Riser emergency shut down valve (ESDV) leakage assessment


OG status:
Fully open
Author unit / section:
Target audience:
All OSD Inspectors, SI3A and SI3B
Version No:


To describe how HSE assesses the acceptability of riser emergency shutdown valve (ESDV) leakage rates. This SPC replaces SPC/Tech/OSD/26 which has been withdrawn.

Legal requirements

Duty holders are not required to meet fixed criteria for maximum riser ESDV leakage rates. The goal setting regulatory regime allows maximum rates to be set according to the installation's ability to safely control the hazards produced by such a leak.

The Pipeline Safety Regulation 1996 (PSR)1 states that an "emergency shut-down valve" means a valve which is capable of adequately blocking the flow of fluid within the pipeline at the point at which it is incorporated. In the absence of a definition, "adequate" is taken to mean sufficient for a particular purpose.

The guidance to PSR (Schedule 3 and regulation 19) indicates that an ESDV should be capable of stopping the flow of fluid within the pipeline. However, minor internal leakage past the ESDV may be accepted providing it does not represent a threat to safety. The rate of leakage should be based on the installation's ability to control safely the hazards produced by such a leak.

The duty holder assessment must be consequence based and can take some mitigation systems into account.

Mitigation measures that can be credited

Mitigation measures that cannot be credited

To be credited for mitigation, all systems should be designed to operate automatically in a fail-safe manner, be capable of remaining effective in an emergency and must be demonstrated to meet their performance standards.

Specialist assessment

OSD's fire and explosion specialist inspectors (OSD 3.2) will assess analysis methodologies used by all duty holders. Where Inspectors find that ESDV leakage has risen above levels previously considered acceptable in accordance with the guidance to SI 1029 revoked (1sm3/min gas or 6kg/min oil) the issue can be forwarded to OSD 3.2 for assessment.

Hazard analysis issues

The following issues are expected to be included in the consequence based hazard analysis of ESDV leakage.



A guide to the Pipelines Safety Regulations 1996 Guidance on Regulations L82 HSE Books 1996 ISBN 978 0 7176 1182 9

Further information

Further information can be obtained from OSD3.2 Fire, Explosion and Risk Assessment 0151 951 3144

Updated 2020-12-28