In numerous applications, it is neither desirable nor practical to expose a temperature sensor directly to a material. Wells are therefore used to protect against damage corresion, arosion, aborsion and high pressure processes. A thermo well is also useful in protecting a sensor from physical damage during handling and normal operations.
Materials used in thermo wells: Stainless steel, Inconel, Monel, Alloy Steel, Hastelloy
■ 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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