In recent years, whenever the Ministry of Emergency Management’s inspection teams conduct safety inspections and diagnostics at hazardous chemical production and storage facilities, they almost always find problems with toxic, hazardous, flammable, and explosive gas detection and alarm systems. Some companies have numerous, complex, and chaotic alarms in their control rooms; others have installed alarms but they are ineffective. These issues reflect poor gas detector management, a lack of professional knowledge, and unclear and unenforced responsibilities.
Common Mistakes in Gas Detector Installation and Use
Improper Instrument Installation Location
The installation height of the gas detector is not adjusted based on the specific gravity of the target gas. For gases lighter than air (such as methane and hydrogen), the detector is installed below the release source; for gases heavier than air (such as liquefied petroleum gas and hydrogen sulfide), the detector is installed above the release source.
Consequence Analysis: This incorrect installation height can prevent the detector from detecting leaks in a timely manner because the gas will not naturally flow to the detector. This can delay the alarm and increase the risk of accidents.
The detector is installed in an environment with harsh environmental conditions or where interfering substances are present, such as near a high temperature source, corrosive substances, or in an area with electromagnetic interference.
Consequence Analysis: Harsh environmental conditions may affect the detector’s proper operation, leading to inaccurate detection or malfunction. For example, high temperatures may cause the sensor to overheat and fail, while corrosive substances may damage the detector’s housing or internal components.
The sensor’s air inlet is blocked, or the installation orientation does not align with the gas flow direction. For example, the sensor should be installed vertically downward to avoid dust accumulation, but is actually installed facing upward or horizontally.
Consequence Analysis: Incorrect sensor orientation may cause detection delays or failure. If the air inlet is blocked, gas cannot enter the sensor for detection. If the installation orientation does not align with the gas flow direction, detection accuracy may also be affected.
Incorrect Instrument Selection
The sensor was not selected based on the properties of the target gas. For example, an electrochemical sensor is used to detect inert gases, or a catalytic combustion sensor is used to detect non-combustible gases. Alternatively, a combustible gas detector may be installed in a toxic gas environment, or a toxic gas detector may be installed in a combustible gas environment.
Consequence Analysis: The sensor may not effectively respond to the target gas, resulting in detection failure.
Failure to select a detector with the appropriate explosion-proof rating in an explosive gas environment.
Consequence Analysis: If the detector lacks adequate explosion-proof performance, it may cause an explosion upon detecting a combustible gas leak.
Failure to confirm whether the detector’s output signal type (e.g., 4-20mA, RS485, wireless signal, etc.) is compatible with the existing control system.
Consequence Analysis: If the output signal is incompatible, the detector may be unable to transmit detection data to the control system, resulting in loss of real-time monitoring and warning capabilities.
Improper Instrument Settings
Failure to adjust the detector’s range, alarm value, and other parameters according to actual needs. For example, the alarm value for combustible gas may be set too high, or the detection range for toxic gas may be set too low. Consequence Analysis: Incorrect parameter settings may prevent detectors from sounding alarms in a timely manner, or excessively high alarm thresholds may prevent them from triggering alarms even when gas concentrations have reached dangerous levels, delaying action and increasing the risk of accidents.
Failure to properly set alarm thresholds based on environmental characteristics and safety requirements. For example, in crowded areas or high-risk locations, the alarm thresholds may not be set to a more sensitive level.
Consequence Analysis: Improper alarm threshold settings may result in detectors failing to sound an alarm when necessary (missed alarms) or sounding an alarm frequently when not necessary (false alarms). Missed alarms may delay action and increase the risk of accidents; false alarms may disrupt normal production and reduce the detector’s reliability.
Failure to properly set detector interlocking functions, such as failure to link detectors with ventilation systems, emergency shut-off valves, or improperly setting interlocking functions, may result in the ventilation system not being activated or emergency shut-off valves being closed in a timely manner in the event of a gas leak, making it impossible to effectively control the spread of gas and increasing the risk of accidents.
Instrument maintenance is inadequate or incorrect.
