ESD transmitter with voting logic

 ESD transmitter with voting logic

The ESD transmitter serving the critical trip level in the Safety Instrumented System is recommended to have a polling logic configuration. Election logic is used to minimize the occurrence of total loss of production due to a single transmitter failure or false trip. The voting configuration can be 2oo3 or 1oo2D based on SIL assessment and verification.

When using voting logic in a process, consider:

The transmitters should not have a common connection to the process line/equipment.

Transmitters forming the same voting logic must not be assigned to the same Safety Instrumented System I/O module.

Each instrument cable is routed differently.

The transmitters are set to the same calibration range.

It is also recommended to have third-party converters to avoid a manufacturing defect causing common mode failure. Also in this polling logic configuration, the SIS must compare the transmitter value and trigger an alarm on the Human Machine Interface (HMI) for any measurement deviations between transmitters.

                      ESD transmitter voting

On the 2oo3 polling transmitter, any one abnormal process variable detection by one transmitter will trigger an alarm. Shutdown will be initiated if two transmitters reach the shutdown set point.

Here are some examples of applications where an ESD transmitter is used with polling logic, usually part of a higher level in the shutdown hierarchy level:

Air instrument head

Export pipeline

KO drum