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The length of the straight pipe section of the flowmeter is not enough.

When installing the flowmeter, in order to obtain the same accuracy as the real-flow calibration, the specified flow conditions must be met. At present, in addition to a few types of volumetric, Coriolis mass flowmeters, there are specific requirements for the length of the straight pipe sections.

However, in actual engineering, due to site restrictions, there is no guarantee that the ideal installation location will ensure the length of the straight pipe section; in addition, in some renovation projects, the addition of the flowmeter to the existing pipeline will also encounter the problem of not having the proper length. At this time, engineers often use the following methods to solve the problem.

Concession
The so-called concession method is to make concessions on an indicator, which is commonly used in product quality management. For example, in chemical production, the products flowing out from the end of the process do not reach the first-grade product index, but can reach the second-level product index, so they are used for secondary product storage, instead of scrapping it, which is more economical. .

At the flowmeter use site, if the straight pipe length cannot meet the requirements anyway, the flow measurement results are not used for trade settlement, but for general monitoring or process control, and try to use the concession method.

Modified pipe
Simply put, the existing pipeline is modified by negotiating with the equipment specialists.

Add flow regulator
A flow regulator can be used to reduce the length of the upstream straight pipe section. Coordination experiments have shown that it can be used downstream of any upstream pipe.

Choose the right model
Due to the wide variation of the requirements of the straight pipe lengths of various types of flowmeters, if the original straight pipe section of the flowmeter is required to be long, and the requirements cannot be met anyway, the model with a lower length of the straight pipe section should be selected.

Evaluate the impact value
When the length of the straight pipe section is not enough, the uncertainty of the flowmeter increases because the velocity distribution in the pipe is distorted, so that the actual flow coefficient of the instrument is inconsistent with the flow coefficient of the factory standard. If the flowmeter with the front and rear pipe sections is assembled according to the actual pipe type and straight pipe length on the site, put it on the flow standard device, calibrate the flow coefficient of the instrument, and then use it together, and use this flow coefficient to calculate the flow rate. The effect of insufficient length of the straight pipe on the measurement results is completely ruled out.

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