Typical Faults of Combustible Gas Detectors
Faults mainly arise from improper operation, insufficient understanding of detector performance, incorrect model selection, non-compliant installation and construction, and inadequate maintenance. The following analyzes common faults caused by improper operation of combustible gas detectors and specifies correct operation methods to minimize failures of gas alarms.
① Improper Operation by Users During operation, if air conditioners or heating equipment are installed close to combustible gas detectors, direct cold or hot airflow blowing onto the detector may alter the resistivity of the platinum wire and cause measurement errors. Therefore, combustible gas detectors shall be kept away from air conditioners and heating equipment to avoid faults induced by poor positioning. Electromagnetic interference shall also be prevented. The installation position, mounting angle, protective measures and system wiring of combustible gas detectors shall all be designed to mitigate electromagnetic interference. Electromagnetic disturbances affect the detectors mainly through three pathways: airborne electromagnetic waves, narrow pulse clusters on power supply and I/O cables, and static electricity from human bodies.
For instance, installation adjacent to air conditioners will lead to detection deviations; detection cables routed in close proximity to high-power cables such as power and lighting wires without anti-interference measures will also produce inaccurate readings. Operators shall watch for fault-prone factors including dust, high temperature, humidity and rain exposure. If an exhaust fan needs to be fitted at a site with a combustible gas detector and is placed next to the detector, leaked combustible gas cannot fully diffuse to the sensor, resulting in delayed detection and missed hazard response.
In addition, proper arrangement of combustible gas detectors in explosion-proof areas must be considered. For Class A plants where combustible gas is released, explosion-proof combustible gas alarms shall be selected with an explosion-proof rating no lower than that specified by applicable codes. Avoid installing combustible gas detectors in locations exposed to high temperature, high humidity, steam or oil fume. Do not place or hang objects on the detector. Once installed, the detector shall not be relocated arbitrarily. Where possible, select models with replaceable sensor probes for convenient maintenance.
② Maintenance and Servicing To measure combustible gas concentrations, the detector must communicate with the ambient atmosphere. It is inevitable that contaminated gases and dust enter the detector, which will degrade its working condition. Combustible gas detectors often operate in harsh environments, many outdoors. Poor maintenance will cause reading deviations or complete detection failure. Regular cleaning and maintenance are therefore essential for fault prevention. Earthing connections shall be inspected periodically. Substandard or missing earthing makes the detector vulnerable to electromagnetic interference and subsequent malfunctions. Component ageing is another root cause. Reliability data and field experience show that fault rates caused by component ageing rise sharply for systems with service life exceeding 10 years. Units beyond their specified service life shall be replaced promptly.
③ Non-compliant Construction Workmanship Improper construction will trigger detection faults during service. Examples include installing the detector away from potential gas leakage points or placing it next to exhaust fans, so that leaked gas cannot reach the detector in time and hazards remain undetected.
For residential applications, combustible gas detectors shall be mounted near gas pipelines and cookers in kitchens. For natural gas, install the detector within 300 mm below the ceiling. For liquefied petroleum gas, install the detector within 300 mm above the floor. A combustible gas detector without reliable earthing cannot eliminate electromagnetic interference, which disturbs voltage signals and yields inaccurate readings. Reliable earthing must be implemented during construction. Gas alarms and terminal blocks shall not be placed in locations prone to mechanical impact or water ingress, which may cause open or short circuits. Welding must adopt non-corrosive flux; otherwise, corrosion at joints may lead to disconnection or increased line resistance and impair normal detection. Avoid dropping or knocking the detector. Commissioning shall be carried out upon completion of construction to verify normal operation.
