Long gone are the days of using canaries as early detection method of high levels of toxic gases. It was common practice through the 19th and early 20th century for miners to use canaries to detect high levels of carbon monoxide and other toxic and combustible gases down in the tunnels. Today, with the advances in electronic sensors, gas detection is readily affordable and utilized in a plethora of different applications.
This said, depending on the technology of the sensor, frequent calibration and verifications are required to insure the proper operation, stability and accuracy of the sensor cell. This applies to both fixed gas detection systems (permanently mounted systems) and portable gas detectors. Electrochemical sensors for example are designed using a chemical called electrolyte. The electrolyte reacts to toxic gases in the environment and produces a linear voltage output that can be measured and accurately determine a specific amount of gas present. Normally measured in PPM (parts per million) and set to the recommended safe levels of specific gases, this insures a safe work environment and avoids any health issues related to high exposures of toxic gases determined by organizations like OSHA. Because the electrolyte chemical dissipates with time and exposure, these sensors require frequent calibration. Most manufactures will recommend a minimum of twice yearly calibration. Depending on the environment and the amount of gas always present in an area more frequent calibrations could be required.
Therefore, how do we certify proper operation of these sensors? What is required and who is qualified to do this type of work? Hetek Solutions offers Cal Check Services across Canada utilizing trained and certified technicians. Cal Check services are an important part in assuring a safe and healthy environment for workers by offering their service on site. Hetek technicians will insure proper operation of the gas detection equipment by applying a certified calibration gas to the sensor. They then adjust the electronics for best accuracy possible and stability. The first step is to adjust the ZERO, meaning no gas present, using either fresh air or a zero-gas concentration. Once the zero is adjusted they will then proceed to apply a certified concentration of the target gas. For example, if we are calibrating a carbon monoxide sensor with a range of 0-100ppm, we would apply a target gas of at least 50% of full scale (50ppm) or the full amount of 100ppm and then adjust the span to the correct level. Sensor transmitters with digital displays are easier to calibrate as you make sure the concentration on the display is equal to the span gas. If no digital display is present, most if not all sensor transmitters include a 4-20mA output where 4mA = 0 gas and 20mA = full scale. For example, if the target gas is 50ppm, the tech using a multi-meter would adjust for 12mA output or if they are using a target gas of 100ppm they would adjust to 20mA. So, 16mA span / 2 = 8mA + 4mA = 12mA
Typical life of gas detection sensors is between 2 and 5 years. If a sensor fails, this could cause plant shut downs, health and safety issues and even high explosive environments when dealing with combustible gases. Our Cal Check technicians are trained to anticipate this before it happens. By verifying the span of the sensors, we can pre-determine if a sensor should be changed before the next visit and can avoid critical, life threatening and expensive events. Hetek also offers service contracts and sensor exchange programs where we are proactive in replacing sensors before they fail. The service contract includes (BP) periodic sensor replacement, calibration of the gas detection equipment and certification of the systems. Hetek covers all liabilities related to its service, giving you peace of mind. “Our Solutions, Your Safety”, Hetek Cal Check services provides the highest level of integrity, knowledge, and expertise in the industry.