Best way to weld this cover/head for pump
Best way to weld this cover/head for pump
(OP)
Hello,
I work for a pump repair shop and recently we received a cover for pump (BB2 type pump).The service is HF acid and therefore I think we have this issues. The pump service pressure is 800 psi and temp is 95F. Cover base material is carbon steel with monel welding on registers. Initially, the welding was sticking out and we decided to machine off 0.020" from monel welding and weld on top on it. After machining, and during welding, we found that there are hydrocarbon pockets and we couldnt weld it. We machined more and remove all monel and now we will be welding on carbon steel with nickel butter pass and then monel weld. Here are few pictures. Please provide your feedback on what would be the best way to weld this? Would baking this part at 700F help? What else we can do better? Is baking necessary and will help?
pre-machining

Unable to weld

I work for a pump repair shop and recently we received a cover for pump (BB2 type pump).The service is HF acid and therefore I think we have this issues. The pump service pressure is 800 psi and temp is 95F. Cover base material is carbon steel with monel welding on registers. Initially, the welding was sticking out and we decided to machine off 0.020" from monel welding and weld on top on it. After machining, and during welding, we found that there are hydrocarbon pockets and we couldnt weld it. We machined more and remove all monel and now we will be welding on carbon steel with nickel butter pass and then monel weld. Here are few pictures. Please provide your feedback on what would be the best way to weld this? Would baking this part at 700F help? What else we can do better? Is baking necessary and will help?
pre-machining

Unable to weld


RE: Best way to weld this cover/head for pump
The Nickel Development Institute or NiDI has a great selection of publications.
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You absolutely need to remove all contamination (that is generally true for welding on high alloy materials). I would start with acetone. The middle picture appears to show the remnants of a fillet weld (is this the dissimilar joint?). The crevice below the root is going to be a potential big problem for cleaning. Just heating to a high temperature might leave a residue that is problematic for welding. Excavate deeper if necessary.
I'm not sure what the last picture is showing, other than non-metal.
"Everyone is entitled to their own opinions, but they are not entitled to their own facts."
RE: Best way to weld this cover/head for pump
Remove the existing weld that appears to be "unsound" until you have sound base metal on which to deposit "good" weld.
Depending on the chemistry and thickness of the carbon steel, you may have to preheat before welding.
Best regards - Al
RE: Best way to weld this cover/head for pump
So I wouldn't focus too much to start on "sound" material.
Also, I doubt you're going to find a definitive answer on the internet. Better retain someone local who can take all secondary information into account.
"Carbon steel" can mean all kinds of things, especially in this case. Preheat is almost a certainty, how much exactly is hard to tell without further investigation.
RE: Best way to weld this cover/head for pump
It appears they are attempting to weld over a cracked weld that has been contaminated with who knows what.
Best regards - Al
RE: Best way to weld this cover/head for pump
Please supply all the serial numbers of aircraft made with this philosophy so that I can warn my flying friends and colleagues...
"Everyone is entitled to their own opinions, but they are not entitled to their own facts."
RE: Best way to weld this cover/head for pump
I don't know if it is correct for connecting machine parts , but seems the steel design standards always suggest to match the weld strength to the metal's yield strength to preserve ductile behavior. But in no way a build-in defect shall be tolerated, if it is avoidable. Please comment, if I am wrong.
RE: Best way to weld this cover/head for pump
As for "built in defect", you might consider what the effect of the faying surface where two members meet has on the integrity of a fillet or the unfused root of a partial joint penetration groove weld. We allow the use of both types of weld details for static loads and try to avoid them where there are cyclic loads.
Best regards - Al
RE: Best way to weld this cover/head for pump
The third shot, showing a rough machined radius with spalls revealing the parent steel material or just incomplete machining next to end of a circumferential crack really has me scratching my head as to its location.
Do you have the body of the pump? What is it made of, and are the pilot bores cut directly in the parent material?
Is it possible the "monel welding on registers" was done as a repair, with the weld material chosen to resist crevice corrosion or some such ?
I picture the pilots being for location, so not very structural, at all. In that case the task of the weld repair is to not provide crevices, although I'm guessing there have to be chamfers on pump body pilots, forming Crevice Las Vegas right beside the monel treated rings.
RE: Best way to weld this cover/head for pump
I have another important question. After welding and after PWHT, We checked the hardness on welded and non-welded surfaces and we are getting 20 RC-30 RC values.
Is this acceptable hardness range? I am not sure why hardness was check on first place. Is there any industrial procedure or welding procedure that states acceptable hardness ranges for monel weld on carbon steel base material??
RE: Best way to weld this cover/head for pump
what are the engineering and quality requirements?
was there a authorize repair procedure from engineering?
was there a schedule from a weld engineer.
what are the part engineering heat treat hardness requirements?
you don't guess, and asking here for internet to tell you is foolish.
how do you heat treat a part and not know the requirements!
what is the part fit, form or function?
hopefully this is not safety issue? where it will endanger some ones life.
RE: Best way to weld this cover/head for pump
https://www.thefabricator.com/thewelder/article/arcwelding/cleaning-material-with-brake-cleaner-before-welding-a-risky-move-that-can-turn-deadly