i am sure if you start trying to weld on the pump casing, you just bought an unwarranteed pump. I would think it is ridiculous to weld the drain and vent plugs, how will the casing be vented if their is entrapped air in the fluid? What safety issue arises from a threaded plug that is on all pumps ever made that this safety group is afraid of?
On Oct 15, 2008, at 7:26 AM, M. Engineer wrote:
> I need your opinion for the subject of seal welding of pump castÂ
> iron screwed connections such as drain plug. This subject wasÂ
> raised from safety group, however, I don¢t recall in any API orÂ
> other codes that it mandates seal welding of such screwedÂ
> connections at centrifugal pump casing. The problem here is weldingÂ
> to cast iron body proven extremely difficult and can impose otherÂ
> problem. I need your feedback if such screwed connections (e.g.Â
> drain connection) mandated to be seal welded in hydrocarbon services
Sounds like a knee-jerk reaction from your safety people. The ASME pressure vessel and piping codes prohibit welding on materials with a carbon content exceeding 0.35%. And for good reason
While cast iron is theoretically weldable, you stand a good chance of serious damage to the pump housing because the material is so brittle. One teeny crack is all it takes, especially in a highly cyclic load environment like a pump. I think a seal weld on cast iron is more of a hazard than a leak, because you can clean up after a leak in a few minutes. Cleaning up after a ruptured housing takes a lot longer, especially if the rupture put someone in the hospital. You've also got heat distortion issues which might distort the connection and make it impossible to unscrew. And you'll almost certainly want to unscrew that drain plug at some point.
Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, SpotsylvaniaÂ1864)
[Non-text portions of this message have been removed] Received on Wed Oct 15 16:10:00 2008
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