Bad Cat Packing Kit?

[bigleo48]

One of my Cat 5cp2120W pumps for a self-serve bay started pulsating. When I inspected the valves, I found a couple of bad 'O' rings. Replacing them stopped the pulsing. I then decided to change the pump seals (AKA packing kit). This is the first time I've done this, but it seem simple enough and I understand how the pump works.

So I replaced the LP and HP seals (the LP on the outside and the HP deeper in the cavity) and the 'O' rings and put the pump back together. I had also inspected the ceramic plungers and they looked ok. I had to prime the pump which kinda surprised me, but once primed all was good. (no I did not run it without water for more than a few seconds).

After a while, the pressure starting dropping (usually at 1200PSI, but I could go above 1500). Now my max is 1100 with no vibration. Would the problem likely be with the seals? I tripple checked that I replace the LP seals with LP seals and the same with the HP seals. Do you ever get a bad batch?

Big Leo

 

[MEP001]

I've never gotten bad seals. The best thing about the 5CP is that it's difficult to mess something up when you reassemble the pump since the seal casings (brass pieces that hold the packings in the head) are self-adjusting. I doubt this is the cause of your problems, but did you check to see that the casings weren't eroded before you put it back together? It's also easy to cut the large o-ring that goes around the seal casing, which would let it draw air and lose pressure. Did you also triple-check that the seals all went in with the groove "down?"

CP Plunger Pump service manual:

http://www.catpumps.com/select/pdfs/CPSvc.pdf

If clicking the link doesn't open it in Adobe Reader, right-click the link and select "Save As..." then choose a target directory in which to save, then you can open and/or print it.

 

[Keith Baker]

I was just fooled by a similar situation last week. Make sure that you are getting all of the flow you need coming to the pump.
I had one that would sometimes hammer and sometimes have a drop in pressure. My first guess was a bad poppet on one of the valves, but that wasn't it. After posting a question about head washout, some one suggested that I check for a collapsed suction hose or bad check valve. It ended up being the inlet strainer was about 75% covered with calcium.
I don't think that the pump woud work at all if you had parts in wrong would it?

 

[MEP001]

I don't think that the pump woud work at all if you had parts in wrong would it?

It will, with symptoms similar to what bigleo described.

 

[bigleo48]

Thanks for all the responses!

It turned out to be the unloader 'O' rings. I didn't think it was the Unloader because when I pinched the unload hose, I should have gotten full pressure, but I did not, so I suspected the pump.

Thanks again...Big Leo