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View Full Version : Making high pressure hydralic fittings



pcarpenter
07-14-2008, 03:40 PM
Edit-- Argh....while it seems you can edit your new thread, you cannot edit the title...so my typo must stay. And yes....I do know how to spell hydraulic :-)

I now have my Ebay Dake press frame back home and am working on it. I bought a 50T press cylinder to replace the cool Dake powerhead that's missing (a new one is over $2k from Dake by the way) and am on my way to fabricating a sliding mount etc.

I bought an air driven hydraulic pump and am working on an adjunct reservoir to supplement the one attached to the pump that is too small.

For those not familiar, presses like these usually use high-pressure hydraulics (up to 10,000 psi) which allows them to make a lot of pressure while keeping the cylinder size reasonable. Even so, the cylinder here is 4" OD and I am guessing about 3.5" inside. As such, it uses what is commonly referred to in the trade as "jack hose". This stuff is what is typically used with jack cylinders (porta-power applications etc.). I found an inexpensive source for the hoses, but seem to struggle to find fittings etc. Enerpac is the cadillac and sells quite a few, but its nothing to pay over $40 for one of their fittings. A gauge mount block is quite a bit higher than that, for example.

Is there any reason I cannot make these? I would think that 4140 for example would have quite a bit of margin. Simple NPT threaded adaptors I need could be lathe turned and threaded with a die. A gauge mounting block could be made from bar stock with cross-drilled and pipe-tapped holes.

Enerpac has a blurb at the top of one of their fittings catalog pages that tends to imply that even though the pressures are high, they should be able to be safely made:


Enerpac does not supply high-pressure pipe or tubing but recommends the use of cold drawn steel tubing instead of regular pipe in the following dimensions: In place of 1/4" pipe use 3/8" tubing with a 0.065" minimum wall thickness. For 3/8" pipe use schedule 80 as a minimum or 1/2" with a 0.095" minimum wall thickness. For 1/2" pipe use schedule 80 as a minimum or 3/4" tubing with a 0.135" minimum wall thickness.
All tubing wall thicknesses based on a 55,000 psi minimum tensile strength.

My only concern is with the strength of threads....ie are cut threads less safe and maybe these fittings require rolled threads or something??

Any of you hydraulics experts out there have any insight?


Paul

tattoomike68
07-14-2008, 04:00 PM
you can make them from solid steel or DOM tube. lathe cut threads are fine.

I think what they want people to not do is let some jackass use water pipe fittings to rig up some dangerously high pressures.

I worked at a combine factory making complete grape harvesters, bean harvesters and pea combines, we had a hydraulic area with every fitting you could ever want. I machined tons of big hydraulic parts.

A farm type tractor dealer/repair shop should be able to hook you up with some good quality nickle plated fittings at a better price. that way you dont have to stress over them being up to the task. they were made for what you want.

Some track hoes and other machines run 10,000 PSI systems, when a hose breaks there better be someone on the controls shutting it down or it makes a huge mess.

davidh
07-14-2008, 05:31 PM
make your adaptor if steel, drill and tap the pipe by hand and it will work very well. i fix and sell portapower cylinders and hoses and have made my own test equip for pumps and cylinder testing. good steel is fine. i do have enerpac fittings and stuff too but not any extra. . . use a pc. of 1-1/2 bar stock and drill thru and tap the sides for gages, connnections etc..... works great.
davidh

wierdscience
07-14-2008, 08:11 PM
Have made and ran a lot of high pressure tubing and fittings,steel tubing is fine,common cold rolled is fine for fittings so long as the minimum wall thickness is maintained.

Swage-loc fittings work good and aren't too bad price wise,of course the best option in any plumbing is the limit the number of fittings in the system.

Manifolds can be made from brass,steel or stainless,but for high pressure/high flow aluminum isn't a good idea as it errodes easily.