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maximum Lift of Diesel Pump

maximum Lift of Diesel Pump

maximum Lift of Diesel Pump

(OP)
With reference to this similar thread, therr was discussion that a pump, pressumed a self priming is able to lift up to 12 m height.

https://www.eng-tips.com/viewthread.cfm?qid=307610

Iam wonderin if how it be possible considering

a pump is having NPSHr, let say 0.3 to 1 meter depending on speed and types of pump.

[Quote]

Lift should be kept to a minimum. For #2
not exceed 15" Hg under the worst conditions. Lifts should be kept to under 10
feet and may be even less depending on suction piping length, fittings, and priming
conditions. The vapor pressure of #2 fuel oil is less than 0.1 PSI (0.0069 BAR) at
ambient temperatures. If the vacuum at the pump exceeds 15" Hg, entrained air in oil may cause capacity and noise problems. Under vacuum conditions the air will
expand and the pump will not deliver its full capacity of oil. While the rotary pumps
self priming, a foot valve is typically recommended to minimize the chance for losing
suction.

[End]

From this source,assuming we have ample npsh,

1. is it possible to lift 9 m of diesel ?

2. If not possible, would installing foot valve helps




RE: maximum Lift of Diesel Pump

Absolute maximum suction lift under ideal conditions is approx 10 metres, however virtually impossible with a rotory pump, consider 8 To 8.5 as a maximum.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: maximum Lift of Diesel Pump

Artisi - remember its Diesel we're talking about, so SG of about 0.8 to 0.85 maybe for heavy fuel oil.

So 1) In theory - yes, just about possible, but you will need to find a pump capable of generating that low a pressure in air to prime the pump.

You would need a vacuum of close to 1 to 2 psia.

A foot valve is simply a non return valve on the inlet which stops the fluid flowing backwards when you stop the pump so that you don't have to prime it again or allows you to fill the inlet line.

So a foot valve helps but fitting one is no use if you can't prime the pump.

But operating at that low a pressure can bring air out of the liquid and be problematic as is finding a pump which can operate at that low NPSH.

The 15" Hg is about 7.5 psia

Is this a real question or idle speculation?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: maximum Lift of Diesel Pump

(OP)
Littleinch,

It is real apllication, most of tbe diesel storage is in underground and located a disfance away from pump room.

operating low pressure, are you referring to low npshr of rotary pump ? .

Assuming the npshr is low, however the suction lift is already 7 to 8 m with ample npsh margin of 2 m.

Some question ?

1. Can the pump primed ?

2. If we could not primed,some practice using a hand pump to leave it filled and would the foot valve help to start the punp ?

My doubt that pumpschool is suggesting to have 15" mercury. This must have some basis here, is it for priming reasons during start or for contibous running despite having foot valve ?

https://www.google.com/url?sa=t&source=web&...

3. Would thr diesel vaporized under 8 m or -0.8 barg suction pressure with ample npsh value ?

RE: maximum Lift of Diesel Pump

Lets make a preliminary calculation ;

- The maximum height the liquid can raise at suction side of the pump is theoretically 10.30 m for water..In case of diesel fuel, assuming S.G. 0.85 Hmax =10.30 /0.85=12.11 m .. This height reduces for the friction loss, density of liquid, steam pressure of liquid , and more important , the altitude ..

If we assume ambient temperature for the liquid ( room temp say 20 degr )and the atm. pressure at sea level ,

Hmax= 12.11-0.8-0.10=11.2 meters. If you provide a safety margin of 3.0 liquid pressure to avoid the air build up at summit and keep the flow.

That is H max = 11.2 - 3.2= 8000 mm

I will suggest you check your pump for self priming, and perform refined calculation ( with the real head loss , find the vapor pressure for the subject diesel ..) and see the situation.

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