Gas waist wheel flowmeter selection and installation
2021-05-15
1. Selection of gas waist flow meter
a. The choice of gas waist flow meter should consider the following three aspects: the type of flow meter, the performance of the flow meter, and the supporting equipment of the flow meter.
b. The selection of the type of gas waist flowmeter should be based on the actual working conditions and the characteristics of the measured medium.
c. The following five elements should be considered in the performance selection of the waist gas flowmeter
(1) Flow range; The flow range of the gas waist flowmeter is related to the applicable characteristics (continuous or intermittent work), measurement accuracy and other factors. The same waist wheel gas flowmeter, when used for intermittent measurement, has a large flow range (mainly, the upper limit flow can be larger than that of continuous work); For measurement accuracy, the flow range is larger when used for low accuracy measurement, while the flow range is smaller when used for high accuracy measurement.
In order to maintain the good performance and long service life of the instrument, the working flow rate during use is best selected not to exceed 70% to 80% of the maximum flow rate of the instrument.
(2) Measurement accuracy; Waist wheel gas flowmeter is one of the most accurate flowmeters at present. The measurement accuracy given by the manufacturer on the product sample refers to the basic error obtained under the laboratory reference conditions, while in actual use, due to the deviation of the field conditions, additional errors will inevitably be brought, and the actual error is the synthesis of basic errors and additional errors. Therefore, measures should be taken according to the problems that may occur on site when the instrument is selected.
The viscosity and temperature of the measured medium are the main factors that influence the measurement accuracy.
(3) Pressure resistance (working pressure); The working pressure of the flow meter should be borne by the working shell of the flow meter, and the different requirements of the working pressure should be made of different materials, so as not to cause unsafe use. The maximum housing pressure grade of conventional products can reach 1.0Mpa pressure.
(4) pressure loss; Pressure loss is also an important issue that must be considered when choosing flow timing. Especially when large flow is used, more attention should be paid to whether the pressure loss of the flow meter can meet the user's use requirements.
(5) the purpose of application; The purpose of use refers to whether the flow meter is used for trade settlement and cost accounting, or for process parameter control. The flowmeter used to calculate the measurement mainly considers whether its measurement accuracy meets the requirements of accounting, and according to user requirements should be selected with a volume correction instrument, IC card controller, various signal output interface, historical database and other supporting equipment and functions.
2. Installation of gas waist flow meter
a. Environmental conditions: no corrosive gas around, small mechanical vibration, less dust and away from heat sources. For intelligent flowmeters equipped with volume correctors, there should also be an electromagnetic environment that meets the requirements.
b. Ambient temperature: generally not more than -20℃~+80℃ range.
c. Pipeline conditions: Before installing the flow meter, the pipeline must be cleaned and purged to clear all debris, rust and dirt. The continuous pipeline should generally be coaxial with the inlet and outlet of the flow meter, and there should be no protruding objects protruding from the pipe wall into the pipeline. The flow meter should be stress-free installation, taking full account of the pipeline stress caused by the operating temperature.
The flow control valve, on-off valve and bypass valve installed in the flow pipeline should work reliably, for example, if there is any leakage of the bypass valve, it will cause a serious decline in the measurement accuracy. In order to facilitate observation and inspection, the cutting off of the bypass pipeline can be composed of two on-off valves in series, and a small diameter leak detection valve is set on the connecting short pipe between the two valves, which can conveniently check the cutting off of the bypass valve. As required, a suitable temperature measuring instrument and a pressure measuring instrument are installed near the inlet of the flow meter in order to determine the temperature and pressure of the gas being measured.
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