PRESSURE MEASUREMENT DEVICES
Selection of the Appropriate Pressure Gauge for Accurate Pressure Measurement
Pressure measurement devices serve to measure the pressure in the food factory’s process and utility infrastructure, allowing detection of system malfunctioning, unsafe conditions and leaks.
Liquid-Filled Pressure Gauges
Open manometers measure pressure relative to the local barometric pressure, and therefore are not very accurate. On the other hand, the closed manometer is a simple and exact, low-cost gauge for measuring pressure independent of the atmospheric pressure. Unfortunately, its use in food plants is limited because of its size and being prone to breakage. If the gauge fluid is mercury (usually), it may contaminate the process, but the use of food grade oils instead of mercury may reduce that contamination risk. These oils also may increase the sensitivity of a closed manometer. When liquid-filled vacuum pressure gauges are used for pressure measurement in vacuum systems, low vapor pressure oils must be used. High vapor pressure oils may contaminate vacuum processes because the working liquid may evaporate if its vapor pressure exceeds the pressure within the vacuum system (Moerman, 2013a).