Compressed Air Flow Meter
A compressed air flow meter helps you see exactly where your compressed air is going and where it’s being wasted. For plants running compressors around the clock, even small leaks or inefficiencies can quietly add thousands to your energy bill every month. Accurate flow measurement lets you catch that waste early, verify the right amount of air is reaching the right point in your process, and protect both product quality and workplace safety. Instead of guessing at consumption, you get real data you can act on whether that means cutting energy costs, meeting compliance requirements, or simply keeping operations running smoothly.
With most liquid & gas flow measurement instruments, the flow rate is determined inferential by measuring the fluids velocity or the change in kinetic energy. Other factors that affect liquid flow rate include the liquid’s viscosity and density, and the friction of the liquid in contact with the pipe.
With the many variations of flow meter technology available it can be challenging to make a decision on which technology is right for the application. An important and perhaps overlooked question, is what the instrument is supposed to do versus what is it able to do?
Flow meters are very popular for measuring compressed air systems. Depending on where they are installed, flow meters can tell you the compressor output, system consumption, peaks and troughs as well as average usage. When used well, flow monitoring can help keep your system under control and highlight any unusual activity in your system.
Benefits of Flow Measurement and Monitoring :
- Improves Your Compressed Air System Efficiency
- Saves Energy and Costs
- Reduces System Maintenance and Hence Lowers Labour Costs
- Reduces Operating Costs
- Keeps You Informed About Your System Dynamics
- Identifies changes in system performance
- Alerts You During Increased Leakage or Consumption.
- Tracks Your Peak and Average Demand
We Offer 3 Different Technologies in Flow Measurement for Gases and Liquids.
Thermal Mass Flow Meter
Thermal Mass Flow Meters measure the Gas Mass Flow Based on Thermal Diffusion Theory. It has two RTDs as its sensors, one of which sense the velocity of the Gas Flow (RH) and the other one will detect the temperature shift of the Gas Flow (RMG) . When the two RTD are in the Gas Flow ,the RH will be heated while the RMG will sense the temperature changing of the Gas Flow. More heat will be taken away as the velocity of the Gas Flow increases, so the temperature on RH will decline
Wise Air WAFS Series Thermal Mass Flow Meters are specially designed for Air and N2 applications. It has more compact design, which means smaller enclosure and thinner insertion tube probe. Due to its small diameter insertion probe and shorter high-sensitive sensor, it can be used on pipes from DN25~DN500, or even larger pipe. In some higher pressure applications, it can be installed / removed without stopping the fluid, as the pipe is thinner, field engineers will be able to insert the meter to pipe very easily. Also, to full-fill the Energy Conservation Need in Compressed Air and N2 applications, WAFS Series Thermal Mass Flow Meters will be the most Cost Effective model in the market.
Process Connection
The WAFS Series Thermal Flow Meters have two different installation types, one is insertion and the other is in-line type.
The insertion type can be installed and maintained on line. To install it, you have to weld and install a socket with screw thread outside on the pipe and install a 1 inch or 1/2 inch ball valve on the base. Then drill a hole of 13mm (or 22mm) diameter on the pipe with a special tool and install the Flow meter on the pipe through the hole. The position and depth of how the sensor is fixed have already been set before delivery.
The fitting in diameter of pipe for insertion type: DN25～ 900mm (Please make sure to let us know if you need it for larger diameter)
The In-line type is delivered along with a pipe which has a same inner diameter as the pipe in field. Is should be installed through flange or screw thread. The flanges meet GB/T9119-2000 standard（or ANSI B16.5 or DIN or JIS standard. The in-line type can fit in pipe with diameter from DN15mm to DN300mm. Or customer can simply choose to use a 3-way pipe to replace the flanged body
Sensor is made in 316 stainless steel and the pipe is made in 304 or 316 stainless steel. If users need them to be made in different material, please let us know before confirming the order.
Special Design
Anti Ejection Design
In some High Pressure Applications, there is a risk that when the pressure is too high, the nut sleeve will fail or be loosened unintentionally and the Flow meter will be ejected out and cause damage or injury. In Our WAFS Series insertion Thermal Mass Flow Meter the sensor base is wider than the nut sleeve and hence as long as the sleeve is still fixed on pipe with thread, the meter will not be totally ejected out even when used in High Pressure Applications.
Ball Valve Mounting
When users want to replace or re-calibrate or for any reason want to remove the Flow meter without stopping the Flow in the pipeline, our ball valve mounting can help. Once the meter is installed with a customized ball valve, user can remove the meter away while still keeping the pipeline sealed with the ball valve.
This design should only be used when it is absolute necessary and the fluid is not explosive or hazard.
Online Drilling
Some user may not want to stop the Flow when installing the Flow meter. With the help of our Online Drilling Kit the required provision can be made without plant shutdown.
The Online Drilling Kit can help you drill a hole for inserting the Flow meter without stopping the Flow. It will work with a ball valve. And after drilling and removing the tool , the pipe will be totally sealed.
