Chemical Compatibility of Glycerin-filled Pressure Gauges
In a Bourdon tube gauge, the important fact is for the curled tube to be compatible with chemicals in the application. Be sure to buy stainless steel gauges with 304 or 316 grade stainless construction. The glycerin is merely a viscous liquid that is used to fill the gauge dial. This reduces the twitching of the needle which can make it difficult to make an accurate measurement. In a normally functioning gauge, the glycerin is never in direct contact with the gases or liquids inside the Bourdon tube.
Some gauges have a liquid-filled Bourdon tube, in which case there is a chemically resistant diaphragm below the tube that isolates process fluids from the fluid in the gauge.
It is true that glycerin can react with nitric acid to form an explosive compound (i.e. nitroglycerin), but that reaction requires additional proton donors, say from sulfuric acid, carefully controlled temperatures, and caustic scrubbing to purify the explosive. (Don’t try this at home kids!!) Our recommendation is that gauges which have failed for any reason, be promptly replaced before resuming normal brewing/cellaring activities.
First step is to get an SDS from the gauge Manufacturer to confirm the chemical. (Note some are actually filled with silicone.) They will probably tell you the volume of glycerine used to fill it. We can compare that with the cleaner and sanitizer SDSs.
