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What are the metrological requirements for mine ultrasonic flowmeters? --1--3--8--5--3--7--2--6--8--9--4--
Mine ultrasonic flowmeters are primarily used in Class I explosion-proof environments, such as coal mines and coal preparation plants. They come with complete coal safety certificates and explosion-proof certifications, are easy to install, and simple to maintain. What are the metrological performance requirements for these flowmeters during use?
Generally, we verify them from the following aspects:
1. Accuracy Class
Recommended accuracy class series. If a non-listed accuracy class is used, its maximum permissible error must comply with the corresponding principles in Table 1 and be clearly stated in the flowmeter product manual and on the nameplate. Within the flow range of q1 ≤ q ≤ qmax, the maximum permissible error of the flowmeter should conform to the specifications in Table 1. In the flow range of qmin < q < q1, the maximum permissible error should not exceed twice the maximum permissible error specified in Table 1. Additionally, for gas flowmeters, the flow velocity corresponding to q1 should not exceed 3 m/s; for liquid flowmeters, the flow velocity corresponding to q1 should not exceed 0.3 m/s.
2. Repeatability
The repeatability of the ultrasonic flowmeter must not exceed one-fifth of the absolute value of the maximum permissible error specified for the corresponding accuracy class.
3. Flowmeter Coefficient Adjustment
If the flowmeter coefficient is changed during verification, the previous flowmeter coefficient, the adjusted flowmeter coefficient, and the amount of adjustment should be indicated on the verification certificate.
4. Requirements for Bidirectional Flowmeters
Bidirectional flowmeters should be verified separately for both measurement directions.
5. Requirements for Clamp-On Flowmeters
Clamp-on flowmeters should be verified for all transducers, preferably on a pipe diameter identical to the one used in practice. If the ratio of the usage pipe diameter to the verification pipe diameter is greater than 2 or less than 1/2, an additional error of 0.5% should be applied when using the flowmeter.
Due to differences in product batches and models, specific product details and prices, please call for consultation.