Measuring Vacuum Pressure in Suction Line
Measuring Vacuum Pressure in Suction Line
(OP)
I am testing a single-element gerotor pump (0.58 cu in / rev)using Mobil 254 jet oil at 65 deg F. I am using 0.5" stainless steel piping with generous bends (and no fittings)for both delivery and suction and run the drive motor at 3000 RPM. Using a Bourdon vacuum pressure gage tapped into the pump housing at suction, I expected to see practically no vacuum pressure. To my surprise I am reading 10 inches Hg consistently. What am I overlooking?





RE: Measuring Vacuum Pressure in Suction Line
RE: Measuring Vacuum Pressure in Suction Line
Steve
RE: Measuring Vacuum Pressure in Suction Line
Good luck,
Latexman
RE: Measuring Vacuum Pressure in Suction Line
The vertical distance from gauge centerline to liquid surface is 8.5 inches.
The supply tank is well-vented.
RE: Measuring Vacuum Pressure in Suction Line
RE: Measuring Vacuum Pressure in Suction Line
RE: Measuring Vacuum Pressure in Suction Line
Raising the oil can above the suction inlet level will help your static suction. Flaring the suction tube end will make a big difference to the dynamic pressure drop.
RE: Measuring Vacuum Pressure in Suction Line
I calculated the dynamic contribution to be under 1 psi.
As the digital image shows, I already attempted to minimize the static head by shortening the vertical distance between the fluid level and suction inlet.
Any other suggestions?
RE: Measuring Vacuum Pressure in Suction Line
At 65 F, the viscosity of that oil is ~ 50 cP. You may be in laminar flow.
Check those two things out and re-calc if needed.
Good luck,
Latexman
RE: Measuring Vacuum Pressure in Suction Line
Ted
RE: Measuring Vacuum Pressure in Suction Line
RE: Measuring Vacuum Pressure in Suction Line
Good luck,
Latexman