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[mrsgoggins]

Having returned from holiday I was catching up with my unread copies of "Model Engineer" when I spotted a letter from TAG commenting on previous articles by Martin Ransome.
TAG made the important point that although he had sold a number of boiler level control kits he had received little or no feed back. So I will try and start the ball rolling:

I purchased one of the original kits and it has been in use for a couple of years now in my 4" centre flue boiler.
The water pump is gear driven from a Borderer steam engine and the control system returns water to the on-board tank when the level is OK - via a servo operated valve.
The level probe is bronze and is connected to the negative side of the circuit.
I use tap water in the boiler and have had no problems with scaling or plating. Our water does not form scale in the kettle.
The only problems with reliability were of my own making as the water return system did not allow trapped air to escape and the pump would fail to prime when I refilled the tank.
The electronics have proved totally reliable and I have a second kit for use in my next project. I will put the monitoring LED's on fly leads rather than fit them to the control box.

I hope this info is of some use to both TAG and other steamheads looking for a safe ans simple way of controlling boiler water level.

Keith

[TAG]

mrsgoggins.
Thank you for your comments on my boiler water level control level system, your comments spur me on to re look at it again. The feedback is most useful. Let me give you some feedback on where my experiments have taken me so far. About the middle of last year I managed to talk an ex club member proficient in PIC programming to help me. In producing a programme usable for either the electrode (probe) or opto on gauge glass system ( Cheddar system) he got me back to square one.
I then made a conscious decision to concentrate on the optical system when I discovered an opto coupler made specifically for "looking" at liquid levels. After various bench experiments I came to the conclusion that the only true measurement was using an electrode within the boiler, which if you have not got a bush spare on the boiler but have a water gauge it is possible to fit an electrode.
One of the main problems with the optical system is bubbles in the gauge glass, I even had one test where a bubble remained stationary in the glass long enough to allow the pump to fill the boiler full! I now see why Stuart's have not re-marketed the Cheddar ABC system.
It is my intention to document all this testing and produce a further article for Model Engineer this year.
My conclusion is presently to concentrate on the electrode or probe system.

Tim

[kno3]

Tim,
There is a rather simple cure for bubbles in the water gauge glass that make a level reading impossible. Insert a piece of wire down the glass tube. This helps the bubbles rise and you get a correct reading. I have used this system in several boilers with satisfactory results.
I don't know how the opto-coupler works, but I can imagine a wire in the glass might interfere with it. What do you think?

[mogogear]

Tim,
There is a rather simple cure for bubbles in the water gauge glass that make a level reading impossible. Insert a piece of wire down the glass tube. This helps the bubbles rise and you get a correct reading. I have used this system in several boilers with satisfactory results.
I don't know how the opto-coupler works, but I can imagine a wire in the glass might interfere with it. What do you think?

Concur on copper wire-- rather heavy gauge works perfect - no bubbles since

[mrsgoggins]

Hi Tim,
Thanks for the update. Hopefully you will get some more user feed-back.

Keith

[TAG]

Thanks for the comments about putting a wire in the gauge glass to break up bubbles, I shall give it a try.
The opto coupler fitted to the gauge glass shines a infra red (IR) beam through the gauge glass onto a photo diode on the other side. As the refractive indecies of steam and water are different the amount of IR received at the photo doide is different whether it shines through steam or water, the trick is detecting this change.
Unfortunately I think the solid wire will always be "seen" as one condition only so no change in light will be received so the system fails, however I will give it a try.

I have always believed the simplist answer is the most sophisticated.

Tim

[HS93 (RIP)]

you may be able to use a piece of fiber optic wire

Peter

[ooyah/2]

If you have a blow down valve on the sight glass you shouldn't have a problem with bubbles.
Over the years I have built many boilers which all have had a blow down valve fitted and never experienced a bubble problem, this goes for small and large boilers.

I can't give a reason why not to put a piece of wire in the glass other than I just don't fancy it.

George.

[kno3]

The problem with blow down valves is that you have to reach in the model boat to manipulate them. Which means bringing the boat to shore etc. With the wire it's easier (if the water gauge is visible) - you can just bring the boat close enough to see if the water level is corect and then sail away.

That's why I fit a wire even to water gauges with blow down valves.

