Line sizes for 25 gpm

skidsteer.ca · Jan 6, 2009

My hi flow nh ls 160 has a 15 or 24 gpm flow output.
When using it on the log splitter it runs up to 600 psi inlet pressure at wot, when the valve is in neutral.
The loader has 3/4 lines and the splitter valve are 3/4" ports, (rated 25 gpm flow) but the front couplers and 10' of hose to and from the splitter valve are 1/2". I guess this is too much flow for 1/2" plumbing?
What should the pressure be at? (as little as possible or is there a rule of thumb?)
Nh does have the larger 3/4 coupler on this loader as well, but it seems some other mfgs are running simular flow through the 1/2" flat faced couplers
Ken

Farmerford · Jan 6, 2009

Ken:

I can only guess without knowing more details of your plumbing, but 24gpm through 1/2"ID hose produces substantial pressure losses because the fluid is moving so fast (about 39'/sec) that the flow is not laminar (smooth), but rather turbulent. Turbulent flow incurs proportionally greater losses than laminar flow. Twenty feet of 1/2" hose with six 90deg adapters produces about 240 psi of loss (over 3 horsepower) through friction alone with ISO 32 fluid at 104deg F. If you have cold or more viscous fluid, toss in the additional pressure losses in the quick disconnects, valves, return line filter, other fittings, 3/4" hose, etc., you could easily have a 600psi loss. That means you are using nearly 8 horsepower just to push the fluid through the circuit, all of which is converted to heat in the fluid, hose, and fittings.

I don't know of any rules of thumb other than the typical recommendations for maximum flow rates in different kinds of lines: 20 feet/sec in pressure lines; 10 feet/sec in return lines; 4 feet/sec in suction lines. Of these, only the 20 feet/sec limit for pressure lines is related to keeping the flow from becoming turbulent. The design standards for the return lines reflect the desire to limit pressure buildup at the working device and valve due to lower pressure capacities in the return circuits of some valves and the case pressure limits on some hydraulic motors, as well as the desire to have the fluid moving somewhat slowly when it enters the reservoir to reduce foaming. The very low design standard for suction lines reflects the desire to avoid a significant vacuum at the pump inlet that causes cavitation (three psi of vacuum is considered the limit for many pumps, so even a short suction hose must be fairly large to prevent excessive vacuum).

You aren't hurting anything as long as the fluid does not overheat from the 15,000+ BTU of energy you are adding from the pressure losses. But you may be using a half-gallon or more per hour extra fuel due to the 1/2" hose alone. I suppose a few hours at today's fuel prices might pay for 20' of 3/4" hose.

Wayne County Hose · Jan 6, 2009

Remember too to look at the hose end of a crimp fitting. A 1/2" crimp fitting necks down to a little over 3/8".

kennyd · Jan 6, 2009

I don't know of any rules of thumb other than the typical recommendations for maximum flow rates in different kinds of lines: 20 feet/sec in pressure lines; 10 feet/sec in return lines; 4 feet/sec in suction lines.

There are two charts on THIS page that should help.

john_bud · Jan 6, 2009

I would for sure get some larger 3/4 hose on that machine. Cheap solution.

jb

skidsteer.ca · Jan 7, 2009

Its not just the cost of the hose its the 135.00 for the larger couplers too.
I spoke with my coupler supplier, they say 17 gpm for the 1/2" couplers and 36 gpm for the 3/4" I usually run the engine a bit slower @ 20 gpm for splitting (fast enough), but I also have a stump grinder that should be switched over to the large couplers too. Run that at WOT.

The smaller coupler on the loader t into the 3/4 line from the big couplers and then have a 90 to point them forward again. So in my splitter system there are 6 90's total that are 1/2" plus about 15' of 1/2 hose. The rest of the loop is 3/4"

The oil is 10/30 motor and the temps never gets above 50 f according to the temp read out in the loader. (that things got a good oil cooler, rarely see 120 even in the summer)

The pressure rarely sees 1000 psi when splitting.

I can see by the charts my flow is excessive for 1/2" hose

I'm just wondering how much the pressure will drop for the $200+ bill this will create. Wonder if I should consider a bypass loop on the cooler?
Thanks for your help
Ken

john_bud · Jan 7, 2009

I doubt the cooler is the issue, so bypassing it won't make much difference. However, it would heat the oil more - your oil is running too cool. Most run 140-160F and that's a GOOD thing as you want to get rid of moisture and heat does that.

J_J · Jan 7, 2009

Ken,

In order to get two different flows, on the aux circuit, is your pump a two speed pump, or do they use some kind of flow divider? Also, is the pressure the same for both flows.

skidsteer.ca · Jan 7, 2009

John
Yes I was thinking in terms of warming the oil not flow restriction. Maybe I can cardboard it over as the rad is a inch away, so long as the motor cools during other tasks, or just slip the cardboard in while splitting.
Even though the machine is parked in the shop its hard get the oil "up to temp" plowing snow or anything (brush mowing on a 80 degree day oil get to 130 or 140 tops)

Many guys run 22 weight hyd oil (not much thicker then diesel fuel)in other hydraulic systems here in the winter but I don't want to get into switching it. Never get 1/2 of it out anyway

Ken

skidsteer.ca · Jan 7, 2009

JJ
Its two separate gear pumps that combine the flow with an electric valve. They use a common relief so the pressure is the same either way, 2650 psi.

The hi flow pump is returned to the reservoir when not in use, and the electric valve diverts it into the "load check" plug in the main hydraulic valve just before the 3rd valve spool when hi flow is activated.
This way the 1st and 2nd spools (boom up/down and bucket tilt) only ever see the standard flow of 15 gpm. Any the aux hydraulics can have 15 or 24 with the flip of a switch.

Lucked out and picked the hi flow kit up off of ebay, it was made for the old NH/JD skidsteer and was NOS (new old stock)
We had to rework the mount for the pump and make a spacer for the crank pulley to get it to work.
My loader has a different engine but the frame and boom was the same.

My loader should have a tandem gear pump for this option, if the old belt drive pump ever fails I'll buy the tandem one then.
$400 and 3 easy days labour, it was a steal for a hi flow option
Ken