Fitness for Service Pipeline
Fitness-for-service assessment is a multi-disciplinary approach to
evaluate structural components to determine if they are fit for
continued service. Pipelines may contain flaws or other damage, or may
be subject to more severe operating conditions than the original design
anticipated. Quest Integrity Group’s LifeQuest pipeline assessment
solution uses API 579-1/ASME FFS-1 fitness-for-service methodology to
deliver an assessment of the pipeline for continued operation at defined
maximum allowable operating pressure. An evaluation of remaining life
and/or inspection intervals may also be part of such an assessment.
The FFS of any particular material is determined by performing a
fitness for service assessment. Performing accurate FFS evaluations is
an integral aspect of fixed equipment asset integrity management.
On the other hand, failing to perform evaluations can lead to equipment
failures which can further result in injury, loss of life, and severe
financial and economic consequences.
The reason these examinations are performed is because even if a
piece of equipment has a crack or other defect, this doesn’t necessarily
mean that it’s unfit for service. Most equipment can continue in
service despite small flaws, and to repair or replace equipment that can
still be used would be an unnecessary and costly expense. Not only
that, but unnecessary weld repairs can actually do more harm than good,
as the quality of the new weld can often be less than the original one.
There are several ways to see if a flaw can cause a piece of
equipment to be no longer fit for service. For cracks, fracture
mechanics provides the mathematical framework for the examination by
quantifying combinations of stress, flaw size, and fracture toughness.
While cracks tend to be the most dangerous, they’re not the only flaw
that might warrant evaluation. Volumetric flaws such as corrosion pits,
porosity, and slag may reduce the load-bearing capacity of a structure.
Likewise, structural integrity may also be compromised by locally
thinned areas which come grinding out cracks, thus FFS methodologies
have been developed to evaluate local thinning. In these cases,
acceptance criteria are based on limit load analyses rather than
fracture mechanics models. Some examples of these different FFS
methodologies are the BS 7910 method, API RP 579-1/ASME FFS-1 method, and the MPC/AP method.
It is important to note though that FFS evaluation can’t provide an
absolute delineation between safe and unsafe operating conditions.
Uncertainties in input parameters such as stress, flaw size, and
toughness often lead to a large uncertainty in the prediction of the
critical conditions for failure. In general there are two ways to
address this uncertainty. The more traditional approach has been to use
conservative input values in a deterministic analysis. The result of
such an analysis is a pessimistic prediction of critical flaw size or
remaining life.
An alternative approach, one which is becoming more common, entails
performing a probabilistic analysis that incorporates the uncertainties
in the input data. The latter type of analysis does not result in an
absolute yes/no answer as to whether or not a structure is safe for
continued operation. Rather, a probabilistic analysis estimates the
relative likelihood of failure, given all of the incorporated
uncertainties. Probabilistic FFS analysis can be an integral part of a risk-based inspection (RBI) protocol, where inspection is prioritized according to the risk of significant injury or economic loss.
Daftar Pustaka :
http://pipelinesinternational.com/news/fitness-for-service_assessment_of_unpiggable_pipelines/53611
https://inspectioneering.com/tag/fitness+for+service
Selasa, 16 Februari 2016
Engineering Critical Assessment for Offshore Pipeline
Engineering Critical Assessment for Offshore Pipeline
Pipeline girth welds often contain “imperfections,” which are alternatively termed “flaws” or “defects.” Traditionally, the tolerable size of those imperfections is set by workmanship-based criteria, such as those in the main body of API Standard 1104. These criteria are empirically-based and historically proven safe in practice. In most cases, they are not quantitatively related to the severity of the defects for the safe operation of the pipelines.
ECA in the context of pipeline girth weld refers to the development of weld imperfection acceptance criteria for the purpose of field girth weld inspection and repair (if needed). The technical basis of ECA is fracture mechanics. When executed correctly, ECA provides a quantifiable level of safety for the project-specific welds and loading conditions. ECA is the preferred method for field girth weld inspection and quality control for long distance pipeline projects.
The stresses affecting the integrity of the girth welds may be broadly divided into alternating stresses and static stresses. The alternating stresses are usually induced by the temperature and pressure fluctuations of the pipelines. The static stresses may come from construction and service conditions.
The primary objective of welding procedure qualification is to establish that welds of certain quality can be reliably produced. These welds should have the necessary properties to meet or exceed the requirements set forth by relevant codes, standards, and/or company specifications.
The initial imperfection criteria are often developed following the requirements and specifications of relevant codes and standards.
Daftar Pustaka :
http://www.cres-americas.com/expertise/engineering-critical-assessment/
Pipeline girth welds often contain “imperfections,” which are alternatively termed “flaws” or “defects.” Traditionally, the tolerable size of those imperfections is set by workmanship-based criteria, such as those in the main body of API Standard 1104. These criteria are empirically-based and historically proven safe in practice. In most cases, they are not quantitatively related to the severity of the defects for the safe operation of the pipelines.
ECA in the context of pipeline girth weld refers to the development of weld imperfection acceptance criteria for the purpose of field girth weld inspection and repair (if needed). The technical basis of ECA is fracture mechanics. When executed correctly, ECA provides a quantifiable level of safety for the project-specific welds and loading conditions. ECA is the preferred method for field girth weld inspection and quality control for long distance pipeline projects.
The stresses affecting the integrity of the girth welds may be broadly divided into alternating stresses and static stresses. The alternating stresses are usually induced by the temperature and pressure fluctuations of the pipelines. The static stresses may come from construction and service conditions.
The primary objective of welding procedure qualification is to establish that welds of certain quality can be reliably produced. These welds should have the necessary properties to meet or exceed the requirements set forth by relevant codes, standards, and/or company specifications.
The initial imperfection criteria are often developed following the requirements and specifications of relevant codes and standards.
Daftar Pustaka :
http://www.cres-americas.com/expertise/engineering-critical-assessment/
Horizontal and Vertical X-mast Tree
Horizontal and Vertical X-mast Tree
Subsea production trees can be segmented into
two main types: horizontal trees and vertical trees. Horizontal trees
are so called because the primary valves are arranged in a horizontal
configuration, and likewise vertical trees have the primary valves
arranged in a vertical configuration.
A
key requirement of a subsea tree is that access is enabled to the “A”
annulus between the production tubing and casing. This is required for a
number of reasons, including pressure monitoring and gas lift. As an
example, any pressure buildup in the A annulus can be bled to the
production flowline via a crossover loop on the tree.
The
original designs of subsea vertical trees and tubing hangers were of a
dual-bore configuration. Prior to removal of the BOP, it is necessary to
set plugs in both the production and annulus bores. Access to both
bores requires the use of a dual-bore riser or landing string. The
handling and operation of dual-bore systems compared to monobore systems
is more complex, and time-consuming and, therefore, more costly.
On
a horizontal tree, access to the A annulus is incorporated into the
tree design and controlled by gate valves rather than plugs. This
enables operations with a mono-bore, less-complex riser or landing
string, which can deliver significant advantages, particularly in deep
water. It is exactly this logic that led to the introduction of
tubing-head spools for use with vertical trees, thereby offering many of
the advantages of a horizontal tree.
Daftar Pustaka :
http://www.epmag.com/drivers-influencing-evolution-horizontal-and-vertical-trees-698041#p=2
Pipeline Elbow and Bend
Pipeline Elbow and Bend
here is always a doubt about the terms bends and elbows on ships. They are frequently used as synonyms. The difference between them is as follows:
Elbows are again classified as long radius or short radius elbows. The difference between them is the length and curvature. A short radius elbow will be giving the piping a sharper turn than a long radius elbow.
In addition to this classification the elbows are 45 degrees, 90 degrees and 180 degrees also called as a return elbow.
- Mitter bend
Another type of bend is a Miter bend. A Miter bend is a bend which is made by cutting pipe ends at an angle and joining the pipe ends. A true miter bend is a 90 degree bend made by cutting two pipes at 45 degrees and joining them by welding. Similarly three pipes cut at 22.5 degrees will give a 90 degree miter bend.
here is always a doubt about the terms bends and elbows on ships. They are frequently used as synonyms. The difference between them is as follows:
- Bend is a generic term for any offset or change of direction in the piping. It is a vague term that also includes elbows.
- An elbow is an engineering term and they are classified as 90 deg or 45 deg, short or long radius.
- Elbows have industrial standards and have limitations to size, bend radius and angle. The angles are usually 45 deg or 90 degrees. All others offsets are classified as pipe bends.
- Bends are generally made or fabricated as per the need of the piping; however elbows are pre fabricated and standard, and are available off the shelf.
- Bends are never sharp corners but elbows are. Pipe bending techniques have constraint as to how much material thinning can be allowed to safely contain the pressure of the fluid to be contained. As elbows are pre fabricated, cast or butt welded, they can be sharp like right angles and return elbows which are 180 degrees.
- Elbow is a standard fitting but bends are custom fabricated.
- In bends as the pipe is bent and there is no welding involved, there is less pipe friction and flow is smoother. In elbows, the welding can create some friction.
- All elbows are bends but all bends are not elbows.
- Bend has a larger radius then elbows.
- Generally the most basic difference is the radius of curvature. Elbows generally have radius of curvature between one to twice the diameter of the pipe. Bends have a radius of curvature more than twice the diameter.
Elbows are again classified as long radius or short radius elbows. The difference between them is the length and curvature. A short radius elbow will be giving the piping a sharper turn than a long radius elbow.
90 degree short radius elbow
Sumber gambar : http://www.piyush-steel.com/img/90-deg-short-redius-buttweld.jpg
- In a long radius elbow the radius of curvature is 1.5 times the nominal diameter. In a standard elbow the radius of curvature is 1.0 times the nominal diameter of the pipe.
- Long radius elbows give less frictional resistance to the fluid than the short elbows.
- Long radius elbows create lesser pressure drop than short radius elbows.
- Short radius is less costly than long radius elbows.
- The short radius elbows are used where there is scarcity of space.
In addition to this classification the elbows are 45 degrees, 90 degrees and 180 degrees also called as a return elbow.
- Mitter bend
Another type of bend is a Miter bend. A Miter bend is a bend which is made by cutting pipe ends at an angle and joining the pipe ends. A true miter bend is a 90 degree bend made by cutting two pipes at 45 degrees and joining them by welding. Similarly three pipes cut at 22.5 degrees will give a 90 degree miter bend.
Mitter bend.
Sumber gambar : http://www.vessel-software.nl/pcc/doc/calculations/asme_b31_3/images/asme_b31_3_miterbend.png
Daftar Pustaka :
http://www.marineinsight.com/tech/pipeing/pipes-and-bends-an-essential-guide-for-second-engineers-part-2/
Pipeline Stress Analysis
Pipeline Stress Analysis
The analysis of piping under pressure, weight and thermal expansion is
complex. This complexity can be understood by knovledge of Principal
Axis System.
