IPP&T – October 2015
Mechanical pressure gauges have been around for over 160 years. The bourdon tube was patented in 1849 and it is still used in most pressure gauges today, and will be for many years to come. It is a reliable measurement concept and very cost effective. It is used to measure pressure from vacuum up to thousands of PSI.
Mechanical pressure gauges are used in several different applications from light commercial to heavy industrial. Some applications have extreme temperatures, some have corrosive media, and some have high vibration. The problem with vibration is it makes the pressure indication impossible to read and adds stress as well as wear and tear to the gauge mechanism thus reducing its life span. To counter the effects of vibration, the pressure gauge case has historically been filled with a high viscosity liquid which creates a “molasses” effect and absorbs the vibration resulting in a stable pointer and pressure indication. Common fill liquids include glycerin and silicone.
Unfortunately, there is a down side to liquid filling pressure gauges. The liquid may leak while the gauge is on the shelf, during transport or in the field, creating a mess and possibly a safety hazard. Another disadvantage is discoloration of the liquid when exposed to UV light or high heat which makes the gauge difficult to read over time. It also limits the operating temperature range of the gauge, thus also limiting its application in cold and hot temperatures. There are a few more disadvantages, but you probably get the idea.
New technology has now been developed that creates an equal stabilizing effect to liquid filling, but without filling the gauge with liquid. How? First, a dampening silicone is applied directly to the pointer movement only as opposed to the complete case, greatly reducing the required quantity and the resulting overall weight. Second, the silicone is contained in a sealed chamber which avoids its evaporation and maintains lubrication to the pointer movement.
The new technology has been submitted to severe cycle and high temperature testing with tremendous results. After thousands of cycles and multiple hours of being exposed to high heat, the performance of the dampening movement remained optimal and the accuracy as specified. this proves that this new technology will thrive in heavy industrial applications where the ambient temperatures are high and where there is frequent cycling.
Technology is constantly evolving, even in a mechanical world where the same sensing mechanism has been used for almost two centuries. Liquid filling of pressure gauges offers some protection against vibration, but the new dampening movement offers the same results with additional advantages. It has proven to be reliable in the toughest of applications and it is gaining more and more recognition throughout the engineering world. The time has come to move from traditional liquid filling and its problems and embrace a modern, optimal dampened movement.