If you have an application where you have to measure the flow of a liquid with a high viscosity, you should consider installing an oscillating piston flowmeter. Learn about the advantages of our COVOL Series.
The oscillating piston flowmeters, a type of positive displacement flowmeter and sometimes called volumetric counters, are flowmeters especially indicated for high viscosity liquids, although they are also suitable for low viscosity liquids.
Let’s talk about Tecfluid oscillating piston flowmeters in particular…
Working principle of oscillating piston flowmeters
Its operation is based on the movement of a rotating piston, which with each turn fills and empties a chamber of a known volume.
Empty measuring chamber with rotating piston, starting to be filled and almost filled
The piston rotation activates a reed sensor, emitting a pulse that corresponds to the volume of said chamber emitiendo un pulso que se corresponde con el volumen de dicha cámara.
The output signal of this sensor can be treated by means of an electronic converter.
The oscillating piston flowmeters COVOL series are manufactured in different materials and with different types of process connections, including materials and fittings suitable for hygienic applications, and there are also special designs for high pressure.
What are the advantages of an oscillating piston flowmeter?
- Installation can be done either in horizontal and vertical position even inclined, it has bidirectional flow measurement and is suitable for all flow directions without affecting the flowmeter accuracy.
- Straight pipe run before and after the flowmeter is not required,it can be installed before or after disturbing elements of flow.
- The oscillating piston flowmeter is not very sensitive to changes in viscosity. So it is ideal for applications where the temperature is not constant.
- Under normal working conditions, it has a long working life. Normally it will not be necessary to change any part, but if required, the operation is simple and it can be done in few minutes.
Now is when you say: and what is considered as “normal working conditions”? 🙂
In Tecfluid, we consider that the duration of the components depends fundamentally on the combination of two factors:
- The abrasive characteristics of the application product (which must be compatible with the manufacturing material of the instrument).
- The operating flow rate. If the maximum flow of the DN of the instrument is exceeded, the rotating piston could be damaged.
- Unbeatable repeatability of ±0,3%
- High accuracy.
- It does not need power supply so it can be installed anywhere.
- Ideal for dosing applications.
Internal mechanism of an oscillating piston
flowmeter COVOL series
Oscillating piston flowmeter
stainless steel body
And disadvantages? (Which must also be considered)
- The liquid must be clean and free of suspended solids, which could jam and / or damage the rotating piston in the chamber and distort the flow readings.
In case that the application fluid has solids, it is essential that we install a filter before the flowmeter to prevent costly breakdowns.
- It has a relatively high pressure loss, the higher the viscosity of the liquid.
- The piping must always be completely filled, with no air pockets to avoid important reading errors.
Electronic devices/converters that can be associated to COVOL
Put yourself in situation: As this kind of flowmeter does not need power supply, you have installed the COVOL series oscillating piston flowmeter in an area of the factory where it is difficult to make a wiring installation. However (there is always a “but”) … you need to have two totalizers, one of them resettable, to have a record of readings from 0.
Is there any converter that you can install to be able to have these options? Well, you could use an electronic CIPII converter, although if your case is different we also have other options available.
The oscillating piston flowmeters COVOL series are very versatile. You can use them as they are, obtaining a pulse output by means of a reed switch that you can connect to your PLC or your own display, or you can use one of these electronic converters:
Polypropylene COVOL series flowmeter
+ CP420 converter
Stainless steel COVOL series flowmeter
+ CIPII converter
Electronic converter CP-CH420R model
for remote DIN rail installation
Electronic converter CP-CH420P model
for remote panel installation
Electronic converter MT03 model
for remote panel installation
Electronic converter DFD420 model installed in COVOL series oscillating piston flowmeter
This functionalities table will clarify to you when to use one electronic converter or the other:
Options for potentially explosive atmospheres
The oscillating piston flowmeters of Tecfluid are also suitable for installation in ATEX classified zones, that is, areas in which a potentially explosive atmosphere may be formed.
They have two different protection types:
- Exia protection.
When oscillating piston flowmeters include only the reed sensor and the connector, they can be considered “simple apparatus”, since they do not contain any source of ignition of their own. In these cases, they can be used in hazardous areas whenever a zener barrier or intrinsic safety isolator is installed.
The electronic converters of Tecfluid S.A., however, must always be installed in a safe area. If you wish, we have converter options for compact mounting with Exia certification. You can discuss this application with Tecfluid’s sales engineer, so you can solve any doubts you may have.
- Exd protection.
The COVOL belongs to group II, therefore it is intended for use in places where there is a risk of generation of an explosive atmosphere, (except in mining).
Being category 2GD it can be used in an environment where it is probable to generate an explosive atmosphere due to air and gases mixtures, vapours, mist and dust as well.
Four different types of Exd housings are available:
- ADF30 model: blind housing with reduced dimensions for pulse output.
- ADF40 model: blind housing for DFD420 converter.
- ADF60V model: housing with window to include CIPII or CP … CH420L converters.
- ADF60 model: same as ADF60V but with blind housing.
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Exd housing ADF60V model with CIPII display
Flowmeters of COVOL series DN50 with ADF60 housing
Most common applications of oscillating piston flowmeters
Applicable in all types of industrial processes, oscillating piston flowmeters are widely used in chemical and petrochemical industry, tank filling and batching applications, measurement of steam condensates in boilers and measurement of fuel consumption among many others… we are talking about purely mechanic equipment that can work with a viscosity of up to 120000 mPa·s
Oil mills: The COVOL series is especially indicated
for oil dosing
With an accuracy of ±0,8% of measured value and the possibility of total cleaning and being sterilisable, the oscillating piston flowmeters COVOL series are ideal for any type of liquid and have an excellent performance in changing process conditions.
Do you need more technical details about this type of flowmeters? Here you have them.
If you are thinking of using an oscillating piston flowmeter in your application and you have doubts, call us or contact with us. We help you to decide which the best option is.