What is halogen leak detection?

A leak detection instrument that uses gases containing halogens (fluorine, chlorine, bromine, iodine) as the leak-indicating gas is called a halogen leak detector. Such instruments are divided into two categories: the first type consists of sensors (i.e., probes) that are connected to the item being inspected; these are known as fixed-type (also known as internal-probe type) halogen leak detectors ； The second type is a halogen leak detector in which the sensor (i.e., the suction nozzle) searches outside the part under inspection; it is known as a portable (also known as external probe-type) halogen leak detector. Gases that indicate leaks include Freon, chloroform, iodoform, carbon tetrachloride, etc., among which Freon 12 is the best. The sensitivity of the halogen leak detector can reach 3.2×10-9 Pam3/s. (1) Working principle and structure: Metal platinum exhibits positive ion emission at temperatures of 800–900°C, and this emission increases significantly when exposed to halogen gases. This is the so-called “halogen effect”; a schematic diagram of the halogen leak detector manufactured using this effect is shown in Figure 8. The sensor is a diode, while the heating wire, cathode (outer tube), and anode (inner tube) are all made of platinum. The anode emits positive ions after being heated by a heating wire; the ion stream captured by the cathode is indicated by a galvanometer (or amplifier), along with an audio signal. The electrical section consists of a heating power supply, a DC power supply, an ion current amplifier, an output display, and a power supply for the portable suction device. (2) Performance testing methods: Sensitivity, response time, and recovery time are the main performance parameters of halogen leak detectors. Its testing method is the same as that of a helium mass spectrometer leak detector, so it will not be repeated here. However, the indication of the halogen leak detector is related to the concentration of halogen gas: generally, the indication is linear at low concentrations, nonlinear at moderate concentrations, and the instrument becomes saturated or poisoned at very high concentrations. Therefore, during performance testing or leak detection, the concentration of halogen gas entering the sensor should not exceed one part per million. The sensor of a fixed halogen leak detector should operate within a pressure range of 10-1 to 100 Pa; pressures that are too high or too low will result in a decrease in the instrument’s sensitivity.

Only halogen gas leak detectors were found; these detectors are capable of detecting leaks of various types of gases. When the leaking gas source approaches the leak detector, the instrument emits an alarm, and the speed and frequency of this alarm increase as the amount of gas increases. Sensitivity: Turns on automatically when powered; can detect even extremely minor leaks with a leakage rate of 14 grams per year. Response time: Instantaneous. Power supply: Two AA alkaline batteries; operational life of 50 hours. Detects SF6 gas leaks from electrical switches, as well as leaks of various JFC, CFC, and HCFC refrigerants. The high-efficiency pump built into the probe reduces the instrument’s response time; large amounts of refrigerant do not “poison” the probe. Leaks can be detected even in heavily polluted atmospheric conditions. The measurement accuracy is high and reliable, with stable detection data; digital display, wide detection range, long-term stability. Handheld design, compact and lightweight, short warm-up time, rapid response, long service life. Dimensions: 120×60×25 mm. Weight: 200 grams. Battery: 9-volt alkaline battery. Probe: Highly selective semiconductor oxidation probe. Warm-up time: 20 seconds. Response time: 5 seconds. Operating temperature: 10–40°C. Accuracy: ±0.01% at 0.10% BAC. Calibration: BAC simulator