A Paddlewheel flow meter is a simple, reliable, and mechanically designed meter with free rotating wheels located in the fluid stream path to measure the liquid flow rate. The gas or liquid flowing in the pipe leads to the turbine’s spinning in the axis, and the spinning rate is proportional to the flow velocity.
A paddle flow meter can measure high fluid flow rates at low temperatures and pressures and can also operate in low viscous fluids and water despite their versatility feature.
We can classify paddlewheel flow meters into two main mechanical classes, namely;
i) Tangential flow
ii) Axis flow
Tangential flow is paddlewheel flow meters that contain a water wheel structure. Axis flow is paddlewheel flow meters that contain a windmill structure.
Since the fluid flow is directly proportional to the Paddlewheel motion, the paddle revolution using the liquid flow enhances the flow rate measurement by counting the rotations the paddle moves around. The magnets help transform the rotation numbers to flow rate through the pulses derived from the border of the paddle and the revolution axis.
How Paddlewheel flow meter works
The device has three primary components: the paddlewheel sensor, display or controller, and pipe fittings. Also, the paddle flow meter can use on a regular basis and in the industries.
i) Pipe fittings
Pipe fittings are made in different styles to suit specific applications. Some can directly install into the pipes through socket fusion, butt fusion, socket weld, male or female threads, etc. The fittings, known to be inline, come in different structures like stainless steel, polypropylene, and PVDF.
Saddle-style fitting usually exists inside the pipe. Therefore, when installing a saddle, you should drill a hole inside the pipe and place the saddles in such a way that they clamp within the pipe.
ii) Paddlewheel sensor
Paddlewheel sensor is the Paddlewheel together with its magnets which are embedded, and the electrical sensor. The sensors are made of different materials depending on the application type. The two common sensors are; Hail effect and AC coil.
iii) Display or Controller
The controllers or the display receives the signal from the Paddlewheel sensor, changes it to the actual flow rate, and displays the fluid flow values. The initially processed signal starts and stops the pumps, meters the pump, opens and closes the valves, indicates low or high flow rate alarms, etc.
The above components are what make up the working principle of a paddle flow meter. The device operates when the Paddlewheel sensor is placed inside the pipe fittings where some paddle comes through the flow stream leading to the spinning of the Paddlewheel due to the movement of fluids inside the pipe.
Production of electrical pulses proportional to the flow rate then occurs when the embedded magnets inside the paddle revolve over the sensor. The quicker the flow, the higher the voltage output and frequency.
Advantages of paddlewheel flow meter
- A paddlewheel flow meter can detect at zero flow rate
- Compact in size, adjustable device
- Low cost with high accuracy
- Repeatability
The paddlewheel flow meter can be used for acidic liquids, which are non-granular. It basically uses to calculate the instantaneous flow rate and concentrated flow. It can be used to adjust the valve according to the flow rate of liquid. The paddlewheel shaft is vertical to the flow, and with the use of this, it provides less axial flow, so less friction.
Types of Paddlewheel flowmeters
Paddlewheel flow meters come in different types, such as;
i) Liquid flow meters; Calculates the quantity flow of the moving fluids.
ii) Gas flow meters; Determines the gas flow in an enclosed pipe, with changing composition.
iii) Water flow meter; Measures the water flow rate.
iv) Air flow meter; Measure the part of airflow to obtain the airflow rate.
Applications of paddle flowmeters
i) Paddle flow meters are used in dispensing systems
In water dispensing systems, preset helps in providing cycle timers to dispense water. Activation of the timer triggers the system to dispense water until the preset time displays time out. Getting the accurate flow rate is usually low with preset cycle timers since they don’t measure the actual flow rate.
Issues interfering with the system may changes the flow rate, thus leading to errors in the dispensing water as in changes in the system pressure and components of pumps leading to the pump output.
The amount of dispensed water is measured by the Paddlewheel sensor, where the activation of the dispensing system makes the electronic flow controller activate the pump, thus opening the right dispensing valves. The sensor then generates electronic pulses, and the electronic flow controller counts them.
When the dispensing system has dispensed the required amount of water, the dispensing valve closes, and the pump stops operating.
ii) Used in the verification of the flow
Paddle Wheel flow meters verify the flow of different fluids and gases, where the sensor measures the metering pipe output of chemicals at a rate of one ounce per minute. The Paddlewheel flow sensors also alert the user to the existing system error in the metering pumps.
When the metering pump is electronic, it reacts to the paddlewheel signal output. Clogged fittings, malfunction of the pump, and exhausted chemical containers may hinder the working process of the metering pump.
iii) Used in controlling chemicals in chemical industries
The injection of chemicals such as acids and chlorine in water systems should be proper to enhance the correct proposition of chemicals. Too much or too few chemicals can lead to system problems. Paddlewheel flowmeters start and stop inexpensive, fixed feed metering pumps, leading to the proper injection of chemicals.
Other applications include irrigation systems and metering pump output in various industries.
Paddlewheel flowmeters usually work best with clean fluids since debris and particles prevent the paddle from revolving around the pipe properly.
Advantages of Paddlewheel flowmeters
1.Paddlewheel flow meters have no pressure drops; hence can measure gravitational flows.
2. Paddlewheel flow meters have high accuracy on the system flow with low solutions costs.
3. Paddlewheel flow meters are simple and reliable to use.
4. The maintenance costs are low due to the design of the insertion flow meter.
5. The cost of ownership is low due to Paddlewheel flow meters’ easy installation and operation.
Disadvantages of paddle flow meter
1. Paddlewheel flow meters are not suitable to measure gaseous substances.
2. It works only with clean fluids since dirty fluids may contain particles that prevent the paddle from rotating or spinning for one to record the measurement.
3. In cases with flow profile laminar for high viscous fluids, the meters may not function properly.
4. To record accurate results, Paddlewheel flow meters need consistent velocity fluid across the pipe diameter. It is sometimes known as the turbulent flow.
5. Inaccuracies may occur from air entering the line when the pipe is not full.
6. Paddlewheel flow meter uses a straight pipe run before and after flow to enhance the flow stream’s spinning pattern, thus disappearing.
Conclusion
A Paddlewheel flow meter is essential in various applications like water dispensing, chemical measurements, flow verifications, etc. Consider performing frequent maintenance of this flow meter device to enhance effective operation in any application. Engineers or system operators can help you install the device and show you how to operate it.
