How to Start Centrifugal Pump

Different setups and situations will require different procedures.

What do you have?

For positive displacement pumps (gear, piston, vane, progressive screw) it is critical to open the discharge valve before starting the pump.

For centrifugal pumps, this is not so critical; and full opening of the discharge valve can even result in pump cavitation. For best NPSH_A, the suction should be fully open, but the discharge can remain closed or throttled until the pump is started, and then gradually opened. If cavitation or pressure instability occurs, throttle back down slightly; and then adjust further as needed for stable operation.

Spot on T.

Especially with heavier product.

Many moons ago when I was loading/unloading AC 10 and AC 20 (Asphalt Cement) to/from river barges, discharge valve throttling is exactly what we had to do to get the product moving.

Even when heated at 325 F, the stuff was still like molasses until the transfer piping came up to temp.

How can we do it in automatic starting of pumps in pressurised system or fire fighting where pump starts by pressure switch or in water storage system where pump starts by float switch in an overhead tank?.

Fire booster pumps are usually 'flooded' - meaning kept at full prime.

"Priming", (which is what most of the above justifiably assumed from your original question), is not an issue, as it it done by default.

You would arrange a booster pump flooded in the normal mains flow, or use a 'flooded suction' pump in a reservoir, or feed to a flooded pump from a reservoir.

In all cases both valves would be fully open and only closed for maintenance reasons.

These valves are always open so if a booster fails, the system will still work to some extent - by mains pressure or gravity.

In Saudi arabia every home has an underground tank and a duplex water pump maintaining about 3bars in the piping system.Also in schools and big buildings they have fire-fighting pump with jockey pump operating by pressure switch maintaining 5 to 7bar pressure with foot valve in underground tank. In those cases what is your advice?.

Start your own thread and let Holzfeller and WJMFIRE know about it

If the pump has been run before, and the discharge valve adjusted as need be; then you can leave it that way, and the pump should start okay. (Especially if the discharge line has a check valve so that it remain filled from the previous time.)

Thanks. What is the meaning of self priming pumps,will they start without foot valve if suction is negative?. Will a multi stage centrifugal pump start without priming?.

We have come across instances where the Client's engineer(arabic speaking) insists the discharge be fully open. We couldn't explain them due to language problem. If we have a solenoid valve normally open but partially closed during starting by the starting signal will it be ok?. Similar to avoiding OL protection for fire pumps is it worthwhile incorporating in the NFPA regulations?.

My centrifugal pool pump starts totally unrestricted every day, with no apparent damage, yet. It's only 30 years old though and still may fail, someday.