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Hydraulic steering questions

Discussion in 'Technical Discussion' started by lucseawalker, Jan 21, 2017.

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  1. lucseawalker

    lucseawalker New Member

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    We have a old Vetus steering system and we have the following problem: when the rudder is hard over (HO) we can still force the helm to keep turning. Friends tell us that it should not be so! The helm should not be able to turn anymore, period. When we get HO, we feel a resistance but it is not that difficult to continue turning the wheel.
    We thus worry than in heavy seas conditions, if the pressure on the rudder get greater, we would be able to keep turning the helm, with no effect on the rudder! No good! So we would like to solve that problem.

    Here is what we did so far:
    First of all, we bypassed the non-return valve box and there was no improvement [​IMG] We believe that the only reason of that part is to protect the pump from rudder backlash in heavy seas. Being on a mooring in protected water, we believe that part is not critical to our testing so we kept is out of the loop. Are we wrong???

    We then did take the cylinder apart and replaced the internal seals that move oil one way or the other in/out of cylinder and there is no improvement [​IMG]

    We figured that the problem then has to be the pump at the helm. First of all, we disconnected one of the 2 hoses going to the cylinder and turned the helm one way > it kept turning even as the rudder was HO. That should not happen since the hose was plugged, correct??

    We then took the helm pump apart and everything looked in perfect condition (pump from 2005) .. except for a little muddy grid solidly stuck to the bottom of the reservoir housing.... I wiped it out with a rag. The pistons are shinny and move freely up and down on their springs ... the 2 small set screws on the bottom contains each a small SS ball that freely moves up or down. We are at a loss as to what other testing we can do now...

    My friend thinks the oil is more viscous that it should. Vetus recommends using 22 hydraulic oil ... could the problem of the helm continuing to turn be related if the oil was thicker?? Anyone has any idea? I will go tomorrow in the small town 1 hour away but I really doubt I will find any 22 hydraulic oil ... could I use any substitute oil? compressor oil? 68 hydraulic? ... brake fluid? I will also buy some 4ft of 50bar hydraulic hose with hose clamps to try to use my pump on my frien's cylinder and then my cylinder on his pump to see if we can narrow down where the problem is ... before buying either a new pump or a new cylinder, I should know where my problem lies.

    BTW Vetus Holland has not replied to my email and I read on forums that they are not interested at all to help fixing old system ... I will still try to call them this week and other specialists .. wish me luck and please share any insight if you have. Tnx

    Luc

    PS: we have a Vetus MTP53 pump (53cc) and a Vetus cylinder that is about 200cc volume
    Last edited by a moderator: Jan 24, 2017
  2. Bamboo

    Bamboo Senior Member

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    Does the steering work fine in other respects? ... I mean when it's not hard over?
  3. lucseawalker

    lucseawalker New Member

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    Yes, it does.
  4. Capt J

    Capt J Senior Member

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    There is a check valve that is bad. I am not infinitely familiar with your system. On most Seastar systems the check valve is a disc in the steering ram and that goes bad and causes the situation you describe and sometimes also allows the propwash to slowly move the rudder and you have to counter steer. The check valve could also be in the helm unit as well. If you have two steering stations see if the other one exhibits the same.

    Chances are you won't find fluid that light. But AW 32 would be the closest or automotive power steering fluid. Having heavier fluid in your system will not cause the issue you are describing. It's a bad check valve.
  5. lucseawalker

    lucseawalker New Member

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    Thanks for your your input. We did not see any check valves in the steering cylinder but I think there are 2 small SS balls in the bottom part of the pump at the helm, that can block or not 3 small holes in the area they are set. Not sure how to find out if the problem is there or not but what you say seems to indicate that the problem is with the pump ...
    Good to know that I could eventually get by AW32 oil. I do have some syntetic compressor oil ... looks thin .. wonder if that would be suitable?
  6. Capt J

    Capt J Senior Member

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    It sounds like the balls are acting as check valves. Usually they'll have a spring holding them in with tension, until the steering input overcomes the tension of the spring.

