what is meant by Process Control

Dear all

Really I am very happy to be a memeber of that great PLCs.net.

I had heared a lot of process control. I know well sequential control, but I do not know what is the difference between Process control and sequential control and patch control.

who guides me and help me in that even with small note, may i be a slave for him.

Mosh leldaragady ya darsh

The word process it self means production or manufacturing operation for example the line for producing Macaroni is a process, the rolling mill is a process ,controlling a heater or a burner is a process.In most cases in a process you have many parameter to control and to adjust may be this parameter are related to each other may be thier are induvidual as much as this number of parameters are increased and related to each other the more complicated process is founded.As a PLC programmer it's better to be aware of the process that you are going to work in this will make programming much easier.
SEquiential control
this is a group of movement or commands that is executed in a pre defined sequance setted by the programer in this case most propably you have no physical quantity to control .For example a conveyor movment could be sequantial control
good luck

Like so many definitions, this one gets a little blurry. Of course, as Hesham points out, everything from machining engine blocks to refining gasoline is a process, so in one sense evey automation project is process control. However, process control usually has a specific implication in the PLC world.

Historically the control world has been divided into two categories. The first, which gave birth to the PLC, is discrete product or parts manufacturing. The ultimate example of this is automotive assembly, where the manufacturing "process" is continuous but the end product is individual devices. PLCs displaced the original relay panels used to automate the sequential operations and provide equipment protection. These processes overwhelmingly use discrete I/O (in the early days called "digital" inputs and outputs).

The second category was "process industries". The ultimate example of this is petroleum refining. The process and the end product are both continuous. Here the original controls were predominantly single loop PID controls, later displaced by Distributed Control Systems (DCS), and recently by PLCs in many systems. In the process industries I/O is predominantly analog.

I think the two industry "sectors" are getting closer and closer. In my industry, cable manufacture, a few years ago we used no analogue values at all. Now, we use more and more with complicated mathematics as well. As the industries get more advanced, they get closer together, realising the potential they can gain from obtaining as much information about the process as possible. In many industries, information about the process is getting more and more essential as margins reduce and processes get tightened.