Pressur relief valve TAI milano 3000W 1

[Adido]

On 06/04/2016 we have received the PSV at workshop, and after disassembled check all their components we found the disc and nozzle totally damaged in the seating surfaces, Imperfections in seating surfaces may contribute to improper valve action in service..
Due to the remarkable damage in the seating area between the nozzle and disc ( as mentioned in the photos below) , lets’say that the PSV was Chattering (rapid opening and closing of a pressure relief valve) the operators confirm that major vibration occured at the inlet piping of this PSV. The rapid vibrations may cause misalignment, valve seat damage, and mechanical failure of valve internal and associated piping.
could you please confirm according the attached folder if tha damaged happed on Disc/Nozzle its due chattering?

 

[Danlap]

I believe "Safety Relief Engineering (PSV)" forum can provide some insight also. In my opinion the failure mode is quite decent since the wear (on both Seat and Plug) are more or less even.
For proper assessment aside from first hand (operator) witness point of view, you should incorporate technical data: Set pressure, (real) Operating pressure, back pressure, Plug and Seat (seating) material/Hard Face, how old is the valve. Those value is as minimum.
For better objective assessment, since you're mentioning chattering better to cut-cross section the Plug and Seat and see it under the microscope (by accredited metallurgical lab).
Some rule of thumb for PRV device selection. I presume yours is Conventional:
Conventional --> when built-up back pressure < allowable accumulation
Balanced Bellow --> when back pressure < 50% of relief valve set pressure (SP), advised in highly corrosive services
Pilot Operated --> when back pressure < 70% of relief valve set pressure (SP), advised when Operating Pressure is close to SP
Chattering indication is mostly related to OP close to SP, and after several "chattering occurred" it potentially lead to shifted SP (due to wear and or bolt self-loosen).
Suggest to go back to check whether this vale (if it is conventional) suitable for the application. And suggestion for maintenance/installation party to handle the valve correctly

Regards,
MR

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

 

[dbill74]

The valves in the pictures do not look like the same valve. I know they are not physically the same, but different models or from different manufacturers where the designed seating areas are different. The central peak of the two discs is the first difference I noticed. Also, to wear it down 50% so evenly with so little damage to show ; I'm having a hard time buying it.

If wear was from the relieved fluid/gas I would expect to see scratching in the seated area radiating out from the center.

If the wear was from the collision of the two surfaces as the valve opened/closed (chattered), I would expect the outer edge of the seating area to be more uneven. Perhaps even some mushrooming of the surfaces.

IMHO, you're looking in the wrong place for the solution to your problem.

I agree with Danlap, sounds like the operating point and set point are too close together. It would account for the chattering.

Regards,
Bill

 

[Adido]

Many thanks for your help, please find below the PSV specification :
Operating P around 80 barg
PSV Set pressure 93 barg ( PSV conventional )
Orifice H
Size of PSV : 2" 900 RF X 3" 150 RF
MANUFACTURER: TAI MILANO
TYPE: 3000W
OZZLE RING SETTING: -5 notch
Back pressure 4.2 barg : PSV outlet vent to HP flare
PSV piping inlet : from Gas inlet separator ( big column) to 20 meter of size 8 inch 5 meter of size 6 inch to PSV

Regards