As a clean energy source, natural gas has been widely used in residential life and industrial production. However, due to its flammable and explosive characteristics, it is very easy to leak and cause dangers such as explosions and fires in the event of external or human errors. Therefore, in order to use natural gas safely and reduce or eliminate accidents caused by gas leakage, installing a combustible gas alarm system has become a necessary safety protection measure in the use of gas.
1. Composition of gas alarm system
(1) Combustible gas detectors. A high-precision sensor is used to detect combustible gas. When combustible gas is found in the air,
the detector will send out a signal and transmit the signal to the combustible gas alarm controller,
which will immediately display the gas concentration. The concentration of the gas is to be measured.
(2) Combustible gas alarm controller. The controller receives the signal triggered by the point-type combustible gas detector. When the measured gas concentration reaches or exceeds the set value,
the controller will send out an alarm sound and light signal and indicate the alarm location,
and at the same time send an alarm signal to the PLC station control system.
The PLC control system controls the corresponding control valve to stop operation according to the alarm signal.
Real-time monitoring of gas leakage in the gas filling station to ensure the safe operation of the gas filling station.
(3) PLC control system. The terminal responsible for the automatic control of the gas filling station collects the pressure, temperature,
and alarm signals during the operation of the gas filling station, controls the opening and closing of the emergency shut-off valve of the gas filling station and realizes the safe and stable operation of the gas filling station.
2. Form of gas alarm system
(1) Bus system
The bus system is an automatic control system composed of all combustible gas detectors connected to the controller through the control bus. This mode has fewer system lines, is easy to install and debug, and has good compatibility. It is currently the most commonly used alarm system mode. It is suitable for scenarios with large scale, many detection points, and equipment such as shut-off valves and exhaust fans that need to be linked.
(2) Multi-wire system
The multi-wire system means that each combustible gas detector is connected to the alarm controller through signal wires. This mode has good stability and high reliability. However, there are many cables and pipes, the installation and debugging are complicated, and the flexibility is poor. Ideal for small gas projects.
3. Working principle of gas alarm system
When the detector detects that the concentration of combustible gas in the environment reaches 20%, the alarm controller sends out an audible and visual alarm, and the PLC system controls the emergency shut-off valve to automatically close, and the alarm point is located at the upstream gas source to avoid leakage expansion. If the alarm point is in a confined space, the PLC will close the emergency shut-off valve and at the same time start the exhaust fan for ventilation to quickly reduce the gas concentration and avoid danger.
4. Combustible gas alarm settings.
The installation position is determined according to the specific gravity of the detected gas and air.
The measured gas is heavier than air, and it is easy to accumulate in low-lying places.
At this time, the detector should be installed in low-lying areas prone to leakage.
The gas to be measured is lighter than air, and it spreads upwards rapidly after leakage.
If it is an open outdoor area, install the detector 1-1.5m above the pipeline, and set one at an interval of 5 meters.
If there are physical beams and other shelters next to the detector, the number of detectors should be increased according to the actual situation.
This enables leaks to be detected early and dealt with promptly. If the measured area is a relatively confined space and the height is less than 5 meters, the detector can be placed on the top beam to increase the detection area, but the layout spacing should not exceed 8 meters.
5. Setting of combustible gas alarm controller
The alarm controller is usually installed in the PLC control room, or the duty room with people on duty throughout the day. When a leakage accident occurs, someone can quickly make a judgment and deal with it in time.
Finally, the gas alarm system has become one of the most powerful safety guarantees under the rapid application and development of natural gas, and it is of vital significance to the safe operation of gas filling stations.