My new boiler - a watertube-type

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dampfspieler
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My new boiler - a watertube-type

Post by dampfspieler » Thu Dec 26, 2019 12:28 pm

Hello,

Pete offers some coils and a bit paperwork for a SBA-blackstaffe-type that i have bought. So i had a problem. What type of boiler should i built for my steam boat project, a Blackstaffe-Three-Drum or an OFELDT?
I have read a lot of articles and asked my experiences with other boilers i have built. So i have found a slightly modified OFELDT-boiler would be the best choice.
I built a small OFELDT for experiments in 2007 - I call it LOCKENWICKLER (Men need a name four her toys) - and an other LIFU with a very mighty overheater for a 7 1/4" Clishay.

Dietrich_Avatar.jpg
The experimental OFELDT-Boiler "LOCKENWICKLER"
Dietrich_Avatar.jpg (23.07 KiB) Viewed 6585 times
WiKe021kl.jpeg
The LIFU-Boiler "Seegurke" (sea cucumber)
WiKe021kl.jpeg (36.07 KiB) Viewed 6585 times
WiKe068kl.jpeg
The overheater
WiKe068kl.jpeg (113.89 KiB) Viewed 6585 times

That were the basic designs for the new much bigger one.

Dietrich
Last edited by dampfspieler on Thu Dec 26, 2019 4:38 pm, edited 1 time in total.
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dampfspieler
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Re: My new boiler - a watertube-type

Post by dampfspieler » Thu Dec 26, 2019 3:23 pm

Hi,

I drew a little and that's the preliminary result.

Kessel_156450_SBA_kplt.png

Best
Dietrich
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Re: My new boiler - a watertube-type

Post by TahoeSteam » Sat Dec 28, 2019 1:32 am

Your design looks very nice. I think you will be quite pleased with a larger Ofeldt. Natural circulation is wonderful in them... Surely you've experienced how quickly they build steam and with such abundance.
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Re: My new boiler - a watertube-type

Post by fredrosse » Sat Dec 28, 2019 3:45 pm

Very nice work!

The bottom ( center main vessel / boiler drum )of the Olfelt boiler will tend to accumulate any scale, therefore it should not have an intense fire directly under this drum. Scale is a poor conductor of heat, and if high heat flow occurs in a drum section with scale, overheating of the metal of the pressure vessel can occur.

This can be accomplished by various methods:

If gas (Propane, C3H8) fired, make the burner circular, with no burner flame in the center of the burner.

If Oil fired, get a similar result, either with a circular burner, or with an oil flame directed tangential to the center axis of the boiler. Avoid flame impingement onto drum.

If wood or coal fired, make the center drum deeper, extending a little distance below the fire bars, so that flames cannot impinge on the bottom of the drum.

Insulate the bottom of the drum from intense flame with a stainless steel disc (or a couple of them one above another), forming a moderate heat flow barrier in this critical region.
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Re: My new boiler - a watertube-type

Post by fredrosse » Sat Dec 28, 2019 4:04 pm

Regardless of the method used to protect the bottom of the drum, effective scale removal from the lower drum is very important.

Put a blowdown connection inside the drum, extending right down to the bottom center of the drum, so that any scale/sludge/mud can be blown down and removed effectively. Exit connection at the top of the drum, so there is no pipe connection at the very bottom of the drum.

Tri-Sodium Phosphate (TSP) fed into the boiler to maintain pH at 9-10, this keeps the scale forming material soft for blowdown, as well as corrosion protection of steel boiler components. The Tri-Sodium Phosphate stays in the boiler when steaming, and only needs to be replenished when boiler blowdown has removed significant amount of boiler water inventory. I usually add about a spoonful of TSP into feedwater tank after blowing down most of the inventory in my boiler.

