Seismic pressure gauge of oil why will change color?

Oil filled seismic pressure gauge filled medium generally has two kinds of glycerol and silicone oil, to fill glycerol as the main mode of production. Fill glycerol in order to effectively reduce the pressure gauge is the purpose of the movement and the vibration of the spring tube and make operation indicating numerical pressure gauge smoothly, to effectively increase the service life of pressure gauge. Glycerin pale yellow factors influencing oil filled pressure gauge is the following: 1. Manufacturers use glycerin is too cheap. 2. The oil filled pressure gauge (inner core The spring tube and copper head) After welding of the cleaning process, pressure gauge of steel pipe and copper after high temperature heat welding, produce a large number of oxide and the residual flux on the surface, such as not to clean, after the oil filled pressure gauge in a short period of time will be yellow. 3. Oil filled pressure gauge using occasions of high temperature influence, undermining glycerin internal composition, the glycerin physical properties change and the metamorphic yellowed.