Self-starting of large flow pumps
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The designed flow rate of the feed pump for the bottom reboiler furnace in our installation is 1900m3/h; the interlock is designed to be self-starting. When there is a problem with the operating pump, the backup pump will start automatically. Experts, let’s discuss the advantages and disadvantages of self-starting backup pumps.
advantage: Automatically replaces manual work, enhances process stability, and reduces adjustment operations caused by fluctuations ； shortcoming: Normally, it is necessary to check the integrity of the spare equipment, and at the same time, it is necessary to conduct irregular performance tests on the interlocking instruments. Maintenance work is critical.
So what are the requirements for the motor? After all, the rated power is above 1000KW, and the starting current may be several times that of normal operation.
Our logic is designed like this: 1. The inlet shut-off valve is closed. 2. The tower liquid level is low and the pump is stopped. If the outlet pressure is low, the backup pump will start automatically.
The motor is required to run continuously for 24 hours. The number of starts of the motor is less than or equal to 3 times per hour. The starting cabinet parameters should be set conservatively to ensure the success rate of one start.
Does such a large motor need to be soft-started?
The first thing to consider in automatic starting is the starting method of the pump. Secondly, the automatic control of the inlet and outlet valves of the pump must be determined according to the type of pump. For example, the inlet and outlet settings of centrifugal pumps and vortex pumps are different. If the process has special requirements, the impact on the process conditions when the two pumps are switched should be considered and the delay mechanism should be appropriately set. Therefore, the automatic switching of the pump must comprehensively consider equipment, electrical, and process conditions. There will be no fixed pattern.
advantage: Self-starting is possible * * Shorten the pump startup time to ensure the pressure at the pump outlet and prevent dry burning accidents in the reboiling furnace. shortcoming: The instantaneous power when the pump starts up is too large, and the motor is easily overloaded instantaneously.
It seems that there are many issues to consider when starting a centrifugal pump as large as 1000kw. Has anyone done this before? What was the result?