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Determination of Gas Consumption for Low Gas Consumers and Control Valves
Abstract: The new structure of electric / gas valve positioner air consumption is small, if the locator air consumption to determine the air consumption of the entire control valve should be used today's new structure of the locator, the instrument air consumption can be as low as the original estimate 1/2 can be. Dynamic gas consumption; Instrument air source device capacity 1 Each type of electric / gas valve positioner Air consumption Pneumatic membrane control valve, cylinder valve or the current world's major implementation Institutions, if it is regulatory, but also with the locator, so electric / gas valve positioner air consumption is a design of energy-saving issues, because different air quality estimates make the device air compressor capacity difference between the great disparity , From a variety of locator samples, due to different units, the state is not the same, very different, from the surface will be a difference of 8 times, if 100 valves, the gas supply will vary greatly. A complete representation of gas consumption According to the terminology "common terminology" for industrial automation instruments, the gas consumption is defined as the gas consumption: the maximum flow of gas consumed by the instrument in the working range at steady state. Therefore, a complete representation of gas consumption, and the supply pressure, flow, output opening, said the methods are related. Such as the Shanghai Great Wall CCCX-4000 electric / gas valve positioner sample shows: single-acting actuator, 140kPa air supply pressure, the output is 50%, air consumption (standard conditions) 5L / min. It is understood that a plant in Zhejiang had on-site operation of the control system with orifice plate on the control valve air consumption test (the following data without verification by the user, for reference only), as shown in Table 2 2 locator air consumption advantages and disadvantages of small 2.1 Energy-saving control valve air consumption, including the locator air consumption and the actuator diaphragm (cylinder) air consumption. Locator air consumption is bound to make the total control valve dynamic air consumption small. Therefore, the steady operation of the system can reduce the supply of gas to save energy. If there are 100 valves in steady state (standard condition), each locator air consumption within 1h 1m3 / h; total air consumption of 100m3 / h, and each locator air consumption of 0.5m3 / h; then only With 50m3 / h; 1m3 / h obviously save instrument air 50m3. 2.2 instrument structure requires a high locator air consumption is small, the structure of the locator and machining accuracy requirements. This is why some of the positioners are designed to make air consumption a little larger for manufacturing performance. 2.3 locator air consumption is small but to ensure that the valve action valve speed, depending on many factors. The ability of the positioner's power amplifier is a determinant of how fast the valve can move. If the retainer air consumption is too small, we must consider whether the impact of valve speed. Especially the action speed of big valve. 3 various structures of the valve positioner has a suitable air consumption From the current survey, a variety of electric / air valve positioner air consumption are related to the structure. The trend is not less and less gas consumption, but rather a suitable air consumption. As can be seen from Table 1, the Fisher DVC500 air consumption is 300L / h, while the DVC600 air consumption is 600L / h and the Neles ND800 air consumption is 800L / h. However, the air consumption of ND-900 is 400L / h. 4 control valve air consumption to consider the dynamic air consumption control valve structure shown in Figure 1, when the control valve steady-state at a certain opening, only the locator gas consumption, the gas consumption only need to consider the locator air consumption. When the control valve movement and opening change, the valve stem up and down movement, the film up and down action, the film room air discharge, this part of the dynamic discharge depends on the valve size and frequency of movement, and the size of the film head, no matter With any positioner, this part of the head of the air consumption is always the same. Therefore, the control valve air consumption is equal to the air consumption of the positioner + actuator air consumption. Especially in the open parking and system fluctuations, the valve action is large and frequent, the film to the intake / deflation, to consider the valve is large enough gas, not because of the locator air consumption is small and the entire control valve air consumption is estimated Too small. From the author's survey, the standard conditions, the film-type control valve can generally be considered as follows: The original domestic control valve each gas consumption by 1m3 / h can be estimated; but with the changes in the structure of the imported valve positioners, not Less valve positioner gas consumption at steady state is much lower than 1m3 / h, but because of the valve air consumption is the locator and film (cylinder) of the air consumption of both, the user can be 0.5 ~ 1m3 / h estimate, And the same device for different valve positioner gas consumption calculation.