PED needed for ASME stamped tank? 2

[mveu97]

As an OEM, we currently purchase an ASME marked tank (38 liters) for use in one of our products. We know our customers will be putting a liquid in it, pressurizing it to less than 6.9bar (generally less than 4.1 bar), and max temp of the liquid will be about 50C (ambient plant temp). However, we don't know what the liquid will be. It is up to the end user to decide. If we want to sell into Europe, does anyone know if we need PED for the system? If so, does having an ASME mark on the tank get you any closer to satisfying the PED? If we don't know what the customer is ultimately dispensing from the tank, how can we satisfy PED?

 

[JohnGP]

As the manufacturer of the system, you may need to apply the CE mark the assembly. Inclusion of a pressure vessel in the assembly means that you need to consider the PED if the maximum allowable pressure is more than 0.5 bar. There are exclusions, so you would need to check the Directive which is available online - see

http://ec.europa.eu/enterprise/pressure_equipment/ped/index_en.html

.

If CE stamping is required then you would need to specify that to the vessel fabricator. An ASME stamp will not demonstrate compliance with the PED - whether you need the vessel to have CE stamping depends on the Category that it falls into. Determining the Category is a bit tricky if you don't know the intended contents, but to cover all bases you could assume Group 1 liquid - explosive, various levels of flammable, toxic, oxidising. If there can be gas, the categorising based on Group 1 Gas will cover every possible situation, but lead to more stringent inspection requirements.

If the contents can only ever be Group 2 Liquid, then based on your vessel size and pressure, no CE marking would be required for the pressure aspects of your package. Other Directives may apply though.

There are a few ifs and buts - check the Directive though to see where you fit.

Regards,
John

 

[JohnGP]

I meant to mention that ASME has a guide for stamp holders that details what additional steps need to be taken to comply with the PED, but that's not really your concern if you are not fabricating the vessels. (Helps to be aware of what they have to go through though).

John

 

[mveu97]

Thanks for the post. I've seen the guide for ASME stamp holders. My problem is we don't fabricate the vessels and my current vendor has no interest in investigating the PED without charging me an outrageous amount of money. Perhaps changing vendors is an option.

Assuming none of the ifs and buts apply to me, could I specify that my system is only suitable for Group 2 fluids so that I wouldn't have to worry about the PED? If a customer chooses to use a Group 1 liquid, they would be responsible for reassessing the system and addressing the PED if necessary? Or is it not this simple?

Other directives do apply to our system, but I find those easier to go through and self certify.

 

[JohnGP]

Well, it's all about safety, so if the equipment is only suitable for Group 2 liquids, then that would obviously need to be clearly stated.

It would not be possible for a customer to reassess for use with a Group 1 liquid because, based on the data above, the vessel would now fall into Category I and thus require CE marking, with attendant declaration. The customer cannot do this.

So if Group 1 liquids are possible, suggest changing vessel manufacturer, otherwise limit use to Group 2 liquids.

I've just noted though that you mention that other directives apply - if any of those are covered in Article 1 Paragraph 3.6, then the vessel is excluded from the scope of the PED if only Category I. I'm not familiar with such packages, but maybe you just need a declaration of conformity to the relevant directive for the complete package in that case.

Regards,
John

 

[mveu97]

Thanks for the input. I'll dive into the directive and see what I can come up with.

 

[PVinspector]

mveu97,

Simply using a Group 2 fluid does not exempt you from the PED requirements, it just means it takes a much higher volume/pressure combination before you reach a hazard category requiring a notified body. If it is under the threshold for hazard category 1, then a recognized national standard, such as ASME, would satisfy the "sound engineering practice" requirement. The Europeans do not accept the "we don't know what the liquid will be" type of answer from the organization wanting to PED/CE mark the vessel. The liquid is part of the rating process, and if you don't know you stop, or use worst case scenario. The CE looks at any boiler or pressure vessel as being rated for service, where ASME lets you design for pressure and temperature and send it out in the world for any possible use. This may change before too many years here too. Hartford Steam Boiler has an excellent PED guide for determing the hazard category available on their website,

http://www.hsbct.com,

and the link is here.

http://www.hsbct.com/uploadedFiles/CTWeb/AllImages/PED Selection Guide 2003.pdf

 

[mveu97]

PVinspector,

Thanks for the link to the PED guide. It is very helpful. I understand about having to assume worst case senario (group 1) for my liquid. I guess I was just hoping I didn't have to go that route.

My next question is in regards to design pressure. We sell/ship the system with a 0-60psi regulator installed on the tank. So is my design pressure 60psi or would I need to assume worse case here too and assume the design pressure is the pressure of the central air supply of the plant (typically ~100psi), or worse yet, would it be the max pressure recommendation of the tank set by the tank manufacturer (190psi)? If I use 60psi as my design pressure, my PS X V is 157, keeping me in the SEP range. If I have to use 100 psi or 190psi, I'm above the 200 volume pressure limit and into a higher hazard category.

Thanks for the input/feedback.