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Process control systems

Johno12345
Hi,


I'm looking at some plant in the facility where I work, which uses a significant amount of energy. Some of it needs replacing because its worn out and I think its a good opportunity to look at the process and potentially upgrade the controls with a view to saving energy. 


I spoke to our energy advisor, which didn't give me a great amount of confidence.


It basically consists of systems that cool a liquid (cooling towers), move the product hydraulically, and stir the liquid. In total, there are 15 motors up to about 25kW and it all runs star-delta, manually controlled, part has a thermostat but that brings on the whole plant where only a small part could be on. 


I think a lot could be run with inverters, based on the process temperature and outside temperature, along with other inputs.


This is where it gets beyond me, I can describe how I want it to operate, and what I want to achieve, but all the people I speak to seem to fail to grasp the system as a whole, and can only focus on a tiny part, like 2 or 3 motors or pumps.


I'm obviously looking for a specialist but don't know what they would be called, or where to look. Does anyone know where or who i could speak to? 


Thanks
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    Johno12345:


    I'm obviously looking for a specialist but don't know what they would be called, or where to look. Does anyone know where or who i could speak to? 


    Thanks


    I think hat the process design should be led by a Process Engineer who would produce optional Process Flow Diagrams to optimise the system. The selected process would then be illustrated on Piping & Instrument Diagrams (P&IDs) which would describe the required control scheme. At this point the actual control scheme detail design can be started.
    As an “electrical person” I have only got involved in the control system design/commissioning when the P&IDs had been drafted but a few points for your consideration of energy saving are;-
    I agree with others that VSD inverters do not always provide the best solution. They lower the drive full load efficiency and are sometimes used as a means of compensating for an oversized pump/fan selection.
    The selection of the more efficient mechanical equipment is followed by the selection of a potentially smaller and more efficient electrical drive.
    The use of storage vessels can create a means of avoiding the need for continuous circulation/pumping.
    Frequent starting & stopping is usually avoided in continuous process systems to minimise wear but there are ways of soft starting to minimise wear and cut down on machines running on recirculation for extended periods.
    At the end of the proving the functional control/sequencing the Process Engineer/Technicians may optimise the instrument settings to achieve the correct product without over heating or cooling, optimum periods of pumping or agitation etc.

    I’m sure that a Process Engineer would think of a lot more energy saving techniques and, with his Mechanical colleagues,  have the background to provide the financial implications of the alternatives considered.
    Regards

     


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  • 0
    Johno12345:


    I'm obviously looking for a specialist but don't know what they would be called, or where to look. Does anyone know where or who i could speak to? 


    Thanks


    I think hat the process design should be led by a Process Engineer who would produce optional Process Flow Diagrams to optimise the system. The selected process would then be illustrated on Piping & Instrument Diagrams (P&IDs) which would describe the required control scheme. At this point the actual control scheme detail design can be started.
    As an “electrical person” I have only got involved in the control system design/commissioning when the P&IDs had been drafted but a few points for your consideration of energy saving are;-
    I agree with others that VSD inverters do not always provide the best solution. They lower the drive full load efficiency and are sometimes used as a means of compensating for an oversized pump/fan selection.
    The selection of the more efficient mechanical equipment is followed by the selection of a potentially smaller and more efficient electrical drive.
    The use of storage vessels can create a means of avoiding the need for continuous circulation/pumping.
    Frequent starting & stopping is usually avoided in continuous process systems to minimise wear but there are ways of soft starting to minimise wear and cut down on machines running on recirculation for extended periods.
    At the end of the proving the functional control/sequencing the Process Engineer/Technicians may optimise the instrument settings to achieve the correct product without over heating or cooling, optimum periods of pumping or agitation etc.

    I’m sure that a Process Engineer would think of a lot more energy saving techniques and, with his Mechanical colleagues,  have the background to provide the financial implications of the alternatives considered.
    Regards

     


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