A quick question relating to equivalence between UK, EN and US standards in relation to pipe sizes and fittings such as flanges.

Being a relative novice to the world of piping (and based in the UK) I am currently working on a project that involes putting together (stainless steel) pipe specification for a new system. In an effort to try and get up to speed I've been doing some background reading on the basics but was hoping to clarify a few areas which are giving me a bit of a headache, specifically:

1. From looking at various UK steel manufacturer's product catalogues it appears that pipes are sized according to ANSI B36.19M which uses the NPS system (and not the DN system). Although this is an American standard, am I correct in assuming this is generally the standard adopted in the UK or is there an UK BS equivalant of the ANSI code? If so why are they not mentioned in suppliers catalogues?

2. In terms of the difference between the NPS and DN system, is this simply limited to using a difference unit to measure OD? For example, looking at various tables showing pipe dimensions for a given NPS and equivalent DN e.g. 3" NPS = 80mm DN , the pipe dimensions appear eqiuivalent for all available thickness shedules. Is the European system to all intents and purposes exactly the same as the US system bar OD units?

3. Assuming that that the NPS and DN sizing systems are equivalent is it acceptable to fit a (BE EN 1092) PN rated or indeed a BS 10 flange to an ANSI sized pipe? Or are only ANSI B16.5 type flanges suitable for such pipework? Similary for other types of pipe fitting i.e. can you fit a UK/European standard item to a US standard pipe?

I'm hoping these questions aren't too daft and would welcome any advice....

Thanks,

Anthony.

Anthony,


I know you posted this question a while ago, but I am wondering if you ever got your questions answered? We're doing a design-build job right now in Malaysia and we're trying to sift through the piping system differences between metric and English. Our client wants metric design but says the piping should follow ASTM. Does this make sense? Can we specify ASTM piping systems with DN sizing?

Just hoping you can share what you found out...


Thank you!

Hi AMG / Anthony,

Some information on comparisons between US and British standards can be found here:
http://pipingdesigners.com/codes%20&%20 ... -%2022.htm

Anthony,

You asked:
"Our client wants metric design but says the piping should follow ASTM. Does this make sense? Can we specify ASTM piping systems with DN sizing?"

Yes.
We do it all the time in Europe, particularly with US owned plants in Europe.
Normally we would call up ASTM fittings in inches, but all dimensions would be in metric.