hydraulic steering hose replacement

[khbritten]

I am considering a major overhaul of the SeaStar hydraulic steering on our 45' ketch. The steering is a bit spongy, and I guess this can come from a variety of sources. It has been throughly bled - no help. According to the guy at Teleflex, bad seals and valves are a leading suspect, so I plan a rebuild. But while I am at it, I am considering replacing the hoses. They are not the recommended copper tubing, but instead are heavy-gauge rubber. I have two questions to help me decide on whether to embark on this plan. First, does anyone have any experience with long-ish rubber hydraulic steering hose, or has anyone done a similar upgrade? (It's about 40' total length.) Second, in shopping around for copper tubing, I found a number of choices in PVC- or polyethylene-coated tube. This seems potentially very nice for abrasion resistance where the tube runs through the bilges and tight corners. Does anyone use this stuff on boats?

[Faster]

Soft copper tubing (comes in rolls and is easily hand formed) is available, as you say, coated with various plastics. This will protect the copper from corrosion in the marine environment and avoid the "green" appearance if any seawater contacts the tubing anywhere.

If you are planning to use tube benders to make any exit turns or tight tucks the coating can be a bit of a problem . Often the bender will tear the cover. The bender also needs to be oversized to accomodate the coating. Lubricating the area of the bend with vaseline can help the bender slide over the cover more easily.

Any required fittings involve the coating being cut away, and these areas and other tears can be taped over for protection after the fact.

Hard tubing comes in straight lengths, bends tidier and is also available coated. However getting prebent straight tubing into the tight areas involved in boats can be a real chore.

[khbritten]

Excellent, thanks. Any thoughts on what kind of plastic coating is better for the purpose? Brand recommendations? Teleflex recommends the mid-thickness L type tubing. Hard tubing isn't a good choice: there are a lot of bends, mostly wide-radius, perfect for soft tube.

[jones2r]

Rubber hose will give a spongy feel, and 40 ft. of hose is excessive. If the hydraulic pump has internal problems, it should show up as hard and unresponsive steering. Air in the system would cause sponginess. However, the presence of sponginess implies considerable hydraulic pressure. I would want to know the actual max pressure available from the steering pump, and then apply a safety factor (usually a multiple, but I do not know what is customary for this application). Soft copper tubing is usually inappropriate material for higher pressure hydraulic applications. The use of multiple lengths of rigid piping interconnected by short lengths of high-pressure rubber hose may be a safer approach, unless you know that the copper tubing's pressure spec at least doubles (triples?) the pump's capability. The use of AN fittings could help with the angles/offsets if rigid piping is required.

I would replace the hose first, and then investigate the pump, etc. Just my thoughts, which are based on knowledge of hydraulic systems and not your boat's steering system.

[cardiacpaul]

I agree with jones...

Aeroquip supplies hyd hose & ends for construction equipment in a harsher environ at much higher pressures than they hyd. system on the boat would ever see.

I'm not sure that soft copper is the answer.

[Faster]

I agree, also, that good approved hydraulic hose is probably the way to go. The question was put, however, regarding the tubing.

I don't think the pressures generated in recreational boating hydraulic steering systems is all that great. BTW - depending on wall thickness and temperatures, 1/4 inch copper can handle up to 1400 - 3600 psig, 3/8 up to 1000 - 2265 psig. I'd think that would be adequate for small boat steering systems.

But definitely, from an installation/vibration proof/maintenance point of view hose is the choice.

[jones2r]

The long run of hose is probably the cause of the sponginess. Shortening the run would be the correct answer. Otherwise, rigid piping.

Another thought has occurred to me. If there is point in the the hose that is higher than the ends, it will be nearly impossible to bleed the air out. Might be the first thing to check.

Further thoughts: The soft tubing will be trying to straighten itself whenever pressure is applied, causing work hardening. Then it cracks or splits. Just a minor inconvenience. A little bit of cleanup. Then a couple of compression unions and a short piece of tubing to patch should hold it until it breaks again. OOPS! Compression fittings are a no-no in pressure systems. Double-flare and threaded unions; just a little extra inconvenience, until it breaks again.

Why is there such a long run from the pump to the steering? The boat's only 45 ft.

BTW, the designation AN means Army/Navy. Aeroquip-type materials are for aircraft and marine applications.

[sailaway21]

I too am not sure about the 45' run. If I had a long straight run I would use steel pipe. There will be no corrosion on the inside and you can paint it on the outside. Advantage being that tou can thread it and connect hoses to it using Iron pipe thread fittings. Stronger and no leaks. The rigid pipe will remove most flex in system. New high pressure hose will probably solve the sponginess as it is probably due to internal hose deteriation also. Long runs of hose must be properly secured as they will flex laterally under load and this can lead to abrasion in unforeseen and unseeable locations. Aeroquip is the leading supplier of ss braid sheathed hose for the auto racing market and they have a product to meet every pocketbook. (by that, I mean that once you get off the floor from hearing how expensive their cheap stuff is they'll be happy to tell you how much the good stuff costs) Given the nature of small boats I expect you are going to have to use a sizable measure of flexible hose. Other than ss I'm not aware of any coating that is going to help you with abrasion resistence. I would emphasis that just because the hose is flexible and lays nicely, you must still secure it properly or you will get abrasion from hose flexing under load.
One item to consider in the degrading of your system is water. Water, via condensation or any other source, is death on hydraulic fluid as well as on hoses and pumps. If substantial amounts of hose are to be run it may be worth investigating a silicone based hydraulic fluid. Obviously, pump compatibility would have to be ascertained first. Silicone is non-hygroscopic (back to water again!) and so condensation will not be picked up in your reservour and the rubber hoses will last indefinitely.
I do not see any advantage to copper lines of any sort and numerous disadvantages as noted by jones.

[pigslo]

What is the original spec on the hoses and how long did the current ones last?