The Steamboating Forum

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Boiler questions:
I have removed & dismantled the boiler over the last two days. It seems to be built as I have read the Blackstaffe boilers are made.

The insulation looks to be the semi solid fiber type that should have had an inner layer of steel but was exposed to the fire - not pretty. I intend to use new insulation with an inner shell. Would stainless steel be a good choice for the inner shell?
What would be a good insulation material that can be bought in a small quantity?

I need to add penetrations to the boiler to accommodate the safety valve, gauge & whistle. I have mocked up locations for 2 Threadolets in some of the pictures. Does this layout look OK? The gauge, whistle & vacuum breaker would share one penetration. The throttle comes off the steam dome.

Is there an easy way to remove oil soot from this boiler? It has been run on kerosene.

I have many other questions but this will be a good start.

Thank you,
Jack



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The insulation looks to be the semi solid fiber type that should have had an inner layer of steel but was exposed to the fire - not pretty. I intend to use new insulation with an inner shell. Would stainless steel be a good choice for the inner shell?
What would be a good insulation material that can be bought in a small quantity?

I've used both 304 and 321 stainless (which I found scrap); .020 or so works fine. Both have worked well. Don't let the fire grow to the point where it hits the inner casing and you won't have any issues with either one. Fiberfrax or kaowool work fine for insulation; if you can't find it locally these folks are pretty handy:

http://shop.clay-planet.com/inswool-cer ... -foot.aspx

I need to add penetrations to the boiler to accommodate the safety valve, gauge & whistle. I have mocked up locations for 2 Threadolets in some of the pictures. Does this layout look OK? The gauge, whistle & vacuum breaker would share one penetration. The throttle comes off the steam dome.

Pictures are here: http://s951.photobucket.com/user/innco/ ... how/Boiler

The layout looks ok. These boilers are small jewels; too much large diameter piping isn't needed in my opinion. Err on the side of 3/8" rather than 1/2" if you can. A pressure washer will remove the soot pretty handily; a wire brush will help if need be.

- Bart

For the fireside of the boiler casing. stainless steel is very nearly the only reasonable choice, other exotic alloys are available, but they cost much more than stainless steel. When fastening stainless in the boiler casing, be sure to have some room for expansion of the stainless sheet. Stainless steel expands about 50% to 80% more than ordinary carbon steel for the same temperature rise, but the stainless will most probably see a temperature rise far greater than the outer steel lagging and boiler frame. Allowing for about 0.1 inch expansion per running foot of inner casing will do. Use stainless fastenings here, ordinary steel rivets or screws will waste away over time, depending on how high the temperatures get. The fastening scheme needs to consider free thermal expansion of the stainless steel sheets, if not the stainless might buckle when heated. The boiler pressure vessel, made of carbon steel, and with a maximum temperature of only about 350F will expand much less.

ASTM SA-105 Thread-o-lets for boiler connections have enough thickness in them to inherently reinforce the penetration drilled in the boiler pressure vessel walls, so they can be placed on just about any part of the vessel with good integrity. Welding should be full penetration type, the details of the welding requirements are discussed at length on previous threads of this forum.

Good to see you are paying close attention to these issues, much better chance of getting it right the first time.

One question, what "Vacuum Breaker"?

The "vacuum breaker" , --- I am accustomed to calling that a vent line/valve, no matter either way.

"Economiser which consists of a 1 1/4" copper pipe above each bank of tubes & joined by a 1/2" copper pipe across the top drum. Does this appear to be satisfactory? It is, I think it is intentionally, very free to move around a bit on its own. It has a 1/4" check valve on its inlet and in the outlet line to the boiler." --- That is an OK setup, provided there is no isolation valve that could separate the economizer from the boiler safety valve. I have worn a hole thru a copper economizer tube that was rubbing against some steel in the smokebox, watch out for this. Not dangerous but can shut you down for an outing.

"there is about 1" of Fiberfrax between a stainless steel inner shell and a mild steel outer shell, would it be safe to lag the outside with wood? Is there something that should go between the outer shell and the wood? My concern is, as you can imagine, having the fire only on the inside of the boiler!" --- Assuming 700F on the stainless inside the boiler, I get about 400F maximum wood temperature (inside surface of wood). With another inch of insulation, (kaowool or even common house fiberglass insulation blanket), then the wood would see only about 300F maximum. I know wood is OK with 300F, and 400F may char it somewhat, I don't know. A few layers of ordinary kitchen aluminum foil between the outer steel casing and the wood will bring down the maximum wood temperature to about 350F, and not make much thickness compared to the fiberglass insulation at 1 inch thick.

If you want (and will not be punished by the keeper of the oven for your actions), you can put some small piece of wood into the oven at 400F to see how it holds up. I once put some pizza in my oven at 550F but forgot about it for 5 days, and it got plenty charred, but did not actually catch fire. But that was just after the first divorce, and it was entirely "my" oven, so no punishment for me.

My experience has been similar to Fred and others. Inner liner of SS + 1" of Kaowool + outer cover of about 24 gauge SS is tooooo hot, but can be covered with oak (less natural oil than teak) lagging and not scorch too badly - still very hot to the touch though. Remember the safety of your passengers. Little ole ladies get testy if you burn them.

"Could I run the bypass line directly to the makeup water container & eliminate the stand pipe?" ANS: Yes

"Or could the bypass line go to a tee in the water feed line to the pumps?" ANS: Yes, OK and probably less piping. On my boat the bypass line just recirculates across the pump. On high power pumps this recirculation line could overheat, so it would be routed back to a larger makeup water tank that is capable of absorbing much more energy before things get overheated. But on our small steam plants this is not an issue.

"Would it be acceptable to place the feed water gauge on a tee placed at the inlet end of the economizer?" ANS: Yes, pressure gauge anywhere from pump discharge to economizer inlet.

If you have reciprocating pump that is capable of over-pressurizing the system, then be sure to have a relief valve on the discharge of the pump if there is any valve that might be closed between the pump discharge and the relief valve.