A pump is a special mechanism for creating and controlling liquid flows in pipelines for various purposes. In order for the pump to work, it must be connected to the appropriate drive. Drives are divided into manual, mechanical, electric. The mechanism connected to the electric motor is an electric pump (the most common in both industrial and domestic areas).
Basic pump requirements
The operating mode of the pump must provide all the requirements for the network in which it is included. Most often, this is the “on-off” function (when filling or pumping out liquid in containers), maintaining the required pressure with an increase or decrease in consumption volumes, uninterrupted operation in circulation mode, emergency shutdown, connection of a backup pump. Compliance with these requirements is the key to cost-effective operation, extending the life of the equipment.
What does the automation system consist of
To control the operating modes, automation for pumps is being developed, whicheliminates human intervention in the operating mode. Typically, the control scheme provides for the transition to "manual mode" in the event of emergency situations (for example, the failure of any sensor that is part of the automation). As a rule, automation for pumps includes the following elements:
1. The pressure switch is an aneroid-membrane device that, when a certain pressure is reached, closes or opens the electrical control circuits.
2. Electrocontact manometers (EKM) with movable and fixed groups of el. contacts.
3. Float system (installed in filled containers) with el. contacts.
4. Pressure transducers with strain gauge bridges that change resistance to allow current to flow as system pressure changes.
5. Mechanical or electronic meters of the volume of consumed liquid, which issue a signal in the control circuit when the set volume is reached.
6. Frequency converters of the current supplying el. pump motor.
Elements 1, 2, 4, 5 are directly installed (cut) into the pipeline. Pump automation also includes:
- electromagnetic starters;
- email switching schemes for standby pumps;
- switching equipment for switching to "AUTO" or "MANUAL" mode;
- light fittings signaling normal operation, emergency shutdown, transfer to reserve, etc.;
- electronic protection equipment pump motors, control circuits.
The above equipmentmounted in pump control cabinets in accordance with the requirements of the PUE (Electrical Installation Rules).
Working principle
How does pump automation work? The most common mode is on-off pumps. For example: the reservoir (tank) is filled with liquid to the required level, while the float system closes (opens) the circuit of the coil of the electromagnetic starter, which turns on (turns off) the pump. The same happens when the float is lowered to a certain level. By the same principle, automation works from a pressure switch, el. contact manometer, counters of volume of the consumed liquid. To maintain the required pressure, the method of changing the frequency of rotation of the electric power is used. pump motor. This mode provides the frequency converter of the current feeding el. pump. The frequency of the transducer changes depending on the level of the signal from the pressure sensor. Continuity of liquid circulation in a closed circuit (this is mainly heating systems) is ensured by the presence of a backup pump, which is activated by an emergency transfer circuit when the main pump fails.
