pump cavitation

[ghanghas85]

i have installed 2 nos. witt ammonia pumps in a large ammonia system but when i start any pump. Both of these are cavitating. i als check the net suction head and little open the pressure vent valves but possition is same.kindly give me the suggestion.

[Brian_UK]

Some facts and figures would be useful in forming an effective conclusion.

[gregd1401]

What size pumps are these and did you fit orifice plates? Also more information on system please.

[lowtempman]

Couple of suggestions.
1. Check strainer if you have one in the suction line.
2. Obvious but is the suction stop valve closed.
3. Check pump rotation.
4. If motor is ound for two speed check it is not on the wrong higher speed.
5.

[lowtempman]

should I try again or what???

[Mark II]

Ghanhas,

Pump cavitation on start-up is normal.. Your pumps should have auto changeover & reset each other when they trip. If your system has been off a while you will get a slug of warm liquid back causing a violent boil off in your vessel including the liquid you are trying to pump..The trip differential is very fine & it will take a few minutes for the system to settle..
If you can't automate your plant you'll need to do up a start proceedure