Re: selection of welding consumables

From: <Christopher>
Date: Thu Sep 20 2007 - 20:02:00 EDT

On Sep 20, 2007, at 11:50 AM, rao marneni wrote:

> dear friends, some time of controle valve's yoke broken in an
> accident in my project. can any
> one help in selection of welding electrodes. valve grade is SA 216
> WCB. thickness of yoke is
> around 90mm. can any one help me in this welding procedure. there
> is no chance prepare
> edge.

You can get some general help from the Lincoln Electric web site with process variables and consumables. <http://www.lincolnelectric.com/>

I really need to say this. It doesn't sound like you know too much about what you're getting into, and you'd be very well advised to leave this up to a professional. I can't tell you how many failures I've seen from botched weld repairs--between material mismatches, heat distortion and metallurgical damage, mostly it just makes things worse. Probably best to torch the thing into fragments now and save yourself a lot of trouble sweeping up after it breaks again in the same place.

The valve may be made from SA 216, but there's no reason to assume that the yoke is made from the same thing. SA-216 is a casting specification, which makes sense for the valve body, but not necessarily for the rest of it. If the yoke isn't a pressure part, it could be anything, including a material which isn't weldable. A 90 mm thick part isn't unweldable, but you'd be putting a helluva lot of molten weld metal into the repair and when that metal cools it'll distorts the part and make it almost unrecognizable. Depending on the material the heat will also change the metallurgy, particularly if the original part were heat treated for strength. You would do very well to get a new yoke from the manufacturer.

Finally, the choice of consumables depends a great deal on the welding process. The type of welding equipment matters, because it affects the current and voltage among other things you need to control. You should already have a weld procedure in place anyway that mentions the electrode specification. If you don't have a procedure in place, with welders qualified to use it, you shouldn't mess with this.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=IaivxhUZVMMiyAHLukE9NnaLPS2LD1h0DI7dSZgi2Ovi5tFSL-YHutm8DSo0UH_kBu6AGlwk740hwcyD">chrisw@skypoint.com</a> | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania

1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a> Received on Thu Sep 20 20:02:00 2007