Accurate flow measurement is crucial in various industries and applications to ensure efficient operations, process optimization, and cost savings. Proper flow measurement allows for better control over processes and helps identify potential issues or inefficiencies. However, achieving accurate flow measurements can be challenging due to flow disturbances and other factors that affect measurement reliability. Flow conditioning plays a vital role in improving the accuracy of flow measurement.
Flow conditioners like the CPA 50E flow conditioner and other flow conditioning devices like perforated plates and tube bundles are designed to mitigate flow disturbances and optimize flow profiles. These devices create a uniform flow field and reduce swirl, resulting in a more predictable and consistent flow pattern.
Using a flow conditioner, the flow profile can be transformed into a fully developed flow profile, which is the ideal state for accurate flow measurement. Fully developed flow profiles exhibit uniform velocity distribution, symmetry, and minimal swirl. This allows flow meters, such as ultrasonic flow meters and turbine meters, to operate in an optimal flow environment, leading to improved measurement accuracy.
Understanding Flow Conditioning
What is a Flow Conditioner or Conditioning?
A flow conditioner is a specialized device designed to optimize flow profiles and mitigate flow disturbances to improve flow measurement accuracy. They aim to create a more uniform and predictable flow pattern, enabling flow meters to operate under ideal conditions for precise measurements.
Flow conditioners are carefully designed to provide sufficient straight run requirements for flow meters, compensating for limited straight pipe sections. They help achieve repeatable velocity profiles and mitigate the effects of installation disturbances such as valves, bends, and fittings. The choice of flow conditioner material, such as 316 stainless steel, ensures compatibility with various fluid properties and process conditions.
Types of Flow Conditioners
The two main types of flow conditioners are the tube bundle, also known as straightening vanes and perforated plate flow conditioners.
Tube Bundle
A tube bundle consists of multiple small-diameter tubes arranged in a welded bundle. They aim to make the flow profile swirl free. However, tube bundles may not produce a fully developed flow profile and can lock in flow distortions.
The length of a flow conditioner does not directly correlate with its effectiveness, as longer tube bundles can introduce more harm than good. These flow conditioners operate through three distinct actions: initial pressure drop, fluid passage through the device, and re-entry into the pipe flow. Tube bundles with equally sized holes and low-pressure drops cannot eliminate uneven velocity distribution and distorted flow profiles, leading to the same distorted distribution re-entering the pipe.
Additionally, tube bundles tend to lock in profile distortions due to discrete flow patterns formed within the flow conditioner, which hampers their ability to restore fully developed velocity flow profiles. When the fluid leaves the tube bundle, the separate miniature flow paths recombine into one, resulting in a distorted profile where each passage does not contribute equally to the flow. Consequently, tube bundles become an installation effect, causing flow measurement errors similar to valves or tees. It is essential to provide sufficient straight run requirements to ensure fully developed flow when using tube bundles, which may necessitate a 30D to 40D meter run in the presence of swirl.
Perforated Plates
Perforated plates offer significant advantages over tube bundles as flow conditioners due to their carefully designed hole pattern, aggressive pressure drop, and short length.The hole layout of a perforated plate is strategically designed to effectively redistribute the fluid flow, promoting faster attainment of the fully developed flow profile distribution.
The pressure drop created by the plate ensures proper balance and equal fluid movement through each hole, eliminating flow distortions and asymmetry. As the fluid is accelerated through the plate’s holes, it acts as a filter, removing the rotational vector from the swirl.
The short length of the perforated plate prevents the fluid from redeveloping flow profiles within the flow conditioner itself. As a result, the flow exiting the perforated plate is symmetrical, swirl-free, and quickly recombines into a bulk, fully developed flow profile after 5 – 8 internal pipe diameters.
This effectiveness is evident in downstream flow profiles, demonstrating improved flow characteristics and reduced disturbances compared to upstream flow conditions with elbows or tees. The perforated plate flow conditioner’s design and performance make it a superior choice over tube bundles, providing more reliable and accurate flow conditioning for various applications.
Different Flow Meter Types – Flow Conditioning
Orifice Meters
Orifice meters, commonly used for differential pressure measurement, force the flow through an obstruction known as the primary element. The pressure difference before and after the obstruction is measured, and the square root of this difference is proportional to the fluid’s mass flow rate and velocity. This principle applies to different differential pressure meters, including venturi meters, cone meters, wedge meters, and the multi-hole orifice plate.
When it comes to orifice meters, flow conditioning requirements are essential due to their sensitivity to velocity profile distortions and swirls. Lower beta ratio orifice installations are less affected by velocity profile distortions, as the increased pressure drop helps act as a flow conditioner and results in a more averaged flow profile.
Swirl is a significant concern in orifice meters and differential pressure measurement. The rotational velocity component introduces measurement errors, leading to local pressure reductions that do not reflect the overall bulk pressure behavior. Severe swirl instances can cause deviations from fully developed energy distribution, and the interaction of swirl with the primary element can further complicate flow measurement.
By employing a perforated flow conditioner, orifice meters can achieve improved flow conditioning, resulting in more reliable and accurate measurements.
Ultrasonic Meter
An ultrasonic flow meter utilizes ultrasonic sound pulses to measure flow velocity. By bouncing these pulses between opposite sides of the pipe along a predetermined path, the difference in travel time is used to calculate the average velocity across that path. However, ultrasonic flow meters face limitations in analyzing variables other than transit time.
