Standard operating procedures for centrifugal blowers
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Could any member provide the standard operating procedures for the centrifugal blower in a heating furnace (positive pressure furnace)? Thank you. Should the inlet and outlet valves be fully opened first before starting the motor, or should it be started in the same way as a centrifugal pump?
It is the exact opposite of the starting method for centrifugal liquid pumps. The standard practice is to keep the fan outlet fully open (or the vent valve fully open), and the inlet slightly open (or at the opening specified in the instructions). This is the startup at the minimum load. The same is true when shutting down: the load must be reduced to a minimum before shutdown. Exceptions apply to emergency shutdowns due to accidents. Once the equipment is operating properly, refer to its rated current and gradually increase the inlet valve until the current remains within the specified range, ensuring that it does not exceed the allowable current level. Then gradually close the vent valve; once the pressure reaches the desired level, the discharge valve can be opened while keeping the pressure constant, with the vent valve remaining closed. For systems with direct delivery, speed control is used; or in cases where the fluid is discharged directly into the system, only the inlet valve is used for regulation. The minimum load for a centrifugal water pump is with the outlet valve fully closed and the inlet valve fully open; this represents the lowest load condition for starting the pump, and the same applies when shutting it down. After startup, use the outlet valve to adjust the flow rate to the specified range.
What was said on the 2nd floor is correct and quite detailed as well. The inlet is slightly open, and no value for the valve opening degree is provided, as the characteristics of each fan vary; this value needs to be determined based on the fan’s surge curve. The manual for the regular compressor here with a capacity of 20 t/h specifies that the opening angle of the inlet valve should be 3 degrees (90 degrees corresponds to full open). We have conducted experiments on starting the inlet valve at 0 degrees, and the static negative pressure at the inlet is extremely high. Big enough to deform a 1mm thin iron blind plate into a lump! Therefore, it is essential to fully open the outlet valve when starting the fan. Fully closing the inlet valve may cause the fan to flatten its own volute. Fully opening the inlet valve may cause an excessive starting current in the fan, leading to the motor overheating and stopping. Ask the fan supplier for the required opening degree; if that’s not possible, you can conduct experiments with an opening degree of around 15. After starting, gradually increase the air volume to its maximum value according to the reference current specified on the second floor