FT221 Portable Ultrasonic Flow Meter

Common applications:

• Water (Hot water, cooling water, potable water, sea water etc…)
• Petroleum products
• Chemicals, including alcohol, acids, etc…
• Beverage, food and pharmaceutical processors
• Secondary sewage, waste treatment, etc…
• Mining industry, power plants for various processes
• Fire suppression system testing
• Pipeline leak detection and inspections
• Flow measurement surveys

If you are not sure if this model is well suited to your needs, please send us an email and describe your application and maybe even a photo of your proposed measurement site and mounting area and we might be able to indicate if the meter may be suited or possibly recommend a different type if necessary.

Suited pipe materials:

• You can select from the pre-configured pipe materials :
• PVC, Carbon Steel, Stainless Steel, Cast Iron, Copper, Ductile Iron, Aluminium, asbestos Cement, ACP, Fiberglass, or ‘other’
• If you have any other liquid, please select ‘other’ then in subsequent menus you can manually enter the fluid sound velocity of the material
  • Usually you can find various other pipe material sound speeds with a web search
• It will only work on ‘sound conducting pipe’, please be aware, there will be some pipes it cannot work on; HDPE is a common one that we are asked about which while it ‘can’ work, it will not work with very high thickness pipes, with HDPE – often the pipe wall thickness is so thick that the ultrasonic sound/signal cannot get through it properly.
• It’s difficult to say what ‘will’ and ‘will not’ work, you can try it – but thicker than around 20mm you may have signal issues.

Can be used on pipes with liners:

• It can also measure on pipes with liners when configured accordingly, you can select from the pre-configured liner materials: No liner, Tar Epoxy, Rubber, Mortar, Polypropylene, Polystryol, Polystyrene, Polyester, Polyethylene, Ebonite, Teflon, ‘Other’
• If you have any other liquid, please select ‘other’ then in subsequent menus you can manually enter the sound velocity of the material
  • Usually you can find various other liner material sound speeds with a web search

Suited liquids:

• It work’s only on clean liquids (not necessarily clear, so oil is okay for example) with little or no particles and entrained air bubbles.
• They will not work with too much suspended solids in the liquid, as a rough guide we typically advise around 5% suspended solids should be the cut off point, though it can vary between applications.
• You can select from the pre-configured liquids: Water, Water 125℃, Seawater, Kerosene, Gasoline, Fuel Oil, Crude Oil, Diesel Oil, Castor Oil, Peanut Oil, Alcohol, Propane (-45℃), Butane (0℃), Gas #93 (USA 93 octane), or ‘Other’
• If you have any other liquid, please select ‘other’ then in subsequent menus you can manually enter the fluid sound velocity and viscosity.
  • Usually you can find other fluid sound velocity and viscosity with a web search
  • Setting parameters accurate is important for an accurate measurement, If sound velocity is not known it’s possible to try using estimated figures, but be aware the further you are from the ‘true’ value the less accurate the measurement will be, or if very far from the ‘true’ value it may not measure at all.

General information:

• This is a ‘transit time’ flow meter. Transit time works on the principle of sending a sound signal up stream and then downstream from a pair of sending and receiving transducers. It measures time shift with and against the flow in calculating flow rate.
• When selecting a measurement site, it is important to select an area where the fluid flow profile is fully developed for an accurate measurement.
  • Choose a section of pipe that is always full of liquid (signal does not pass through air), such as a vertical pipe with flow in the upward direction or a full horizontal pipe.
  • On horizontal pipes it is best to mount the transducers on the side of the pipe. Avoid the top and bottom of the pipe to eliminate issue if air/gas has accumulated at the top of the pipe and sediment collected on the bottom of the pipe.
  • You want to measure where flow is stable and laminar, avoid turbulent areas. Generally, for best results a straight pipe run is required 10 pipe Diameters upstream and 5 pipe diameters downstream, but the recommendations vary depending on the situation, the datasheets have a section on this “installation site selection”
• You will need to know: Pipe outer diameter, pipe wall thickness (consider our GM-100 thickness meter), pipe material, liner details (if applicable), and what the liquid is, you set these parameters in the flow meter and it will give you a transducer spacing which is the distance to separate the sensors on the pipe.
• Included couplant (grease) is to be generously applied to the sensing area of the transducers, then you will need to mount the transducers on the pipe at that specified distance
• The mounting frames have an inbuilt magnet to aid in installation, chains are wrapped around the pipe and tightened down with the frame, then sensors are placed into the frame and clamped into position.
• Something else to note is ultrasonic flow meters are not ideally suited for intermittent flow duration’s (EG a pump powering for 20 seconds on and then flow off, or with diaphragm pumps for example)
  • The reason is that the signal typically will take at least a few seconds to stabilise and display accurate readings.
  • The flow meter has a ‘damping function’ (enabled by default) which will stabilize the flow display, a dampening factor of 3 to 10 seconds is recommended but could be set to 0 for it to much more quickly react to detected flow rate changes. It’s essentially an averaging filter.
  • They are also not suitable for accurate low dosing, or custody transfer applications as they will “miss” some of the totalised flow while the signal attenuates and the flow measurement ‘ramps up’ to it’s measurement accounting for the dampening function setting.

How does an ultrasonic flow meter work

An ultrasonic transit time flow meter utilizes two transducers that function as both ultrasonic transmitters and receivers. The transducers are clamped on the outside of a closed pipe at a specific distance from each other.  The transducers can be mounted in V-method in which case the ultra sound transverses the pipe twice, or with other methods in which case the ultra sound can transverse the pipe several times. The two transducers transmits and receives ultrasonic signals amplified by multi beam which travels firstly downstream and then upstream.

When liquid is flowing the ultra sound travels faster downstream than upstream, so there will be a difference of time of flight (△t). When the flow is still, the time difference (△t) is zero. Therefore, as long as the instrument knows the time of flight both downstream and upstream, it can work out the time difference, and then the flow velocity and flow volume with a formula it calculates automatically.