Currently, gas meters widely used in gas projects include skin membrane meters, turbine flow meters, orifice flow meters, vortex flow meters, and precession vortex flow meters, which are suitable for different users. A reasonable choice should be based on the user's gas pressure, usage, maximum and minimum flow parameters and installation environment. The author discusses the application and management of gas turbine flowmeters. 1 How Turbine Transmitters Work Turbine flowmeters consist of turbines, bearings, preamplifiers, and display meters, as shown in Figure 1. The working principle of the turbine transmitter is: when the fluid flows along the axis of the pipeline. When impacting the turbine blade, a force proportional to the product of the flow qv, the flow velocity v, and the fluid density p acts on the blade to promote rotation of the turbine. While the turbine is rotating, the blades periodically cut the magnetic lines of force generated by the electromagnets and change the magnetic flux of the coils. According to the principle of electromagnetic induction, a pulsating potential signal will be induced in the coil. The frequency of the pulsation signal is proportional to the flow rate of the fluid to be measured. N=Q· ξ Which, ξ is a flow coefficient. The pulse signal output by the turbine transmitter is amplified by the preamplifier and sent to the display meter, so that the flow rate can be measured. 2 Turbine Flow Meter Applications and Selection Gas flow meter selection can be compared in five ways: (1) Instrument performance: accuracy, range, pressure loss, upper and lower limit flow, signal output characteristics, response time, etc.; The turbine flowmeter is the second statutory gas flowmeter after the orifice flowmeter. The measurement objects to be solved by the urban gas flowmeter are roughly medium pressure (below 1.6MPa), medium and small flow (below DN200), and poor installation conditions ( Insufficient length of straight pipe section, weak management and maintenance capabilities, simple and easy-to-understand functions, easy operation, maintenance-free, and moderate price. When selecting a turbine flow meter, consider the following points: (1) The flow meter body is preferably made of 316 stainless steel for corrosion protection. If it is an explosion-proof zone, it must also be explosion-proof. 3 Turbine Flowmeter Installation Turbine flowmeter installation shown in Figure 2. (1) Before installing the turbine flow meter, clean the piping. When the measured media is not clean. Pipes should be added upstream of the pipeline, otherwise turbines and bearings could easily get stuck and flow could not be measured. 4 turbine flowmeter configuration and calibration, display instrumentation Turbine flowmeter configuration and calibration, the standard calibration method is the 10-point calibration method, the viscosity is different, the calibration value is different, so the viscosity calibration curve is usually done. The task of the display meter is to convert the number of output pulses per unit time and the total number of output pulses to instantaneous flow and total flow, and display them. The pulse signal output by the pre-amplifier is irregular in amplitude and waveform after entering the display instrument. First, it needs to be shaped into a regular rectangular electric pulse signal with a certain amplitude through a shaping circuit, and then through a frequency/current conversion circuit, the frequency signal becomes a corresponding current signal (4mA~20mA), and then converted into an instantaneous flow value, The total amount is obtained from the conversion and integration circuits. Some display instruments are displayed locally, and some send DCS displays. 5 Turbine flow meter management Meters are the basis for trade settlement between supply and demand parties, and they are also the main technical indicators for gas efficiency in the production sector. For gas companies, the control of poor gas supply and sales is the focus of management. The main factors causing poor supply and sales are: subjective user equipment configuration, meter reading, failure table replacement time and other factors, objectively, there are gas meter quality, user stealing and other factors. Effectively controlling the above factors can reduce the difference between supply and sales. Turbine meter usage management should be considered from the following aspects: (1) Do a good job in the design, selection and on-site survey of the meter. The design strictly complies with the power of attorney to provide the meter data flow range of the equipment data to ensure the measurement accuracy. The instrument performance quality and the characteristics of the measurement object must be accurately understood. The failure of many types of selection is due to inaccurate parameters. Before the ventilation, confirm on-site use of the gas equipment. If there is any discrepancy, ensure that the meter is replaced before ventilation. Window Screening,Aluminium Alloy Window Screen,Galvanized Window Screen,Window Screen tengyuan wire mesh , https://www.tengyuansiwang.com
(2) Fluid properties: fluid pressure, temperature, density, viscosity, chemical properties, wear, corrosion, scaling, fouling, gas compression coefficient, isentropic index, specific heat capacity, conductivity, sound velocity, miscible flow, pulsating flow, etc. ;
(3) Installation conditions: pipeline layout direction, flow direction, length of upstream and downstream pipelines, pipe diameter, maintenance space, pipeline vibration, grounding, power supply, auxiliary equipment (filtering, sewage discharge), explosion-proof, etc.;
(4) Environmental conditions: temperature, humidity, safety, electromagnetic interference, etc.;
(5) Economic factors: purchase costs, installation costs, maintenance fees, calibration fees, service life, operating costs (energy consumption), spare parts, etc.
(2) Bearings are generally available in three sizes: carbonized tungsten, PTFE, and carbon graphite. Tungsten carbide has the highest accuracy and can be used in gas projects; PTFE and carbon graphite can be preserved, and is generally preferred in chemical plants.
(3) The sensing probe detects the movement of the rotating body and converts it into a pulsed digital electrical signal. The output voltage of the electromagnetic coil is close to a sinusoidal curve. The frequency range of the pulse signal varies linearly with the measured flow rate. The typical range is 10: 1, 25:1 and 100:1 three specifications. The electromagnetic coil's resistance is generally less than 2000 Ω . 
(2) The power cable of the transmitter adopts metal shielded Wire and the grounding should be good and reliable. The power supply is DC 24V, 650 Ω impedance.
(3) The transmitter should be installed horizontally to avoid vertical installation, and to ensure that there is an adaptive straight section before and after it, generally 10D before and after 5D.
(4) Ensure that the flow direction of the fluid is the same as the direction of the arrow of the instrument housing and must not be reversed.
(5) The measured medium cannot have a corrosive effect on the turbine, especially the bearing, otherwise measures should be taken.
(6) Set the meter factor before commissioning. Carefully check to make sure that the instrument wiring is correct and the grounding is good before sending power.
(7) When installing the turbine flowmeter, the front and rear duct flanges should be horizontal, otherwise the pipeline stress has a great influence on the flowmeter.
(8) When attaching or detaching the flowmeter, be careful not to collide with the magnetic sensor.
(2) Improve technology and improve measurement management. A highly efficient rectifying rectifier and turbine flow sensor are coupled to form an integrated gas turbine flow juice. Only a 2D straight pipe length is required for the city when the upstream side choke is used as an elbow or a half-opening cutoff valve. The installation space is narrow, it has a very prominent feature.
(3) Strictly check the quality of the first inspection of the gas meter, and regularly carry out the inspection and verification of the meter. The gas turbine meter should be a meter that is qualified for the first inspection, a limited period of use, and an expired replacement. The first verification must pass the quality. Send someone to read and maintain the data on a regular basis and regularly conduct inspections and verifications.