Failure to perform regular functional checks on gas detectors, including detection response time and alarm accuracy, as recommended by the manufacturer or relevant standards.
Consequence Analysis: Prolonged failure to perform functional checks may cause aging, contamination, or damage to the detector’s internal components, thereby affecting its detection accuracy and alarm reliability. For example, a sensor may fail due to long-term disuse, resulting in a failure to promptly alarm in the event of a gas leak.
Failure to use standard gases for calibration, or improper calibration procedures, such as an unqualified calibration environment or untrained personnel, may also result in failure to perform calibration at the required intervals.
Consequence Analysis: Calibration is a critical step in ensuring the detection accuracy of gas detectors. Improper or non-calibrated calibration procedures may result in decreased detection accuracy or even complete failure of the detector. For example, using unqualified standard gases for calibration may cause the detector’s detection data to be biased and fail to accurately reflect the gas concentration in the environment.
Failure to regularly clean and maintain gas detectors, or the use of incorrect cleaning agents or methods during cleaning and maintenance, can lead to damage or contamination of internal detector components.
Consequence Analysis: Gas detectors may be contaminated by dust, oil, and other contaminants during use, affecting their detection accuracy and alarm reliability.
Failure to promptly replace aged or damaged components in gas detectors, such as sensors and batteries.
Consequence Analysis: Gas detector components, such as sensors and batteries, may age or become damaged during use. Failure to promptly replace these components may result in decreased detection accuracy or even failure.
Failure to fully consider the impact of environmental factors, such as temperature, humidity, and dust, on detector performance during gas detector maintenance. For example, in environments with high temperature, high humidity, or high dust content, appropriate protective measures or adjustments to the maintenance schedule may be made.
Consequence Analysis: Environmental factors may interfere with the normal operation of gas detectors, resulting in inaccurate detection or malfunctions. Failure to fully consider these factors during maintenance can lead to poor maintenance results and even accelerate detector aging or damage. For example, in high-temperature environments, failure to provide heat dissipation measures for detectors can cause internal components to overheat and fail.
Maintenance records for gas detectors are not maintained, or they are incomplete or inaccurate. For example, information such as maintenance time, maintenance personnel, and maintenance details is not recorded.
Consequence Analysis: Maintenance records are crucial for tracking the maintenance history of gas detectors and evaluating their performance. Failure to maintain maintenance records or incomplete or inaccurate records can result in inability to timely understand the maintenance status of detectors, making it difficult to develop effective maintenance plans or evaluate their performance.
Failure to replace instruments at the end of their lifespan
The service life of industrial and commercial gas detectors is generally three years. Some companies, to save costs or meet inspection deadlines, fail to replace instruments beyond their lifespan.
Consequence Analysis: As the instrument reaches its end of life, sensor aging leads to decreased sensitivity, potentially preventing timely response to low-concentration gas leaks.
Other Operational Errors
Because of ongoing construction nearby, company employees were concerned that dust might affect the function of the gas detectors, so they wore masks to protect them from dust.
To prevent corrosion, the company wrapped the entire gas detector in plastic sheeting, completely rendering the detector inoperable.
Some employees, dissatisfied with the loudness of the alarm, unplugged the power cord while it sounded. Plugging and unplugging the power cord while the gas detector was sounding could generate sparks, potentially leading to fires, explosions, and other accidents.
Some companies experienced mainline communication failures, some leak alarm signals were not transmitted to the control room where operators were stationed, and some companies failed to install flashing warning lights for flammable and toxic gases in the control room.
The alarm was installed but not powered on, effectively facilitating inspections and becoming a mere decoration.
No dedicated personnel were assigned to manage and maintain the alarm. On-site personnel were unaware of the alarm’s installation location and remained clueless when questioned.
The alarm nameplate was corroded or stained, and the gas it detected was not clearly labeled, making it unclear what gas it detected.
Inspectors’ primary method of determining whether toxic gas leaks is to smell them.
The effectiveness of gas detectors depends on proper installation and proper operation. Companies must strictly adhere to national standards and perform regular maintenance to ensure they function effectively and avoid significant losses.