Stress is considered as the ratio of Force to Area. To find the stress
in the small element, say cube of a piece of pipe, construct a
three-dimensional, mutually perpendicular principal axis system with
each axis perpendicular to the face of the cube it intersects.
Each force, acting on the cube can be resolved into force components,
acting along each of the axis. Each force, acting on the face of the
cube divided by area of the cube face is called the principal stress.
The principal stress acting along the centerline of the pipe is called
Longitudinal principal stress. This stress is caused by longitudinal
bending, axial force loading or pressure.
Radial principal stress acts on a line from a radial line from center of
pipe through the pipe wall. This stress is compressive stress acting on
pipe inside diameter caused by internal pressure or a tensile stress
caused by vacuum pressure.
Circumferential principal stress, some times called Hoop or tangential
stress, acts along the circumference of the pipe. This stress tends to
open-up the pipe wall and is caused by internal pressure.
When two or more principal stresses act at a point on a pipe, a shear stress will be generated.
Longitudinal Principal stress, LPS = PD/4T
Circumferential Principal stress, CPS (Hoop) = PD/2T
Radial Principal stress, RPS = P
Daftar Pustaka :
http://www.pipingguide.net/2010/10/stress-analysis-of-piping.html
Vortex Induced Vibration on Pipeline
Vortex Induced Vibration on Pipeline
Vortex-induced vibration is a major cause of fatigue failure in submarine oil and gas pipelines and steel catenary risers. One of the serious problems for the structural safety of pipelines is uneven areas in the seafloor as they enhance the formation of free spans. Route selection, therefore, plays an important part in design, Matteelli (1982). However, due to many obstacles it is difficult to find a totally obstruction free route. In such cases the pipeline may have free spans when crossing depressions. Hence, if dynamic loads can occur, the free span may oscillate and time varying stresses may give unacceptable fatigue damage. A major source for dynamic stresses in free span pipelines is vortex induced vibrations (VIV) caused by steady current. This effect is in fact dominating on deep water pipelines since wave induced velocities and accelerations will decay with increasing water depth. The challenge for the industry is then to verify that such spans can sustain the influence from the environment throughout the lifetime of the pipeline.
The aim of the present project is to improve the understanding of vortex induced vibrations (VIV) of free span pipelines, and thereby improve methods, existing computer programs and guidelines needed for design verification. This will result in more cost effective and reliable offshore pipelines when laid on a very rugged seafloor.To evaluate two different strategies for field development; one based on offshore loading and the other on a pipeline to an onshore gas terminal. A key problem for the last alternative is that the seafloor between these fields and the coast is extremely rugged meaning that a pipeline must have more and longer free spans than what is seen for conventional pipelines.
Practical engineering is still based on empirical models, while use of computational fluid dynamics (CFD) is considered immature mainly because of the needed computing resources. CFD models may certainly be linked to a non-linear structural model, but the needed computing time will become overwhelming. Then, one of the main focuses of the present research is investigation about time domain model for analysis of vortex induced vibrations for free span pipelines and the other is about multi free span pipelines where neighbor spans may interact dynamically. The interaction will depend on the length and stiffness of the pipe resting on the sea floor between the spans, and sea floor parameters such as stiffness, damping and friction. Each of them has important issues to investigate for improvement of our VIV knowledge.
Daftar Pustaka :
http://www.diva-portal.org/smash/get/diva2:217873/FULLTEXT01.pdf
Vortex-induced vibration is a major cause of fatigue failure in submarine oil and gas pipelines and steel catenary risers. One of the serious problems for the structural safety of pipelines is uneven areas in the seafloor as they enhance the formation of free spans. Route selection, therefore, plays an important part in design, Matteelli (1982). However, due to many obstacles it is difficult to find a totally obstruction free route. In such cases the pipeline may have free spans when crossing depressions. Hence, if dynamic loads can occur, the free span may oscillate and time varying stresses may give unacceptable fatigue damage. A major source for dynamic stresses in free span pipelines is vortex induced vibrations (VIV) caused by steady current. This effect is in fact dominating on deep water pipelines since wave induced velocities and accelerations will decay with increasing water depth. The challenge for the industry is then to verify that such spans can sustain the influence from the environment throughout the lifetime of the pipeline.
The aim of the present project is to improve the understanding of vortex induced vibrations (VIV) of free span pipelines, and thereby improve methods, existing computer programs and guidelines needed for design verification. This will result in more cost effective and reliable offshore pipelines when laid on a very rugged seafloor.To evaluate two different strategies for field development; one based on offshore loading and the other on a pipeline to an onshore gas terminal. A key problem for the last alternative is that the seafloor between these fields and the coast is extremely rugged meaning that a pipeline must have more and longer free spans than what is seen for conventional pipelines.
Practical engineering is still based on empirical models, while use of computational fluid dynamics (CFD) is considered immature mainly because of the needed computing resources. CFD models may certainly be linked to a non-linear structural model, but the needed computing time will become overwhelming. Then, one of the main focuses of the present research is investigation about time domain model for analysis of vortex induced vibrations for free span pipelines and the other is about multi free span pipelines where neighbor spans may interact dynamically. The interaction will depend on the length and stiffness of the pipe resting on the sea floor between the spans, and sea floor parameters such as stiffness, damping and friction. Each of them has important issues to investigate for improvement of our VIV knowledge.
Daftar Pustaka :
http://www.diva-portal.org/smash/get/diva2:217873/FULLTEXT01.pdf
Horizontal Directional Drilling
Horizontal Directional Drilling
Directional boring, commonly called horizontal directional drilling or HDD, is a steerable trenchless method of installing underground pipe, conduit, or cable in a shallow arc along a prescribed bore path by using a surface-launched drilling rig, with minimal impact on the surrounding area. Directional boring is used when trenching or excavating is not practical. It is suitable for a variety of soil conditions and jobs including road, landscape and river crossings. Installation lengths up to 2000 m have been completed, and diameters up to 1200 mm have been installed in shorter runs. Pipe can be made of materials such as PVC, polyethylene, polypropylene, Ductile iron, and steel as long as it can be pulled through the drilled hole. Directional boring is not practical if there are voids in the rock or incomplete layers of rock. The best material is solid rock or sedimentary material. Soils with cobble stone are not recommended. There are different types of heads used in the pilot-hole process, and they depend on the geological material.
Horizontal directional drilling (HDD) was pioneered in the United States in the early 1970s by an innovative road boring contractor who successfully completed a 183 m (600 ft) river crossing using a modified rod pushing tool with no steering capability (DCCA 1994). By integrating existing technology from the oil well drilling industry and modern surveying and steering techniques, today's directional drilling methods have become the preferred approach for installing utility lines, ranging from large-size pipeline river crossings to small-diameter cable conduits.
Directional boring, commonly called horizontal directional drilling or HDD, is a steerable trenchless method of installing underground pipe, conduit, or cable in a shallow arc along a prescribed bore path by using a surface-launched drilling rig, with minimal impact on the surrounding area. Directional boring is used when trenching or excavating is not practical. It is suitable for a variety of soil conditions and jobs including road, landscape and river crossings. Installation lengths up to 2000 m have been completed, and diameters up to 1200 mm have been installed in shorter runs. Pipe can be made of materials such as PVC, polyethylene, polypropylene, Ductile iron, and steel as long as it can be pulled through the drilled hole. Directional boring is not practical if there are voids in the rock or incomplete layers of rock. The best material is solid rock or sedimentary material. Soils with cobble stone are not recommended. There are different types of heads used in the pilot-hole process, and they depend on the geological material.
Horizontal directional drilling (HDD) was pioneered in the United States in the early 1970s by an innovative road boring contractor who successfully completed a 183 m (600 ft) river crossing using a modified rod pushing tool with no steering capability (DCCA 1994). By integrating existing technology from the oil well drilling industry and modern surveying and steering techniques, today's directional drilling methods have become the preferred approach for installing utility lines, ranging from large-size pipeline river crossings to small-diameter cable conduits.
The HDD industry is divided into three major
sectors--large-diameter HDD (maxi-HDD), medium-diameter HDD (midi-HDD), and small-diameter
HDD (mini-HDD, also called guided boring)--according to their typical
application areas. Although there is no significant difference in the operation
mechanisms among these systems, the different application ranges often require
corresponding modification to the system configuration and capacities, mode of
spoil removal, and directional control methods to achieve optimal
cost-efficiency. Table 1 compares typical maxi-, midi-, and mini-HDD systems.
Table 1. Comparison of main features of
typical maxi-, midi-, and mini-HDD (Iseley and Gokhale 1997)
| System Description | Product Pipe Diameter | Depth Range | Drive Length | Torque | Thrust/ Pullback | Machine Weight (including truck) | Typical Application |
| Maxi-HDD |
600-1,200
mm
(24-48
in)
|
< 61 m (200 ft) |
< 1,818 m
(6,000
ft)
|
< 108.5 kN-m
(80,000
ft-lb)
|
< 445 kN
(100,000
lb)
|
< 267 kN
(30
ton)
|
River, Highway crossings |
| Midi-HDD |
300-600
mm
(12-24
in)
|
< 23 m (75 ft) |
< 274 m
(900
ft)
|
1-9.5
kN-m
(900-7,000
ft-lb)
|
89-445
kN
(20,000-100,000
lb)
|
< 160 kN
(18
ton)
|
Under
rivers and roadways
|
| Mini-HDD |
50-300
mm
(2-12
in)
|
< 4.5 m (15 ft) |
< 182 m
(600
ft)
|
< 1.3 kN-m
(950
ft-lb)
|
< 89 kN
(20,000
lb)
|
< 80 kN
(9
ton)
|
Telecom
and Power cables,
|
Daftar Pustaka :
https://en.wikipedia.org/wiki/Directional_boring
http://rebar.ecn.purdue.edu/Trenchless/secondpage/Content/HDD.htm
HDPE Pipe
HDPE Pipe
High Density Polyethylene (HDPE) has been selected for the primary pipe material. HDPE has several advantages over FRP and concrete pipes for this marine pipeline :
- Readily Available Commercial Product
- High Flexibility/ Strain Capability
- High Strength/Rugged
- Strong Fusion Joints
- Corrosion/UV/Biofouling Resistant
- Excellent Hydraulic Characteristics
- Low Cost
HDPE's unique characteristics of high flexibility, high strength. high strain capability, strong fusion joints, no corrosion, and bouyancy provide for fast and low-cost deployment using the controlled submergence deployment method. HDPE pipe is also a favorite for HDD installation, as its strength and flexibility make it highly suitable for installation in tunnel boring.
