STEM FAILURE ANALYSIS OF 4-WAY REVERSING VALVES OF AIR-CONDITION

A quantity of the 4-way reversing valves are found with water leak failure after hydraulic-pressure testing in the factory. The stems made by imported ferric stainless steel bars inside of the 4-way reversing valve have been also checked. The cracking stems was studied by means of Metallography, SEM and EDAX. It is found that there are large quantities of sulfured manganese inclusions in the sample. The water leak failure of 4-way reversing valve for air-condition is caused by the cracking stems inside, the stems cracking is caused by the large amount sulfured manganese inclusions which is distributed axially.