UK PSSR, Regulation 10- Imminent Danger

[Pipis118]

Hi All,
I'm interested in parties/ cases of where people have had experience around reporting a case of imminent danger to the HSEx or enforcing authority (UK)and what the outcome was.

Regulation 10 requires that where an inspection under the written scheme of examination (WSE)identifies an instance where the equipment may give rise to imminent danger if returned to service/ continued in service without certain repairs or actions taken to remove that level of risk.

I'm aware that the HSEx must be informed of the issue within 14 days of the finding and the user/ owner must be informed at the earliest opportunity before the inspector/ competent person leaves site.

An example I was given was around a relief device which was returned post overhaul, and the pop test revealed the valve lifted at 110% CDTP. An auditor stated that was a case of imminent danger to the system int eh it could be over pressurised.

My take was that it wasn't that black and white, the system was relatively new, in very good condition (on plant air duty) and had been pressure tested to 1.5 times design pressure.

If the system was 20 years old, falling apart and poorly maintained i would have had a different take.

Wondering what cases people have had in the UK. Insurance company CP's tend to report on cases of reg 10 fairly frequently but other 3rd party CP's tend to be far fewer.

Thanks in advance & hope it makes sense...

 

[CuMo]

I think you might be able to find your answer in ASME VIII-1 UG-152:

"(f) The relieving capacity of a pressure relief device for compressible fluids may be prorated at any relieving pressure greater than 1.10p"

Without being an expert in the field and briefly reading between the lines, my first thought would be that the pressure relief valve is set correctly to operate at 1.10 times the design pressure/maximum allowable pressure.

The 10% on top of the Maximum Allowable Pressure of a pressure vessel is a margin which would account for any variations in the whole system and ensure that the safety valve does not open randomly for no reason
when the vessel is operating at or close to its maximum allowable pressure.

First thing I would do is to read through ASME VIII-1 UG-150 /Overpressure protection/ and look for similar literature across different codes which have to do with pressure relief valves.
Also look for Non Mandatory Appendix PP in ASME VIII-1 : 2021 Edition.

Maybe the HSEx needs to do some reading too before making ultimate conclusions.

By default and very crudely summarised - if calculated properly, a pressure vessel has built in safety margin which is greater than 10%, but that's another science.
You can look up how diferrent design codes compare to each other - ASME VIII-1 vs PD 5500 vs EN 13445 for example. This shall give you an idea of the "built-in" design safety factors for pressure vessels.

If you can share more information about the specific case - we might be able to find some more guidance.

But if you want to get the best guidance on how to deal with your issue - contact a UK Notified Body (also could be called Approved Body such as TUV and they will best advise you.

https://www.tuv-nord.com/uk/en/home/

 

[Pipis118]

Hi CuMo,
Thanks for the reply. I wasn't holding out much hope of a quality response so appreciate the time and thought.
I agree with your comments around factors of safety built in to pressure equipment. I work for an inspection body but never worked for the insurance type bodies who seem to be a bit more free-issuing of regulation 10 notices under the PSSR, rather than the "our side" who operate in a very different manner, probably demonstrating more thorough ways off working under the regs.

Hopeful to get some more communication either from client side or CP side but i'll not hold my breathe.
Thanks once more...

 

[goutam_freelance]

Very cogent response above.

A small update, now-a-days the overpressure protection is guided by ASME Section XIII.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[The Obturator]

Pipis118 If it has been reported that the Pressure-relief Valve opened 10% above its CDTP, then that is cause for alarm.

A Pressure-relief Valve will have a tolerance for the set pressure (the pressure the valve starts to open. CDTP - is the test bench pressure - Cold Differential Test Pressure (taking into account back pressure and operational temperature which can't be replicated on a standard test bench).

Typically the tolerance (per ASME XIII) is +/- 2 PSIG for set pressures up to 70 PSIG and +/- 3% for set pressures above 70 PSIG.

It was correct for the auditor to reject the valve. It should not go back in service until it is rectified by a competent person.

The 10% discussed above, relates to the overpressure the valve requires to go into full lift during a vessel overpressure event. It is not a safety margin (!!!).

In basic terms;- The Pressure-relief Valve is typically set to open at MAWP (100). It will open at 100 and attain full lift and flowing capacity at 110 (ie., 10% overpressure).

Pressure-relief Valves are the last line of overpressure defence protecting life and property. You need to be intimately knowledgeable on this subject.

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

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

 

[georgeverghese]

Agreed, the auditor needs to take a chill pill