Electric / gas valve positioner gas consumption than the new structure, consumption if locator to determine the entire control valve air consumption, should adopt the structure of today's new locator, the instrument air consumption can be reduced to the original estimates of 1/2 can be.
Electric / gas valve positioner of various types of gas consumption
Pneumatic diaphragm control valve, cylinder valve or the executive organization in the world, if it is adjustable, also need to be matched with locator, thereby saving energy of electric / gas valve positioner gas consumption is to pay attention to a problem in design, because of the different consumption estimates that the capacity device instrument air compressor to determine the difference between, from the various locator sample, because the unit is not the same, not the same, difference is very big, can vary as much as 8 times from the surface, if the 100 valves, gas supply will vary greatly.
Consumption notation complete
Industrial automation instrumentation by the term "general terms", and air consumption is defined as, gas consumption: steady state, the maximum flow of gas consumed in the working range of the instrument. Therefore the complete consumption of representation, and the gas pressure, flow rate, output opening so that the relationship between both methods. Such as the Great Wall in Shanghai CCCX-4000 electric / gas valve positioner sample shows: single actuator, in 140kPa gas pressure, the output is 50%, the gas consumption (standard) 5L/min. In this paper.
It is understood, Zhejiang some factory had to control system operation with the orifice of the control valve air consumption test. (the following data without the user to verify, for reference only).
Locator consumption advantages and disadvantages of small
Energy saving
Control valve positioner gas consumption and gas consumption including actuator (cylinder) thin film gas consumption. Consumption of small locator must make the overall dynamics of control valve small consumption. Therefore in the stable operation of the system can make the gas supply to reduce, thereby saving energy. If there are 100 valves in the steady state (standard condition), each locator 1H internal volume is 1m3/h; the total gas consumption is 100m3/h, and each locator consumption is 0.5m3/h; is only 50m3/h; obviously saves the instrument air 50m3 in 1m3/h.
Instrument structure requires high
Consumption of small locator, structure and machining accuracy of the positioner of the requirements of high. This is a locator in the manufacture of some, but rather let reason consumption bigger in order to ensure the instrument performance.
Locator consumption to be small but to ensure that the valve action
Valve movement speed, depending on many factors. PA locator ability is a crucial factor in valve movement speed. If the locator gas consumption is too small, should consider the impact of valve movement speed. Especially the big valve movement speed.
The valve positioner of various structures have a suitable gas consumption
From the current investigation to see, all kinds of electric / gas valve positioner of the gas consumption are related to structure. The gas consumption trend is not more and more small, but a suitable air consumption. From table 1 shows the standard conditions, Fisher DVC500 gas consumption is 300L/h, and to the development of DVC600 type gas consumption for 600L/h, Neles for 800L/h ND800 gas consumption, and to the development of ND-900 type gas consumption for 400L/h.
Control valve air consumption to consider the dynamic consumption
When the control valve stability in an opening, only locator gas consumption, the consumption need only consider the consumption of positioner. When the control valve of the opening changes, the valve stem up and down movement, the diaphragm moves up and down, make indoor air from the film, the size and the frequent action of this part of the exhaust gas dynamic depends on the valve, and with the size of thin film head, regardless of the use of any locator, this part of the film the first air consumption is always the same. Therefore, the control valve air consumption is equal to the executing agency locator consumption + gas consumption. Especially in the open parking, and large fluctuations in the system, the valve action is large and frequent, the film to the intake / discharge, large enough to consider the valve for gas, not because of consumption of small locator and the entire control valve air consumption estimated too small.
From the author's investigation, under standard conditions, the film type control valve can be used for the following considerations: the domestic control valve for each gas consumption by 1m3/h estimation can be; but with the change of inlet valve positioner structure, many valve positioner in the steady-state air consumption is much lower than the 1m3 /h, but due to consumption of air valve is positioner and films (cylinder) in gas consumption and both, the user can press 0.5 ~ 1m3/h estimation, and according to the gas consumption amount of the same device in a different valve positioner calculation. The following calculation instrument air supply device capacity (design code for instrument air supply system HG/T20510-2000).
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