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Overview / Design Principle:
This recorder is an accurate, sensitive pneumatic controller used in conjunction with an air-operated valve for control of steam, gas or fuel for combustion equipment or to operate other pneumatic devices. Requires approximately 16 psi input, air output is 3 to 15 psi, throttling span is 5% to 25% of scale range. Flush or wall mounted (brackets supplied) with 12 optional ranges from -30°F to 1100°F.
Operation:
Operates in an adjustable throttling range of 5-25% of scale range. As the indicating pointer, moving up or down scale in response to the expansion or contraction in the thermal sensing element, enters the throttling range and approches set point, it changes the effective orifice in the instrument's bleed valve.
Depending upon its control action (reverse or direct acting) this increases or decreases the pressure delivered to the remotely-placed air operated control device.
Pressure transmitted by the control instrument is reflected by teh valve postition of the air-operated device which modulates the flow of heating or cooling medium.
Load error, inherent in throttling controls, is compensated by manual reset adjustment. Note: For long air line feeds, ie. 10 feet or greater, or large volume air valves or control devices, an air pressure booster relay is strongly recommended. |