Normally the marine antipollution authorities (also B31.4 for liquid hydrocarbon pipelines; you didn't mention what contents or design codes are) require block valves on both sides of significant water courses.  In some cases a check valve may be used downstream.  In keeping with the intent of polution mitigation, with a liquid pipeline you should have some kind of valve on land and near the shoreline to prevent backflows to sea if a washout or anchor drag damages the pipeline.

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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/

Thank you for your reply. Just to be sure I understand that the block valve are necessary if we have a liquid pipeline.

My pipeline is a gas one and reference code for design is BSPD8010.

Don't know that code, but since the shore zone is an area more prone to damage than most, I think it would be a good place to put a valve nearby in any case.  A check valve alone might prevent a lot of lost gas should there be a line break in the surf zone.

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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/

The need for a valve and its location will come from the Major Accident Prevention document that should be under production during design to comply with the UK Pipelines Safety Regulations.  UK HSE look to DNV-OS-F101 as an example standard and good practice for offshore pipelines wherein Appendix F Requirements For Shore Approach And Onshore Sections suggests that the first valve onshore is "often an emergency shut down valve (ESDV)".  EN 14161 also indicates that a 'section isolation valve' should be installed at the end of the pipeline.

Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
 

Good advice, although for EN14161 I don't get how it would be the "end" of the pipeline.

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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/

Where the 'end' is would be for the designer to define I guess.  It could be where there is a transition to a service not covered by that standard, e.g. transport/distribution.

Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
 

that still sounds like somewhere in the middle.

**********************
"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/