Consumable Inserts ANSI B31.3

[DaiLG]

Hi All,

I am attempting to weld an orifice plate between 2 sections of pipe.

Under section 328.2 of ANSI B31.3 it states that a weld procedure qualified without the use of a backing ring is also qualified with the use of a backing ring with single welded butt joints.

Here's my question. Can I interpret the orifice plate as being a backing ring in this instance OR do I need to create a new weld procedure?

Any help would be greatly appreciated.

BR
Dai

 

[LittleInch]

Can you please sketch a londitudinal section of what you're trying to do. Is there some reason why you can't use normal flanges? currently as described, my answer would be no, it's not a backing ring, but I'm not sure I follow what you're trying to do.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[DaiLG]

Here's a quick pencil sketch showing the plate and pipe arrangement.

Its for a multistage assembly so mounting between flanges is not an option unfortunately .

BR
Dai

 

[DekDee]

DaiLG,
No problem at all.
The Orifice plate (as drawn) is "backing" and that is all that is required.
Forget about the "backing ring" - as long as you have some sort of backing - eg. permanent (steel), temporary (ceramic) or weld metal then you are complying with the requirements for backing.
Regards,
DD

 

[LittleInch]

Ah, That makes a lot of sense now and I tend to agree with DekDee, you can weld it like that, but still seems very odd - e.g. how will anyone know it's there once you've moved on? Orifice plates between flanges are:
a) removable to check their size, remove debris on one side and
b) also have a tell tale stub sticking out to remind everyone there's a orifice plate there and what it's size is.

It would also seem to have the potential to move and crack the root weld or just dissapear down the pipe. How will you keep it in place while welding or is that small lip at the root deliberate?

I'd like to know how the process engineer thought it was going to be installed or are you just trying to make something work that wasn't properly designed?? Not sure what you mean by a multi stage assembly, but I would only recomend that you consider the future operations and maintenence and also weld on a tell tale to show there's something in the line restricting flow

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[DaiLG]

Thanks both, the helps appreciated.

FYI Little Inch it is intended for use in construction of a 'multistage restriction orifice assembly' and yes the small 'lip' is deliberate. Basically its a number of restriction orifice plates mounted in series to reduce pressure in very high pressure lines. If you tap it into Google all will become clear.

Again thanks for the help both.

BR
Dai

 

[LittleInch]

Ahhhh Ok, so it's a purpose made spool piece not just installed in a piece of pipe, which is what we started with. Looked them up and see what you mean, but still don't lile the look of them, but that's more personal preference I guess. I'd prefer to see small spools with the orifice plate in the centre of the spool being fillet welded on both sides then stitch the small spools together. There are still lots of amintence issues here, but I guess you're just the fabricator, not the piping designer.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[LittleInch]

In fact the rototherm one looks like what I just described....

http://www.rototherm.co.uk/multistage.html

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way