DetroiTug's Tug is going together

[artemis]

Ron,

Thanks for the input on the economizer. What would be the best check valve for that application? What type? I need something that seals 100%. Apparently a the pump checks are leaking through, allowing steam pressure in the economizer to push all the water out of the pump system...

-Ron

Sorry to be so long in replying. I've used a lightly spring loaded lift check in the past. Buuuut, because of our "little boats" you need to "throttle" the "lift" to less than 3/32" otherwise the check will take toooo looong to close completely leading to erratic feeding. For any engine up to 8 HP this should allow plenty of opening (remember the pipe size of the suction line should be at least as big as that of the discharge side). Conbraco is a major supplier; they're owned by Apollo Valves (the quarter-turn-ball-valve people). A number of folks use just a "swing" check. Sure, they're inexpensive but they like to stick or not open properly. I'll spend a few $ more and have something reliable. If you have no water in the boiler you also have problems! And now they're in-line so the space requirements are very minimal. Visit their on line website at:http://www.apollovalves.com/ - and the in-line checks don't seem to need to be "throttled".

[DetroiTug]

Ron,

That is exactly what we put on there, an inline Apollo check valve, this one right here:

http://www.mcmaster.com/#standard-check-valves/=dxktsv

# 47885K71

Works perfect.

The good news is, the economizer works great, went back to the 20X20 prop, we held 60 - 70 psi no problem for about 4 hours, then I noticed pressure dropping and water on the top tube sheet. The economizer started leaking. So I bypassed it and it ran the rest of the day, same old deal, fighting to keep 30-40 psi. Revisiting the plan for a steel wound coil that I can weld in to the supports instead of wire tying the copper as it is. Just too much shock to be tied in, it needs to be welded. Thinking more on this, the tightly wound coil inside the heat exchanger has worked great, no leaks or banging. maybe I need to just make something similar inside the hood. A tightly wound coil in a loop? Also going to add a larger air cushion.

Went to the Saugatuck Michigan meet yesterday, only four boats showed up. I took some pics of the QA GILLMORE steam tug that sold on Ebay, the one stuck in the mud? It's still there. We steamed all around it and wound up running aground ourselves. Luckily Chief had about 80 on the clock backed herself off no problems.







In the background is the SS KEEWATIN.

From the wiki:

""The SS Keewatin is a passenger liner that once sailed between Port Arthur / Fort William and Port McNicoll in Ontario, Canada. She carried passengers between these ports for the Canadian Pacific Railway's Great Lakes Steamship Service. The Keewatin also carried packaged freight goods for the railway at these ports.[1]

Built by Fairfield Shipbuilding and Engineering Company in Scotland as Hull No. 453, the Keewatin was launched 6 July 1907 and entered service in the following year. She ran continuously for almost 60 seasons, being retired in 1966.

Like many passenger ships of that era on the Great Lakes, the Keewatin and sister ship SS Assiniboia operated under stringent regulations imposed for wooden cabin steamships following the SS Noronic disaster in 1949. Doomed by their wooden cabins and superstructure, these overnight cruisers lasted through the decline of the passenger trade on the lakes in the post-war years. As passengers opted for more reliable and faster modes of travel, the Keewatin and her sister ship were withdrawn from the passenger trade in 1965, continuing in freight only service for another year.""

-Ron

[artemis]

Ron,

That is exactly what we put on there, an inline Apollo check valve, this one right here:

http://www.mcmaster.com/#standard-check-valves/=dxktsv

# 47885K71

Works perfect.

The good news is, the economizer works great, went back to the 20X20 prop, we held 60 - 70 psi no problem for about 4 hours, then I noticed pressure dropping and water on the top tube sheet. The economizer started leaking. So I bypassed it and it ran the rest of the day, same old deal, fighting to keep 30-40 psi. Revisiting the plan for a steel wound coil that I can weld in to the supports instead of wire tying the copper as it is. Just too much shock to be tied in, it needs to be welded. Thinking more on this, the tightly wound coil inside the heat exchanger has worked great, no leaks or banging. maybe I need to just make something similar inside the hood. A tightly wound coil in a loop? Also going to add a larger air cushion.
-Ron

Many "hobby" steamboats on the west coast of the USA wound a copper tube coil that nicely "sleeved" inside the stack. Scavenges almost as much heat (maybe more?) as an economizer fitted in the smoke hood area. Al Giles' Crest used this technique (Crest had a Merryweather "B" boiler) and over a 20+ year period he only had to replace the copper coil once - he used SS the second time. As have several others who have used this technique over the years. Al was a lead millwright at the Olympia Brewery ("It's the water...") and an early experimenter with such things as teflon steam packing and piston rings (back in the early 1960s). He initially used the teflon rings in the compressors used in the brewing processes - all subject to FDA rules regarding lubricants and foodstuffs - and figured that the concept would work well in his hobby. It does.

[87gn@tahoe]

To prevent the coil from expanding and contracting, on can install a "water hammer arrestor" which are available commercially or one could make their own as my father did out of copper tubing, hammering in a nice dome shape to the top.