Daftar Pustaka :
http://www.deepwaterdesal.com/userfiles/file/Appendix_D-_Makai-DWD_-_Final_Report_-_May29_-_revB.pdf
Daftar Pustaka :
http://www.deepwaterdesal.com/userfiles/file/Appendix_D-_Makai-DWD_-_Final_Report_-_May29_-_revB.pdf
Minggu, 14 Februari 2016
Above Water Tie In
Above Water Tie In
Midline Tie-in or Above Water Tie-in (AWTI) is an operation where two laid down pipelines on the seabed are welded together after being lifted above water using vessel davits. For AWTI we determine/provide:
Static Code checks (pipeline integrity) are performed for
every static loadcase. Dynamic Analysis is performed for the respective
worst case in Pipe Recovery, Welded configuration and Laydown. DNV
buckle checks are used to ascertain pipe integrity during dynamics.
Daftar Pustaka :
http://www.oesl.nl/expertise/pipelay
Midline Tie-in or Above Water Tie-in (AWTI) is an operation where two laid down pipelines on the seabed are welded together after being lifted above water using vessel davits. For AWTI we determine/provide:
- Steps for recovering the pipelines
- Welded Configuration for recovered pipes
- Steps for lowering the completed pipeline
- Weld excavation analysis
- Minimum weld thickness assessment for removal of the welding clamp
- Offshore Procedures to be followed during execution
Above water tie in.
Sumber gambar : https://vladvamphire.files.wordpress.com/2009/06/5.jpg
Daftar Pustaka :
http://www.oesl.nl/expertise/pipelay
Sabtu, 13 Februari 2016
Pipeline inspection
Pipeline Inspection
Because of growing oil and gas pipeline regulations, operators are
implementing thorough integrity programs that ensure leaks and failures
do not occur.
Integrity programs that combine structural condition assessment with
regular and accurate verification of containment surveys significantly
reduce the risk of failure while extending the useful life of
thepipeline asset.
By utilizing verification from containment tools that identify very
small losses, oil and gas pipeline operators can identify and repair
problems at an early stage in their development. This is important as
small pipeline leaks can eventually lead to failure.
Through a diverse and comprehensive integrity program, oil and gas operators can reduce the risk of pipe failure.Daftar Pustaka :
https://www.puretechltd.com/markets/oil-and-gas
Flexible riser
Flexible riser
A Flexible Riser is a flexible pipe that transfers materials from the seafloor to the drilling and production facilities and from the facilities to the seafloor as well. It is a hybrid that is capable of accommodating a wide number of different situations that withstand both horizontal and vertical movement; hence it is ideal for use with floating facilities. Flexible Risers were originally used to connect the production equipment embarked on a floating facility to export and produce risers.
There are a variety of configurations for the Flexible Risers which includes lazy S and steep S that use anchored buoyancy modules. They also use lazy wave and steep wave which incorporate buoyancy modules.
Flexible Risers are flexible pipes that have been a successful solution for shallow and deep flowline systems worldwide. These are the subsea risers that are developed to carry out this type of vertical transportation. They serve as import or export and production vehicles connected between the drilling and production facilities and the subsea field development. Like pipelines, the risers also transport the produced hydrocarbons, control fluids, injection fluids and gas lift.
They are the enabling technologies used for floating production in harsh environmental conditions. They encompass a layered structure with various materials having different functions like withstanding internal and external pressure, preventing leaks of hydrocarbons, coping with tensile forces and protection against the seawater.
A Flexible Riser is a flexible pipe that transfers materials from the seafloor to the drilling and production facilities and from the facilities to the seafloor as well. It is a hybrid that is capable of accommodating a wide number of different situations that withstand both horizontal and vertical movement; hence it is ideal for use with floating facilities. Flexible Risers were originally used to connect the production equipment embarked on a floating facility to export and produce risers.
There are a variety of configurations for the Flexible Risers which includes lazy S and steep S that use anchored buoyancy modules. They also use lazy wave and steep wave which incorporate buoyancy modules.
Flexible Risers are flexible pipes that have been a successful solution for shallow and deep flowline systems worldwide. These are the subsea risers that are developed to carry out this type of vertical transportation. They serve as import or export and production vehicles connected between the drilling and production facilities and the subsea field development. Like pipelines, the risers also transport the produced hydrocarbons, control fluids, injection fluids and gas lift.
They are the enabling technologies used for floating production in harsh environmental conditions. They encompass a layered structure with various materials having different functions like withstanding internal and external pressure, preventing leaks of hydrocarbons, coping with tensile forces and protection against the seawater.
Flexible Riser
Sumber gambar : http://www.offshorerisertechnology.com/uploads/8/7/0/7/8707355/576920_orig.jpg
Daftar Pustaka :
https://www.petropedia.com/definition/7230/flexible-riser
Pipeline On Bottom Stability
Pipeline On Bottom Stability
On bottom stability analysis is performed to ensure the stability of the pipeline when exposed to wave and current forces and other internal or external loads. The requirement to the pipeline is that no lateral movements at all are accepted, or alternatively that certain limited movements that do not cause interference with adjacent objects or overstressing of the pipe are allowed.
Hydrodynamic stability is generally obtained by increasing the submerged weight of the pipe by concrete coating. There are other ways such as increasing the steel wall thickness, placing concrete blankets or bitumen mattresses across the pipeline, anchoring or covering it with gravel or rock. Alternatively, the hydrodynamic forces may be reduced by placing the pipeline in a trench on the seabed, prior or subsequent to installation. The natural backfilling of a pipeline depends on the environmental conditions and the seabed sediment at the location.
A pipeline on the seabed forms a structural unit where displacement in one area is resisted by bending and tensile stresses. The real situation most probably involves a great variety of pipeline-seabed interface conditions. Pipeline self lowering may result in some sections of a pipeline being embedded to a larger degree than determined by soil characteristics and phenomena such as scour, sediment transport and other seabed instabilities. In other sections the pipe may be slightly elevated above the seabed due to seabed undulation or scour processes. For both conditions, the hydrodynamuc forces are reduced relative to the idealized on bottom condition.
Daftar Pustaka :
http://www.efka.utm.my/thesis/IMAGES/3PSM/2007/JSB/PARTS5/mohdridzaba030064d07ttt.pdf
On bottom stability analysis is performed to ensure the stability of the pipeline when exposed to wave and current forces and other internal or external loads. The requirement to the pipeline is that no lateral movements at all are accepted, or alternatively that certain limited movements that do not cause interference with adjacent objects or overstressing of the pipe are allowed.
Hydrodynamic stability is generally obtained by increasing the submerged weight of the pipe by concrete coating. There are other ways such as increasing the steel wall thickness, placing concrete blankets or bitumen mattresses across the pipeline, anchoring or covering it with gravel or rock. Alternatively, the hydrodynamic forces may be reduced by placing the pipeline in a trench on the seabed, prior or subsequent to installation. The natural backfilling of a pipeline depends on the environmental conditions and the seabed sediment at the location.
A pipeline on the seabed forms a structural unit where displacement in one area is resisted by bending and tensile stresses. The real situation most probably involves a great variety of pipeline-seabed interface conditions. Pipeline self lowering may result in some sections of a pipeline being embedded to a larger degree than determined by soil characteristics and phenomena such as scour, sediment transport and other seabed instabilities. In other sections the pipe may be slightly elevated above the seabed due to seabed undulation or scour processes. For both conditions, the hydrodynamuc forces are reduced relative to the idealized on bottom condition.
Daftar Pustaka :
http://www.efka.utm.my/thesis/IMAGES/3PSM/2007/JSB/PARTS5/mohdridzaba030064d07ttt.pdf
Pipeline Material and Grade Selection
Pipeline Material
With the recent spate of material failures in the oil and gas industry around the world, the role of a material and corrosion engineer in selecting suitable material has become more complex, controversial and difficult. Further, the task had become more diverse, since now modern engineering materials offer a wide spectrum of attractive properties and viable benefits.
From the earlier years or late ’70s, the process of materials selection that had been confined exclusively to a material engineer, a metallurgist or a corrosion specialist has widened today to encompass other disciplines like process, operations, integrity, etc. Material selection is no more under a single umbrella but has become an integrated team effort and a multidisciplinary approach. The material or corrosion specialist in today’s environment has to play the role of negotiator or mediator between the conflicting interests of other peer disciplines like process, operations, concept, finance, budgeting, etc.
With this as backdrop, this article presents various stages in the material selection process and offers a rational path for the selection process toward a distinctive, focused and structured holistic approach.
What is material selection in oil and gas industry? Material selection in the oil and gas industry – by and large – is the process of short listing technically suitable material options and materials for an intended application. Further to these options, it is the process of selecting the most cost- effective material option for the specified operating life of the asset, bearing in mind the health, safety and environmental aspects and sustainable development of the asset, technical integrity and any asset operational constraints envisaged in the operating life of the asset.
Concept Stage
Material selection during the concept stage basically means the investigative approach for the various available material options for the intended function and application. In this stage, a key factor for the material selection is an up-front activity taking into consideration operational flexibility, cost, availability or sourcing and, finally, the performance of the material for the intended service and application.
The material and corrosion engineer’s specialized expertise or skills become more important as the application becomes critical, such as highly sour conditions, highly corrosive and aggressive fluids, high temperatures and highly stressed environments, etc.
It is imperative at this concept stage that the material selection process becomes an interdisciplinary team approach rather an individualistic material and corrosion engineer’s choice. However, some level of material selection must be made in order to proceed with the detailed design activities or engineering phase.
The number and availability of material options in today’s industry have grown tremendously and have made the selection process more intricate than a few decades back. The trend with research and development in the materials sciences will continue to grow and may make the selection even more complex and intriguing.
It should be understood that, at the concept design stage, the selection is broad and wide. This stage defines the options available for specific application with the available family of materials like metals, non metals, composites, plastics, etc. If an innovative and cost-effective material choice is to be made from an available family of options, it is normally done at this stage.
At times, material constraints from the client or operating company or the end user may dictate the material selections as part of a contractual obligation. Sourcing, financial and cost constraints at times may also limit and obstruct the material selections except for vey critical applications where the properties and technical acceptability of the material is more assertive and outweighs the cost of the material.
Materials availability is another important criterion on the material selection which impacts the demanding project schedules for the technically suitable material options. Also, different engineering disciplines may have different and specific requirements like constructability, maintainability, etc. However, a compromise shall be reached at this stage among all the disciplines concerned to arrive at a viable economic compromise on the candidate material.
Detailed Engineering Stage
Materials selection during the detailed design stage becomes more focused and specific. The material selection process narrows down to a small group or family of materials, say: carbon steels, stainless steels, duplex stainless steels, Inconels or Incoloys, etc. In the detail design stage, it narrows down to a single material and other conditions of supply like Austenitic stainless steels, Martensitic stainless steels, cast materials, forged materials, etc.
Depending on the criticality of the application at this stage the material properties, manufacturing processes and quality requirements will be addressed to more precise levels and details. This may sometimes involve extensive material-testing programs for corrosion, high temperature, and simulated heat treatment as well as proof testing.
From the concept to detailing stage is a progressive process ranging from larger broad possibilities to screening to a specific material and supply condition.
