PSV Outlet Flange mismatch 1

[nasim123]

Dears
Find attached photograph for the PSV outlet mismatch. Your comments pls.
If the outlet is not matched with outlet piping, what are the issues we may face in future. Also if the inlet flange is not matched what are the issues we may face in future.

Your valuable comments are really appreciated.

 

[LittleInch]

I'm assuming the relief valve is on the right of that photo?

That is horrible, how any one has permitted that to happen is beyond comprehension. I don't even know how they have managed to do it as I can't see the nut on the far side.

Please advise size, and class rating of the two flanges.

The bore sizes probably won't match and what the bearing area for the gasket is I have no idea, but it won't be what it was designed for.

Flange sizes and ratings need to match each other otherwise you get incomplete sealing and stress developing which are not allowed for.

Where was the error here? piping size wrong, P & ID wrong, valve data sheet wrong?

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

 

[nasim123]

PSV SIZE: 2"-600# X 3"-150#

 

[LittleInch]

Doesn't really tell me much, but my only assumption is that the vendor just uses a single casting with a large flange able to be drilled to whatever anyone wants (e.g. 3" class 600?) Looks horrible though.

It's very odd, but you're drip feeding information here - please give us the full set of data, such as the valve data sheet, piping specs, whether my suspicions above is true, what the relief valve looks like with the piping off.

Turns out the diameter of the raised face bit is the same regardless of flange class, but clearly the number, size and PCD of the bolts is different.

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

 

[The Obturator]

My first reaction is, is it the valve outlet or the connecting outlet pipe flange which is wrong. Just checking the outside diameter of a 3" CL300 should provide a quick answer. The valve outlet OD should be 7.5" - Check that, then advise on the data sheet. My other question is, who installed it like that and what questions (if any) where asked at that time).

Per ISO, only the term Safety Valve is used for all overpressure eventualities regardless of design.

 

[EmmanuelTop]

Apart from the comments above, I would be seriously worried if the reduced size discharge piping can cause significantly higher backpressure on the relief valve, which will ultimately cause the PSV to under perform when needed.

If I were you, I'd issue a non-conformity note/report and request immediate actions.

Still, as LittleInch says, there is a lot of data missing here. Maybe the situation is not so bad (from the risk point of view), or maybe it is just a catastrophe waiting to happen. We can't say, based on the info provided so far.

Dejan IVANOVIC
Process Engineer, MSChE

 

[nasim123]

Dears
Find attached reply from the PSV Manufacturer. Thanks a lot for your support

" This exceed is in accordance with API Standard 526, Section 2.4. Dimensions:"
“For some valve designs, the inlet raised face height may substantially exceed the nominal dimension specified in ASME / ANSI B16.5. Consult the manufacturer for exact dimension.”

 

[The Obturator]

nasim123 The explanation from the manufacturer is fine although rather general. It is what most SRV manufacturers practice, especially the inlet nozzle/raised face comment.

However, it does not answer your fears. At the very least, check that the outlet of the SRV has the OD dimension I advised in my earlier comment. If it's larger so far so good, then check the OD of the mating outlet flange which MUST be that same dimension minimum. If you can, check the pipe/DN size also.

For whatever reason, you may have a very oversized SRV outlet flange and a "correct" mating flange.



Per ISO, only the term Safety Valve is used regardless of design.

 

[georgeverghese]

Oops, head for the nearest bomb shelter..

BTW, where are the bolt holes on the RV exit flange?

 

[don1980]

The external visual appearance looks odd - different from what one is accustomed to seeing - but there's nothing wrong and no reason to be concerned about the mechanical strength or the performance of the valve.

The odd appearance is explained in the first paragraph of Leser's response. They're starting with a single casting, which is large enough for a range of different outlet flange classes, and then machining it for the specific desired connection (raised face and bolting pattern). Although it looks odd, it has no more effect on the performance than the color of the external paint.

 

[LittleInch]

I kind of get their logic, but it still looks horrible.

One other thing though - maybe it's a trick of the camera, but those bolts don't look straight or at the same angle. A view of a flange with holes lines up to the holes in the PSV flange would be interesting and would tell you whether the holes are properly drilled.

By the look of it they've got a body which could pass for a #900 or #1500 3" flange (240 or 265mm OD), but you've got a #150 flange on it (190mm OD)

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

 

[georgeverghese]

I see where the bolt holes are now.

 

[cam72]

PSV is the last defense of the plant against any hazardous event( In the worst case scenario if Shutdown system fails , PSV is the last defense). The way outlet flange has mismatch, this is sure recipe for disaster. Please get your PSV vendor at site and let he examine this. I am sure he will ask you to replace the outlet flange.

 

[chicopee]

I wonder if the relieving capacity of the safety valve is over rated?