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Carbon commutator with carbon brushes for use in a pump submerged in fuel

Carbon commutator with carbon brushes for use in a pump submerged in fuel

(OP)
I have a fuel pump motor that is submerged in the fuel tank (gasoline). I'm having an issue with the brush life when the speed and flow rate is increased (increased current). I have researched the issue in the Engineering Tips forums as well as internet search and I've found some (very little) information. Does anyone have experience with this type of application? I could use some help when I begin to analyze the problem. I can't find any information with respect to acceptable current densities for this application as well as acceptable speeds and spring forces for the combination of carbon commutator with carbon brushes submerged in fuel. Thanks in advance for your help.

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

Is this an automobile fuel pump?
How are you increasing the current?
Is this a sealed pump? Please don't tell me that the gasoline is contacting the brushes directly.
Tell us a little more.
Is this a home built or shop built pump or a manufacturers approved assembly?
Is this a transfer pump?
What is supplying the current for the pump?
Battery? Power supply?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

Commutator submerged in a gasoline tank? It's a bad, bad idea.

Muthu
www.edison.co.in

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

There are millions of cars on the road with the fuel pumps submerged in the gasoline tanks.
However these pumps are sealed and the gasoline never touches the brushes.
These pumps are not serviceable.
If the gasoline is in contact with your brushes the best I can do for you is to share an old ditty, to the tune of:
"My Bonny Lies Over the Ocean"

My Bonny leaned over the gas tank,
To see what the level might be.
I lighted a match to assist her,
Oh bring back my Bonny to me!

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

(OP)
Thanks for the replies. I'm traveling to the site tomorrow and I'll have a better idea of the situation. All good questions, I'll answer as I can:
Is this an automobile fuel pump? May be auto or marine.
How are you increasing the current? By increasing the load is what I understand
Is this a sealed pump? Please don't tell me that the gasoline is contacting the brushes directly. I'm not sure yet but I think it is sealed
Tell us a little more. I'll share when I see what is going on
Is this a home built or shop built pump or a manufacturers approved assembly? Manufacturers assembly
Is this a transfer pump? There are two pumps involved and one is a transfer pump. I'm not sure which one is having the problem
What is supplying the current for the pump? Direct DC
Battery? Power supply? Battery is what I've been told

My understanding is that they have realized reduced the brush life when they tried to increase the flow by increasing the speed. They are not able to share too much information and that is why I'm going to the site.

Thanks again for your reply.

Clyde Hancock
Design & analysis of electric motors and generators
www.motorconsultants.com

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

Helwig Carbon doesn't publish too much technical info but their sales engineers are very good:

http://www.helwigcarbon.com/

Is the user trying trying to load up the pump to more than it was designed for? If not, I'd contact the manufacturer of the pump or motor and get their input.

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

If they are trying to speed up the pump, then they may be applying a greater voltage than the pump motor is rated for.
That will void the warranty and will quite possibly push the characteristic curves of the motor into the non-linear range.
I suggest that the rapid brush wear is a strong indication that the motor and pump are being misapplied.
Sometimes you can push a device past the manufacturers limits, sometimes you can't.
This may be an instance of "You can't."

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

Especially if it's a centrifugal pump. An increase in speed will result in the load on the motor increasing at the cube of the speed change. So for example if they increase the speed just 20%, the load on the motor increases to 173% of what it was at rated speed. You could be burning the brushes because that's the first point of failure of an overloaded DC motor. People do this sort of thing all the time, not understanding the consequences. If they need more flow, get a bigger pump...


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

Those canned fuel pumps are automotive in nature. 'Automotive' means optimized to within an inch of their lives so they can be dirt cheap to produce in the millions. Demanding more from them will almost always result in a stunningly reduced time-before-failure. If you want to use OTS automotive parts you need to load them the same or less.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Carbon commutator with carbon brushes for use in a pump submerged in fuel

(OP)
I've contacted Helwig and they have been very helpful. Thanks again for all of your help.

Clyde Hancock
Design & analysis of electric motors and generators
www.motorconsultants.com

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