Hydraulic motor case drain question- expected flow rate through case drain hose?

[KYErik]

I posted some questions last month about a leaky hydraulic motor and ended up buying a new 22 cu. inch low speed motor from surplus center. This motor has a case drain (in addition to the pressure and return lines). From what I have read, it is very important for the longevity of the motor's shaft seal to plumb the case drain directly back to your hydraulic sump so there is no back pressure (not even through the return filter).

I will be using several different tractors with the auger cart so it would require lots of time to install a quick connect fitting on the rear housing of each to return the fluid directly to the sump. These tractors are older and will all run less than 1400 psi.

Since this 200 bushel auger cart will probably only be filled/emptied a maximum of 5 times per year, my idea is to simply run a long case drain hose into the small opening of the lid of an empty 5 gallon hydraulic fluid bucket. I know that the case drain just gives fluid that leaks through the internal parts a place to go. But what flow rate should I expect? It should take less than 10 minutes of running the auger to empty the cart- so would the flow rate likely be less than 0.5 gallons per minute? I wouldn't want to have to line up several 5 gallon buckets just to catch the fluid that comes through in 10 minutes...

 

[LouNY]

The flow in the case drain is very difficult to predict it will vary considerably from motor to motor and increase as the motor gets used.
Also the loading on the motor will effect the case drain as well as the fluid temps, starting a full auger will take more pressure then running the auger.
Would it be easier to return that motor and get one without a case drain.
I see that they have several without case drains.
Otherwise the poor boy way would be a hose long enough to go into the fill port on the tractor and rag stuffed around it to keep out the dirt and dust.

 

[bigdeano]

You should read the manufacturers literature to determine if the case drain needs to be hooked up. Typically they're not hooked up unless there's a lot of back pressure on the motor, like if two motors are hooked in series. If you don't have to use it you just put a plug in it.

 

[KYErik]

You should read the manufacturers literature to determine if the case drain needs to be hooked up. Typically they're not hooked up unless there's a lot of back pressure on the motor, like if two motors are hooked in series. If you don't have to use it you just put a plug in it.

Ahh- that would be nice to not have to run the extra hose. I got this pic (below) from the manufacturer. The motor came with a metal plug already installed in the case drain. So since I will be running no more than 130 rpms and no more than 1200 psi on the pressure side, it looks like I will be fine without using a case drain line (leaving it plugged). Am I thinking through this correctly?

 

[CincyFlyer]

Ahh- that would be nice to not have to run the extra hose. I got this pic (below) from the manufacturer. The motor came with a metal plug already installed in the case drain. So since I will be running no more than 130 rpms and no more than 1200 psi on the pressure side, it looks like I will be fine without using a case drain line (leaving it plugged). Am I thinking through this correctly?

View attachment 541965

Seems to me that you can run it for a bit, and see how much bypass leakage you get in the case drain. It it's really small, put a "catch can" on it.

 

[bigdeano]

Ahh- that would be nice to not have to run the extra hose. I got this pic (below) from the manufacturer. The motor came with a metal plug already installed in the case drain. So since I will be running no more than 130 rpms and no more than 1200 psi on the pressure side, it looks like I will be fine without using a case drain line (leaving it plugged). Am I thinking through this correctly?

View attachment 541965

It looks like the shaft seal is good for about 1400 psi, so just leave the plug in the drain port. The pressure on the seal is only a little above the pressure in the return hose, which is usually 200 psi or less. It should work fine.

 

[mcfarmall]

As a side note, if you pressurize the case drain you can lock the motor. A piece of industrial equipment at my former employer used a hydraulic motor driving a ball screw to index a carriage. When the carriage was in position, a solenoid valve would energize and apply system pressure to the case drain and lock the motor.

Note I said PRESSURIZE the case drain. Plugging it as stated above shouldn't have any effect on it.

A hydraulic pump, on the other hand must always have the case drain plumbed to the tank below oil level.

 

[bigdeano]

As a side note, if you pressurize the case drain you can lock the motor. A piece of industrial equipment at my former employer used a hydraulic motor driving a ball screw to index a carriage. When the carriage was in position, a solenoid valve would energize and apply system pressure to the case drain and lock the motor.

Note I said PRESSURIZE the case drain. Plugging it as stated above shouldn't have any effect on it.

A hydraulic pump, on the other hand must always have the case drain plumbed to the tank below oil level.

Are you sure the motor you're talking about wasn't equipped with a brake? Some of them have brakes which are applied by applying pressure to a port.