A friend sent a homemade log splitter over to my shop saying that the pump loses prime because it is mounted too high above the tank. How do you go about determining the maximum lift that a given hydraulic pump can be above the tank fluid level?

This is a 2-stage pump (I'll check on the brand and model and post later) driven directly by a 5.5 hp Honda. The pump is currently mounted about a foot above the fluid level.

I am technical, just not in FP other than basic physics.

If pics can be posted here I can take pics too.

Please help if you can. I spent an hour searching but didn't find the help I needed.

The pump is a 2-stage and other than what looks like a serial number only has one marking on it. It has P-24 stamped on it.

The valve is stamped Energy and has a tag stuck to it that a few number are visible on. One of these number is CVA-200.

I'll try to add a pic next.

In theory, 30+ feet for one atmospheric pressure. In reality, as low as possible.
You probably have a suction hose lean or shaft seal leak. they can leak air but not leak oil.

k

Hi,
1) Maximum theoretical Suction head can not exceed ~10 meter ( 32,8 ft).
Prctical , thumb estimation , dont go higher then 1 meter (3,28 ft).
Height depends also in flow resistance, so what I recommend is to
minimuze the suction head . To be on the safe side you can install a
vaccum gauge near to pump's Inlet Port to verify that vaccum do not
exceed 0,1 Bar (1,5 PSI). All correct only if you use the right oil
viscosity. Cavitation is the main reason for pumps damage.

Thanks for the input.

I have not tested this machine myself yet, but plan to do so in a few minutes.

Here is a pic for now . . .

That sure looks like HIGH PRESSURE HOSE for the Suction Line. Also, it appears it is reduced in size at the Tank Port. A couple of No-No's for any Suction Line.

Its location at the bottom of the Tank surely will help keep all the CONTAMINATION in suspension and give long life to the Pump.

Atleast the Fall weather will keep the Fluid Power Forums active for as long as it takes to get all the Home Made Log Splitters up and running.

Maybe Peter can suggest a Proportional or Servo Valve setup to take the shock out after the Suction problem is fixed.

Just kidding Peter!

Thanks for the input!!!

Yes that is 3/4" high pressure hose. The smallest that i goes is the 3/4" street ell (plumbing term) that goes in a reducer at the tank. It would seem then that running suction hose of whatever size the outlet in tank is 1" or larger, all the way to the pump is the best choice. Is that true?

I did get the unit running and split a couple 20" thick logs with it. It seemed to take a while for the 2nd stage to kick in on the pump which looks like a barnes 11gpm or similar. I had to bring the pressure down on it and back off several times before 2nd stage kicked in. Now it goes right in as soon as it hits some resistance. Must be the valve in the pump was sticking.

The brand new Honda GX160 that he had for it had a fuel supply problem (actually 2 of them). The hose was kinked, and then the carb had small aluminum fragments in it. (Yikes!!!) I have never seen that with a new Honda unit before. I got it all flushed out and it runs fine now.

Another question, where should a gauge be mounted to insure all is well?

Thought I would post a couple more pics . . .

Another

Last One

Comments are welcome . . .

I can post one with the engine and pump mounted if anyone wants to see it. If not I won't waste the space.

It appears the hoses from the valve to the cylinder are undersize for 16 GPM flow. That would be exagerated on the retract stroke when flow from the cylinders Cap End Port wold be flowing 1.2-1.3 times pump flow due to the differential area at the Rod End.

Ntice how much larger the Suction line and the Return line from the valve is.

I you had a pressure gauge in the pump line it may show pressure is above the Unloading Valve setting and that is the reason for the slow action.

The small line flow reduction effect is made worse if theunit has high viscosity oil due to its higher resistance to flow.

BTW the problem with use of pressure hose on a suction line is because pressure hose has in inner liner that is not necessarily vulcanized tightly to the outer pressure containing part of the hose. The outer hose construction is not leak proof is the reason for the liner. When pressure hose is used in a Vacuum situation the inner liner can collapse and cause restriction to flow.

Suction Hose is designed to handle vacuum without collapsing.

This message has been edited. Last edited by: Bud T,

"Another question, where should a gauge be mounted to insure all is well?"
Any place in the Pump Outlet Line is satisfactory. If you put a Shutoff valve before the Gauge you can keep it from seeing pressure continuously so it will last longer and be reading as if it were new when you need to check pressure.

You could also just remove it and plug the port. Then you would have no trouble reinstalling it when required.

better yet, a gauge quick coupler on the machine, and mating half on the gauge.

Flat faced SAE style can connect and disconnect under pressure only up to 500 psi.

Stauff/parker connnect/disconnect up to 5000 psi I think, and are what we use all over. About $15 per half, but I don't know a good retail source. Check your local Parker rep.

http://www.phionline.com/hqdiag.htm

k