At present, all of our Transit-Time ultrasonic flow meters are used for liquid flow measurement and The measured pipe must be full water pipe. Transit time liquid flow meter often used in water supply plants, HVAC application, pharmaceutical factory, food factory, beverage industry, metallurgy industry and others. Our Transit-Time ultrasonic flowmeter can be divided into single channel ultrasonic flow meter, Dual-channel ultrasonic flow meter, multi-channel ultrasonic flow meter.
Single channel ultrasonic flow meter with one pair of clamp on or insertion sensors
Double channels ultrasonic flow meter with two pairs of clamp on or insertion type sensors
Multi-channel insertion ultrasonic flow meter with 4 pairs of insertion sensors
They are suitable for measuring relative clean liquids, liquid with less contains of solids, the accuracy can reach 1%, the accuracy of dual channel ultrasonic flowmeter can be up to 0.5%.
In chemical industry, water treatment, petroleum and other industries will use flowmeters to measure a variety of liquids, such as chemical liquids, tap water, industrial water, domestic wastewater and so on. And in medicine, food and other industries, they usually have strict standards in water quality for flow measurement , they need to measure the flow of pure water or ultra-pure water, pure water conductivity will be relatively low.
Why clamp on type transit time ultrasonic flowmeter is the best solution to measure pure liquid ?
Let me take some other types popular flow meter as comparison .
1. Electromagnetic flowmeter
The electromagnetic flowmeter is based on Faraday’s law of electromagnetic induction. It is used to measure the volume flow of conductive liquid with conductivity greater than 5μS/cm. It is an inductive meter for measuring the volume flow of conductive medium.
This meter can be used to measure the volume flow of strong corrosive liquid such as strong acid and strong base and homogeneous liquid-solid two-phase suspended liquid such as mud, pulp and paper pulp. Since the conductivity of pure water is only 0.055 μS/cm, much lower than 5μS/cm, it is obvious that electromagnetic flowmeters are not suitable for the measurement of this liquid.
2. Turbine flowmeter
Turbine flow meters use the mechanical energy of the liquid to rotate a rotor within the flow stream. The rotational speed is directly proportional to the velocity of the fluid traveling through the meter.
It can be seen that the turbine flowmeter is a contact flow measurement, and pure water have particularly high material requirements, so the main material must be used in the manufacturing of 316L, the use of sanitary clamp joint, production cost immediately increased a lot.
3. Vortex flow meter,Turbine flowmeter,PD flow meter
Vortex flow meters, often referred to as vortex shedding flow meters, use an obstruction in the flow stream to create downstream vortices which are alternately formed on either side of the obstruction. As these vortices are shed from the obstrction, they create alternating low and high-pressure zones that oscillate at particular frequencies directly proportional to the velocity of the fluid. The flow rate can be calculated from the fluid velocity.
Turbine flow meters for use with liquids have a relatively simple theory of operation, as a fluid flows through the tube of the flow meter it impacts upon turbine blades. The turbine blades on the rotor are angled to transform energy from the flowing liquid into rotational energy. The shaft of the rotor spins on bearings, as the fluid velocity increases the rotor spins proportionally faster. Revolutions per minute or RPM of the rotor is directly proportional to the mean flow velocity within the flow tube diameter and this relates to the volume over a wide range.
Positive displacement flow meters utilize two patented impellers (gears) to measure precise volumes of liquid that pass through the flow meter as the gears rotate. These flow meters are specifically designed to accurately measure thicker fluids such as resins, polyurethanes, adhesives, paints, and various petrochemicals.
They are contact type liquid flow measurement, so they will be in direct contact with the fluid, which will pollute the measured liquid.
4. Coriolis Mass Flowmeter
A Coriolis flow meter contains a tube which is energized by a fixed vibration. When a fluid (gas or liquid) passes through this tube the mass flow momentum will cause a change in the tube vibration, the tube will twist resulting in a phase shift. This phase shift can be measured and a linear output derived proportional to flow.
As the Coriolis principle measures mass flow independent of what is within the tube, it can be directly applied to any fluid flowing through it – LIQUID or GAS – whereas thermal mass flow meters depends on the physical properties of the fluid. Furthermore, in parallel with the phase shift in frequency between inlet and outlet, it is also possible to measure the actual change in natural frequency. This change in frequency is in direct proportion to the density of the fluid – and a further signal output can be derived. Having measured both the mass flow rate and the density it is possible to derive the volume flow rate.
Nowadays, this meter is just ok to measure 200mm or below diameter pipe, can not measure big diameter pipe; Morever, it is relatively large in weight and volume, not easy to handle.
For pure water flow measurement,you can choose flow meter based on the following standards.
1) To choose non invasive type water flow meter and no directly contact with the measured liquid to ensure the liquid is not contaminated ;
2) The flowmeter selected must be able to measure liquids with very low conductivity.
3) The installation and measurement data of flow meter shall not be affected by the diameter of the measured pipe.
External clamp on ultrasonic flowmeter is a kind of non-contact liquid flow meter, it can measure the pipe from 20mm to 5000mm, a wide diameter range of pipe, and can also be used to measure the liquids that is difficult to contact and observation. The accuracy is relatively high, almost no interference of various physical properties of the measured medium, such as strong corrosive, non-conductive, radioactive, flammable and explosive liquid and other problems. Therefore, for pure water measurement, we will first recommend the external clamp-on fluid ultrasonic flowmeter to measure.
Show some real cases for your reference .
Post time: Oct-26-2022