The Steamboating Forum

Hey Bart

Some design comments on the Lamont... you'll need to insure turbulent flow (say Reynold numbers above 10000 or so) to realize the advantages of the pumped circulation. This means about 2 gpm in 1/2" pipe - not a lot, but it needs to happen so long as you have fire. I'd not consider solid fuel suitable for a Lamont boiler w/o redundant pumps & reliable pump power; I'd also consider multiple pumps required (or some other form of aux. power) if in open/dangerous (tides/currents/surf) waters. Remember that the pump only needs to produce a few psi pressure head - but the seals need to take full boiler temperature and pressure, which is what makes finding such pumps difficult. Also, the water you're trying to pump is about to flash into steam, so the design of the pump needs to require a very low NPSH.
From Wikipedia: "Careful design is required to pump high temperature liquids with a centrifugal pump when the liquid is near its boiling point." You can use a positive displacement pump, but gear pumps are probably out since any scale or such in the boiler water would soon trash the pump. A 2" bore, 1" stroke double acting opposed piston pump with lift checks and Viton or Teflon packing running about 100 rpm would do the trick - but it has to run all the time, even when the fire is just lit, so you'll need to use an electric motor.

You said that a piston pump could be used? Today I am replacing the lower seals “again” in one of our barrel pumps (the monkeys did not clean out the 3M last night) and I had a thought.

This pump mechanism is double acting by way of a stepped piston. It has two sets of V rings, an intake ball valve in the foot and one inside the piston itself. The volume of the lower chamber is higher than that of the upper chamber so that when the pump cycles it moves material on each stroke. It has no packing gland since it is mounted inside the container so if it leaks a bit no big deal. The pump is driven by a 5 to 1 air motor that will move material the consistency of honey at little over 3 gallons a minute at 500 psi through a 1/2” hose.

What about mounting an entire pump unit “inside” the boiler loop. Say in a ported tank that could be isolated by valve next to its twin encase of pump failure. That way ya get a main pump and a backup or you could run both for a boost when needed. At 2” bore x 1” stroke the pump housings would not be overly large or heavy.

My thinking is to build something like this in bronze or? With Teflon rings and place it inside a suitable housing. Say 2,5” schedule 80 with flanges and valves appropriate for the job. The pump could be built lighter that way since it is only moving the water inside the pressure loop. The unit would be driven like those feed water pumps are with something slow and dependable.

Ya think an arrangement like that would move enough water to keep a steam engine of around 3+5 x 4 running? And yes I am terrible at math, I do better with things I can wrap my hands around.

Cheers,
Scott

A suitable pump could be made with two lift checks, a tee and some pipe - it is no different than a feed water pump.

I would make a double-ended pump so that I could balance the pressure forces, and I'd use teflon packing - not o-rings.
Perhaps a piece of one inch stainless or old bronze prop shaft running back and forth in some suitable bushings; the ends
would go into packing glands. I'd definitely use a proper strainer that would remove any scale before it got into the checks.

It would need to be well-insulated w/ fiberglass; you'd need to drive it w/ an electric motor (or handcrank) to start
the boiler. You'll want ample water capacity.

It's definitely an experimental unit, though.

- Bart

Hey Bart

I'm not sure I understand what a double ended pump is. From the description I can work it out but it would seem to me that having packing glands and bushings in that arrangement would cause a lot of drag on the pump as well as leak potential.

I tried to find an exploded view of the pump I was talking about but only found a PDF. The parts view of the pump MODEL 223-954 is not the greatest but it was all I could find at the moment. http://www.samkieng.com/doc/pdf/307026j.pdf

The actual pump body is 319 it has an upper section that is roughly a third less than the diameter of the lower section. The piston is sized at both ends to ride in the cylinder on Teflon guides (308,312) small end (307,308,307) and large end (311, 312, 311) and seal with Teflon cups. The drive rod (320) is a little under a half inch and is connected to the air motor (301) through a ball and socket assemble (not shown). Except for the one O-ring at (322) there are no other seals on the pump itself and the only reason the O-ring is there is to keep the end from rattling off inside the barrel.

The fluid is drawn into the lower chamber when the piston is pulled up through ball and seat (305,317). When the piston is pushed down the fluid is pushed through the second ball (304) into the upper chamber which is smaller than the lower one therefore part of the fluid is forced out of the pump through the three small tubes you see at the center of the upper and lower cylinder.

The only place I would need a packing gland is on the drive rod. The actual pump part would all be inside a housing connected to the boiler circuit through shut off valves so the pump could be isolated for repairs.

