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Hydraulics Issues

jic hose replacement hydraulic filters crimp hydraulic pressure

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#1 dodge trucker OFFLINE  

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Posted November 23, 2014 - 08:56 PM

I thought I'd posted a thread on this topic  earlier today, and now can't find it....

sorry for the length of the post, please bear with me....

 

anyway I am working on the hydraulics on my Ariens GT 19 sealing up the leaks, and am at a point of needing/making new hoses.

I got this tractor with one hose completely blown, looked like it may have rubbed thru on the drive shaft.
I had a local shop make me a new one then watched a 2nd (different)  hose blow within 15 min of running in the garage on a jack (so the system was under minimal stress, not doing any real "work" at the time) I had "just" gotten all the air bled out of the system, when the 2nd hose blew its pinhole.  Considering how rusty the inner metal mesh was on that original blown hose,  I figured the rest were not far behind... time for all new hoses.

I have some questions related to hydraulic hoses--some of which I used to know the answers to, back when I worked at the steel mill and had my turn in the hose room--- but have forgotten the answers to.

 

the original hoses were 1/4" with 3/8" JIC threaded fittings.

that 1st hose I had made at the hose shop, they made that same way as original/ but the fluid hole within the  crimp fittings themselves that they used,  was about 1/2 the size of the original/ which on the originals, was same diam as the hose itself. Could that smaller passage in the fitting on the replacement hose, possibly have restricted flow enough to jack up pressures "behind" it in the system to cause the 2nd hose to blow?  (I am thinking 30 years of age did have something to do with it)

higher pressure = higher temps

 

Being that the threaded couplers are 3/8 JIC, my buddy who still works at the mill and is getting me a favor done on making me  these hoses,  used 3/8 hose to go with the 3/8  thread size. (after I had issues installing them the 1st time, he then said they do have 1/4 crimp fittings with 3/8 thread like original, if I'd rather).... I figured bigger hose= more flow volume and = cooler running system... will the larger hose also reduce system pressures?  (I am thinking "not," but unsure) the 3/8 fittings for 3/8 hose sure have larger openings WITHIN the fittings, than the fittings on the hose from the hose shop. I know too that parker fittings will not work on a Weatherhead crimper machine, and vise versa the one from the hose shop didn't look like Parker fittings.... not sure what brand they use

 

 

I am having to shorten a couple from original due to the 3/8" hose not being as flexible as the 1/4, and not "tucking" into the frame and bending around obstacles as easily  and also wanting to hit the driveshaft, or mingle with my new fan. some of the old hoses did seem longer than they needed to be, anyways// and I was wanting to shorten them anyhow from original equip (especially the 2 to the lift cylinder) even if I were to go back with 1/4" hose, to tuck them in and better keep them out of harm's way ...  What bearing does length have, on pressure within a system?  (I know, too short can be bad too if there is strain/pull on them// but there won't be, in this case)

I am thinking as in electricity, where they tell you to go up one gauge size wire if your circuit is over a certain length,  but being as how my longest hose on this setup is about 32" long, that point may be moot... but thought I'd ask anyway... it may do someone else some good, down the road.

I do not care about it being a museum piece and "exact replica of original" as these are hidden by the seat pan anyways and not seen unless the pan is flipped up... I just want it to "work" and NOT leak.

 

 I may have asked this in another thread.

  It depends on where you look, interchange info on hydraulic filters for this machine varies. Some cross it over to the same oil filters that my Dodges and jeeps take on their engines; others cross to specific "hydraulic" oil filters in the same respective brands! . The specified fluid on this tractor is motor oil anyway, so what difference (if any) would it make if I used an "oil" filter or a "hydraulic" filter?  I have a Fram PH8A on there at the moment, it seemed to work just fine on there,  til the 2nd hose blew a pinhole. 

