Volumetric flow rate and mass flow rate measurement
We know that the volume of a fluid can be affected by fluid temperature and pressure, while the mass of a fluid does not change with time, temperature, and pressure. The flow measurement values of commonly used flow meters, such as orifice plate flow meters, turbine flow meters, vortex flow meters, electromagnetic flow meters, rotameters, ultrasonic flow meters, and oval gear flow meters are volume flow rate flow meters. But for activities such as scientific research (lab flow meter), production process control, quality management, economic accounting, and custody transfer is generally need mass flow measurement. Using the volumetric flowmeter
to measure only the volume flow rate of the fluid often cannot meet people's requirements, and it is usually necessary to try to obtain the mass flow rate of the fluid. In the past, the mass flow could only be obtained indirectly through methods such as correction, conversion, and compensation after measuring the temperature, pressure, density, and volume of the fluid. With this measurement method, there are many intermediate values (which detect by industrial temperature sensor, pressure transmitter.,etc) , and the accuracy of mass flow measurement is difficult to guarantee and improve. With the development of modern science and technology, some metering methods and devices for directly measuring mass flow have appeared one after another, which has promoted the progress of flow measurement technology.
What are the types of mass flow meter?
At present, mass flow measurement methods can be divided into two categories:
Indirect mass flow measurement
The volume flow and density of the fluid are measured at the same time, and the mass of the fluid is calculated by the flow computer; or the volume flow, temperature and pressure of the fluid are measured at the same time, using the fluid density, temperature and pressure to calculate the mass flow by flow totalizers or flow computers. For example, we use vortex flowmeter, orifice flowmeter, differential pressure flowmeter to measure the volume flow of saturated steam or superheated steam, and then use PT100 temperature sensor and pressure transmitter to measure the steam temperature and pressure, after inputting the temperature and pressure value into the flow totalizer, the density of steam and the mass flow of steam are calculated. 4”, 6” 8 inch Vortex steam flow meters are often used to measure the mass flow of steam in that way.
Indirect measurement of mass flow requires multiple intermediate parameter measurements, and then calculations and corrections. Therefore, the cumulative error is relatively large. However, because it is the traditional method, users are more familiar with it and tend to use that method in some occasions where the measurement accuracy is not required very high; the temperature and pressure compensation method is still widely used in measuring the mass flow of gas under standard conditions.
Direct mass flow measurement
Which type of flowmeter directly measures mass flow rate? With the development technology of direct mass flow measurement, many types of direct mass flow meters have been produced. Such as calorimetric mass flow meters, impulse mass flow meters, differential pressure mass flow meters, and bi-turbine mass flow meters and Coriolis mass flow meters
. At present, Coriolis mass flow meters are mostly used. The fluid measurement directly reflects the mass flow value, and has nothing to do with the changes of the fluid's temperature, pressure, density and other parameters.
Coriolis mass flowmeter is a mass flow measuring instrument that uses a new measurement principle. It has developed rapidly since the early 1980s.
Coriolis mass flow meters can be used in petrochemical, chemical, pharmaceutical, paper, food and energy industries. They have been widely used in the detection and control of process and custody transfer measurement and other occasions. Highly valued by the measurement industry and welcomed by users, it is a new type of mass flow meter that is more advanced and has a rapid development trend in the world today.
Compared with traditional mass flow measurement methods, Coriolis mass flow meters have the following outstanding features:
(1) It can directly measure the mass flow of the fluid in the closed pipeline and directly obtain the mass flow signal (current, frequency or pulse). This measurement method does not require the measurement and conversion or correction of intermediate parameters, thereby improving the mass flow measurement accuracy. The measurement accuracy of the mass flow is high, the repeatability is good, and it can be in a relatively large turn down ratio.
(2) Coriolis flow meters are applicable to many tough fluids. It can be used as high viscosity flow meters or non-Newtonian fluids mass flow meters or liquid containing a small amount of gas. Coriolis flow meters can be used to measure dirty fluids, fluids with suspending solids or particles, so it can be used as slurry flow meter, mud fluid mass flow meters, paper pulp mass flow meters; Coriolis mass flow meters can be used in below applications: asphalt flowmeter, mud flowmeter, honey flowmeter, LPG flowmeter, ultra-low temperature/ Cryogenic flowmeter, latex paint flowmeter, honey flowmeter, polymer flowmeter, grease flowmeter, chocolate flowmeter, etc.In principle, the measurement accuracy of the Coriolis mass flowmeter can be approximately considered not to be affected by the fluids physical parameters and the flow state.
(3) There are no obstacles and moving parts inside the mass flowmeter sensor, so the reliability is high, the service life is long, and the amount of daily maintenance is small.
(4) In addition to directly measuring the mass flow of the fluid, digital mass flow meters can also directly measure the fluids density, temperature, the percentage of solids. It is an intelligent multivariable mass flow transmitter that can provide a variety of parameter display and control functions.
(5) Multiple mass flow meters sizes can be selected. We have micro mass flow meters for low flow applications, DN3, DN6, 1/8”, 3/8” and so on. Commonly used Coriolis flow meters dial sizes are 1”, 2”, 3”, 4 inch, 5 inch, 6 inch, 8” and 10” Coriolis flow meters.
(6) Electronic mass flowmeter, with current 4-20Ma output, pulse output, frequency output, 485 communications, HART, used for various control and output, batch control purpose.
(7) Mass flow measurement units: Kg/h, t/h
Mass Flow Meter price
How much does Coriolis mass flow meter cost? The price of Coriolis mass flow meters is much more expensive than volume flow meters. The price is related to the brand, the size of the flowmeter, and the function of the flowmeter. The price of Silver Automation Instruments Coriolis mass flow meter starts from US$2800.