FAQ’s about clamp-on ultrasonic flowmeters

FAQ’s about clamp-on ultrasonic flowmeters2022-06-02T14:52:22+00:00
How does a clamp-on ultrasonic flowmeter operate?2022-06-07T14:44:49+00:00

Veelgestelde vragen - looptijdverschil meetprincipe ultrasone clamp-on flowmeting U-F-M | Ultrasonic Flow Management

U-F-M | Katronic KATflow clamp-on ultrasonic flowmeters operate according the Transit-Time ultrasonic principle. This means that the transit time difference between the transmitted and received signal is measured by the two associated sensors. It is a more efficient way of determining flow than most other measurement systems providing an extremely accurate measurement.

The clamp-on sensors are installed on the exterior of the pipe. They receive ultrasonic pulses through the pipe wall. The fluid (or gas) flowing inside the pipe causes time differences, frequency deviations and phase separation in the ultrasonic signals. These are evaluated by the flowmeter and thus a very reliable measurement is achieved.

The main principle is that sound waves that go with the current flow are faster than those that go against the current. The difference in the flowtime of these signals is directly proportional to the flowrate of the fluid or gas.
With the help of electronics incorporated in the flowmeter, elements that can influence the measurement are compensated (for example flow profile, fluid type and tube material).

Which substances are suitable for ultrasonic flow measuring?2022-06-07T14:39:26+00:00

Our ultrasonic clamp-on flowmeters are suitable for measuring a wide variety of electrically conductive and non-conductive fluids, as well as liquid gases.

Depending on the industry, the fluids to be measured can range from water, waste water to beverages, liquid food, shampoo, vegetables and oils, hydrocarbon refrigerants and much more. Actually, there is no acoustically conductive liquid substance that our flowmeters cannot measure.

Alcohol, benzene, carbon tetrachloride, diesel, ethanol, ethyl alcohol, ether, formaldehyde, glycol, isopropanol, methanol, milk, naphtha, mineral and vegetable oil, coolant, tetra-chlorides, water, salt water, … This is just a small selection of all substances that can be measured with our flowmeters.

Which pipe materials are suitable for ultrasonic flow measurements?2022-06-03T08:29:54+00:00

A clamp-on ultrasonic flowmeter is suitable for all commonly known pipe materials, whether ferrous, alloy or plastic.
Ultrasound flowmeters also work on pipes with an inner lining, provided the pipe is acoustically conductive and there are no layers of air between the different pipe materials.

Steel, stainless steel, asbestos cement, aluminum, copper, brass, lead, gray casting, ductile iron, nickel, tin, titanium, glass, polyethylene, PVC, CPVC, acrylic, …
This is just a small selection of the pipe materials suitable for ultrasonic flow measuring.

What is the accuracy of ultrasonic flowmeters?2022-06-07T14:29:44+00:00

For volumetric flow measurements, our flowmeters can achieve an uncertainty of 1 to 3 % of the measured value depending on the specific application.

Uncertainty of approximately 0.5 % can be achieved with on-site process calibration.

In case of flow velocity measurements, the flowmeters achieve an uncertainty within 0.5 % of the measured value.

How to install a flowmeter?2022-06-07T14:07:59+00:00

The ultrasonic sensors are simply clamped on the exterior pipe surface. This is how our flowmeters can be installed without the need to break into pipelines. The sensors are fixed to the pipe using metal chains, straps or mounting rails. Additionally, coupling paste is applied to the bottom of the sensors to ensure an acoustically conductive connection to the pipe.

While particularly rough or pitted pipe surfaces may need cleaning with a file or suitable abrasive material, the sensors of our Katronic flowmeters can usually be installed without the need for surface preparation. Every instrument of the KATflow series is equipped with a Setup Wizard and an Audible Sensor Positioning Assistant, which guide you step-by-step through the installation process. As a result, it only takes minutes to install and set up the flowmeter and to obtain correct measurement data.

