Causes and protection of combustible gas detector sensor poisoning
Combustible gas detector is an important alarm device for safety production, it can quickly detect the presence of combustible gases in the air and whether the gas concentration reaches the explosion limit, which can prevent the explosion from occurring at the critical moment. However, in the use of combustible gas detector sensor poisoning phenomenon sometimes occurs, so what are the causes of combustible gas detector sensor poisoning? How to protect?
Poisoning causes:
In the process industry, many chemicals will be absorbed by the catalyst or react with the catalyst to form new compounds, thereby inhibiting the catalytic reaction, and even poisoning the catalytic element and lead to a decrease in its sensitivity or even complete failure. Sensors working for a long time in the environment with these chemicals, the catalyst will be poisoned and deactivated, so that the sensitivity of the catalytic element is greatly reduced, shortening the life of the element. The most common types of these chemicals are silicides and sulfides.
1: Silicides
Silicides are often found in large quantities in compounds such as lubricants, cleaners, adhesives, sealants, etc., and are used in large quantities in the petrochemical industry, where they can significantly inhibit the response of the sensor. Silicone compounds reduce sensor response at concentrations of a few parts per million. Silicones break down catalysts and form solids on the catalyst surface in high temperature environments, leading to a reduction in sensor sensitivity, while higher concentrations of silicone compounds can cause immediate damage to the gas detector.
2: Sulfides
Sulphides, on the other hand, are easily oxidized to mineral acids, which can corrode the catalytic element and, in severe cases, even cause it to fail. Hydrogen sulfide and numerous other sulfides, when oxidized to inorganic acids may corrode the sensor. High-temperature organic acids (e.g., acetic acid), or direct exposure to acidic vapors (e.g., hydrochloric acid vapors, sulfuric acid vapors) can similarly corrode the sensor.
3:Other
In addition, heavy metals such as mercury and lead have a significant inhibitory effect on catalytic elements. Solvents such as degreasers and cleaners often contain chlorinated hydrocarbons that can affect the sensor. Some polymer plastics also release toxic chlorinated compounds when they are overheated, such as insulated PVC wires during soldering.
4:Degree of Destruction
Silicides are usually regarded as poisonous substances for catalytic combustion sensors, i.e. they completely destroy the catalyst. Sulfides, for example, are regarded as inhibiting substances, i.e. they only reduce the sensitivity of the measurement. The effects of this inhibition or reduction may be long term and unrecoverable or temporary and recoverable.
Prevention and treatment:
1: Select a catalytic element with high resistance to toxicity. Research has proved that new catalysts such as composite metal oxide catalysts prepared by chemical co-precipitation can enhance the stability of the surface of catalytic elements. Improve the anti-poisoning ability of the element. The same use of new catalysts, but the difference in toxicity between different manufacturers of products may be large, choose a better quality catalytic element can effectively improve the average trouble-free operating time of the combustible gas detector.
2:For the existence of catalytic combustion sensor can cause poisoning material environment, should be in the instrument suction pump inlet or sensor chamber before the installation of filters. Replace them frequently or immediately after exposure to toxic gases, depending on site contamination.
3:Avoid exposing the sensor to silicides and sulfides. Such as not using gaskets, seals and insulating components containing silicone rubber, synthetic rubber or sealants: not in the assembly and storage of the instrument in the environment using polishes, cleaners and lubricants containing silicides: gas piping network valves and other components should be avoided to use lubricants containing silicides: as far as possible, do not use in the surface of the instrument can be self-stick labels (this kind of adhesive often contains silicides); installation, maintenance personnel Do not use cosmetics containing silicone components, etc..
4:According to the actual situation, estimate the concentration of possible leakage of gas, choose the appropriate range of combustible gas detector, as far as possible to avoid making the sensor work for a long time in the leakage of gas under high concentration environment.
5:Reduce the exposure time in the ambient toxic gas. Turn off the instrument when not in use.
