selection of suitable pump for gasoline lifitng 1

[mirghaffari]

Dear Sir,
i want to select the suitable pump to lift the gasoline from the Truck. the truck is located 3 meters under the platform that pump is located on it.
we try with gear type pump (that used in gas stations), but the result is not good becuse of very low flow. we can not used check valve in suction line becuse we have to drain all remaining fuel to truck and start this process with next truck. could you help me to select the suitable pump that can prime in short time?

best Regards,
mirghaffari

 

[LittleInch]

First you need to establish how much vapour pressure you have available as this will vary with temperature and atmospheric pressure. As zda04 keeps reminding us, atmospheric pressure in mountain and high plains is a lot lower than at sea level and will reduce the amount of "lift" that is physically possible.

3m may be at the limit of "lift" and even if you can get liquid at this height, you might not be able to get a pump which will not vapourise in operation, i.e NPSHA might be too low.

What is the TVP of your product at the temperature you're pumping at? If its coming in on trucks it could be a lot warmer than when it left the filling station.

What elevation is the site?

TBH, it sounds to me like you are vapourising the liquid in the pump.

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

 

[mirghaffari]

thanks alot,
the site elevation is not too high but it seems that the pump can not wotk becuse of low NPSHA. is there any solution to incrise the NPSH in this case? or is there any pump that can work at this sicuation?
wen we fill the sucton line with gasoil, the pump works better than befor but we have to drain the suction line each time.

BR
Mirghaffari

 

[LittleInch]

Q" is there any solution to incrise the NPSH in this case"

A - Not unless you change something.
The only real things you can change are: temperature of the gasoline (not likely by enough), properties of the gasoline (again not likely to be enough) elevation of the pump - your best option.

Or lower a submersible pump into the tanker?

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

 

[EmmanuelTop]

Can you push gasoline with Nitrogen, in a controlled way of course? The additional pressure (above gasoline vapor pressure) inside the truck will generate additional NPSHA.

Other than that, you remain with options proposed by LittleInch - or change the pump type.

Dejan IVANOVIC
Process Engineer, MSChE

 

[LittleInch]

Emmanueltop - Come on - this is a road tanker. They are not built for any internal pressure.

Type of pump is irrelevant if it's sucking vapour.

I have never come across a gasoline unloading system which has the pump inlet above liquid level, never mind 3m above it

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

 

[EmmanuelTop]

I was referring to raising the pressure up to the maximum allowed vapor pressure for transport of gasoline - clearly not to pressurize the tanker up to several hundred kPa's. Apologize to the OP and to others if my post was interpreted that way.

I also understood they have problems because NPSHA < NPSHR, not necessarily that there is vapor at the pump suction. If the case, yes you are definitely correct - changing the pump type will definitely not cure the problem.

In one plant we have used a specially designed Nitrogen utility station for flushing and purging of trucks that were used for loading and transporting of the hydrocarbon product/condensate from the plant.



Dejan IVANOVIC
Process Engineer, MSChE

 

[mirghaffari]

Thanks Dears
But it is impossible to use the nitrogen for increasing the pressure. We know that the maximum lifting height is around 10 meters. Why we can not lift the gasoil 3 meters?

 

[LittleInch]

Maximum lifting height of 10m is theoretically possible with cold water which results in a pressure at the top of the column of water of around 0.05bara. More than that the water will start to boil.

Gasoline, especially warm gasoline, will boil at around 0.6 to 0.7 bara. That only gives you 0.3 bar "lifting".

research "vapour pressure" and NPSH a bit more an then you might start to understand why your system is at the limits of physical probability.

Lower the pump inlet relative to gasoline liquid height.

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

 

[mirghaffari]

Thanks very much littleinch
I underestand that our main problem is vapou pressure
Now i can chech and solve the problem
Thanks again for your help

 

[georgeverghese]

There are centrifugal pumps that are fitted with vacuum assisted suction lift - in some previous discussion on this forum, such a pump is in use in water service - see if a similar pump can be offered for gasoline service to prime the suction line / fill it up on startup.

But, as suggested, with gasoline with an RVP of say 8psi or so, there may be NPSH issues if the gasoline level is 10metres below the pump centreline.

 

[chicopee]

There is a system of gasoline vapor/liquid transfer between R.R. tank cars and storage tanks in which vapor is forced into the RR tank cars and liquid is transferred to the storage tanks. Research the web as I am sure there is information that could assist you. Altho. I have not dealt with this type of operation , I am more involved with a similar transfer operation of LPG products.

 

[mirghaffari]

Thans alot for your kinkly information and help. Today we test this arrangement again with som modification and i reflect the result here.
Thanks again

 

[mirghaffari]

Dear sir
Today we test the mentioned pump(gear type) for lifting the gasoil from 3 meter. The pump lift the gasoil esely and discharge flow was good. But the pump worked only 30 secends! And after that the flow decrease to zero!
Then we stop the power and reverse it for secend. Again we connect the power and start it and every things was ok but only for 30 secends again!
Do you know why pump work only short time?
What happen wen we reverse the direction of pump?
Why in new start pump work good again?
Thanks for your help

 

[bimr]

Lifts (when the pump port is above the liquid level in the tank) should be kept to 6 feet or less when pumping gasoline to prevent vaporizing the gasoline at the pump inlet. Check the system NPSH to make sure it is adequate.

 

[LittleInch]

No real idea.

Are you letting air in at the same time as pumping out?

Draw a sketch or attach some photos so we can work this out better.

Also do you mean gasoline or gas oil. Big difference.

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

 

[mirghaffari]

Ok and thanks again,
The teat was down with gas oil.
And in this atached schematic you can see the our plant. In fact we want to lift the oil, gas oil or gasoline from the truck for sampling. All part work ok except the pump. As i toold our pump work only 30 secends!
Regards

 

[LittleInch]

That's a start.

How far down does your sample tube go into the truck?

Why don't you use a simple container dropped in?

How much are you "sampling"?

flow rate?. line size?

Why only 30 seconds? We're too far away to see the operation or all the components so can't really add anything unless you can describe what you're doing in more detail

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

 

[Artisi]

The drawing is about as useful as tit's on a bull. If you want answers how about some decent information, sketches etc. We are very smart people but not mind readers or crystal ball gazers.

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.)

 

[LittleInch]

Artisi - great comment.

mirghaffari - We can provide some useful assistance, but you're giving us information small piece by small piece. We have about 10% of the information any one would need to help you.

I think most of us thought you were trying to offload a road tanker into a facility. It now seems you're trying to obtain small volumes from a road loading facility where you are top loading with loading arms. Big difference.

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