European directive 97/23/EC and Maximum Allowable Pressure (PS term) 6

[sheiko]

Dear all,

In Europe, the directive 97/23/EC applies to the design, manufacture and conformity assessment of pressure equipment and assemblies with a maximum allowable pressure PS greater than 0,5 bar.

They define PS in the article 1 - section 2.3 as: "Maximum allowable pressure PS means the maximum pressure for which the equipment is designed, as specified by the manufacturer. It is defined at a location specified by the manufacturer. This must be the location of connection of protective and/or limiting devices or the top of equipment or if not appropriate any point specified."

I was wondering if you could tell me if it corresponds to the design pressure or not?

For info:

In annexe I - Section 2.2.3.b, this directive states: "the calculation pressures must not be less than the maximum allowable pressures and take into account static head and dynamic fluid pressures and the decomposition of unstable fluids. Where a vessel is separated into individual pressure-containing chambers, the partition wall must be designed on the basis of the highest possible chamber pressure relative to the lowest pressure possible in the adjoining chamber"

Could you please also tell me if this calculation pressure corresponds to the MAWP or not?

Kind regards.


"We don't believe things because they are true, things are true because we believe them."

 

[BrianPetersen]

What is it that is unclear? I think the definitions given are defining what they are talking about, much more precisely than the generic terms that you are trying to equate them to.

 

[sheiko]

OK, so do you mean they (PS, MAWP, calculation pressure and design pressure) are all different?

"We don't believe things because they are true, things are true because we believe them."

 

[sheiko]

As i am a junior chemical process engineer, i would like to have some mechanical experts clarifications on this subject.

"We don't believe things because they are true, things are true because we believe them."

 

[prex]

The absolute value of the design pressure Pd for normal operating load cases shall not be smaller than the absolute value of PS.

so the two are in practice the same thing, except that you may occasionally have more than one couple of design pressure-temperature pressure for a vessel.
The calculation pressure is the design pressure plus the static head at the location of the calculated component, plus other minor terms.
MAWP is a concept that afaik is not present in the european code. This is an option that the purchaser may choose under ASME: instead of using the pressure required by the process, the vessel is stamped and designed with the maximum allowable pressure (at the design temperature) for vessel. EN13445 has a concept of maximum permissible pressure that's defined only for single components and is used for some calculations required by the code (e.g. for fatigue calculations)

prex

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[HenryItaly]

Hy,
MAWP & MAP are not Psmax.
In PED (Pressure Equipment DIrective) and its Harmonized code (EN13445 and EN13480) as in other european codes don't exist the concept of MAWP & MAP.
Psmax is the design pressure of the vessel. The vessel can't work at a pressure major of Psmax.
I suggest you to buy BS EN 13445.

By
from Florence

 

[HamishMcTavish]

Which country in Europe are you based? Directives are transposed into National Law - in the UK this directive is captured by the Pressure Equipment Regulations (amendment) 2002 and the Pressure Systems Safety Regulations 2000.

Check out the following for summary:

http://www.berr.gov.uk/files/file11284.pdf

As HenryItaly suggests design to code - i would suggest PD5500: 2009 as it provides the basis of vessel design and manufacture for compliance with the Pressure Equipment Directive

Regards, HM

No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[HenryItaly]

Hy
the law that in Europe all the states MUST respect is the Directive 97/23/EC (PED).
Before PED all states of the UE had their mandatory national regolamentation.
After PED is born a new and very very innovative Code: EN 13445 (infact new ASME VIII Div.II ed 2007 has take a lot from new EN).
But, you know here in Europe every state think be better than other's, so all states of the UE has revised their old codes to give conformity to PED.
So are borned "new" codes as:
Germany => AD 2000
England => PD 5500
French => CODAPE 2000
Italy => VSR + CTI
etc.

Those codes are realy very very similar.....and i doesn't understand why we (european) use only the very innovative code EN 13445 for all europe (as un the USA ASME)....

But I think i'm dreming....

