Are there hydraulic fittings that don't leak - possibly a stupid question

ewlsey · Feb 18, 2017

Is there such a thing as a hydraulic fitting that doesn't leak at all? I've worked on equipment with every kind of fitting in existence, double flare, single flare, o-ring, tapered thread, yore-lock, ferrule/compression, push-lock, hose clamp, barb, every style of hose crimping, ad infinum. Every fitting I have ever seen has the trademark dirt/grease/oil stain around it within a relatively short time. A machine like a forklift or a backhoe is just a rolling hydraulic leak.

So, my stupid question is why do these fittings always leak at least a little bit? Is there any way to stop it?

Scottl · Feb 18, 2017

In my experience they don't all leak but get dinged up when disconnected and reconnected over the years. I can't remember the company but someone makes tapered copper washers to help seal conical/flared fittings.

Dirt, scratches, and over or under-tightening cause most leaks IMO. I think many fittings are over-tightened and leak as a result.

kustomizingkid · Feb 18, 2017

Go on google scholar and look at all the patent for high pressure hose fittings and go invent a new breadbox...

Under normal operation they leak at a rate which is acceptable to most everyone everywhere. Or else they wouldn't be used everywhere.

Onepass · Feb 18, 2017

The ones that don't leak are on someone else's equipment. The ones that do leak are on your stuff and in an amount directly correlated to how difficult it is to get to !

projectnut · Feb 18, 2017

The only ones I know of that don't leak were literally a hose within a hose. I don't remember who made them but we used them in the Food industry. The inner hose was fitted with what ever type of fittings that were standard on the machine. The outer hose had SAE fittings and a sight glass. The hose and outer fittings were blind in that they weren't meant to conduct flow but rather only contain any leakage from the inner hose.

They were primarily used on lifts that dumped ingredients into mixers and hydraulically operated conveyors that transported finished product to the packaging machines. They weren't meant for mobile devices like fork trucks and end loaders because the double hose wasn't nearly as flexible as flexible as the standard single hose.

MC Parts Kid · Feb 18, 2017

I use a product call Leak-Loc. You can find it at most air conditioning supplies. I wipe male and female with laquer thinner until the rag stays white. I just put a little on the male face around the hole. The stuff really works great but with this and other goops. If it ain't clean, it will not work. Bob

Jashley73 · Feb 18, 2017

It always seemed to me that the 37* flared JIC fittings were the best, but ion Zero-Turn mowers, they use a type where there's an o-ring of the male flare, to provide an extra measure of insurance against leaks.

Like all things with fasteners though, I'd say the other part to leak-free fittings, is the proper torque.

atomarc · Feb 18, 2017

I've done hundreds of hydraulic connections on forklifts and machinery and have never had problems with leaking or seeping at the fitting. The fittings were always checked and cleaned, then tightened the proper amount, taking care not to over tighten.

Stuart

garyhlucas · Feb 18, 2017

Hydraulic is a french word. It means leak!

gustafson · Feb 18, 2017

any fitting can be mis installed in order to leak

brake fittings don't leak[1500 psi]

fuel fittings don't leak[2-150 psi]

because something can be done wrong does not mean it is not worth doing

ac fittings sure don't leak much oring or flare

Mud · Feb 18, 2017

I have lots of hoses and lines that don't leak, on trucks, earthmovers, machine tools, cars, motorcycles, even on antique cars, some in service for many years. It seems to me that the majority of leakage comes from the devices the hoses are connected to. Valves, cylinders, junctions, pumps, etc. The hardest to prevent seems to be from things with O rings in them.

Tonytn36 · Feb 18, 2017

Dynamic O-ring seals will leak by design. The amount is just very small. The microscopic pores of the surface they run against carries oil - in order to lubricate the o-ring face, so by design, they allow some amount of oil to go past the o-ring. The finish of the running surface determines how much.

