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How Does the Hedland Variable Area Flow Meter Work?

Hedland variable area flow meters take a unique approach to a traditional flow meters

Variable area flow meters measure the volumetric flow rate of liquids and gases. Traditional VA meters consist of a Tapered tube (Glass or Metal) and a float which could also be described as a shaped weight. As the flow increases, the float rises in the tapered tube until reaching a point where the upward force exerted by the flow and downward force of gravity are in balance. As the float settles to a stable position, a reading can be taken typically by using the top of the float as a point of reference against an internally mounted flow scale.

One major disadvantage to using gravity as the balancing force on a VA Meter is that the meter must be installed in a vertical position to work properly. In a Hedland VA Meter, gravity has been replaced with an ingeniously designed "Calibrated Spring" which opposes the flow in the forward direction. This spring provides a number of distinct advantages over a gravity based balancing force.

1. Hedland variable area meters can be mounted in any position without affecting accuracy. An optional inverted flow scale is available for inverted flows.

2. The Calibrated Spring decreases viscosity sensitivity making Hedland's variable area meter much more versatile than a standard Variable Area Flow Meter using gravity as the balancing force.

3. In addition, Hedland's unique design makes their meter inherently less sensitive to shock and vibration when compared to other variable area flow meters.

Hedland offers standard inline variable area flow meters for applications ranging in size from 1/4” up to 3”, in your choice of NPT, SAE or BSPP end connections. Although well suited for measuring any stable fluid with consistent flow properties, Hedland VA meters are typically the first choice for flow rate measurement in many Fluid Power applications. They’re also a popular choice in other industrial and manufacturing processes including: machine tool cooling and lubrication, packaging, semi-conductor manufacturing, die casting and plastic injection molding.

Interested in learning how to adapt an existing Hedland Oil or Water meter for use with other fluids? Read our article on calculating correction factors.