Steam Boilers staging On/Off based on modulation rate
Steam Boilers staging On/Off based on modulation rate
(OP)
Hi
I am currently commissioning a PLC controlling the staging on and off of 3 nr. Steam boilers based on the modulation rate of the boilers. All boilers are different sizes. Staging them on is no problem. When the running boilers are at more than 90% modulation for 3 minutes another boiler is added .This works fine.
The problem is how do I get the PLC to decide to switch the last boiler off again. Again I'm going to look at the burner modulation rate. Is there a correlation between steam capacity from the boiler and the boiler burner modulation rate? E.g. can you say a 10 ton boiler at 50% modulation is giving 5 tons, at 30% gives you 3 ton etc..? If so I can write a simple algorithm to do the job. Does anyone know where I can find a curve of burner modulation V's Boiler output for a typical steam boiler gas fired?
Regards
Remp
I am currently commissioning a PLC controlling the staging on and off of 3 nr. Steam boilers based on the modulation rate of the boilers. All boilers are different sizes. Staging them on is no problem. When the running boilers are at more than 90% modulation for 3 minutes another boiler is added .This works fine.
The problem is how do I get the PLC to decide to switch the last boiler off again. Again I'm going to look at the burner modulation rate. Is there a correlation between steam capacity from the boiler and the boiler burner modulation rate? E.g. can you say a 10 ton boiler at 50% modulation is giving 5 tons, at 30% gives you 3 ton etc..? If so I can write a simple algorithm to do the job. Does anyone know where I can find a curve of burner modulation V's Boiler output for a typical steam boiler gas fired?
Regards
Remp





RE: Steam Boilers staging On/Off based on modulation rate
Do you have a meter on your existing fuel gas supply to each boiler and steam meters? You could use that data to supply what you are looking for (assuming you trust them). Alternatively, do the manuals or documentation for these boilers have any information on what you are looking for?
RE: Steam Boilers staging On/Off based on modulation rate
What modulates the firing demand signal? If it is header pressure, then that ought to tell you when you have too much steam production capacity on line.
rmw