flowmeter selection principle
Published on：2015-5-5 19:25:37 Hits：
Flowmeter selection is in accordance with production requirements, from a practical instrument supply point of view, a comprehensive measure of security consideration, accurate and economy, and to identify ways and means flow sampling measuring instruments according to the nature and the flow of fluid to be measured The types and specifications.
Safe and reliable flow measurement, the first measurement method is reliable, that the sampling device does not occur in the operation of mechanical or electrical circuit fault caused by an accident; the second is measuring instruments in terms of the production or breakdown under normal circumstances cause safety impact on production systems . For example, high temperature and pressure measuring power plant main steam flow, which is installed in the pipeline in the first measuring element must be strong in order to ensure high-speed steam flow erosion damage without generating mechanism. Thus, generally preferred standard throttling device without selection Izod double flared tube or other non-standard plug-meter speed measuring devices, and low structural strength of the target type, turbine flow meter. Fuel power plants and flammable gases occasions, should be used in explosion-proof type instrument.
To ensure the safe operation of the instrument on the basis of, and strive to improve the instrument accuracy and energy efficiency. For this reason, not only to choose to meet the accuracy requirements of display instruments, but also to choose the right way to measure the characteristics of the measured medium. Main steam flow measurement in power plants, because of its crucial economic power plant safety and, generally use mature standard with a differential pressure flow restrictor installed capacity, chemical treatment of sewage and dirty fuel flow and low, respectively, belong to Renault Number of viscous flow, do not apply a standard orifice. Dirty stream generally used for round orifice other non-standard orifice with differential pressure gauges or ultrasonic Doppler flow meter, and viscous flow positive displacement, respectively, of the target type or wedge flow meter. Population water turbine, condenser circulating water and heat recovery unit heat recovery steam are all large-diameter (400mm or more) flow measurement parameters, due to manufacturing difficulties and create pressure loss, generally do not choose standard throttling device. According to the measured medium special items and measurement accuracy requirements, respectively insertion flow, velocity components with differential pressure gauge, ultrasonic flowmeter, or the use of labeling, simulation and other incompetent loss measured way traffic.
To ensure the accuracy of the meter life and, also pay attention to the anti-vibration instrument selection requirements. In the humid heat meter area you want to select.
The correct choice of instrument specifications, but also to ensure that an important part of life and the accuracy of the instrument. Special attention should be static pressure and temperature options. That is the extent of hydrostatic pressure of the instrument, it should be slightly larger than the working pressure of the measured medium, and generally 1.25 times, to ensure that does not leak or accident. Scale range of choice, mainly meter scale upper limit choice. Choose small, easy to overload, damage to the instrument; large selection, hinder the measurement accuracy. Usually preferably 1.2 to 1.3 times the actual operation of a maximum flow rate value.
Mounted on a long-running production tubing contact instrument, it should also consider the energy loss caused by the flow measuring element. In general, the same should not be selected in the production tubing pressure loss larger plurality of measuring elements, such as throttle element or the like.
In short, there is no way of measuring or meter the flow of various fluids and can adapt. Different measurement methods and structures require different measurement operation, use and conditions of use. Each type has its unique advantages and disadvantages. Therefore, it should be based on a variety of measuring methods and instruments for the full comparison of characteristics suitable for production requirements on select both quiet and reliable, durable and economical best type.
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