The design of a pressure regulator can be of two fundamentally different types - direct and indirect acting regulators.
Indirect acting pressure regulators use an external source of energy to change the flow area of the valve. The measuring element consists of two pressure sensors that transmit a signal to the controller, and the controller generates a control signal for the regulating valve. The complex design and high price of indirect acting regulators have made them rarely used, despite their high accuracy in maintaining pressure differences. These regulators can be assembled based on any control valve, practically any pressure sensor and controller.
Direct acting pressure regulators - the measuring element affects the regulating element without additional sources of energy, using the energy of the working environment. These are proportional regulators in which the opening of the valve corresponds to the deviation of the controlled variable, and the opening speed corresponds to the rate of change of the pressure difference.
The design of a direct acting pressure regulator must include a setpoint, two impulse lines, measuring and regulating elements. Depending on the type of regulator, the measuring element may be a membrane, bellows or piston, and the setpoint may be a spring, pneumatic or lever-loading mechanism. The impulse line can be integrated into the valve body or connected to the pipeline using an impulse tube.
The pressure regulator valve can be pressure relief or non-relief, single or double seated, connected to the pipeline by thread, flanges or weld-on nipples.
Of the many designs of pressure regulators for water, devices with a single-seat valve, spring setpoint and membrane measuring element are used. Such devices are called membrane regulators - they maintain pressure differences with high accuracy, are reliable in operation and repairable, although they have a slightly higher cost compared to spring regulators.
Spring pressure regulators are devices with a single-seat valve, spring setpoint, and the valve disc as the measuring element. The cost of a spring regulator is lower than that of a similar membrane device, the construction is simpler, and the pressure maintenance accuracy is lower.
Some types of bypass valves can be considered spring analogs of membrane pressure regulators that open when the pressure difference increases relative to the setpoint. There are no spring analogs for membrane regulators that close when the pressure difference increases relative to the setpoint.
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