Fitting an auto pilot pump - cutting the hydraulic lines??

dalex

dalex

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Hi folks,
I am introducing a pump into a 2 line dual station hydraulic steering system, which uses 3/8" nylon tubing.
Q1 is this tubing substantial enough to take the pressure from a typical auto pilot pump - in this case, a Navico? Current helm pumps are teleflex seastars.
Q2 How would you go about getting a really good square cut on this type of tubing, bearing in mind I am probably going to have to cut all 3 lines in a difficult-to-reach area of the boat?
Q3 As the 3 lines will all have fluid in them, I thought I'd temporarily bung up the end with a lump of blu-tac - bad idea? Any other suggestions bearing in mind its only going to be for 10 minutes or so...
Many thanks
 
go to your nearest hydraulic hose company and get some new hose made up to the correct length. avoids getting bits of plastic into the hydraulic liguid, which is not recommended.
 
I fitted a system a couple of years ago using seastar helm pumps & Raymarine autopilot pump.

First of all, the nylon tube is well up to the job.

Regarding cutting the tube, I used a pair of the cutters that plumbers use to cut plastic water pipe but a sharp stanley knife will do the job (do not use a hacksaw as the bits will cause many problems)

Fluid loss, If you prepare the pipes frm the pump with the 'T' peice ready, then it is just a case of cut and push both ends in to the 'T' piece and tighten (I assume you are using compression fittings)
Block the breather/filler on the upper helm to reduce fluid loss and do not turn the helms whilst pipe is cut.
Blue tack is a no no as it may block the valves in the pumps.

PM me if you need any further info.

Hope this helps
 
Thanks for the warning on the blu-tac - I was a bit wary about it blocking the check valves in any of the pumps, and thinking about it, cutting the pipe followed by stuffing the ends into the tee fittings will be mere seconds, so no need for blocking the pipes if I'm quick.
I never thought to use one of those plumbers cutters - great tip thanks! I had a practice run cutting the tube with a new stanley blade on a spare bit of old pipe, and wasn't impressed with the lack of square on the end. Yes I am using compression fittings. My ferrules fit both the inside and the outside of the 10mm tube, so square is very important to get most joint strength.

How do I block the breather on the upper helm? Both my helms seem to have filler plugs. I can't see a breather as a separate device up there. Does the filer plug double up as a breather? If so, leaving it closed should reduce any syphoning do you think?
Thanks.
 
I used nylon pipe to fit the auto pilot pump on the hydraulic steering of my previous yacht. The first time I put it onto full hard over the pipe burst. IMHO do not use nylon pipe use high pressure hydraulic hose with proper steel fittings of at least 1000 psi rating

The various hydraulic steering pumps have looked at have their pressure relief valve set at 1000 psi which is higher than the burst pressure of the average nylon pipe.

Have a look here under tubing, hoses & fittings
 
The filler plug on the upper helm will have a small hole in it to act as a breather, just place some tape over the hole to block.

I tried the garden secateurs and whilst they gave a clean cut it was difficult to leave the end square.

It's a fair point about the PSI rating of nylon tube. I suppose there are different grades. I got mine from a supplier of hydraulic and air systems and have had no problems or leaks in 2 years of use.

Another tip - when fitting the pipes to the pump, do not use the PTFE tape as any stray bits may block the valves. Use the liquid version (as recommended by Seastar)

I have the fitting/instuction manuals for the Seastar pumps,
if you need one, let me know and I will copy & post to you or you can find them on the internet.

Regards
 
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