Automated Control System for Water-Chemistry Conditions in Water-Steam Circuit of Energy Units (ACS WCC)
Our Company offers complex one-way solutions for the automatic chemical control requests – from development of project documentation to commissioning of the whole system. We design and manufacture basic system components, including equipment and controllers for sample preparation in TPU (Test Preparation Unit) «TEST»; sensors and instruments for measurement of basic heat medium parameters; proprietary software for development of network for data acquisition encompassing all system components, followed by such data archiving and visualization.
1. Functions and tasks of ACS WCC
The ACS WCC is intended to ensure:
Automatic selection of heat medium samples at all stages of technological process;
Automatic rendition of physical and chemical parameters of samples in compliance with requirements of automatic chemical control instruments;
Supply of necessary amount of sample to sensors of automatic chemical control instruments;
Automatic measurement of scheduled parameters for water-chemistry conditions of energy unit;
Digital conversion of measured parameters, followed by indication and registration on electronic and paper mediums;
Signaling of parameter deviation beyond stipulated values;
Recording of <history> for water-chemistry conditions parameters over necessary period; generation of related reports and graphs; Visualization of state of all monitored parameters and emergency indication in mnemonic diagrams displayed on monitors of automated workstations (AWS) for attention of attendance personnel and management of station.
2. ACS WCC architecture and design
As the lowest link in the system ensuring measurement of all WCC parameters are used the Sample Preparation Units “TEST” (SPU "TEST"), which are connected to measurement instruments.
The WCC parameters can be measured with use of the following instruments:
The system may equally incorporate other types of units, however, under prior coordination with Customer.
The SPU "TEST" reduces the pressure and temperature of sample and distributes it into 5 channels (4 for automatic selection, and 1 for manual selection). The settings provide for indication of sample temperature and pressure excess above acceptable values. From output of the SPU "TEST" is supplied to chemical analysis units (1 to 4). The manual selection channel can be used to connect the fifth unit.
Primary processing of data received from ACC (automatic chemical control) units is realized in the electronic control unit of the SPU "TEST"; this control unit is employed to -receive analog and discrete signals, -convert these signals into the digital form, -and, -data transfer via RS-485 interface to the PC (server) of the ACS WCC.
Electrohydraulic diagram for SPU "TEST" connection to automatic chemical control units (per one sample selection point)
The SPU "TEST" control unit features the following output signals:
- Digital signal (via RS-485 interface), employed for transfer of the following data:
- Sample temperature (from inbuilt temperature sensor);
- Sample consumption (from inbuilt consumption sensor);
- Sample pressure excess above acceptable level;
- Information from ACC units (up to 4 units).
- Current signal, 4 - 20 mA (1 output);
- Discrete signals (excess of measured parameters, temperature and pressure above acceptable levels, 6 thresholds).
The SPU "TEST" control unit features the following input signals:
- Digital signal (via RS-485 interface);
- Current signal, 4 - 20 mA (4 inputs);
- Discrete signal (sample pressure excess above acceptable level, 2 thresholds).
The software of the data acquisition and processing system of the ACS WCC (ACS WCC SW) is an application running under the Windows OS.
The ACS WCC SW ensures the following functions:
Reading of technological process parameters of energy units from ACC units;
Preprocessing of data received from ACC units (if necessary);
Display of technological process current parameters on PC monitor;
Operator setting of necessary emergency limits for each controlled parameter;
Tracking of parameter deviation beyond acceptable values supported by emission of caution signals and logging of emergency events;
Parameter value archiving;
Viewing of archive information per certain periods;
Generation of reports based on archive contents;
Transfer of on-line and statistical information to remote workstations via embedded Web server.
The ACS WCC SW is realized as an automated workstation (AWS) on the basis of an industrial computer, which is located in the operator room at the distance of up to 1200 m off data acquisition controllers (the SPU "TEST" control unit). The communication between the PC and data acquisition controllers is realized via the RS-485 interface.
Structural diagram of ACS WCC for water-steam circuit of power plant
The graphical interface of the ACS WCC SW is intended to display the state of technology and technological equipment as a dynamic review diagram, supported by presentation of basic data relating to the real-time course of technological process. On operator demand, the console may present more detailed on-line, archive or statistical data on state of separate sections of the technological process (represented as diagrams and trends).
The ACS WCC SW requires presence of a Web server to ensure presentation of on-line and statistical data to remote workstations. The workstation can be any PC connected to the server via the TCP/IP network and equipped with a Web browser. The Web server presents information in the "read-only" mode, as dynamically updated HTML pages.
The ACS WCC SW must provide for the possibility of further integration of an OPC server for data presentation to OPC clients of third-party developers.
3. Visualization of data dialogue
The ACS WCC SW ensures indication of controlled parameters as a multi-level diagram. Each level is represented as a diagram of the whole system, or, a section of the system, with indication of current state of controlled parameters.
The current state of controlled parameters is indicated in digital form in the appropriate section of the diagram.
Apart from the direct presentation of values, the indication of state of controlled parameters is supported by color signaling. If a value is within the acceptable limits, that value is indicated in green. If a value exceeds the cautionary or emergency limits, the color switches to yellow or red respectively. The ACS WCC SW provides for controlling of up to three levels of emergency limits.
In case of no data per any of the channels, no parameter value is indicated.
The figure below gives an exemplary indication of one of the energy units of a thermal power station.
Color signaling is also reserved for indication of the SPU state. Grey color of the SPU icon indicates normal state of all SPU “TEST” parameters. Yellow color indicates deviation of temperature or consumption value beyond the cautionary limit.
Red color is intended to indicate that the temperature, consumption or pressure value exceeds the emergency limit, or that any other emergency situation has occurred.
All emergency situations, as well as the facts of their termination, are registered in the Emergency Situations Table, which is part of the graphical interface. Moreover, information on emergency situations is saved to the archive on HDD.
A more detailed presentation of the state of any particular SPU can be obtained by selecting that SPU in the diagram. In this case, the SPU shall be presented as a separate diagram, such as the one presented in the figure below.
The history of parameter change per one of the selection points, as well as the information on current emergency limits, can be viewed as a dynamically updated graph (trend), by prior selecting the necessary point in the general diagram.
The trend allows both viewing of the current state of one or several controlled values, and selection of data sample per any particular period from the archive.
The operator is enabled to view and, if necessary, change the values of tracked emergency limits for controlled values.
Apart from on-screen presentation of on-line and archive data, the system also provides for generation of reports as text documents.
Such reports may contain graphs for value change over set time periods; maximum, average and minimal values; and, information relating to possible occurrence of emergency situations.