The working method of using an infrared thermometer to check the leakage of the air supply pipeline
1. Fault report
When the aircraft is in the air or on the ground, a BLEED 1/2 LEAK fault message appears in the CAS area (Crew Advisory System) of the central instrument panel of the aircraft after the air conditioning component is turned on for a period of time. This type of malfunction is a frequent occurrence of the 145 aircraft in hot weather with humidity sensor probes, stainless steel electric heating tube PT100 sensors, cast aluminum heaters, and heating coil fluid solenoid valves
In the first few years of the operation of our company's E145 aircraft, maintenance personnel mainly isolated faults in the BLEED 1/2 LEAK based on the Fault Isolation Manual (FIMs). The main troubleshooting steps provided by FIMs are as follows:
(1) According to the AMM manual, conduct the operation and testing procedure for the air injection system, connect external high-pressure nitrogen gas to test the sealing of the pipeline, to verify the fault phenomenon and determine whether the fault is intermittent. This test requires relatively complex equipment and takes a long time, which must be completed at the main maintenance base.
(2) Use a hot air gun and thermometer to check the overtemperature detection switches in all pipeline interface areas, as shown in the following figure. There are 17 overtemperature detection switches on the left engine air duct of E145 aircraft, and 14 overtemperature detection switches on the right engine air duct. All switches are tested one by one, with a large inspection range and a long time to stop for troubleshooting. The work is very difficult and the accuracy is also poor.
(3) If no problem with the overtemperature switch is found, then check the relevant circuit condition. This inspection mainly relies on a multimeter, which is a complex task and the actual troubleshooting effect through measuring the line is very poor.
(4) After completing the above testing work, conduct leakage checks on the interfaces of each section of the air intake pipeline. During the initial troubleshooting, the engine needs to be running and the air conditioning components need to be connected for air supply. The main method of finding the leakage point is through visual inspection and hand feeling. Due to the high temperature of the leaked air supply, it can sometimes reach over 150 ℃, which poses a considerable risk. In addition, the critical temperature of the overtemperature switch is around 91 ℃, which lacks accuracy when using visual or tactile methods* After using an infrared thermometer for temperature detection, this problem was completely solved.
