hydraulic hose advice

[Mike Adams]

When I replaced my engine some 4 years ago (it has a hydraulic drive) I needed to replace/extend some of hydraulic hoses. It has all been fine but this year I noticed two of the new made up hoses have started to weep at the crimped part of the terminations and not at the screw on joint while the other pair, which were purchased from a different supplier, are fine. Both sets are subject to the same working pressure.The hoses are from different manufacturers but the same working pressure/spec but the ones that are leaking don't seem to be crimped quite as hard. I guess the only option is to replace them. Unfortunately I purchased them through Ebay. Any recommendations for a good supplier or brand or could they be re-crimped now? The pair that have failed are not subject to any movement  are not subject to any movement whilst the other pair that are good connect the static control valve to the engine pump which is subject to engine vibration.

[BEngo]

Re-crimp is unlikely to be effective. If they have failed the crimper  was probably set up wrong, and the fittings will be work hardened now so won't squeeze down as far as they should. 

 

Ring your local Pirtek ( or equivalent) van.  He (she) will make new ones on site or, if you have all the size and end fitting details,  can make them up and drop them off for you to fit.  That might be cheaper as it will be a fill in job not an emergency  call out to site.

 

N

[Tony Brooks]

Virtually every major town will have suppliers who make them up to order for  agricultural and construction equipment, so Google is your friend. Some will  make up on site.

[ditchcrawler]

1 hour ago, Mike Adams said:

When I replaced my engine some 4 years ago (it has a hydraulic drive) I needed to replace/extend some of hydraulic hoses. It has all been fine but this year I noticed two of the new made up hoses have started to weep at the crimped part of the terminations and not at the screw on joint while the other pair, which were purchased from a different supplier, are fine. Both sets are subject to the same working pressure.The hoses are from different manufacturers but the same working pressure/spec but the ones that are leaking don't seem to be crimped quite as hard. I guess the only option is to replace them. Unfortunately I purchased them through Ebay. Any recommendations for a good supplier or brand or could they be re-crimped now? The pair that have failed are not subject to any movement  are not subject to any movement whilst the other pair that are good connect the static control valve to the engine pump which is subject to engine vibration.

I had mine made up at a local hydraulic company in Lowestoft where I live

[Mike Adams]

Thanks for the comments.

I think I will order a pair of new hoses as I don't fancy the idea of one coming apart!

[BEngo]

13 hours ago, Mike Adams said:

Thanks for the comments.

I think I will order a pair of new hoses as I don't fancy the idea of one coming apart!

Hydraulic hoses have a finite life.  If they are not too dear, might be worth having a spare set. 

 

N

[jonathanA]

I found these guys helpful and reasonably priced for hydraulic stuff, if you have a way to have them posted to you 

 

https://www.ebay.co.uk/itm/125882313212?hash=item1d4f2ba9fc:g:CosAAOSwCr9iD5Nr&amdata=enc%3AAQAIAAAA4Nh6F%2FOLxYt0e91y0sLpWUBFGIsjOZBxylbceVutUaHRdd37a2EvjmVvtOiaLwct93asb6C5bpGEwB7XZbNuIO1RznnXtFyjNHsrJeR7Xtjeegzk2MmZT4tgsmloQpiUsMQn1ALjbdrXAOrxhv8xL94RCJk6HKws5lIaKZsxrJfvW7Pfc%2Ftw%2BUlik9CvKLDYqnd6Gyu7PJSI4E3ib%2B38E5ft%2Fyo98253wTVjs5J8zdSmbwej5SI%2Bedz5xu%2BkrU9PlDeeNXzaCWARuGGsRy%2FkdnO9q%2Fx6H0tD%2FEMiBbLUyht0|tkp%3ABFBM_vSM4IBi

 

no connection other than as customer, but you do need to know what size/type of fitting you need - pretty sure if you sent them some photos they would be able to help (or some one on here would identify for you)

 

(mine were for a tractor not a boat btw) 

[agg221]

9 hours ago, BEngo said:

Hydraulic hoses have a finite life.  If they are not too dear, might be worth having a spare set. 

 

N

Hydraulic hoses can be very expensive. Fortunately, there are couple of factors which work in favour of marine hydraulic drive owners - one is that they are usually running them at a very low pressure compared with design pressure (ours are at about 300psi on 5000psi rated hoses) so when they fail it is by bulging rather than immediately bursting and you do get fair warning. The second is that they usually see no UV so do not perish at anything like the same rate. This means they can last a very long time, over 20yrs if properly made. Unfortunately the weak point remains the connector.

 

One piece of advice I got recently was to get most of the hose replaced with an appropriately rated steel pipe. There is no risk of internal corrosion (permanently oil filled) so if well maintained the weak link remains the hose. You then have much shorter hoses which are lot cheaper to replace and far less awkward to store (and much easier to fit as it is no longer like wrestling with a large python in a small box. In terms of storage, it is a good idea to keep a spare, the same length as your longest hose, as you can then fit it to whichever one fails which gives you a reasonable time to get the replacement set made up.

