DIN 2673 versus EN 1092-1 type 04-34

[Piline]

Dear engineers,
For a couple of years I visited many times your “EngTips” site for a fresh look on piping issues. I am a design engineer on retirement and spent about 35 years in engineering firms and construction sites. Nowadays I spent some times to study subjects related to piping I never had the time for that. Such a subject is the comparison between ASME en EuroNorm flanges (see Flanges comparison).

There are four columns for the geometric comparison between ASME and EN. In the 3rd and 4th column are the lap joints and stub ends. The EN has more of these items to choice. Type 02 & 35 consist of ISO and metric design (metric version is not shown in 4th column). Why some many designs in the EN norm? So I asked myself the next question:” if I don't have a pipe spec, which flange would I choice for a good design”?

So, I did study all the facets of flanges and makes a report (in Dutch) of it. My approach has been of a qualitative nature to still get results on the pro & cons in the engineerings phase and operational phase.
This report is 14 pages long and unfortunately is takes to much time for me (now this moment) to translate it.

Some points I will highlight:
-In DIN period (from 1928 to 2007) only the PN10 range of type 04-34 consist,
-After 2001 (harmonization DIN to EuroNorm) PN16 to PN40 are added,
-Some of the dimensions of the welding neck flange are taken over,
-There are no re-calculations made on the new type 04-34.
-There is only one firm in Europe who is manufactured this type (I did sent the report to them and hope on response).


One of the thinks I discovered was the integrity of flange type 04-34 of the EN 1092-1(see fig.A&B).

In fig.A you can see the old DIN flange assembly. Fig.B gives the new release of PN10 range. You can see the decrease in contact surface. If the tolerances are “counteracting”, the ring of 3 mm will be 2 mm. I don't have to tell what happens if there is some misalignment or water hammer in the system.
The same goes for the whole diameter PN10 range:
-DN15 to DN200, ± 30% less contact surface
-DN250 to DN600,± 60% less contact surface
Because in the old DIN 2673 only the PN10 range existed there is no comparison for the PN16 etc.

I am aware of this EuroNorm treatise in the ASME bastion.

So, and now finally my question to you: Do I have a point if my conclusion is that this construction is a bad design?

 

[XL83NL]

Hi there, and welcome fellow Dutchman! Good to see you joined ET.

Although I’ve never looked at these EN flanges before, I’ve used several EN 1092-1 flanges for the pipe specs I’ve made over the years. I’d say the answer to your question is yes, it’s a bad design. There are some crazy sections in EN 1092-1 if you start digging, which is what you’ve done too, for good reason.
Have you looked at the appendix in EN that, if I’m not mistaken, covers some history? Also, you could try to contact the CEN/TC committee responsible for EN flanges and ask for their opinion.

PS: translating is quite easy nowadays with the built in translator in recent MSWord versions, it does the job quite well.

Huub
- You never get what you expect, you only get what you inspect.

 

[Piline]

Thanks for your response XL83NL,

Flanges are the most important part in a piping system, therefore I will take a closer look on some types and in response of your reply.

Flange data in historical perspective.
Carl Sagam once said “you have to know the past to understand the present”. In other words, if you can link facts, then the answer is already there.

Taken from the introduction alinea in BS-EN 1092-1 (2007),
Major changes against edition 2001:
-flanges PN160, PN250, PN320 and PN400 have been introduced;
-further collar types have been introduced;
-materials have been updated.
Re-calculation acc EN 1591-1 for,
-type 11, 05, 01, 02-32, 02-33;
-type 35, 36, 37;
-type 21, 04-34 have not been re-calculated acc EN 1591-1;
-type 12, 13 have been adjusted to the results for type 11.

Before year 2001 all the type numbers where DIN codes.

Just more original data,

Some time ago I did a little research of the weights of ASME flanges in comparison with DIN flanges. In most cases the ASME flanges are heavier. There was an article (can't find it anymore) on internet about the 2nd war period in Germany about shortage of raw materials. They needed it for the war industry. In the period 1936 – 1943 there were some changes in the DIN codes. I can not verify the decrease in weights in that period, mine oldest source is the “Deutscher flanschenkatalog” from 1967. It could be a minor explanation for the differences in weights. On the other hand, I know that the CODES are normative.

CEN/TC 74
A standard or norm is established when there is a need from the business community for a new product standard, in this case a flange. If three quarters of the ISO member countries agree, it becomes official.

https://www.envirotech-online.com/a...opean-cen-and-international-iso-standards/176

But the business community must take the initiative with an adjustment and/or new product. I am a private citizen, not a business, so I have mine doubts whether my proposal will be considered.
An other point is, if this type is not used in business, it will never come to light. I have searched in ± 120 CS pipe specs and nowhere is this type 04-34 used. Therefore I sent my report to Hertecant Flanges in Belgium because they have, as only European manufacturer?, type 04-34 in their program. I have asked them how they deal with this, because they should make this disclosure at the CEN/TC 74. This moment of writing I did not receive an answer from Hertecant.


How to reduce the number of flanges in the EN 1092-1?

ASME B16.9 9 types of flange components
EN1092-1 16 types of flange components

I have split the types by material and pressure range,

Proposal;
Type 33 to combine with type 37
Type 35M to combine with type 35 ISO
Type 02M to combine with type 04
Type 04-34 to re-design

The committee CEN/TC 74 could have reduced the number of types with a little more imagination, this benefits the right choice and stock management in the business community. Because there is a tendency in process technology to work with increasingly higher temperatures so that chemical processes run better, the welding neck is now the only candidate for this. It is possible that a better flange concept will be developed in the near future that offers more advantages compared to the welding neck flange. Maybe this will be the new type 15 or type 22? A more balanced EN 1092-1 standard improves choice (like the ASME B16.9).
Is this delusion, fantasy or possible?

I tried to find an European site where I can discuss these issues but nothing there, so I went to Eng-Tips where the ASME dominates, witch is also familiar in Europe.

Thanks for getting this far.