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A sail switch, vane switch or flow switch is a mechanical switch that is actuated on or off in response to the flow or non-flow of a fluid such as air or water. [1] A sail switch typically operates through the use of a paddle or a diaphragm which gets displaced due to the force of fluid or air moving past it. Sail switches find application in ...
Direct digital control is the automated control of a condition or process by a digital device (computer). [ 1 ] [ 2 ] Direct digital control takes a centralized network-oriented approach. All instrumentation is gathered by various analog and digital converters which use the network to transport these signals to the central controller.
A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. [1] This enables the direct control of flow rate and the consequential control of process quantities such as pressure , temperature , and liquid level.
All mass flow controllers have an inlet port, an outlet port, a mass flow sensor and a proportional control valve. The MFC is fitted with a closed loop control system which is given an input signal by the operator (or an external circuit/computer) that it compares to the value from the mass flow sensor and adjusts the proportional valve ...
After the control of air flow and temperature was standardized, the use of electromechanical relays in ladder logic to switch dampers became standardized. Eventually, the relays became electronic switches, as transistors eventually could handle greater current loads. By 1985, pneumatic controls could no longer compete with this new technology ...
In a variable primary chilled-water system, the design flow rate is determined by the water flow velocity in the tube of the coils. At typical conditions, 6–7 feet per second (1.8–2.1 m/s) Maximum 12 ft/s (3.7 m/s) Minimum 1.5 ft/s (0.46 m/s) (based on a Reynolds number of 7500) Minimum flow is typically 50% or less of the design flow. [1]
Control valves are normally fitted with actuators and positioners. Pneumatically-actuated globe valves and diaphragm valves are widely used for control purposes in many industries, although quarter-turn types such as (modified) ball and butterfly valves are also used. Control valves can also work with hydraulic actuators (also known as ...
This opens the system to the possibility of also using chilled water to provide air conditioning. In homes, the water loop may be as simple as a single pipe that "loops" the flow through every radiator in a zone. In such a system, flow to the individual radiators cannot be modulated as all of the water is flowing through every radiator in the zone.