Schedule ##S designation

[rmw]

When a schedule number has an "S" behind it, it indicates that it is a Stainless (or is it other alloy as well) pipe. An example would be 4" Schedule 10S indicates a 4 inch schedule 10 stainless pipe.

What and/or where is the standard that states that the "S" designator signifies Stainless (or is it more than stainless?)

I have to make the case in order to establish an internal standard that the "S" designator indicates stainless but I need an authoritative source.

rmw

 

[JJPellin]

The "S" does not always indicate stainless. Schedule XS is a designation for extra strong and XXS is extra, extra strong. Enter "Pipe Schedule XXS Extra Strong" into ask.com and you will get plenty of references for the stainless designation.

Johnny Pellin

 

[JohnGP]

In my (quite old) copy of ASME B36.19, it is stated in the Scope that the "S" suffix in the Schedule Number is used to differentiate B36.19M pipe from B36.10M pipe, as there were some wall thickness differences between the two standards for some of the sizes.

 

[vpl]

According to Crane Technical Paper 210 Flow of Fluids, (the Pipe Data in Appendix B towards the end) the S stands for stainless when used behind a schedule number. So while iron pipe can be XS or XXS, it would not be designated Schedule 80S. When you take the Schedule number "80" and add an "S", you're indicating stainless.

Patricia Lougheed

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[JLSeagull]

ASME B36.19M
1 Scope
The wall thicknesses for NPS 14 through 22, inclusive (DN 350–550, inclusive), of Schedule 10S; NPS 12 (DN
300) of Schedule 40S; and NPS 10 and 12 (DN 250 and 300) of Schedule 80S are not the same as those of ASME B36.10M. The suffix “S” in the schedule number is used to differentiate B36.19M (stainless steel) pipe from B36.10M(carbon steel) pipe. ASME B36.10M includes other pipe thicknesses that are also commercially available with stainless steel material.

I inserted (carbon steel) and (stainless steel). Otherwise this reflects the phrasing in the ASME B16.39 scope.

 

[JohnGP]

Yes, like I said. The thing I didn't realise was that the "S" designation applied only to pipe to the B36.19 standard and not SS pipe to B36.10 - I just took it to apply to all SS pipe.

 

[racookpe1978]

To add a related question then, do the original "schedule 40, schedule 80 ..) designations relate to the pipe pressures back in the days of cast iron pipes?

The 150 pound, 300 pound designations in the 1942 Crane catalog I have do match with the fitting pressure ratings for saturated steam.

 

[JohnGP]

Yes, derivation of schedules seems to go back to the cast iron days, see here

http://en.wikipedia.org/wiki/Nominal_Pipe_Size

- includes some discussion of pipe schedules.