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Process Operation Technology

Oil, gas and petrochemical process industries

    EXAMPLES OF PROCESS CONTROL

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    Talib Al_Munawri
    Director-General
    Director-General

    Posts: 333
    Join date: 2009-07-03
    Age: 27
    Location: Sultanate of Oman

    EXAMPLES OF PROCESS CONTROL

    Post by Talib Al_Munawri on Thu Aug 12, 2010 9:05 pm




    We will give a simple example of process control.

    Manual Control




    Figure 1.1 Example of Manual Control


    The diagram above (see Figure 1.1) shows what is called MANUAL
    control. The process is temperature control. The indicator is
    a thermometer. The correcting unit is the gas control valve.
    The controller is the operator who uses his own judgement to
    keep the water temperature constant.

    Manual control has its uses as it is cheap to install and maintain,
    and simple to operate. However, it is very seldom used in industry
    because:

    The operator must remain in position at all times.
    It cannot be used if the operator is placed in a dangerous area.
    The process changes faster than the operator can react.
    A mistake by the operator can have dangerous results.

    These problems are avoided by using automatic control.
    Modern household appliances now use automatic control to make
    work easier.

    For example:-


    • Refrigerators and air conditioners use automatic temperature control.
    • Washing machines use automatic heating and water control.




    Automatic Control




    Figure 1.2 Simple Example of Automatic Control


    The above diagram (see Figure 1-2) shows a simple automatic
    controller. The boiler now has the loop closed and no operator
    is required.

    The following items are added.


    The temperature transmitter (T.T) which measures (senses) the temperature of the hot water and changes it to a standard signal.

    A signal line from the transmitter to the controller, the signal
    may be either pneumatic or electrical.

    A controller which keeps the temperature of the hot water at
    a position set by the operator (set point)

    The controller adjusts the correcting unit (automatic control valve) using an output signal line similar to the input line from the
    transmitter.

    The controller may provide alarm signals to alert the operator if
    the system fails. It may also shut off the gas if the water starts
    to boil.

    This is a very simple example of automatic control.

    Process Control Instruments can be very complex.

    If we take each part or device that is in a complex unit one by
    one the system is easy to understand.




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    marklgaines
    Member
    Member

    Posts: 1
    Join date: 2012-07-20
    Age: 56

    Re: EXAMPLES OF PROCESS CONTROL

    Post by marklgaines on Fri Jul 20, 2012 10:27 pm

    I'm looking for images of a process trend screen. Sucsh as a distillation tower and it's control loops. Like to see PV trend lines for pressure, temperature and level along with SP, CV output.

    rrafeeksl
    Member
    Member

    Posts: 1
    Join date: 2012-08-09
    Age: 39

    Re: EXAMPLES OF PROCESS CONTROL

    Post by rrafeeksl on Thu Aug 09, 2012 1:20 am

    Dear is very good for begineers like me, thanks indeed for the good job
    Rifkhan

      Current date/time is Thu Nov 27, 2014 8:17 am