hydraulic steering

Unless it is a power steering system, most manufacturers spec a SAE-100R1hydraulic hose. Hynautic systems usually use a 950psi relief valve so you need a working pressure at least above that. I have seen a lot of installations with Parflex MSH5 or MSH6 hose (wp 1000 psi).

Hi,

How are you comparing 15 to 20 Bar of Air with the normal working pressure of the Hydraulic System?

Hi,

You have me more confused than ever with that statement.

You have a Hydraulic Steering System, you want to replace the hoses on it. That much I understand from your first post.

You do not have any information on the system such as manufacturer or model,Ram or existing hoses.

You say you pump it up with air to 15 to 20 Bar.

Why did you decide this was the right working pressure or couldn't you pump it up any higher than that?

Hi,

Glad you got it sorted out.

You might well find that the system pressure is considerably higher when you are underway and there is a load on the rudders than what you saw when trying to see what pressure it worked at while sitting still.

The system will work fine when the boat is alongside and there is no load on the rudder.

When you are underway and have water pressure acting against the rudder is when the pressure will increase, or heaven forbid, the rudder hits a submerged object. This pressure will be related to the speed you are doing, the angle of turn you have wound on and the sea state; this would be very difficult to guess.

I would go with the higher rated hose personally unless you have tried the lesser underway. If a steering hose blows underway at speed, you may be in more trouble than just a hydraulic leak.

The preloaded pressure in the system is there to force fliud into the "feed" port on the helm(s) and keep air from being fed into either port or starboard ram lines, and is not actually present in the lines at the ram. The system will in fact work with no pressure present but you run the risk of sucking in air through whatever leak allowed the pressure to bleed down in the first place.

Running lower pressure rated hoses may allow the system to work at the dock or under light steering loads at slow speeds but when you need it most, for high speed emergency avoidance turns, it will be sluggish and spongy feeling. The lower pressure hoses will swell like baloons absorbing the fluid pressure rather than pushing the ram cylinder over to turn the rudder(s).

You want to make sure you don't skimp on the hoses. They should have both adequate diameter and working pressure or your steering will be slow and soft. Refrigerant grade copper tubing, Kevlar-reinforced Parflex tubing, or Aeroquip type hose is all I'd consider for steering lines, paying particular attention to the fittings if using the latter.

Bill

I would replace with same pressure rated hoses, as im sure that was the orginal design parameters of the system, maybe just use higher quality hoses like the other guys mentioned below. Aeroquip comes to mind

What gauge reads 15-20 bar? The part of the system you "pump up" is the low pressure side which feeds the pump- then it kicks out pressurized fluid that moves to the ram which directs it and thus moves the rudder. I have not seen a system where you can "pump up" the high pressure side of the system- but the low pressure sides typical pressure is 15-20 psi . If yours is anything like most other 48 foot sportfish then you need the Parflex 1000psi working hose. Get the reusable end fittings and don't kink the hose anywhere at anytime. Don't go with a lower rated hose. I could be wrong, but with the info you gave this is MHO.