There are varieties of ways to measure volumetric flow that most engineers use, unlike mass flow measurement which is not widespread and understood. How to measure mass flow rates directly and highlight applicable features of certain mass flow meters available for business is what this article will be explaining.
Types of Electronic Mass Flow Meter
and Principles of Operation
The most used meter types are differential pressure flow meter ( DP flow meter), Coriolis flow meter and thermal mass gas flow meter
Differential Pressure Flow Meter for mass flow measurement
It involves using an obstruction like a disk that has a hole with a specific diameter that is placed inside a laminar flow region and then fluid pressure gets measured on both sides. There will be higher pressure on the upstream side, while the reading difference is considered in relation to whatever distance there’s between those 2 reading points, viscosity, pipe diameter and volumetric flow rate, according to setting as per Poiseuille’s equation. The corrections for pressure and temperature are done to come up with a mass flow rate that is standardized. DP flow meters are used together with electronic flow totalizer , which calucate the mass flow meter rate by flow rate , temperature and pressure information . Currently, Silver Automation Instruments develops balanced flow meter which is a kind of advanced DP flow meters and can be used in a lot of tough applications , such as high temperature or high pressure fluids flow rate measurement.
The Coriolis Mass Flow Meter to measure media mass flow
Measurement of mass using Coriolis mass flow meters
involves inertia. The process includes a dense gas or liquid flowing through a small actuator vibrated-tube. As it accelerates, it exerts a calculable twisting force that impacts the tube in proportion to the mass. The specification of the mass flow rate does not require any knowledge about the flow of the fluid inside. Electronic coriolis mass flow meter with digital display to show fluids mass flow, total flow , density value , it can also have frequency, 4-20mA, RS 485 communication , even with Hart Protocols .
Thermal Mass Flow Meter to measure gas mass flow
They come in two designs: These are inserted probe together with heated sample tubes. Their mass is generated based on the specific capacity of the fluid heat they have, hence negating variations in density. Thermal mass flow meters do well with low gas flow rates.
To use a thermal mass flow meter, consider that it may be influenced by the following:
Condensation of moisture on the temperature detector: Moisture may be generated by saturated gases, leading to bad readings and hence, corrosion.
Particulate accumulation: If the gas flow sensor is affected by residue accumulation, hindering heat transfer, it may result in low readings.
Specific heat capacity assumption error: This comes from gas composition variations.
Besides, it takes time for thermal mass flow meters to reach a state of steady operating temperature. So, readings must always be done later on and not once the device gets powered-up.Electronic thermal mass flow meters is standard with digital display , 4-20mA output , RS485 and pulse output, it is 24V DC or 220V AC power supply.
Though Coriolis mass flow meters are regarded as the most accurate, there’re prone to errors coming from bubbles in liquid. Such errors come with “splashing” inside the tube, which makes noise and changes the energy needed for the tube to vibrate. With large cavities, the required tube vibration energy increases exceedingly, leading to absolute failure. In addition, separating fluid to liquid as well as gas generates a hindering effect on the vibration of the tube
Thermal mass flow meters are suitable for gases and air flow measurement
. Their use is wide-spread in:
Filter & leak detection
Monitoring nuclear power facility air
Measurement of semiconductor process gas
Common additional applications used for thermal mass flow meters are laboratory analysis, like gas chromatography.
Being the most accurate and most costly technique, Coriolis flow meters are the predominantly used type of meter applied for scientific applications that involve measuring corrosive, gases and clean liquids. They also feature in:
Petroleum & oil
Meters used in pulp and paper processing are designed with a straight tube and cleaning them is more effortless. Hence, they are preferably used for beverage and food applications as well as pharmaceuticals. When it comes to handling slurries as in mining operations, they’re effective.
Indirect measurement of mass flow rates by differential pressure is possible likewise directly with a meter, applying the Coriolis-effect flow meter
. It can also work with specific heat capacity.
Coriolis mass flow meters make the highest accurate measurement for the highest number of liquids, however, they are expensive. The benefit of using them includes not requiring the knowledge regarding the fluid that is being carried.
Thermal mass flow meters are less accurate; however, they still employ a direct technique of measurement. They require knowledge about the specific heat capacity of the fluid.
The differential pressure flow meters produce an indirect measurement which comes from a derivation of Poiseuille’s equation and must be changed for fluid pressure as well as temperature. This is quite applicable in the case of incompressible fluid.
Silver Automation Instruments sell different type mass flow meters with electronic outputs and digital displays at low price cost, welcome to contact us to obtain the price.