Trouble Shooting -Vapor Locked Pump
1) Open the suction and two discharge diaphragm valves all the way.
2) Close the needle valve on the rotameter
3) Close the vent valve on the saturation tank
4) Turn the pump on
a. Record the suction and discharge gauge values (they should be 0 and 0)
b. Observe the gauges for 1 minute and note any changes in gauge readings
5) Throttle the two discharge valves until a pressure reading of 40 psi is observed on the pressure gauge
6) Allow the pump to operate for 5 minutes and note any major fluctuations on the discharge and suction gauges
7) After 5 minutes, try throttling the suction valve to generate 1 inHG on the vacuum gauge
8) Readjust the discharge valves for a discharge pressure reading of 40 PSI
9) Allow the pump to operate for 5 minutes and note any major fluctuations on the vacuum and discharge pressure gauges
10) The main question here is: can the pump operate without air at steady state?
a. If it cannot, then there may be an issue with the pump or piping system leading to the pump
If the pump is able to operate at steady state without air, try it with a reduced amount of air:
1) Is the rotameter clean? No water vapor, moisture or dust affecting the movement of the float?
2) Open the needle valve on the rotameter to allow air flow to the pump.
a. You should be able to open the needle valve all the way without the float going to maximum scale.
i. If it does go to maximum scale or is above 1 SCFH, open the suction valve to reduce the air flow to 1 SCFH
b. If you are not able to generate air flow, slightly throttle the suction valve until you generate 1 SCFH of air flow on the rotameter.
3) Readjust the discharge valves for a pressure reading of 40 PSI
a. While doing this, you may need to readjust the suction valve to maintain air flow. This is an iterative process
4) Slightly open the vent valve on the saturation tank, this will release coalesced air bubbles and vent them back to the effluent box on the DAF
a. This valve should be open just enough so that air and water are spitting out, it should not be a constant stream of water
If you are able to do the second segment, please observe the system and note changes in suction pressure, discharge pressure and air flow. What will be helpful to determine the cause is:
1) Does the air flow rate go to maximum just before a zero pressure state?
2) Does the suction gauge spike just before a zero pressure state?
3) What is happening just prior to the values not holding?
4) Is there a change in sound of the pump? Vibration?