Let’s discuss how flow rate is controlled in gear pump types /

Generally, there is backflow inside the pump, and adjustments are usually made based on this. Of course, slightly increasing the inlet pressure and reducing the resistance in the outlet pipe can also help a bit. I haven’t seen any other methods; after all, in practical applications, gear pumps are used quite rarely, and only in very small pumps. It is auxiliary equipment belonging to the gas station system.

Reply to 1# Yuru Yucheng: Adjust the flow rate of the outlet pipeline; the excess flow can simply be returned to the inlet

The approach is as follows: 1. By adjusting the speed of the gear pump, it is possible to reduce the speed (using frequency conversion or by changing the size of the pulley) in order to decrease the outlet flow rate. Increasing the speed can raise the flow rate, but it should not exceed the allowable maximum speed (which also depends on factors such as the viscosity of the fluid being transported; high viscosity makes it inappropriate to increase the speed). Otherwise, instead of an increase in flow rate, the pump’s noise and vibration may increase, which also affects its service life. 2. For gear pumps that do not have a safety relief valve built into them, the gate valve on the outlet pipeline can be adjusted to allow excess fluid to flow back to the inlet. It is not possible to close the outlet valve completely on gear pumps without a safety relief valve, as this can lead to problems such as the rupture of the outlet pipeline or the jamming of the pump ； Gear pumps equipped with safety relief valves can also adjust the flow rate in the outlet pipeline to a certain extent by adjusting the relief pressure of the safety valve.

By adjusting the speed or the backflow in the branch line, a gear pump is a positive-displacement pump; changing the size of the inlet and outlet cannot alter the flow rate

For the gear pumps used in ordinary gas stations, it is sufficient to adjust the outlet backflow to control pressure and flow; there is no need to change the speed of the gear pump. However, for large gear pumps such as polyester melt pumps, it is necessary to control the pump’s speed.

Reply to 1# Yuruyu Cheng: Add frequency conversion

1 Adjust the speed; 2 Branch return flow; 3 If the pump is equipped with a unloading valve, the flow rate can also be adjusted by changing the opening degree of the outlet valve, but the outlet valve should not be closed completely – a certain flow rate must be maintained; 4 Closing the inlet valve for adjustment can cause cavitation.

1. The method of adjusting the rotational speed is the most reasonable in principle, but its drawback is the high initial investment cost, and it cannot be used for gear pumps that are already installed on site and do not have variable frequency drives. 2. Pipeline adjustment: Connecting pipes and valves are installed on the inlet and outlet pipelines to regulate the connecting valves and allow some of the fluid to flow back to the inlet; the downside is that this results in energy waste. 3. Adjusting the gate valve on the outlet pipeline also wastes energy. 4. Adjust the gate valve on the inlet pipeline; proper adjustment can help control the flow rate and also result in lower energy consumption by the pump. However, the range of adjustment should not be too large, to avoid severe cavitation in the pump that could cause intense vibrations.

The speed of a gear pump can be controlled without the use of variable frequency drives; permanent magnet drives can be used to control its speed, thereby enabling control over the outlet flow rate of the gear pump. http://www.csetcorp.com.cn/

The flow rate of a conventional gear pump mainly depends on the rotational speed, the module of the teeth, the number of teeth, and the tooth width. 1. The higher the rotational speed, the greater the flow rate for the same structural dimensions; this is generally determined by the motor selected. 2. When the external dimensions remain constant, the fewer teeth there are, the larger the module will be, and consequently the flow rate will also be higher. 3. The tooth width is proportional to the flow rate; however, the greater the tooth width, the higher the load on the bearings, which results in an increase in the pump’s size and a reduction in its lifespan! :)