Beginner question

MBean0302

I'm just recently getting into steam. I have done a lot of work on hot water boilers and this is a pretty big transition lol. A lot bigger than I realized. I will assume everyone or most here have read the list art of steam heating so my question relates to a diagram on page 42 of the online pdf version, probably same page in actual book...

Steam travels from the boiler up to the header and then turns a 90 at a tee and heads out the main. Excess water continues straight and back to boiler. I understand the concept, but what makes the steam take that turn, and not just go straight back into the boiler?

Logic would say that a straight path is the one with the least restriction to flow, so i'm wondering what the science is behind it?

R Dougan

That loop is called an equalizer, ... the pressure from the boiler is "equal" at the riser to the header and at the below water line return connection. That pressure is greater than the pressure up the riser off the header. It moves from the volume of greater pressure to that of less pressure.

If you hooked two garden hoses from two separate spigots together with a Y shaped fitting and then attached another hose with a spray nozzle out the Y, ...the water doesn't go from one hose into the other and not out the nozzle when you squeeze it. The water will come out the nozzle at the same pressure as each of the spigots. Think of the header riser and the return connection as the two hose feeds and the riser off the header as the hose with the spray nozzle. … only difference, steam pressure vs. water pressure, ... same result.

That turn up the riser pipe is the only direction that steam can go.

Fred

Steam takes the path of least resistance, Hot goes to cold (or Cooler), High(er) pressure goes to low(er) pressure and the other end of that Tee, on the header goes to the Equalizer which drops down below the boiler water level so it is filled with water equal to the level of the water in the boiler and steam can't get back into the boiler.

MBean0302

> @R Dougan said:
> That loop is called an equalizer, ... the pressure from the boiler is "equal" at the riser to the header and at the below water line return connection. That pressure is greater than the pressure up the riser off the header. It moves from the volume of greater pressure to that of less pressure.
>
> If you hooked two garden hoses from two separate spigots together with a Y shaped fitting and then attached another hose with a spray nozzle out the Y, ...the water doesn't go from one hose into the other and not out the nozzle when you squeeze it. The water will come out the nozzle at the same pressure as each of the spigots. Think of the header riser and the return connection as the two hose feeds and the riser off the header as the hose with the spray nozzle. … only difference, steam pressure vs. water pressure, ... same result.
>
> That turn up the riser pipe is the only direction that steam can go.

Thanks! That makes perfect sense! The steam can't go back to the boiler bc the water in the wet return is like a wall in a sense?

Steamhead

Correct.

R Dougan

its not so much the water that prevents it, its the pressure pushing out in all directions at every opening of the boiler that stops it. If the boiler has two risers to the header, the pressure pushing out of each one would be equal to each other. The boiler is a pressure vessel and that pressure is equal at every penetration regardless if its above or below the water line. The radiators at the end of the pipe run are like the hose and nozzle in my analogy. The radiator vent acts like the nozzle itself, when open, ...steam can move. Once that valve shuts, steam movement toward the outside atmosphere stops.