 

Alec

[john.k]

Every brand of hose has dedicated terminations............some cheapskate hydraulic shops try to mix and match hose and fittings they get a auctions and liquidation sales ..........In general ,the crimping machines are dedicated to one brand ,and are set to hose sizes ,and cant be altered...........the obvious solution is to demand Frederick Duffield re usable fittings ,then you can buy the bulk hose and reuse the fittings....................if you havent guessed ,hydraulic hose supply is a massive ripoff ,with franchises taking massive fees and markups.

Incidentally,you can also get stainless steel hydraulic pipe.,if corrosion is a worry.

[Chris Lowe]

Another mobile repair company that you could call is Hydraquip .

When I worked in the design department at Niftylift, most of the hoses we used came from Stauff.

[Mike Adams]

7 hours ago, john.k said:

.the obvious solution is to demand Frederick Duffield re usable fittings ,then you can buy the bulk hose and reuse the fittings.............

I thought of buying some of those, or at least something similar but as the pressure can go up to 4000psi on 3/4 hose I wasn't sure if they would handle it. On further reflection it is the two fittings on the output of the control valve going to the stern and drive motor that are leaking the worst perhaps going too quickly from ahead to astern and vice versa causes a bit of a pressure surge at that point if the propshaft has some inertia the two pumps could be operating against each other for a short time. I think the PRV is on the other side of the control valve. Perhaps I need another PRV in the circuit?

[Tony Brooks]

7 minutes ago, Mike Adams said:

I thought of buying some of those, or at least something similar but as the pressure can go up to 4000psi on 3/4 hose I wasn't sure if they would handle it. On further reflection it is the two fittings on the output of the control valve going to the stern and drive motor that are leaking the worst perhaps going too quickly from ahead to astern and vice versa causes a bit of a pressure surge at that point if the propshaft has some inertia the two pumps could be operating against each other for a short time. I think the PRV is on the other side of the control valve. Perhaps I need another PRV in the circuit?

 

On all the systems I have seen, the PRV is effectively between the pump and control valve, even if it is in the control valve casing.

 

Also, all the systems I have seen only have one pump. It is the control valve that reverses the flow through the motor.

 

I agree that going from ahead to astern too quickly might produce a pressure spike, but the PRV should damp that before it got high enough to "blow" a hose. all our hose failures were caused by abrasion that went unnoticed.

 

Where did you get the 4000 psi from? Do you have a gauge?

 

[Mike Adams]

Both the pump and motor are interchangeable, they are both bent axis devices so can act as pump or motor. The existing PRV is between the the pump on the engine and the control valve. So if you turn the propeller the motor on the shaft acts as a pump. So if the shaft carries on for bit after you change direction the two pumps(one being the motor)could be opposing each other for a short time possibly? I obtained the pressure rating from the speed ,hp and pump/motor characteristics. I may be taking rubbish here as I not by any means a hydraulics expert.

[Tony Brooks]

3 hours ago, Mike Adams said:

Both the pump and motor are interchangeable, they are both bent axis devices so can act as pump or motor. The existing PRV is between the the pump on the engine and the control valve. So if you turn the propeller the motor on the shaft acts as a pump. So if the shaft carries on for bit after you change direction the two pumps(one being the motor)could be opposing each other for a short time possibly? I obtained the pressure rating from the speed ,hp and pump/motor characteristics. I may be taking rubbish here as I not by any means a hydraulics expert.

 

That sort of makes sense, but we never has signs of that on the hire fleet. You can bet many customers treated the direction change harshly. I admit we were using sine pumps and motors at first, then gear pumps and vane motors, but the same thing will apply. The motor, if rotated, would try to act as a pump.

 

No comment on the 4000 psi except it seems very high to me, even as a transient pressure. If the leaking hoses are the Ebay ones, I suspect John k is no the money.

 

 

[ditchcrawler]

I tread mine very harshly. I can easily lift the RV on my bow thruster if the engine revers are above a fast tickover . The other thing on our side is the hoses don't get waggled about like on a JCB or back of a tractor. By installing lengths of steel hose you are introducing 2 more joints/crimps that could fail. The main drive RV lifts if something jams the prop like a log of wood or a builders sack.

[john.k]

Out of the sunlight is a big factor ,then fluid heat ......all my stuff ,first the rubber develops cracks ,water rusts the steel braid ......and theres a split hose ..........very ocassionally there is a hose blown in two,nearly always from bending.............steel pipe is a much cheaper solution ,and the pipe has a lower pressure loss from internal friction,

[adrianh]

If you have peak pressures as high as that then the hoses need to be spiral reinforced, R12 or R13 grade I think - R2 are the cheaper lower pressure grade normally supplied ( will be marked along the hose )

This type have heavier crimped on end fittings that can resist pulsating/surge pressures with a hose construction that does not expand as much when under pressure.

