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| De-superheater |
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A device for removing the excess heat in steam as its pressure is reduced.
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| De-vent |
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To close the vent connection of a pressure control valve permitting the valve to function at its adjusted pressure setting.
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| Deadband |
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The region or band of no response where an error signal will not cause a corresponding actuation of the controlled variable.
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| Decompression |
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The slow release of confined fluid to gradually reduce pressure on the fluid.
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| Delta |
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The amount of change in a number, size or position.
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| Density |
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As usually applied to wood of normal cellular form, density is the mass of wood substance enclosed within the boundary surfaces of a wood-plus-voids complex having unit volume. It is variously expressed as pounds per cubic foot, kilograms per cubic metre, or grams per cubic centimetre at a specified moisture content.
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| Differential current |
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The algebraic summation of the current in the torque motor; measured in MA (milliamperes).
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| Differential cylinder |
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Any cylinder in which the two opposed piston areas are not equal.
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| Diffusion |
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Movement of moisture from areas of high to low concentration or temperature.
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| Digester |
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An airtight vessel or enclosure in which bacteria decomposes biomass in water to produce biogas.
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| Directional valve |
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A valve which selectively directs or prevents fluid flow to desired channels.
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| Displacement |
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The quantity of fluid which can pass through a pump, motor or cylinder in a single revolution or stroke.
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| Dither |
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A low amplitude, relatively high frequency periodic electrical signal, sometimes superimposed on the servo valve input to improve system resolution. Dither is expressed by the dither frequency (Hz) and the peak-to-peak dither current amplitude (ma).
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| Double sheave |
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A pulley block with two grooved wheels.
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| Downdraft gasifier |
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A gasifier in which the product gases pass through a combustion zone at the bottom of the gasifier.
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| Drain |
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A passage in, or a line from, a hydraulic component which returns leakage fluid independently to reservoir or to a vented manifold.
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| Drive pulley |
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The first of a train of wheels, giving motion to the rest.
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