Scada control system

For water-treatment-plant

Posted by george vakfaris on August 24, 2017

The application programs a SCADA Control System for ESCARCOM S.A. water treatment plant (WTP) in order to:

  • monitor
  • Telecontrol and
  • real time data logging of operation parameters

The WTP layout includes a 140m3/hr inlet, a grit removal for large particles, a DAF unit (*Dissolved Air Flotation), Primary & Secondary aeration tanks, Primary & Secondary clarifiers and the outlet. A filter press is also installed for sludge dehydration and removal.

Water-treatment-plant top view layout.

The incoming load consists of fruits processing (apricots, cherries and peaches).

The Siemens S7-1200/1214C CPU was selected because of:

  • the CPU size
  • the number of integrated I/O and Ethernet port
  • The User Defined Pages (UDP) option
  • the expansion modules
  • the communication protocols (HMI, Peer-to-peer, Modbus to Ethernet)
  • The programming software TIA PORTAL, which allows the user to integrate all instructions and devices within a unified IDE

Design

  • 30 Digital Inputs (DI) for switches/breakers status (in/out/trip)
  • 4 Analog Inputs (AI) for values monitoring/logging (flowmeters, Oxygen blowers etc)
  • 4 Digital Outputs (DQ) for DAF remote control
  • 2 Analog Outputs (AQ) for air blowers regulation
  • Wireless Telecontrol through PC/Cell phone
  • Data logging into *.csv files for processing in MS Excel

Additional modules are easy to install and program for expansion capabilities

Automation Panel. Equipped with MCB, RCD 30mA and SPD T2 protection devices as well.

Operation

The end user can do the following operations through the Webpage created:

  • monitoring wtp operation in real time
  • logging values from oxygen blowers, flow meters, energy meters and power factor
  • Start/Stop DAF unit remotely and/or by-pass it in case of low input. This function is available only for password verified users
  • Webpage

    The S7-1200 PLC series allows the programmers to create user defined pages.

    It was created in BOOTSTRAP 4 in order to allow the remote user to implement the SCADA graphical environment.

    TIA PORTAL allows the programmer to use its variables by adding a 'physical' name to them and inserting to the HTML code. The communication was created with AJAX/JSON and the page design in HTML, CSS and jQuery v3.2.1.

    What is also interesting on the communication between the PLC and the remote server is the GSM Modem. Data refreshing is done in 30seconds intervals. It is not the entire webpage to be refreshed because it would require a large amount of transmitted data and time delay to do so. Only those with status change are refreshed. This can be achieved either by entering every unit into separate < iframe > or with the following script:

    < script type="text/javascript">
    setInterval("update(imgName)",30000);
    function update(imgName) { image = document.getElementById('comp1');
    image.src = imgName;
    }
    < / script >

    variables reading from the CPU

    < img src="icons/compressor_:="AIRCOMP10I": _:="AIRCOMP1TRIP":.svg" id="comp1"/>

    variables writing to the CPU

    < !-- AWP_In_Variable Name='DAFINOUT'-→
    < form method='post' action=' '> < input type='image' alt='submit' src='icons/confirm.svg'> < input type='hidden' name='DAFINOUT' size='20px' value='1'> < / form >

    User Defined Webpage. SCADA Interface in web browser.

    The end user watch in real time the operation of the equipments through their various coloring. GREEN (ON), GREY (OFF), RED (ERROR). He can also start/stop the DAF unit with the up left two buttons. This operation requires password insertion. By clicking on the values shown he can download them to the PC for further processing.

    SCADA Interface on mobile phone (Responsive).

    In case of emergency an SMS is sent to the preselected mobile phone number. In the wtp was chosen the operation manager.

    Text and images by george vakfaris.