What is a Flowmeter?
A flowmeter is a device that is used when measuring gases and liquids that move through a pipe or line. Flowmeters are used in a variety of industries, including chemical processing, aerospace industries and also in laboratories. Some flowmeters measure the amount of liquid passing through it during a certain time period (i.e. 200 liters per minute) and others measure the total amount transmitted altogether.
Styles of Flow Meters
There are many flowmeters on the market, each of which are designed for specific applications and have their limitations. Choosing the right type of flowmeter for your company is essential, as they do not all measure in the same way and some are more accurate than others.
Flowmeters currently available include:
- Variable Flowmeters
- Turbine Flowmeters
- Positive Displacement Flowmeters
- Open Channel Flowmeters
- Mass Flowmeters
- Velocity Flowmeters
All of these meters come in various models, each with different design features that suit a specific industry, so it is essential that you do your homework when deciding what will do the best job for the requirements of your company.
The variable flowmeter gives readings that are taken by looking at the position of a float within a metering tube. The inferential measurements are given based on the linear function of the flow rate. This style of flowmeter is also known as a rotameter and is great value for money for businesses that cannot afford to spend a lot of money on certain types of equipment.
The variable flowmeter consists of a vertically oriented glass, in which the glass metering float can move freely within the pipe or line. As the fluid flows, the float will rise as the upward pressure differential reacts to gravity and the buoyancy is altered.
For all of you science lovers out there, here is the exact definition of flowmeter measurement works:
Q = A · v, which means that the volume of fluid passing through a flowmeter is equal to the cross-sectional area of the pipe (A) times the average velocity of the fluid (v); and
W = r · Q, which means that the mass flow of fluid passing through a flowmeter (A) is equal to the fluid density (r) times the volume of the fluid (Q).
You can expect a Turndown Ratio of up to 12: from a variable flowmeter and the accuracy can reach as good as 1% (full-scale rating). For alarm and transmission functions, magnetic floats can be used.
In terms of accuracy, the variable flowmeter may not perform as high as some other styles of flowmeter, but if you can function with up to 1% then this flowmeter will stand you in good stead.
The Benefits of Variable Flowmeters
- No moving parts
- Low maintenance
- Unobstructed flow passage
- No projecting parts
- No additional pressure drop
- Optimized measuring range
- Suited to hydraulic solids
- Unaffected by temperature and viscosity changes
- Can handle contamination
- Can cope with aggressive materials (chemical processing)
With variable flowmeters such as the 2600 Industrial Series, you can enjoy a meter that provides a direct-reading with a custom-engraved scale mounted adjacent to the metering tube. Design features like this can make life easier for businesses who want to achieve precise readings with no ambiguity.
Variable flowmeters are generally used for local indications of small areas of liquid or gas flow and are most popular in mineral processing, wastewater plants, chemical processing, the mining industry and in work using petrochemicals.
Disadvantages of Variable Flowmeters
- Only suitable for liquids (although some better models can be adapted for gases)
- Errors caused by gas inclusions
- Lower conductivity limits
- Sensitive to vibration
- Damage (to measuring heads) can be caused by solids
It is imperative that you use variable meters in the correct way and you should ensure that when used with fluids that are opaque or dirty as this will affect the meter flow readings.
Installation and Calibration
Installation of variable flowmeters is relatively hassle-free but you must ensure that a qualified handler installs your equipment.
The following actions must be taken in order to ensure that your flowmeter is safe to use and does the job that you want it to.
- When using liquid, you need to ensure that the variable flow has a full level during the installation process so that the accuracy is not affected.
- If you are a business that works with gases or vapors, you need to ensure that the variable meter is full and do not allow liquid inside that can alter the geometry.
- You need to be sure that you position the valves in a way that there are no disturbances in the flow that may affect the measurement and ensure that all piping has a straight run.
- Extra care needs to be taken when the flow is in two phases, i.e. liquid and solid flow or vapor and liquid flow as this may affect the preciseness of accuracy ratings.
When maintaining and calibrating your flowmeter, you need to check for any areas that may have become plugged, as this will eventually prevent the meter from working.
In terms of calibration, the pipes used for your business can be calibrated in units that are appropriate for your business and, like choosing a style of flowmeter, this will be dependent on your individual requirements.
Flowmeters comes in various designs and sizes and you cannot rely on a standard size that can be taken off a shelf when it comes to installing one for your business. Always get advice from a reputable flowmeter specialist to ensure that you do not make a costly mistake in buying the wrong piece of equipment for your business. In today’s competitive environment, the C-Suite network of every company is usually concerned with cutting costs and ensuring nothing affects the bottom line.
When purchasing your variable flowmeter, it is wise to ask the provider what their after-service offerings are, such as regular maintenance and calibration.
Different businesses will provide different services. This will ensure that you get the most out of your purchase in the long-term.