Machines! · Feb 18, 2017

I do a lot of work with hydraulic systems in the 1500-3000 psi range. SAE O-ring boss fittings and JIC 37 degree flares will not leak if clean and in good condition.

I also maintain these systems and have found that NPT threads are fine but only if considered as single-use. The difficulties in clocking the fittings in certain orientations while still getting them tight enough to seal is the other reason people have lots of failures with NPT.

I use Discount Hydraulic Hose to get my fittings because the website layout is very intuitive; everything is grouped logically.

metalmagpie · Feb 19, 2017

My experience is limited. I rehosed an old ironworker. Previously all connections were NPT. I replaced those with ORFS wherever I could. No leaks.

metalmagpie

atomarc · Feb 19, 2017

Not to flog a dead horse, but I recently built a hydraulic press for a customer who is only one step removed from a NASA clean room.

While I did work with hydraulics for many years, I don't like them..when not done properly they certainly will leak, and an occasional blown hose is a nightmare.

Having said that..I'll enclose a picture of the valve and some of the plumbing on the 'clean room' press, and as mentioned above, I had Discount Hydraulics supply all the custom length hoses and fittings.

To date, not a drop has dripped from the press in the enclosed pix!

Stuart

DMF_TomB · Feb 19, 2017

hydraulic oil on some systems gets hot, the higher the pressure forced through a restriction will generate heat. i have seen hydraulic reservoirs get so hot the oil was boiling.
.
just saying a hydraulic system were oil does not get too hot has a greater chance of not leaking. when over 150F a lot of sealing compounds and rubber looses strength and sealing ability.
.
some hydraulic systems actually have a oil cooler on them to help cool the oil temperature down or the have a large tank with so much oil it can absorb the heat so average oil temp not that high

ewlsey · Feb 19, 2017

I was working on a pair of Mori Seiki ZL-45s. They have two hydraulic turrets, a tailstock, two hydraulic chucks (each chuck has two sets of jaws that clamp independently), hydraulic counterbalances, and probably other systems I forgot. They had two hydraulic pumps and a chiller. I would guess 20 solenoids and maybe 10 pressure regulators.

Those machines pretty much leaked everywhere. I spent days tweaking hose fittings and replacing little o-rings and it slowed it down a bit. The owners had pictures of the machines on the floor in Japan and you can see drip pans everywhere under the brand new machines.

Machines! · Feb 20, 2017

DMF_TomB said:
hydraulic oil on some systems gets hot, the higher the pressure forced through a restriction will generate heat. i have seen hydraulic reservoirs get so hot the oil was boiling.
.
just saying a hydraulic system were oil does not get too hot has a greater chance of not leaking. when over 150F a lot of sealing compounds and rubber looses strength and sealing ability.
.
some hydraulic systems actually have a oil cooler on them to help cool the oil temperature down or the have a large tank with so much oil it can absorb the heat so average oil temp not that high

This is important. If your system runs for a longer period of time than intermittently, it must have a heat exchanger. When the oil gets too hot, it will bake the o-rings and turn them brittle.

A terrible proposition when for example the heat exchanger on a 200 ton injection molding machine fails and now the entire system is compromised.

gustafson · Feb 20, 2017

atomarc said:
Not to flog a dead horse, but I recently built a hydraulic press for a customer who is only one step removed from a NASA clean room.

While I did work with hydraulics for many years, I don't like them..when not done properly they certainly will leak, and an occasional blown hose is a nightmare.

Having said that..I'll enclose a picture of the valve and some of the plumbing on the 'clean room' press, and as mentioned above, I had Discount Hydraulics supply all the custom length hoses and fittings.

To date, not a drop has dripped from the press in the enclosed pix!

Stuart

View attachment 191488

What the hell, the one angled hose is just wrong! replace it!!

sorry, just kidding, looks great

I've had a plumber who could not stand a pipe running diagonal and cut it out and replaced it, love that guy.

Are there hydraulic fittings that don't leak - possibly a stupid question

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