Modern ultrasonic meters have multiple signal paths positioned at different distances across the pipe to address these limitations. These paths provide a comprehensive view of the flow by combining results from each path. The path locations are strategically chosen to capture critical flow information, such as areas with significant flow volume and swirl. Different path orientations help counteract swirl and other factors causing transverse velocities across the pipe.
While an ultrasonic meter offers advantages in flow measurement, its reliance on assumed symmetrical and evenly distributed velocity flow profiles poses challenges. Without the ability to directly observe the flow profiles, determining the accurate representation of the actual flow becomes complex.
It is worth noting that flow conditioning requirements apply to both liquid and gas applications, contrary to misconceptions surrounding the suitability of certain flow conditioners. Properly designed flow conditioners, including perforated plates, can be used in various fluid types, facilitating effective flow conditioning and accurate measurements for ultrasonic flow meters.
In summary, flow conditioners play a vital role in enhancing the performance of orifice meters and ultrasonic meters. The flow conditioner ensures more reliable and accurate flow measurements across different meter types and fluid applications by addressing velocity profile distortions, swirls, and other flow disturbances.
Factors to Consider When Selecting the Right Flow Conditioner
Application-specific requirements: When selecting a flow conditioner, it is crucial to consider the application’s specific needs. Factors such as fluid type, flow rate range, temperature, and pressure requirements should be carefully evaluated to ensure the chosen flow conditioner can effectively meet the application’s demands.
Pipe size and material: The size and material of the pipe play a significant role in determining the appropriate flow conditioner. Other flow conditioners are designed to accommodate various pipe sizes and materials, ensuring compatibility and optimal performance.
Pressure drop considerations: Pressure drop is an important factor to consider, as it affects the overall efficiency and operation of the flow system. Understanding the pressure drop characteristics is essential to ensure that the chosen conditioner provides an acceptable pressure drop while maintaining accurate flow measurements.
Installation options and compatibility: The installation method and existing piping systems should be evaluated. Some flow conditioners may require specific mounting orientations or additional installation considerations. Selecting a flow conditioner that can be easily installed and integrated into the existing infrastructure is important.
Canada Pipeline Accessories Flow Conditioner Solutions – CPA Flow Conditioner performance
CPA 50E
The CPA 50E flow conditioner is a plate-style model by CPA, designed to enhance flow straightening and improve velocity profile distribution for accurate flow measurement in various gas and liquid applications. With over 20 years of experience, it has been widely tested and accepted, making it a reliable choice for flow conditioning with minimum straight-run requirements. The CPA 50E ensures proper performance and repeatable velocity profiles in multiple installation options.
CPA 55E
The CPA 55E flow conditioner is designed to address more severe measurement scenarios with downstream pipe disturbances, making it ideal for gas applications with high velocity and Reynolds numbers. Its innovative stepped profile geometry reduces noise levels by up to 30 dB compared to the CPA 50E, and it efficiently eliminates swirl and cross-flow, ensuring accurate flow measurement even in challenging conditions. With minimum straight run requirements of 6D for gas USM applications and 10D for gas turbine applications, the CPA 55E offers higher performance and lower turbulence, enabling it to be installed closer to ultrasonic meters.
CPA 65E
The CPA 65E flow conditioner is designed for less severe measurement or liquid scenarios, offering exceptional flow conditioning performance with half the pressure drop of typical plate-style conditioners and lower turbulence. It is recommended for liquid applications with low velocity and Reynolds numbers, making it suitable for water, petroleum, crude oil, LNG, and pump applications. An innovative stepped design optimized using fluid dynamics efficiently eliminates swirl and cross-flow, reducing noise levels and allowing installation closer to ultrasonic meters.
CPA TBR TBRL
The CPA TBR/TBRL flow conditioners are designed to be pinned in the pipe without requiring a flange for installation. They offer reliable flow conditioning, recommended for orifice meter applications, ensuring accurate measurements in various flow conditions. However, it’s essential to note that they are not recommended for liquid applications due to higher drag forces and pressure drop risks that may dislodge the flow conditioner.
Conclusion
The flow conditioner is critical in achieving an accurate flow meter and operational performance. It helps address challenges like velocity flow profile distortions, swirls, and flow disturbance that can adversely impact measurement accuracy. By employing a suitable flow conditioner, such as the CPA 50E, CPA 55E, CPA 65E, and CPA TBR/TBRL, it is possible to achieve fully developed flow profiles, mitigate turbulence, and ensure repeatable velocity profiles. Properly conditioned flows enable differential pressure meters, orifice meters, ultrasonic meters, turbine meters, and other flow measurement devices to perform at peak efficiency, delivering reliable data in a wide range of flow conditions.
Industries and engineers must explore and implement flow conditioning solutions for optimal flow measurement accuracy and operational efficiency. Incorporating advanced flow conditioners like the CPA series can ensure precise and reliable flow data across various flow scenarios, including those with downstream disturbances and low-velocity conditions. By investing in flow conditioning technology and following best practices, organizations can minimize measurement uncertainties, optimize their processes, and make informed decisions based on trustworthy flow data.
Are you ready to learn about Cherokee Measurement & Control’s flow conditioner solutions? Contact us today at sales@cherokeetulsa.com or give us a call at (918) 446-1611.