A new hotwell for Rainbow

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barts
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A new hotwell for Rainbow

Post by barts » Thu Nov 30, 2017 8:23 pm

During this summer's steaming in our newly acquired Rainbow (26' ex-Navy double ender), I decided we needed to add a float valve to her hotwell. Although a nice big boiler means that the water level moves slowly, I find fiddling w/ the pump bypass valve annoying. When I removed the hotwell at the end of our trip, I discovered that the drain was a piece of 1/2" pipe clumsily welded into a stainless hotwell, and that it was leaking around a large rusted area. I'd also seen salt spray drifting towards the hotwell in some wind and wave conditions, which is definitely less that optimal.

Rainbow's hotwell is approximately 7.5" square, and 24" deep - tricky for a float. In addition, there's not a lot of room to fit a more traditionally shaped hotwell w/o impinging on passenger space.

I removed the rusted steel pipe and cleaned up the rusted area, inside and out. I tried putting in a bulkhead fitting, but the wall of the hotwell was too damaged in that area for a proper seal. I tried first ox-acetylene welding the area w/ stainless rod, which didn't work well, and then brazing it a new piece, but ran into an interesting problem - the bronze caused stress cracking to appear in the stainless steel, and thus leaks. Since I don't have TIG gear, I was somewhat annoyed.... A visit to a local scrapyard turned up a slightly larger stainless tank of very similar construction - perhaps some sort of standard commercial tank, and for the princely sum of $13 I took home a new hotwell.

I installed a float valve with the long arm (12" or so) pointing straight down, added a stationary guide and connected a 6" ball float via a piece of heavy ball chain to the end of the arm, matching the recommended dimensions from the valve manufacturer. The ball chain wraps 90 degrees around the guide, and lets the float move up and down while still giving adequate leverage w/ the 12" long arm. I added a proper drain bulkhead fitting in the bottom, bolted on some angle w/ sealing washers to help retain the tank on the bottom, and made a lid from 1/8" polycarbonate. I also added a simple bulkhead fitting for the condensate to drain back into the hotwell.

I tested the hotwell w/ a hose - works like a charm. I'll install it when I'm next up in the San Juan Islands. Here are some pictures; note the shock cord securing the lid.
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Re: A new hotwell for Rainbow

Post by cyberbadger » Fri Dec 01, 2017 12:55 am

The new hotwell looks great!
barts wrote: I'd also seen salt spray drifting towards the hotwell in some wind and wave conditions, which is definitely less that optimal.
So does this imply it had a vacuum? Confused.

How do you go about choosing valves and fittings for a hotwell? Does it have to be steamrated or near the MAWP? This is partially a general question, if you are running condensing or have more complex setups how does one decide what is sufficient/appropriate for certain areas. For example, sometimes the water rating WOG(Water/Oil/Gas) is a much higher pressure, but if it's in an used area that isn't expected to see steam just hot water - does it need to be steam rated?

-CB
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Re: A new hotwell for Rainbow

Post by barts » Fri Dec 01, 2017 1:09 am

cyberbadger wrote:The new hotwell looks great!
barts wrote: I'd also seen salt spray drifting towards the hotwell in some wind and wave conditions, which is definitely less that optimal.
So does this imply it had a vacuum? Confused.
How do you go about choosing valves and fittings for a hotwell? Does it have to be steamrated or near the MAWP? This is partially a general question, if you are running condensing or have more complex setups how does one decide what is sufficient/appropriate for certain areas. For example, sometimes the water rating WOG(Water/Oil/Gas) is a much higher pressure, but if it's in an used area that isn't expected to see steam just hot water - does it need to be steam rated?

-CB
When Rainbow is taking waves on the front starboard quarter and the wind is from the same direction, the resulting spray tends to come over the gunwale. This can end up in the hotwell, as that is on the same side of the boat.

The hotwell is at atmospheric pressure, and there's supposed to be liquid inside. Temps are usually about 70 or 80 F; I'm working on getting those
up to 120 or so. Steam rated valves are not needed; anything that can handle domestic hot water will work just fine. Note that the float valve does see basically boiler pressure (since the feed pump will reach that and a bit more to get water into the boiler), so make sure the valve+float+level are rated for that. Watt makes a nice heavy duty float valve.

- Bart
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Re: A new hotwell for Rainbow

Post by cyberbadger » Fri Dec 01, 2017 1:20 am

barts wrote:When Rainbow is taking waves on the front starboard quarter and the wind is from the same direction, the resulting spray tends to come over the gunwale. This can end up in the hotwell, as that is on the same side of the boat.
I don't know why I don't think of it when you clearly wrote "salt spray" - but even though I have petrol motored/kayaked a around the Juneau area I don't always remember that salt water imposes more challenges to a steamer. I didn't think of wave contaminating your feed water sources....

Eventually I intend to visit my cousin near Shelter Island with a steamer I make or purchase. So I should pay attention to how it's done.

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Re: A new hotwell for Rainbow

Post by malcolmd » Sat Dec 02, 2017 6:16 pm

What a neat solution. ...I think this might well find its way into Befur :-)

BTW I have had success welding stainless by arc welding with stainless rods. ..you get a mirror finish, but beware of the flux as it removes itself from the job quite violently as the job cools!
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Re: A new hotwell for Rainbow

Post by barts » Sat Dec 02, 2017 7:31 pm

malcolmd wrote:What a neat solution. ...I think this might well find its way into Befur :-)

BTW I have had success welding stainless by arc welding with stainless rods. ..you get a mirror finish, but beware of the flux as it removes itself from the job quite violently as the job cools!
That's a good idea; I've done that with thicker material. This is prob. 18 gauge (~.050", or 1.27 mm) stainless;
somewhat difficult for me to weld w/ a stick. I have a MIG setup, but that would require a different gas bottle w/o any C02.
I recently picked up several pounds of stainless welding rod at a swap meet, happily enough, but it's 1/8" ( 3 mm),
rather too thick for this. I'll have to practice this with some really thin rods; it's very handy being able to weld
this thinner material. I see that rods are available down to .035", which makes welding thin material practical.

Thanks for the suggestion!

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Re: A new hotwell for Rainbow

Post by Lopez Mike » Sun Dec 03, 2017 12:33 am

Some years ago I soft soldered some stainless steel for an electronics project. I have no idea of the metallurgy of the stuff but it might be well worth fooling about with it. I didn't even use acid flux. Just ordinary rosin for electrical connections.
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