[Abstract] This paper summarizes a rare accident involving the crankcase explosion of an air conditioning compressor. Through eyewitness recollections, on-site investigation, and analysis of the explosion mechanism, it was determined that this was a crankcase oil mist explosion accident. For safety reasons, corresponding operating procedures and precautions are formulated. [Keywords] Air conditioning compressor; crankcase; explosion accident; liquid receiver; relay failure 0 Introduction The compressor is a key component of the four major parts of a ship's air conditioning refrigeration system. To ensure the safe operation of the refrigeration system, protective devices such as high and low pressure relays, low-pressure oil relays, and motor overload protection are installed on the compressor. Due to the high management requirements of refrigeration equipment, each company's ships have established strict operating and maintenance procedures. However, due to deficiencies in management and technical level, situations such as poor cooling effect or partial damage to certain components may occur, but serious damage accidents are generally rare. As for a major accident like a crankcase explosion, it is unheard of. Recently, the author learned from the shipping industry that an air conditioning compressor crankcase explosion accident occurred on a certain ship, resulting in the tragic deaths of the ship's chief engineer and first engineer. 1. Accident Overview During the voyage, the weather turned hot. The chief engineer, along with the watchkeeping engineer, went to start the air conditioning system, which had been idle for a long time. The chief engineer did not perform a comprehensive leak check; instead, following usual practice, he simply topped up the system with electrolyte. After running for about 20 minutes, the chief engineer felt the system was ineffective and went to inspect the air conditioning room himself. At this time, the chief engineer and the watchkeeping engineer also returned to check and saw the chief engineer in the air conditioning room. The chief engineer then ordered the engineer to inspect other areas. The engineer had just stepped out of the air conditioning room when he heard a loud bang. He immediately returned and found the chief engineer had been struck by metal fragments and died instantly. The chief engineer was also struck by metal fragments and suffered extensive burns from an oily substance; he later died despite hospital treatment. According to the engine room mechanic who was on duty with the chief engineer, the situation was as follows: The chief engineer knew the high and low pressure relays were malfunctioning; before adding refrigerant, the chief engineer did not perform a system refrigerant check, assuming that based on past experience, prolonged shutdowns would lead to refrigerant leaks and therefore replenishment was necessary, but he did not calculate the required amount; the refrigerant was added through the multi-channel before the compressor; the compressor inlet and outlet valves were opened, but other valves remained closed. After the accident, on-site inspection revealed: the receiver liner outlet valve was not open; the high and low pressure relays were malfunctioning; the compressor oil pan was broken; the high and low pressure gauges and lubricating oil pressure gauge were all normal; the thermal relay was normal; the engine room log showed that all parameters were basically normal during the last operation, with the discharge pressure slightly higher than normal. [b][align=center]For more details, please click: Analysis of the Cause of the Air Conditioning Compressor Crankcase Explosion Accident on a Certain Ship[/align][/b]