Vacuum chiller ladder logic program
The PLC can explicitly write or read data that does not need to occur in real time. Based upon the common industrial protocol (CIA), the PLC is able to change data in the controller and get specific data returned in real time from the controller without having to write a single line of ladder logic. Several manufacturers of temperature controllers offer devices with communications, including Ethernet/IP or DeviceNet protocol, that allow the controller to communicate implicitly to the PLC. They offer communications so that they can easily exchange information with the PLC and share data. Some of the newer models of temperature controllers even look and feel like a small PLC. Many people use stand-alone temperature controllers to manage process temperatures and a PLC for machine control. This local display and control is why they continue to use stand-alone temperature controllers rather than a PLC. Any operator can initiate an autotune by simply pushing a button on the front of his controller. At the same time, all of the temperature controllers include a local display so the operators can see the temperature and setpoint. Additionally, all of the temperature controllers have an option to retransmit the process valve back to the DCS system using a 4 to 20 mA output. With this particular setup, all of the temperature controllers have options in them that allow users to send the temperature controller a setpoint remotely. In doing research, I have found a chemical processor who employs a distributed control system (DCS), but throughout the entire plant, temperature control is done with discrete temperature controllers. If it needs repair, the operator can send it in for repair and have it back in a few days. Once swapped out, the old controller can be taken to a bench and tested. One option is to simply swap out the old controller with a new one, which takes a few minutes. With a stand-alone temperature control, troubleshooting typically is easier.
#VACUUM CHILLER LADDER LOGIC PROGRAM SOFTWARE#
To troubleshoot a PLC and the PID parameters, special software is needed along with a computer, cables and training to access the PLC and start troubleshooting.
When things go wrong - as they tend to do in plants - the temperature control settings are a likely culprit that must be investigated. Anybody who has worked on PLCs for any length of time will attest that there are dangers in editing a PLC while it is running the machine.Įase of Troubleshooting.
As the new module is programmed for temperature control, changes are being made to a running process. If the PLC is to be set up for temperature control, it might be necessary to have an engineer or someone trained in the use of the specialized software configure the PLC.Īdditionally, configuring a PLC requires someone to go out in the plant, where the machine is running, and plug into the PLC. Generally, there is an engineer responsible for operating and programming the PLC. Using a PLC requires special software that can be expensive. By contrast, a stand-alone temperature control had all of those components and more for far less money.Įase of Use. Depending upon the PLC, you may need a thermocouple input card, a temperature control module and possibly a special output card. The PLC cards needed to perform temperature control are relatively expensive.