At times, the selection activity may involve a totally new project (greenfield) or to an extension of existing project (brownfield). In the case of an existing project, it could be necessary to check and evaluate the adequacy of the current materials; it may be necessary at times to select a material with enhanced properties. The candidate material shall normally be investigated for more details in terms of cost, performance, fabricability, availability and any requirements of additional testing in the detail engineering stage.
Failure Prevention (Lessons Learned)
Material selection and the sustainability of material to prevent any failure during the life of the component is the final selection criterion in the process.
Failure is defined as an event where the material or the component did not accomplish the intended function or application. In most cases, the material failure is attributed to the selection of the wrong material for the particular application. Hence, the review and analysis of the failure is a very important aspect in the material selection process to avert any similar failures of the material in future.
The failure analysis – or the lessons learned – may not always result in better material. The analysis may, at times, study and consider the steps to reduce the impact on the factors that caused the failure. A typical example would be to introduce a chemical inhibition system into the process to mitigate corrosion of the material or to carry out a post-weld heat treatment to minimize the residual stresses in the material which has led to stress corrosion cracking failure.
An exhaustive review and study of the existing material that failed, including inadequacy checks and a review of quality levels imposed on the failed materials, is required before an alternate and different material is selected for the application.
The importance of the failure analysis cannot be overstressed in view of the spate of failures in recent times in the oil and gas industry. The results of failure analysis and study will provide valuable information to guide the material selection process and can serve as input for the recommendation in the concept and design stages of the project. It strengthens and reinforces the material selection process with sound back-up information.
Let us take a general view of material recommendations for pipelines. Some of the materials most relevant for use in pipelines in the Middle East are indicated for information and guidance in Table 1. The recommendations are general in nature and each pipeline is to be studied in detail case by case as regards operating conditions, fluid compositions, etc. before any final selections.
Also, other considerations – like the total length of the pipeline, above or below ground installation, nature of the pipeline (export line or processing line, etc.) – that are to be taken into consideration during the detailed engineering phase.
Materials:
Material Selection Process:
Material Options
Metals:
Advantages & Disadvantages of Material Options
With the recent spate of material failures in the oil and gas industry around the world, the role of a material and corrosion engineer in selecting suitable material has become more complex, controversial and difficult. Further, the task had become more diverse, since now modern engineering materials offer a wide spectrum of attractive properties and viable benefits.
From the earlier years or late ’70s, the process of materials selection that had been confined exclusively to a material engineer, a metallurgist or a corrosion specialist has widened today to encompass other disciplines like process, operations, integrity, etc. Material selection is no more under a single umbrella but has become an integrated team effort and a multidisciplinary approach. The material or corrosion specialist in today’s environment has to play the role of negotiator or mediator between the conflicting interests of other peer disciplines like process, operations, concept, finance, budgeting, etc.
With this as backdrop, this article presents various stages in the material selection process and offers a rational path for the selection process toward a distinctive, focused and structured holistic approach.
What is material selection in oil and gas industry? Material selection in the oil and gas industry – by and large – is the process of short listing technically suitable material options and materials for an intended application. Further to these options, it is the process of selecting the most cost- effective material option for the specified operating life of the asset, bearing in mind the health, safety and environmental aspects and sustainable development of the asset, technical integrity and any asset operational constraints envisaged in the operating life of the asset.
Concept Stage
Material selection during the concept stage basically means the investigative approach for the various available material options for the intended function and application. In this stage, a key factor for the material selection is an up-front activity taking into consideration operational flexibility, cost, availability or sourcing and, finally, the performance of the material for the intended service and application.
The material and corrosion engineer’s specialized expertise or skills become more important as the application becomes critical, such as highly sour conditions, highly corrosive and aggressive fluids, high temperatures and highly stressed environments, etc.
It is imperative at this concept stage that the material selection process becomes an interdisciplinary team approach rather an individualistic material and corrosion engineer’s choice. However, some level of material selection must be made in order to proceed with the detailed design activities or engineering phase.
The number and availability of material options in today’s industry have grown tremendously and have made the selection process more intricate than a few decades back. The trend with research and development in the materials sciences will continue to grow and may make the selection even more complex and intriguing.
It should be understood that, at the concept design stage, the selection is broad and wide. This stage defines the options available for specific application with the available family of materials like metals, non metals, composites, plastics, etc. If an innovative and cost-effective material choice is to be made from an available family of options, it is normally done at this stage.
At times, material constraints from the client or operating company or the end user may dictate the material selections as part of a contractual obligation. Sourcing, financial and cost constraints at times may also limit and obstruct the material selections except for vey critical applications where the properties and technical acceptability of the material is more assertive and outweighs the cost of the material.
Materials availability is another important criterion on the material selection which impacts the demanding project schedules for the technically suitable material options. Also, different engineering disciplines may have different and specific requirements like constructability, maintainability, etc. However, a compromise shall be reached at this stage among all the disciplines concerned to arrive at a viable economic compromise on the candidate material.
Detailed Engineering Stage
Materials selection during the detailed design stage becomes more focused and specific. The material selection process narrows down to a small group or family of materials, say: carbon steels, stainless steels, duplex stainless steels, Inconels or Incoloys, etc. In the detail design stage, it narrows down to a single material and other conditions of supply like Austenitic stainless steels, Martensitic stainless steels, cast materials, forged materials, etc.
Depending on the criticality of the application at this stage the material properties, manufacturing processes and quality requirements will be addressed to more precise levels and details. This may sometimes involve extensive material-testing programs for corrosion, high temperature, and simulated heat treatment as well as proof testing.
From the concept to detailing stage is a progressive process ranging from larger broad possibilities to screening to a specific material and supply condition.
At times, the selection activity may involve a totally new project (greenfield) or to an extension of existing project (brownfield). In the case of an existing project, it could be necessary to check and evaluate the adequacy of the current materials; it may be necessary at times to select a material with enhanced properties. The candidate material shall normally be investigated for more details in terms of cost, performance, fabricability, availability and any requirements of additional testing in the detail engineering stage.
Failure Prevention (Lessons Learned)
Material selection and the sustainability of material to prevent any failure during the life of the component is the final selection criterion in the process.
Failure is defined as an event where the material or the component did not accomplish the intended function or application. In most cases, the material failure is attributed to the selection of the wrong material for the particular application. Hence, the review and analysis of the failure is a very important aspect in the material selection process to avert any similar failures of the material in future.
The failure analysis – or the lessons learned – may not always result in better material. The analysis may, at times, study and consider the steps to reduce the impact on the factors that caused the failure. A typical example would be to introduce a chemical inhibition system into the process to mitigate corrosion of the material or to carry out a post-weld heat treatment to minimize the residual stresses in the material which has led to stress corrosion cracking failure.
An exhaustive review and study of the existing material that failed, including inadequacy checks and a review of quality levels imposed on the failed materials, is required before an alternate and different material is selected for the application.
The importance of the failure analysis cannot be overstressed in view of the spate of failures in recent times in the oil and gas industry. The results of failure analysis and study will provide valuable information to guide the material selection process and can serve as input for the recommendation in the concept and design stages of the project. It strengthens and reinforces the material selection process with sound back-up information.
Let us take a general view of material recommendations for pipelines. Some of the materials most relevant for use in pipelines in the Middle East are indicated for information and guidance in Table 1. The recommendations are general in nature and each pipeline is to be studied in detail case by case as regards operating conditions, fluid compositions, etc. before any final selections.
Also, other considerations – like the total length of the pipeline, above or below ground installation, nature of the pipeline (export line or processing line, etc.) – that are to be taken into consideration during the detailed engineering phase.
Materials:
- API 5L – Specification for line pipe
- API 5LC – Specification for CRA line pipe
- API 5LD – Specification for CRA clad or Lined pipe
- API 5LE – Specification for Polyethylene line pipe
- ISO 3183 – Petroleum & Natural gas industries – Steel Pipe
- ISO 14692 – Petroleum and Natural gas industries – Glass Reinforced plastic piping
- AWWA M – 45 Fibre glass pipe design
Material Selection Process:
- Identify corrosion threats
- Define the corrosion circuits
- Calculate the corrosion rate per year
- Calculate the Service Life Corrosion (SLC) based on design life
- Consider the materials options
- Carry out the Life Cycle Costing (LCC) – Capex / Opex / Install
- Review the materials selection w.r.t design / operating / constructability
- Finally select the choice materials
Material Options
Metals:
- CS with corrosion allowance
- Stainless Steel
- Duplex Stainless Steel
- Super Duplex Stainless Steel
- CS with internally coated FBE
- CS with internal PE lining
- CRA clad / lined materials
- Glass Reinforced Epoxy (GRE)
- Polyethylene (HDPE)
Advantages & Disadvantages of Material Options
Gambar. Advantage and disadvantage material options.
Sumber gambar : http://www.whatispiping.com/wp-content/uploads/2015/01/Advantages-and-Disadvantages-of-materials.jpg
Daftar Pustaka :
http://pgjonline.com/2011/12/27/a-rational-approach-to-pipeline-material-selection/
http://www.whatispiping.com/pipelines-material
Sabtu, 06 Februari 2016
Pipeline Integrity Management
Pipeline Integrity Management
Growing safety and environmental concerns regarding pipeline management have led to new regulations and stricter requirements for pipeline operators to demonstrate and document their facility’s safe operations.
Pipeline operators are expected to treat pipeline safety and integrity as a social accountability issue while facilitating access to data and ensuring transparency. They are required to demonstrate and document the integrity of their pipeline facilities at all times as well as assess and mitigate risk factors.
Comprehensive integrated Pipeline Integrity Management (PIM) system which is a quality management system encompassing :
- Operation
- Inspection
- Maintenance
- Health, Safety & Environment (HSE)
- Corporate communication
The aim of a PIM System is to set up a concise methodology which applies the same process to all pipeline, enabling homogenous decision making
Benefit of PIM System :
a PIM system can vastly improve the safety of pipeline by :
- Taking into account results from previous years in order to compare, analyze and update data.
- Allowing operators to reflect on their best practices, remaining compliant with the latest regulations and adopting the most appropriate standar
- Identifying and analyzing actual and potential threats, ensuring data integrity
Daftar Pustaka :
http://www.bureauveritas.com/services+sheet/pipeline-integrity-management_941
Growing safety and environmental concerns regarding pipeline management have led to new regulations and stricter requirements for pipeline operators to demonstrate and document their facility’s safe operations.
Pipeline operators are expected to treat pipeline safety and integrity as a social accountability issue while facilitating access to data and ensuring transparency. They are required to demonstrate and document the integrity of their pipeline facilities at all times as well as assess and mitigate risk factors.
Comprehensive integrated Pipeline Integrity Management (PIM) system which is a quality management system encompassing :
- Operation
- Inspection
- Maintenance
- Health, Safety & Environment (HSE)
- Corporate communication
The aim of a PIM System is to set up a concise methodology which applies the same process to all pipeline, enabling homogenous decision making
Benefit of PIM System :
a PIM system can vastly improve the safety of pipeline by :
- Taking into account results from previous years in order to compare, analyze and update data.
