Pipeline
is a transportation of goods through a pipe. For underwater pipeline the most
common goods is oil and gas. Generally pipeline is welding using 5G position
with two kind welding techniques. First one is downhill, the most common use
for pipeline. The welding start from above the pipe and go through the bottom
of the pipe. Second is uphill, the opposite way of downhill. Pipeline welding
using downhill technique because this technique is faster than uphill. But for
toughness, uphill technique is still better than downhill. Celluloid is the
most common welding consumable that use for welding in pipeline. For welding
technique is depend on client requirement, but nowadays welding in pipeline is
using MIG or for manual is GTAW.
The
pipeline have some several parts, there are:
- Mainline. Mainline is the primary line that transport goods such as oil or gas from manifold to ship or rig.
- Tie-in. Tie-in contains of flange, pipe, and pipe bend. The function of tie-in is a connector between risers and mainline.
- Flange: Flange is a joint that can freely open or close. Flange is bolting not welding to make it easier to maintain.
- Pipe bend: A pipe that bend to transport the goods from mainline to riser.
- Riser: A part of pipeline to transport the goods from mainline to sea surface.
Generally
for pipeline construction there are two kind of design, strain-based pipeline
and stress-based pipeline. Stress-based pipeline is a conventional design of
pipeline. The pipeline characteristic is stress-based, in the other word is the
pipeline can bear the stress good enough. This is designed for safety use but
the cost is expensive because using too many material. Nowadays the pipeline
design is using strain-based design. It is cheaper and more efficient, but need
a good calculation of design.
Pipe
Laying
Installing
pipeline underwater is called pipe laying. There are three types of laying,
S-lay, J-lay, and nowadays there is a reeling installation. The different from
three of them is the shape of the pipe when went from a barge to seabed. S-lay
laying pipe usually use for small size of pipe, when J-lay and reeling is for
big size installation.
Pipeline
Construction Line
There
are two types of pipeline construction, conventional construction and reeling.
Nowadays contractor start change their pipeline construction to reeling method.
Conventional construction is to construct the pipeline above the ship/ barge.
In the other hand reeling construction is to make the pipe in land, reel it and
take it to the sea.
The
example of conventional pipeline method is on US EPCI company’s barge. Figure 1
is a flow chart of pipeline conventional method.
Figure 1. Conventional pipeline installation flowchart.
The
barge will bring the pipe to the construction site, another barge also bring it
into the site. In location site the barge will put down the anchor. Using a
help from tugboat the barge need to get a good position of an anchor to hold
the barge getting pulled by pipeline when the pipeline start to release from
the barge. When it settle the barge start their construction line.
First
the pipe from deck or barge will go into construction line. The pipe will went
through beadstall. In beadstall, the pipe will be check the code, cleaning the
pipe, and also some preheating is applied into the pipe. If there is something
wrong with the pipe code or rejected the pipe will go to quarantine place.
After preheating, the pipe will go to the station. Station is a place where the
pipe start to weld, NDT test, coating, and in the end is release it into the
seabed. How many station on the ship is depends on client demand, but usually
there is 9 stations on the ship. First station is for root welding station.
Welding technique use in project is depend on the client demand. When it finish
it will go to other station to do another welding layer, and so on in other
station until finishing the capping weld. After finishing the welding, NDT test
will do to check the welding result. The most common NDT test is UT or nowadays
is AUT. But sometimes radiography test also use to inspect the welding. If
there is a problem, the construction line will stop and welder will be call to
repair the welding. If it can't be repair, the pipeline will be cut off and
replace with a new pipe. After the NDT station pipeline will go to the next
station which is a coating station. In this station they will applied a coating
for pipeline joint, a pipeline coating already installed in land. The coating
that use for joint is Heat Shrink Sleeves (HSS) coating. After finishing the
coating, anode installation will be done, depends on client demand. Later the
pipe will be release into the sea. Pipe will go from the barge trough a stinger
and later go into the seabed. The pipeline will leave the barge and went through
the seabed create an "S" shape. That pipe laying is called S-lay
pipe.
Reference:
Hutagalung, Andi A., Albert Hutama. 2013. “Phase III Preparation CAPEX
NO102 and QC Department Batam Marine Base”. Bandung: ITB.
George Gilbert Mattew
Student ID. 155 12 061
Course: KL4220 Subsea Pipeline
Prof. Ir. Ricky Lukman Tawekal, MSE, Ph. D./ Eko Charnius Ilman, ST, MT
Ocean Engineering Program, Institut Teknologi Bandung
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