maintpro
Member
I have a wax melting process wich utilizes a steam heated system controlled by a TI 545 PLC. My steam valves operate at 0 - 20 psi.
I use a Cutler Hammer PanelMate 1500 to make adjustment to and monitor my kettle temperatures.
The system operates so that the steam valve for each kettle is open proportional to the wax temperature.
I know that when my kettle temperature is low (80 deg f.) and my setpoint is high (250 deg f.) that my valve is open 100% with 20 psi and the outputs are at 20ma. The valves will start to close as the temperature in the kettle climbs to 250 degrees and the PLC outputs decrease as well. If the kettle goes overtemp (by 20 deg f or more), the valves will go into a "lockdown mode" and the PLC outputs will be at 4ma and the air pressure on the steam valve will be at 0psi.
My question is,why is it that when the Kettle temp is the same as the preset temp, the PLC output will be at 7ma and the air pressure on the steam valve is at 9psi. Is this to maintain heating and help hold temperature or is the system malfuctioning. I have been having a lot of trouble with the kettles overheating and have yet to find an answer to the problem.
I use a Cutler Hammer PanelMate 1500 to make adjustment to and monitor my kettle temperatures.
The system operates so that the steam valve for each kettle is open proportional to the wax temperature.
I know that when my kettle temperature is low (80 deg f.) and my setpoint is high (250 deg f.) that my valve is open 100% with 20 psi and the outputs are at 20ma. The valves will start to close as the temperature in the kettle climbs to 250 degrees and the PLC outputs decrease as well. If the kettle goes overtemp (by 20 deg f or more), the valves will go into a "lockdown mode" and the PLC outputs will be at 4ma and the air pressure on the steam valve will be at 0psi.
My question is,why is it that when the Kettle temp is the same as the preset temp, the PLC output will be at 7ma and the air pressure on the steam valve is at 9psi. Is this to maintain heating and help hold temperature or is the system malfuctioning. I have been having a lot of trouble with the kettles overheating and have yet to find an answer to the problem.