CAT 340 direct drive pump shearing from motor

[Sequoia]

I finally put my car wash up for sale and it is responding to that by doing a repeated, expensive failure that I cannot figure out.

I have 3 CAT 340 direct drive pumps fitted up to Baldor motors. Two months ago, Bay 1 pump, which has been installed for over a year, suddendly sheared all 4 mounting bolts and leaked all the oil out. It was hanging in place by the hoses. I replaced it, and then it happened again. Now it has happened twice more. The other motor pump combinations do not do this.

Years ago, I did replace the Baldor motor and at the time had to switch to a different flange to properly mate up the motor and pump. All seemed well at the time and it all installed correctly and ran without problems.

I first suspected improper bolts, so I special ordered the correct bolts (size and hardness) from CAT. Plus I use threadlocker when installing them. And, during the last repair, a device to mitigate water hammer was added to all 3 pumps (looks like a black piece of HP hose, about 2 feet long or so.)

I'm stumped. All 4 bolts shear off. The fellow at CAT didn't have much info and ventured a guess that maybe the bolts are loosening, but at that time he didn't know I was using threadlocker.

Any ideas on my CAT pump issue?

 

[MEP001]

It seems strange that it would start doing it suddenly. You might have a faulty regulator allowing the pressure to sometimes get too high. You could also add a delay on/delay off relay so that the pump can't get switched off/on too quickly while changing selections.

 

[PaulLovesJamie]

Duane,
best wishes on your sale.

Sorry for using what is probably the wrong names/terminology, but...
do you mean the little bolts (around 1/2 - 3/4" long??) that bolt the flange to the crankcase?
If so, I seem to recall having problems with them working loose on one pump many years ago. iirc the key that mates the motor's shaft with the crankshaft in the pump was worn, I think it got that way because the 2 little allen bolts that hold it down worked loose. Anyway I think that was causing the crankshaft to jerk every time the motor started, thus causing undue torque on those little bolts.
I replaced that little key, loc-tited the 2 allen screws in place, and havent touched it since.

Not sure if thats what you're talking about though

 

[mac]

This is why I don't use direct drive pumps, but that's another story. With any positive displacement pump, which these are, the water HAS to go somewhere when the pump is turning. On belt drive pumps I've seen the valve plugs blow off when the water had no place to go. I suspect that your bypass regulator may be an issue. Also you do have a safety pop off on the discharge of the pump right?

 

[Sequoia]

Pump

Thanks for positive wishes on a sale. I enjoy owning the wash but I simply have piled too much on elsewhere to keep owning it.

Yes, the bolts are 6mm, flathead, I think about 25mm long or about an inch. We have not been using loctite on the allen bolt but I did install a brand new shaft key last time. A new regulator was installed on the 3rd pump change. I believe there is just one allen bolt, not two?

I supported the other two pumps with a 2x4 wooden "stiff leg" under them. When I reinstall this pump I will do the same, loctite everything and allow it to set for 24 hour before usage. I also got some stronger bolts (flathead) that are 12.9 hardness instead of 10.9 hardness whatever that is. I will probably also reduce the operating pressure from 1000 to 900 psi.

One note-- I removed the pump yesterday and found that the pressure gauge is leaking oil. It needs replacement. Not sure if it was reading the wrong pressure but the bay pressure seemed right.

And, time to show some ignorance. What is a "pop off" valve? Having never encountered one, I'm guessing or sure my wash does not have them??

Thanks!

 

[MEP001]

A safety pop-off is to prevent the pump from an over-pressure condition in case the regulator malfunctions. I've seen that happen with a regulating unloader, but never with a bypass regulator.

 

[Greg Pack]

No solution here, just sympathy. I leased a wash many years ago that had 350s and encountered the same problem. There is just too much torque on those little bolts, and if things don't go together just right they were a problem. I would perhaps look at building a frame assembly to take the torque off the mounting bolts.

I believe they have transitioned to a the spider/lovejoy coupling to reduce the problem. I wonder if there is a practical way to add this.

 

[Sequoia]

Thanks

I appreciate the responses-- thank you.

On my two remaining pumps, which I have not had a problem with, I have added a 2x4 wooden "stiff leg" between the pump body and the concrete floor.

CAT has suggested checking for a wobble in the motor shaft, or to check and see if the motor, flange, and pump are misaligned. I asked "how do you do that" and they responded by asking me to ship the entire assembly to them in MN. Argghhh. They also asked if I have a 3hp motor or a 5hp motor and I simply don't know. I live 90 miles from the wash so I will have to check it next trip.

I am going to carefully check the alignment, somehow, then put it all back together, apply the threadlocker, put a stiff leg under bay 1 pump, and let it all set for 24 hours before I turn it back on. I also got some higher hardness bolts (10.9 whatever that is)

The only benefit here is that I bought myself a real nice drill press from Sears to use to extract the broken bolts. If it saves even one pump body I'll pay for the press right there.

 

[Sequoia]

New info

New info:

I went to reassemble the new pump, motor, and flange and found that one of the screws that holds the shaft key secure to the shaft was missing. The shaft key was held in place using only one of the two screws that should be there. Hmmmm.

I located a correct replacement screw, and decided to clean all parts before reassembly. When I carefully cleaned the flange, I observed that the mount holes from the flange to the pump had been ovalled from prior stress. This was not visible when the flange was greasy/dirty. Its just a guess but I think it was ovalled from the first shearing episode and might have contributed to each one since.

I erred on the side of caution and ordered a brand new flange. Hey, why not throw even more money at this? Maybe the use of only one set screw allowed the key to move, and maybe (likely?) the ovalled holes on the flange were allowing the pump to move. Even a slight movement, magnified by each on/off cycle, might lead to the bolts shearing.

I had substandard strength bolts at the time of the first shearing, so maybe with a new flange, proper hardness bolts, etc., I can get back to some reliability.