- Allowing operators to reflect on their best practices, remaining compliant with the latest regulations and adopting the most appropriate standar
- Identifying and analyzing actual and potential threats, ensuring data integrity
Daftar Pustaka :
http://www.bureauveritas.com/services+sheet/pipeline-integrity-management_941
Pipe In Pipe
Pipe in pipe
A pipe in pipe (PIP) is a pipe inserted inside another pipe.Over the past two decades, the pipe-in-pipe (PiP) product has become an essential part of the subsea field development engineer's "tool box". Due to its high insulation performance it minimizes heat losses from the transported fluid to the environment that more traditional subsea coatings cannot provide. This is achieved using thermal insulation of very low thermal conductivity, such as aerogel, encased in dry atmospheric conditions between the inner pipe or "flowline," which transports the fluid, and the outer pipe or "carrier," which provides the mechanical protection from the subsea environment.
Other benefits of the PiP solution include compatibility with high temperatures (in terms of material and enhanced compliance with large axial loading), stability on the seabed, and protection by the outer pipe against external loads. In some cases this may obviate the need for burial.
Pipe-in-Pipe are suited for shallow, deep and ultra deep water as well as HP/HT fields.
1. Pipe-in-pipe for shallow and deep water applications
Pip system are particularly well suited for shallow, deep and ultra deep offshore projects:
- The pipe in pipe structure accommodates large hydrostatic pressure.
- Due to the low thermal conductivity of IzoflexTM, only a thin layer of insulation is required to obtain highly insulated systems, which reduces the outer pipe size and thickness, thus reducing weight and costs (less welding time, less steel).
- The compact & efficient insulation allows long tiebacks and long cooldown time.
- For J-lay & S-lay, the specific ITP Field Joint (FJ) allows a quick offshore installation (one single weld offshore).
- The ITP single/double/quad joint design offer integrated water stop and buckle arrestor every 12/24/48 metres.
2. High Pressure/ High Temperature
Daftar pustaka :
http://www.offshore-mag.com/articles/print/volume-75/issue-2/pipelines-flowlines/pipe-in-pipe-technology-adapts-to-changing-needs-in-deep-and-shallow-water.html
http://www.itp-interpipe.com/products/pipe-in-pipes/pipe-in-pipes.php
http://www.itp-interpipe.com/
A pipe in pipe (PIP) is a pipe inserted inside another pipe.Over the past two decades, the pipe-in-pipe (PiP) product has become an essential part of the subsea field development engineer's "tool box". Due to its high insulation performance it minimizes heat losses from the transported fluid to the environment that more traditional subsea coatings cannot provide. This is achieved using thermal insulation of very low thermal conductivity, such as aerogel, encased in dry atmospheric conditions between the inner pipe or "flowline," which transports the fluid, and the outer pipe or "carrier," which provides the mechanical protection from the subsea environment.
Other benefits of the PiP solution include compatibility with high temperatures (in terms of material and enhanced compliance with large axial loading), stability on the seabed, and protection by the outer pipe against external loads. In some cases this may obviate the need for burial.
Pipe in pipe.
Source : http://www.itp-interpipe.com/images/pipe-in-pipes/pipe-in-pipes.jpg
Pipe-in-Pipe are suited for shallow, deep and ultra deep water as well as HP/HT fields.
1. Pipe-in-pipe for shallow and deep water applications
Pip system are particularly well suited for shallow, deep and ultra deep offshore projects:
- The pipe in pipe structure accommodates large hydrostatic pressure.
- Due to the low thermal conductivity of IzoflexTM, only a thin layer of insulation is required to obtain highly insulated systems, which reduces the outer pipe size and thickness, thus reducing weight and costs (less welding time, less steel).
- The compact & efficient insulation allows long tiebacks and long cooldown time.
- For J-lay & S-lay, the specific ITP Field Joint (FJ) allows a quick offshore installation (one single weld offshore).
- The ITP single/double/quad joint design offer integrated water stop and buckle arrestor every 12/24/48 metres.
2. High Pressure/ High Temperature
Daftar pustaka :
http://www.offshore-mag.com/articles/print/volume-75/issue-2/pipelines-flowlines/pipe-in-pipe-technology-adapts-to-changing-needs-in-deep-and-shallow-water.html
http://www.itp-interpipe.com/products/pipe-in-pipes/pipe-in-pipes.php
http://www.itp-interpipe.com/
Flow assurance for offshore pipeline
Flow assurance for offshore pipeline
Flow assurance is relatively new term in oil and gas industry. It refers to ensuring successful and economical flow of hydrocarbon stream from reservoir to the point of sale and is closely linked to multiphase flow technology.
Flow assurance developed because traditional approaches are inappropriate for deepwater production due to extreme distances, depths, temperatures or economic constraints. The term Flow Assurance was first used by Petrobras in the early 1990s in Portuguese as Garantia do Escoamento (pt::Garantia do Escoamento), meaning literally "Guarantee of Flow", or Flow Assurance.
Flow assurance by definiton focuses on the whole engineering and production life cycle from the reservoir through refining, to ensure with high confidence that the reservoir fluids can be moved from the reservoir to the refinery smoothly and without interruption.
Daftar Pustaka :
http://petrowiki.org/Flow_assurance_for_offshore_and_subsea_facilities
http://www.uio.no/studier/emner/matnat/math/MEK4450/h11/undervisningsmateriale/modul-5/MEK4450_FlowAssurance_pensum-2.pdf
Flow assurance is relatively new term in oil and gas industry. It refers to ensuring successful and economical flow of hydrocarbon stream from reservoir to the point of sale and is closely linked to multiphase flow technology.
Flow assurance developed because traditional approaches are inappropriate for deepwater production due to extreme distances, depths, temperatures or economic constraints. The term Flow Assurance was first used by Petrobras in the early 1990s in Portuguese as Garantia do Escoamento (pt::Garantia do Escoamento), meaning literally "Guarantee of Flow", or Flow Assurance.
Flow assurance by definiton focuses on the whole engineering and production life cycle from the reservoir through refining, to ensure with high confidence that the reservoir fluids can be moved from the reservoir to the refinery smoothly and without interruption.
Gambar. Scope of flow assurance
Sumber gambar : http://petrowiki.org/File%3AVol3_Page_554_Image_0001.png
- Pressure support consideration
It is necessary for sufficient pressure to be available to transport the hydrocarbons at the
required flow rates from the reservoir to the processing unit. Matters
that require consideration in this regard include:
1. Pressure loss in flowlines
2. Separator pressure setpoint
3. Pressure loss in wells
4. Artificial lift method selection
5. Remote multiphase boosting
6. Drag reduction
7. Slugging in horizontal wells
8. Gas lift system stability
9. Interaction with reservoir performance
http://petrowiki.org/Flow_assurance_for_offshore_and_subsea_facilities
http://www.uio.no/studier/emner/matnat/math/MEK4450/h11/undervisningsmateriale/modul-5/MEK4450_FlowAssurance_pensum-2.pdf
Pig Launcher
Pig Launcher
Pigging in the maintenance of pipelines refers to the practice of using pipeline inspection gauges or 'pigs' to perform various operations on a pipeline without stopping the flow of the product in the pipeline. Pigs get their name from the squealing sound they make while traveling through a pipeline. These operations include but are not limited to cleaning and inspection of the pipeline. This is accomplished by inserting the pig into a Pig Launcher - a funnel shaped Y section in the pipeline. The launcher is then closed and the pressure of the product in the pipeline is used to push it along down the pipe until it reaches the receiving trap - the 'pig catcher'.
Pigging has been used for many years to clean large diameter pipelines in the oil industry. Today, however, the use of smaller diameter pigging systems is now increasing in many continuous and batch process plants as plant operators search for increased efficiencies and reduced costs.
Pigging can be used for almost any section of the transfer process between, for example, blending, storage or filling systems. Pigging systems are already installed in industries handling products as diverse as lubricating oils, paints, chemicals, toiletries, cosmetics and foodstuffs.
Pigs are used in lube oil or paint blending to clean the pipes to avoid cross-contamination, and to empty the pipes into the product tanks (or sometimes to send a component back to its tank). Usually pigging is done at the beginning and at the end of each batch, but sometimes it is done in the midst of a batch, such as when producing a premix that will be used as an intermediate component.
Pigs are also used in oil and gas pipelines to clean the pipes. There are also 'smart pigs' used to inspect pipelines for the purpose of preventing leaks that can be explosive and dangerous to the environment. They usually do not interrupt production, though some product can be lost when the pig is extracted. They can also be used to separate different products in a multiproduct pipeline.
If the pipeline contains buttery valves, or reduced port ball valves, the pipeline cannot be pigged. Full port (or full bore) ball valves cause no problems because the inside diameter of the ball is the same as that of the pipe.
Daftar Pustaka :
http://www.jamisonproducts.com/pipeline-products/pig-launchers-receivers.html
https://en.wikipedia.org/wiki/Pigging
Pigging in the maintenance of pipelines refers to the practice of using pipeline inspection gauges or 'pigs' to perform various operations on a pipeline without stopping the flow of the product in the pipeline. Pigs get their name from the squealing sound they make while traveling through a pipeline. These operations include but are not limited to cleaning and inspection of the pipeline. This is accomplished by inserting the pig into a Pig Launcher - a funnel shaped Y section in the pipeline. The launcher is then closed and the pressure of the product in the pipeline is used to push it along down the pipe until it reaches the receiving trap - the 'pig catcher'.
Pig Launcher
Sumber gambar : http://www.tecpesa.es/images/products/1411638760piglauncher.jpg
Pigging has been used for many years to clean large diameter pipelines in the oil industry. Today, however, the use of smaller diameter pigging systems is now increasing in many continuous and batch process plants as plant operators search for increased efficiencies and reduced costs.
Pigging can be used for almost any section of the transfer process between, for example, blending, storage or filling systems. Pigging systems are already installed in industries handling products as diverse as lubricating oils, paints, chemicals, toiletries, cosmetics and foodstuffs.
Pigs are used in lube oil or paint blending to clean the pipes to avoid cross-contamination, and to empty the pipes into the product tanks (or sometimes to send a component back to its tank). Usually pigging is done at the beginning and at the end of each batch, but sometimes it is done in the midst of a batch, such as when producing a premix that will be used as an intermediate component.
Pigs are also used in oil and gas pipelines to clean the pipes. There are also 'smart pigs' used to inspect pipelines for the purpose of preventing leaks that can be explosive and dangerous to the environment. They usually do not interrupt production, though some product can be lost when the pig is extracted. They can also be used to separate different products in a multiproduct pipeline.
If the pipeline contains buttery valves, or reduced port ball valves, the pipeline cannot be pigged. Full port (or full bore) ball valves cause no problems because the inside diameter of the ball is the same as that of the pipe.
