Digger hydraulic quick hitch

Hesston4860s · Apr 24, 2020

essexpete said:
I am not familiar with hydraulic hitches but I thought they unlatched by by hydraulic power and locked by a sprung loaded action?

Generally they open and close hydraulically, some have springs to keep them closed some don’t (mine doesn’t). Generally the non sprung type have a very minimal flow to the extent side of the hitch ram to keep it closed, mine however has full system pressure keeping it closed. Since the ram is at full stroke (hitch closed) the pipe is dead heading and eventually just fails.

Lincs Lass · Apr 24, 2020

Hesston4860s said:
Generally they open and close hydraulically, some have springs to keep them closed some don’t (mine doesn’t). Generally the non sprung type have a very minimal flow to the extent side of the hitch ram to keep it closed, mine however has full system pressure keeping it closed. Since the ram is at full stroke (hitch closed) the pipe is dead heading and eventually just fails.

Has it got a switch in cab to isolate the flow to the hitch ,once its locked it should stay pressurized without continuous pressure pushing at it

essexpete · Apr 24, 2020

Hesston4860s said:
Generally they open and close hydraulically, some have springs to keep them closed some don’t (mine doesn’t). Generally the non sprung type have a very minimal flow to the extent side of the hitch ram to keep it closed, mine however has full system pressure keeping it closed. Since the ram is at full stroke (hitch closed) the pipe is dead heading and eventually just fails.

That just does make sense unless it gains pressure like the JCB hydraclamps or the old powerslide clamp on the old 360s?

Hesston4860s · Apr 24, 2020

Lincs Lass said:
Has it got a switch in cab to isolate the flow to the hitch ,once its locked it should stay pressurized without continuous pressure pushing at it

Yes there’s a switch, press the green 1 and it intermittent buzzes then press the red 1 constant buzzing and the hitch will then un lock. Swap ya buckets press the green button again now no buzzing and it will lock and remain will full system press to keep it locked !.

it doesn’t isolate the flow tho it just crosses the ports on the hitch valve Between lock and unlock.

Lincs Lass · Apr 24, 2020

Hesston4860s said:
Yes there’s a switch, press the green 1 and it intermittent buzzes then press the red 1 constant buzzing and the hitch will then un lock. Swap ya buckets press the green button again now no buzzing and it will lock and remain will full system press to keep it locked !.

it doesn’t isolate the flow tho it just crosses the ports on the hitch valve Between lock and unlock.

Could be that where the problem lies ,high pressure is getting past the cross over ,,they are supposed to have a trickle feed to keep the lock engaged but it sounds more like too much

Hesston4860s · Apr 24, 2020

Lincs Lass said:
Could be that where the problem lies ,high pressure is getting past the cross over ,,they are supposed to have a trickle feed to keep the lock engaged but it sounds more like too much

yes I think it is where the problem is somewhere, but is it the valve that is faulty or is the fact all other hitch systems I’m coming across have a check valve and a restrictor in the pressure line from the pump to the valve where mine hasn’t !.
i don’t really just wanna stick a new valve on it as they aren’t cheap and it still be the same.

Lincs Lass · Apr 24, 2020

Hesston4860s said:
yes I think it is where the problem is somewhere, but is it the valve that is faulty or is the fact all other hitch systems I’m coming across have a check valve and a restrictor in the pressure line from the pump to the valve where mine hasn’t !.
i don’t really just wanna stick a new valve on it as they aren’t cheap and it still be the same.

How long have you had the digger ,from new or second hand,,has this problem of pipes failing only just started or done it in the past before it started to be a regular occurance.

Hesston4860s · Apr 24, 2020

Lincs Lass said:
How long have you had the digger ,from new or second hand,,has this problem of pipes failing only just started or done it in the past before it started to be a regular occurance.

I’ve had it since 2013 it was second hand but from an owner driver, it was ok when I first got it. Then it’s done this on and off from about 2015, it’s been really bad this last couple of weeks. Probably had 25-30 pipes on the hitch since I’ve had it did 5 in 4 days once !, everyone I’ve ever asked says it’s working properly.

Lincs Lass · Apr 24, 2020

Hesston4860s said:
I’ve had it since 2013 it was second hand but from an owner driver, it was ok when I first got it. Then it’s done this on and off from about 2015, it’s been really bad this last couple of weeks. Probably had 25-30 pipes on the hitch since I’ve had it did 5 in 4 days once !, everyone I’ve ever asked says it’s working properly.

Two a year is bad luck ,,5 in 4 days is not working properly ,,what you have spent in lost time and new pipes would have cured to fault a long time ago

essexpete · Apr 24, 2020

So what is the fail safe if the pipe blows? What is to stop the hitch unlocking?

Lincs Lass · Apr 24, 2020

essexpete said:
So what is the fail safe if the pipe blows? What is to stop the hitch unlocking?

By rights,a big safety pin about 25mm thick right through the hitch but that's only used on site work for safety, on your own and nobody around it's not really needed but it should be

Hesston4860s · Jun 2, 2020

Mr Happy said:
The lack of a pressure relief valve will be the cause of your hoses blowing there ends off. Surely there shouldn't be constant pressure to the hitch ram. Post some pictures of the hitch valve so we can advise on a suitable relief valve.

Finally got round to getting a picture

The close port has a 0.9 mm restrictor fitting in it now, but it’s hardly made any difference.

