METHOD AND APPARATUS FOR OVERRANGE PROTECTION OF THE TRANSDUCER IN A DIFFERENTIAL PRESSURE TRANSMITTER

摘要

ABSTRACT OF THE DISCLOSUREA method and apparatus for protecting the transducer inliquid-filled differential pressure transmitter having strokelimited, isolation diaphragms from exposure to overrange pressureare disclosed. Bidirectional overrange pressure protection isprovided through the use of a single, preloaded bellows that isrestrained by a preloaded stop means preferably including apreloaded mechanical spring. The bellows remains stationary whenthe differential pressure transmitter is exposed to a normal,operational differential pressure. When an overrange pressure isapplied to the transmitter, the bellows expands or contracts toaccommodate the liquid displaced by either of the isolationdiaphragms thereby protecting the transducer from the overrangepressure. Upon removal of the overrange pressure condition, theprotection apparatus automatically resets itself.