NPK C4C Hydraulic Motor Seal Issues

[tywark]

Hi, I have a NPK C4C Compactor that seems to be building too much pressure and keeps wanting to blow out the shaft seal on the hydraulic motor. After I bought it (auction find) I found out the motor was leaking hydraulic oil into the exciter housing. I took it apart to replace the seal and noticed one of the metal spacer washers that help hold the seal in place had also broken when the seal went out. So I replaced the seal and put a different washer in there, I then put the motor back together, hooked all the hoses back up and ran the motor for 30 seconds and I notice the washer has bent already from internal pressure. I tried straightening it out and turning it around/ inside out and ran it again and it started bending again. Any idea what could be causing this? We have only been running it on a small MT55 Bobcat skid steer and Yanmar 4 ton mini excavator so shouldn't be building to much pressure, should we? I also took out the pressure relief valve with I believe is set at 2650 psi and took out all the other plugs that I could in the bypass relief block and nothing seemed out of the ordinary.

Thanks in advance

 

[heymccall]

Shaft seal sees Return pressure if motor is mounted correctly.
Shaft seal sees Supply pressure if motor is inverted.
If motor is mounted correctly, then the return circuit is suspect (for restriction).

The motor body should be biased below the mounting bolts. Inverted allows more clearance to bottom plate, but, as stated above, puts the shaft seal under spply pressure.

 

[heymccall]

 

[heymccall]

Directions in here

 

[92U 3406]

If you're in 2 way flow you'll see motor seals blow out. One way flow only. Also verify your flow rate, never trust what the monitor says, never seen a machine yet that's accurate.

Cheap couplers will cause a lot of back pressure as well. Hook it up directly or invest in some decent high flowing couplers.