GPM and hydraulic hoses....

[Volfandt]

Mowing the back field always tends to get me to pondering things. The constant sounds of the machinery working away coupled with very few distractions is the perfect conditions to cause this and I always look forward to whatever topic enters my brain housing group during these times
Today I got to pondering the longevity or the lack of longevity of the BX's power steering hoses, among other world changing thought
From reading this forum I've read of far too many power steering hose failures, commencing at around the 200 hr mark and yet a very small percentage of the other hoses such as those on the FEL and/or BH failing.
Granted they aren't worked as often as the PS hoses but they do seem to last alot longer than 200 hrs of use.

Two thoughts and a few questions come to mind about why.
1st thought is construction, Are the PS hoses made of different material(s) than the other hoses? If so why?

2nd thought has to do with the design. The BX23 makes approx 5.5 gpm and this hydraulic power is circulated thoughout all the hoses on the tractor.
This leads me to the question(s), Does the PS system require this much power to function?
My guess is that it doesn't. Now the HST, FEL and BH could use more so I tend to think that this is a compromise.
Would reducing the power to the PS subsystem only, increase hose life and not effect it's operation?
Can one subsystem on a tractor hydraulic system have it's power reduced without effecting the other subsystems?

I know that larger tractors have two or more hydraulic pumps and generally one is for the PS while the other provides power to the other systems. I wonder if the the reason is that this is the easiest ( or only way) way to provide differing pressures within the separate hydraulic systems on a tractor?

Volfandt

 

[MadReferee]

1st thought is construction, Are the PS hoses made of different material(s) than the other hoses? If so why?

Hydraulic hoses are made different. The implement design engineer specifies the type of hose to use. The most common hose is a 2-wire hose rated for about 3500-4000 psi. This is sufficient to cover most all tractor applications. There are plenty of cheaper hoses out there that are only 1-wire and 2000-2500 psi rated. These hoses should be avoided for tractor applications.

Hose diameter determines the amount of gpm the hose is rated for. For example a 1/4" hose is rated for 3.5 gpm maximum while a 3/8" hose is rated for 7 gpm max. Hard metal tubing is rated almost 75% higher for the same diameters.

Hoses fail for many reasons, but usually from fatique and/or weathering. Power steering hoses tend to be shorter and flex a lot and get plenty of abraision from being located where they are. I would expect failures to happen more often with them than with loader hoses.

2nd thought has to do with the design. The BX23 makes approx 5.5 gpm and this hydraulic power is circulated thoughout all the hoses on the tractor.
This leads me to the question(s), Does the PS system require this much power to function? My guess is that it doesn't. Now the HST, FEL and BH could use more so I tend to think that this is a compromise.

Probably not that much flow. But flow is usually not the culprit for hose failures. It's fatique or over pressure or weathering (see above).

Would reducing the power to the PS subsystem only, increase hose life and not effect it's operation?

Probably not.

Can one subsystem on a tractor hydraulic system have it's power reduced without effecting the other subsystems?
I know that larger tractors have two or more hydraulic pumps and generally one is for the PS while the other provides power to the other systems. I wonder if the the reason is that this is the easiest ( or only way) way to provide differing pressures within the separate hydraulic systems on a tractor?

You answered your own question. It's the easiest and probably the least expensive for this type of tractor application. Additional features like the multiple pumps will increase the cost accordingly. It is obvious that the Kubota engineers felt that the best cost effective way to implement power steering is to use the same pump for PS and implements.

If hose failures are really that common (we have no actual numbers to verify that either) then reqular maintenance procedure should be to change the PS hose and some point.

 

[Volfandt]

Thanks for the answers but they bring up a few more questions
(I need to figure out how to enable html code)

"Hoses fail for many reasons, but usually from fatique and/or weathering. Power steering hoses tend to be shorter and flex a lot and get plenty of abraision from being located where they are. I would expect failures to happen more often with them than with loader hoses."

I've owned and operated auto's for more yrs than I care to mention and I don't recall ever having to R&R a PS hose nor a tranny to radiator hose for that matter. These hoses are made similarly as the tractor's hoses, i.e. a combination of flex and rigid.
Wonder why do these hoses hold up better than those on the BX?

"If hose failures are really that common (we have no actual numbers to verify that either) then reqular maintenance procedure should be to change the PS hose and some point."

I've read of quite a few failures of the PS hoses on the BX's here on this board and the maintenance manual recommends to inspect and replace the PS hoses if necessary at 200 hr intervals.

Now these hoses aren't the easiset components to R&R and their cost is way higher than your normal maintenance replacement items, especially if one has to pay a mechanic to replace them. And to be truthful I'm quite surprised that these components seem to have such a limited servicable lifespan.

I'll be performing my 200 hr maintenance soon and I'll be removing the engine cowling inorder to give the entire tractor a thorough inspection along with the std fluid and filter changes. If I see any spot where the lines can be secured away from rubbing I'll do it then but knowing that I'll be operating on borrowed time from this point on I'll also be looking into what kind of replacement lines I can go with that'll hopefully give the same kind of longevity that other tractor brands and auto's enjoy.

Volfandt

 

[MadReferee]

I've owned and operated auto's for more yrs than I care to mention and I don't recall ever having to R&R a PS hose nor a tranny to radiator hose for that matter. These hoses are made similarly as the tractor's hoses, i.e. a combination of flex and rigid.
Wonder why do these hoses hold up better than those on the BX?

I had a PS hose fail on my old Mazda pickup at about 10 years. PS hoses on autos typically are not exposed to the elements and do not have flex issues.

...the maintenance manual recommends to inspect and replace the PS hoses if necessary at 200 hr intervals.

Now these hoses aren't the easiset components to R&R and their cost is way higher than your normal maintenance replacement items, especially if one has to pay a mechanic to replace them.

