The Basics of
Variable Area Flowmeters
A variable area flowmeter is designed such that the device
has a cross-sectional area through which gas or liquid passes. This area changes
depending on how the rate of flow changes, causing a measurable effect by which
the rate of flow can be determined. In this article you will learn about where
variable area flowmeters are used, and why they are best suited for those
applications.
Where are Variable
Area Flowmeters Used?
The typical place where you will find variable area
flowmeters is in rugged industrial service. Their economical composition makes
them one of the most affordable and reliable methods for measuring process
liquids and gasses. They are often built with end caps that can be removed,
allowing them to be easily cleaned between uses. They can be installed quite easily. There
are different sized of variable area flowmeters, also known as rotameters,
available, depending on which rate of flow you intend to measure. You will find
them most commonly being used in a few specific applications, such as producing
polyurethane foam, in test benches for fuel flow, and in test benches for
hydraulic components.
The Composition of a
Variable Area Flowmeter
There are various different ways in which a rotameter could
be built, but the following is a description of what might be found in an
average device. To secure the end-fitting, three O-rings and an end gasket seal
are set in place. The O-rings are compressed by a packing gland or frame, and
this allows for a seal to take place between the tube and the fitting. Whether
you want a flanged connection, or if you prefer a corrosion-resistant material,
you can choose which kind of fitting will suit your needs best. You can mount
the device either in-line or on a panel, thanks to the standard frame/bezel
assembly. Stainless steel frames contain tapered metering tubes.
How a Variable Area
Flowmeter Works
The tapered tube is typically made of a smooth borosilicate
glass. Within this tube is a freely moving metering float made of a material
that is compatible with the fluid to be processed. Before flow takes place, the
float will remain at the bottom. Once liquid or gas begins flowing through the
tube, the float will be pressed upward in proportion to the pressure created.
The float will oscillate a bit as its weight reaches equilibrium with the
hydraulic force. Once it reaches this equilibrium, it remains in place as long
as flow rate does not increase or decrease. However, if the flow rate does
increase or decrease, the position of the float will change accordingly.
Before You Order
