Advantages and disadvantages of Parshall tank with open channel flowmeter

The automatic monitoring system for a Parshall tank equipped with an open channel flow meter consists of a Parshall tank, a data acquisition instrument, and Alibaba Cloud software. The main equipment includes: a Parshall tank, a data acquisition instrument (composed of an open channel flow meter, cables, data lines, Control box, signal transmitting device, antenna), data receiving device, Alibaba Cloud data storage system, computer (users can view data through (website address, IP address)), in which the Parshall trough consists of an upstream contraction section, a short straight throat and The downstream diffusion section consists of 3 parts, divided into large, standard and small. There are 8 types of large, 12 types of standard and 5 types of small. Choose the appropriate model according to the drainage flow rate.

The open channel flowmeter is installed in the constriction section upstream of the Parshall tank. The Parshall tank converts the flow into liquid level. By measuring the liquid level of the water flow in the constriction section of the Parshall tank below the open channel flowmeter, the flow rate is measured according to the corresponding parameters of the Parshall tank. The relationship between water level and flow rate is converted into drainage flow rate through calculation formula. The measurement principle of Parshall tank is shown in Figure 2. The flow calculation formula is as follows:

In the formula: Q - flow rate, L/s; C and n - constants (check the corresponding coefficients through the options of the Parshall tank); Ha - water depth level, m.

According to field practice, the advantages and disadvantages of this flow meter are as follows:

(1) Advantages. ① Simple structure, reliable operation and long service life; ② It is made of stainless steel or fiberglass to adapt to the needs of different media; ③ The Parshall tank forms a stable water surface, and the water level measurement accuracy is high; ④ The interval between recording one data The time can be set to any length. The time set for this project is to collect data once every 1 minute, which further improves the accuracy of the measurement data; ⑤ The Alibaba Cloud system is used to store data, which is safe and reliable. You can log in to the website to view the data anytime and anywhere; ⑥ Later maintenance costs Low. No maintenance has been carried out since it was put into use 1+a. Data has been collected continuously on site and meets construction needs.

(2) Disadvantages. ① The construction of the Parshall tank is relatively complex, with many ancillary equipment and relatively high installation costs; ② In order to ensure the normal operation of the facility and ensure its measurement accuracy, daily inspections such as regular rust removal, dredging, and equipment inspection are required on the tank body. Especially in channels with a large sediment content, dredging is more frequent; ③ The center line of the Parshall trough should coincide with the center line of the ditch, so that the water flow does not flow into the trough, and the on-site installation accuracy is required to be high; ④ There should be a straight section greater than 10 times the width of the trough upstream of the Parshall trough, so that the water flow can enter the Parshall trough smoothly, and the site will occupy a larger area; ⑤ The data is susceptible to magnetic field interference during the measurement and transmission process, and it needs to be installed on an electromagnetic A place with less disruption.