Pressure gauges - air gauges ok?

[Thad Swarfburn III]

Is it possible to use an air gauge to measure steam as long as a siphon tube is used?

If not, where do folks get their steam gauges?

 

[Noitoen]

The siphon is to prevent hot steam from reaching the gauge. As long as you keep those "cheap" plastic gauges away from the heat you can connect it to steam.

 

[GWRdriver]

The siphon is to prevent hot steam from reaching the gauge. As long as you keep those "cheap" plastic gauges away from the heat you can connect it to steam.

The siphon acts as a condenser to change steam into water so that WATER rather than steam is presented to the Bourdon tube. If you are going to use a gauge made for something other than steam use a gauge made for water.

 

[hammers-n-nails]

dont know what part of the world your in but the local plumbing supply store (not lowes/home depot,etc.) here can get whatever kind of pressure guage you want.

 

[shred]

I've used the Home Depot pressure gauges to measure steam pressure and hydro-test pressure to no ill effect with a loop in the tube.

 

[terrywerm]

As one gentleman already pointed out, as long as you keep the plastic away from the heat, even the cheap plastic gauges will work for steam. Internally, pressure gauges are all pretty much the same, with minor differences from one manufacturer to the next, and of course better components in the more expensive models. The gauges used in full size practice are not really specified as "steam gauges" either, and siphons are used in full size practice all the time. ASME boiler code in the USA also requires some sort of siphon or piping arrangement so that water is always acting directly on the Bourdon tube inside the gauge, not steam, regardless of the gauge that is used.

 

[woodnut]

I have a quick question.

I am making whats call a "hardware Store Stream Boiler" as all the parts can be bought from your local hardware store. Its basically a 2" x 6" black pipe nipple and 2 end caps (Popular Mechanics 1963). Holes are drilled and tapped in the top for the steam outlet, safety valve and filler hole. 2: 1/4" flare fittings and a 1/4" coiled copper tube is run under the boiler on a slight angle, this were you heat the water.

Now to my question. How long should the the pipe to the pressure gauge be and what size of pipe to use? I have a 0 to 200lb gauge with 1/8 threads on the back.

I plan to keep the working pressure between 20lbs and 25lbs and have the safety valve set for 80lbs. I am using the same pipe used in fire sprinkler systems in commercial buildings which is pressurized to a working pressure of 125lbs. I will still do a pressure test to 120+lbs to make sure there are no leaks.

I don't have a lathe or mill as of yet to build a better boiler, thought I start small and simple first. Then I will have to build a engine to run of the boiler.

John