Master Fuel Trip and SOE

The Master Fuel Trip just shuts off fuel supply when emergency such as too high pressure or too high temperature. It usually switch off the fuel pump and need to be re-set when emergency has been under control. Sequencing of events is a program usually store in the embedded memory of micro-controller that steps from one event to another. One event might be starting up boiler, so controller:opens chimney shutter; starts air supplying fan to evacuate possible fuel vapor in combustion chamber to prevent explosion; starts arc to ignite fuel, then starts fuel pump that supplies fuel to burner and checks if ignition has happened, then it refers to set points of pressure and temperature and controls fuel supply by adjusting fuel supply valve. Sometimes there are up to 100 set-points so it refers to a set-point table to get optimal supply of fuel/air mix to prevent CO2 or NOx formations. You better do not touch that if you do not know how to adjust it. There is a program that takes care of events. Sometimes the program is called firmware as it was the firm that produced the controller that stored it as Read Only, so you cannot change that without proper instrumentation

SOE can also refer to a log of what has taken place during an emergency within the control system. It is used during the postmortem of an incident. It requires that the discrete inputs be time stamped, typically to the nearest milisecond (at least that is the value most often seen in an electrical control system). The time stamp needs to be done at the input card since scan times can be longer than 1 ms, especially during an incident. Since a separate input card type is required which is typically on the order of 2x cost, the points are normally chosen during system design.