The most common range for differential range for liquid measurement is 0-100. This range is high enough to minimize the errors caused by unequal heads in the seal chambers. It is also dependent on the differences in the temperature of the load lines. The 100 range permits an increased in capacity up to 400. While decrease down up to 20 by merely changing the range tubes or range adjustments.
■ TRIP : The term trip refers to an action that is initiated by the control system and which forces a device or devices to a pre-determined state. Example of Trip Signals: Close Valve, Open Valve, Stop motor, etc. The Safety Instrument System (SIS) or a Hardwired systems normally initiate trips, however the PLCs or DCS may also initiate trips provided the necessary independence and SIL ratings are met.Once a device or devices have been forced to a pre-determined state by the action of a Trip they will remain in that state until the Trip is manually reset by a conscious operator action. For example: High level in a vessel initiates a trip system which stops the pump feeding that vessel, the pump will remain stopped even if the level in the vessel falls to a safe level. The Trip must be ‘reset’ by the operator before the pump can be re-started. The Trip can only be ‘reset’ if the level in the tank has fallen to a safe level. Resetting the Trip will no...
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