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Subsea Pipeline Installation : Pipelaying
Here is the summary of OIC responsibilities during typical shallow water pipelay operations:
Installing a barge real time electronic positioning system onboard the lay barge and onboard the anchor handling vessel. This is a mandatory requirement to ensure safe operation during anchor running & maneuvering of all marine vessels. All anchor handling operations will be suspended if the system on any of the vessels is not operational.
The work will be executed with an approved anchor patterns and catenaries, together with approved barge, trench vessel, tugs and other vessels movements along the entire length of the job. The barge will be set up in lay mode and in the correct position for start-up of pipelaying and carrying out all preparatory work for installation.
Part of the initial activities is to cut loose and remove all tie-down materials used to secure Pipeline material for transportation and offloading as required to maintain pipelay progress. This activities need to be planned properly to ensure no bottlenecking during pipelay operations.
To maintain high quality production, it is mandatory to remove all foreign matter from bevelled ends and inside of pipe including cleaning with power brush prior to welding, brush and clean all finished welds. This activities will be monitored closely by QA/QC personnel.
The linepipes will be properly handled, align using internal line-up clamps, welding and lowering Pipeline to seabed. All welding works will be inspected by radiographic inspection, UT and all other non-destructive inspections and testings including visual inspection. For all AUT & RT requirements for Pipelines, RT equipments will be inspected & approved by the client. There is a complete laboratory set up on the barge for automatic film processing which also including the dry file viewing facilities.
Part of the pipelay operation, is to carry out a post-installation survey of the cable crossings (if any), span rectification, determining and plotting the final position of these items and identifying all unsupported Pipeline spans. These activities can be done with the main work barge or by other work vessel a few days behind the barge operations. Again, this simultaneous operation require a properly planned schedule.
Bow String Pipeline Start-up
Not to forget; all welded pipe joints will be coated/wrapped and holiday detected and carry out all repairs (should there is any) as necessary for such coating and wrapping.
The pipeline will be cap-off and laid on seabed awaiting for any future spool or PLEM (Pipeline End Manifold) installation.
During laying operation, pipeline profile monitoring by diver and ROV shall be conducted at a minimum frequency of three (3) times per shift. The ROV will also be used for checking of anchor lines over existing pipelines (if any).
Sometimes the client require OIC to install pingers which have a 6 month life period on marker buoys attached to the start-up/ laydown heads to facilitate locating of these heads in future.
A post-lay pre-flood video surveys will be perform to identify an unsupported spans, flowline coating damage areas, etc. and rectify same. Final as-built surveys will be done following hydrotest, dewatering and drying activities.
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Posted by : Sulaiman Sabur |
| Biography : Author (also the WebMaster) hold a degree in Mechanical Engineering from University of Malaya. He has extensive experience in offshore construction and currently employed by one of the Major Offshore Construction Company in Malaysia. |
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17 Responses to 'Subsea Pipeline Installation : Pipelaying'
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on 8th, December
for the palm oil millers…
the method of pipeline installation that written by SULAIMAN are totally different from our conventional method in palm oil industries.. but i think how SULAIMAN’s do that things, can give us an inspirations during we do our job, especially when we lying a pipeline for the Raw Water, Final Effluent, Steam Pipe Line and CPO Storage Tank Piping. the methods and procuders being difference due to the piping material that we used, either a Stainless Steel Pipe, HDPE, GI or Steam Pipe, the size of pipe for the flowrate volume and the thinkness for the pressure and also how we lay it and fitted for the minimum friction loss.
The main things here, “how we observe and plan to detemine the pipe leakage during installation, less friction loss, cost and to avoid the bottleneck” Think it….
on 8th, December
Amy,
I think Hydrotest should give you indication for leak. SUbsea pipeline is tested up to 1.2 of its design pressure. We use water + Fluorescent during hydortesting. Fluorescent is use to give indication where the leak is…
on 8th, December
ya.. ngam tu olet… pas flashing pipeline kena buat H.T lebih kurang 1.2 s.f daripada pipe design pressure..
sebab kitaorg punya welder ni lesen keta ma motor jak ada, itu pun kalau ada… hehheh.. TQ
on 8th, December
every where is the sama la amy… still bound to API… nanti boleh la melawat kilang sawit…
on 22nd, August
kind you please give me the factors and loadings during design of pipe stingers..or nay drawing of an stringer/
on 5th, September
When is it necessaries to laydown the pipe with water (laydown with water)?…In this case do we need to flush the water first or straight away do the hidrotest?
on 5th, September
Hi Megat, it is a good area to explore.. the WET LAY!
