May I ask under what circumstances is it necessary to incorporate a variable frequency design for the pump?
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Under what circumstances is it necessary to incorporate variable frequency design for pumps?
If you need to control the flow rate, you can use pneumatic valves for control, or you can employ variable frequency control of pumps, which helps to save energy; this is a quite practical technique.
Currently, in domestic design, large-scale approaches are generally adopted; such designs ensure that no problems will arise, and they also provide plenty of room for modifications by the technicians. Generally speaking, during normal production, having the automatic valve open at 30% is sufficient to meet the requirements, and you might consider installing a variable frequency drive. For air coolers that require the adjustment of their louvers at night, you can also use an inverter (with relatively low energy savings); the best option is to use a motor with high power output (several hundred kilowatts), as this is more practical.
In the following situations, it is recommended to add frequency conversion control for centrifugal pumps: 1. When the flow rate of the centrifugal pump is high and the motor power is relatively large, i.e., at least around 100 kW or more. If the motor has low power, the energy savings are limited, the economic benefits are poor, and it has no value for modification. 2. To meet production requirements, this centrifugal pump has a wide adjustment range in practical applications. If, to meet the requirements of the production plant, the centrifugal pump must operate at a relatively constant flow rate, then there is no need for any modifications.
Generally, it is the cases where flow rate needs to be controlled frequently or with high precision, such as in the feeding of towers. However, in order to improve the automation level of the installations, we use variable frequency drives wherever possible.
As for whether to choose a variable-frequency drive for pump systems, in my opinion, it is cost-effective to use variable-frequency control for pumps that do not require high outlet pressure (where such requirements are not strict) and that need to handle large flow rates. Pumps used for feeding reactants are typically equipped with fixed-frequency drives, as high pressure is required in these cases. On the other hand, product transfer pumps can benefit from variable-frequency control when the backpressure is low, after the discharge control valve is opened fully. I’m not sure if this understanding is correct; please ask an expert to correct me.
○Due to the requirements of the production process, the outlet flow varies significantly (with step-like changes)； ○The designed flow rate or head of the pump is much higher than what the actual installation requires, resulting in a smaller opening degree of the outlet control valve and higher energy consumption ； ○The operating conditions exhibit periodic and regular variations ； ○LPG pump. ——It's purely a personal opinion. If possible, take as many as you can; the results are quite good!
When the pump is operating under conditions of overpowered operation, it is necessary to add frequency conversion control to save energy!
Two pumps are used, one as the main pump and the other as a backup; one of them is equipped with variable frequency technology while the other isn’t. The choice depends on the circumstances, but generally using a pump with variable frequency technology helps save energy
The addition of variable frequency control to centrifugal pumps is mainly aimed at saving energy； For the feed to the tower, we use metering pumps (as the tower pressure is high and centrifugal pumps do not provide sufficient pressure); frequency conversion is employed, with the rough adjustment provided by the metering pump’s stroke complemented by the precise control offered by frequency conversion, in order to regulate the feed flow rate.
1. There is room for energy savings. Design institutes tend to choose conservative options; generally, the motors selected are of larger size, which leads to energy waste simply from controlling the outlet valve. In such cases, an inverter can be considered. The pump achieves the best energy-saving benefits when operating at 80%-90%. 2. The flow rate needs to be precisely and frequently controlled. 3. Modern industrial control systems generally employ fully automated control; frequency converters facilitate remote control and make operation easier. It also facilitates communication. 4. The frequency converter can be in a 1-to-2 or 1-to-multiple configuration. Save costs.
Generally, when it is necessary to control the flow rate of materials, an inverter needs to be added.
1. Save energy; 2. Control flow rate;
There is considerable uncertainty in the process flow rates; for instance, there can be significant changes in the amount of raw material processed, and the flow rates remain unstable. Take the decarburization process as an example – it is affected by large variations in the flow rates from upstream sources as well as by changes in the carbon content of those gases. As a result, fluctuations occur in the amount of acidic gases produced. In such cases, the acid gas compressors used downstream need to be designed with variable frequency capabilities in order to adapt to the conditions from upstream (this is just an example)
1. High pump power makes starting difficult； 2. Large fluctuations in traffic volume ； 3. Large pressure variations ； 4. Frequent start-stop operations ； 4. A good way to save energy.
Power consumption is high; using variable frequency can help reduce costs