It is much better / cheaper to use steel tubes for long runs with short hoses at each end, but the end of the tubes either need to finish with a securely mounted bulkhead fittings at the hose start point or heavy duty 2 bolt plastic pipe clamps. Also all hoses last longer if they have a slight curve and can move freely when pressurised.

Construction plant hydraulics tend to work with high pressure pumps so are a good thing to copy, they also use JIC spec hose ends as I believe this perform better

Edited May 14, 2023 by adrianh
Corrected spiral hose spec

[john.k]

Hydrostatic drive machines inevitably have formed steel tube connecting the components in the chassis .......neater ,much cheaper ,and no replacement required ............I recall one machine I used to work on that had short flexible hoses from pump to motor where the hoses had to be exactly to length or they would fail very quickly.........its all very well saying use manufacturer parts ,but that isnt done.....you get the mobile hose fixer around ,and he is usually someone who has bought a franchise ,and may have alot of mechanical experience ,or virtually none .......the franchises sell to anyone with the finance to buy ...............I used to work regularly with truck cranes that were 6000 psi ,and yes they need special hose ,but armour is only used  to stop chafing of the cover.

[Mike Adams]

Thanks for the comments. I have now looked back at the original fitting instructions from 1987 where it says ' The main feed and return hoses should be of multi wire spiral construction and capable of withstanding a burst pressure of 16000 psi or 1100 bar or solid pipework to BS3602' but it doesn't give any specification for the hose. This seems very high the ones I have ordered as replacement are working pressure of 4800 psi so maybe I need to rethink these. I haven't found out yet the relationship between working and burst pressure but I have never had any bulging hoses.

[adrianh]

It is rare for a hydraulic hose to bulge and burst ( also very dangerous as you get a fine oil jet that will go through flesh and a vapour that can ignite very easily ).

The more normal failure point is an end fitting blowing off the rubber hose. Hose that are old and have been running with excessively hot oil ( what is your oil temperature? ) which causes the rubber to age harden are a common failure point.

If you have very long hoses to your bow thruster then a double cross line pressure relief at both ends will protect the hoses better. Set these as close as possible above the system pressure.

The comment multi spiral is what I referred to in my earlier post, I have updated the details as I think R12 or 13 is this type of construction.

To check the burst pressure you need to know the hose size and the type of fittings attached.

A good supplier will do a full pressure test prior to delivery.

 

[Mike Adams]

27 minutes ago, adrianh said:

what is your oil temperature?

Very low, in fact it only gets warm to the touch after running all day. I fitted a temperature sensor with a gauge to show the oil temperature but it never gets hot enough to register on the gauge. I know the bent axis pumps/motors are very efficient and the hoses run almost the whole length of the boat so I guess most of the heat generated is dissipated. I did think about fitting another prv in between the two lines with a relief line back to the tank but I will try the replacement hoses first. I have also adjusted the rate on the engine throttle remote control lever so that it has to move further for the same acceleration of the engine so as to slow down any rapid change of direction on the single lever control.

[john.k]

Id think there was no way to get high surge pressures in a boat drive .....the other factor is engine rotating weight ...a tiny engine isnt goint to have much momentum if the hydraulics comes to dead block for some reason ......the diesel motor will just stall...................you see this effect quite commonly in excavators where the computer is kaput ......the pump runs full flow and will  stall the diesel at slightest resistance.......like track drive,or even extending a ram.

[ditchcrawler]

5 hours ago, john.k said:

Id think there was no way to get high surge pressures in a boat drive .....the other factor is engine rotating weight ...a tiny engine isnt goint to have much momentum if the hydraulics comes to dead block for some reason ......the diesel motor will just stall...................you see this effect quite commonly in excavators where the computer is kaput ......the pump runs full flow and will  stall the diesel at slightest resistance.......like track drive,or even extending a ram.

You wont stall my boat engine unless its the bow thruster  being used on tickover. I have had the prop stop dead due to logs getting caught.

 

[Tony Brooks]

6 minutes ago, ditchcrawler said:

You wont stall my boat engine unless its the bow thruster  being used on tickover. I have had the prop stop dead due to logs getting caught.

 

That is because the PRV should open, and in my view it should be set to open before the engine stalls. I bet the oil warmed up a bit though.

[ditchcrawler]

30 minutes ago, Tony Brooks said:

That is because the PRV should open, and in my view it should be set to open before the engine stalls. I bet the oil warmed up a bit though.

Not that I noticed I run via an oil cooler and of course as soon as the log jams jammed, it has happened more than once, I go into neutral and it just recirculates. I have a tank capacity of about 40lts