Applications Where Variable Area Flow Meters Deliver Value and Performance

There are many industrial and municipal applications where accurately measuring fluid flow is key to the success of the process. Selecting the right technology for a particular application is an important decision.

Variable Area (VA) flow meters have long been a preferred choice because of their reliability, cost-effectiveness, and simplicity. While more complex flow measurement options, such as ultrasonic meters and electromagnetic meters (mag meters) offer higher levels of precision and data collection capabilities, Variable Area flow meters remain the technology of choice where simple, dependable performance and cost advantages are a consideration.

Why Choose Variable Area Flow Meters?

Variable Area Flow Meters utilize a vertically tapered tube through which the fluid to be measured passes, from the smaller diameter end of the meter vertically to the larger diameter. As the fluid flows through the tube, it forces an indicator (float) upward. The clearance space (area) between the float and tube increases as the float approaches the top of the meter. This increasing area requires a larger amount of fluid to force the float higher. By varying the taper of the tube, the mass of the float, and the length of the tube, different flow ranges can be calibrated.

The simplicity of this design means there is no need for complex electronic components or for a power source. Unlike paddlewheel or ultrasonic meters, which may require specific flow conditions or additional calibration, Variable Area flow meters function reliably across a range of applications and require minimal maintenance.

In addition, VA meters are popular because of their cost efficiency. This is particularly beneficial in applications that require flow measurement at multiple points in a system, where outfitting each point with a more costly flow meter can be prohibitively expensive.

It could be said that Variable Area Flow Meters provide an ideal balance of economics and accuracy, particularly for OEMs building water treatment or industrial process systems.

Manufacturers like Blue-White® Industries have optimized their Variable Area flow meter designs to ensure accuracy, durability and affordability, making these units an attractive option when designing cost sensitive systems.

Common and Specialized Applications

One of the most common applications for VA flow meters is as a component of reverse osmosis (RO) water purification systems. In this application the Variable Area flow meters monitor the flow through membranes to ensure optimal performance of the system. RO technology already carries a high price tag, both in terms of capital costs and the operating expenses associated with energy usage and membrane changeouts. As such, operators need to have reliable flow measurement without inflating system costs. The accuracy of VA meters — typically within ±4% of full scale — is precise enough to track flow through membranes, helping operators detect performance issues like fouling and plugging before those conditions affect broader system performance.

Other well-known applications include chemical dosing systems, such as calcium hypochlorite feeders used in commercial pools, cooling tower systems, and chemical dosing in both wastewater and drinking water treatment processes. These systems rely on flow meters to ensure chemicals are being delivered to the system. The ability of VA meters to provide a simple, real-time visual indications of flow ensures that operators can quickly verify proper dosing rates.

In less common applications, Variable Area Flow Meters play a key role in geothermal heat pump systems, where they monitor the water flow circulating through the system to ensure efficient heating and cooling. Similarly, paint finishing systems and industrial seal water monitoring, and solar systems also benefit from VA meters, as they provide a reliable method to track water flow in these processes.

Balancing Accuracy with Application Needs

While high-precision digital flow meters can offer accuracy within fractions of a percentage, the reality is that many applications do not require this level of detail. The ±4% full-scale accuracy of a high-quality VA meter is more than adequate for applications like RO systems, where significant deviations — such as membrane fouling — will manifest as easily detectable changes in flow. The key is selecting a meter that provides sufficient accuracy while avoiding unnecessary expense.

For OEMs designing water treatment or process systems, the selection of flow meters can be a cost-sensitive decision. When purchasing in bulk, even a small price difference per unit can add up significantly. A well-built Variable Area Flow Meter from a trusted manufacturer can strike the right balance between affordability and performance, ensuring reliable operation while keeping costs in check.

For instance, Blue-White® Industries’ VA acrylic flow meter bodies are annealed for added strength, and for more heat and chemical resistant capabilities, the company manufactures Polysulfone flow meters. Blue-White flow meters are also tested for accuracy and repeatability. While it may be tempting to get the lowest-cost flow meters available, quality of construction, accuracy and service life must also be considered

Blue-White® Industries’ flow meters are manufactured in the company’s U.S. facility with quality-controlled materials and production processes. The company’s 68 years of focus on quality ensures that customers receive a flow meter that will meet performance expectations.

Variable Area Flow Meters provide an excellent balance of accuracy and affordability for applications where extreme precision and flow data may not be necessary. By selecting high-quality VA meters from reputable manufacturers like Blue-White® Industries, OEMs and operators can ensure dependable performance while keeping operational costs under control.

Written by:
Blue-White® Industries
714-893-8529

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