Inches of mercury conversion to suction of oil

   / Inches of mercury conversion to suction of oil #1  

PutnamVictor

Bronze Member
Joined
Dec 26, 2009
Messages
52
I'm looking at a Hydro-Gear pump that states a continuous inlet vacuum of 4 inches of mercury. That converts to 54 inches of water. So since oil is lighter than water, can I place the pump 54" above the tank?

My uncertainty is that I'm not taking into account the viscosity difference, the diameter of the suction line, or even something else?
 
   / Inches of mercury conversion to suction of oil #2  
I'm looking at a Hydro-Gear pump that states a continuous inlet vacuum of 4 inches of mercury. That converts to 54 inches of water. So since oil is lighter than water, can I place the pump 54" above the tank?

My uncertainty is that I'm not taking into account the viscosity difference, the diameter of the suction line, or even something else?

Pump design/application involves a parameter called NPSH for Net Positive Suction Head.

This link is to more detailed explanations.

https://www.pumpschool.com/applications/NPSH.pdf.

In simple terms, a pump will operate best if it is not struggling to get adequate fluid flow into its inlet. The important term is POSITIVE.

Unless you have the experience and skill to do the calculations for NPSH, it is best to keep the pump low relative to the fluid level and the connection between the pump and tank large.

Deviate from these simple rules and risk pump damage from cavitation and poor performance.

Dave M7040
 
   / Inches of mercury conversion to suction of oil
  • Thread Starter
#3  
Agreed, but that can't be done in this case. The hydro motor, transmission, and tank are one unit out of a Wheel Horse D series. I can't run the pump lower than the tank.
 
   / Inches of mercury conversion to suction of oil #4  
Agreed, but that can't be done in this case. The hydro motor, transmission, and tank are one unit out of a Wheel Horse D series. I can't run the pump lower than the tank.

I would think though that the pump is mounted lower than the normal fluid level in the tank.

Dave M7040
 
   / Inches of mercury conversion to suction of oil
  • Thread Starter
#5  
From the factory, the pump is 18" above the fluid in the tank.
 
   / Inches of mercury conversion to suction of oil #6  
From the factory, the pump is 18" above the fluid in the tank.

You can be assured the factory engineers would have done the appropriate NPSH calculation for the pump/fluid arrangement.

Would the pump inlet location on the tank come from the bottom of the tank?

This would improve the NPSH calculation compared to sucking from the top of the fluid level.

Dave M7040
 
   / Inches of mercury conversion to suction of oil
  • Thread Starter
#7  
Yes, the suction line comes from the bottom of the transmission/tank.
 
   / Inches of mercury conversion to suction of oil #8  
I'm looking at a Hydro-Gear pump that states a continuous inlet vacuum of 4 inches of mercury. That converts to 54 inches of water. So since oil is lighter than water, can I place the pump 54" above the tank?

My uncertainty is that I'm not taking into account the viscosity difference, the diameter of the suction line, or even something else?

I have taught fire service hydraulics for over 40 years so I will throw in my 2 cents.

You say that the pump states a continuous vacuum of 4". Is this the parameter of the test that determined the flow and PSI rating? If you saw 0 inches of mercury vacuum, would you be able to deliver greater than the stated pressure and volume? Is 4" the maximum negative pressure the pump will develop?

You are on the correct path by determining the viscosity as it relates to the friction loss of the suction side plumbing. Remember to add "loss" for a suction strainer, any supply piping and any elbows in the plumbing. Rule of thumb is slow the flow rate (GPM or fluid velocity) and you reduce those parasitic losses which is probably common sense to you.
 
   / Inches of mercury conversion to suction of oil #9  
Question about what fluid is spec'ed for the hydro gear pump. ?? (I wouldn't raise the pump any higher than OEM if possible.)

btw, my Terramite and the HG 3100s in my ZTR call out 15w-40 'diesel motor oil', warmup times are short in cold temps. :2cents:
 
   / Inches of mercury conversion to suction of oil
  • Thread Starter
#10  
Question about what fluid is spec'ed for the hydro gear pump. ?? (I wouldn't raise the pump any higher than OEM if possible.)

btw, my Terramite and the HG 3100s in my ZTR call out 15w-40 'diesel motor oil', warmup times are short in cold temps. :2cents:

Fluid Viscosity Limits @ 230°F [110°C]
Optimum SUS [cSt] 70 [13]
Minimum SUS [cSt] 55 [9]

This is not an OEM pump. It's actually a variable displacement piston pump. There will be lots of body, and hydro modification to this tractor.
 
Last edited:

Tractor & Equipment Auctions

2006 CATERPILLAR 312CL EXCAVATOR (A51406)
2006 CATERPILLAR...
2007 Chevrolet Impala Sedan (A51694)
2007 Chevrolet...
2016 Chevrolet Impala Limited Sedan (A51694)
2016 Chevrolet...
2010 Ford Edge SE SUV (A51694)
2010 Ford Edge SE...
Как зайти с телефона на кракен. kra39ac.cc  | Kraken зайти на площадку? как пополнить кошелёк? Правила диспута
Как зайти с...
2003 Ford F-350 Dump , VIN # 1FDWW36P63EC81092 (A51572)
2003 Ford F-350...
 
Top