MW Pipe thickness definition

Is there any more info? Diameter? Pipe Specification? Weight? If you gave the outside diameter, maybe I could x-ref it to the appropriate schedule.

I would guess that MW = minimum wall thickness.

A pipe spec should always indicate the weight/ft or /meter
to prevent any confusion as to scheduled or non-scheduled pipe walls.

Thanks BigInch! I'll ask the issuer some additional information respect to this unusual spec.

Regards,

Amaro Moraes

Amaro O. Moraes
Rio de Janeiro - Brasil
aombr@yahoo.com

Hi All

I think the outside diameter is given in the original
post as 219.1mm.

regards

desertfox

Yes...uh.. it does appear to be so.

Then that would be referring to
8" Nominal D., 8.625" (219.1 mm)O.D. x Sch40 0.322" (8.18 mm) w.t. x 28.55 lbs/ft

Aren't unexplained acronyms grand? (I know one at least one CEO who is not too fond of them!!) I wonder however if there is a chance the issuer means "medium-weight" or "medium weight" etc., as opposed to heavier styles of pipes or tubes (I think I may have heard that term used at times with Schedule materials (e.g. see section 2.02 D. at If the intent is "minimum wall", I wonder additionally if this could cause some confusion (due to normal tolerances etc.) as to exactly what is meant in a schedule specification?

It seems BigInch is right. See for example, last column in table P-02B:

Thought about that one, but never heard of medium weight steel pipe, its always "Std" wt, XH, or XXH, so I went with min wall. Sometimes a yard has XH, in which case they would be ok to suggest a replacement with anything higher.

BigInch. I agree with you in the traditional, I think decades old context of steel or black iron/galvanized pipes/tubes etc. (though I guess I missed the inquirer defining this specifically as "steel").

I'm still a little fuzzy however as to exactly why the the issuer would include such an acronym along with Schedule 40 to mean "Minimum Wall" (particularly if that means the minimum thickness value number in the last column Mr. 25362 refers to) in a "pipe spec" (instead of e.g. just saying Schedule 40 or Heavier steel pipe, if that is what he really wanted)? I guess this is what I meant by possible confusion.

Nominal pipe dimensions are subjected to mill tolerances of up to about 12.5%. There are also design specific considerations such as corrosion allowance and threading that might lead you to specify a minimum wall thickness. It is probably a good idea to always spell out the desired wall thickness. Check out the attached link:
Incidentally, the pipe schedule number was not originally based directly on the pipe wall thickness. It is supposed to be given by the relation: Sch.#[≈]1000*(P/S) where P is the service pressure and S is the allowable stress (see Piping handbook, 4th edition, 1945, p. 14.) Presumably, it simplified the design of pressure piping systems by using pipes of the same schedule number without needing to do a stress calculation for each size.

Whatever. Its always infinitely better to specify the exact O.D. and wall thickness dimension, as well as unit weight. A purchasing, or any other, spec is something that should not leave anything to anyone's imagination. Goes without saying not to use abbreviations, unless they are also defined within the same spec or to a common reference.

In some older documents at my company MW refers to Mill Wrap coating. Probably doesn't apply to anything new, but if it is a spec from years ago that could be what it is refering to.