Measuring the fluidity of liquids is critical in industrial applications. In some cases, the skill of conducting accurate flow measurements is so vital that even a minute difference can either lead to a profit or a loss. In other situations, inaccurate flow measurements or failing to take measurements can lead to serious and disastrous results.
The most liquid flow equipment controllers determine the flow rate inferentially; either by noting changes in kinetic energy or measuring the fluid’s velocity. The velocity of fluid will depend on a pressure differential that forces the liquid through a conduit or pipe. Since the pipe’s cross-sectional area will always remain constant, the flow rate is the average velocity.
How does a liquid flow controller work?
A liquid flow controller also referred to as metering flow of liquid, typically has an inlet that receives the liquid. This inlet passes the liquid via a high resistance liquid flow path, during which a pressure drop occurs. The pressure sensor will measure the amount of liquid flow and generates a pressure drop signal. This signal is fed into an electronic circuit. A temperature sensor is positioned in the high-resistance liquid flow-path which will generate a temperature signal that is fed into the electronic circuit. The electronic circuit will create a viscosity-normalized flow signal which will be compared to a set point; thus generating an error signal. In the downstream path of the high-resistance liquid flow is a valve which controls the flow of liquids. It is driven by an error signal and will monitor the flow.
An example of a liquid flow controller: the Mass Flow Controller
Mass flow controllers (MFCs)are devices that measure and regulate the flow of gasses and fluids. All MFCs are designed and standardized to regulate a specific type of gas or liquid at a specific flow rate. An MFC can be set up at 0 to 100% range, but it operates best when in the 10 to 90% range. The best percentage of accuracy is achieved in this range. The device will control the flow rate at this given set point. An MFC device can be digital or analog. The advantage of using a digital MFC flow controller is that it is capable of controlling more than one type of liquid whereas analog controllers are limited by the liquid for which it was standardized.
All MFCs have an outlet and an inlet port, a flow sensor and a control valve. MFCs are fitted with closed loop control systems. An input signal is entered by an operator (a computer/external circuit) which it will use to compare the value from the flow sensor. It will adjust the proportional valve as required to achieve the desired flow rate.
Mass flow controllers are used in a wide range of industrial applications. Some key applications include LED production tools and semiconductor fab, biopharmaceuticals, chemical gas, and petrochemicals.
Liquid flow equipment controllers play an integral role in various industrial applications.