Diaphragm seals are protective devices designed to isolate pressure gauges, pressure transmitters, and pressure switches from potentially damaging process media. Typical applications where a diaphragm seal provides a cost effective solution to protecting the pressure instrument are:
In applications where the process fluid is corrosive
In applications where the process fluid has a high viscosity, is comprised of slurries, sludge or other material that can actually coat or damage a traditional pressure measuring device
In applications where the process fluid can freeze or polymerize, thus causing a condition that might lead to the instrument becoming immobilized or incapable of transmitting an accurate pressure measurement or signal
Operational Theory:
Mansfield & Green brand diaphragm seals typically comprise a metal, TEFLON or elastomer diaphragm mounted between two housings and sealed to prevent leakage of process gases or fluids. The space on the instrument side of the diaphragm, the connections and the instrument- sensing element, are all completely filled with instrument oil, silicon or other suitable fluid.
When the process line pressure is applied, the diaphragm exerts equal pressure on the instrument side of the seal producing a reading on the gauge or process instrument. Instruments may be attached directly to the diaphragm seal or connected remotely by means of a filled system – typically a length of armored capillary tubing. Mansfield & Green diaphragm seals may be used with pressure or vacuum instruments including gauges, transmitters, and switches that utilize C-type, helical or spiral bourdons, bellows elements, diaphragms or electronic strain gauge sensing elements.