Automated Process Control System (APCS) of a Gas Distribution Station (GDS)

Application

Automated Process Control Systems (APCS) carry out a continuous automatic monitoring of process parameters, the implementation of protection functions, remote and automatic control of the main and auxiliary equipment of GDS, that provides gas supply to consumers in the required quantity according to the specified parameters.

APCS of GDS is designed for operation as a part of an integrated automated process control system of a gas transportation enterprise with interaction with a control center via communication channels of a linear telemechanics system or an industrial computer network.

Functions of APCS of GDS

Informative functions:

• automatic data accumulation and recording from process parameter sensors;
• automatic collection and processing of information on operating modes, the status of main and auxiliary equipment and the position of isolation valves, including:
  • isolation valves of switching and reducing units;
  • gas heaters;
  • fire detection and gas contamination control systems;
  • heating, ventilation and security alarm systems.
• formation of pre-emergency and emergency alarm, alarm on unauthorized changes in the process equipment state, deviation of parameters beyond the limits of process setting;
• display of information and signals on abnormal situations on the control panel (operator’s panel) of the automation cabinet or on the display screen of the GDS operator's workstation;
• gas flow measurement with data accumulation on hourly, daily, monthly and annual gas flow rate for GDS consumers;
• integration with flow computers;
• information exchange with remote and/or local operators’ workstations via interface communication channels;
• recording and archiving of information on the GDS state, emergency messages, operators’ actions during station control with data safety within at least 30 days at the operator's workstation, maintenance of the emergency archive on the controller equipment;

Control functions:

• automatic implementation of control algorithms of actuating units;
• remote control of isolation valves and other process equipment from the control panel and (or) from the operator's workstation in accordance with the GDS work procedure;
• automatic protection control such as: automatic access to backup reduction lines if there is any problem with one of the main reduction pipes and fuel shut-down control of the reduction lines defective reducing threads;
• automatic activation of emergency exhaust ventilation in case of gas contamination of the compartments.

The number of input and output signals of APCS of GDS, type and measuring range of the sensors are specified after placing an order to the equipment and during commissioning work at the facility. Amount of information, transferred to the upper level and to the telemechanics system, as well as to the display on the operator's workstation are specified during development of software of APCS of GDS.

Functions of GMS operator’s workstation:

User interface of APCS of GDS

On the main display there is a general P&ID with current state of GDS equipment and process parameters. A separate area of the display is for emergency problem indication such as “Accident”, “Fire”, “Security”, etc. At the lower part of the display there are navigation buttons that help the user to move between the mnemonic schemes and to open setup windows and windows of other parameters of the system. Isolation valves (pneumatic and solenoid valves) are controlled directly via mnemonic scheme of equipment.

Commercial gas flow rate:

Our company integrates FloBoss 107 flow computer for commercial flow metering to the ACS of the GDS system. FloBoss 107 flow computer is a new process platform for the FloBoss flow computer family including a code modularity, versatility, high performance and ease of use. Regardless of whether the flow computer is required for one or more flows, or for several or multiple I/O points, FloBoss 107 solves all of these tasks. FloBoss 107 meets the users’ requirements of the flow computer. You also receive all the proven functions such as complex calculations that conform AGA standards, data archiving, extensive communication capabilities, economical power consumption, P&ID control, sequential control of the Function Sequence Table (FST) by programming and as well possibility of operation at extreme temperatures.

Basic protection algorithms:

• closing of input and output valves when the gas pressure at the outlet of the gas distribution system exceeds the specified emergency limits;
• closing of the input and output valves and opening of the vent valve, blocking the activation of the sure venting system of the GRS units during fire in the compartments;
• cutting off of the gas heater (heat exchanger) and opening of the valve at a bypass line when the tube bundle is broken in the heat exchanger;
• main line changing to a backup reduction line;
• gas supply shutdown to the boilers if a maximum allowable value of the gas pressure for own needs and the concentration of fuel and carbon monoxide is exceeded;
• switching on of the sure venting system when the concentration of combustible gases in the compartments of the GDS is exceeded.

Valve with an electric actuator	Valve with a pneumatic actuator	A sure venting system

For safety of maintenance personnel during maintenance and repair work at the GDS, automatic algorithms for the GDS protection and prohibition of the actuating unit control from the upper level are provided. Reliability and efficiency of the automated control system is achieved by the use of equipment of leading foreign and domestic manufacturers, a galvanic isolation of the inputs and outputs of the flow computer from the primary sensors and actuating units.