VFT water level
- Lopez Mike
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VFT water level
I am considering adding turbulators to my Beckamn VFT-30 boiler. I've been running it for a couple of years. One of things I have not changed since I bought the boat is the vertical position of the sight glass. Today I made some measurements for the first time.
The tubes are 14" long. The bottom of the glass is 1" above the lower tube plate. The top of the glass is 9" above the bottom tube plate. There is about 3 or 4" above the top of the glass before there is overflow into the steam pipe.
I've been steaming with 4 to 5" of water showing. 5 to 6" above the tube plate. It's been steaming well. I sometimes run it as high as 6 to 7" on the glass. The boiler is a bit less responsive to load and firing when I'm running a higher glass.
My power plant is limited by the boiler output thus the turbulator project. Would the boiler evaporate more if I fired it at a higher glass? I would think so but I'm not sure at all.
If I limit the turbulators to the top of my normal water level, I would like to make them the right length. Would there be a draft penalty to making the turbulators full length? Wood fired, by the way.
Thoughts?
The tubes are 14" long. The bottom of the glass is 1" above the lower tube plate. The top of the glass is 9" above the bottom tube plate. There is about 3 or 4" above the top of the glass before there is overflow into the steam pipe.
I've been steaming with 4 to 5" of water showing. 5 to 6" above the tube plate. It's been steaming well. I sometimes run it as high as 6 to 7" on the glass. The boiler is a bit less responsive to load and firing when I'm running a higher glass.
My power plant is limited by the boiler output thus the turbulator project. Would the boiler evaporate more if I fired it at a higher glass? I would think so but I'm not sure at all.
If I limit the turbulators to the top of my normal water level, I would like to make them the right length. Would there be a draft penalty to making the turbulators full length? Wood fired, by the way.
Thoughts?
If you think you are too small to make a difference, try sleeping with a mosquito.
Dalai Lama
Dalai Lama
- DetroiTug
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Re: VFT water level
Low water or high water?
I noticed when I was injecting water intermittently: Running low water, It was easier to make steam and the steam seemed to be hotter as there was more superheating going on in the upper exposed tubes. BUT, when I had to take on feedwater, the whole thing died quickly. And it was difficult to get it back under way.
I've found its better to keep the water higher in the glass and do not let the pressure fall below 60 psi. Just keep throttling back/hooking up and maintain the pressure/steam temperature. More work is to be had from hotter steam. The higher water level means higher volume of water ready to make steam which is not affected so adversely by the introduction of feedwater. Which should be added little and often. And through an economizer.
I use the Southworth now which provides constant feedwater level maintenance. THis is the best way to go, by some automatic means.
A needle valve bypass is pretty effective also. But it's impossible to set it precisely to the boiler demand, so it is a continual adjustment.
And of course, the fire, cant have enough. On the tug, if a log will fit, put it in.
-Ron
I noticed when I was injecting water intermittently: Running low water, It was easier to make steam and the steam seemed to be hotter as there was more superheating going on in the upper exposed tubes. BUT, when I had to take on feedwater, the whole thing died quickly. And it was difficult to get it back under way.
I've found its better to keep the water higher in the glass and do not let the pressure fall below 60 psi. Just keep throttling back/hooking up and maintain the pressure/steam temperature. More work is to be had from hotter steam. The higher water level means higher volume of water ready to make steam which is not affected so adversely by the introduction of feedwater. Which should be added little and often. And through an economizer.
I use the Southworth now which provides constant feedwater level maintenance. THis is the best way to go, by some automatic means.
A needle valve bypass is pretty effective also. But it's impossible to set it precisely to the boiler demand, so it is a continual adjustment.
And of course, the fire, cant have enough. On the tug, if a log will fit, put it in.
-Ron
- Lopez Mike
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Re: VFT water level
I use a hot well float so my water level just sits there for hours. Within an eighth of an inch.
If you think you are too small to make a difference, try sleeping with a mosquito.
