For any incident within the plant boundaries, the pipeline inventory needs to be isolated from the plant, in order to prevent escalation of the incident. These valves are called “emergency shutdown valves”, and form part of the pipeline.
1. ESD in Onshore : ESD valves should be located at each end of the pipeline, and on the incoming and outgoing sections at any plant en route, such as compressor or pumping stations. The valves should be located in the non-hazardous area e,g, close to the plant fences.
2. ESD in Offshore : An ESD valve shall be located at the top of each riser connected to the offshore platform. It should be placed below the platform lower deck level for protection against topside incidents.
3. For pipelines connected to manned offshore complexes, and in addition to the top of riser ESD valve, a subsea ESD valve located on seabed close to the platform may be considered. Subsea valves should be justified by a quantitative risk assessment.
4. The distance of the subsea ESD valve from the platform should be derived such that the combined risk associated with the platform activities and the pipeline fluid inventory between the valve and the platform is minimised.
ESD valves should not incorporate bypass arrangements. Pressure balancing, if required prior to valve opening, should be done using the operational valves located immediately upstream or downstream of the ESD valve.