Anyone Knowledgeable About European PED Rules?

[don1980]

My colleagues in Netherlands and Germany claim that they're not allowed to use standard pilot operated PSVs, unless they're fitted with triple-redundant pilots. Obviously, that a show-stopper!

I've referred them to the harmonized EU standards (ISO-4126-4 Pilot Operated Safety Valves) but they insist that local inspectors (Notified Body) require the triple redundancy.

My impression is that they are still applying country-specific rules (Stoomwezen, AD Merkblatt) that pre-dated PED, or possibly confusing the requirements for a CSPRS (Controled Safety Pressure Relief System) with those of a pilot PSV.

There's no requirement in ISO-4126-4 that calls for triple-redundant pilots. This documents describes the same pilot valves that we've used for years outside of Europe. Am I overlooking some in PED or are they wrong?

Thanks!

 

[MortenA]

As far as i understand it merblatt is like the english BS5500 - not the same as PED because it deals with how you build a pressure vessel - whereas the PED is a directive on how to operate pressure containing systems (including vessels)?

I have never heard that triple redundant pilot operated PSV should be a requirement - i often specify normal spring loaded valves for German and Danish applications.

Best regards

Morten

 

[gerhardl]

I am sorry that I cannot point you to the relevant rules, but sticking in the back of my mind is following:

Redundancy would be required if the volume to be protected is above a certain value, or if SIL requirements(requirement for tested dependability over a prolonged periode) or if the consequence by failure is large.

In addition: In some European countries the local inspector would be responsible for the yes or no on how a mounted assembly of mechanical components, working together in a process, satisfy the total assembly's safety.

This opens for a certain degree of local interpretation of the total process safety, and might lead to extra demands.

And not at least: Pilot operated PSVs are commonly used on Atomic Power-plants with very high safety demands, and the high-quality competitors will have redundancy as an option.

This is probably in itself enough to limit the market penetration of one without this possibillity.

 

[don1980]

Several years ago I started to educate myself on the rules that apply in EU countries because the company I'm with has a number of sites there. Since PED implementation is relatively new, I thought there would be a wealth of publications (books and articles) that summarize the rules. That turned out not to be the case......very frustrating. If anyone knows of such a reference document I'd greatly appreciate the tip.

Meanwhile, I've gotten some good information, regarding my specific question in this post, from a German who has published several articles in trade journals. From what I've pieced together, it looks like standard single-pilot POSVs are allowed in non-boiler application, but triple redundancy is necessary for steam boilers.

Prior to PED, POSVs were not approved relief devices in most EU countries. I've found that many engineers in Europe continue to practice the old country-specific rules that pre-dated PED.

Now that POSVs are allowed (ISO-4126-4) it seems like the POSV manufacturers would be jumping at this new market opportunity, but doesn't appear to be the case.