Dalai Lama
Dalai Lama
- fredrosse
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Re: VFT water level
"Would the boiler evaporate more if I fired it at a higher glass? I would think so but I'm not sure at all."
ANS: Definately more steam production with the higher water level. As Ron points out, with a VFT there is less superheating surface when running with a higher water level, but that is not much of an issue here. Running too high a water level risks the issue of water carryover with the steam, so a reasonable steam space needs to be maintained.
"If I limit the turbulators to the top of my normal water level, I would like to make them the right length."
ANS: Remember that there is what is called "swell" in a steaming boiler, the actual presence of water, bouyed up by the boiling process, makes the effective water level (height of tubing participating in the boiling process) a couple of inches higher than what is indicated on the glass. For your boiler I would make the turbulators about 2 inches higher than the normally indicated water level for optimum turbulator effectiveness.
"Would there be a draft penalty to making the turbulators full length? "
ANS: Yes, the longer the turbilators, the more pressure loss.
Flat plate turbulators should have a twist in the vicinity of one turn in 8 diameters length. The main concern with solid fuel firing is fouling of the inside tube surface, and the ability to clean the tubes from soot buildup. Ideally the top of the boiler smoke hood should allow you to pull the turbulators and brush the VFT inside surface as needed. A strong steam lance, running at main steam pressure, can also clean the tubes fairly well, although this may get messy.
ANS: Definately more steam production with the higher water level. As Ron points out, with a VFT there is less superheating surface when running with a higher water level, but that is not much of an issue here. Running too high a water level risks the issue of water carryover with the steam, so a reasonable steam space needs to be maintained.
"If I limit the turbulators to the top of my normal water level, I would like to make them the right length."
ANS: Remember that there is what is called "swell" in a steaming boiler, the actual presence of water, bouyed up by the boiling process, makes the effective water level (height of tubing participating in the boiling process) a couple of inches higher than what is indicated on the glass. For your boiler I would make the turbulators about 2 inches higher than the normally indicated water level for optimum turbulator effectiveness.
"Would there be a draft penalty to making the turbulators full length? "
ANS: Yes, the longer the turbilators, the more pressure loss.
Flat plate turbulators should have a twist in the vicinity of one turn in 8 diameters length. The main concern with solid fuel firing is fouling of the inside tube surface, and the ability to clean the tubes from soot buildup. Ideally the top of the boiler smoke hood should allow you to pull the turbulators and brush the VFT inside surface as needed. A strong steam lance, running at main steam pressure, can also clean the tubes fairly well, although this may get messy.
- Lopez Mike
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Re: VFT water level
Thanks Fred. Good thoughts as usual.
I have easy access to the upper tube sheet. I'm making the units from 7/8" wide stock and the tube I.D. is 1" so what with the soft soot I get from soft wood fuel I don't expect to have any maintenance issues.
The stock is only .033 so it's a bit of a trick to get more than one turn in the length of a tube. I'm still experimenting with ways to twist them. One end in a vise and the other in my vise grips pliers is all I've tried so far. Tends to kink at the pliers end so I make them a bit long and whack them off.
I'll be steaming this weekend with turbulators and running a higher glass as well as experimenting with different orifice sizes on my stack blower. If I come up with any useful data on performance it will be a miracle!
I have easy access to the upper tube sheet. I'm making the units from 7/8" wide stock and the tube I.D. is 1" so what with the soft soot I get from soft wood fuel I don't expect to have any maintenance issues.
The stock is only .033 so it's a bit of a trick to get more than one turn in the length of a tube. I'm still experimenting with ways to twist them. One end in a vise and the other in my vise grips pliers is all I've tried so far. Tends to kink at the pliers end so I make them a bit long and whack them off.
I'll be steaming this weekend with turbulators and running a higher glass as well as experimenting with different orifice sizes on my stack blower. If I come up with any useful data on performance it will be a miracle!
If you think you are too small to make a difference, try sleeping with a mosquito.
