May need an hyd oil cooler on drill have ???

burntside bob · Feb 11, 2012

I have a rock drill - its air powered. Its on a drill mast of a mini excavator with a hyd motor powering the chain applying pressure on the drill bit forcing it into ground.
The oil flow control to the mast chain motor is through a Prince flow control valve with relief valve, oil from relief valve flow going direct to hyd reservoir. The flow out of the chain drive motor goes back through the return line. The mini excavator auxiliary circuit (which is the hyd thumb on the excavators stick circuit which I connect into via quick couplers for the drills hydrolic flow) is open all the time the drill is operating applying oil flow to chain motor on mast. I have used the drill an it appears to me the oil has heated up maybe too hot, oil has gotten darker in color.
I am looking for input as to how to install a oil cooler, high pressure 1500 PSI at drill mast. And info on just who manufactures portable small oil coolers for my application? Do you need more info fro me to reply?

Blast Chamber · Feb 11, 2012

Hi Bob,

I'm not sure what size hydraulic hoses you are dealing with, but here is an online supplier where I bought a hydraulic oil cooler to fit my Trackless MT municipal tractor (RTF INDUSTRIAL OIL COOLER - 24 x 17 5/16 x 1 1/2 OVERALL). It worked great on my machine, and I had no problems with the purchase or the installation. Hope this helps.

Tractor Oil Coolers - RadiatorGroup.com

Harry in Ky · Feb 11, 2012

Why do you feel the need for a high pressure cooler? Your machine probably has a cooler already, usually near the radiator for air flow from the fan. Are you comfortable with the match of the pressure and flow requirement of the orbit motor to the output of your auxilary circuit? Excessive heat usually comes from pushing too much oil through too small a space. Is the attachment a good match for the machine or is it designed for something larger?
If you're happy with the unit and just want more cooling capacity, you might consider looking in the area of the pumps, reservoir, filters,and such for enough space to add a cooler on the low pressure side. Most coolers are on the return side, in line with filters on the way back to tank. It doesn't matter where you cool the oil, the end result is the same. Just google Hydraulic Oil Coolers, and all kinds of sources show up. Check out some of the size, flow capacity and price ranges, then compare that to your space availability and budget. You will probably need to figure in a cooling fan on it too. You can get tricky and add a temp sender in there somewhere, and a relay to turn on the fan at your desired temperature. All kinds of possibilities.
Just a few ideas.

J_J · Feb 11, 2012

Here is my hyd radiator and fan, it is about 2 1/2 in thick and cools my 20 gal of hyd fluid. It has a temp sensor to allow the fluid to heat up first, and after that it is automatic.

It seems to do an adequate job.

It is a low pressure radiator.

Duff · Feb 13, 2012

When installing the oil cooler, ensure it cools the return oil back to tank !

IceStationZebra · Feb 13, 2012

Not sure where you are located, but if it gets below freezing you might want to consider a thermostat in the cooler. They by-pass the cooler when the oil is cold so the back-pressure isn't too high and blows a line off. I know Hydac has them, but I'm sure others do too.

ISZ

Farmerford · Feb 14, 2012

I would first check the actual oil temperature as it exits the excess flow port on the Prince valve. The recommendations vary, but anything over 160-180 deg F is undesirable and by 200 deg F the oxidation rate of the oil is much too high and will shorten its life significantly.

A quick rule of thumb is that the temperature of hydraulic oil passing through a pressure relief valve increases by 1 deg F for each 140psi of pressure drop. I assume you are using the valve to keep a constant pressure on the chain and that the chain moves very slowly.

Your Prince flow control valve maintains that pressure on the chain by bypassing the unused hydraulic fluid (which is most of it if the motor is barely moving) through an adjustable orifice at the same pressure that is required to move the motor.

Suppose you need 1,000psi on the motor to give the downward pressure you require. That means the excess flow from the Prince valve is also at 1,000psi when it enters the valve and then that pressure drops to, say 0 for convenience, as the oil flows through the valve.

The 1,000 psi pressure drop in the excess flow through the Prince Valve means the excess flow temperature increases by 7 deg F each time it passes through the Prince Valve (1,000 divided by 140 = about 7 deg F).

So, if your pump capacity in gpm is such that all the fluid in your system circulates as excess flow say two times per minute, then your fluid is increasing in temperature by 14 deg F per minute. Of course, some of the heat energy is dispersed through the cooler, lines, etc., but I doubt that your system was designed to remove that much heat.

Note that this is the sitution when the motor is moving, but only slowly. When the motor stalls, the Prince valve blocks all excess flow (it is trying to force fluid through the stalled motor) and then 100% of the pump output passes through the relief valve built into the Prince valve (or system pressure relief valve if set lower).

This is one of the drawbacks of any flow control valve that sends only a small part of the fluid through a working circuit such as a motor or cylinder; the rest of the fluid (the excess) must experience the same pressure drop as the working fluid. So the control valve is in many cases just a big fluid heater. Indeed, Caterpillar says that the way to warm the hydraulic fluid in my bulldozer to operating temperature for testing is to hold the blade control lever against the stop so that the fluid flows through the relief valve once the cylinder extends fully.

The excess flow line from the Prince valve should go directly to the tank, so it will be under very little pressure. You may need a hydraulic cooler and fan in that line to keep the temperatures down.

Please send us some pictures of your rig.