Ordering socket weld flanges 1

[KevinNZ]

What is more common when ordering socket weld flanges to get the correct ID of the socket step?
1. state the pipe sch e.g XS or SCH80
2. state the # rating e.g 3000# (to match XS pipe)

 

[LittleInch]

State the pipe nominal Od, 2",3" etc

Schedule is irrelevant.

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

 

[KevinNZ]

After I bit more digging, Per B16.5 the default ID of small SW (& WN) flanges is

class 150 - STD weight
class 300 - STD weight
class 600 - must be specified by the purchaser

So I would say order SW flanges with the pipe SCH stated.

 

[1503-44]

As a general rule, minimum info is
ITEM, NomSize, OD, WT, SMYS, MATL, Fab SPEC

Schd is optional (it is undefined for non-standard wall thicknesses.)

That will save you at least one huge, huge headache during your life.


--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

Better still just use WN flanges...

Or slip on ones if you really don't want to butt weld.

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

 

[Krausen]

You need to specify the pipe schedule bore when ordering socket weld flanges, similar (but not exactly the same) to weld neck flanges. Otherwise you'll like end up with mismatched bores/IDs btw flange & pipe. Typically socket weld flanges are used in small bore applications (<2" size). Small bore piping is often specified to be SCH80 or thicker wall. If you don't specify your socket flange bore, you'll end up with STD bore flanges socket welded to SCH80/SCH160 pipe. Less than ideal, or flat out incorrect (depending on your process).

 

[racookpe1978]

I am going to (reluctantly and rarely!) disagree with all of the above.
For ANY FLANGE, you MUST order by ALL of the following:
Nominal diameter
Material (and sometimes with certification papers)
Type of flange and Flange face: RFWN, RFSO, RFSW, FFWN, API style, etc
Class or "Pressure Rating": This value is ESSENTIAL for mating with the opposite flange.

It defines these:
the number of bolt holes,
dia of bolt holes,
bolt circle diameter,
thickness of flange and diameter of flange,
dia of raised face,
and (if present), the OD and height of "the back side" for the pipe socket weld or slip on reinforcement.​

You "never" need the Pipe ID to select a flange Class - which is the only thing defined by the pipe schedule. RFWN ? - Check me.

Now, having said that last, "pipe schedule" should usually match what the pressure rating or class of the flange will be. A 10 Sch 10 Stainless steel pipe will not need a Class 600 flange - Usually. A Class 150 flange should be reviewed very, very carefully if it is being connected to a Sch160 heavy wall pipe.

Remember the history of piping. Class ratings for flanges only came about when the higher pressure superheated steam became possible with the higher quality steel after the US Civil War and the Bessemer and Siemens steel production became reliable. Then, flange ratings were named for matching the strength of common steel at the temperature and pressure of the saturated steam inside the pipe.

 

[KevinNZ]

racookpe1978

Flange and pipe wall thickness are only loosely related. Pipe wall needs to consider corrosion allowance, flange class does not.

eg. As above the default ID for small WN and SW class 150 flanges is STD pipe, but when corrosion allowance is considered the pipe could be thicker. WN flanges must match the pipe. We always state the pipe SCH for WN flanges. (and will also for SW)

Yes, thick pipe may over stress flanges (STD pipe can too). There are rules for checking this.

 

[DekDee]

KevinNZ,
Sorry mate, I disagree with you and believe racookpe & LI are correct.
Pipe Schedule is related to the ID of the pipe so WN flange and pipes must be same schedule.
For Socket weld flanges pipe schedule is irrelevant.
A 2" Class 300 flange can accomodate Sch 40, Sch 80 & Sch 160 pipe - same OD but different ID's.
I am not an engineer so not familiar with corrosion allowance but pretty sure it will not affect the OD of the pipe - only the ID, therefore no effect on the ID of the SW flange.
Cheers,
Shane

 

[LittleInch]

The issue here is in part if anyone supplies anything more than a STD thickness SW flange, but also why would you bother?

A SW flange is as below.

So the ID 2 is basically the ID of a STD thickness pipe.
What happens if its a thinner pipe? A very small ridge which is irrelevant in terms of pressure drop and I wouldn't be pigging through one of these.

A thicker pipe? There is a small depression, again should be negligible impact, especially for the smaller sizes where SW is ore commonly used.
This is not part of the pressure containing calculation and is just part of the Raised Face.

So you CAN specify the wt / schedule of the connecting pipe for SW flanges, but unlike WN, this would seem to be not a requirement and you might find difficulty or delay or extra cost in obtaining something seen as not standard for little to no benefit. All IMHO of course.

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

 

[KevinNZ]

I agree ID of the SW step does not effect the strength of the flange or the piping. Just adds an internal bump when the pipe ID is less than the SW step ID. May also cause a mismatch of gasket IDs to flange face if the project has a mixture of SW and WN flanges.

B16.5 does require the purchaser to state the required SW flange ID for higher class and larger flanges. e.g table 8 note 7, ID SCH40/(STD) for <=10" or specified by the purchaser.

 

[LittleInch]

Dies anyone really use a SW flange beyond 2 or 3"??

A SO flange would surely be a better bet at those sizes?

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