Turbine flow meter manufacturers Xiyuan instrument technical guidance for instrument selection and use
Turbine flowmeter introduction:
is a speed type flow meter. Because of its advantages such as high measurement accuracy, fast response speed, wide measurement range, low price, convenient installation, etc., it is widely used in chemical production.
Turbine flow meters are widely used in the following measurement objects: petroleum, organic liquids, inorganic liquids, liquefied gas, natural gas, coal gas and low temperature fluids. Turbine flowmeter consists of turbine, bearing, preamplifier and display instrument. The working principle of the turbine transmitter is that when the fluid flows along the axis of the pipeline and impacts the turbine blades, a force proportional to the product of the flow rate qv, the velocity V and the fluid density r acts on the blades, pushing the turbine to rotate. While the turbine is rotating, the blade periodically cuts the magnetic lines of force generated by the electromagnet, changing the magnetic flux of the coil. According to the principle of electromagnetic induction, a pulsating potential signal will be induced in the coil (the frequency of this pulsating signal is proportional to the flow rate of the measured fluid). The pulse signal output by the turbine transmitter is amplified by the pre-amplifier and sent to the display instrument to realize the flow measurement.
Selection points of liquid turbine flowmeter:
In the selection and use of chemical equipment, attention should be paid to: the body of the flowmeter should be made of 316 stainless steel to prevent corrosion; care should be taken to ensure that the measured medium cannot corrode the turbine, especially the bearings, otherwise measures should be taken. Priority should be given to the place where the bearing uses PTFE, carbon graphite materials before installing the turbine flowmeter. The pipeline must be cleaned. When the measured medium is not clean, add a filter. Otherwise, the turbine and bearing are liable to get stuck and the flow cannot be measured . The transmitter should be installed horizontally, avoid vertical installation, and ensure that there are adaptable straight pipe sections at the front and back, generally the first 10D and the rear 5D. The turbine flowmeter is mainly selected for its high degree, but it should be noted that the higher the flowmeter, the more sensitive it is to changes in field conditions. Therefore, when installing the turbine flowmeter, the front and rear pipe flanges must be level. Otherwise, the pipeline stress will have a great impact on the flowmeter. The installation of the sensor should be convenient for maintenance and avoid places with pipeline vibration, strong electromagnetic interference and resistance to radiation.
The selection of gas turbine flowmeter should be considered from the following aspects:
(1) Density of gas: The effect on the gas turbine flowmeter and the physical properties of the fluid is mainly the density of the gas. It has a great influence on the meter coefficient, and it is mainly in the low flow area. If the gas density changes frequently, corrective measures should be taken for the flow coefficient of the flowmeter.
(2) Flow range: The choice of the flow range of the turbine flowmeter has a greater impact on its degree and service life, and each type of flowmeter has a certain measurement range. The selection of the flowmeter diameter is also determined by the flow rate. The scope is determined. For intermittent working occasions where the actual running time of the instrument does not exceed 8 hours per day, select 1.3 times the maximum flow rate in actual use as the upper limit of the flow range; for continuous working occasions where the actual operating time of the meter is not less than 8 hours , Choose 1.4 times the maximum flow in actual use as the upper limit of the flow range. The lower limit flow of the meter is 0.8 times of the actual minimum flow rate.
(3) Pressure loss: Try to choose a turbine flowmeter with a small pressure loss. (4) *** Degree level: It is not the higher the better, it is important to choose the right one according to the actual situation! Generally speaking, the choice of turbine flowmeter is mainly for its high degree. However, the higher the accuracy of the flowmeter, the more sensitive it is to changes in the field conditions. Therefore, the choice of the instrument's accuracy must be considered carefully and economically. For trade settlement instruments of large caliber gas pipelines, it is cost-effective to invest more in instruments. For occasions with a small amount of conveyance, a medium precision level can be used.
(5) Structure type:
· Internal structure should choose reverse thrust turbine flowmeter. Because the reverse push structure can make the impeller float in a certain flow range, there is no contact point in the axial direction, there is no end face friction and wear, and the service life of the bearing can be extended.
· Selection according to the pipeline connection method. There are two types of horizontal and vertical installation of the flowmeter. The flange connection, screw connection and clamp connection are available for horizontal installation and pipeline connection. Medium diameter is selected by flange connection; small diameter and high pressure pipe are selected by screw connection: clamping connection is only suitable for low pressure medium and small pipe diameter; vertical installation is only threaded connection.
· Select according to environmental conditions, taking into account the effects of temperature and humidity. Natural gas measurement should choose intrinsically safe explosion-proof turbine flowmeter.
(6) Bearings: The bearings of turbine flowmeters are generally made of tungsten carbide, polytetrafluoroethylene and carbon graphite. Natural gas metering instrument bearings should use tungsten carbide materials.