Pump Reduced Pumping Rate

Check whether any airlock has happened...if so do venting and also check if any leakage is present in its discharge line.

• Is the pipework leaking?
• Is there a mechanical obstruction wrapped round the impeller?
• Is there a dead bird jammed in the volute?
• Has the supply altered its characteristics?
• Is the volute cracked or broken?
• Is the impeller damaged or even worn-out?
• Has someone inadvertently fitted a smaller replacement impeller and not said anything?
• Is the inlet obstructed in any way?
• Is the outlet obstructed in any way?
• Has the level in the supply tank dropped so that only 180 litres per minute is available to the delivery tank as per the pump characteristic curve?
• Is the pump cavitating in any way?
• Has the specific gravity of the fluid being pumped changed?
• Has someone closed a valve without making it known?
• Are there other pumps running in parallel that have started up?
• Has the pressure above the liquid in either or both of the supply tank or the delivery tank changed in any way?
• Has the assembly been tilted or accelerated in some way so as to increase the head needed to effect the transfer?

Etc., etc.

With so little information to go on your best bet is what vir540 said that you may have air trapped in the pump, so drain and re-prime the pump to remove any trapped air.

If this doesn't work check the pump system lines and valves and open the pump up and clean it. Also consider checking your supply voltage which may be lower that usual resulting in the pump operating slower (unless it is operating off a variable speed drive).

Anything else is just a guess.

Dear Mr.benombori

I want to supplement to the points referred by Mr.PWslack - vide No.2 here. Mr. PW Slack has touched all the points from Engineering Point of View, however I want to include the following.

1. Whether the SUCTION HEAD is reached the THRESHOLD LIMIT.? Suction Head should be less than 26 Feet or 7.92 Metres.

2. What is the height of the liquid level over the Foot-Valve in the suction line - if it is too less Air Ingress will happen in the form of small whirl and lead to problem in the impeller and reduce the NETT FLOW.

3. Is tere any VOLAGE variation,in the Power Supply.?

Pl. include these 3 points also while checking.

Thanks,

DHAYANANDHAN.S