What is the required maintenance schedule for a flowmeter?2022-06-07T13:37:39+00:00

U-F-M | Katronic clamp-on ultrasonic flowmeters do not contain moving parts which could wear out. The sensor casings are manufactured from stainless steel and are not in contact with the flowing medium, which helps avoid corrosion. Therefore maintenance should not be necessary.

What range of pipe diameters can be measured?2022-06-07T13:27:28+00:00

U-F-M | Katronic clamp-on ultrasonic flowmeters can cover a pipe diameter range from 10 mm (0.4 inches) to 3 m (118 inches).

N.B. For non-standard applications we have special solutions available.

What are the standard sensor cable lengths?2022-06-07T12:32:43+00:00

The ultrasonic clamp-on sensors of the KATflow series come with a standard cable length of 2.5 or 5.0 meters depending on the specific sensor type. Additional extension cables of up to 100 meters can be ordered separately.

How to program a non-standard medium?2023-11-13T15:25:40+00:00

Most of our flowmeters have a library of standard flowmeter programmed into them. If the liquid to be measured is not in the list there are two things that can be done:

  1. Choose Water from the menu. This might seem unhelpful, but water has a good average set of values for the three main parameters that the flowmeter needs. Using water for a non-water based application may not be perfect, but can provide a setup that will allow the device to measure. N.B. river water, waste water, sewage water etc. are all Water; It is only the solid content that varies.
  2. If more accurate data is desired for the media parameters, select User from the drop-down list. The flowmeter will then ask for three sets of data:
    – Kinematic viscosity in mm²/s
    – Density in kg/m³
    – Medium C speed in m/s

The C-velocity of the medium is often an unknown data. In fact, it is the conduction speed of a liquid to ultrasound. There is an overview of non-standard media in the back of the manual for this purpose. If the data is not found there, please contact us for technical support and advice.

Please note that any manually entered liquid information is only applicable at that temperature.

Is calibration for specific pipes required?2020-12-15T16:27:19+00:00

Calibrations for specific pipes are not necessary. Entering the specific application parameters (e. g. pipe diameter, pipe material, type of fluid) into the flowmeter ensures the above stated accuracy. If additional accuracy is required, a process calibration can be carried out on site.

Do clamp-on ultrasonic flowmeters come with a calibration certificate?2022-06-07T12:15:41+00:00

Due to the ultrasonic measurement technology, there is no need to calibrate the flowmeters to achieve the above stated accuracy.
If you require calibration, this can be ordered for an additional charge. The certificate confirms that the supplied sensor and flowmeter combination is delivering measurements which are stated in the accuracy range.

Can ultrasonic flowmeters handle air bubbles and solids?2022-06-03T10:28:00+00:00

The clamp-on ultrasonic flowmeters from our KATflow series can measure the volume flow, even when the medium contains air bubbles or solids up to 10%.

Can ultrasonic sensors withstand moisture and sand?2022-06-03T10:21:40+00:00

All U-F-M | Katronic clamp-on ultrasonic sensors have a minimum protection of IP66. They are suitable for use on underground pipes and in open areas where they are exposed to rain.

Please note that it is possible to upgrade the sensors to IP68. This makes them suitable for underwater use.

How often should the coupling agent be replaced?2022-06-03T10:12:05+00:00

Once applied to the sensors during the initial installation, the acoustic coupling paste should not have to be replaced.

Please note : If the mounting point is exposed to extreme atmospheric conditions, we would recommend the coverage of the sensors to be checked once a year.

Can ultrasonic flowmeters measure liquid gas and air?2022-06-03T09:48:48+00:00

Both fluids and gasses can be measured with ultrasonic clamp-on flowmeters.

For more specific information, please visit our product pages.

Which units of measurement are available after a flow measurement?2022-06-03T09:20:27+00:00

Our clamp-on ultrasonic flowmeters can display the following data :

  • Volume of the flow : m3 / h, m3 / min, m3 / s, l / h, l / min, l / s, USgal / h (US
  • Quantity : gallons per hour, USgal / min, USgal / s, bbl / d (barrels per day), bbl / h, bbl / min, bbl / s
  • Flow velocity : m / s ft / s, inch / s
  • Mass flow : g / s, t / h, kg / h, kg / min amount
  • Volume : m3, l, gal (US gallons), bbl
  • Mass : g, kg, t
  • Heat flow : W, kW, Mw (only possible with the heat quantity measurement option on KATflow 230, KATflow 100 and KATflow 150)
How to measure in case of a disturbed flow?2022-06-03T09:07:47+00:00

Dual-channel flowmeters: for the best results under the worst of flow conditions.

