Flow sensors are vital in detecting and monitoring the flow of fluids in a channel. Paddlewheel sensors are among the mechanical flow sensors you can use in flow gauging. They are mechanical since they have moving parts that support their functions.
Paddlewheel flow sensors have a reliable accuracy. They are applicable in several firms except in custody transfer. Due to their moving parts, they demand regular maintenance. However, you can use them for a long time without replacement. Some of the important parts that we are going to discuss below:
Parts of a Paddle Wheel Flow Sensor
Paddle wheel sensors are simple in design. They have three main components- the paddlewheel, pipe fitting, and the controller or display. The paddle wheel rotates freely as the fluid passes through the wheel. Instead of a rotating wheel, the sensor could have an impeller with embedded magnets. The magnets are at a right angle to the flow of fluids. The impeller rotates when you insert it in a channel of flowing fluid.
Working Principles of a Paddle Wheel Flow Sensor
Magnets are an important part of a paddlewheel sensor as the magnets rotate behind the flow sensor and create a frequency and a voltage signal. The voltage signal output is equivalent to the flow rate. If the flow rate is high, then the voltage will be higher. Thus, the paddlewheel with magnets is useful when the fluid has some electric properties.
The paddle wheel gets into the pipe fitting. Also, you can use it as an inline or insertion style sensor. There are several connection methods, fittings styles, and materials for paddle wheel sensors. You need to install the sensor in a straight run pipe. Thus, assess the part of the flow channel where you can find good straight pipes upstream and downstream.
Controllers and flow show taps the signals from the paddlewheel. Then they convert the signals to the real flood flow rate. You can use the signals to send alerts to an external output, activate an alarm system, control the flow, etc.
Paddlewheel sensors offer a fair accuracy at low costs. Their applications are many in various industries.
How to Select Paddle Wheel Flow Sensors
There are a few factors you should consider when you are selecting flow sensors. The selection determines how the sensor will serve you and how it will fulfill its purpose. Below are the things you should look out for when selecting a paddlewheel flow sensor.
Type of Liquid
The type of liquid you use differs in viscosity. Highly viscous fluids will not let the paddlewheel rotate freely. Thus, it will hinder the functions of the flow sensor. Know the traits of your fluid before you settle for a paddle wheel flow sensor.
Purity of the Liquid
You can get fluid with the right viscosity but still be unsuitable for a paddle wheel sensor. If the fluid contains suspended particles, then it could prevent the wheel or impellers from rotating freely. The suspended solids get to the blades and block their movement. In the end, the sensor will cease functioning. Thus, ensure that your fluids are pure or give manageable solids.
Size of the Channel
Paddlewheel sensors are made in different sizes. Each size caters to a different cross-section area of a flow channel. Thus, you need to know the size of your flow channel before you select a flow sensor.
Straight Pipes Upstream and Downstream the Installation Part
Paddle wheel sensors are sensitive to disruptions. Barriers upstream or downstream of the sensor can lead to errors in the sensor readings. Thus, you should ensure you install the sensor in a straight line.
Pressure ranges
Different flow sensors can withstand different pressure ranges. Before you select a paddlewheel flow sensor, check the maximum pressure that your channel can produce. It will guide you on the flow sensor to select. They are designed with different strengths to withstand different pressures.
Temperature Ranges
Fluids flow under different temperature conditions. There are some materials of flow sensors that are only suitable for fluids under room temperatures. Also, some can withstand a certain degree of temperature. If you need a flow sensor that can operate at extreme heat levels, you need to see the manufacturer for customization. There are some materials they use to make special flow sensors to work under extreme heat levels.
Required Accuracy
Paddle wheel flow sensors are not the best for custody transfer. If you need high levels of accuracy, then you should opt for other types of flow sensors.
Is the Pipe Always Full?
Paddle wheel sensors need to work in a full pipe or the water to cover the wheels or the impeller. If the flow channel carries the fluid below the half mark, then the flow sensor will not function well. You may consider changing the pipings and take a smaller flow sensor.
Output Requirements
There are different types of output screens that you can use with a flow sensor. Also, there are different ways in which you use the output signals. Different flow sensors are made as a package for a set of requirements. Thus, you select the package that suits your needs.
Pipework Material
Different pipings use different types of materials. The type of materials depends on the fluid type that the pipe will carry. You can’t use steel or iron with a corrosive liquid. In most cases, such fluids will require hardened plastic. On the other hand, you can’t use plastic for high temperatures and pressures.
Wach pipework materials go well with a certain material of the flow sensor. Thus, use a flow sensor that matches the pipework material.
Advantages of Paddle Wheel Flow Sensors
- They offer a low-cost accuracy. They are reliable in a variety of industries.
- They are easy to install and use. In most cases, you’ll only need to follow the installation manual. Thus, they offer you a low cost of ownership.
- They are great when gauging gravity flow since they do not have a pressure drop.
- Although they are mechanical flow sensors, they need low maintenance since they are insertion types.
- They are compact, and you can use them to gauge large amounts of fluids.
While there are some of the advantages to purchasing paddlewheel flow meters, there are some constraints that prospective buyers should be aware of. While we have reported that these types of flow meters are not fit for gases and liquid. The paddle wheel flow meter works best with cleaner liquid types as, in some instances, particulates can stop the paddle from molding properly. Additionally, paddlewheel flow meters often require a hard flow profile to ensure the most reliable results.
Disadvantages of Paddle Wheel Flow Sensors
- They do not work well with dirty fluids. Suspended particles in a liquid can make the flow sensor stall.
- You can’t use them with gases
- They need a turbulent flow.
- They don’t work well with highly viscous fluids.
- They need straight run pipes upstream and downstream of the sensor.
- They need full pipes. The presence of air introduces inaccurate readings.
Conclusion
Paddle wheel flow sensors are applicable in many firms. Their accuracy is reliable when you need it for monitoring and sending alarms. However, it would help if you avoided them when inaccuracy can cause harm to humans and the environment.
