Hydraulic pump locks up

[blackdogsailing]

I have an old model navtec hydraulic pump which works the kicker and backstay. It works fine for about 10 or so pumps then suddenly locks up solid. I have bled both rams and the fluid level is fine. Any ideas about curing the problem ? Accessing the pump and valves requires major dismantling of cabin furniture so if there is something I can do without resorting to that it would really help !

Chris

 

[Bilgediver]

I have an old model navtec hydraulic pump which works the kicker and backstay. It works fine for about 10 or so pumps then suddenly locks up solid. I have bled both rams and the fluid level is fine. Any ideas about curing the problem ? Accessing the pump and valves requires major dismantling of cabin furniture so if there is something I can do without resorting to that it would really help !

Chris

Do the cylinders move at all during these 10 pumps?

 

[blackdogsailing]

Do the cylinders move at all during these 10 pumps?

Yes, no problem.

 

[Bilgediver]

Yes, no problem.

If you stop pumping before lock up can you then retract the cylinders normally??

How are you bleeding the rams after lock up? Does the pump come free at this time?????

 

[blackdogsailing]

If you stop pumping before lock up can you then retract the cylinders normally??

How are you bleeding the rams after lock up? Does the pump come free at this time?????

Yes, if I stop pumping before lock up, I can release the pressure normally. they then work normally again before locking up.
bleeding the rams by just loosening the pipe connectors at the ram and letting fluid come out (no sign of air at all).

Chris

 

[Bilgediver]

Yes, if I stop pumping before lock up, I can release the pressure normally. they then work normally again before locking up.
bleeding the rams by just loosening the pipe connectors at the ram and letting fluid come out (no sign of air at all).

Chris

Previously when the cylinders had fully operated and you kept pumping could you keep pumping but it just got harder???

Does your system normally stop operating at a preset pressure or do you stop pumping when the tension gauge gives a certain reading?

 

[blackdogsailing]

Previously when the cylinders had fully operated and you kept pumping could you keep pumping but it just got harder???

Does your system normally stop operating at a preset pressure or do you stop pumping when the tension gauge gives a certain reading?

Yes, it just got progressively harder. No preset pressure and gauges are u/s. We just pumped until we had the desired tension !!

Chris

 

[yoda]

I have an old model navtec hydraulic pump which works the kicker and backstay. It works fine for about 10 or so pumps then suddenly locks up solid. I have bled both rams and the fluid level is fine. Any ideas about curing the problem ? Accessing the pump and valves requires major dismantling of cabin furniture so if there is something I can do without resorting to that it would really help !

Chris

I would expect the system to have return lines and a reservoir. If the fluid is unable to go back to the pump or resevoir then the system will lock up. Check no valves have become accidentally closed in the system.

Yoda

 

[penfold]

If it's a two speed pump with a high volume/low pressure stage and a low volume/high pressure stage, if the changover valves are malfunctioning it could cause these symptoms. Does the lock up coincide with tension coming on the rams?

 

[rogerthebodger]

" hydraulic pump which works the kicker and backstay "

Are the kicker and the backstay 2 separate cylinders with a single pump. If so there must be a change over valve somewhere and this could be faulty.

Is there a hydraulic circuit somewhere so we can see how it's setup

 

[Bilgediver]

" hydraulic pump which works the kicker and backstay "

Are the kicker and the backstay 2 separate cylinders with a single pump. If so there must be a change over valve somewhere and this could be faulty.

Is there a hydraulic circuit somewhere so we can see how it's setup

Maybe the OP can confiirm if he has something like the one in the link below Roger.... I expect there are folk racing in the UK who have similar.

I was beginning to think a control valve or relief valve issue.


http://www.navtec.net/\assets\img\dataset\manual-system-50l.pdf

 

[rogerthebodger]

If it is a multi function system it could be a faulty selector valve of the knob is not turned until you feel the knob click as described on page 3 of the doc in your link.

 

[blackdogsailing]

" hydraulic pump which works the kicker and backstay "

Are the kicker and the backstay 2 separate cylinders with a single pump. If so there must be a change over valve somewhere and this could be faulty.

Is there a hydraulic circuit somewhere so we can see how it's setup

Yes, 2 separate cylinders, each with their own changeover valve. (pump, hold and release). No schematics anywhere I'm afraid. System has a reservoir then a line to the pump. Pump then feeds the changeover valves which then feed the rams. There is also a return to the reservoir. If the changeover valve is faulty surely it would not work at all ?
Chris

 

[blackdogsailing]

Maybe the OP can confiirm if he has something like the one in the link below Roger.... I expect there are folk racing in the UK who have similar.

I was beginning to think a control valve or relief valve issue.


]

Mine is an earlier model than that. Have seen it on a couple of old swans in The Solent. There are 3 individual changeover valves. (One isn;t being used) and the pump is to the left of them.

 

[Steersman]

Could it be that the piston rod has bent?

 

[blackdogsailing]

Could it be that the piston rod has bent?

Not with the symptoms occurring on both rams. I am going to have to take the pump out and service it I think. Problem is, the riggers won't touch it as they don't know how it comes apart either !!

 

[Steersman]

I'm sure it's fixable. Sometimes these things just need a bit of TLC. Take something apart, put it back together and it works again. Don't know why, but there it is. Also, I guess you plan to replace the seals, that may just solve it too.

Good Luck.

 

[penfold]

Hand-op hydraulic pumps are not complicated, the biggest challenge will be dismantling it as the plugs and fasteners will probably either be glued in with loctite or corroded in. Document the process with video or lots of pictures and make notes as you go, particularly noting the number of turns removing plugs holding relief valve springs, as this will preserve preset pressures.

It may be worth taking the unit to whatever local hydraulic service agents you have near you; they may not be familiar with your pump, but they will have serviced similar equipment, understand how to dismantle it and probably have seals in stock.