Help sizing a boiler feed pump

[jx3]

Hi I am a new steamboat owner and new to steam, I have a small 15ft boat with a Taylor single cylinder engine 2.25" X 2.5" with a copper blackstaff 5A water tube boiler at 100psi burning kerosene. I have never run the boat and I am in the process of redoing all the pipe work and going through the engine. The boiler feed pump that was on the boat is a hypro pump driven by belt. I have read on this forum that these are very reliable pumps, however the pump seems massively oversized for such a small engine. I was thinking of trying to build a small piston feed pump driven off the cross head or possibly from an eccentric. I do not know what quantity of water I need to supply to the boiler, typically what kind of RPM is a small launch engine like this running at while cruising and how much water would the boiler use. Any help would be much appreciated
Kind Regards John
Niagara Falls Canada

[Peter H]

My engine is 2 1/4 by 3 and runs at 100psi max. My pump is single acting and is 5/8 bore with a 1 1/4 stroke. The pump runs at 1/4 engine speed.

[RNoe]

John:
Welcome to this discussion board.

I would guess that your engine will likely operate in the 300 to 400 rpm range, depending on the prop used, and other unknowns.
An "oversized" water pump is not a problem, due to "standard" plumbing practices that should provide a water return line with a valve to control what proportion goes into the boiler. Being able to supply more water than required is always better than an insufficient amount.

I have that proportioning valve setup on both my steam locomotives and my 17 foot long steamboat. It has a float valve in the hot well tank which automatically proportions the boiler water level, based on the hot well level.

Adjusting boiler water level is quite simple with this water proportioning valve, especially on a steamboat which generally operates at a more steady state than a railroad locomotive.
Food for thought.
Russ

[Lopez Mike]

A hot well float is needed for reasons of seamanship as well as convenience. It's easy to overlook that fact that a skipper has a world of things to deal with beyond the power plant. Anything, especially something as simple and cheap as a hot well float valve, that allows you to be a better helms person is not to be left at the dock.

Mike

[TahoeSteam]

Take the rated HP of the engine, multiply by 33lbs/hr, and divide by 8.33lbs (gallon). That will give you a rough estimate for the gallons/hr your engine will consume. A gallon occupies approximately 231 cubic inches and 3.8 litres... One can size their displacement pump by knowing the rpm and space it is displacing/revolution... I would suggest sizing for at least 150%, if not 200%, capacity as there are always leaks and kiddos who need to hear steam whistles.

Unfortunately I'm south of you and still stuck in archaic measurements. You'll have to convert to your measurements of choice.

Niagara On The Lake would be a lovely spot to steam. I rode on the S.S. Pumper there after she moved from Ottawa.

[TahoeSteam]

Take the rated HP of the engine, multiply by 33lbs/hr, and divide by 8.33lbs (gallon). That will give you a rough estimate for the gallons/hr your engine will consume. A gallon occupies approximately 231 cubic inches and 3.8 litres... One can size their displacement pump by knowing the rpm and space it is displacing/revolution... I would suggest sizing for at least 150%, if not 200%, capacity as there are always leaks and kiddos who need to hear steam whistles.

Unfortunately I'm south of you and still stuck in archaic measurements. You'll have to convert to your measurements of choice.

Niagara On The Lake would be a lovely spot to steam. I rode on the S.S. Pumper there after she moved from Ottawa.

[TahoeSteam]

Repost

[RNoe]

You can say that again!

RussN

[TahoeSteam]

Bloody browser on my phone keeps showing an error message after hitting submit... Thought it didn't work until I refreshed the page. Then the forum setup (love the new look by the way Simon) won't let one delete more than their most recent post, and only edit their second most recent.

[jx3]

Thank you very much for the replies to my question I found the the comments very helpful and also the posts on the thread "Best RPM for plunger pumps" have given me some ideas to try and make a small plunger style boiler feed pump. If that doesn't work out I can always go back to the hypro pump.
Regards
John