Mass Flow Meter, also known as an inertial flow meter is a device that measures mass flow rate of a fluid traveling through a tube. The mass flow rate is the mass of the fluid traveling past a fixed point per unit time. Coriolis mass flow meters can detect the flow of all liquids and gases which can be used used for the food and chemical industry.
The Mass Flow Meter does not measure the volume per unit time (e.g., cubic meters per second) passing through the device; it measures the mass per unit time (e.g., kilograms per second) flowing through the device.
Coriolis mass flow meters can detect the flow of all liquids and gases which can be used for the food and chemical industry
- Design Pressure: 1200 PSIG
- Design Temperature: -282 to 300 Deg. C
- Sizes: 1/2″ to 4″ but larger sizes are customized.
- Fluids/ Applications: Liquids (clean/ dirty/viscous/ slurries) clean /liquified gases
- Flow range: 0 – 4,500 GPM
- Material of tube: Mostly in stainless steel, other options
- Accuracy is +0.1% to +0.5% of flowrate
- Range ability is 20: 1
- Bi-Directional flow measurement
- Measured variable: Mass flow, volume flow, temperature and density.
- Output: Pulse, 4~20mA, RS485, HART, 0-10VDC (Optional)
- Power supply: 85~265VAC or 18~36VDC
Advantages of Coriolis Flow Meter:
- Capable of measuring difficult handling fluids
- Independent of density changes, flow profile and flow turbulence. Hence straight lengths are not required.
- No routine maintenance required since no moving parts
- High accuracy
Disadvantages of Coriolis Flow Meter:
- Not available for large pipes
- High flow velocities required for detection resulting in high pressure drop
- Expensive compared to other flowmeters
- Difficulty in measuring low pressure gases
Technical Side of the Coriolis Flow Meter:
Volumetric flow rate is the mass flow rate divided by the fluid density. If the density is constant, then the relationship is simple. If the fluid has varying density, then the relationship is not simple.
The density of the fluid may change with temperature, pressure, or composition, for example. The fluid may also be a combination of phases such as a fluid with entrained bubbles.
The Actual density is due to dependency of sound velocity on the controlled liquid concentration.
What happens to the Fluid?
Fluid is being pumped through the coriolis flow meter or mass flow meter. When there is mass flow, the tube twists slightly. The arm through which fluid flows away from the axis of rotation must exert a force on the fluid, to increase its angular momentum, so it bends backwards.
Curved Mass Flow Meters:
curved tube mass flow meters are designed where the fluid is led through two parallel tubes. The actual frequency of the vibration depends on the size of the mass flow meter, and ranges from 80 to 1000 Hz.
When no fluid is flowing on a coriolis flow meter, the motion of the two tubes is symmetrical, as shown in the left animation.
What happens to Coriolis Flow Meter during mass flow:
- Some twisting of the tubes
- The arm carrying the flow away from the axis of rotation must exert a force on the fluid to accelerate the flowing mass to the vibrating speed of the tubes at the outside (increase of absolute angular momentum), so it is lagging behind the overall vibration.
The arm through which fluid is pushed back towards the axis of movement must exert a force on the fluid to decrease the fluid’s absolute angular speed.
The inlet arm and the outlet arm vibrate with the same frequency as the overall vibration, but when there is mass flow the two vibrations are out of sync: the inlet arm is behind, the outlet arm is ahead.
The two vibrations are shifted in phase with respect to each other, and the degree of phase-shift is a measure for the amount of mass that is flowing through the tubes.
Coriolis Flow Meter Economics:
These mass flow meters provide short payback periods on applications where measurement accuracy lowers production costs. They also have a short payback when multiple measurements (including density, temperature, pressure) are needed.
On the other hand, they may not be competitive when used in simple flow measurement applications. Where volumetric sensors are sufficient and where repeatability is more important than precision other type like Micro Mass Flow Meter, Turbine, Electromagnetic, Variable Area, Ultrasonic and Vortex may be the preferred choice.
Coriolis mass flow meters can detect the flow of all liquids and gases which can be used for the food and chemical industry and are the best choice for an accurate flow meter.