 

Instead of looping the feed hose from the hydro to the control valve like a question mark around the fan,  (3/8 hose can't be bent to the same radius as 1/4, and the crimp fitting itself is too rigid to miss interference with the hydro fan)  I had him put a 90* crimp fitting on the hydro end of that hose which will allow me to reduce that hose to almost 1/2 its original length)  will that 90 on there hurt my feed pressure to the valve?  I'm thinking that with the larger ID of the new hoses allowing more volume, that will make up for putting a 90* fitting where there never used to be one....does this sound right? 

 

Oh well/ as long as this tractor sat before I got it, and coming to me with what appears to be the original factory hydraulic filter, running it with new oil for 15 minutes then having to dump the system again to replace the hoses may serve well as a "flush" of the system.... that can't hurt.

 

 

 



#2 superaben OFFLINE  

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Posted November 23, 2014 - 11:11 PM

I'm no hydraulic engineer by any stretch, but the length of your hose would not change the pressure.  It can't, fluid does not compress, so it will keep the same pressure all the way down. 

 

A longer or shorter hose will change the reaction time it takes to change fluid direction and speed.  Nothing really to be concerned about, but it was something I notice on a high load situation (hydrostatic tractor with hydraulic driven attachments for example) or a low volume situation.  It takes x amount of time longer to fill a run of hose that is longer than the original.  I know this is true on zero turn mowers, the hoses running from the drive pumps to the drive motors have to be the same length or else you will not accelerate straight.

 

As far as 1/4 hose versus 3/8 hose.  The main thing is volume.  A smaller hose will put more stress on a pump during high oil volume demands, since the pump has to work harder to keep up.  Restrictions will reduce volume, and it will increase pressure behind the restriction.  Possibly the system might have to blow relief often. 

 

A good hydraulic fitting should have the interior pretty darn close to the interior of your hose.  Can't be exactly the same, but it should be close.

 

Ben W.


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#3 Bruce Dorsi OFFLINE  

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Posted November 23, 2014 - 11:31 PM

I am certainly not a hydraulics expert, but I'll offer some of my thoughts.

 

1) Additional hose length will increase friction loss through the hose.    ....However, those friction losses are insignificant in your case since the fluid flow (gpm) is low. 

 

2) Small hose will not allow as high a flow rate (gpm) as a larger hose,  but again, this should not be a factor in your relatively small hydraulic system.

 

3) In general, the flow rate through a system is determined by the hydraulic pump displacement times the pump rpm, and is rated as gallons per minute (gpm).

 

4) Hydraulic filters are usually in the return line to the reservoir or between the reservoir and pump inlet.  ....In these locations, the filter is not subjected to high hydraulic pressure.  .....Too small a filter, or a dirty filter can cause restriction to flow, which is not good.  ....Since your system uses motor oil for hydraulic fluid, the   Fram PH8A should be acceptable for your system. 

 

5) I have noticed smaller diameters on some fittings, also.  ....Depending on flow rate (gpm) of the circuit, the smaller holes may not be a matter of concern.  ....However, fitting manufacturers size their fitting passages to be compatible with the hoses used. 

 

    For example, a fitting for a 3/4"  i.d. hose would never have a 1/4" hole, but a 1/4" hole would be acceptable for use with a 3/8" i.d. hose.

 

 6)  At 1200 psi, a spray nozzle with a .040" orifice can pass approx. 3.75 gpm.   .....So, you can see that a 3/16" or 1/4" hole in a fitting can still pass the relatively low gpm in your tractor's system.

 

7) I don't believe a 90* fitting will add significant restriction (or pressure) in your application.      


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#4 dodge trucker OFFLINE  

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Posted November 24, 2014 - 07:15 PM

I am certainly not a hydraulics expert, but I'll offer some of my thoughts.

 

5) I have noticed smaller diameters on some fittings, also.  ....Depending on flow rate (gpm) of the circuit, the smaller holes may not be a matter of concern.  ....However, fitting manufacturers size their fitting passages to be compatible with the hoses used. 

 

    For example, a fitting for a 3/4"  i.d. hose would never have a 1/4" hole, but a 1/4" hole would be acceptable for use with a 3/8" i.d. hose.

