One of them is a series 10 open 25 HP Sullair.
For a while, I was having serious overheating problems. After cooling off, it would run for about a minute, and then shutdown. The discharge air overtemperature switch was faithfully doing it's job. At first, I figured the switch itself had degraded as some troubleshooting sources suggested, so I tried a new one with the same results. I tried a new oil filter. I tried new oil. I thouroughly cleaned all the cooling coils. Nothing was helping. Neither did any of the manuals I could find, nor any of the troubleshooting charts I could find. I figured perhaps it was the screw compressor head itself. I am glad I was not too hasty to replace it.
After all the previous steps, (not necesassarily in that order), I removed the thermal control valve (a glorified thermostat, no different than one in an automobile, only larger), and installed bypass plumbing with a ball valve. That did not help either. I suspected it may be the oil stop valve was restricted, but there was no easy way to verify my suspicion, not any easy way to bypass it if it was. I installed a tee with an air pressure gauge to the pilot port of the OSV, to verify whether it was even getting a signal to open. That portion was working just fine. I considered bypassing the OSV by using some other port on the screw head, but none sufficed to do the job that the main OSV port does. Finally, I figured I could tap out of a spare downstream (filtered) port from the oil filter, and supply oil into a tee I installed into the output side of the OSV.
Success!
That was it, the OSV was not opening up enough to allow adequate oil to help cool down the compressor head.
Until I got the rebuild kit for it, I determined to use an oil stop valve bypass valve to correct the problem. Incidently, the purpose of the OSV, is to stop the oil flow to the head when the compressor stops running. If the oil flow is not prevented when stopped, it ends up gushing out the intake air filter. What a mess! Don't try it at home kids!
I have a ball valve installed just before the OSVBV, to shutoff the bypass as long as the OSV is doing it's job. Just after the ball valve, I installed an inline sight glass to monitor oil flow in the bypass. I connected the inlet and outlet of the OSVBV with generic hydraulic hoses. The OSVBV is rated for as much as 210 degrees F. That rating should always be adequate as the air discharge temperature switch is rated at 250 degrees F, and the oil supply to cool the head should never come close to that temperature. The unit now runs at about 150 degrees F. I connected the 120 volt OSVBV coil in parallel with the run contactor, and in series with the selector switch you can see just to the left of the ball valve, so it will energize as long as the compressor is running, unless the selector is off. The ball valve that is plumbed into the thermal valve housing, is normally always kept closed, to force all oil flow through the cooling coils. Only if the compressor were to get too cold, would the valve need to be opened. In the environment this compressor is in, I don't think I will ever need to open it.
|
|
| |
| Sullair series 10 open 25HP | Thermal Valve bypass | Oil Stop Valve Bypass Valve |