ASME Flange Thickness Tolerance - Standards vs Reality
ASME Flange Thickness Tolerance - Standards vs Reality
(OP)
Hi Eng-tips community,
This is my first post here so hopefully it's nice and concise.
I'm currently doing some R&D for a couple of new products, one of them being a tool to measure the thickness' of ASME Flanges on site,
The thickness values (c) in the ASME 16.5 standards are taken as the minimum and usually to 0.1mm.
I know the ASME 16.5 standard also states that the thickness of flanges can have a tolerance of -0/+3.2mm, this seems very high, basically rendering such a tool non-practical, as there is sometimes only a 1.6mm difference between these flange thicknesses.
My question is, without going through and physically measuring batches, is this tolerance stated in the standard actually regularly translated into reality? Since I'm guessing these tolerances in 16.5 were taken when manufacturing techniques were much less advanced than today. Surely its in the interest of many manufacturers to get their tolerances lower than those in the standard (saving on material costs etc).
Usually I'd just drop the project, but having spent a lot of time on it and this issue of variation of flange thickness for raised face ASME flanges also affects other R&D projects where F-F space is an issue (so a potential F-F tolerance of 6.4mm is not ideal).
Any clarification on the feasibility and actual current manufacturing tolerances for ASME/PN flanges would be much appreciated.
This is my first post here so hopefully it's nice and concise.
I'm currently doing some R&D for a couple of new products, one of them being a tool to measure the thickness' of ASME Flanges on site,
The thickness values (c) in the ASME 16.5 standards are taken as the minimum and usually to 0.1mm.
I know the ASME 16.5 standard also states that the thickness of flanges can have a tolerance of -0/+3.2mm, this seems very high, basically rendering such a tool non-practical, as there is sometimes only a 1.6mm difference between these flange thicknesses.
My question is, without going through and physically measuring batches, is this tolerance stated in the standard actually regularly translated into reality? Since I'm guessing these tolerances in 16.5 were taken when manufacturing techniques were much less advanced than today. Surely its in the interest of many manufacturers to get their tolerances lower than those in the standard (saving on material costs etc).
Usually I'd just drop the project, but having spent a lot of time on it and this issue of variation of flange thickness for raised face ASME flanges also affects other R&D projects where F-F space is an issue (so a potential F-F tolerance of 6.4mm is not ideal).
Any clarification on the feasibility and actual current manufacturing tolerances for ASME/PN flanges would be much appreciated.





RE: ASME Flange Thickness Tolerance - Standards vs Reality
The flange thickness impacts the bolt length, especially with the high tolerance from B16.5 you mentioned. What I did was measure a few dozen flanges for the typical range we use (1/2"-8") and check how much they were off. I dont recall the outcome, but the exercise was short, simple and useful, and gave me the info I needed. Maybe you can do this as well.
RE: ASME Flange Thickness Tolerance - Standards vs Reality
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: ASME Flange Thickness Tolerance - Standards vs Reality
Cheers Xl83NL! We came to the same conclusion, I'm going to take some calipers out on site for my next few surveys and note them down.
Still its strange that manufacturers and suppliers don't include these in their quality checks, maybe they would just rather not release such info.
SnTMan, I agree, seems to me any manufacturer would want to keep their material costs down for items produced in large volumes like this, so would most likely work to a lower tolerance, I'm guessing the standards tolerances were from when manufacturing techniques were not as good as they are now, and have been kept to cover manufacturers liability.
The -0/+3.2mm would make these sections overlap in size, as some are only around 2mm difference.. Here's hoping the actual on site checks will produce a tolerance lower than this and make the project actually viable.
RE: ASME Flange Thickness Tolerance - Standards vs Reality
The actual tol largely depends on the size of the flange and the fabrication method.
When you have a large number of forged blanks which costs more, having them all a little too thick or having a few of them scraped for being too thin?
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: ASME Flange Thickness Tolerance - Standards vs Reality
I'm still missing something....
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: ASME Flange Thickness Tolerance - Standards vs Reality
“Bolt length calculations based on worst case tolerances led to a revision of tabulated lengths”.
Regards
r6155
RE: ASME Flange Thickness Tolerance - Standards vs Reality
Yes, machining techniques are more advanced than they used to be. I could (and would) leave the design thickness at +3mm over spec, and my machine shop would never be out of the +3.2mm tolerance. .0079" is child's play to those guys.
RE: ASME Flange Thickness Tolerance - Standards vs Reality