Tim, please let us know if the wire interferes with the optical sensor. As HS93 suggested, you could also try another material besidesn metal wire, if it withstands the temperature.

[south steyne]

Hi Guys after lots of experimenting with auto boiler control I have resigned to the fact that the water gauge glass method is not practical simply because there is too much activity in the boiler to give an accurate signal,however the principle of a signal to a electronic switch to a pump is sound and works well with a fine coated wire feeding through a machined boiler fitting with the underside over drilled and filled with liquid silicone the idea being the boiler pressure acting on the silicone seals the clearance between the wire and the fitting so the closer the fit the better also the wire is not exposed at the bottom of the wire but just nicked above this ensures the wire does not touch any stays or tubes .
I realize everyone has different theories but this works for me
Cheers
 

[ooyah/2]

The problem with blow down valves is that you have to reach in the model boat to manipulate them. Which means bringing the boat to shore etc. With the wire it's easier (if the water gauge is visible) - you can just bring the boat close enough to see if the water level is corect and then sail away.

That's why I fit a wire even to water gauges with blow down valves.

Tim, please let us know if the wire interferes with the optical sensor. As HS93 suggested, you could also try another material besidesn metal wire, if it withstands the temperature.

Calin,
It's a bit pointless fitting a blow down valve to the sight glass if you can't get to it !!!
Once you have your boiler up to working pressure and then blown down you shouldn't have bubbles in the glass when  the boat is out on the water.
. Here is a pic of the boiler in my tug, boiler is 4.5" dia and is fired by a plumbers blow lamp burner head.
Once it's up to pressure and blown down before setting sail the glass stays bubble free all afternoon, with the burner and large gas tank it can be on the water for 2 hrs( if I don't get bored before then.)
I don't have gas regulator or boiler level indicator I work between the gauge and the safety valve, which makes it more interesting keeping an eye on it rather than relying on the electronic devices.

However if you prefer the wire in the glass I don't see a problem and if it works for you that's great
George.

[dreadnought72]

I have always believed the simplist answer is the most sophisticated.

Tim, I know nothing about the technical intricacies of steam power.

But if it's water level in the boiler that needs to be monitored, my initial thought would be:

Weigh the boiler. A delve into reading about amateur robotics leads me to load cells, transducers that output a specific resistance which reflects a weight carried. Here's one that measures up to 10lbs for a not unreasonable sum. Connected to a microprocessor, you could have real-time boiler water mass information.

Andy, ponderin'

[oiler]

I bought the maxitrak low water sensor a couple of years ago. It uses a photo sensor on the sight glass as well. I have also used a probe system from Bill Ford here in the US. If I had a choice I would use Bill's because he has refined it over the years and it works very well.  Here is his link http://wldssystem.weebly.com/

The maxitrak's also burned out the optical sensor and I emailed them to get another but haven't heard back. I found the sensor from Mouser in Texas and they should arrive today.

The bubbles in the sight glass are a big problem and I have used the wire trick but the sensor senses the wire. I thought about gluing a wire to the back of the glass so the sensor won't see it but super glue is only good for 300 degrees F so I'm not sure this trick will work.

Also the Maxitrak does not have a relay for a pump or a timing circuit so I've had to make one for it. Without it the pump or solenoid will kick on and off any time the boat rocks back and forth.


The probe works best I have found but unless you build it yourself chances are your not going to find one that will fit the threads of your boiler because there is no standard.

As for as pumps go...

I've tried the Regner servo pump and built one myself. The Regner was slow would always fail to pump because the check valves would get clogged or not seal. The one I built would also fill too slow for my big V4 because the fastest servo only turns about 1RPM. Not only that but the servo pumps make noise that takes away from the steam engine. I built a pump using a gear dc motor that worked much better but was still loud. I'm now waiting on a very small dc water pump capable of 100 psi /600mlpm that is better quality, quieter and cheaper that either the servo models and geared motor design.

You can see some of what I've done on my youtube channel. http://www.youtube.com/watch?v=3zEArj_HwZ4
BTW I took the pump off of the engine because it was slowing it way down.

[TAG]

Thanks for everyone's responses some usefull ideas to follow up on. I already have an an auto blow down test rig ready but not yet tested.
Regards
Tim