Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hey folks, been a while since I’ve posted.  Had a fun project I worked on today… added my own “Blowdown” system to my Stuart plant which uses a Jensen 75 windowed boiler.   Thought of this idea Sunday evening and got all the measurements required to make this work.   Using a reducing bushing from PMR, I soldered a copper tube to the end hole which is measured to length allowing a small 1mm gap at the bottom of the boiler between the copper tube and the boiler.  From here, it is seated into the boilers safety valve holes, as is my steam pipe.  As per the photos you can see how it works in better detail.

Steam pressure will siphon water up the tube and through the pipework and out as a typical blowdown valve would work.   Tested this out in its entirety and it works flawlessly. 

Operation would be when the water level is low, shut down the engine as usual, let some pressure build to about 25psi, and cut the gas. Open the blowdown valve and most of all the water evacuates, which will be demonstrated in the video below.

As per the photos you’ll see no safety valve.  I am a certified idiot, so please don’t try this at home… none the less, with adequate monitoring of pressure and utilizing a gas cutoff valve, this can be safely performed, but you must be engaged with the engine during its entire run.     If pressure ever got to high, I’d simply cutoff the gas and evacuate pressure.   Engine runs and boiler holds pressure between 15-20psi so this isn’t an issue for me.

The video also explains how water is added to the boiler.

Let me know your thoughts.   Enjoy the video.
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https://www.youtube.com/watch?v=l7_wpvJIho0

Interesting Travis!

A blowdown valve is for removing sediment from dirty water (which is why it’s located low) and done in a short burst, not likely going to be achieved with this setup

I agree with draining boilers warm to help with evaporation, but if done too hot the sediment/scale can be baked to the inside.

I actually found some particles of sand like material on my last blowdown, but it wasn’t much.     I find this just to be a fun little project, and it does allow me to evacuate most of the water from the boiler instead of dumping it out or trying to suck it out.   And it adds more pipes to the plant which to me is just aesthetically pleasing.   LOL! 

It’s more of an aesthetic and adds another element to the steam plant.     

Just a thought ... since you asked.

How about putting a "T" fitting at the top of your steam line, to mount your pressure gauge, so that you can put your safety valve back on the boiler.

Another thought, with sooooooooo much steam line exposed in those long runs of pipe, some form of insulation covering them would likely be a good idea.

Someone mentioned this.   Put a Tee fitting 1/4-40, and then @ the top put a SV.  And on the back end, a plug.   It would certainly work. The only 1/4-40 SV I’ve found is the UK, and shipping international is a nightmare!

My thought was to use the T-fitting on top of the steam line for your pressure gauge, so you could put your original Jensen safety valve back in place on the boiler.

The pressure guage is a #12-32 for banjo screw.  The hole is a 12-32 female.  I’m not sure there are any fittings for that.

It was designed to go on top of the steam line coming from the banjo screw, thus why I have a teflon bushing there.

Where there is a will, there is a way!

I’m no machinist but that 12-32 hole could be drilled out and threaded to 5/16-24, for a safety valve?

Might you consider switching the gauge with one of the pressure gauges offered by PMR, that has threads that are adaptable to the pipe and fittings you are already using?

I may eventually entirely go with a different boiler. The Jensen boiler wasn’t designed for PM pipe work, which is what makes my plant unique,  but no matter what I do with the 2 (5/16-24) holes, I still have a #12-32 hole where the current guage is at. All I can find for that type of fitting is screws. 

My absolute best bet at the current configuration is to get a Tee fitting and put it the first elbow on the steam line, and put a 1/4-40 SV on the top, and put a 1/4-40 plug on the rear.

I just can’t find any good 1/4-40 SV’s, except ones that are way over priced on eBay.     

If I was a machinist I could make my own stuff.

Then perhaps you would want to be looking into something like this, which would be a perfect match for your S-50.

https://www.ebay.com/itm/116197059149?

Hmph!  Well, I have some options here.  The Jensen boiler is awesome but it’s a bit small.

If I upgraded to a Stuart boiler and added some cladding to the pipework, it may be awesome. 

Thanks for the insight, will keep you posted what I do.