Background:

Gas is one of the basic states of matter, and the air around us is a mixture of pure gases that naturally exist in a mixed state. So each particular gas needs to be tested. A gas detector is a small tool used to detect the presence of gas in an isolated location. The device is used to carefully search for gas leaks or other discharges and can be connected to the facility's control system to automatically shut down the process.

A gas detector as a safety device

Gas detection is necessary and is part of the safety system at most oil and gas facilities, as well as other industrial facilities, because its integration can be used to detect combustible, flammable and toxic gases. In addition, gas detection helps monitor oxygen consumption in underground terrain, such as gold and coal mines, as reduced oxygen levels can cause workers to become dizzy and possibly pass out. If the level is too low, it can cause serious brain damage or death. Gas detection can be used for fire fighting. In addition, gas detectors can issue warnings or evacuation alerts to operators in the area of a leak, giving them time to leave the site. The instrument is of incalculable importance because there are many gases that can be harmful to organic life such as plants, humans and animals.

Type of gas detector

Gas detectors can be divided into two categories according to their operating mechanism: stationary and portable gas detectors.

Portable detection system: This is often used to assist workers with tasks such as maintenance, where employees may interfere or release gases that should not roam freely in the area. Portable detectors are also a useful way of gas sampling, where workers need to measure atmospheric mass around the person, and can be held or worn on clothing or belt/suspenders. These gas detectors are usually designed to run on battery power. When harmful vapors reach dangerous levels, they send visible and audible signals via flash lights and alarms.

Fixed detection system: As the name suggests, it is mainly fixed in a location within the work area. Where they are placed in a building or processing plant depends on the density of the gas (whether it is heavier or lighter than air). Stationary detectors are usually installed near process areas in the plant or control room, or areas that need protection, and are connected by cable to a monitoring system that can be activated in case of emergency. They can be used to detect one or more gas types.

There are several types of gas detectors used for special industrial operations, including:

1.Electrochemical gas detector

Electrochemical sensors are used to detect oxygen and toxic gases. More specifically, they measure the concentration of a particular gas in an external circuit. This is done by oxidation or reduction reaction.

These reactions produce a positive or negative current flowing through the external circuit. The electrochemical sensor consists of a "working" electrode, an "opposite" electrode, and a common "reference" electrode. All of these components are located in the sensor housing along with the liquid electrolyte.

2.Photoionization detector

The photoionization detector (PID) uses a highlighter energy UV lamp to ionize the chemicals in the sampled gas. If the ionization energy of the compound is lower than that of the lamplight, electrons are ejected, and the resulting current is proportional to the concentration of the compound. Common tube photon energies include 10.0 eV, 10.6 eV and 11.7 eV. While a standard 10.6 eV lamp will last for years, an 11.7 eV lamp usually only lasts a few months, and is only used when there are no other options.

A wide range of compounds can be detected, with concentrations ranging from a few ppb to thousands of ppm. The categories of compounds that can be detected in descending order of sensitivity include aromatic hydrocarbons and alkyl iodine; Alkenes, sulfur compounds, amines, ketones, ethers, alkyl bromine and silicates; Organic esters, alcohols, aldehydes and alkanes; H2S, NH3, PH3 and organic acids. PID consists of ultraviolet lamps that emit photons, which are absorbed by compounds in the ionization chamber. The ions created in this process (atoms or molecules that gain or lose electrons and thus have a net positive or negative charge) are collected by the electrodes. The resulting current provides a measure of the analyte concentration. Because only a small fraction of the analyte molecules are actually ionized, this method is considered nondestructive, allowing it to be used in combination with another detector to confirm the results of the analysis. In addition, PID is available in portable handheld models and a variety of light configurations. The results were almost immediate.

Infrared point gas detector

The infrared (IR) method of measuring gas concentration is based on the absorption of a specific wavelength of infrared radiation as it passes through a given volume of gas. Infrared hydrocarbon gas detectors can be divided into two types: point detector and open circuit detector. For point detectors, the absorption path length is fixed, defined by the instrument design as several inches. For open-circuit infrared detectors, the absorption path length can be as long as 130 meters, while point detectors are only a few inches. Instruments based on infrared technology use two wavelengths, one at the wavelength absorbed by the gas and the other at the wavelength not absorbed by the gas. Neither wavelength is absorbed by other atmospheric components, such as water vapor, nitrogen, oxygen or carbon dioxide.

In contrast to electrocatalytic sensors, IR gas sensing technology provides fail-safe operation because optical sensing is an active technology that continuously monitors sensor failures and communicates them to the user. This is mainly achieved by using a second wavelength or a reference wavelength. Infrared detectors are also toxic and corrosion-resistant, can operate under oxygen deficiency or excess, and do not shorten sensor life due to repeated exposure to gas. Because of the precise optical and electronic designs currently used, the detectors are factory calibrated and require little maintenance.

Other gas detection devices include:

infrared imaging, semiconductor sensors, ultrasonic gas leakage detectors, catalytic beads (catalysis), holographic gas sensors, etc. It is worth noting that a multi-gas detector can be used to detect some of the detectors mentioned earlier because it is designed for events that require simultaneous monitoring of multiple gases and the detector is pre-configured to meet the user's individual needs. They are commonly used for the following gases, hydrogen sulfide (H 2 S), carbon monoxide (CO 2), oxygen (O 2), and combustibles (%LEL). All gas detectors require regular calibration to ensure accurate gas readings. You will be interested to know that you do not have to travel too far to purchase this equipment. We serve you at JXCT.