Following a query raised at MTM No.17 in Aberdeen in September 2015, Arild Fossa of Expro (Leader of the NORSOK D-007 revision team) has provided this response:
Is there any good reason for the SSV (C.8) having 7 second closure time, while the STT (C.2) has 5 second on its actuator? Our internal operating company timing requirement is 10 second for both.
The 5 second requirement on the STT (item C.2) is a historic experience number verified over the years since NORSOK D-SR-007 rev. 1 was issued in 1996. The service companies (Expro, Halliburton and Schlumberger) all reported that it has never been a problem testing the valve closure that quick.
The SSV requirement (item C.8) at 7 seconds is a new requirement in D-007 revision 2.It is based on the normal third party classification company acceptance criteria.
It was the revision committee’s intention to harmonize these two criteria and change them both to 7 seconds, but this was a typo that slipped through the review. However, for practical purposes this is not an issue since the classification companies use 7 seconds or slower timings.
Note: NORSOK D-007 covers generally valves up to nominal 4” size here. For large valves, the closure time should be as per valve manufacturers guidelines. This since reaction forces vs. bolt strength can dictate slower reaction times.