Daftar Pustaka :
http://www.jamisonproducts.com/pipeline-products/pig-launchers-receivers.html
https://en.wikipedia.org/wiki/Pigging
Subsea Pipeline Replacement
Leighton Enters Pipeline Replacement Project Offshore India
Leighton India has been awarded its fifth consecutive project with India’s Oil & Natural Gas Corporation (ONGC), taking the value of the total work awarded to the Company by ONGC to more than INR 5000 Crore over the past 5 years. The 1400 Crore Pipeline Replacement Project 3 (PRP3) follows on from the very successful completion of the Pipeline Replacement Project 2 in 2011.
PRP3 covers works in ONGC’s Mumbai High and Heera Oil and Gas fields off India’s west coast. The scope of work includes installation of 31 subsea pipeline segments, both rigid and flexible, of various diameters up to 16″ and totalling approximately 200kms in length, as well as associated pipeline risers, platform topsides modifications, hook-up activities and testing.
Much of the production and transportation infrastructure at Mumbai High was installed in the 1980’s. To assure asset integrity, ONGC has been progressively implementing a replacement program. The new pipelines will help ONGC extend field life and enhance production and operational safety.
Daftar Pustaka :
http://www.leighton.co.in/project/113/pipeline_replacement_project_3
http://www.offshoreenergytoday.com/leighton-enters-pipeline-replacement-project-offshore-india/
Leighton India has been awarded its fifth consecutive project with India’s Oil & Natural Gas Corporation (ONGC), taking the value of the total work awarded to the Company by ONGC to more than INR 5000 Crore over the past 5 years. The 1400 Crore Pipeline Replacement Project 3 (PRP3) follows on from the very successful completion of the Pipeline Replacement Project 2 in 2011.
PRP3 covers works in ONGC’s Mumbai High and Heera Oil and Gas fields off India’s west coast. The scope of work includes installation of 31 subsea pipeline segments, both rigid and flexible, of various diameters up to 16″ and totalling approximately 200kms in length, as well as associated pipeline risers, platform topsides modifications, hook-up activities and testing.
Much of the production and transportation infrastructure at Mumbai High was installed in the 1980’s. To assure asset integrity, ONGC has been progressively implementing a replacement program. The new pipelines will help ONGC extend field life and enhance production and operational safety.
Daftar Pustaka :
http://www.leighton.co.in/project/113/pipeline_replacement_project_3
http://www.offshoreenergytoday.com/leighton-enters-pipeline-replacement-project-offshore-india/
Kamis, 04 Februari 2016
Offshore Pipeline buckling
Offshore Pipeline Buckling
Buckling merupakan suatu proses dimana struktur tidak mampu mempertahankan bentuk aslinya. Buckling adalah masalah geometrik dasar dimana terjadi lendutan besar sehingga akan mengubah bentuk struktur. Fenomena tekuk atau buckling dapat terjadi pada sebuah struktur seperti :
- Kolom Langsing
- Lateral buckling balok
- Pelat tipis
- Cangkang silindris dibebani aksial sumbu
- Cangkang silindris dibebani tegak lurus sumbu
Pipeline dapat buckle secara global baik ke bawah (free span), lateral, atau secara vertikal.
Dalam DNV OS F101 Submarine Pipeline System, 2007 diterangkan mengenai kriteria desain untuk penentuan tebal pipa diantaranya adalah Lokal Buckling.
Lokal Buckling adalah modus tekuk terbatas singkat pada panjang pipa yang menyebabkan perubahan mencolok pada penampang seperti runtuh, kerutan pada dinding lokal dan uji puntir. Pada DNV - OS - F101 local buckling harus memenuhi 3 kriteria yaitu :
1. System Collapse
2. Propagation Buckling
3. Kombinasi kriteria pembebanan adalah menunjukkan kemampuan pipa baja yang akan diletakan di dasar laut terhadap semua gaya dan tekanan yang akan terjadi pada pipa. Dalam hal ini pipa dikenai kombinasi pembebanan terhadap momen tekuk, gaya aksial efektif, tekanan internal berlebih dan kombinasi pembebanan terhadap tekuk gaya aksial efektif, tekanan internal berlebih dan tekanan eksternal berlebih
Daftar Pustaka :
https://sasmita02.wordpress.com/category/pipeline/
http://riosinaga55.blog.com/2011/05/18/backling-tekukan/
http://hafyantoekos.blogspot.co.id/2015/02/pipeline-global-buckling.html
Buckling merupakan suatu proses dimana struktur tidak mampu mempertahankan bentuk aslinya. Buckling adalah masalah geometrik dasar dimana terjadi lendutan besar sehingga akan mengubah bentuk struktur. Fenomena tekuk atau buckling dapat terjadi pada sebuah struktur seperti :
- Kolom Langsing
- Lateral buckling balok
- Pelat tipis
- Cangkang silindris dibebani aksial sumbu
- Cangkang silindris dibebani tegak lurus sumbu
Pipeline dapat buckle secara global baik ke bawah (free span), lateral, atau secara vertikal.
Dalam DNV OS F101 Submarine Pipeline System, 2007 diterangkan mengenai kriteria desain untuk penentuan tebal pipa diantaranya adalah Lokal Buckling.
Lokal Buckling adalah modus tekuk terbatas singkat pada panjang pipa yang menyebabkan perubahan mencolok pada penampang seperti runtuh, kerutan pada dinding lokal dan uji puntir. Pada DNV - OS - F101 local buckling harus memenuhi 3 kriteria yaitu :
1. System Collapse
2. Propagation Buckling
3. Kombinasi kriteria pembebanan adalah menunjukkan kemampuan pipa baja yang akan diletakan di dasar laut terhadap semua gaya dan tekanan yang akan terjadi pada pipa. Dalam hal ini pipa dikenai kombinasi pembebanan terhadap momen tekuk, gaya aksial efektif, tekanan internal berlebih dan kombinasi pembebanan terhadap tekuk gaya aksial efektif, tekanan internal berlebih dan tekanan eksternal berlebih
Daftar Pustaka :
https://sasmita02.wordpress.com/category/pipeline/
http://riosinaga55.blog.com/2011/05/18/backling-tekukan/
http://hafyantoekos.blogspot.co.id/2015/02/pipeline-global-buckling.html
Hydrotest pada pipa offshore
Hydrotest pada pipa offshore
Hydro test digunakan untuk menentukan integritas pipa. Ada beberapa cacat yang dapat di deteksi oleh hydrotest yaitu :
1. Cacat pada material yang ada
2. Stress Corrosion Cracking (SCC) dan properti mekanis pipa
3. Sel korosi aktif
4. Adanya spot yang memungkinkan terjadinya kerusakan akibat adanya hidrogen
Ada beberapa cacat yang tidak dapat di deteksi oleh hydrostatic test yaitu cacat pada material sub kritik yang tidak dapat dideteksi oleh hidrostatik tes.
Ketika sebuah pipa di desain untuk beroperasi pada tekanan operasi maksimum, harus di tes terlebih dahulu untuk memastikan struktur mampu menahan internal pressure sebelum digunakan. Secara umum hidrostatik tes adalah mengisi pipa dengan air dan memompa tekanan hingga nilai yang lebih tinggi dari tekanan maksimum operasi yang diijinkan (MAOP).
Kode referensi, standar dan spesifikasi :
- ANSI B 31.8 : Gas Transmission and Distribution Piping System
- ANSI B 31.4 : Liquid Petroleum Transportation Piping System
- API RP 1110 : Pressure Testing of Liquid Petroleum Pipelines
- ASME Sec VIII : Boilers and Pressure Vessels Code Div. 1
- DNV 81 : Rules for Submarine Pipeline
Daftar Pustaka :
pgjonline.com/2009/12/17/pipeline-hydro-test-pressure-determination/
https://dwinirestu.wordpress.com/2015/02/03/hydrotest-on-offshore-pipeline/
Hydro test digunakan untuk menentukan integritas pipa. Ada beberapa cacat yang dapat di deteksi oleh hydrotest yaitu :
1. Cacat pada material yang ada
2. Stress Corrosion Cracking (SCC) dan properti mekanis pipa
3. Sel korosi aktif
4. Adanya spot yang memungkinkan terjadinya kerusakan akibat adanya hidrogen
Ada beberapa cacat yang tidak dapat di deteksi oleh hydrostatic test yaitu cacat pada material sub kritik yang tidak dapat dideteksi oleh hidrostatik tes.
Ketika sebuah pipa di desain untuk beroperasi pada tekanan operasi maksimum, harus di tes terlebih dahulu untuk memastikan struktur mampu menahan internal pressure sebelum digunakan. Secara umum hidrostatik tes adalah mengisi pipa dengan air dan memompa tekanan hingga nilai yang lebih tinggi dari tekanan maksimum operasi yang diijinkan (MAOP).
Kode referensi, standar dan spesifikasi :
- ANSI B 31.8 : Gas Transmission and Distribution Piping System
- ANSI B 31.4 : Liquid Petroleum Transportation Piping System
- API RP 1110 : Pressure Testing of Liquid Petroleum Pipelines
- ASME Sec VIII : Boilers and Pressure Vessels Code Div. 1
- DNV 81 : Rules for Submarine Pipeline
Daftar Pustaka :
pgjonline.com/2009/12/17/pipeline-hydro-test-pressure-determination/
https://dwinirestu.wordpress.com/2015/02/03/hydrotest-on-offshore-pipeline/
Rabu, 03 Februari 2016
Pengelasan Bawah Air oleh Diver
Pengelasan Bawah Air oleh Diver
Teknologi pengelasan bawah air (Underwater Welding) adalah pengelasan yang dilakukan di bawah air, umumnya laut. Pengelasan bawah air digunakan untuk memperbaiki kerusakan yang pada badan kapal, memperbaiki struktur kapal, konstruksi pipa, konstruksi jembatan maupun konstruksi pengeboran lepas pantai.
Mengelas di dalam air membutuhkan keterampilan khusus. Karena pengerjaan las bawah air rentan terhadap resiko kecelakaan bagi seorang welder beberapa kasus kecelakaan seperti electrical shock, gas tabung yang digunakan untuk mengelas di dalam laut berpotensi meledak, nitrogen yang digunakan untuk pengelasan bisa terhirup dan bercampur dengan darah, hingga resiko karena faktor alam bawah laut. Selain terampil dalam pengelasan seorang welder juga harus mampu menyelam, sehingga seorang pekerja las bawah air juga merupakan seorang diver.
Metode pengelasan bawah air terdiri dari dua kategori yaitu pengelasan basah ( Wet Underwater Welding) dan pengelasan kering (Dry Underwater Welding).
Pada metode pengelasan basah pengelasan berlangsung dalam keadaan basah artinya elektrode maupun benda berhubungan langsung dengan air. Aplikasi pengelasan sampai kedalaman 150 m. Adapun proses pengelasan yang digunakan adalah SMAW, FCAW, dan MIG.