I guess Kubota engineers are aware of the life span of the PS hoses. These hoses should not cost more the $15 from any local source. Much less than say your filters. Replacement should be a rather simple job for the non-Kubota mechanic. If you can do your own filter replacement then you can surely do your own hose replacement too.

And to be truthful I'm quite surprised that these components seem to have such a limited servicable lifespan.

Why? Do you expect your radiator hose to last a lifetime? All parts have a lifespan. Due to the nature of this particular part's usage/location, it is 200 hrs. I don't see it as a problem especially since the maintenance procedure calls for inspection and/or replacement at 200 hrs.

I'll also be looking into what kind of replacement lines I can go with that'll hopefully give the same kind of longevity that other tractor brands and auto's enjoy.

You can always go to the local hydraulic shop and ask for a 4-wire hose or even a High Pressure Hydraulic Jack hose but those might only last the same amount of time due to the flex/environmental/location issues.

 

[Volfandt]

"I had a PS hose fail on my old Mazda pickup at about 10 years. PS hoses on autos typically are not exposed to the elements and do not have flex issues."

How many hrs would that correlate too? It's definitely more than 200...
I would venture to say that the pS lines on a vehicle with over 100K miles will have encountered worse elements than a tractor with 200 hrs of use.


"I guess Kubota engineers are aware of the life span of the PS hoses."
Hense my original question, do The "B", "L" & "M" series Kubota's require their PS hoses to be replaced at 200 hr intervals?

"These hoses should not cost more the $15 from any local source. Much less than say your filters. Replacement should be a rather simple job for the non-Kubota mechanic. If you can do your own filter replacement then you can surely do your own hose replacement too."

Simple is in the eye of the maintainer. That I have the ability to R&R these lines are beside the point, the fact that part(s) not normally associated with the vast majority most manuf's normal scheduled maintenance items IS included on the BX series.

FYI, I can R&R my oil filter in less than 3 minutes without removing any additional parts. The air filter in less than a minute. With the MMM mounted the hydo filter will take approx 15 minutes and the fuel filters in about 5 to 10.
I seriously doubt I can R&R the PS hoses in less than an hr, probably two or more and many other parts/assembly's need to be R&R'ed in the porcess, hardly a "simple" preceedure......

"Why? Do you expect your radiator hose to last a lifetime? All parts have a lifespan. Due to the nature of this particular part's usage/location, it is 200 hrs. I don't see it as a problem especially since the maintenance procedure calls for inspection and/or replacement at 200 hrs."

Who's saying a lifetime? Relacement of radiator hoses are included in ALL manuf's scheduled maintenance instructions on liquid cooled internal combustion power plants on self propelled vehicles. If I'm not mistaken PS hoses are not....

I'll have 200 hrs in less than 2 yrs. There have been many that have eclipsed this in a yr. I do not look forward to having to replace my PS lines every other yr hense the reason for looking for alternative/corrective action.

" You can always go to the local hydraulic shop and ask for a 4-wire hose or even a High Pressure Hydraulic Jack hose but those might only last the same amount of time due to the flex/environmental/location issues."

Thanks, when I need to cross this bridge, I'll keep those recommendations in mind.
Refer to question #2 in this post, if other tractors don't need to have their PS hose's replaced at 200 hrs, why the BX series?

Volfandt

 

[MadReferee]

By your reasoning, nothing should ever have to be checked or replaced. The BX series maintenance schedule, according to you, requires PS hoses to be checked/replaced at 200 hrs. What's the big deal? It's no different than if Kubota said to change all filters and all fluids every 50 hrs. That's the maintenance schedule developed for the BX model, be it good or bad in yours or anyone elses eyes.

The B2410/2710/2910 manual does not have any recommended interval for changing PS hoses. But, those models are not the BX models. Every model series has it's own quirks and maintenance issues. PS hoses just happen to be one of those that are associated with the BX series.

Refer to question #2 in this post, if other tractors don't need to have their PS hose's replaced at 200 hrs, why the BX series?

Now you are asking me to read into the heads of the Kubota design engineers. That's impossible. I would suggest that you ask Kubota directly as only they can give you the right answer. In the mean time, you should follow the manufacturers maintenance schedule to insure proper and continued operation of your tractor.

 

[Volfandt]

"By your reasoning, nothing should ever have to be checked or replaced. "

I don't know where you read that.
I AM questioning the inclusion of power steering hoses into the BX's, and apparantly only the BX series tractors, as items that needs to be replaced at regular and seemingly very short intervals as compared to other tractors.... Some of which don't even make any mention of PS hoses..

"Now you are asking me to read into the heads of the Kubota design engineers. That's impossible. I would suggest that you ask Kubota directly as only they can give you the right answer."

No, I'm not asking that at all. Again, where did you read this?
I AM asking for opinions and yours is noted.
Now to get back on track I'll refer back to my initial post.

"Two thoughts and a few questions come to mind about why.
1st thought is construction, Are the PS hoses made of different material(s) than the other hoses? If so why?

2nd thought has to do with the design. The BX23 makes approx 5.5 gpm and this hydraulic power is circulated thoughout all the hoses on the tractor.
This leads me to the question(s), Does the PS system require this much power to function?
My guess is that it doesn't. Now the HST, FEL and BH could use more so I tend to think that this is a compromise.
Would reducing the power to the PS subsystem only, increase hose life and not effect it's operation?
Can one subsystem on a tractor hydraulic system have it's power reduced without effecting the other subsystems?

I know that larger tractors have two or more hydraulic pumps and generally one is for the PS while the other provides power to the other systems. I wonder if the the reason is that this is the easiest ( or only way) way to provide differing pressures within the separate hydraulic systems on a tractor?"

Volfandt