What if there were a way to obtain a single, accurate measurement that represents an entire cross-sectional flow area? The solution for this lies in a remarkable piece of technology known as averaging pitot tubes. Meticulously curated for the industry, the versatility of averaging pitot tubes has expedited their application in industrial settings.
The blog delves into the realm of averaging pitot tubes and concepts associated with them.
What is an averaging Pitot tube?
To begin with, an averaging pitot tube is an “averaged” differential pressure based measuring instrument which is used to estimate the flow rate in an enclosed structure (pipe or a conduit). Your may ask, how is an averaging pitot tube different from a regular pitot tube? Averaging Pitot tube is designed to measure the flow velocity across the entire cross section of an enclosed structure as multiple sensing ports are evenly distributed along the length. Regular Pitot tube simply measures the flow velocity at a single point usually with sensing port at the tip.
How does an averaging Pitot tube work?
Core principle behind multiple differential pressure based flow measurement instruments is Bernoulli’s equation and the same works here. Averaging Pitot tube constitutes of an outer tube with multiple pressure sensing ports. Inside are two tubes connected to the pressure sensing device. The tube is introduced in pipe along the flow path. As the fluid strikes the tube surface (high pressure side is created at the portion facing the fluid flow) pressure is transmitted to the inner section of the tube.
The sensing ports inside the internal averaging tube connected to pressure-sensing device provides an average of pressures measured from different ports. The readings for the low pressure side are obtained using similar sensing ports connected to a pressure sensor which can be a transducer or transmitter. The output reading on transmitter is the variation in the pressure values at different points along the length of the tube. As per Bernoulli’s equation, the pressure difference is equal to square of flow velocity. Presence of multiple pressure sensing ports ensures high accuracy and precision.
Why are averaging pitot tubes important in industry?
- Versatility: Owing to their adaptivity, averaging pitot tubes can be integrated in several HVAC systems, power generation, process industries, etc.
- Lower maintenance requirements: Averaging pitot tubes have fewer working parts and are less prone to clogging as in case of other instruments.
- Cost effectiveness: While the initial cost of averaging pitot tubes is higher than the other flow measuring instruments, their accuracy, reliability, durability make them a cost effective choice for long run.
- Reduced sensitivity to geometry: Averaging pitot tubes are less sensitive to variations in pipe/duct geometry compared to other devices.
- Improved flow profile measurement: As the velocity at different points in a pipe are measured, we can get a better understanding of the fluid flow pattern. This information is crucial for ensuring a distributed flow.
What are the key industrial applications of averaging pitot tubes?
- Aerospace: These tubes are employed in aircrafts to measure air speed, air velocity which provide integral data for navigation and control.
- Petrochemical and Chemical Industries: Averaging pitot tubes are used to monitor the fluid flow in pipelines and ducts. These ensure even distribution of process fluids in a pipeline and controlling the flow rate.
- Wastewater treatment plants: Such type of pitot tubes are used in wastewater treatment plants for monitoring the flow of gasses and water in the pipelines and filters.
- Mining: Averaging pitot tubes are an integral component used in mining sector to measure air flow in the mines to establish an accurate ventilation system.More about flow elements in the subsequent articles!