Pump; Miscellaneous; Relay Behaviour Under Fail-Safe Conditions; Alarm Relays - Siemens SITRANS L 7ML5400 Operating Instructions Manual

Flowrate
Available for LUT440 (OCM) model only.
In high alarm, the alarm state becomes active when the flowrate exceeds High Flowrate
Value ON and inactive when the flowrate falls below High Flowrate Value OFF. In low alarm,
the alarm state becomes active when the flowrate falls below Low Flowrate Value ON and
inactive when the flowrate rises above Low Flowrate Value OFF.
7.2.2.2

Pump

Setpoint - ON / OFF
If the ON setpoint is higher than the OFF setpoint, the relay operates as:
• pump down control
If the ON setpoint is lower than the OFF setpoint, the relay operates as:
• pump up control
7.2.2.3

Miscellaneous

Totalizer and samplers
Refer to Other Pump Controls (Page 114). Relays are normally de-energized, contact closure is
approximately 200 ms duration.
7.2.3

Relay behaviour under fail-safe conditions

A fail-safe condition generally indicates that the level reading is not reliable or is unknown. In
such a situation, pumps will not run and alarms (that are based on level or a derivative
reading) will not activate. The following describes this behaviour in detail, by relay function.
7.2.3.1

Alarm relays

Any alarm that is based on level, or a reading derived from level such as flow rate, will not
activate if there is a fail-safe condition. If the fail-safe condition occurs and the alarm is
already active, the alarm will de-activate.
The following alarm types will de-activate during a fail-safe condition:
• High Level
• Low Level
• In-bounds Level
• Out-of-bounds Level
SITRANS LUT400
Operating Instructions, 04/2021, A5E33329501-AG
General Operation
7.2 Relays
87