Hydraulic question.

jplambs · 19th November 2012, 08:42 PM

I'm almost finished building my new 40' auger and as I get down to the final few bits and pieces I think I may have been a bit to clever for my own good.

The auger works on a scissor lift principle and when it is in the lowered position the hydraulic oil tank is currently a bit lower than the inlet to the hydraulic pump. The question I have for those in the know is, is the pump going to provide enough suction to draw oil from the tank when it is in the lowered position or will I have to relocate the tank?

I'm using a v-twin briggs with the pump directly mounted to a bellhouse/clutch.

Cheers.

**justinc** · 19th November 2012, 10:03 PM

MOST pumps require a pressure head to work effectively without cavitation. How much work / flow will the pump require at the position where the tank is level or lower?

If any more than a light load I think you will have a problem.

JC

**sdt463** · 19th November 2012, 10:22 PM

I have a log spliter that I built that has the pump about 30 cm above the tank and it has never been a problem. If you have already built it give it a try and see how you go.
Dave

**Blknight.aus** · 19th November 2012, 10:55 PM

it will only be a problem if you start approaching pump stall where the suction of the pump drops off because theres too much pressure on the other side of it.

IT wont self prime and once it starts cavitating it'll keep doing so until you get to a high flow low pressure situation on the output of the pump.

**Rick1970** · 22nd November 2012, 03:22 AM

True that pump inlet below oil level is prefered, but as long as its not a stupid height above it and your hose (suction) is appropriately sized it will be fine.

jplambs · 24th November 2012, 08:06 AM

Thanks Guys I think that answers the question, sorry I haven't been back on, we have been tied up fighting fires for most of the week.

When the auger is raised, and not by a lot, the tank rises above the pump. That is the position that it will be doing most of its work in so it sounds like it should be fine.

Cheers.

**Nova** · 26th November 2012, 07:11 PM

You had better drop it into my place and make yourself another one without this problem. I should be able to find a use for it.

Thunder out your way again tonight? Making me nervous again. How did you fare last week?

Cheers,
Nova

jplambs · 29th November 2012, 12:05 AM

Steady on, its only taken me 18 months to get it to this stage. Although I suppose if I tried again I'd know what I was doing this time. ;-)

Yup there was a bit on Monday, we fared ok but I spent three days south of here looking after a fire at Pitlochry last week, it took out about 300 Ha's all good though now.

**Gerokent** · 29th November 2012, 10:23 AM

"MOST pumps require a pressure head to work effectively without cavitation."

Just being pedantic, but this is aeration. Cavitation is usally caused by restriction in the inlet, or to thick or cold oil. Both cause damage. Aeration will cause faults further into the system (jerky movement, overheating the oil, ect), whereas cavitation usally only affects the pump.

**Blknight.aus** · 29th November 2012, 05:30 PM

to be really pedantic...

its cavitation..

areation is when air is introduced to the oil by means of an air leak on the suction side of the pump, in the pump or by venturi effect at joints during high flow low pressure operation.

cavitation is when micro bubbles are formed in the pump that immidiately collapse. they're bad for a whole host of other reasons.

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