RangerBill
Petroleum
A client is looking for our definitive guidance regarding the suitability of fitting an NPT threaded 1" vent valve assembly into a blind flange at the end of a subsea hydrocarbon spool. The flange is duplex the valve 316. The spool is located under a wellhead flowbase.
Failure of the NPT thread where the nipple on the valve screws into the blind flange would result in a loss of containment requiring diver intervention to isolate/replace. The main line isolation valves adjacent are normally open and manual. The well would have to be shut-in and the flowline isolated at a remote manifold to fully isolate. The whole piping and valve spool with which this assembly is fitted is ‘dumped’ under a wellhead structure and protected with flexible concrete mats.
I personally wouldn't touch an NPT threaded valve into a blind flange with a bargepole, but a 'cheap' client is determined to get away with it. I think its too mechanically vulnerable from damage and a ¼ turn away from being unscrewed. We ourselves proposed a flanged double block and bleed assembly integral with the blind, though it is being avoided by the 'cheap' client on cost.
Can anyone remember a section in any relevant piping design code, which covers a scenario such as this?
Failure of the NPT thread where the nipple on the valve screws into the blind flange would result in a loss of containment requiring diver intervention to isolate/replace. The main line isolation valves adjacent are normally open and manual. The well would have to be shut-in and the flowline isolated at a remote manifold to fully isolate. The whole piping and valve spool with which this assembly is fitted is ‘dumped’ under a wellhead structure and protected with flexible concrete mats.
I personally wouldn't touch an NPT threaded valve into a blind flange with a bargepole, but a 'cheap' client is determined to get away with it. I think its too mechanically vulnerable from damage and a ¼ turn away from being unscrewed. We ourselves proposed a flanged double block and bleed assembly integral with the blind, though it is being avoided by the 'cheap' client on cost.
Can anyone remember a section in any relevant piping design code, which covers a scenario such as this?