Torque and Chrome

we are experiencing pipe settlement on a submarine pipeline newly constructed. how to fix it?

We constructed a submarine intake and discharge pipeline (1.2m dia.) that is using a flange to flange connection for a cooling system for a small power plant. It is trenched but the bolts are loosening (we were not advised to use a torque wrench), because the seabed based on soils investigation was found to be silty sand to poorly graded sand plus there are no sinker or thrust blocks on the joint connections. Also the pipelines which crosses a road way onshore was only backfilled without any protection or culvert, heavy trucks about 30 tons in weight frequently pass this road. How do we fix this? Is there a design deficiency?

Public Comments

1. You almost certainly have design or installation deficiencies on the settling portion of the pipeline. On the road crossing, if the pipeline is sufficiently deep and has sufficient strength to resist loads from trucks at road crossing, as specified by the applicable code, then it is ok. My guess is that the road crossing could go either way. You also have a major problem. My guess is that it will probably cost you about 20% to 50% of what the original pipeline installation cost to fix it. Who pays for the repairs is also going to be an issue. It could be you, the engineering firm if they made design errors, or the installation contractor if their work was faulty. You should consider getting a good consulting pipeline engineer and a good attorney. Give them your contract and have them review the contract and the site to see if they meet the original contract requirements. Good chance you are looking at $10k for initial opinions, maybe $100k or more for court suit. If you have a strong contract and the pipeline does not meet spec, the contractor will likely fix it at minimal or no cost (tho they will try to get you to pay as much as possible) to avoid also having to pay court costs. We had a similar case. The design was OK, but the contractor's work did not meet specs. However, the contractor was smarter than our county commisioners, or perhaps had an arrangment with them. They had supposedly verbally approved deficient work, to keep the project on schedule, and kept no records. So, the county paid the origional contractor lots more to fix their original work. Weak original contracts and/or customer acceptance at various milestones combined with poor recordkeeping of approvals often lets the contractor off the hook, and the customer has to pay for the repairs. Next time, write a good contract that requires the pipeline meet a specified code and be fit for service. Use caution in approvals - you want the contractor and engineering firm to remain responsible for meeting specs and fitness for purpose, even after you approve milestones. Then, at least you won't have to pay to fix it (if your engineering firm and contractor are solvent or have insurance). Good luck.