For a typical steam launch sized Olfelt boiler, with center drum 150mm - 200mm (6inch-8inch) diameter, the blowdown pipe should be 15mm - 20mm (0.6inch - 0.8inch) inside diameter, and terminate about 6mm (0.25 inch) above the bottom of the drum. Reverse washout flow with a strong water hose (or a pressure washer) can get the drum well cleaned, although this reverse flush is not necessary for ordinary blowdown after a day's steaming.
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Re: My new boiler - a watertube-type

Post by DetroiTug » Sat Dec 28, 2019 5:07 pm

The Ofeldt and Blackstaff are both good boilers which use the same type of coil. The coil is much more beneficial versus the vertical pipe as shown in the one picture. Approximately 5 degrees rise in the water tube it reportedly optimum angle for best natural internal circulation, which the coils inherently have. Reference Derr, Babcock and Wilcox, etc.

Personally I would opt for the Ofeldt, but it really depends on the application, the Blackstaffe can be applied and kept in the same configuration as the Roberts types.

The center drum of the Ofeldt is the Downcomer, it can't be all upwards circulation, what controls that is the difference in temperature, note that downcomers on many boilers are outside the firespace and some even outside the thermal jacketing, the greater the differential in temperature between the downcomer(s) and heated elements, the greater velocity of internal circulation. As Fred states, the burner should be either circular in flame pattern or some sort of deflector should be affixed to the bottom of the drum to limit impinged heat. On the Ofeldt for my Locomobile steam car, we did add outlets in the bottom of the center drum for blow down and water gauge glass, then attached a heat shield under them to prevent boiling and erratic gauge readings.

My opinion is that the Ofeldt was the best boiler design ever concocted. It isn't better in every category, but no other boiler defeats it in all categories nor balance. i.e. considering Cost, weight, labor, pound per hour steam generation versus heated surface area, reserve, footprint, vigorous natural internal circulation, control, etc. It is the best balance of all categories.

Steam systems design is a series of benefits and compromises.

-Ron
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Re: My new boiler - a watertube-type

Post by Lopez Mike » Sun Dec 29, 2019 12:38 am

As an aficionado of solid fuel, I think I'll stay with my vertical fire tube unit for now. Very forgiving and stable.
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Re: My new boiler - a watertube-type

Post by fredrosse » Sun Dec 29, 2019 3:58 am

Ron: "....the greater the differential in temperature between the downcomer(s) and heated elements, the greater velocity of internal circulation."

Actually, once the boiler is underway generating steam flow, there is virtually no differential temperature here, the generating coils and the downcomer liquid are at virtually the same temperature, the steam/water saturation temperature. What drives the circulation is the steam voids in the generating coils, making effective density in the coils very low compared to the almost complete liquid water situation in the downcomer(s). This large difference in effective density drives the circulation flow.
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Re: My new boiler - a watertube-type

Post by dampfspieler » Sun Dec 29, 2019 10:01 am

Hi all,

thanks everyone for your comments. They are helpful for my work.

I think the best burner for an OFELDT is the Lune Valley/Simpson-PARAFINE-PATENT-Burner. In this times it is a bit difficult to operate because of the bio content of the heating oil. I will burn gas (LPG or BUTANE) in a ceramic burner.

In the central drum is a deflector so there are two parts in - a steam generating and an other where water is separated from steam and the steam is calmed.

Here is an interesting article YARROWs-Boilers and his circulations experiments.

- Dietrich
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Re: My new boiler - a watertube-type

Post by DetroiTug » Sun Dec 29, 2019 7:55 pm

dampfspieler wrote:
Sun Dec 29, 2019 10:01 am
Hi all,


In the central drum is a deflector so there are two parts in - a steam generating and an other where water is separated from steam and the steam is calmed.


- Dietrich
Dietrich, I put a deflector in mine that directs the flow out of the top of the coils to a tube that extends down in the top, this deflects everything down, and then only steam will come back up in theory, I never get carry over water in the dampf line. My friend built a very similar kessel with no deflector or separator at all and he has no issues with it either, or that he has mentioned

-Ron
Last edited by DetroiTug on Sun Dec 29, 2019 9:06 pm, edited 1 time in total.
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