two pipeline in the same trench
two pipeline in the same trench
(OP)
Dear all,
I'm involved into design of pipeline system composed by 2 gas pipeline.
I have a small on shore section (500m) and I'm thinking about the possibility to bury both pipeline in the same trench (the route in that section is the same).
Considering that the cathodic protection system is the same for both pipeline (sacrificial anodes, same system used in offshore section) is there any problem / limitation to do that? (such as installation issue, HSE requirements)
Thank for your help.
I'm involved into design of pipeline system composed by 2 gas pipeline.
I have a small on shore section (500m) and I'm thinking about the possibility to bury both pipeline in the same trench (the route in that section is the same).
Considering that the cathodic protection system is the same for both pipeline (sacrificial anodes, same system used in offshore section) is there any problem / limitation to do that? (such as installation issue, HSE requirements)
Thank for your help.





RE: two pipeline in the same trench
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: two pipeline in the same trench
1. Twin lines fastened together might unexpectedly "rotate" about their axis (for whatever reason, apart from perfect balance etc.) in the process of trying to get them in intended perfectly level orientation the bottom, and maybe in th eworst case rotate even all the way around looking like a corkscrew?
2. Some authorities might have regulations regarding minimum spacings of pipelines for some services, perhaps based on other risks. In this regard some well-meaning authorities and individual Engineers have even gone beyond minimum standards requirements at least for other services, looking at additional issues e.g. regarding potential vulnerabilities re breaks or failures e.g. as talked about in some published papers like htt
In the absenceof minimum spacing regulations or requirements that prevent yoking the lines very close together I guess any negotiable risks of doing this might be weighed relative to any economic etc. benefits of installing close together etc.
RE: two pipeline in the same trench
Agree with BigInch. I am currently working on a project where we are bundling 3 ea high pressure gas pipelines (18", 22", and 24") and pulling them offshore through a cofferdam in a single trench.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
RE: two pipeline in the same trench
Onshore pipelines in a single trench will depend on the Owners requirements for maintenance and risk of failure.
Are both pipelines owned by the same company? This would make it easier to accept.
Stephen Argles
Land & Marine
www.landandmarine.com
RE: two pipeline in the same trench
The owner is the same for both pipelines.
Another issue for this project is that the work area is swamp one, so we could have some problem during installation.
Anyway according to your reply to investigate the possibility to land both pipelines in the same trench we have to see maintenance program and a quantity risk analysis.
RE: two pipeline in the same trench
If you're laying two pipelines at the same time, cost-wise its a no-brainer.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: two pipeline in the same trench
If the land transverse is swampy, as in mangrove/brackish water swamp, then your pipelines will have to be externally concrete coated, and/or even concrete anchor blocks build into the design, for weigh to prevent pipeline from floating.
As for spacing, I think 1 meter spacing would be a requirement for welder work space.
RE: two pipeline in the same trench
I would definately stay away from the anchor blocks. As far as the spacing, welder access is not really a consideration in bundling; those sections are welded up separatly at the push site and then "bundled" as they are pushed thru the swamp.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
RE: two pipeline in the same trench
Please clarify your reservations on anchor blocks?? Thanks!
Yes, if the pipeline is being installed by push-pull method from a pipeline launching platform into pre-excavated trench filled with water, then spacing for welder would not be an issue.
But if the pipeline is being joined and welded inside trench, as for laying normal land pipeline, then the spacing will become a necessity.
RE: two pipeline in the same trench
Anchor blocks are not recommended as they tend to impart more stress into pipeline, which requires larger anchor blocks and you go round & round. Basically in a buried pipeline the soil acts as a continuous anchor, the only issues you have are where you come above ground at a facility and in those cases it is always best to manage any movement by design of piping (guides and change in directions) and not with traditional anchor blocks. There have been some good discussions on anchor blocks and stress in previous threads, you can Google "anchor blocks" within EngTips for much more details.
Correct on the spacing. We are currently instaling 3 high pressure gas lines and in areas where it is tight, we are using 1m spacings; for the swamps and shore approach we are bundling all 3; all remaining areas have 10m spacings.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
RE: two pipeline in the same trench
I asked that because our Client's consultants have added two anchor blocks each on the swamp & subsea pipeline landfall areas. Guess the consultants are not that experienced afterall!
Can you have a look at my problem in a thread I posted earlier on regarding buckling of subsea water pipeline?
My team of engineers have come up with some interesting proposal, but I would like to see what other experienced engineers have in mind to solve the problem with laying inflexible pipes. Using the "Rintis" method cropped up, but I'm not too crazy with that approach due to the tedious work involved in the many pipeline tie-ins for 27 km long pipeline.
Cheers!
RE: two pipeline in the same trench
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: two pipeline in the same trench
The Consultant designer specified one anchor block on the Launcher side and three anchor blocks at the Receiver side to prevent pipeline movement.
RE: two pipeline in the same trench
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: two pipeline in the same trench
Agreed! But I'm sure you've come across Consultants who screwed-up in their design but won't admit to their mistakes to protect their reputation. And the Client, not knowing any better, go along with their Consultant reccommadations.
RE: two pipeline in the same trench
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: two pipeline in the same trench
Anchor block are usually necessary when it come to shore approach as water depth is shallow resulting in huge ENV loads on the pipeline. This will cause in stability to the pipeline. Anchor Block is only one of the method to counter this, others include buried the pipeline, use of high density concrete coating etc.
Anchor block is just a dead weight holding down the pipeline, therefore it come in vary shape and size depending on the designer. The term anchor block used here is different from the anchor block used (one big block casted to anchor restrict and expansion or movement to the onshore side), here Rainbowseahorse refer to a block used to prevent floating of pipeline.
Regarding the spacing the block, it will depend on the design. There is no fast rules on 1m or 10m spacing. Pretty similar to anode design, you can have more spaing if you provide bigger anode at each location. As long as the downward force from the anchor is sufficient to prevent the pipeline from upward or lateral movement.
Hope this helps.
RE: two pipeline in the same trench
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: two pipeline in the same trench
RE: two pipeline in the same trench
i work within subsea pipe lay industry for a leading contractor.
A Bundled pipeline solution is definitely the most cost effective. Use sacrificial anodes on the main line only and attach to piggyback line with spot welds (or other) at predetermined spacing to provide continuity. The current attenuation should be a derivative of normal anode calcs/code requirements and shouldnt matter if only a 500m section is onshore. (if anything, being outwith saltwater makes protection more likely)
Offshore code such as DNV-FS-101 or PD 8010 will provide further guidance. Don't use the Dutch code NEN 3650.
Have the insuring body approve your calcs.
BEng(Hons) CEng (UK) MIMECHE
RE: two pipeline in the same trench
Here is a effect weight used in swamp conditions.
Far superior to the bolt on Cement Weights