Vibration alarm and shutdown time setting issues
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In large boiler feed pumps, the pump passes through a vibration peak rapidly as it starts up and reaches its normal operating speed; at this time, the vibration level can reach or even exceed the set alarm threshold, and it is not desirable for the DCS to generate false alarms in such situations. The duration of the monitored vibration is an important factor in determining whether a real fault requires an alarm or whether a brief start-up of the pump can be ignored. Now, the instrument requires a DCS program to set this time value. I would like to ask fellow experts how to determine such a short time interval – 3 seconds? 5 seconds? Are there any relevant standards? Thank you! !
It is recommended to measure the actual duration of this vibration peak before setting a value
Initial data from the equipment personnel/manufacturer is required before conducting on-site tests; be aware of deviations caused by signal interference. This setting cannot be determined by the instrument operator.
For example, when we start up the system, some interlocks need to be disabled; for instance, the pressure in the fuel gas line is always low at startup. If interlocks were in place, wouldn’t it be impossible to start the system ever? The same principle applies here as well: when this alarm or interlock system is activated, it’s possible to use a bypass route, but be sure to restore things to their normal state afterward. There’s no need to worry about such things
Thank you, what you say makes sense. I want to know if it’s possible to set this through programming, for example by calculating the alarm time so that no alarm is triggered during those few seconds. This can effectively filter out some false positives.
You are absolutely right; the measured time is the most accurate. However, before the newly installed equipment starts operating, this value can only be used as a reference based on the manufacturer’s advice.