“Small in and out” is a common language used by the power meter industry in the instrument industry for the flow direction of the orifice plate. It means that the sharp edge of the orifice plate should face the flow direction of the measured fluid, so that the fluid flows from the upstream end of the orifice plate to the orifice. The downstream end face of the plate. This is true for standard orifice plates, round orifice plates, and eccentric orifice plates. However, the 1/4 circular orifice plate and the tapered inlet orifice plate are exactly the opposite. The sharp ends of their openings must be carried The flow of the fluid is “big and small”.

How to ensure that the orifice plate has a long enough upstream and downstream straight pipe section has always been a headache in engineering design and construction. We have noticed in our work that the throttling element can only guarantee the measurement accuracy of the fluid based on the fully developed velocity profile of the fluid before and after. The specific requirements of the straight pipe manager shall be implemented in accordance with the "Code for Construction and Acceptance of Automatic Instrument Engineering".

At present, the most authoritative calculation in the flowmeter orifice plate calculation is the relevant formula in the international organization ISO5167. According to different flow characteristics, different types of orifice plates are selected. In the selection, it is very important that under one working condition When various types of orifice plates can be used, standard orifice plates conforming to ISO5167-2 or GB/T2624-93 specifications should be used. Since the manufacturing specifications of standard orifice plates are derived from long-term and large-scale experiments, they are very high. Reliability. The square root of the flow and differential pressure within the set range can maintain good linearity. As long as the manufacturer processes according to the standard, the flow rate is not required to be calibrated, and the non-standard orifice plate and most other flowmeters must be specially tested and calibrated.

In the design calculation of the power meter orifice plate, it is important to deal with the relationship between the scale flow rate, the upper differential pressure and β. According to the scale flow rate, a conventional β value is set, the ΔP value is calculated, and the β value is appropriately adjusted according to the ΔP value. The scale flow rate is usually 1.3 times of the normal operation flow rate and 1.1 times of the maximum flow rate. The maximum value of the two is the maximum flow rate, or the normal flow rate is about 70% of the scale flow rate, and the minimum flow rate is not less than 25%. , 16, 25, 40, 50kPa several files, the value of β is 0.5 to 0.6 is the recommended value.

Boxing Medals

ZHONGSHAN LAVI HARDWARE PRODUCTS CO., LIMITED , https://www.lavimedal.com