One of the assumptions made when installing a flowmeter is that the instrument in a location where there is a stable and undisturbed flow. The reality is though that accessing such ideal measurement conditions is often difficult, or impossible. Disturbances in the flow profile could be caused by numerous things but generally are a result in a change to the pipe through which the liquid is flowing. This could be a change of angle or plane through bends, a change of diameter through a reducer or diffuser or some other process equipment such as a valve or pump. These changes in fluid condition cause the flow profile to shift with the point of maximum fluid velocity no longer being located in the centre of the pipe.

Localised flow profile changes resulting from these pipe modifications will cause problems for most flowmeters installed in the same area. The cause is that regardless of the measurement technique used, there is an assumption that the observed flow condition is happening at the point of fastest flow and that no other outside influences are in play. The initial question is therefore what can be done to identify when disturbances to the flow might be happening, and then secondly to offer an appropriate solution.

It should me mentioned at this point that certain measurement technologies are more immune to this effect than others. Coriolis flowmeters for example calculate flow and density based on the vibrations of the internal tubing within the meter body and as such are not constrained in the same way as other instruments. Users of clamp-on flowmeters, along with many other devices, need to take the flow condition into account looking at potential locations for meter installation.

In order to provide guidance in how best to do this, we recommand to download the document highlighting how dual-path ultrasonic flowmeters can be used to improve measurement results under non-ideal installation conditions.

Download the technical information sheet ‘Dual Path Measurement‘.

What should be done in order to measure on painted pipes?2020-12-16T11:46:14+00:00

If the pipe is painted, and the coating looks in good condition, there is no need to remove the paint in order to get a good measurement. Paint should only be stripped from a pipe if it is flaking or in poor condition, where there is obviously multiple layers of paint, or where measurement has been attempted but poor signal is seen.

How to check the flow in an installation that is in operation?2022-06-03T08:53:40+00:00

Flow measuring in an installation that is in operation

Occuring problems:Flow meten werkende installatie

  • Fluctuations in the suction pressure
  • Fluctuations in the discharge pressure
  • Fluctuations in the motor sound
  • Fluctuations in the motor rpm
  • Fluctuations in the measured sound level dBA as well as dBC

To solve this kind of problem, you have to collect as much measurement data as possible. Do keep in mind that there is always the chance that you need more information to check your initial measuring.

Install a clamp-on flowmeter to collect all the necessary flow details.

The next thing is to combine all measurement details and the related problem can be solved.

What is a bidirectional flowmeter?2022-08-01T08:19:15+00:00

Bidirectional flowmeters are ideal for systems containing a flow that needs to be measured in both directions. For example monitoring pump performance, measuring fluids in hydraulic circuits and for cooling systems.

What is the expected battery duration of a portable flowmeter?2023-11-13T13:55:40+00:00

Both the KATflow 200 and KATflow 230 operate for up to 24 hours in continuous operation on a full charge. The flowmeters should fully charge in twelve hours. The operating time of a portable flowmeter would decrease if the instrument is used intermittently.

The KATflow 230 is fitted with two 4-20 mA active outputs. If these are turned on battery life will decrease. The outputs should be disabled in the input/output menu if not in use.

If an extended operation we advice the KATflow 210. The instrument has several battery configurations available and can be operated in three different measurement modes intended to provide the longest possible measurement. Present estimates indicate that in its largest capacity the KATflow 210 should be able to provide datalogging for over three months.

All of the Katronic flowmeters can also be operated off mains power, providing continuous operation, even if only on a temporary basis. If either of the flowmeters are failing to meet the expected battery performance please contact us for additional advice.

For the battery life of our other portable measuring devices, check the technical specifications in the data sheets.

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