One way I found to maintain temps, pressure and even steam volume is to use a function of (x-y)/x x is the max value you want, y is the input from whatever you want to control. So to control pressure, you could use a constant number of 7 for boiler pressure conneected to x on the function block, connect a variable valve to the fluid from firebox to boiler, then connect output of the function to the valve and the boiler pressure node to y of the function block. It makes the valve open in the inverse percentage of the difference. If that is even a thing. The easiest way I have found to manage pressure is to limit the water in the boiler. The boiler has enough water to create about 7000bar of pressure ( exaggerated numbers, haven't done the actual calculations). 1L of water into a hot boiler will create about 3bar pressure if I remember right. So if you use the function i mentioned above with 3L as the setpoint (x) and use the fill volume of the boiler as the variable(y) and connect a tank and variable valve to the water in side of the boiler that has 0% fluid in it, you do not really have to worry about the temperature of the boiler being too high. In fact, higher boiler temp is better because it creates steam faster. 🤷♂️ something to try out maybe.
I've tried something similar to your setup, but I used PIDs to do the heavy lifting and control boiler and furnace temps, using 0.1 = P = D and then i = 0. I then used a less-than function to control a numerical switch and another one to control another numeric switch to vary the PID setpoints based on pressure. The furnace is set to a constant 250 degrees to lessen coal consumption. If the boiler pressure is below x, the temps are set to a; if the pressure is between x and y, temp is set to b; I think the third one was for testing purposes. Anyway, mine works, but it isn't meant to maintain one pressure. It's meant to maintain a range of pressure for occasional use (steam whistle). I'll try your method next. That's a good idea about the boiler water level. I've been leaving it full and having my water tanks to constantly fill it
@@qazxsw21000 I actually came up with a better way. I posted it to the workshop. It controls the water into the boiler to keep pressure as close to 10 as possible without going over.
Just keep it simple. The best logic for controlling a boiler is 2 threshold gates and two and gates. I use two and gates because I want the final on/off output to factor in the on off signal from my key button that starts my system. But basically, the two threshold gates on/off output goes to the inputs of one and gate. the output from the first and gate goes into an input on the second and gate. then your on/off switch into the second input of the second and gate. The final output of the and gates will go to the two standard 3x1x1 pumps you have cycling coolant through your boiler from your heat source of choice. The two threshold gates will measure boiler pressure(High of 7 low of 0) and boiler temperature(High of 105 low of 0). The whole setup then can be a closed loop between boiler fully filled with water, pistons or turbine, and condenser with pumps between and no need for valves and water tanks.
One way I found to maintain temps, pressure and even steam volume is to use a function of (x-y)/x
x is the max value you want, y is the input from whatever you want to control.
So to control pressure, you could use a constant number of 7 for boiler pressure conneected to x on the function block, connect a variable valve to the fluid from firebox to boiler, then connect output of the function to the valve and the boiler pressure node to y of the function block. It makes the valve open in the inverse percentage of the difference. If that is even a thing.
The easiest way I have found to manage pressure is to limit the water in the boiler. The boiler has enough water to create about 7000bar of pressure ( exaggerated numbers, haven't done the actual calculations). 1L of water into a hot boiler will create about 3bar pressure if I remember right. So if you use the function i mentioned above with 3L as the setpoint (x) and use the fill volume of the boiler as the variable(y) and connect a tank and variable valve to the water in side of the boiler that has 0% fluid in it, you do not really have to worry about the temperature of the boiler being too high. In fact, higher boiler temp is better because it creates steam faster.
🤷♂️ something to try out maybe.
I've tried something similar to your setup, but I used PIDs to do the heavy lifting and control boiler and furnace temps, using 0.1 = P = D and then i = 0. I then used a less-than function to control a numerical switch and another one to control another numeric switch to vary the PID setpoints based on pressure. The furnace is set to a constant 250 degrees to lessen coal consumption. If the boiler pressure is below x, the temps are set to a; if the pressure is between x and y, temp is set to b; I think the third one was for testing purposes.
Anyway, mine works, but it isn't meant to maintain one pressure. It's meant to maintain a range of pressure for occasional use (steam whistle). I'll try your method next. That's a good idea about the boiler water level. I've been leaving it full and having my water tanks to constantly fill it
@@qazxsw21000 I actually came up with a better way. I posted it to the workshop. It controls the water into the boiler to keep pressure as close to 10 as possible without going over.
@@Bendigo1 what’s the name of the creation? I’ll take a look at it when I get home
@@qazxsw21000 Steam Boiler Pressure Controller by Bendigo
Just keep it simple. The best logic for controlling a boiler is 2 threshold gates and two and gates. I use two and gates because I want the final on/off output to factor in the on off signal from my key button that starts my system. But basically, the two threshold gates on/off output goes to the inputs of one and gate. the output from the first and gate goes into an input on the second and gate. then your on/off switch into the second input of the second and gate. The final output of the and gates will go to the two standard 3x1x1 pumps you have cycling coolant through your boiler from your heat source of choice. The two threshold gates will measure boiler pressure(High of 7 low of 0) and boiler temperature(High of 105 low of 0). The whole setup then can be a closed loop between boiler fully filled with water, pistons or turbine, and condenser with pumps between and no need for valves and water tanks.