One specific type of flow meter is a variable area flow meter which is one of the most straightforward and most versatile fluid measurement devices used today. It operates through a relatively constant drop in pressure to measure fluid flow. This flow meter consists of a float or vane where its position inside the tube changes as flow rate increases, allowing more liquid to pass through. Observing the location of the float indicates the flow rate in the calibrated flow tube.
A variable area flow meter either uses gravity or a piece of spring to return the float to a resting position. A gravity-operated flow meter requires vertical installation, while a spring-operated flow meter does not have installation limitations. All flow meters allow for local measurement readings. But in some instances, you can include a position transmitter to display the measurement remotely.
Types of variable area flow meters
The most commonly known type of variable area flow meter is the rotameter. It is a low-cost device which is also simple to use. Other advantages of a rotameter include a wide range of measurement, low-pressure drop, and linearity.
One disadvantage of a rotameter is that it requires vertical installation. It will also cost a lot more when you need a large rotameter. To mitigate the cost of installing a large rotameter, one alternative is using an orifice bypass or a pitot tube combined with a small rotameter. Installing a bypass rotameter is inexpensive but may be prone to measurement inaccuracy and sensitivity to the residue and fluid material build-up. In applications using a bypass rotameter, there is often an isolation valve installed so that maintenance can ensue without interrupting the whole process.
Another type of variable area flow meter is a tapered plug flow meter. It has an immovable core and a piston that moves as fluid flow changes. Another variation in variable area flow meter is a gate type meter resembling a butterfly valve. Fluid flowing through will force the spring-operated vane to move, and there is a corresponding mechanical connection which indicates flow rate locally.
Benefits of using variable area flow meters
Flow rate manufacturers engineer variable area flow meters in a variety of materials which suit different specifications for industrial applications. There are many benefits to using a variable area flow meter which are:
- Displays are easy to read and reliable.
- Variable area flow meters are economical and simple to operate.
- Readily available from most industry flow meter suppliers.
- There is an integral flow control to compensate for pressure variations.
- Come in a variety of materials and different designs suitable for varying pressure and chemical compositions.
- Easily integrate flow switches, automation valves, and alarms.
- You can request the manufacturer to include a fail-safe feature to fit any circumstance.
In choosing a variable area flow meter, you should trust not only the design of the product but also check the expertise of the manufacturer. Always look for a supplier with knowledge and years of experience in the field of engineering flow meters for all industries.