Automatic start of boiler feedwater standby pump
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When the boiler is operating normally, one feed pump is in use while another serves as a backup. How can the backup pump be started automatically via the DCS in the event of a failure of the pump in use? Thank you! Automatic control instruments
Set up a flow interlock: when the flow falls below a certain value, the backup pump can be activated!
Could you tell me the requirements for the DCS software?
Boiler feed water pumps are generally centrifugal pumps; therefore, it is not appropriate to use a low flow rate as the trigger for automatic startup, and instead a low pressure should be used as the trigger for automatic startup
Could you explain in detail why centrifugal pumps are not suitable to be equipped with a low-flow auto-start function? What are the effects if low traffic triggers automatic startup?
Generally, the backup pump is activated when the pressure falls below the set value, while the flow rate is often used for 3-step impulse control.
The feed water pump is controlled based on liquid level; it’s better to switch it manually – it’s not scientific. We should make changes when we have time.
The startup of the boiler feedwater standby pump can be set in two ways: 1) Based on the pressure in the feedwater main; the standby pump is started when the pressure falls below a certain value, with the flow rate serving only for monitoring purposes. 2. Furthermore, based on the operating status of the pump in use, when that status becomes 0, the backup pump is activated. The above dual interlock protections ensure that the feed water pump meets the requirements for normal process operation
Could you elaborate on the software requirements? How should this interlock function be designed to be implemented?
You make the request, and the engineer specialized in configuration will guide you on how to operate the DCS. On-site, it is necessary to provide these to the DCS: the AI value for the pressure in the feed water main, as well as the DI values indicating the operating status of pump A and pump B. Add judgment logic in the DCS to implement interlocking for the standby pump. Set up two interlock modes: 1. The interlock switch for activating Pump B when Pump A is running, followed by logical configuration; 2. The interlock switch for activating Pump A when Pump B is running, followed by logical configuration.
Pressure can reflect more directly the process conditions that occur when the pump stops, which is easy to understand once you think about it