Bend Tube Flow MeterInstalled in natural bends of industrial pipelines or horizontal straight pipes, it exhibits no additional pressure loss and good measurement repeatability, suitable for complex fluid conditions with low working pressure, high medium temperature, dirty medium, strong mechanical vibration, and high flow rates.
Principle
Fluid flows through a pipe under certain temperature and pressure conditions. When it passes through a bend, the fluid will rotate in a corresponding circular motion. According to the theory of forced vortex flow, the circular motion of the fluid within the pipe is similar to the circular motion of a solid in space, thus necessarily generating an inertial centrifugal force. The magnitude of this centrifugal force is related to the fluid's velocity, density, and the radius of curvature in the circular motion (i.e., the radius of curvature of the bend sensor).
Since the curvature radius of the bend sensor is known, and the fluid density passing through the bend sensor can be accurately calculated using the computer of the main unit by measuring parameters such as fluid temperature and pressure, the magnitude of the centrifugal force generated on the bend sensor is solely a function of the fluid velocity. By measuring the magnitude of the centrifugal force, the fluid velocity within the pipeline can be determined. Multiplying the velocity by the pipeline cross-sectional area and the fluid density will yield the fluid flow rate. The calculation relationship is as follows:
Equation ① provides the functional expression for the average flow velocity and differential pressure of the fluid flowing through the elbow pipe:
V=a[（P1-P2）/ρ]β--------①
V - average fluid flow velocity
a - comprehensive flow coefficient, a = f(bend diameter ratio, Reynolds number, medium dynamic viscosity, pipe roughness, etc.), with the influence of the bend diameter ratio being the most significant:
P1-P2——Inside and outside pressure difference of the bend tube
ρ —— fluid density
Beta —— Index
Calculate the average flow rate V, and you can derive the functional expression for calculating the flow rate.
Q=S*V*ρ-----------②
In the formula:
S——Cross-sectional area of the bend pipe
V - average fluid flow rate; Applicable range
Bend tube flowmeterMeasurement medium and installation requirements:
Liquids, steam, gases, etc. Liquids include cold water, hot water, oil, liquid ammonia, and other liquids; steam includes superheated steam and saturated steam, gases include blast furnace gas, coke oven gas, oxygen, air, nitrogen, natural gas, acetylene, hydrogen sulfide, and more.
Bend Tube Sensor Type:
1. S-shaped bend sensor installed on straight pipeline.
2. L-shaped bend sensor installed at natural bend locations. L-shaped bend sensor. The L-shaped bend sensors are further categorized into LA and LB types.
Features:
Low installation costs, enhancing installation efficiency.
② Broad application range, can be installed wherever there is a straight pipe section.
③ More reliable measurements reduce installation errors, ensuring greater stability and dependability.
The LRD-WG type bend sensor is a standard 1.5D bend sensor, which has three spatial states: horizontal to horizontal; horizontal to vertical downward or from vertical upward to horizontal; and horizontal to vertical upward or from vertical downward to horizontal.
The LRD-WG type bend sensor is a large bend diameter ratio bend sensor, typically with a bend diameter ratio of 4D or 5D. It is usually located at the outlet of a boiler or steam turbine and is mainly used for measuring medium temperature and medium pressure steam (with a temperature of about 450°C and a pressure of around 4.5 MPa).
Material: Carbon steel, 20# steel, stainless steel, heat-resistant steel, or other materials.
Installation Conditions: Direct welding and flange mounting methods are available. The "L" type bend sensor is suitable for installation at the natural bend of the crude oil pipeline, with horizontal installation being the optimal working condition. The "S" type bend sensor is suitable for installation on straight pipe sections in any space. The required length of the straight pipe sections before and after is 5D and 2D respectively.
Features: Flow-throttle-free sensor, non-blocking, excellent wear resistance, no leakage, etc.
Bend Tube Flow Meters Performance Features
1. Simple structure; no throttle or insert parts; no additional pressure loss; energy-saving.
2. High accuracy up to 1.0-1.5 grades; excellent reproducibility with a reproducibility accuracy of 0.2%; wide measurement range.
3. Good adaptability to measuring media, suitable for the measurement of gas and liquid fluids under conditions such as high temperature, high pressure, and corrosion.
4. Low requirements for straight pipe sections: first 5D, then 2D; direct welding installation, no leakage issues.
5. Excellent stability, wear-resistant, calibration-free, easy maintenance, with long-term high-precision operation characteristics.
6. Adaptable to complex environments, insensitive to factors like high temperatures, dust, humidity, vibration, and electromagnetic fields.
7. Superior performance-to-price ratio and long service life.
8. Compared to other flow meters (like orifices, electromagnetic, etc.), the bigger the pipe diameter, the higher the cost-performance ratio of the bend flow meter becomes. 20mm – 2000mm.
Structural Form
The once-sensing element of the bent pipe flow meter—the bent pipe sensor—is divided into three types based on its installation on the pipeline:
&90° Bend Tube Sensor - Used for 90° bend connections in process piping, replacing the original elbow
&180° Bend Sensor - Used on straight pipe lines, replacing sections of straight pipe
135° Elbow Sensor - For 135° bend connections in process piping, as a replacement for the original elbow
The shape and structure of the 90-degree bend pipe are shown in the following illustration:
The shape and structure of the 180-degree bend pipe can be seen in the illustration below:
The shape and structure of the 135℃ bent pipe can be seen in the following illustration:
