Installation methods and precautions for radar flow meters and radar velocity meters in wide river measurement

1. Installation requirements

The equipment installation method adopts the outdoor integrated rack and stainless steel chassis method. The chassis, communication antenna and other modules are installed at a suitable height at the waist of the rack's upright pole. The chassis must be reliably locked, and the communication module antenna and other modules can be reasonably and firmly installed on the rack. Above, the solar panels are protected from obstruction by tall buildings or trees. Each installation point can have certain adjustment capabilities in the horizontal and vertical directions to avoid mutual interference or obstruction of the installation equipment.

The RTU, communication module, data conversion module and other specifications are integrated into the integrated stainless steel chassis, and the installation is required to be firm. Each cable in the box is arranged in a cable trough, and the cable head is crimped with terminal blocks.

(1) The chassis is made of stainless steel, and the integrated rack can be made of galvanized pipe or stainless steel.

(2) The appearance of the integrated rack and chassis should be beautiful and generous, with appropriate proportions and smooth surface. The welded parts should be free of defects such as slag inclusions and pores. The chassis should have warning signs indicating that it is flood control equipment or similar information.

(3) The metal shells of integrated racks, chassis, antennas, rain gauges and other components need to form an equipotential body and are ultimately connected to the protective ground grid through the rack.

(4) The rack, chassis and other components are connected and fastened with stainless steel connectors and fasteners, and various exposed cables are protected with stainless steel plastic-coated corrugated pipes.

(5) On-site installation can rely on existing building foundations such as bridges and brackets, but the flow meter must be installed horizontally, that is, the radar wave emission direction of the water level probe of the radar flow meter is perpendicular to the direction of the water flow, and the radar wave of the flow velocity probe of the radar flow meter The angle between the launch direction and the water flow direction is approximately 35° (the angle between the launch direction and the vertical direction is 55°). The installation of the flow meter should ensure that the angle between the radar wave emission direction of the flow velocity probe and the direction of the water flow is approximately 35° (the angle with the vertical direction is 55°).

(6) Radar flow meters and radar flow meters should be installed behind the gate. If installed in front of the gate, the water surface flow rate will be very small and the bottom flow rate will be very large. When installing behind the gate, the radar flowmeter and velocity meter should be installed as far away from the gate as possible, and should be installed in a location where the water flow is stable and the river section is relatively regular.

2. Installation method

Non-contact flow monitoring of rivers requires the selection of different monitoring solutions based on the cross-section conditions of the diversion river and the width of the river under the condition that the flow measurement accuracy requirements are met: single-point (pole type) installation flow measurement is used for rivers below 10m. -Double-point (pole type) installation flow measurement method is used for rivers 20m long, and array (cableway) installation flow measurement method is used for rivers above 20m, and appropriate flow measurement equipment is configured according to different installation methods.

Single point pole installation method

The rod flow meter bracket consists of three parts: the main steel pipe column, the horizontal steel pipe, and the reinforced concrete foundation. The main steel pipe column is 5 to 6 meters high, and a hot-dip galvanized eight-sided variable-diameter steel pipe with a diameter of 300 to 200 mm and a wall thickness of 8 mm is used. The solar panel is installed on the top of the column; the cantilever length of the horizontal steel pipe is 2 to 6 meters, and the diameter of the horizontal steel pipe is 250 to 6 meters. 150mm, 6mm wall thickness hot-dip galvanized eight-sided variable diameter steel pipe. The reinforced concrete foundation can use C30 independent foundation or pile foundation according to geological conditions. Pile foundation is used when the construction site is located in a river, on a steep slope or the foundation soil is poor.

The single-point pole installation method uses a flow meter to be installed on one side of the river for flow monitoring. Taking the installation location of the radar flowmeter 8 meters away from the river surface as an example, the diameter of the flow velocity measurement sector of the radar flowmeter perpendicular to the direction of water flow is approximately 4.25 meters. It can be seen that the coverage of radar is limited, and it is difficult to use the flow velocity of the watershed covered by the flowmeter to represent the flow velocity of the entire section.

With this solution, the amount of on-site construction is minimal, but the measured flow rate of the river section deviates greatly. Therefore this solution is not recommended.

Pole installation method

The double-point pole installation method is basically the same as the single-point installation method. A flow meter is installed on both sides of the river for flow monitoring. Each flowmeter represents half of the flow of the entire river, and the algebraic sum of the flows of the two flowmeters is the flow of the entire river.

Similar to the single-point pole installation method, due to the limited coverage of the radar, it is difficult to use the flow rate of the watershed covered by the flowmeter to represent the flow rate of the entire section.

Using this solution, the amount of on-site construction is small, but the measured flow deviation of the river section is still large. Therefore this solution is not recommended.

Array (cableway) installation method

When the river width is greater than 20 meters, the array (cableway) installation method is used. The array (cableway) installation method consists of four parts: cableway steel pipe columns, cables, steel column foundations, and ground anchor foundations. The steel pipe column of the cableway is 6 meters high. It uses a hot-dip galvanized eight-sided variable-diameter steel pipe with a diameter of 300 to 200 mm and a wall thickness of 12 mm. The flow meter guy wire and anchor cable are fixed on the top of the column; the wire specification is 1×7∅11.40 galvanized steel strand. The length of the line should be determined according to the actual conditions on site. Both the steel column foundation and the ground anchor foundation adopt C30 independent foundation, with the natural foundation as the basic bearing layer. The characteristic value of the foundation bearing capacity is not less than 120kPa.

The array installation method, that is, one flow meter dragging multiple flow rate meters, can overcome the problem of large deviations in flow monitoring data caused by uneven flow speeds and irregular cross-sections in rivers. The array installation method is based on the characteristics of the river section, taking into account the river bed elevation distribution and the full-section flow pattern distribution, and divides the entire flow monitoring section into a number of flow measurement zones. Each flow measurement zone is deployed with a flow meter, and a radar flow meter can be deployed. in any flow measurement zone. This installation method greatly reduces the deviation in flow measurement caused by irregular natural river sections and uneven flow velocity distribution. In terms of construction, there are mature engineering experiences for existing bridges or cableways that can be used for reference. Therefore, it is recommended to use array installation for flow monitoring in wide rivers.