WELDING BRACKETS TO VALVE FLANGES - ANY CODE REQTS?

[Bambie]

At our plant, 1/2"nps bypass valves are 'stayed' with brackets fillet welded to the body flanges of their 14"nps boiler feedwater valves.

Fatigue failures of the bracket welds has called for beefing up the bracket configuration and weld design to avoid resonance.

The legitimacy of the attachment weld (which has not failed) is being questioned.

The alternative is to use a body/bonnet stud for this purpose, however this could lead to gasket leaks.

Are there any large valve manufacturers that approve this practice?

Are there any specific conditions on type, size and length of weld or pre and post heat treating?

 

[pennpiper]

Bambie,
Can you provide a picture or two of the specific situation?

Sometimes its possible to do all the right things and still get bad results

 

[Bambie]

Pennpiper,

I can get those on Monday. In the meantime I've attached a sketch.

A 4" x 2" x 1/4" plate is welded to the edge of the body/bonnet flange with a fillet weld along the 4" edge.
The 4" edge is slightly contoured to the radius of the large flange.
The plate has two 1/2" holes to which the bypass valve or it's actuator can be bolted.

Being attached to the body side of the flanged connection allows valve bonnet removal without disturbing the bypass valve that is bolted to the bracket.

 

[Bambie]

Pennpiper,

Here is a picture of a welded and bolted lug installation as requested.

 

[pennpiper]

I want to thank you for the picture however it did not help me as much as I had hoped.
I now suggest, as long as you discussed this need with the Maintenance Department and got their approval then it must be good to go.

Sometimes its possible to do all the right things and still get bad results

 

[LittleInch]

I've not seen much on this in the codes and looks more like something it doesn't specifically allow, but doesn't specifically forbid.

I would much prefer to use bolted connections and then weld onto that.

Section 2.1.6 of ASME B 16.34 states that the welding requirements for the main body are not applicable to ...lifting lugs,...

So there appears nothing to directly stop you, but equally nothing giving you any requirements or specifically allowing it. So it looks like a welding procedure / fillet weld testing issue.

A lot seems to depend on the manufacturer - in my place I would say no as it is not of value to me, but you can always ask.



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

 

[Bambie]

LittleInch,

I am interested to know your reasons for "much" preferring to use a bolted connection as the attachment to the main valve.