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Customer brought me a pump to repair. Had a leaky shaft seal they thought they could replace it themselves. Couldn't get the cast iron impeller off so they forced it with a shaft puller and broke it. What a drongo.This is a job for EzyTigWire.Cleaned the flat surfaces with flap disc,Clamped the broken piece in position and tacked the ends. Grooved the cracked joint with dremel and die grinder. Two pass weld with full peno.Heard a dreaded kachink and thought that's a fail. Turned out an invisible crack opened up in a different location. Grooved that out and welded up. All good, no more kachink.Gonna give the pump a birthday. Cleanup, bearings, shaft seal, repaint.That's the way I do it. No torch, no braze, no nickel rod, no mig, no pre or post heat.
Reply:It spins 3450 RPM or 2875 if 50 HZ. You want perfect balance on that part.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:Cool. Please let us know if it works out.
Reply:Yer I'm just gonna grind it flat and go with that.
Reply:Dang it. All right all right I'll get it balanced.
Reply:Great job.Now to machine and balance.Dave
Originally Posted by Woznme
Customer brought me a pump to repair. Had a leaky shaft seal they thought they could replace it themselves. Couldn't get the cast iron impeller off so they forced it with a shaft puller and broke it. What a drongo.This is a job for EzyTigWire.Cleaned the flat surfaces with flap disc,Clamped the broken piece in position and tacked the ends. Grooved the cracked joint with dremel and die grinder. Two pass weld with full peno.Heard a dreaded kachink and thought that's a fail. Turned out an invisible crack opened up in a different location. Grooved that out and welded up. All good, no more kachink.Gonna give the pump a birthday. Cleanup, bearings, shaft seal, repaint.That's the way I do it. No torch, no braze, no nickel rod, no mig, no pre or post heat.
Reply:Gosh. Busting the lip of the impeller with a jaw puller! Who would have thought
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Reply:This is a job for EzyTigWire.Cleaned the flat surfaces with flap disc,Clamped the broken piece in position and tacked the ends. Grooved the cracked joint with dremel and die grinder. Two pass weld with full peno....That's the way I do it. No torch, no braze, no nickel rod, no mig, no pre or post heat.
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Originally Posted by Oldiron2
I'm not familiar with your particular TIG wire and wonder who makes it, what it contains, and where you get it? Any links?
Reply:The good news about most cast iron most parts are made out of Class 25 or less. But that bad too as you find more problems welding the cast iron. I would use a four jaw chuck and TIR of less than 0.00,5". Most 3 jaw chuck when new is 0.000,5" but in time the 3 jaw drop to 0.005" or more. Then if possible balance the shaft then the rotor on shaft. Dave
Originally Posted by Oldiron2
I recall reading a thread or two about using MIG with special wire for such repairs and believe the wire name or supplier was linked. I'm not familiar with your particular TIG wire and wonder who makes it, what it contains, and where you get it? Any links?Can't even remember the last important CI repair I did; might have been the handle of the old Champion Post Drill, which I stick welded. Little jobs, less interesting ones, are more easily forgotten though, particularly when there's so much other that needs to be remembered these days.
Reply:Just heating cast iron to red hot and letting it air cool changes the metallurgy to a complex mixture of the original iron and hard and brittle iron carbide and Martensite that make up brittle white iron that has very little tensile strength. How it is welded and what it is welded with wont change this fact. This is from the chapter on cast iron from Metals and How to Weld them by Lincoln Electric. That is why the weldment cracked upon cooling the first time. You will notice how hard it is when you try to grind it smooth. Whether the result is strong enough is unknown but I would feel much better about it if it was the pump housing and not the impeller that is rotating at 3K RPM. There is a tremendous amount of energy in that impeller when it is running.Last edited by Bradley256; 1 Day Ago at 10:36 AM.
Reply:The thing we have to worry about when we complete those “simple” repairs. At least it broke from misuse and not inservice stress. So I would guess the repair is sound. How fast does it spin? Does it fit inside a sleeve? Machining is important, before installation. S
Reply:It does run at 2950rpm. It's what's called a DIN pump, cheap Chinese construction with coarse tolerances which is why I was considering not balancing the impeller. I've installed and commissioned plenty of these bad boys over the years. One even was delivered with the impeller rubbing the pump housing. Had to pull it apart and grind inside the housing to make clearance.Then I got to thinking maybe the impeller was always out of balance and responsible for the shaft seal failure and if not balanced now the same thing will happen and be deemed my fault.Better quality pumps have a machined and balanced bronze or stainless steel impeller. The shaft is supposed to be stainless steel but is magnetic with evidence of rust.
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Originally Posted by Woznme
It does run at 2950rpm. It's what's called a DIN pump, cheap Chinese construction with coarse tolerances which is why I was considering not balancing the impeller. I've installed and commissioned plenty of these bad boys over the years. One even was delivered with the impeller rubbing the pump housing. Had to pull it apart and grind inside the housing to make clearance.Then I got to thinking maybe the impeller was always out of balance and responsible for the shaft seal failure and if not balanced now the same thing will happen and be deemed my fault.Better quality pumps have a machined and balanced bronze or stainless steel impeller. The shaft is supposed to be stainless steel but is magnetic with evidence of rust.
Reply:Your not in America, Canada or Mexico By the RPM?Dave
Originally Posted by Woznme
It does run at 2950rpm. It's what's called a DIN pump, cheap Chinese construction with coarse tolerances which is why I was considering not balancing the impeller. I've installed and commissioned plenty of these bad boys over the years. One even was delivered with the impeller rubbing the pump housing. Had to pull it apart and grind inside the housing to make clearance.Then I got to thinking maybe the impeller was always out of balance and responsible for the shaft seal failure and if not balanced now the same thing will happen and be deemed my fault.Better quality pumps have a machined and balanced bronze or stainless steel impeller. The shaft is supposed to be stainless steel but is magnetic with evidence of rust.
Reply:No heat treatment on that piece certainly makes me nervous for overall longevity... For an exhaust manifold, it might be ok, but for something rotating that fast I would sure want it to all be grey cast, without a hint of white iron in there.But maybe I'm wrong, I've never serviced something that critical before. Have you had good luck with this style of repair in the past, on similar components?SRA & IWW memberCentury: 250 amp AC/DC, 295 amp AC, High Frequency BoxVictor, Harris, and Oxweld Oxy-Acetylene Equipment.
Reply:I have used this method of repair on pressure equipment, valve bodies etc. Gears on winches. This is the first pump impeller I've done. I think the welds and repair is sound. But now you're making me nervous. |
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发表于 2022-7-24 15:51:40