External-gear-pump operation. 2

[luciom]

If in an existing installation for diesel pumping with subj. type pump the diesel is replaced with water, will tere be a substantial difference in the discharge pressure ?

 

[EGT01]

For your existing installation, keep in mind that the pressure at the discharge of your pump is the sum of the delivery pressure (at the far end of your line) + dynamic losses in the line between pump and delivery point + static head difference between pump discharge and delivery point. Of course a change in liquid viscosity and/or density will have an effect on those values but, offhand, I wouldn't think there would be a substantial difference between diesel and water as long as the only change is the fluid properties. I would suggest you do the math to be sure.

 

[jay165]

Assuming all the other conditions remain the same, the discharge pressure will increase linearly with the change in specific gravity of the liquid. Thus if your discharge pressure is 100 psig with a sg of 0.8 and you increase the sg to 1.0 you will increase your discharge P by 25% to 125 psig. You didn't ask, but the volume delivered will remain the same for a PD pump but the HP required will increase by the same amount as the discharge P.

You also didn't ask, but I would sure that the pump materials can take a change from diesel to water. Gear pumps rely on the lubricity of the fluid to keep the metal from grinding up.