EN 13445 is borned on the request of the European Commission to have an "Harmonized Code" with PED, so if you wont a clarification on PED read it.

Bye bye

 

[HamishMcTavish]

Henry,

sorry, i don't want to get all pedantic on you but a directive is binding, as to the RESULT to be achieved, upon each member State to which it is addressed, but the MEANS by which this is achieved is up to the various national authorities. The member states are bound to implement the directive into their national laws within specified timescales.

However, it was held (in Francovich and Bonifaci v. Italy (Case-6 and Case-9/90), [1991] E.C.R. I-5357) that if a Member State failed to implement a Directive by the deadline for doing so, or its implementing provisions were incompatible with provisions of the Directive that are unconditional and sufficiently precise to be given effect to directly, then any national provision must give way to EC law.

So depending on which member state the OP is in will affect which national legislation they have to comply with. There may be "local" requirements which are over and above those of the PED.

Regards, HM




No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[btrueblood]

Stars for Henry and Mac, the member state codes are hard to find at times for us Yanks; knowing the numbers helps a lot.

That said...if one designs a vessel meeting the requirements as outlined in 97/23/EC, but adhering to the "sound engineering practice" of a local code (e.g. ASME B&PV code, or a typical member state code), is it fairly safe to say that the CE cert. will be accepted by other member states? OR must one show compliance to each member state's pressure vessel code in order to sell one's equipment within that state? And, if that is the case, what good did the PED do?

 

[HenryItaly]

Hamish,
of course each state may have its particular regolation, but PED is MANDATORY and the Essential Safety Requirements (ERS) of Annex 1 must be respected.
After 2002 England, Italy, French, Germany, Spain, etc. must design and build with PED in mind to certify CE the equipments.

This is the why every old National code has been admendemed: for give conformity to PED.

However, if someelse want use ASME in PED he can, but must to have in mind that he must change some ASME requirement for give conformity to PED (as for example Hydraulic test, etc.)

I'm sorry for my English....

Ciao

from Florence

 

[HenryItaly]

Hy btruedblood
for PED in every state of UE you can use every PED admended code:
AD 2000, PD 5500, CODAPE 2000, VSR+CTI, etc or to use the PED harmonised EN13445.
You have to certify CE by means of one Notify Body like, for example:
Bureau Veritas
Lloyd's Register
ISPESL
Apave
TUV
etc

Good night

 

[HamishMcTavish]

Hey Henry - don't apologise for your English, it's WAY better than my non-existent Italian!!

I don't want to sidetrack the post with any more talk about mechanisms of EU legislation but just briefly...

A Directive must be translated into member states national law within a set timescale. If it isn't then the courts look to the wording of the directive for the legal position.

A Regulation on the other hand is a legislative act of the European Union which becomes immediately enforceable as law in all member states simultaneously.

It seems to me that you think the PED is actually a regulation since you use the term "mandatory".

As far as the OP goes - if they comply with the national legislation of the country they are working within then they should automatically comply with the PED. The various national standards will have been adjusted so that users can show compliance with local legislation (and by extension the PED)

Certainly if they use any of the standards which you have quoted they will be able to demonstrate compliance.

Apologies if this seems pedantic - i did a law diploma a long time back and old habits die hard!

Kind regards, HM




No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[sheiko]

Thanks all,

I am in France so the code is CODAP 2005 (Div.1 and Div.2).

Now back to my original question and if my understanding is correct:

1/ The acronym MAWP does not exist in PED. Why? it looks however close to the PS in definition. what do you think?

2/ "design Pressure" is from the user (usually the process engineer).

3/ PS (maximum allowable pressure) is from the manufacturer. It is higher or equal to the design pressure.

However, i have been told that, "Manufacturer", in PED terms, does not have to be the company that actually fabricates the equipment and, in every project, it has to be decided who will take the PED role of "manufacturer". This can be the operating company, the EPCM contractor, a Project Management Consultant or the actual equipment supplier, or any other that takes the responsibility for compliance with PED.

COuld you please tell me in which part is it mentionned in the PED?

