Feeding a water boiler/steam generator that's under pressure

[Evil Wizard]

Can anyone point me at info please or suggest good methods of keeping a steam boiler topped up? Its for my continuous stripper builds. (I've done a working 2", 3" and 6" column)

I have have intermittent results with a propane water heater boiler being filled from a bucket by way of a swing valve (like a non-spring check valve)
I've also had intermittent results with an electric internal element in a boiler being drained by a water lock. This only worked when when the boiler was being replenished by the wash falling down the column.

The general problem I find is that the pressure generated by the boiling water and steam holds closed the swing valve until the boiler is dry enough to burn the element. A closed swing valve means the replenishing water can't enter.

Thanks.

[Yummyrum]

Theres a pic around here somewhere in one of the continuos stripper threads . I think it was Swedishpride posted it . He copied it from Still dragon site .
Basically it was small boiler with an element in it . Next to it was a smaller section connected to the boiler at both the top and bottom via about 300mm of approx 1/4" or 3/8" copper .
There was a float valve in it that let mains pressue water in as the level dropped .
I believe the purpose of having the float chamber to the side was that the level in it was more stable and not so voilent due to the bubbling action in the boiler it self ....:. If that makes sense

[The Baker]

There are special water entry fittings for maintaining the water level of steam locomotives against the pressure of the steam.
No doubt there are likewise fittings (possibly the same) for filling commercial and other pressurised water heaters.
Dunno the details, ask someone in the industry.

Geoff

[shadylane]

Just a guess
The feed water will need to have a pressure higher than the boiler
And, preheating the feed water with recycled heat would be a good idea.

[steelmb]

If you want something that works like magic, then a steam injector is the ticket. Here is the Wikipedia version. https://en.wikipedia.org/wiki/Injector" onclick="window.open(this.href);return false;" rel="nofollow They work really neat when they work but they can be finicky. I have never seen one that worked at the low pressure that you are probably using. They may make them or they may not, I don't know. The ones I have used work at 120 psi down to maybe 40 or 50 psi. I have used a higher pressure one that worked from 175 psi down to maybe 100 psi. If you search YouTube you will find a couple animations how they work.

If you decide to try use an injector, the colder the feed water, the better it will work. Do not dump the overflow water discharge back into your feed water as this will heat up the feed water.

In my opinion the injector is pie in the sky for our kind of projects. I would use a pump that supplied a greater pressure than that in the boiler.

[Evil Wizard]

That steam injector is pretty smart. Using steam pressure to drive cold water into the boiler through what is roughly a venturi nozzle in order to increase the pressure.

I wonder if I could fab that.

Yummyrum, I suppose the small diameter of 1/4" or 3/8" over 30cm would prevent much push-back from the boiler into the float chamber. You think that float chamber was closed/pressurized?

[MichiganCornhusker]

Not sure if this idea will help in any way for your application, but still_stirrin helped me come up with this contraption that I use for my steam generator. The crossover tube is the key to keeping pressure equalized.
This is a very low pressure setup though, the still is open to atmosphere.

[Yummyrum]

Evil Wizard , it was pretty much exactly like MCH has shown except the element was vertical in a narrow tube and the float section was smaller .....and yeah the float chamber is sealed . I agree with your reasoning that the thin connection pipe reduces the surging in the float chamber . You would need to get a float valve that runs at high temp as I'm sure the water in the float chamber would be close to boiling temp .

IIRC this one used a float switch to operate a solenoid valve .

Thanks for the topic . I'm close to making a steam generator as I'm sick of boiling my keg dry ..... so all info that pops up is greatly appreciated

[Wild Bill]

Shady lane nailed it. With operation of steam boilers, a float controls a pump that is capable of developing more pressure than the boiler operating pressure. There will also be a check valve at the boiler feed water inlet, downstream of pump to keep boiler from back feeding when pump is off. Also the float balls in steam boilers are commonly made from copper.

[HDNB]

mine works like this:

water from mains to condensate tank, on a float to hold a level. >>>20psi pump>>>check valve>>>>check valve>>>boiler>>>valve to steam jacket>>>jacket>>>condensate trap>>>>condensate tank.

i have a water level switch on the boiler...when the boiler runs low, it supplies electricity to the pump until it reaches a full load again.

as a closed loop system, it all heats up as run progresses

the reason for two checks is in case one gets a bit of shit in it and sticks open...don't want to backfeed the system. in the event of back feed the condensate tank is open to atmosphere.

other considerations for the system is over/under fill sensors, flame rollout, over pressure, and (2x) remote shutdown and interlock on fire alarm, interlock on distillate output temp, interlock on coolant flow.