Sunday, January 17, 2010

Thru Hull Fitting

I decided to make each job I have to do in the engine room it's own post vs adding to the "back to work on the boat" post.

Now that I'm back working in the engine room I find myself wondering "why in the hell did I do that"? Maybe it's an older and wiser thing or maybe I just wasn't thinking right a couple of years ago, but either way I find myself having to do a bit of re-work.

My main engine is keel cooled with dry exhaust. My generator is cooled through a heat exchanger with wet exhaust. I had originally laid out the generator to be installed on the port side, but with all the weight I was putting to port, I thought it better that I move the gen-set over to starboard. Looking at the through hull fitting I had originally installed to service the gen-set ( a 1" pipe welded into the hull and threaded on its end), I began to feel this set up was totally inadequate for my future needs. Having realized just how lame my original thru hull was, the first order of business in the engine room was to remove the that 1" pipe and fabricate a more suitable through hull.

I don't want to punch a bunch of holes in my hull so I decided to fabricate a two inch sea chest that will handle my water intake needs. I want to have a fore and aft wash down set up, I might also want to have the option of raw water flushing the heads if fresh water gets scarce, I also need to think about possibly cooling my hydraulic system, and I need to be able to cool my generator.

I decided to install one 2" water intake using socket weld flanges that will lead to a proper valve, then through a sea strainer to a manifold consisting of four or five 1" valves to direct water as I need.

I bought the socket weld flanges from my local plumbing supply house and used sch. 80 pipe for the thru hull fitting. Because I want to use stainless steel for my valving and manifold, I had to electrically isolate the thru hull from the stainless. I did this with a gasket and isolating bushings for the flange. The flange on the hull side is carbon steel, while the flange on the boat side is stainless steel. In the first picture, you can see the green coating on the carbon steel flange that is welded to the mild steel sch. 80 pipe.

After welding the thru hull pipe to the flange, I gave the piece a quick sand blasting before I welded it in place.

These pictures show the various parts along with the flange welded into the hull. On the last picture you can see the remnants of red dye I used to test the welds. Air testing this piece would have been difficult and while the welds looked good I decided to dye test just in case. I'm planning on making a trip to the scrap yard later this week to see if I can find some valves and some piping. In the past I've been able to buy stainless steel ball valves at the scrap yard for $10.00, and with a little luck I'll also find some couplers and other bits I'll need.

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