Metode pengelasan kering tidak berbeda dengan pengelasan udara terbuka. Hal ini dapat dilakukan dengan bantuan suatu peralatan yang bertekanan tinggi yang biasa disebut Dry Hyperbaric Weld Chamber, alat ini didesain kedap air. Seorang welder tidak boleh langsung terjun pada kedalaman yang dituju tetapi harus menyesuaikan terlebih dahulu step by step tekanan yang terjadi pada kedalaman tertentu.
Daftar Pustaka :
http://kapal.ptbps.com/2015/02/teknik-pengelasan-basah-bawah-air-wet.html
http://ilmu-dewa.blogspot.co.id/2013/07/pengelasan-basah-dalam-air-underwater.html
Teknologi pengelasan bawah air (Underwater Welding) adalah pengelasan yang dilakukan di bawah air, umumnya laut. Pengelasan bawah air digunakan untuk memperbaiki kerusakan yang pada badan kapal, memperbaiki struktur kapal, konstruksi pipa, konstruksi jembatan maupun konstruksi pengeboran lepas pantai.
Gambar. Pengelasan bawah air.
Sumber gambar : https://nainamania.files.wordpress.com/2015/01/welders.png
Mengelas di dalam air membutuhkan keterampilan khusus. Karena pengerjaan las bawah air rentan terhadap resiko kecelakaan bagi seorang welder beberapa kasus kecelakaan seperti electrical shock, gas tabung yang digunakan untuk mengelas di dalam laut berpotensi meledak, nitrogen yang digunakan untuk pengelasan bisa terhirup dan bercampur dengan darah, hingga resiko karena faktor alam bawah laut. Selain terampil dalam pengelasan seorang welder juga harus mampu menyelam, sehingga seorang pekerja las bawah air juga merupakan seorang diver.
Metode pengelasan bawah air terdiri dari dua kategori yaitu pengelasan basah ( Wet Underwater Welding) dan pengelasan kering (Dry Underwater Welding).
Pada metode pengelasan basah pengelasan berlangsung dalam keadaan basah artinya elektrode maupun benda berhubungan langsung dengan air. Aplikasi pengelasan sampai kedalaman 150 m. Adapun proses pengelasan yang digunakan adalah SMAW, FCAW, dan MIG.
Metode pengelasan kering tidak berbeda dengan pengelasan udara terbuka. Hal ini dapat dilakukan dengan bantuan suatu peralatan yang bertekanan tinggi yang biasa disebut Dry Hyperbaric Weld Chamber, alat ini didesain kedap air. Seorang welder tidak boleh langsung terjun pada kedalaman yang dituju tetapi harus menyesuaikan terlebih dahulu step by step tekanan yang terjadi pada kedalaman tertentu.
Daftar Pustaka :
http://kapal.ptbps.com/2015/02/teknik-pengelasan-basah-bawah-air-wet.html
http://ilmu-dewa.blogspot.co.id/2013/07/pengelasan-basah-dalam-air-underwater.html
Selasa, 02 Februari 2016
Stabilitas Pipa Bawah Laut
Stabilitas Pipa Bawah Laut
Pipa bawah laut di desain untuk mampu menahan beban yang dikenakan kepadanya baik itu akibat gelombang atau arus (gaya hidrodinamika). Gaya yang mempengaruhi antara lain : Gaya drag, gaya ini dapat menyebabkan bergesernya pipa. Gaya angkat, gaya ini dapat menyebabkan pengurangan berat terendam pada pipa.
Untuk mengatasi masalah kestabilan pipa bawah laut maka ada beberapa hal yang dapat dilakukan yaitu pipa dapat dikubur di bawah laut, pembuatan parit, pembuatan tanggul batu, menambahkan matras, atau dengan penambahan berat pipa dengan menambahkan selimut beton pada pipa.
Pipa bawah laut di desain untuk mampu menahan beban yang dikenakan kepadanya baik itu akibat gelombang atau arus (gaya hidrodinamika). Gaya yang mempengaruhi antara lain : Gaya drag, gaya ini dapat menyebabkan bergesernya pipa. Gaya angkat, gaya ini dapat menyebabkan pengurangan berat terendam pada pipa.
Gambar. Gaya hidrodinamika
Sumber gambar : http://112.220.84.59:8080/PmcXml_WorkBench/upload/snak/E1JSE6/2013/v5n4/E1JSE6_2013_v5n4_598_f007.jpg
Untuk mengatasi masalah kestabilan pipa bawah laut maka ada beberapa hal yang dapat dilakukan yaitu pipa dapat dikubur di bawah laut, pembuatan parit, pembuatan tanggul batu, menambahkan matras, atau dengan penambahan berat pipa dengan menambahkan selimut beton pada pipa.
Senin, 01 Februari 2016
Mitigasi Free Span
Mitigasi Free Span
Pipa bawah laut dapat mengalami free span akibat berbagai macam kondisi seperti permukaan dasar laut yang tidak rata. Apabila free span terlalu panjang melebihi batas ijinnya, Vortex Induced Vibration (VIV) dapat menyebabkan pipa mengalami kelelahan (fatigue) dan menyebabkan kegagalan (failure).
Free span menjadi penyebab masalah baik dalam aspek statis maupun dinamis. Jika panjang free span terlalu panjang, pipa akan over-stressed dengan berat pipa ditambah isinya. Gaya drag karena near bottom currental berkontribusi terhadap beban statis. Untuk mengurangi masalah rentang statis, mid-span supports, seperti kaki mekanik atau kantong pasir-semen atau kasur, dapat digunakan.
Free span juga dipengaruhi gerakan dinamis yang disebabkan oleh arus, yang disebut getaran diinduksi pusaran (Vortex Induced Vibration). Getaran dimulai ketika frekuensi shedding dekat dengan frekuensi dari pipe span. Frekuensi alami pipa meningkat, dengan mengurangi panjang span, VIV akan berkurang dan dihilangkan. Menambahkan peralatan penekan VIV seperti strakes atau hydrofoils juga dapat mencegaj pipa dari bergetar.
Dibawah ini tabel mitigasi untuk mencegah masalah spanning statis dan dinamis
Pipa bawah laut dapat mengalami free span akibat berbagai macam kondisi seperti permukaan dasar laut yang tidak rata. Apabila free span terlalu panjang melebihi batas ijinnya, Vortex Induced Vibration (VIV) dapat menyebabkan pipa mengalami kelelahan (fatigue) dan menyebabkan kegagalan (failure).
Free span menjadi penyebab masalah baik dalam aspek statis maupun dinamis. Jika panjang free span terlalu panjang, pipa akan over-stressed dengan berat pipa ditambah isinya. Gaya drag karena near bottom currental berkontribusi terhadap beban statis. Untuk mengurangi masalah rentang statis, mid-span supports, seperti kaki mekanik atau kantong pasir-semen atau kasur, dapat digunakan.
Free span juga dipengaruhi gerakan dinamis yang disebabkan oleh arus, yang disebut getaran diinduksi pusaran (Vortex Induced Vibration). Getaran dimulai ketika frekuensi shedding dekat dengan frekuensi dari pipe span. Frekuensi alami pipa meningkat, dengan mengurangi panjang span, VIV akan berkurang dan dihilangkan. Menambahkan peralatan penekan VIV seperti strakes atau hydrofoils juga dapat mencegaj pipa dari bergetar.
Dibawah ini tabel mitigasi untuk mencegah masalah spanning statis dan dinamis
Tabel. Mitigasi Free Span
Sumber tabel : https://anindamiftahdhiyar.files.wordpress.com/2013/02/tabel-free-span.png?w=522
Daftar Pustaka :
http://hafyantoekos.blogspot.co.id/2015/02/pipeline-free-span-mitigation.html
http://pricilia281.blogspot.co.id/2014/02/free-span-mitigation.html
Analisa Kelelahan Free Span
Analisa Kelelahan Free Span
Free span adalah suatu keadaan yang dialami pipa dimana adanya suatu bentangan terhadap dasar laut atau seabed. Free span sangat beresiko dan memiliki tingkat ancaman yang cukup tinggi pada konstruksi pipa bawah laut. Adanya free span dapat menimbulkan terjadinya bending sebagai akibat dari beban statis yang terjadi pada pipa. Sedangkan adanya getaran pada pipa dapat menimbulkan terjadinya fenomena vortex shedding diakibatkan oleh beban dinamis pada pipa. Oleh karena itu, untuk menganalisa panjang jalur pipa maksimum yang mengalami free span harus dilakukan dua macam kondisi yaitu kondisi statis dan kondisi dinamis,
Dalam analisa kondisi free span berdasarkan adanya kasus pembebanan pada pipa ada 3 macam analisis kondisi yaitu kondisi Instalasi, kondisi Hydrotest serta kondisi Operasi.
Untuk analisa kondisi instalasi dilakukan pada jenis pipa baru, material pengisi masih kosong seta pembebanan eksternal secara periodik 1 tahun. Untuk analisa kondisi hydrotest dilakukan pada jenis pipa baru, berisi air secara penuh, dan pembebanan secara periodik 1 tahun. Sedangkan untuk analisa pada kondisi operasi dilakukan pada pipa yang sudah mengalami korosi, material pipa berisi gas serta pembebanan dari luar secara periodik 100 tahun.
Dari penjelasan diatas, pada setiap kondisi akan dianalisa free span pada pipa akibat adanya beban statis sehingga dapat diketahui panjang span yang diijinkan.
Semua analisi free span mengacu pada kode standar DNV - RP - F105 Free Spanning Pipelines
Free span adalah suatu keadaan yang dialami pipa dimana adanya suatu bentangan terhadap dasar laut atau seabed. Free span sangat beresiko dan memiliki tingkat ancaman yang cukup tinggi pada konstruksi pipa bawah laut. Adanya free span dapat menimbulkan terjadinya bending sebagai akibat dari beban statis yang terjadi pada pipa. Sedangkan adanya getaran pada pipa dapat menimbulkan terjadinya fenomena vortex shedding diakibatkan oleh beban dinamis pada pipa. Oleh karena itu, untuk menganalisa panjang jalur pipa maksimum yang mengalami free span harus dilakukan dua macam kondisi yaitu kondisi statis dan kondisi dinamis,
Dalam analisa kondisi free span berdasarkan adanya kasus pembebanan pada pipa ada 3 macam analisis kondisi yaitu kondisi Instalasi, kondisi Hydrotest serta kondisi Operasi.
Untuk analisa kondisi instalasi dilakukan pada jenis pipa baru, material pengisi masih kosong seta pembebanan eksternal secara periodik 1 tahun. Untuk analisa kondisi hydrotest dilakukan pada jenis pipa baru, berisi air secara penuh, dan pembebanan secara periodik 1 tahun. Sedangkan untuk analisa pada kondisi operasi dilakukan pada pipa yang sudah mengalami korosi, material pipa berisi gas serta pembebanan dari luar secara periodik 100 tahun.
