The correct selection of ultrasonic flowmeters can ensure better use of ultrasonic flowmeters. The type of ultrasonic flowmeter to be selected should be determined according to the physical properties and chemical properties of the fluid medium to be tested, so that the diameter, flow range, lining material, electrode material and output current of the ultrasonic flowmeter can be adapted to the properties of the fluid to be measured. And flow measurement requirements.
1, precision function check
Accuracy levels and functions are based on measurement requirements and usage scenarios to select instrument accuracy levels for cost-effectiveness. For example, in the case of trade settlement, product handover and energy measurement, the accuracy level should be higher, such as 1.0, 0.5, or higher; for process control, select different accuracy levels according to control requirements; It is to detect the process flow, no need to do precise control and measurement, you can choose a lower accuracy level, such as 1.5, 2.5, or even 4.0, then you can use a low-cost plug-in ultrasonic flowmeter.
2, measurable medium
Measuring medium flow rate, meter range and caliber When measuring a general medium, the full flow rate of the ultrasonic flow meter can be selected within the range of 0.5-12 m/s of the measured medium flow rate, and the range is relatively wide. The selection of the meter specification (caliber) is not necessarily the same as the process piping. It should be determined according to whether the measured flow range is within the flow rate range. That is, when the pipeline flow rate is too low to meet the requirements of the flow meter or the measurement accuracy is not guaranteed at this flow rate. It is necessary to reduce the gauge diameter, thereby increasing the flow rate inside the tube and obtaining satisfactory measurement results.
First, the gas turbine flowmeter installation requirements
1. When the gas flowmeter is installed, it is strictly forbidden to directly conduct electric welding at the inlet and outlet flanges to avoid burning the internal parts of the flowmeter;
2. For the newly installed or overhauled pipeline, it must be purged to remove the debris in the pipeline before installing the flowmeter;
3. The gas turbine flowmeter should be installed in a place that is easy to maintain, has no strong electromagnetic field interference, no mechanical vibration and thermal radiation;
4. Gas turbine flowmeters should not be used in places where flow is frequently interrupted and there is strong pulsating flow or pressure pulsation;
5, the gas turbine flowmeter should ensure that the pipeline is coaxial, and prevent the gasket from protruding into the pipeline, otherwise it will disturb the flow profile;
6. The flow direction of the gas turbine flowmeter should be consistent with the direction marked on the casing. The upper and lower pipelines of the flowmeter should be guaranteed with 2DN and 1DN straight pipe sections;
7. When using external power supply, the flowmeter must have reliable grounding, but it should not share the grounding wire with the high-power system; when the pipeline is installed or repaired, the grounding wire of the welding system should not be overlapped with the flowmeter.
8. Since the flowmeter needs to be repaired and calibrated, in order to ensure normal gas supply, bypass piping should be set. The bypass pipe valve must be closed during normal use;
9. When constructing pipelines, it is advisable to install telescopic tubes or bellows to avoid serious stretching and causing breakage of the flowmeter;
10. When the gas turbine flowmeter is installed outdoors, the upper part should be covered to prevent the rainwater from immersing and the sun exposure affecting the service life of the flowmeter;
11. When installing the gas turbine flowmeter, it is advisable to add a filter to the flowmeter (filtering accuracy is recommended ≤20μm).
Second, gas turbine flowmeter requirements
1. When the gas turbine flowmeter is put into operation, the upstream valve of the flowmeter should be slowly opened (not less than 15 seconds), and then the downstream valve of the flowmeter should be slowly opened to prevent the instantaneous airflow from rushing to the turbine;
2. When the flowmeter needs to have a long-distance signal, it should be connected to the external power supply (+12~+24VDC) strictly according to the electrical performance index of the gas turbine flowmeter. It is strictly forbidden to directly connect 220VAC (or 380VAC) power supply at the signal output.
In the case of small flow metering, the film surface ratio is the largest, the Roots flowmeter is second, and the turbine flowmeter is the smallest. The initial flow performance of the volumetric flowmeter should be superior to the velocity flowmeter. For industrial and commercial users with large total gas consumption and low heat load for each gas, the volumetric flowmeter, ie, the membrane meter and the Roots flowmeter, should be preferred to meet the flowmeter requirements of a single burner when used alone. It can also meet the measurement requirements of the maximum flow rate when all burners are used at the same time.
Not all industrial and commercial users can solve the measurement problem by selecting a volumetric flowmeter with a larger range. The volumetric ratio of the volumetric flowmeter is limited, and it is impossible to increase without limit. The selection of the flowmeter cannot be solved. This kind of user has a measurement problem. When the user only uses a single device for gas, or when operating at low flow rate, the initial flow rate and minimum flow rate of a single flow meter may not meet the minimum flow rate requirement. A single large flow meter cannot measure low gas consumption, which will result in Large supply and marketing differences.