[DetroiTug]

Ron, Wes,

Thanks for the input, I'm going to try one of those shock arrestors, if the problem persists. There is one made by Buffalo Chief, they call it a mini. It is intended for icemaker water lines for refrigerators. Has a piston with O-rings.

I'm really puzzled about the water on the tube sheet - read on.

This morning I broke all the unions and lifted the funnel/smoke hood to exchange the economizer. I even spent an hour wrestling the new 6 ft of 1/4" pipe replacement economizer in to a tennis racket shaped once-around coil before even starting.

I raised the hood and could not see any places on the copper coil that looked cracked or rubbed through. Tested with some compressed air, it isn't leaking.

Taking in to consideration everything that happened last Sunday: The pump hammering, the relief valve on the pump spitting on every stroke. Thinking it was the feedwater flash boiling in the economizer and increasing the head pressure, I was going to just increase the pumps relief valve pressure, then it dawned on me, this seems more like a simple restriction in flow. I grabbed one of the extra 1/4" NPT Gauge cocks, and sure enough the passage way through is tiny. It looks to be about .140" in diameter, this is what is causing the excessive pump pressure and hammering. I swapped out the valves for standard 1/4" ball valves that have a .375" passage. That should take care of that. Comparison in area of each: .140"d = .015 sq-in. / .375"d = .110 sq-in big difference, about seven times the flow rate.

Trying to figure out why I'm getting water on the top tube sheet again, and why did it appear to stop after bypassing the economizer, when the economizer wasn't leaking. I had the manifold drains open and the old condensation problem has returned. I'm just wondering if it's because the water temp was a bit cooler, the boat running a bit harder (Higher exhaust steam velocity carrying condensate further), with the better supply of steam.

Pressure tested the whole feedwater piping from the main pump to the feedwater inlet at the boiler, nothing is leaking. I'm puzzled.

One would think exhausting out the stack would be a simple approach, Could have set up a condensing system with little more effort.

-Ron

[87gn@tahoe]

Probably wouldn't be a bad idea to hydro test the boiler, just to eliminate that possibility.

1/4" feed line seems awfully small too.

[DetroiTug]

We were stopping a lot, there would have been some hissing or dripping in to the firebox etc, only happened when pumping feedwater under way. But, you're right, it's always a good time to hydro the boiler. Can't do that too much.

The 3/8" copper line seemed fine prior to the economizer addition. Only 1/4" in the feedwater circuit is 1/4" pipe, close to 3/8" copper ID. Only running the 3/4 X 3/4 feedpump, it keeps up with the boiler. Typically it runs about half the time when the boiler is in the 60 psi range. There is a pressure gauge on the feedpump, when bypassing it reads boiler pressure, bypass closed it bounces + 20-30 psi on every stroke. Good indicator it's pumping water.

Thanks, Ron

[87gn@tahoe]

Oh, okay, I thought you meant 1/4" tubing, made me . 1/4" NTP is pretty close to 3/8" tubing.

Strange about the water on top of the boiler...

[artemis]

I've got a whole bunch of thoughts (but trying to keep them together is like herding cats).

1. I've never heard of using 1/4" pipe for economizer pipe in a 22' steamboat. Soooo - What is the volume of water in cubic inches that you pump through the pipe in one second? What is the area of the "hole" that is the inside of the feedwater/economizer piping? Calculate the speed of the water in feet/second. An old text I have says that boiler feed water speed should be no more than 5 feet/second. But that's for 1" or larger pipes. Probably lower for smaller pipe (wall resistance and turbulence). Be careful about changing pipe volume from one size to another and then back again; same thing with materials (smooth surface, rough surface). Strange things happen.

2. Gauge cocks: Frequently gauge cocks have a "snubber" built in. This type of valve should ONLY be used between the line and the gauge, nowhere else. This snubber is basically a "reducer" that supposedly reduces the "wild, swinging" of the gauge needle caused by pumping operations. I've found that using a needle valve works better on our "little" installations with smaller i.d. "pressure lines.

3. As the "hissing" and "spitting" only seemed to occur when pumping feedwater underway maybe another part of the earlier noted difference occuring when introducing cool feedwater and cooling the stack gas, thus allowing the exhaust steam to:
a. cool more in the feedwater heater;
b. cool even more on contact with the cooler economizer;
c. produce a gray "rain" that permanently stains clothes and cabin tops.

Isn't hobby steamboating fun It's also why steam engineering is a separate study from "fluids and hydraulics".

[DetroiTug]

Ron,

The economizer is about a foot lower than the actual end of the engine exhaust pipe inside the funnel. The economizer does touch that pipe, but only a few places, and it would be hard to conclude there is much heat transfer going at those contact points.

The feedpump is just .75 X .75 Each stroke is moving .442 cu-in of water. At 240 RPM it's pumping about 1.7 cu-in per second. 3/8" copper with a .04 wall has an internal ID of about .295". The area is about .07" square inch. 1.7/.07 = 25 linear inches. So the velocity is about 25 inches per second. And that is not including losses in the check valves at the pump. Probably about 80% efficient. About 20 inches per second through 3/8" tubing.

After replacing the valves, I'm going to take it out and run it and see how it does. I should have done that today. Too late now

-Ron