My current employer do have 2-3 times experiencing wet lay of pipeline. Here is my answer to your question…
1. When it necessary to laydown the pipe with water…
- Client design the pipe to be laid in WET.
- During laying the pipe, it was found that the pipe string is too buoyant (Cases happen in pipe without concrete coating)
- Accident happen the pipe string is leak and its flooded.
- Installation contractor for get to close the Start up head valve.. he he he … or the valve is accidentally opened.
2. In this case do we need to flush the water firs or straight away do the hydrotest?
- I strongly believe you don’t have to flush (assuming you complete the pipelay and its design to be laid wet).
- But you cannot directly Hydrotest… You have to perform pigging and gauging first to ensure the pipe is clean and Gauging shows no buckle.
This is a very interesting topic. I will write more about it since I do have much to share about wet lay…
on 9th, September
Ok, cool2…im very keen to explore the installation process since i just involve with oil n gas industries..Thanks again bro!
on 12th, September
Megat,
Thank you for your visit & i really hope you can share your experience with us here in Offshoreman.net
on 16th, September
Will do..currently im working on the ONGC pipeline replacement project, India..10 pipelines to be replace till 2009..a lot of pipeline crossings involve..got 1 pipeline with 30+ crossings..
At first we proposed to used a mattress to cover the existing pipeline and grout beg for support purposes..Its been rejected due to installation point of view since divers will be needed to pump the grout beg..Then the client proposed to used slippers which is much more easier to install…
From ur point of view, which one is more costly and which one is the best method to be use?(rookie question..hehe)
on 16th, September
Are you referring to these lines :
12″ x 2.5km NLW-NLM5
6″ x 6.6km NQP-LD 6” ND
8″ x 4.7km SJ-NL
6″ x 7.6km SQ-IP
10″ x 3.4km NR1-NQD
4″ x 2.9km LC-SS1
16″ x 10.9km ST-MSP
8″ x 2.3km ND-NO
12″ x 9.4km SR-BHS
He he he… small world huh!. I’m not be able to answer your questions since i dont have much info on your project resources. But below is some possibilities:
1. Assume DPDSV is part of your resources & assume its cheaper than your Pipeline Barge… (Some DPDSV is now cost more than 8 point mooring Pipelay barge). So it is better to assign the DPDSV to INSTALL ALL the Concrete Slippers before laying pipe. I strongly believe you do have DPDSV since it is a replacement work and you have a lot of riser clamps to be installed.
2. If you dont have the DPDSV in your project, then Concrete Slippers is still the best options since it is easier to install and you dont have to mob a grout spread.
One note about India field, some times (Previous info) the client allow to lay the pipe on top of the existing pipe. After lay, you come back, lift the pipeline (With airbags) and support with grout cement. Some might not agree with these method (I personally also sees it is not safe) but experience shows in some situation client approved the above method.
Btw, is installation of flexible lines is part of your scopes?
on 16th, September
haha…almost d same…but there r few changes since then..so ur company involve in the bidding izit?..since the contractor is leighton so i dun really noe how do they want to install it n wat kind of machine do they have…i guess the slipper is d best solution for the time being..
For the flexible pipeline is also under leighton scope of work but the design is not in our scope of work since this is a special item i presumed. But we do design the i-tube for the flexible line..and i think the flexibles will be supplied by NKT flexibles…
on 16th, September
question, if we r not using the dpdsv we need to install the concrete slippers later on izit?…so we lay the pipeline first then come later for the slippers installation..
how do this dpdsv look like?..never seen it before..haha..
on 16th, September
It is not feasible to install concrete slippers after the pipeline. it is design to be installed before or during pipelay.
If you dont have the DPDSV (Dynamically Position Diving Support Vessel) as part of your resources & still want to maintain using concrete slippers, than, you may need to allocate 3-6 hrs of critical barge time to install all the slippers.
In your case : 30nos x 4 hrs = 120 hrs (5 days). So the next question that need to be asked is, IS IT WORTH to squeeze 5 days of Main work barge to install all the crossing materials…
DPDSV look like : try look at the sample vessel… i.e. Miss Marie, Miss Clementine, Lewek Toucan, or a bigger one subsea 7…
on 1st, December
Sir,
I am new Graduate ENgineer trainee in an organization in India.
As I am new…….to offshore structures and pipelaying …..kindly help me for my introduction to all these new but interesting topics.
I have learnt that ur site gives u all the information which is complex yet in a simple manner.
Kindly mail me.
on 1st, December
thank you. keep on visiting this web. will update it from time to time. since this website have been very popular, its been in the eye of my current employee. There for every writing or web content will be properly edited …