Would you explain how the PLC can be used to ensure plant safety , particularly in conjunction with master / zone control .

 

What do you mean by plant safety?
What is you imagination telling it can do?
What would you like it to do?

You can connect motion detectors, proximity detectors, video cameras with digiatl outputs, intrusion alarms or any number of other devices related to safety and preventing unauthorized entrance to areas or equipment to a PLC. you can connect light barrier/curtains to them, connect flashing lights and horns to the outputs, you can operate mag locks for doors via a card reader which sends a digital output to a PLC or even card data. The door is wide open, it is up to your imagination - it can be simple or complex.

Need some technical asssitance or consulting input?

matt
[email protected]

 

You can install external safety relays that will interrupt the feed to the PLC outputs. Omron have an IEC type 4 compliant safety relay that mounts on the rack of the CS1 PLC. This relay can only be read in the PLC but the external control on the card is fully type 4 compliant. There are an extra 4 inputs that can be used as normal inputs. There is also a separate 24VDC power supply to the card to maintain it's integrity.

 

hi

It totally depends upon you that how you want to imply plant safety. For eamaxple In an Edible Oil Automation Project; the Plant saftey is observed as follows.

1) Every high level, high temperature, high pressure etc signal is reported by PLC.

2) Upon Some Critical signals PLC not only report them but also trigger a Alram Hooter to attract the attention of every body on plant to take proper steps accordingly.

3) And upon Some very Dangeraous Signals as Very High Pressures in Filters, or Very high temperature in Bleaching Container; PLC not only generates alarm hooter but also automatic Shut Down the related portion of the plant; So as to observe the full safety precautions.

For further information Do contact at

Syed Aftab Ahmed
Siemens
Lahore
Pakistan
[email protected]

 

go to this site and it explains with products

www.am.pepperl-fuchs.com and it tell about asi safety at work.

Can a PLC or PC read the state of the Safety Inputs?
Yes. As soon as a Safety Module indicates that safety input has been activated it stops transmitting its dynamic bit pattern. The PLC/PC can simply monitor the data from the Safety Module, checking for the “0000” bit pattern. All other bit patterns can be neglected as they are part of the dynamic data cycle and indicate normal operation. This eliminates the costly and time-consuming process of wiring auxiliary contacts for monitoring the status of safety devices to the PLC.

 

This depends on what you mean by safety. In a plant environment, safety is usually considered to be Plant personnel going home at night, the bugs and bushes in and around the plant, and the equipment in the plant. If it is a particularly hazardous process, redundancy of controllers, and sensors, is number one. Sometimes a seperate control systems which exists outside of the usual controllers arena is another option, two systems one for everday control, another for emergency shutdowns, although a properly programmed plc with a good back-up power system and the proper forsight into the failed state of your end devices is essential if you are using a plc. A PLC is only the controller! safety is so much more, than just how does the plc perform. It must be consideed from the device and process through to the operators mind.