Understanding High-Pressure Centrifugal Fan Shutdown Procedures
How to emergency stop a high-pressure centrifugal fan?
Additionally, what are the main steps and procedures for normal shutdown?
These topics will be addressed in the next mini-series, relevant to everyone.
Therefore, I hope you study diligently and master them promptly.
In the event of an emergency with a high-pressure centrifugal fan, follow these steps for immediate shutdown:
(1) Sudden severe vibration exceeding trigger thresholds.
(2) Internal friction noises or abnormal grinding sounds.
(3) Irrecoverably low oil pressure. Additionally, fuel tank is empty.
The specific steps and procedures for normal shutdown of high-pressure centrifugal fans are as follows:
(1) Slowly close the exhaust valve while simultaneously opening the exhaust valve or outlet bypass valve.
(2) Gradually reduce the suction throttle and press the stop button.
(3) If bearing temperature is below 45°C, oil replenishment can be halted.
Rated Speed and Operating Costs of Backward-Curved Centrifugal Fans
Backward-curved centrifugal fans equipped with variable frequency motors enable frequency conversion operation.
While this approach increases initial procurement costs, it significantly reduces operational expenses. It is ideal for environments requiring frequent airflow adjustments, with a controllable range of 0–60 Hz. Some customers design systems requiring over 10 daily fan starts. This poses challenges for fixed-frequency motors. Excessive starting currents accelerate insulation degradation, drastically shortening motor lifespan.
When using backward-curved centrifugal fans, installing a standard fixed-frequency motor with star-delta or auto-coupling voltage reduction starting provides an economical and straightforward method. After fan startup, the damper closes. Once the fan reaches rated speed, the damper gradually opens as medium temperature rises until fully open.
The backward-curved centrifugal fan is equipped with a standard fixed-frequency motor started by a frequency converter.
This method suits operating conditions where frequent flow adjustments are unnecessary. During startup, the motor operates at a low frequency. As the inlet temperature of the centrifugal fan continues to rise, the motor frequency increases, preventing overload. While the use of a frequency converter raises the initial purchase cost, it effectively protects the motor. During commissioning, airflow can be freely adjusted, greatly facilitating system-wide debugging.
However, the adjustment range for backward-curved centrifugal fans is limited to 40–50 Hz. Centrifugal fans rotating cooling fans within cold storage units generate heat, which can impact the cold storage unit's energy consumption.
Therefore, from an energy-saving perspective, the operating time and number of backward-curved centrifugal fans must be minimized.
In actual fruit and vegetable storage, backward-curved centrifugal fans are economical for ensuring product quality, necessitating improved handling methods. For varieties requiring strict temperature control after storage temperature stabilization, 1–2 fans continue operating even after cooling and liquid supply cease to maintain uniform temperature distribution throughout the storage space.