    On the seastar rams it's a ceramic disc inside the ram that acts as the check valve, eventually the disc cracks and breaks into pieces...... Try to find schematics of your system online. BUT, you may really want to just replace the system with a new one. Sometimes when you fix worn out stuff, you still have temporarily working worn out stuff.
  7. K1W1

    K1W1 Senior Member

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    Do you know what the system pressure is when the wheel continues to turn? Hydraulic Systems need relief Valves , maybe you have reached the limit in yours.
  8. lucseawalker

    lucseawalker New Member

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    Thanks for that. I just looked again on the schematics of both cylinder and pump and nowhere do they show springs (other that each spring under the small cylinders ) or ceramics .. i am puzzled
  9. lucseawalker

    lucseawalker New Member

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    No, I have no pressure gauge on the system and I am not sure where any opressure valves would be located, at the pump or in the cylinder??
  10. K1W1

    K1W1 Senior Member

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    In the pump so the HP can be released back into the inlet side or tank if the tank is integral with the pump.
  11. lucseawalker

    lucseawalker New Member

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    Ok, the pump looks more and more like the issue ... I wonder if they built it that way as we were able to force the helm over, past the HO point, even when the pump was brand new in 2005. Perhaps if you apply enough pressure at the helm it is supposed to protect the system from increasing the pressure too much??? But now, with the pump older and perhaps missing springs it does it too soon ???
  12. Capt J

    Capt J Senior Member

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    I don't know. If it did it since new, then it's quite possible the helm is just bleeding it out of the overpressure valve and not an issue at all.
  13. K1W1

    K1W1 Senior Member

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    Test the pressure or you will be asking questions forever without knowing one system fact
  14. lucseawalker

    lucseawalker New Member

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    I just called Vetus in Holland and spoke with a technician who indicated that when the helm is HO .. if more than 60 Bar of force is applied, then the relief valves in the pump will protect the system by circulating the oil inside the pump. That is a crucial info to know :) I will now test pump and cylinder individually, then put everything back on our boat with brand new AW 32 hydraulic oil I was very lucky to find in the small town today and then see how it all goes ... Will the helm offer enough resistance when turned HO or will it continue to turn too easily. If the latter was the case, apparently there is not much to be able to do to repair the pump ... so I will have to replace the pump then ... I will keep you posted ...
  15. Bamboo

    Bamboo Senior Member

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    If the system works as designed except when you attempt to turn the wheel when the rudder is already hard over I'd suggest you do nothing other than stop turning the wheel when the rudder is already hard over.
  16. lucseawalker

    lucseawalker New Member

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    I was thinking exactly the same thing myself a few days ago ... I guess I wanted to be sure that the system will work in heavy wx and not have the pump bypasssing itself when there is a little more resistance on the rudder ... indeed, if I could connect a pressure gauge to the system, then I would know if it bypasses only when the 50 Bar designed pressure is reach or not!
    But, I am not sure how I could do that right now, so I probably will do as you suggest and not worry about it ...

    Part of my saga here is that I have a second issue: the autopilot I have now requires 3 turns HO to HO and our actual system has 5 thus rendering the task impossible to the autopilot. I have 3 choices and I can choose the best one ONLY after I determined the problem #1 that is the turning of the wheel past the stop.

    To fix the autopilot issue, I can either replace the pump OR the cylinder in order to reduce the numer of turns, OR I could install a hydraulic pump on the autopilot and get rid of the helm wheel connection OR I could get a different autopilot altogether, one that accommodates wheels that turn 5x

    After the testing today, I should be able to determine the best way to solve now the autopilot issue ....
  17. K1W1

    K1W1 Senior Member

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    Given the little bit of info I would say your auto pilot is mis matched to your steering gear.
  18. lucseawalker

    lucseawalker New Member

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    We finished testing pump and cylinder today with another pump & cylinder on a friend's boat and we discovered that my cylinder (1980!) is doing very well but my problem is the pump. The relief valve must open at very low pressure.
    So I will buy another pump, a bigger one that will give me less than 3 turns HO to HO so my autopilot will be happy with it and both my problems will be solved. I just dread the fitting of the new pump (from a different manufacturer since Vetus has no pumps big enough anyway) as far as connections and housing size ...
    Thanks everyone for your ideas ... I will return in a few weeks after I get the pump shipped to me here in the Pghilippines and have finished installing it ... hopefully with a very good ending!
  19. Capt Fred

    Capt Fred Senior Member

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    Have you assured yourself that the wheel is positively driving the pump shaft. In other words could the wheel be slipping on the pump shaft?
  20. Bamboo

    Bamboo Senior Member

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    3 turns lock to lock is a bit less than the norm of 3.5-4.0 5 is a bit high. Sounds like you need to adjust the autopilot settings- not purchase a new pump and install it. It's hard to believe that a autopilot cannot be set up/ adjusted to accommodate 5 turns lock to lock.