Pilot Operated Surge Relief Valve; Hydrostatic Shell Testing 1

[NISHANT_D]

Hello All,

For pilot operated surge relief valve, hydrostatic shell testing;
does any standard specification asks for pilot testing at same pressure as main valve body shell test?
For example, if we have CL.300 pressure class valve; we will do hydro shell at 78 bar (1.5 times of rated pressure).
Do we need to test pilot also at 78 bar hydro shell pressure?
Because regular operating line pressure is 8 bar only and set pressure is 9 bar.
We considered to shell test only for main valve (without pilot mounted on main valve) at 78 bar.
At this shell testing, we will block the pilot connecting ports by mean of plug.
After shell test, we will mount pilot on main valve; and then will do seat test, set pressure test, etc..
Is my understanding is correct?

Thanks,
Nishant

 

[The Obturator]

I'm not sure for 'surge' pilot operated, but for just pilot operated pressure relief valves, the hydrostatic shell test is effectively testing the integrity of the main valve which is a casting. The pilot valve is generally of a wrought bodied construction and would not be subjected to a hydrostatic test. This is within ASME UG-136 (Production Testing).

BTW. Why are you hydrostatically testing the main valve? It would have been done by the manufacturer and certified as such with the supplied documentation.Hydrostatic testing is not normally done again post delivery unless there is an apparent defect on the casting.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[NISHANT_D]

Hi,
Thanks for your reply, it is very useful information!
I would like to ask one more query regarding form of any valve body; to be tested under hydro-shell.
If any valve body made from bar machining or forging; then also specification ask for hydro shell for it (as it is main valve body OR pressure containing / retaining part).
So in that condition, how we differ for material integrity; from casting or forging / bar machining process (for hydro shell testing requirement)?

Or do we have any another aspect or view to eliminate shell testing requirement for pilot?
In basic way of thinking; we also agreed to not to do hydro-shell test for pilot (at same pressure 78 bar which is for main valve body 78 bar).
But how to convince to customer or inspector for this?
Or this is well known practice in safety / relief valve industry?

Thanks,
Nishant

 

[The Obturator]

To answer your last query accurately, please advise the details of the subject valve (Brand and type).Also, what are your client specifications saying?

If it is a Pilot Operated Pressure-relief valve made to ASME VIII/API-526, then it needs to follow the minimum requirements within that code.

Please see attached a part extract of ASME VIII (2019) UG-136 which descries some of the required testing.

In the PRV industry, pilot bodies which are not cast, are not hydrostatically tested.




*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[NISHANT_D]

Hi,
This is pilot operated axial flow type surge relief valve.
Customer requirement for design & testing as per ISO 4126.
So applicable standard is "ISO 4126-4:2013 - Safety devices for protection against excessive pressure — Part 4: Pilot operated safety valves".
After our discussion, I came across comparison between "ISO 4126-1" & "ISO 4126-4" for hydrostatics testing.
"ISO 4126-1" asks for hydrostatic testing of valve shell; however "ISO 4126-4" asks for hydrostatic testing for "main valve shell" only.
"ISO 4126-1" is applicable for safety valve in general; "ISO 4126-1:2013 - Safety devices for protection against excessive pressure - Part 1: Safety valves".
Refer attachment for comparison.

As "ISO 4126-4" is applicable for pilot operated safety valve and here requirement is for "main valve shell" only.
So we can conclude that pilot is not required to be tested under hydro testing; along with main valve.
Only main valve hydrostatic shell testing at 1.5 rated pressure is required.

But I would like to hear from you; is my understanding correct.
What is your perspective in this.
Also if possible; you can elaborate on my earlier question for hydro test with form cast/forge.

Thanks,
Nishant

 

[The Obturator]

As already requested in my last post, please clarify the type (Brand and Type) of valve you are discussing.

I've been answering against a pilot operated pressure relief valve but you are still stating Surge relief pilot operated valve.

ISO-4126-4 Is for PRESSURE RELIEF Pilot Operated valves.



*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[NISHANT_D]

Hi,
Please refer attached cross sectional view for this pilot operated valve at Dipper_Valve_China.
These are pilot operated surge relief valve.
Hope now you have required information for brand & type of valve.
Thanks!

 

[The Obturator]

Thanks for the clarification. Unfortunately that design is most definitely not a Pilot Operated Pressure Relief Valve. ISO-4126 certainly does not apply to that design. I don't have any comment for this design.

I would suggest posting your query (with the attachment) on the 'Valve Engineering' forum.

Good Luck.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[NISHANT_D]

Ok, noted!
Thanks for your reply!

 

[don1980]

The confusion here is understandable. That is, it's understandable that one would describe this as a "pressure relief valve". It's just not a valve that's used in most pressure relief applications. Instead, it's a valve that designed for the very specific application of pressure rise due to hydraulic surge. In hydraulic surge applications the rate of pressure rise is extremely fast - much too fast for typical pressure relief valves. In these applications, a typical PRV won't open fast enough - it won't open before the damage is done. Thus the need for specially designed surge protection valves, like this one. I recall seeing a Dresser surge protection valve that's similar to this one.

My main comment here, though, is that the discussion above is still relevant to the question asked. These manufactured products are pressure tested by the manufacturer, and in this case that includes the pilot. So there's no need for you to hydro-test this valve when you hydro-test the piping. Instead, you just need to leak test the flanged connections. I understand that this flanged valve is an integral part of the piping system, but I would remove it before hydro-testing the pipe. Then re-install it, and pressure test the valve's flanged connections separately, at a lower pressure (a pressure that's within the pressure limit stated by the manufacturer).