A.6.1 Brief description of equipment
A power plant's pneumatic ash conveying system has a total of 4 screw air compressors installed as the air supply source. The air compressor specifications are 110kW, water-cooled units, exhaust volume is 20m³/min, and the motor speed is 1480r/min.
A.6.2 Fault phenomenon
The overhaul time of the air compressor is generally 20,000~30,000h. Most air compressor manufacturers set the overhaul time to 20,000h for safety reasons. Because the cost of overhaul is high, the plant decided to use condition maintenance after the cumulative operation time of the #3 ash conveying air compressor reached 30,000h. When the equipment is abnormal, the air compressor will be overhauled. After the #3 air compressor ran for 38,000 hours, the operator found that the noise of the compressor increased significantly, and the maximum vibration value was 0.085mm. The maintenance personnel recommended stopping the compressor for inspection. After disassembling the compressor, it was found that 5 teeth of the air compressor gearbox speed increase gear were broken, the keyway of the large gear drive shaft was cracked, the air compressor bearing raceway and roller had obvious wear grooves, and the main and auxiliary rotors had friction marks. During the overhaul of the air compressor, all bearings, speed increase gears, large gear drive shafts, oil seals, sleeves, etc. were replaced. After reinstallation and trial operation, the air compressor ran normally.
A.6.3 Cause Analysis
The cumulative operating time of the air compressor of the power plant reached 38,000 hours, which was nearly twice the time required by the air compressor manufacturer. A bold attempt was made, but the life of the equipment is limited after all. Indefinitely extending the operating time of the equipment can only result in equipment failure; implementing equipment status maintenance can reduce maintenance costs and extend the equipment life cycle. If the plant does a good job of equipment status maintenance, it can detect the abnormal operation of the air compressor in advance, thereby avoiding damage to the speed increase gear.
A.6.4 Preventive measures
(1) Check all air compressors, and set different overhaul times according to the operating conditions of the equipment when the operating time reaches the overhaul standard time.
(2) Do a good job of equipment status maintenance, strictly implement the equipment inspection system, and detect equipment abnormalities in a timely manner.