Dari penjelasan diatas, pada setiap kondisi akan dianalisa free span pada pipa akibat adanya beban statis sehingga dapat diketahui panjang span yang diijinkan.
Semua analisi free span mengacu pada kode standar DNV - RP - F105 Free Spanning Pipelines
Gambar. Free span.
Sumber gambar : http://fishsafe.eu/media/5557/pipeline_span_3_374x118.jpg
Tahapan dari analisis free span sebagai berikut :
1. Data Lingkungan
Tahapan pertama dari analisa free span adalah akuisisi dan pengecekan data lingkungan laut pada lokasi tinjauan. Parameter yang mempengaruhi yaitu parameter tanah, metocean data.
2. Data Geoteknik
Data geoteknik pada umumnya diperoleh dari survei in-situ yang dilakukan pada lokasi tinjauan dan tes laboratorium. Data yg dibutuhkan antara lain :
1. Data jenis tanah, void ratio, submerged unit weight, indeks plastisitas
2. Kondisi tegangan dan regangan in-situ, tegangan geser, untuk kondisi drained maupun undrained, dan siklus regangan geser.
3. Parameter settlement tanah.
3. Data Arus
Asumsi yang digunakan adalah arus dianggap steady current terdiri dari :
1. Arus pasang surut
2. Wind induced current
3. Storm surge induced current
4. Density driven current
4. Data Gelombang
Data gelombang didapatkan dengan dua cara yaitu data pengukuran langsung di laut dan data hasil hindcasting.
Daftar Pustaka :
http://digilib.its.ac.id/public/ITS-Undergraduate-23295-4208100017-Abstract_id.pdf
igilib.itb.ac.id/files/disk1/629/jbptitbpp-gdl-ratnapuspi-31432-4-2008ta-3.pdf
Teknologi Pengelasan Pipa
Teknologi Pengelasan Pipa
Pengelasan atau welding adalah salah satu teknik penyambungan logam dengan cara mencairkan sebagian logam induk dan logam pengisi dengan atau tanpa tekanan dan dengan atau tanpa logam penambah dan menghasilkan sambungan yang kontinyu.
Tungsten Inert Gas
Tungsten Inert Gas adalah proses pengelasan dimana busur nyala listrik ditimbulkan oleh elektroda tungsten dengan benda kerja logam. Daerah pengelasan dilindungi oleh gas lindung (gas tidak aktif) agar tidak terkontaminasi udara luar, Tungsten Inert Gas disebut juga Gas Tungsten Arc Welding (GTAW) merupakan salah satu dari bentuk las busur listrik (Arc Welding) yang menggunakan inert gas sebagai pelindung dengan tungsten atau wolfram sebagai elektrode.
Proses pengelasan bisa dilakukan secara otomatis, Filler metal ditambahkan ke dalam daerah las dengan cara mengumpankan sebatang kawat polos. GTAW berfungsi untuk mengelas pipa pada posisi sulit seperti pada stainless steel. GTAW sudah bisa dilakukan secara otomatis.
Elektroda tungsten berfungsi sebagai pencipta busur nyaka saja yang digunakan untuk mencairkan kawat las yang ditambahkan dari luar benda yang akan disambung menjadi satu kesatuan sambungan.
Keuntungan proses GTAW yaitu menghasilkan pengelasan bermutu tinggi pada bahan-bahan ferrous dan non ferrous, selain itu bisa digunakan untuk membuat root pass bermutu tinggi dari arah satu sisis pada berbagai jenis bahan.
Kelemahan GTAW yaitu laju pengisian lebih rendah dibandingkan proses lain.
Daftar Pustaka :
http://cipretx.blogspot.co.id/
Pengelasan atau welding adalah salah satu teknik penyambungan logam dengan cara mencairkan sebagian logam induk dan logam pengisi dengan atau tanpa tekanan dan dengan atau tanpa logam penambah dan menghasilkan sambungan yang kontinyu.
Tungsten Inert Gas
Tungsten Inert Gas adalah proses pengelasan dimana busur nyala listrik ditimbulkan oleh elektroda tungsten dengan benda kerja logam. Daerah pengelasan dilindungi oleh gas lindung (gas tidak aktif) agar tidak terkontaminasi udara luar, Tungsten Inert Gas disebut juga Gas Tungsten Arc Welding (GTAW) merupakan salah satu dari bentuk las busur listrik (Arc Welding) yang menggunakan inert gas sebagai pelindung dengan tungsten atau wolfram sebagai elektrode.
Gambar. Tungsten inert gas.
Sumber gambar : http://derijcke.com/knowledgebase/welding/tig2.jpg
Proses pengelasan bisa dilakukan secara otomatis, Filler metal ditambahkan ke dalam daerah las dengan cara mengumpankan sebatang kawat polos. GTAW berfungsi untuk mengelas pipa pada posisi sulit seperti pada stainless steel. GTAW sudah bisa dilakukan secara otomatis.
Elektroda tungsten berfungsi sebagai pencipta busur nyaka saja yang digunakan untuk mencairkan kawat las yang ditambahkan dari luar benda yang akan disambung menjadi satu kesatuan sambungan.
Keuntungan proses GTAW yaitu menghasilkan pengelasan bermutu tinggi pada bahan-bahan ferrous dan non ferrous, selain itu bisa digunakan untuk membuat root pass bermutu tinggi dari arah satu sisis pada berbagai jenis bahan.
Kelemahan GTAW yaitu laju pengisian lebih rendah dibandingkan proses lain.
Daftar Pustaka :
http://cipretx.blogspot.co.id/
Jumat, 29 Januari 2016
How pipeline pig work
How pipeline pig work
Proses pengolahan dalam industri minyak banyak melibatkan sistem perpipaan. Berbagai jenis pipa digunakan untuk menyalurkan fluida dari satu lokasi ke lokasi lain. Dalam hal ini sistem perpipaan sangat penting peranannya, oleh karena itu hambatan atau kemacetan dalam sistem pipa harus dihindari sehinggan muncul suatu alat yang disebut dengan "pig". Alat ini berfungsi untuk membersihkan bagian dalam pipa dengan prinsip mengelap atau menggosok bagian dalam pipa dengan sebuah benda padat.
Berikut ini prinsip Pig Launcher :
1. Tutup main line trap valve
2. Tutp kicker trap valve
3. Buka closure
4. Masukan pig, tutup closure
5. Buka sebagian kicker trap valve
6. Buka main line trap valve
7. Buka kicker trap valve
8. Tutup sebagian main line by pass valve
9. Pig dijalankan
10. Buka main line by pass valve
11. Tutup main line trap valve
12. Tutp by pass trap valve
13. Pig keluar
Daftar pustaka :
http://eprints.undip.ac.id/36544/1/Tesis-final-25_maret-pdf.pdf
https://www.youtube.com/watch?v=CDHtL-J1Xxo
Proses pengolahan dalam industri minyak banyak melibatkan sistem perpipaan. Berbagai jenis pipa digunakan untuk menyalurkan fluida dari satu lokasi ke lokasi lain. Dalam hal ini sistem perpipaan sangat penting peranannya, oleh karena itu hambatan atau kemacetan dalam sistem pipa harus dihindari sehinggan muncul suatu alat yang disebut dengan "pig". Alat ini berfungsi untuk membersihkan bagian dalam pipa dengan prinsip mengelap atau menggosok bagian dalam pipa dengan sebuah benda padat.
Gambar. Pig Launcher
Sumber gambar : http://www.piping-engineering.com/wp-content/uploads/2013/11/pig-launcher-for-gas-service.jpg
Berikut ini prinsip Pig Launcher :
1. Tutup main line trap valve
2. Tutp kicker trap valve
3. Buka closure
4. Masukan pig, tutup closure
5. Buka sebagian kicker trap valve
6. Buka main line trap valve
7. Buka kicker trap valve
8. Tutup sebagian main line by pass valve
9. Pig dijalankan
10. Buka main line by pass valve
11. Tutup main line trap valve
12. Tutp by pass trap valve
13. Pig keluar
Daftar pustaka :
http://eprints.undip.ac.id/36544/1/Tesis-final-25_maret-pdf.pdf
https://www.youtube.com/watch?v=CDHtL-J1Xxo
Konstruksi Pipa Bawah Laut
Konstruksi Pipa Bawah Laut
Pada pekerjaan konstruksi pipa bawah laut terdiri dari beberapa tahapan, yaitu :
1. Pre Lay Survey
Survey ini dilakukan sebelum pemasangan pipa dilakukan.
Tujuan dari survey ini yaitu :
- -
Menyediakan informasi mengenai batimetri, dan
menyediakan informasi mengenai posisi pipa yang telah existing.
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Mengetahui adanya endapan puing-puing yang dapat
membahayakan pada rute pipa.
Survey yang dilakukan pada tahapan ini
yaitu :
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Side Scan Sonar
Gambar. Side scan sonar.
Sumber gambar : http://www.jwfishers.com/graphics/hr/sss1HR.jpg
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Sub Bottom Profiler
Gambar. Sub bottom profiler
Sumber gambar : http://filemaker2-server.cbl.umces.edu/sensorimages/9901-SB216S.gif
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- Echo Sounder
Gambar. Echo sounder.
Sumber gambar : http://www.worldfishing.net/__data/assets/image/0020/100847/Koden-Digital-Color-LCD-Echo-Sounder-CVS-1410_1410HS.jpg
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Magnetometer
Gambar. Magnetometer.
Sumber gambar : https://www.trifield.com/images/dcmagnetometer-guass-hs-large.jpg
2. Pipeline Installation
Pada tahapan ini terdiri dari
metode apa saja yang dapat digunakan dalam instalasi pipa bawah laut.
Penjelasan mengenai pipeline installation telah dijelaskan pada artikel Metode
Instalasi Pipa Bawah Laut.
3. Tie-in / Riser Installation
Setelah pipa selesai dipasang didasar laut, selanjutnya adalah pemasangan riser. Riser merupakan bagian vertikal pada pipa yang berfungsi menghubungkan pipa bawah laut dengan fasilitas produksi yang ada pada platform. Metode yang digunakan untuk pemasangan riser yaitu metode tie-in atau penghubung antara pipa bawah air dengan riser dibuat dengan pengelasan, flanging, atau mechanical connector.
4. Trenching Operation
Trenching operation merupakan proses perlindungan pipa dengan cara menguburkan pipa ke dalam tanah. Trenching Operation terdiri dari 3 metode yaitu : Pre trenching, simultaneous trenching, dan post trenching.
5. As Laid Survey
Tujuan dilakukannya tahapan ini adalah untuk merekam posisi dan status dari pipa yang telah dipasang
Daftar Pustaka :
http://digilib.itb.ac.id/files/disk1/455/jbptitbpp-gdl-muhammadfi-22723-3-2012ta-2.pdf
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