Dalai Lama
Dalai Lama
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Re: VFT water level
One consideration of running with a high glass is that there is less steam reserve should a quick increase in power be required. Much less of a problem when running at a constant speed as long as 'feed' keeps up with 'need'.
Retirement is about doing what floats your boat!
A BODGE : - A Bit Of Damn Good Engineering.
A BODGE : - A Bit Of Damn Good Engineering.
- Lopez Mike
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- Location: Lopez Island, Washington State, USA
Re: VFT water level
I don't understand why there would be less steam reserve with a high glass. If anything it seems as though having all that extra water up to temperature and ready to evaporate would make for more reserve.
I must think about this. A lifetime of fooling with steam and I still have to think about stuff. Old age is galloping in.
I must think about this. A lifetime of fooling with steam and I still have to think about stuff. Old age is galloping in.
If you think you are too small to make a difference, try sleeping with a mosquito.
Dalai Lama
Dalai Lama
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Re: VFT water level
It boils down (sorry, bad pun) to what capacity is left without water, if you demand a lot more steam suddenly, steam won't be made instantly, there will be a time lag, the reserve has to be big enough to cope without too large a drop in pressure.
Retirement is about doing what floats your boat!
A BODGE : - A Bit Of Damn Good Engineering.
A BODGE : - A Bit Of Damn Good Engineering.
- barts
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Re: VFT water level
The length of tubes that aren't covered by water are basically doing nothing for your steam production. If your water level is half-way up the tube, you've cut the boiler size in half. As others have mentioned, you need enough steam space to allow for the water level to rise when steam production increases - say when you crank the throttle open or blow the whistles. Some boilers do this more than others; too much and you'll send a spray or a slug of water into the engine.
Carry the water as high as possible w/o carry-over, and you'll maximize heating surface.
Since your engine will use all the steam the boiler will produce, try setting the throttle to a comfortable cruise and try building the fire nice and hot, and keeping it that way. Does she reach a higher equilibrium pressure with the boiler water level kept higher?
This will let you know what is going on... or, at a minimum, give you some fun steaming time
!
- Bart
Carry the water as high as possible w/o carry-over, and you'll maximize heating surface.
Since your engine will use all the steam the boiler will produce, try setting the throttle to a comfortable cruise and try building the fire nice and hot, and keeping it that way. Does she reach a higher equilibrium pressure with the boiler water level kept higher?
This will let you know what is going on... or, at a minimum, give you some fun steaming time

- Bart
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
- Lopez Mike
- Full Steam Ahead
- Posts: 1925
- Joined: Wed Dec 07, 2011 6:41 am
- Boat Name: S.L. Spiffy
- Location: Lopez Island, Washington State, USA
Re: VFT water level
I dunno Mike. I'll have to think some more about reserve steam when opening the throttle.
As far as I know, when the pressure drops even a teeny bit more water boils instantly to make up the difference. The reason the pressure drops is because the temperature of the water drops gradually unless the fire is stoked up. I don't see how the steam already in the boiler adds much to the reserve capacity. It has very little thermal mass unlike the water. The steam does have stored energy. Entropy, enthalpy and all that stuff that makes my eyes glaze over. But I'm pretty sure its' small potatoes compared to the liquid.
I'm waiting for Fred or Bart to come in now and crush us both to silence.
As far as I know, when the pressure drops even a teeny bit more water boils instantly to make up the difference. The reason the pressure drops is because the temperature of the water drops gradually unless the fire is stoked up. I don't see how the steam already in the boiler adds much to the reserve capacity. It has very little thermal mass unlike the water. The steam does have stored energy. Entropy, enthalpy and all that stuff that makes my eyes glaze over. But I'm pretty sure its' small potatoes compared to the liquid.
I'm waiting for Fred or Bart to come in now and crush us both to silence.
If you think you are too small to make a difference, try sleeping with a mosquito.
Dalai Lama
Dalai Lama