ASME PCC-2 Wording Issues

[Zack491]

Looking at the wording of ASME PCC-2 305-3.1 (Raised Face), it states:

"Under-thickness of a raised face due to refinishing shall
be acceptable, provided the minimum finished height of
the raised face is 0.8 mm (0.031 in.)."

Does this mean that that the raised face (annular area jutting from the flange) can be taken down to a minimum of .031 inches away from the flange or that refinishing can only remove .031 inches from the original raised face height.

 

[LittleInch]

I read it as the former.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Zack491]

Yeah, Littleinch, so did I, but a peer swore up and down it meant the latter. I don't know which makes more sense. ASME B16.5 paragraph 6.3.2 states that you can actually remove the whole of the raised face part as long as the minimum flange thickness is in accordance with the standard, so that nearly aligns with the former explanation, but saying you can only remove a 1/16'' seems like a reasonable interpretation.

 

[1503-44]

I agree with LittleInch interpretation. "Height" cannot refer to removed material. If you removed the TV tower from the Empire State Building, how "high" would it be when you finished.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[LittleInch]

Well given that you only start with 2mm for class 150 & 300, it is more or less the same....

The 7mm fr class 400 and above is a bit more meaty, but the intent I think is clear. ASME PCC -2 is for repair, so it implies a certain amount of metal needs to be removed which cannot be limited to such a small amount.

You can always write in a code question and wait 9 months for a reply....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Zack491]

Yes, ax1e, it would be whatever is left of the empire state building. I agree with you.

LittleInch, why can't .031" be taken off the surface of a raised face? When you reface a flange face, isn't a minuscule amount like 1/32'' taken off to do so, or is it more than that?

 

[LittleInch]

Depends how deep the damage is. It can be 3 or 4 mm as corrosion or a dent/ gouge

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BJI]

The wording is explicit, "minimum finished height", so you can go down to 0.031". For class 150 and 300, this is a 50% reduction so it doesn't actually matter which way you look at it. The proposed revision to B16.5 and B16.47 shows the metric raised face height being corrected from 2mm to 1.6mm, consistent with industry supply and the US customary equivalents. Don't confuse the B16.5 allowance to convert a raised face flange to a flat faced flange, with the re-machining allowance for a raised face flange in PCC-2. A minimum raised face height is required to limit the gasket area and minimise the risk of metal-to-metal contact on the OD of the flange or OD of a centering ring.