The air motor (301) would be replaced by a steam piston and valve arrangement like that found on a feed pump. The entire pump would be around 2.5 inches in diameter and about 12 inches long. The steam drive section I am not sure of yet but I imagine with some sort of steam regulator like the one you built a 4" slow moving piston would do the trick running at 50 or so psi. And yes there would be a fine strainer on the intake of the pump.

As far as starting the boiler from cold goes I am working on it.

Cheers,
Scott

Scott,
If I undrestand correctly, what Bart is talking about is similar to the pumps on the older(1960s) steam jennies, a solid shaft with a pump chamber on each end and a crosshead in between. Later model jennies use catt pumps which may be an alternative for this application. After all a steam jenny isn't much more than a forced circulation monotube boiler.

Dave

Hey Oilking

Ok I get it, sorta like the feed pumps I see on some of the steam engines main shaft where they have a scotch yoke in the middle driving two pumps. That is a possibility but you have a bit more friction using that method. I am considering an inline arrangement to cut down on the contacting parts and so I can mount the pump inside the boiler loop. That way I only have one packing to manage and the pump could be insulated easier.

A rotary seal would be as easy to implement but how would a pump like that work under very hot water? And if I don't put the pump inside then I have more surface area through pipes and such to loose heat from.

The pump I am leaning towards is designed to work in liquids that make it impossible to lube the pump. The piston has two Teflon pucks that touch the metal and it is driven along the axis so there is very little if any scrapping force against the cylinder walls. That setup would have only two connections to the boiler and both would be through valves. It would make isolating the pumps easier as well as repairs in the field.

Throw more ideas at me, two heads are better than one.

Cheers,
Scott

Oilking wrote:Scott,
If I undrestand correctly, what Bart is talking about is similar to the pumps on the older(1960s) steam jennies, a solid shaft with a pump chamber on each end and a crosshead in between. Later model jennies use catt pumps which may be an alternative for this application. After all a steam jenny isn't much more than a forced circulation monotube boiler.

Dave

Yes, that's what I had in mind. Since the water is under 200+ psi of pressure, using only a single acting pump would place the full boiler pressure to work against the crank; with a double acting pump the boiler pressure would be canceled out and the only force on the crank would be the pressure head supplied by the pump.

- Bart

Hey Bart

That makes sense, when the valve opens on one side to pull in water it comes in under pressure and when the valve opens on the other side to push out water it has the boiler pressure to push against thus canceling any unworkable load on the crank.

What I am most concerned with are the large diameter packing glands to deal with on each piston as well as wear on the cylinder walls, or slide area if the pistons are centered in the bore and do not touch the cylinder walls. There will be some mechanism by which rotary motion is converted to linear and that mechanism will need oil.

The pump I described has no packing glands, does not need rotary motion converted to linear and requires no lube. And there will only be a single packing gland on a 1/2" shaft.

I do like that idea though as a hand operated starter pump/feed water backup pump. With a set of valves it could be used for either, thus supplying the required backup hand pump and starter pump all in one.

Maybe not... as a hand powered feed pump it would have atmospheric pressure on one side and boiler pressure on the other. So I guess it would depend on how much force it would take to pump the feed water in against boiler pressure. Will have to think about this one.

At the moment I think the water heater I have has a tube size of 3/8". I am not sure how long the tube is over all though but when I find my scale and dig the coil out of storage I will know for sure. The heater unit it came out of was used for heating water after a pressure washer that ran at 4.5 gpm at 2200 psi.

Since that is the mono tube boiler I am going to do the experiments with at first will the 2" dia x 1" stroke pump you suggested work ok for this?

Scott

Hey Guys

I have been getting miscellaneous parts together to build a test pump for a little fun, since I am at least a year away from starting on my Steam Launch project. So my first question was could I put a pump inside a boiler system that will do the job needed. The second was what kind of pump? I got those questions pretty much worked out now and I have been collecting parts.

Parts of the test pump are stainless steel, parts are steel and a couple pieces are brass. So before I start assembling parts I had a question for Ya'll. How well will silver solder hold up inside the boiler? I am only doing some tests for now to see how well the pump works. Afterwards I will machine a nice little iron unit for permanent use.

Scott

" How well will silver solder hold up inside the boiler?"

It will hold up very well, because the other metals you mention will provide galvanic protection of the silver solder, and these other metals will be sacrificed to corrosion. Probably not an issue in the short term, however the use of sacrificial zinc anodes mounted inside the boiler may be a good idea.

I've had a boiler w/ silver soldered joints running for 18 years now. A zinc anode would prob. be a good idea, but that's tricky surgery at this point.

- Bart