Plus,

4/ what is maximum permissible pressure?

5/ what is PSmax?

"We don't believe things because they are true, things are true because we believe them."

 

[HamishMcTavish]

Btrueblood - if you design to a harmonised code then they should all comply with the PED see the following for how the directive has been implemented in the various countries in the EU.

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

sheiko, you could look at the following for the definition of manufacturer

http://ec.europa.eu/enterprise/newapproach/legislation/guide/document/1999_1282_en.pdf

is the english version

http://ec.europa.eu/enterprise/newapproach/legislation/guide/document/guidepublicfr.pdf

is the french version

My understanding is that if you design to a code which is harmonised with the PED then you should be ok. So design to the French code and use its definitions of MAWP and design pressure.

Regards, HM

No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[btrueblood]

No apologies for language (I don't speak very good Italian either) nor for pedantics necessary, this discussion of the PED was quite informative, thanks again to all.

 

[JohnGP]

Hamish,
I've sometimes been accused of being pedantic, hence have a small issue with your use of "harmonised". Harmonised standards give a presumption of conformity with directives - i.e use of EN 13445 mentioned above by HenryItaly provides direct conformity with the PED. Other national codes can be used nonetheless to demonstrate a design/fabrication complies with the requirements of the PED - we have many vessels designed and fabricated in accordance with ASME VIII, and CE marked per the PED.

btrueblood,
ASME had a guide for stamp holders that detailed what needed to be done to comply with the PED. As noted above ASME VIII can be used for design and fabrication for vessels subject to PED. The documentation requirements and level of involvement of a Notified Body depends on the equipment category - "sound engineering practice" being the lowest defined (and not requiring, or allowing, a CE mark by the way).

sheiko,
Apologies for continuing with the hijacking of your thread. In response to your questions (and reiterating some of the points made by prex and HenryItaly),

1/ I don't know why MAWP doesn't exist in the PED - as far as I know the particular term is unique to ASME. The term PS in the PED appears to me to be more like design pressure, as evidenced by its definition in 2.3 of Article 1. I can see though it could be argued differently.

2/ "Design Pressure" is usually specified by the user, but can be by the manufacturer (as for say a standard range of pressure equipment).

3/ The maximum allowable pressure PS, in terms of the PED, is the "maximum pressure for which the equipment is designed…", normally specified at the top of the vessel. I have not actually used EN 13445, but it specifies that the design pressure must not be less than this (I know, I know, my head is in a spin about this as well). I think generally PS will equal "design pressure".

I think you have moved on to Assemblies. Someone joining various equipment items into an assembly would be the manufacturer of that assembly, and is responsible for applying the CE mark if required. To do that, the assembly must be assessed against the requirements of relevant directives, and all individual components would necessarily have to comply. Any vessels and piping in the assembly would have to be assessed against the PED and so you would need the documentation from the manufacturers or suppliers of such items in order to be able to demonstrate compliance of the whole assembly. See Article 10 paragraph 2 of the PED.

4/ I don't think "maximum permissible pressure' is defined in the PED. But in EN13445 at least it is the "pressure obtained with the analysis thickness at the calculation temperature for a given component from the design by formulae". So, same as MAWP it seems.

5/ I haven't seen "PSmax", but in EN 13445 "Pmax" is defined as "maximum permissible pressure".
Maybe those terms are in CODAP as well?

Hope I haven't confused the issue too much, but that's my limited understanding anyway.

Regards,
John

 

[sheiko]

Thank you all,

To sum up, the answers of my original post are:

- Does the "maximum allowable pressure (PS)" defined in EN 13445, correspond to the "design pressure" defined in ASME code? - Yes

- Does the "calculation pressure" defined in EN 13445, correspond to the "maximum allowable working pressure (MAWP)" defined in the ASME code? - No

The calculation pressure is the design pressure plus the static head at the location of the calculated component, plus other minor terms. The equivalent of MAWP is rather the "Maximum permissible pressure (Pmax)" in EN 13445.



"We don't believe things because they are true, things are true because we believe them."