Hydraulic gear pump ports and line sizing

[grandnat_6]

I am between selecting two gear pumps. One with .25 cu in at 2000 RPM or .38 cu in at 2000 RPM. In order for .25 cu into get the right flow, I will need to increase the speed to 3000 RPM. Gotta belt drive it either way. I have sized up a suction line of 7/8" I.D. that will get me a velocity of 1.76 ft/sec.

The inlet port on the .25 pump is a SAE 8 otherwise for a (8/16) 1/2" line. The pump with the .38 has a SAE 10 inlet port other wise (10/16) 5/8" port.

Because the inlet port size is smaller that the suction line; does running the larger suction line defeat the purpose of sizing the larger line to fit the rule of thumb that a suction line shouldn't go over a velocity of 4ft/sec? It seems like the port size in either pump has defeated itself for the 4ft/sec max velocity for a suction line...

Interested in members thoughts.

Thank you!

 

[Illmatic1]

Yes, running a larger suction line than the inlet port size of the pump can indeed defeat the purpose of sizing the line to fit the rule of thumb that a suction line shouldn't go over a velocity of 4ft/sec. The larger suction line would cause the velocity to be lower than the 4ft/sec limit, which is not ideal for proper operation of the pump. In this situation, you may need to consider using a different pump with a larger inlet port size that is better matched to the size of the suction line.