We use the pfte rope and wrap it aroubd the shaft, bolt down tight, but not too tight and check vac.
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Have used both the PTFE rope and pre-cut white factory seals for this purpose. the precut seals work more reliably but the PTFE rope is useful in a pinch.
The compression of the (idk what to call it, but its where the three hex bolts go through, (collar, maybe?)) is what makes the seal.
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Its typically known as packing
That would probably work temporarily, but I would still look into some PTFE rope/seals, my experience was that teflon didn’t like to hold up
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Fixing to run into the hardware store to see what I can cook up. I’m thinking if I can pack it with PTFE and then slather the top of the packing with either vac grease or silicone sealant, maybe it’ll conform enough under the pressure of the packing collar to provide a seal. I picked up some helium today so I will be able to test it to see if it works. Will definitely report back.
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I never even had to use vac grease, but I think it probably couldn’t hurt in this case.
Okay so the 5/32 PTFE rope was the ticket! I crammed it down in the and tightened the packing collar and it formed perfectly! As it turns out, this must’ve been what the guy that worked on it before me used because it looks the exact same as the “seals” that I dug out of there!
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I dont my IG got deleted or i would
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Looks right to me, good luck with running
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I was using the PTFE 1/8" braided packing from Grainger, glad you got it working!
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Okay so we tore down and cleaned all of the pumps and crammed the PTFE rope around the shaft. I didn’t know how much to use so we used quite a bit. 10in or so per pump of 5/32 PTFE rope. After letting them wear in by running the pumps and then tightening the press collars, the collars are bottoming out on the shaft guide. I’m guessing we should have used more. I didn’t want to use too much to cause too much friction around the shaft but will tear them down again and add more. Also added a layer of vac grease on top before collar to allow for some lubrication and potential sealing from air channeling.
When I run my distillate discharge pump the vac gets down to <400 micron, but when I cut the pump off, it shoots up to 3000micron. I am curious, in a properly sealed system, does the micron gauge increase when the pumps are turned on, stay the same, or go down? Obviously all inputs/outputs are blocked off to prevent leakage around the valves.
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Yes, I’ve had that issue before when running these pumps.
FWIW it looks like the blue collar isn’t evenly on the gear there. I’ve had vac issues from running like that that were resolved by getting that straightened out on there. This was on a YHChem SS unit, but the pumps looked identical. Also another note is that we had more clearance in these areas marked in red, the bolts we used may have been longer and allowed for more compression.
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Okay, so the areas marked in red. The amount of packing material in there controls how much that collar sticks out. I will be adding more in there today. We aligned all of the motors onto the blue collars but after a minute at full speed, it had already worked its way back out. Will fix today.
Also, I definitely try not to run them dry, but after repacking the shafts, it became apparent that they needed to be run to wear in. Is it a big no-no to run these things dry?
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I wouldn’t recommend it, especially if you’re trying to troubleshoot vacuum issues with it, conditions might change when the pump is wet and lead to chasing something that might be a non-issue
This boggles my mind. When I remove the distillate discharge pump from the system, I pull down to 60 micron. When I added it back to the system, I’m pulling 400 micron. When I run the pump at 50% speed, I pull down to 200 micron. I’ve sprayed etoh all over the damn thing to find leaks as well as Helium. The output is blocked off and we repacked the shaft seals on all three pumps. On all of the other pumps, the microns go up when turned on. On the distillate discharge pump, the microns go down when turned on. Which makes me think that the pump body might be leaking, but I can’t find it! What do?
I’ve let it sit for 10min with the vac pump and discharge pumps off and the gauge is reading 2600 micron.
Welcome to the fun. 90% of my time running one of these SS wipers was chasing down vac leaks.
Do you have a secondary/alternate gear pump you can throw on there to see if the gear pump is the issue? If the gears/inside of the gear box are scored up or damaged they can have vac issues. Do any of the other pumps have a similar issue? Are they all rebuilt the same?
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Yes I do. The spare pump that I have on hand was galled to shit around the shaft and the motor housing. I spent quite a bit of time on my polishing wheel and tried to remove as much of the galling as I could. It is very smooth now but I’m not sure if it will hold a seal.
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Wrap a tape heater around the gear pump section and run some sacrificial oil through. Expand that steel and fill the gaps.
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