We are running a Omax P3050 pump 30hp at 47KSI and RPMS at 700. Every Morning when we start it up the pressure goe's up to 54 to 55 ksi and it DEAD HEADS the pump. If we run it at low pressure, rpms at 654 and do a water test for about 5mins then it seems to work ok, we can then up the RPMS up to 700 And the KSI to 47 and it will run the rest of the day with out dead heading.Just before this started happening we installed two PULL TO OPEN on /off valves and ACTUATORS."Note".  We are running with two MICRO NOZZLES  .007 DIAMOND JEWELS .015 MIXING TUBES, AIR PRESSURE AT 80 PSI, WATER  AT FILTERS 120 PSI.

We've replaced:

• Adjustable dump valve
• Charge pump
• Water filters
• All actuators
• Cleaned the cooling water tank
• Diamond jewels and other nozzle parts
• Checked the pressure transducer
• Checked RPM voltage at side panel
• Oiled the control block
• Changed air pressure up and down

Jim, No doubt this is tricky and sounds like you covered many bases. It is not terrible uncommon for pressure to go up or down a bit after running for a short time. 7-8ksi is too much though. This is what I would check... When you say you have replaced all the air actuators, are you are referring to the air solenoids? If this is the case, this may not be the issue, but make sure you are not bleeding a bit of air to the nozzle valve while cutting. You can simply unplug the small air line while the nozzle is on and put it in some water to check for air bubbles. Since you have already checked a bunch of things, there isn't much left. Though you haven't mentioned it, I am assuming you have replaced the ball and seat components. One other possibility is a small hairline fracture in a check valve that only bleeds by after the water is on for a bit. A couple of tricks you can do on the Omax pumps that may be helpful... A) You can peak in the charge tank at look at the volume of water coming out of the three cooling return lines. Check it when you first start up and then when the pressure drops. See if one of the lines has any noticeable increase. If this is the case, you can follow this line back and pin down what cylinder the issues is in. This would usually imply issues with the dynamic seal itself or something else as you move closer to the crank. B) Another test you can do, is to kink the gray water supply lines (make sure you don't do the cooling lines) one at a time. See what the pressure drop is for each cylinder and record it. If one of the has a smaller pressure drop, this is the problem cylinder. A problem here would imply an issue with the check valve. I hope this info steers you into the right direction. Let me know if I can help any way. Tim