A860 & A694 vs MSS SP75 & SP44 1

[Krausen]

All,
I've gone back & forth on how best to specify & order high yield steel piping buttweld fittings & flanges. I primarily work under B31.4 & API 1104 for welding procedures. H For grade B material, we commonly will specify ASTM A234WPB with B16.9 for fittings & A105 with B16.5 for flanges. This is fairly standard across the pipeline industry from my experience.

However, for high yield material it's a different story. We used to specify the appropriate MSS SP75 grade with B16.9 for fittings & MSS SP44 grade with B16.5 for flanges. In an effort to be consistent with how we specify grade B material we've since switched to specifying the ASTM A860 or A694 high yield steel with the ASME/ANSI dimensional standard. From some of the previous posts I've read on this site, it appears the most common way is to specify to MSS standards instead. Can anyone explain why?

Also, if you do specify a high yield flange to both MSS SP44 & B16.5, what pressure-temperature rating do you follow since MSS SP44 states its flanges are full rated up to 250 F I believe whereas B16.5 flanges typically derate beyond 100 F for common materials?

Thank you for your input

 

[BigInch]

Ya. It always irks me to see the those big elaborate specs for something that's been relatively simple to order since the last 30 years.

If you spec B16.5, you get to use the B16.5 temperature allowable. If you spec MSS SP-44, you get to use the SP-44 temperature allowable.

MSS SP-44 was written to address the need for high pressure flanges and SP-75 hi press fittings, that were developed specifically for high pressure, pipeline use. It allows the material's high yield stress at lower temperatures than B16.5, up to 250[°]F, then derates more quickly above 250[°], as based on pipeline industry experience.

B16.5 is primarily a dimensional spec that at one time only addressed low carbon steel and sizes up to 24" for typical low grade, carbon steel, plant piping which was no longer suitable for high pressure, high strength, large diameters being used in pipelining at the time.

To specify a high yield strength, large diameter, pipeline flange, all you really (normally) need to do is write

36" Diameter,
Flange,
RF x WN (might be something like RTJ x WN, etc.)
0.375" wall thickness,
Bore 35.250" (that is redundant, but not harmful)
ANSI#600,
MSS SP-44,
F65
Design Code B31.8
Design Factor 0.60
Beveled 30[°] for welding

It may also be helpful to specify the wall and grade of the adjoining pipe.

The mfgr may select the (any) base material as referenced within MSS SP-44 that matches the yield strength grade that you specify, unless you choose to specify a particular material, in which case he will use that one and probably charge you more for having to read your spec.

Include any additional requirements, such as Charpy Test Temperature, Taper bored to some other ID, etc. as applicable to your specific requirements.

 

[Krausen]

Thanks BigInch. I think I'm going back to specifying MSS standards again. It just seems more straight forward & there is history to back it up. You also have the benefit of higher pressure-temp ratings up to 250 F. The only thing I'm uncertain of now is if I should change my grade B material to MSS since they make F36 flanges to MSS SP44 apparently also. This would make everything consistent, but I've never come across F36 MSS SP44 flanges before.

 

[BigInch]

MSS pipeline flange temperatures match the B31.4 and 8 pipeline code's no-derated pressure limit (the same 250[°]F), so it is beneficial to use the MMS spec. for all pipeline projects, especially for size >24", high yield strength grades, or when you need allowable pressures > the published temperature limits of B16.5. For example, you could still have ANSI#600 pressures to 100 Barg when up to 100[°]C, not the 90 Barg limit in B16.5

I too have always used A105 and 234 WBP For Grade B flanges and fittings to B16.5 or 9 when size is <= 24", as they nearly all are in plant piping, and when temperatures are below the B16.5 & .9 limits. That's normally not a problem, hi temp pipelines have been few in the past, but their use is becoming more frequent with the more unusual oils coming to market these days. If I had a hot pipeline, I would be tempted to use MSS SP 44 F36 too.

They have a number of other useful standards as well,

http://msshq.org/Store/Results.cfm?category=6

 

[tharrison]

What about spec'ing orifice flanges?

B16.5 is to MSS SP-44
as B16.36 is to .... ?

In other words,
B16.36 refers back to B16.5 for materials, but what is the best/easiest way to specify orifice flanges to go with the higher grade pipe?
For regular non-orifice flanges, MSS SP-44 provides a way to use the higher strength material (like A694 GR. XX), but as far as I can tell, MSS SP-44 doesn't cover orifice flanges.

Any suggestions?

 

[BigInch]

Orifice flanges are flanges that happen to hold an orifice plate between them.

Order whatever flanges you want and machine bore the taps, if you want flange taps, or alternatively tap only the pipe.

Plate

http://www2.emersonprocess.com/en-u...-pressure-flowmeter/pages/orifice-plates.aspx

OR
Use an orifice fitting,

http://www2.emersonprocess.com/en-u...e-flowmeter/pages/senior-orifice-fitting.aspx