The paper in the process of the turbine flowmeter measurement precision by the cause and the corresponding solutions

by:Kaidi Sensors     2020-07-19
Turbine flowmeter is a placed in the center of the measuring pipe through a supported by bearings on both ends of the turbine, when fluid flows through a pipe, turbine blades, on the turbine drive, make a turbine overcome fluid resistance torque and rotating friction torque. Within a certain flow range, for a certain amount of fluid viscosity, the rotation of the turbine angular velocity is proportional to the fluid velocity. As a result, the fluid velocity can be obtained through the rotation of the turbine angular velocity, to eventually achieve by calculation of fluid flow through a pipe. Because of the turbine flowmeter is more sensitive to the scene of the condition, the user shall be under the condition of the big meet meet its ideal requirements, so as to maintain the accuracy of the instrument leaving the factory, make ideal measurement data. When the temperature of the fluid medium pressure with a greater difference between reference condition, according to the material of sensor and temperature and pressure calculated the volume change of the sensor shell, provision of meter reading. When fluid under the working state of the viscosity of the fluid viscosity and calibration is large, to install and use the instructions provided on the viscosity of the modified curve parameter correction. And turbine flowmeter in the measurement of its upstream and downstream straight pipe length has certain requirements, should according to the installation requirements to meet, especially when the user requirements and high precision. Instrument shows the working medium under the condition of traffic volume, if you want to know what a standard or volume flow to mass flow and density compensation is needed. Is the accuracy of the turbine flowmeter in reference condition ( Or standard working conditions) Under certain, turbine flowmeter, the reference condition generally includes: the environmental conditions ( Environment temperature 15 ℃ ~ 35 ℃, relative humidity 45% ~ 75%, atmospheric pressure 86 kpa to 108 kpa, no electric field, magnetic field interference, no vibration) ; Power supply conditions, 220 v± 10% or 110 v, 50 hz & plusmn; 1, or 24 VDC) ; Fluid conditions ( When using fluid calibration, calibration pipe for industrial pipe, single-phase Newtonian fluid, fully filled tube, fully developed turbulent velocity distribution of axial symmetry, whirlpool, disturbance, steady flow. Calibration fluid is often water, oil, air, choose according to need. In the upstream and downstream of turbine flowmeter has enough long straight section. Fluid temperature is usually at room temperature, fluid pressure in usually 0. Below 25 mpa) 。 Obviously, actual work condition of turbine flowmeter are usually different from the reference condition, thus causes the accuracy of the turbine flowmeter to change. Turbine flowmeter in use process accuracy decreased, may be the following reasons: 1, the fluid in the fibrous or viscous impurities attached to the rotating part of the flowmeter, make rotational resistance increases, resulting in a decrease of instrument of the indicated value, the negative error, adverse to the fluid of the supplier. 2, fluid temperature, pressure changes may make the escape of air or liquid in the pipe due to the pressure inside the pipeline is lower than the saturated vapor pressure of fluid, make part of the liquid and steam, is also likely to make out with medium pressure air is sucked into the pipe, the gas with the measured liquid, caused its indication value increase, there is error, adverse to the fluid of the buyer. 3, usually have some impurities in medium, to produce the wear of bearing, axis, the gap between the two increases, moving parts of dynamic balance is destroyed, speed drops, or dirt into the gap, make motion resistance increases, speed down. All of these reasons resulting in a decrease of instrument display value, negative error, adverse to the fluid of the supplier. 4, poor working environment will be a larger influence on the measured results, such as electromagnetic interference, dust, high temperature, vibration, humidity, etc. , may cause a malfunction or failure of turbine flow sensor, the direct cause of turbine flowmeter, of error of error is positive or negative, may not be obvious, may complete failure. For the above phenomenon, the more serious when, can find problems from the comparison the working state of the process, easy to take corresponding measures. But, in the early part of the problem, don't take special measures can't found the problem. To sum up, embellish of instrument science and technology according to the principle of turbine flowmeter and site construction work experience for many years, suggest the user to compare smudgy fluid or is likely to produce gas liquid, the installation flow timing, can add filters or upstream of it gets over, gas collector, strengthen the routine maintenance, regular cleaning filters, eliminate getter, sundries in the gas or gas collector, to ensure the normal operation of the meter. At the beginning of the turbine flowmeter installation, upstream and downstream of the flow meter on the 2 times the diameter of the tube wall add a pair of pressure, need with differential pressure gauge is linked together, in the working status, indicating value of the flowmeter and the contrast between the differential gauge indicating value relationship, if everything is in order, then put the contrast relationship as the basis of later check whether the flowmeter work normally. Regularly measuring the contrast relationship and track record, if the same under the differential gauge indicating value of flowmeter slants small, indicating value is doubt to the flowmeter fault occurs. Check the flow sensor method can do so: first check transmission device. Method is to separate the letter issued by lifter, a known signal input, control the output value, can be found that the problem. If the fault cannot be ruled out short time, can change new one. If it is not the reason why it should be removed from the process line for the flowmeter, further examined, symptomatic treatment. In this paper by embellish instrument technology co. , LTD. Arrange release.
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