In any type of work environment where employees work in isolated areas, it can be difficult to accurately monitor the area for combustible gas levels that may result in fires. To do so effectively requires the use of specialized monitoring devices known as Lower Explosive Limit detectors.
Lower Explosive Limit detectors, commonly referred to as LEL monitors, play an important role in various industrial facilities throughout many industries. With many factors at play during the monitoring process, it becomes important to pay attention to details, as overlooking one important element of the monitoring process could result in tragedy.
LEL Detection Principles
An LEL gas detector is designed to detect the presence of combustible gases such as hydrogen or hydrocarbons like methane, propane, or gasoline fumes. Most common LEL detectors use either Catalytic Bead sensors or Infrared Absorption sensors. CatBead sensors, as they are commonly known, detect gas by burning a small amount of gas (carefully!) on a hot wire; the resulting heat changes the wire’s resistance and indicates the presence of gas. Infrared Absorption sensors detect combustible hydrocarbon gases using a frequency of infrared light that is absorbed by the hydrogen-carbon bonds in hydrocarbon gases.
Detection of Multiple Gases
When using an LEL gas detector, it is common to include a second sensor to detect oxygen depletion or toxic gases such as hydrogen sulfide or sulfur dioxide. Dual-channel detectors such as the GASMAX II and GASMAX CX make it easy to add a second local or remote sensor.
Up to a few years ago, battery-powered wireless LEL detection was impractical given the amount of power required to operate an infrared sensor. Recent advances in sensor technology now allow battery-powered detectors to continuously monitor for explosive levels of combustible gas for more than six months. Information from the wireless sensor is transmitted to a central controller every five minutes, and more often if high levels of gas are detected.
Pro Tip: LEL detectors can be programmed to send real-time reports and alerts to a website or manager’s smartphone. Get in touch with our expert team to find out how.
Of course, to ensure that the value shown on the monitor and recorded in the plant management system is accurate, LEL gas monitors must always be properly calibrated. Ignoring the need for calibration can lead to catastrophic results. To make sure this does not happen, many of today’s LEL gas detection devices are designed with electronics and software that simplify the calibration process and/or provide helpful reminders when calibration is due.
Confined Space Monitoring
One of the most important areas to monitor are confined spaces where equipment malfunctions or leaks in pipes or valves can occur, resulting in a build-up of combustible gas. Sample draw monitors that incorporate integral sample pumps and low-flow warning devices can be mounted outside the confined space and continuously monitor the air inside the space for the presence of combustible or toxic gases, reducing the risk of explosion or injury in the event that a leak should occur.
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