Hydraulic Hose

[malis]

Im working on a project that basically consists of runing number 6 size hoses thru a 180 deg. bending cable track with a bend radius of 4" and total length of 336". The hoses are clamped at both ends of the track and the working pressure is 2800 psi. My issue is that the hoses shrink to the point that they create friction on the inside of the track and wear thru as the machine cycles.

Below are the parameters I must meet.
1) Wire Reinforced
2) High abrasion resistance
3) Less than 1.2% shrinkage or alternative way to ease the shrinkage.
4)Greater than 3000 psi WP

Due to the loactaion and space requirements I cant over stuff the track or add a loop. The expansion has to be taken up by the hose or some axial expansion fitting

Any suggestions?

 

[MadMango]

You might want to search Google for Jackson Industries. They have a line of PTFE hoses with stainless steel braiding, S-6 "dense-pac" hoses have a 5kpsi wp. Not sure of shrinkage.

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Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[XELR8]

Use 2-90-elbo's fittings for the 180 loop. Offset each hose so they don't touch.

 

[MikeHalloran]

If you're using generic cable chain, that may be your problem. Igus, in their application selector,

http://igus.bdol.com/echain.asp

specifically asks if you're using hydraulic hoses or not. I assume it's because high pressure hoses, even without wire reinforcement, fight back a lot harder than an electrical cable when you try to bend them.

Also talk to your hose supplier; they may have something with a more chafe- resistant cover.

Short- term, that's what I'd do; add chafe guards to the hoses wherever they contact the carrier. Corrugated split wire loom might help. Secure it with ty-raps in between contact zones.








Mike Halloran
Pembroke Pines, FL, USA

 

[MarkTEng]

My concern is that your bend radius is to tight for a -06 hose. From my information (see also

http://hydraulics.goodyear.com/cfmx/web/hosesearch/hose_family_results.cfm?hosefamily=GR12

) the min bend radius is 5 inches for a -06 hose. You will cause damage to the hose with a 4 inch bend radius. My safe rule of thumb for any hose is to do a manual rap (like a garden hose) and visually inspect the hose for it's natural bend radius.

 

[MintJulep]

Mount an integrated hydraulic power pack at the point of use and run electric to it.

Wire is much less likely to fail, and if it does, it won't spray hydraulic fluid all over.

A host of other potential advantages too.

 

[malis]

To clear up some issues this project is one that i'm fixing from a previous engineers bad design.

1)Cant change to any other type of system.
2)Their are lots of -06 hoses with less than 4" bend radius

Really just need some suggestions on hoses that could meet the critera above. So far the vendor has come up with some that meet all except the shrink rate.

Thanks for all the sugestions, but still looking for the right solution.

 

[Mandrake22]

Parker advertised some "abrasion resistant" hose about a year ago. Take a look there.

 

[BillPSU]

You may want to look at the non-conductive hose as it can have a polyurethane outer covering which may be better for this application. Parker makes one of the best 518C.

http://www.parker.com/PARFLEX/4660 SINGLE PDF/518C.PDF

 

[MikeHalloran]

The bend radius seemed tight (for a wire- reinforced hose) to me too, but I figured it was already cast in stone. Maybe you could use two -04 hoses.

If the hose was actually shrinking under pressure, you could just install it with more slack. I suspect that it's just trying to straighten itself, and chafing against the inner side of the bend in the track because it's not following a path concentric to the track bend center.

Actually, the bend radii limits for the hose are given for installation in free space, or over a large mandrel. Inside the track, the hose is being bent over what amount to edges or crossbars, so the _local_ bend radius is governed by the radius of the bar or bushing or whatever actually contacts the hose.



Mike Halloran
Pembroke Pines, FL, USA

 

[malis]

Mike you have hit the nail on the head as to what is happening. But my delima still stands as to how I can correct the issue. I cant change to any other size of hose nor can I just simply add slack. Secondly I dont understand why everyone thinks that the 4" bend radius is to small. Parker has pages of wire reinfoced hose with radius in the 2-3" range?

The problem really comes down to controlling the shrinkage when the hoses are pressurized so that when they are moving thru the radius that they stay on path with the track bend radius. Has anyone ever heard of an axial slip ring fitting for hoses?

 

[diskullman]

Fortunately, Parker has introduced some newer hoses with tighter bend radia, and good working pressure.In my youger days at a Parker distributorship, we steered everyone that needed a 2 wire hose to the 301, so we could hold down our inventory. This hose has a 5" bend radius &4000PSI working pressure. Parker also offers a 431 hose with a 2½" bend radius & 4000 working pressure, or a 471TC hose (tough cover) with a 2½" bend radius & 5000 working pressure. The fun part is finding a distributor that stocks these, and has the proper dies for crimping the fittings. They can order the hoses assembled from Parker, if you have the time.

Russell Giuliano

 

[MikeHalloran]

Maybe you could put the hose through a rigid metal tubing u-bend, and assemble that into the carrier. You'd need to keep it greased inside and out, though. I've done something like that on a smaller scale with teflon tubing inside stainless u-bends, but the cycle rate was pretty low.

Closest dry approximation is arcuate shoes on the inner face of the track elements, to distribute the load.

Incidentally, I suspect that if you set up a static test with a u-bend section of track and a hose inside, you'd be surprised at the force exerted on the track by the hose. Maybe just insert a pencil between the hose and the track and slowly pressurize the hose and see what happens.

Or take a piece of hose in free air, pressurize it, and try to bend it to a 4" radius with your bare hands.

If you could somehow link a big pulley to the bend in the cable track, you could route the hose over that, and keep axial tension in the hose, and control the bend radius. I can see it, a little fuzzy, in my mind. [Caution: I have an eidetic mind, and can visualize things are not physically realizable, in such a way that they are not distinct from things I have actually seen.]



Mike Halloran
Pembroke Pines, FL, USA

 

[BillPSU]

One of the solutions used in extendable boom aerial devices and digger derricks is sometimes a welded hose. Multiple hoses bonded together to form a ribbon hose. In one case because electrical wires were required an addition hose was used as a sheath for the wires. You can sometimes use these without a carrier. These ribbon hoses are made from hoses with thermoplastic covers.

The bending action that Mike describes is exactly what happens and causes hose failure at the cross braces. How full is your hose carrier?

 

[sreid]

Have you contacted Aeroquip? In my mind, the world leader in high performance hose.

http://www.aeroquip.com/