pump starts 1

[BRIS]

For estimating pump sumps and tank volumes I have generally allowed 3 starts per hour for storm water irrigation pumps which operate only intermittently and 8 pump starts per day for pumps in irrigation and water supply pump stations which operate continuously. (Thus for a irrigation supply station with 3 duty pumps operating in rotation I would allow (3x8) 24 starts per day). Perhaps I am being over conservative but early in my career (30 years ago) I had an irrigation project that suffered early fatigue failure of the distribution pipes due to frequent starts and stops.

I am presently working on an irrigation supply project with 9 pump stations with pumps between 20 and 400 kw, pumping into GRP distribution pipes. I have based the pump sump and storage calculations on 8 starts per day per pump. The client now wants to reduce the sump volumes.- increase the number of starts per day per pump to say 3 per hour.

I am working in developing countries so my philosophy is too keep everything simple and avoid devices such as soft starts and stops.

Any views on the maximum number of starts per day? (assuming there is no restrictions from the power supply).

 

[BobPE]

Bris:

It is a balancing act. Pump starts should be directly related to volume to allow the pump to run once it starts for a minimum period of time to cool the pump from its start. Another limiting factor is availability of equipment. If you can get pumps and parts in a quick period of time, you may want to minimize volume. If you cant get parts quickly, then maximize volume and try to get the maximum pump life.

This is how I look at it....

BobPE

 

[electricpete]

NEMA MG-10 has suggested starting limits for motors based upon horsepower and speed which are intended to allow the motor to reach its normal life.

Higher horsepower and higher speed motors driving higher inertia and higher torque load during starting (i.e. contsant torque vs speed^2) all drive towards lower starting limits.

One other factor beyond total number of starts which is very important is establishing a minimum time between starts to allow the motor to cool.

I can provide more info on motor starting limits if you like (let me know), but I'll stop for now because you asked about pumps, not motors.

 

[BRIS]

Thanks - yes I should have said pump sets. The limiting factor is obviously the electrical side - pump motor and switchgear not the pump.

The pump stations will be in the Bekaa Valley in the Lebanon - so availability of spare parts and maintenance will be low.

 

[fredb]

Hello

You might want to take a look at:

http://www.joliet-equipment.com/allowable_starts.htm