ESDV Closing Speed
ESDV Closing Speed
(OP)
This has come up a few times in the past but I think it's worth throwing it back out for consideration. Does anyone know of a criteria or spec for Emergency Shutdown Valve (ESDV) closing speed? I'm aware of the concerns with respect to hydraulic surge if the valve is located on a liquid line.
However, for the most part, our work involves ESD valves in gas service. Any ideas on closing speed criteria?
However, for the most part, our work involves ESD valves in gas service. Any ideas on closing speed criteria?





RE: ESDV Closing Speed
The surge relief valve could be operated in parallel with the ESD valve in order to redirect the stream flow in a closed loop circuit until a pressure decay is detected. It is understood that a transient regime analysis have to be conducted in order to properly size a surge relief valve capable to handle the usteady flow conditions.
RE: ESDV Closing Speed
Think about a 10" line filled with liquid propane and you shut the valve slow enough not to cause hammer (or you have a relief valve around the ESD). How much energy escapes downstream in BTU's? Then look at your 10" line with nat gas closeing just as slow, how many BTUs of fuel would be added to the fire?
RE: ESDV Closing Speed
After that, depending on shutdown mode, we either block and hold, or dump the plant to 100 Psig in less than 15 minutes. I guess I could do a quick calc for the volume of gas moved through the ESD valve as it starts to close and assume a linear Cv reduction over a 20-30 second period. Given the volume of gas and propane contained in the plant, I'm not sure it's going to amount to very much.
RE: ESDV Closing Speed
At one site, they did the test. It only cost them about $50,000. The next year, the cost was even more. Here is what happened. All the lube oil from the compressors was laying in the headers. When they blew the gas down, all that lube oil sprayed the landowners property, cost to cleanup, $50,000. The next year they did the same thing. This time the landowner was going to sue and cancle the surface lease. I was called in and we installed 1" RO under all the 8" ball valves and piped them to a KO drum and a large single vent.
The next year it took closer to 15 minutes, but there was no oil slick.
A couple of years later I was at a different station on the day they were doing the same test. My personal car was covered with oil and the hyway outside the fence was so slick, I spun out. They had to have the road shutdown until they steam cleaned it. Needless to say, in went the RO's.
RE: ESDV Closing Speed
Best regards
Morten
RE: ESDV Closing Speed
RE: ESDV Closing Speed
RE: ESDV Closing Speed
Best regards
Morten
PS: most valves are smaller than 45 - so a 24" closing in 24 secs would comply - but could have a larger surge than a 45 sec closing time
Best regards
Morten
RE: ESDV Closing Speed
The paragraph that mentions the 45 second requirement is in Appendix C - Support Systems. The paragraph begins on page 65, C.2.1.4 Supply and Response. The last sentence on page 65 continues on page 66 with the 45 second requirement.
"The time it takes for any safety device (e.g. PSH, BSL, ESD station, etc.) to effect component or platform shutdown should not exceed4 5 seconds. To achieve this response, consideration should be given to pneumatic line sizes, safety device bleed port size and the use of auxiliary quick bleed devices. Pneumatic lines that supply and bleed should be sized for optimum bleed conditions. Because of volume and flow characteristics a line that is either too large or too small will require excessive time to bleed."
The next sentence applies an obsolete API Recommended Practice 550 to be used as a guide when designing instrument and control systems. Instead the paragraph should reference 551-554, etc.
RE: ESDV Closing Speed
But latest 14C is form 2003?
Anyway - its a fine number
Best regards
RE: ESDV Closing Speed
Most valves will require quick exhausts to dump this much air quickly, but we'll test and record closing times as part of the commissioning process and I'll put a note in the manual requiring yearly confirmation of closing times.