Metric Bolts for use with B16.5 & B16.47 flanges 1

[hawksy]

I have a project with requirements to use metric bolting. The project has piping (ASME B31.3) and pressure vessels (ASME BPVC Section VIII, Div I). Can I select metric bolting that has similar diameter or are calculations required?

 

[deanc]

Think you will need calcs. per Sec VIII Div.1 Appendix 2 and 16.3.

Review U-4 before you start. Stress values? See SF-568M in SecII Part A (hint-pg.1623)

 

[unclesyd]

One caveat in swapping fasteners is don't get too far off with clearances in the bolt holes, in other words size to size as close as possible.

 

[MJCronin]

hawk,

Nope....if you are constructing a piping system in accordance with ASME B31.3, then you must use english bolt/stud sizes.

ASME B31.3 references and requires the usage of ASME B16.5 which requires a certain english size of stud/bolt for each flange size.

-MJC

 

[hawksy]

I have never used metric bolting in the past but, I currently have a customer that is requesting that we use ASME B16.5 flanges with metric bolting. They are not accepting a deviation. The customer is over seas and has stated that they have purchased systems similar to this before (from other companies) and have never had a problem with this. What should I tell them?

 

[deanc]

MJCronin

Don't know if I agree with you. There is a Code Case on this item which I will list later.

There are a number of manufactuers who do this. Unclesyd is correct about sizing. You may want to drill out holes and up size for metric under U-2(g).

That is why you must do a justifcation for this. I believe
this will be possiable.

 

[deanc]

MJCronin

Sorry---need to slow down and backup. If I had read your post better I would of seen it was only B31.3,while I was stuck on SecVIII.

However,I still do not agree,there must be a"work around"
on this. There are too many requests for metric not to be. It will of course need to be justified and they may not be B16.5 flanges when finished.

I have seen some documents---let me find them and I will list.

 

[unclesyd]

This is the only reference I could find concerning the use of a Metric or UN thread form. As long as you keep them as a unit and calculate them as such the flange will never know the difference. The units used for calculations are undefined until you define them.

ASME A193/A A193/M-06a

1.6 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.

The use different thread forms in PV's and piping has been around for years. We had four nitric plants built in the 50's that had Whitworth threads on wet end and UN threads on the hot side. Two very expensive rotary vacuum filters designed to ASME with Metric bolting.

 

[deanc]

Sorry about being slow to get back.

There is no reason why metric would not be acceptable,if you design and plan for it.

Your material requirements address it and also most sections of the Code.

For instance see SecVIII,U-2(g),Table U-3,U-4,Appendix 33,and Appendix GG.

Get your ducks in a row,talk to your AIA,and go for it.