Return line size

250quality · Dec 9, 2011

I was given some advice to up size the return lines on my processor to 1-1/4.
I just finished putting on 2 new valves, a 3 spool with power beyond and an auto cycle downstream from that. Both valves have 3/4 ports on the return side as well as my cooler where they will run to.
Does it make sense to upsize the return to 1-1/4 anyway and if so can I use regular black iron plumbing fittings for the return as there should be little pressure there and it would save me a bunch of trips to my hydraulic supplier.
Thanks
Brian

KYErik · Dec 9, 2011

Black iron is good up to at least 3-400psi so using it on a return line will be fine.

Several years ago, I even used some isolated black iron bushings and 3/8 elbows for a low pressure (1000psi) hydraulic system and had no issues with it- though I know it was a risky application (I placed them in locations so that I would be shielded if they failed).

That said- if the return port is only 3/4 inch- I don't see the benefit in going up to 1.25 inch- unless the return line has lots of twists and turns which would slow flow significantly.

J_J · Dec 9, 2011

Could use some 1 in hose for flex, and pipe for the rest of the return, How about the return filter, is it 1 in ?

250quality · Dec 9, 2011

No its 3/4 as well.

oldnslo · Dec 9, 2011

What flow rate are you operating at?

What will the surge flows flows be and for what time duration will they last?

How long of lines will there be?

3/4" schedule 40 black pipe is rated 16.5 GPM at 10 feet/second

1" schedule 40 is rated at 27 GPM at 10 feet/second

Roy

250quality · Dec 9, 2011

What should the return pressure be or will it vary per system?

J_J · Dec 10, 2011

If the fluid is flowing through a return filter and it is new or clean, there should be very little pressure on the return/tank port. You could put a low pressure gage on the filter and monitor if concerned.

Discount Hydraulic Hose · Dec 10, 2011

KYErik said:
Black iron is good up to at least 3-400psi so using it on a return line will be fine.

I can't speak for all black iron, but we sell some malleable black iron fittings on our site, and these fittings have a pressure rating of only 150 PSI.

Black Malleable Iron Pipe Fittings > DiscountHydraulicHose.com

I would definitely check the rating for any black iron pipe and fittings you are using before assuming that they will handle 300 or 400 psi.

oldnslo · Dec 10, 2011

250quality said:
What should the return pressure be or will it vary per system?

It will vary with each system. I presume you are using a gear pump on your wood processor so there will be continuous flow in the return line. I would try to have less than 50 PSI measured at your valve tank port.

Roy