orifice pltes 3

[merlin000]

We are putting a orifice plate between 2 x RF WNF,s B16.5 is it normal practice to grind the welds flush at the orifice plates. This is on a Terminal.

 

[JLSeagull]

What kind of orifice plates - for what purpose?
Why modify the flanges?
ASME B16.36 covers orifice flanges for flow measurement.

 

[merlin000]

They are just class 150 restriction orifice plates. it says in local spec to grind the welds flush internaly on the Flanges.Normal WNF RF not orifice Flanges.We will not touch or modify the flanges. Is this normal practice to flush the welds off Internaly.

 

[JLSeagull]

The welds that you are inquiring about appear to be the weld neck flange at the welded connection with the upstream or downstream piping. API MPMS Chapter 14.3.2 addresses the roughness and tolerences for a flow element installation.

I would not apply API MPMS tolerances for a restriction orifice. Also, no appropriate standard comes to mind to reference if a client demands compliance with API MPMS or similar ASME or ISO standard for a restriction orifice.

 

[pennpiper]

Merlin000,
You left some information out so we must give general answers.

Questions:
1, What is the purpose of this Flange/Orifice Plate installation (Flow Measurement or Flow Restriction)?

2, What is the pipe size for this question?

Answers:
1a, If the purpose is for true Flow Measurement then yes the common practice is to grind the inside of the circumferential weld smooth.

1b, If the purpose is for purely the Restriction of Flow then No you do not need to grind these welds.

2a, If you are in a Flow Measurement situation, with Pipe sizes 3" through 10" the smoothness is far more important than maybe a 24".

 

[JohnGP]

merlin000 says it's "just class 150 restriction orifice plates". RO plates generally have a hole size significantly smaller than the pipe size, so grinding the WN flange welds will have no effect, or benefit.

 

[merlin000]

Thanks for all your answers guys. A great help.

 

[merlin000]

It is only 2 inch pipe. There are no orifice flanges just a orifice plate.normal WNF. RF so i think it is restriction flow only.