Bloders · Jun 2, 2020

Lincs Lass said:
By rights,a big safety pin about 25mm thick right through the hitch but that's only used on site work for safety, on your own and nobody around it's not really needed but it should be

The way i understand it;
On a fully automatic hitch there is no "safety pin" they work as above where there is a constant bleed a bit like the hydraclamps to keep the hitch locked.
Alternative is a manual hitch with a spring and a locking pin.
I believe a semi automatic, which uses a locking pin and hydraulic release are not allowed to be sold new now - they are certainly outlawed on the railway. People would not bother with the locking pin and attachments would become detached and hurt people/things

Zetor · Jun 2, 2020

Almost all hydraulic hitches have a constant feed to keep them closed, in case of a bust pipe some have a safety pin, some have a mechanical linkage that is sensitive to hitch position and some have an spring Inside the ram to keep them closed.
The qh takes Its feed from a test port on the main pump, pumps are usually load sensing hence you have to crowd the bucket in To wake the pump up to get the hitch to move.
As far as I’m aware The qh runs at the same pressure as the pump so my suspicions will be the pipes not crimped well enough.

Lincs Lass · Jun 2, 2020

Bloders said:
The way i understand it;
On a fully automatic hitch there is no "safety pin" they work as above where there is a constant bleed a bit like the hydraclamps to keep the hitch locked.
Alternative is a manual hitch with a spring and a locking pin.
I believe a semi automatic, which uses a locking pin and hydraulic release are not allowed to be sold new now - they are certainly outlawed on the railway. People would not bother with the locking pin and attachments would become detached and hurt people/things

when I was on plant job ,,we had two 13 tn 360,s ,both had dramone hydraulic hitches ,even when the hitch locked in it was advised to slide the safety pin through ,,I had 6 months on a gas terminal site and if you were found not using the pin ,you were of site goodbye

Bloders · Jun 2, 2020

Lincs Lass said:
when I was on plant job ,,we had two 13 tn 360,s ,both had dramone hydraulic hitches ,even when the hitch locked in it was advised to slide the safety pin through ,,I had 6 months on a gas terminal site and if you were found not using the pin ,you were of site goodbye

How long ago was that?

Lincs Lass · Jun 2, 2020

Bloders said:
How long ago was that?

2008

tinman · Jun 2, 2020

The hydraulic pressure of your digger should be somewhere round the 3,000 psi mark, a 1/4" 2 wire hose's working pressure would normally be round the 6,000 psi range and that's working pressure, burst pressure would far exceed that.
yes the hitch gets full pressure when the bucket is on but it should be nowhere near the max working pressure never mind the burst pressure.
your valve is not unlike any other valve thats fitted to your style of hitch so in fairness the folk who are saying everything is right, they would be correct.

out of interest, are all the hoses your getting made from the same supplier?, are they using gates hose and gates fittings?.
if so and they are blowing off id be trying someone else to make my hose's.

i have a 13T one here with a hitch on it and the 1/4" hoses to the hitch are just the average 2 piece fittings, ive never had one burst or blow off from pressure alone.

it might not be available to you altho their not too dear but id be putting a test point on the hose that's bursting as Mr happy said and leave a test gauge connected to it in the cab where i could keep an eye on it to see what pressure its going to but tbh i don't think your hose supplier is crimping your hoses right.

https://www.ebay.co.uk/itm/Hydrauli...557441?hash=item594bd85281:g:2UoAAOxy3NBSeLfo

Hesston4860s · Jun 3, 2020

tinman said:
The hydraulic pressure of your digger should be somewhere round the 3,000 psi mark, a 1/4" 2 wire hose's working pressure would normally be round the 6,000 psi range and that's working pressure, burst pressure would far exceed that.
yes the hitch gets full pressure when the bucket is on but it should be nowhere near the max working pressure never mind the burst pressure.
your valve is not unlike any other valve thats fitted to your style of hitch so in fairness the folk who are saying everything is right, they would be correct.

out of interest, are all the hoses your getting made from the same supplier?, are they using gates hose and gates fittings?.
if so and they are blowing off id be trying someone else to make my hose's.

i have a 13T one here with a hitch on it and the 1/4" hoses to the hitch are just the average 2 piece fittings, ive never had one burst or blow off from pressure alone.

it might not be available to you altho their not too dear but id be putting a test point on the hose that's bursting as Mr happy said and leave a test gauge connected to it in the cab where i could keep an eye on it to see what pressure its going to but tbh i don't think your hose supplier is crimping your hoses right.

https://www.ebay.co.uk/itm/Hydrauli...557441?hash=item594bd85281:g:2UoAAOxy3NBSeLfo

I've had hoses on it from 3 different places one of which was gates pipe with gates fittings and they all do the same, I’ve had gauges on it before but I can’t remember exactly what the pressures where now as it’s awhile ago.
I’m pretty confident it’s not right as after you activate/deactivate it, it shouldnt open/close on it’s own which it does. It should only operate when you move the bucket circuit !.
none of the other machines I’ve driven over the years send full system pressure to the hitch to keep it closed, yes they send some oil but all there valves have a pressure relief valve in the Hitch close side of the valve.
I was on a 22 ton CAT only a couple of weeks ago and it was painfully slow closing the hitch due to the minimal flow aloud by the valve.

I'm that fed up with it I’m thinking of striping the hitch off it and selling the digger.

Bloders · Jun 3, 2020

Lincs Lass said:
2008

I was wrong. I thought they had been prohibited, though in truth, its a voluntary ceasation to supply.
Either way, since October 2008, you cant buy a new semi auto QH

Semi-automatic quick hitches - Construction health & safety

www.hse.gov.uk

Digger hydraulic quick hitch

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