 

 

Well, looking at the ID of the hole within the fitting on all the old hoses vs the ID of the hole in the one that I had made at the hose shop, they used 1/4" hose with 3/8" fittings just like original;  but their fitting's holes within,are about 1/2 the size of any of the old hoses' fittings. I will keep that one as a backup/emergency spare, but am not gonna run that one unless I HAVE to. I'm talking on that one newly made hose, barely being able to get a pencil lead thru the fittings vs almost being able to pass a whole pencil thru the old fittings. big obvious difference.  that's why I'm glad to have someone I know that knows what they are doing, that has access to a hose crimp machine at his work....

that new hose with the too-small opening in the fittings went from the steering column to the steering cylinder (power steering!)



#5 dodge trucker OFFLINE  

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Posted November 24, 2014 - 07:17 PM

 

 

A good hydraulic fitting should have the interior pretty darn close to the interior of your hose.  Can't be exactly the same, but it should be close.

 

Ben W.

this is about how I was thinking it should be.



#6 TUDOR OFFLINE  

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Posted November 25, 2014 - 07:09 AM

The flow rate determines minimum hose size required. For mobile hydraulics, 1/4" hose is adequate for up to 6 gpm. Most GT hydro powered implement lift systems have a flow rate up to about 3 gpm.

 

Line loss from length or number of fittings is minimal on GT systems. That would be a slightly different story on a 50 gpm, 3000 psi system with 60' long, mimimum diameter hoses.

 

Space available is restricted on tractors with the result that minimum hose sizes are used for hydraulcs. Quarter inch hoses can handle every hydraulic attachment on most GT's up to a log splitter that uses the 6 gpm FEL auxilliary pump. (Case GT's are in a world of their own with the 9 gpm hydraulic drive.) While smaller hoses could be used for a hydro implement lift system, that is the only place that they could be used. Industrial hydraulic system flow rates for a given hose size are smaller, but space for larger diameter hoses is rarely an issue.

 

Heat generation is a given with hydraulic systems. It is also necessary to get the most out of the system. Water contamination won't drop out of suspension unless the system is operating at 140° F or higher. The common temperature for testing the specifications for pumps and motors is 180° F. A system that operates at over 190° F needs a cooler. A system operating at sub zero temperatures is very sluggish and requires higher pressure just to push the fluid through the system until it warms up.

 

Standard practice is to use 1/4" hose with -6 (3/8") terminations and fittings. That is sufficient to reduce the minimal restrictions caused by 90° and other fittings.

 

Oversizing hoses on GT's brings minimal, if any, benefits to the machine. It does beat up on the owner's pocket book quite well.

 

This covers the high points for the OP's original questions. Some of the many points expressed, while valid for laboratory purposes, don't really have a bearing on the original request for information on the common practices used in the field. I may have missed a few that deserved comment. Sorry!


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#7 dodge trucker OFFLINE  

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Posted November 27, 2014 - 10:02 PM

ok, got all new hoses on my GT 19.  I shortened up the ones from the control valve to the hydro and both to the lift cylinder  from OEM configuration, because I could not loop them forward and around the fan, like the old ones were, on account of using 3/8 hose to match the 3/8 fittings/ besides the price I got them done for, could not be beat.(original was as mentioned above 1/4" hose, with these 3/8 JIC thread size) also had him make me up another to replace the one, 1/4" with the less-than-pencil-lead sized opening in the fitting that I'd had made at the hose shop. the 3/8 hoses sure do not bend like the 1/4 ones did.... my buddy used 4000 PSI rated Parker "no Skive" hose. should be more than plenty of pressure capacity, hopefully that solves the hydro leaks for good.

 

I did have to put a 90 on the hose from  hydro end of the hydro to control valve  but I was also able to shorten it by  about double..

 

now to mount the gas tank back in there (may have to fab up the straps) re bleed it, then tube the front tires, and hopefully mount the snow blade.


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