The information contained in this section is based on AD Merkblatt A2 edition AD Merkbltter are guidelines satisfying the requirements for the construction of pressurized vessels contained in the PED directives. Among all other information, AD A2 contains indications for the installation and the sizing of safety valves and may be used alternatively to ISO Sizing acc. The minimal flow cross section of the safety valve must exceed the minimum one, which results from the following formulas.

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I am currently working on a project being developed for use in Germany and we need to size out the relief valves. LESER's Germany's leading relief valve manufacturer engineering handbook calls out sizing according to the AD Merkblatt and the methodologies are slightly different from everyone else.

With this service you have online access to the full texts of over one hundred AD Codes. So how does the Merkblatt fit into selling things in Europe. Adam - About years ago I launched an effort to understand the current rules in Europe. I feel like I have a pretty good understanding now, but it has been much more difficult that I thought it would be. I thought I would easily find trade journal articles that concisely explained this. I never found such a publication. For that, you need one of the harmonized standards that deal with relief application.

Harmonized standards are the new standards that have been developed with representation from all EU countries, and once finalized, each EU member country is required to adopt those standards as national standards.

A harmonized standard e. ISO , EN can be used to design relief systems which can be installed in any EU country, without that country placing additional requirement on the design. Effectively, the harmonized standards are intended to replace the old country-specific standards e. By using a harmonized standard, one is granted the automatic presumption of compliance with PED. On the PED website you can also find a list of harmonized standards. Personally, I like the application standard EN So if you bid in accordance with tis requirement i think you have two options: 1 aski if you could do the design to some other standard or 2 Do the work as you told you would unless that would be against code.

Asking the customer would be a start but this is actually a product being developed for a handful of different German customers in response to some laws being past in Germany but later something we really would like to sell all over the world. It is quite possible even if one customer accepts something the next may not. Really what I am looking to do is come up with a design that hopefully is good to use anywhere in the world but specifically anywhere in Germany.

It looks like I have been going through the same efforts that Don describes above and am finding it to be a challenge to say the least. I think at this point the better ones to talk with will be with our notified body who will be issuing us the CE mark as opposed to customers but we will see.

What I just can't understand is why are the Germans maintaining a set of standards the AD Merkblatt if they have been superseded by something new. On a side note is it worth it to purchase the actual code?

There are tons of great articles which I have been studying up on diligently. The design code is a key element of the documentation - it's one of the first things the Notified Body will want to see. The risk in not buying the code is that you might have some re-work due to something you didn't know. If you're use ISO , and plan to buy a copy, then be carefully check to see which chapters you need.

They're sold separately. Before I got what I really needed, I ended up buying a couple of chapters that I didn't need. Why do we still have national standards e. AD Merkblatt, Stoomwezen when there are pan-European standards "harmonized standards" which can be used in any country? I don't know the answer, but I think the legecy codes probably have value from a brand name perspective. AD Merkblatt was updated to make it compliant with the PED technical requirements, but it's not a harmonized standard.

That doesn't mean it can't be used. It just means that its use doesn't infer automatic PED conformity. My observation is that the transition to use of harmonized standards has been relatively slow.

It's just human nature to resist change. I think there's a generational factor too. For example, I often hear older engineers in Germany and Netherlands say that pilot valve can't be used in those countries. That statement was true before PED but it's not true now. Regardless, a lot of engineers continue to follow legecy practices even though the rules have changed.

BTW, it's easy to confuse the requirements. The CE stamp is one that the manufacturer's must obtain in oder to sell products in the EU market. Most all the global manufacturers have aquired CE certification for their products.

Obviously, that's especially true for those manufacturers like Leser which are based in Europe. Don or anyone else, I have done a little more reading on this one and I think I have a good idea of how this one all plays out especially pertaining to the sizing and selection PRVs. I was wondering what people think of my summarized thoughts here or if I am off basis?

There are 2 major laws in effect in most of the modern world. In order to sell an item in Europe it must conform to the PED and individual European countries must accept product for sale in them if they conform to the PED. On the other hand my understanding of the PED is that it is more of a legal document with general higher level requirements but leaves the actual implementation up to good engineering judgment and the end user. In addition to being the law the ASME code serves to aid the engineer in execution.

With some exceptions for example the PED does not allow for different accumulations above release point , a user actually could use the ASME calculations, and or any other country's standard formula to size out their PRV they would just need to be careful that it fit within the PED guidelines.

Indeed it would seem if my own company did the research we could create our own sound methodology to say size out a relief valve differently from other international norms as long as we could prove it safe that too would work? Would an authorized body ever sign off on such a thing? As such since the PED does not give formulas or direction on actually calculating particular sizes etc Under the category of standards one most common European recognized one is ISO , but others include the old individual country code such as the Merkblatt.

Providing a standard such as Merkblatt and or has been harmonized in other words ensured to meet all higher PED requirements the end user can actually size a valve to any standard formula of his choosing? When it comes to using a standard to work towards the PED the engineer must be careful that the standard in use is harmonized with the PED. When it actually comes to the methodology I intend to use here on our project since we are working on a product for sale in Germany I am going to see to it that we work first and foremost to the ISO while also doing our best to fit the requirements of ASME VIII at the same time, such that if our product is ever to be sold in the USA a few years later which is intended it is a smooth transition.

Is this the proper way to move forward? Applications have to be done according to an application standard, preferable a harmonized standard e. ISO , EN Refer to the comment above about formulas. I doubt that a Notified Body would sign off on that.

Adam, that formating didn't come out like I thought it would. Regardless, i think you can figure it out. I entered comments under the bullets to specefic statements in your post.

I guess where I struggle with in all of that is what does "Recommendation" mean? To me it means that it is something you are encouraged to follow but not mandatory like the law. Going forward I think it may be time to move on and just pick a path to run with on this project. Is this what you would do? Is there any risk to ignoring completely the Merkblatt for a product for sale in Germany if the is followed?

The Pressure Equipment Directive leaves open the choice of the applicable rules. In Germany, which is mostly AD regulations applied. There have been developed that are still used hesitant European harmonized standards for pressure vessel standard series EN Some API manuals are labeled "standards" e. API and some "recommended practices". So, if you're going to eventually bring this product to the US, then you'd prefer following the API sizing procedures, if that's compliant in Europe.

I don't have a clear answer, but I do know that they are still very widely used in Europe. In Germany there's a very strong bias toward following AD Merkblatt, even though it's not a harmonized standard.



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Single Market. Now available here. It naturally fulfils the conformity requirements ot the PED, but the high quality standard of the AD Code continues beyond this. In competition with other national standards and European Standard EN Pressure Equipment as well as EN Piping , which regulate the quality of pressure equipment, the German standard is very popular because of its consistent and logical form. In addition to its focus on quality, safety and conformity with the basic requirements of the Pressure Equipment Directive it is, above all, the clarity of the test results, which makes the AD Code so valuable to the user. In addition to the clear structure and high quality standards of the pressure equipment, the fact that the set of rules is available in the English language caters for the outstanding acceptance it has even outside of Germany.

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