HotWell Sizing

[JonRiley56]

All,

I still do not have clarity on how to appropriately size a hotwell. Here is my situation:

* I have a 60 sq ft boiler that I beleve should be able to generate about 450 lbs of steam per hour at peak output, good fire etc.

* I am running a 5 hp single that I only anticipate requiring 240 lbs per hour at full steam

* at 240 lbs per hour I should be generating/using about 30 gallons of water/steam per hour or 1/2 gallon per minute (i am a math whiz !!! )

* I am condensing since I will be running on the ocean, so all of the "activity" is going to route through my hotwell. I wont be set up to pump make up water directly from the hull if needed. I will be carrying about 15 gallons of fresh makeup on board. If I exhaust that in an emergency I will add all of the liquid refreshments that remain.

It would seem that if I size the hotwell too small that it is going to be very turbulent. What is a reasonable number of turnovers for the hotwell per hour ? Clearly I wont be running at full steam all the time, but it seems like I should plan for the possibility. Also, should I plan to be able to have a resonable number of turns based on the amount of steam my current engine will consume, or the amount the bouler can supply ?

Assuming the full output of 450 lbs, or ~ 60 gallons per hour, a five gallon hotwell would turnover every 12 minutes. Of course another issue then is finding an appropriate container for a hotwell that size.

I look forward to your sage advice, my prop shaft is supposed to be ready this weekend, and I am sanding 400 years worth of paint of my hull..........I hope I finish this project before the next milleniium.

jon

[Lopez Mike]

Others with more experience will no doubt have something to say but I think you are guessing way on the large side. I suspect that you would get by just fine with a couple of gallons capacity. It's not as turbulent as you might think in there.

[barts]

If you're worried about oil separation getting messed up due to turbulence, do that in a separate container... the hot well will be fine w/ one or two gallon capacity. You will not go through nearly as much water as you think....

- Bart

[fredrosse]

Large US power plant practice is 3 minutes full power available hotwell storage volume. These plants have automatic actions and alarms, which we typically do not have on a small steamboat, so probably the storage time should be extended for our steamboats. At 240 PPH steam generation, if you allow about 6 minutes hotwell storage, that is about 3 gallons, which should give more than ample time to react to possible shortages.

[JonRiley56]

Thanks guys, that helps a lot !!!

[SL Ethel]

I can't speak to the "right" size for a hotwell, but mine started life as a beer keg (15 gallons). This is for a 5 hp system maxing out at around 200pph. I was originally running non-condensing, so that tank doubled as a feed tank, which worked pretty well. For my condensing setup, I am cutting it down a few inches and adding a float indicator and a lid so that the whole business can go under a removable section of deck. In that incarnation it should have a working volume of around 5 gallons.

For something a little smaller, look on Ebay for things like commercial cooking equipment (e.g. rectangular soup chafing dishes). They come in a wide variety of sizes. A stainless stock pot could work well too, if you don't mind a round container. For something a little bigger, a 7.5 gallon pony keg could make a very nice hotwell.

Cheers,
Scott

[farmerden]

My hotwell is about 5 gal. It is divided into two parts [about 1/3 on one side and the remainder [2/3] -see You're not the only math whiz! In the smaller side there is a tray which holds a "sop-up paper" to catch any oil. The water then continues to the bottom of that tank where it is connected to the other side by about a 1" gap. The theory being that oil floats and can't get to the other side even if the "sop-up" fails.The returning water is merely a trickle out of the 1/2" copper return pipe. Like you I carry spare water in 1gal jugs and these can be poured into the hotwell when required.As i am running a steam atomizer and have numerous drips and other leaks ,I tend to use water at a regular rate.I have about 20 gal in bilge tanks and pack about 5 gal in bottles which gives me ample for a 3 day trip.As they say "I'd rather be lookin' at it ,than lookin' for it" when it comes to water!! Den

[JonRiley56]

So on the return from your condensate loop, does it come in to the hotwell above the water line ? I was reading some stuff I beleive in SBMSL or the british steamboating guide, and it mentioned the preference that the water returning to the hotwell come in below the water line. Their point was that you dont want to "aerate" the water after you have gone to the trouble of getting the air out of it.

It seems to me that it would make more sense to have it come in where you can see it run or trickle so you know something is happening.

Thoughts ?

jon

ps - I got abut 2/3 of the %$#*&## bottom paint sanded off my hull this weekend.........Hope to get the rest done during the week. I am shooting for putting the primer coat on the weekend after next.

[farmerden]

Jon That's correct,the water from the keel condenser just dripples on top of the "Sop-up" towelling. I'm not going to get into a debate about what's right or wrong-That's how mine works and I can see it working.So -touch wood-the boiler was made in 1987 and still going strong.Eventually the mud drums will fail and I'll replace the boiler! Den
PS Although it's too late now I hope you were wearing a respirator! I really felt ill when I scraped that stuff off of my bottom-sorry the boats' bottom