Differential Pressure Pitot Tube Flow Meter
Differential pressure Pitot tube Flow Meters use Bernoulli’s equation to measure the flow of fluid in a pipe. Differential pressure pitot tube Flow Meters introduce a constriction in the pipe that creates a pressure drop across the Flow Meter. When the flow increases, more pressure drop is created. Impulse piping routes the upstream and downstream pressures of the Flow Meter to the transmitter that measures the differential pressure to determine the fluid flow. Differential Pressure Pitot tube flow meters are ideally suited to wet, dirty and high velocity gases. The extremely sensitive differential pressure measurement allows this sensor to be used over a wide flow range. The patented anti condensation technology enables the sensor to be used under saturated conditions and ensures the sensor will perform stable accurate measurements for years to come .Pitot tube flow sensor measure the upstream dynamic pressure and downstream static pressure. The pressure differential is a measure of the velocity and flow rate.online auto-calibration technology, high reliability, long-term measurement and accuracy can be guaranteed .Pitot flow meters are widely used in industrial processes, chemical, petrochemical, power engineering, etc.Pitot Tube flow meters are ideal for both temporary or permanent installations.
Ultra Sonic Flow Meter
Ultrasonic Flow ,Meters use sound waves to determine the velocity of a fluid flowing in a pipe. At no flow conditions, the frequencies of an ultrasonic wave transmitted into a pipe and its reflections from the fluid are the same. Under flowing conditions, the frequency of the reflected wave is different due to the Doppler effect. When the fluid moves faster, the frequency shift increases linearly. The transmitter processes signals from the transmitted wave and its reflections to determine the flow rate.
Transit time ultrasonic Flow Meters send and receive ultrasonic waves between transducers in both the upstream and downstream directions in the pipe. At no flow conditions, it takes the same time to travel upstream and downstream between the transducers. Under flowing conditions, the upstream wave will travel slower and take more time than the (faster) downstream wave. When the fluid moves faster, the difference between the upstream and downstream times increases. The transmitter processes upstream and downstream times to determine the flow rate.
Which flow meter for which job
WiseAir manufactures four measurement principles because no single one suits every duty. The choice is decided by the fluid, the pipe size and whether you can shut the line down to install.
| Model | Principle | Fitting | Suits |
|---|---|---|---|
| WAFS 103 | Pitot tube | Insertion | Compressed air on larger mains where a differential-pressure method is preferred and cost matters. |
| WAFS 103D | Pitot tube, bi-directional | Insertion | Ring mains and interconnected headers where air can flow either way and you need to know which. |
| WAFS 104 | Thermal mass | Insertion, DN20 to DN1000 | The workhorse for compressed air. Fits through a 1/2 inch ball valve under pressure, so no shutdown is needed. |
| WAFS 105 | Thermal mass | Inline, DN15 to DN80 | Smaller lines and branch drops where an inline body gives the best accuracy and straight-run behaviour. |
| WAFS 106 | Thermal mass | Insertion | General industrial air and gas duties. |
| WAFS 107 | Thermal mass | Insertion | Air service where a simple, robust installation is the priority. |
| WAFS 108 | Thermal mass, compact | Compact | Machine-level and point-of-use measurement where space is tight. |
| WAFS 1102 | Vortex | Inline | Steam, and gas or liquid duties outside the range of a thermal instrument. |
| WUFS 904 | Ultrasonic, clamp-on | Clamps to the outside of the pipe | Liquids where the line cannot be broken into at all. |
| WUFS 905 | Electromagnetic | Inline | Conductive liquids such as water and effluent. |
Insertion or inline? The decision that matters most
For compressed air this is usually the only real choice to make, and it comes down to your pipe size and whether you can stop production.
Insertion instruments such as the WAFS 104 are fitted through a tapping in the pipe wall. On DN20 to DN1000 the sensor goes in through a 1/2 inch ball valve while the line stays pressurised, which means no shutdown, no pipe cutting and no lost production. On anything above about DN80 this is the sensible choice, and on a live plant it is often the only practical one.
Inline instruments such as the WAFS 105 replace a section of pipe, in sizes from DN15 to DN80 with threaded or flanged connections. Because the full bore is defined by the meter body rather than by your pipe, the flow profile is known and the measurement is less sensitive to what is upstream. On small lines and branch drops it is the better instrument — but it needs the line down to fit.
A practical rule: measure the main with an insertion meter so you can install it without stopping, and measure individual departments with inline meters when those branches are next opened up for other work. Trying to fit inline meters on a live main is how projects stall.
Why two meters on the same system disagree
Almost every disputed flow reading we are called about comes down to one of four things, and none of them is instrument accuracy:
- Not enough straight run. Thermal insertion meters need roughly 15 pipe diameters of straight pipe upstream and 5 downstream. Fitted two diameters after an elbow, the sensor sits in a distorted profile and reads whatever that distortion produces.
- Different reference conditions. One meter reporting Nm³/hr at 0 °C and another reporting Sm³/hr at 20 °C will differ by about 7 percent while both are correct. Our free flow unit converter settles this in seconds.
- Actual versus normal volume. A meter reading actual m³/hr inside a pressurised pipe reads roughly one eighth of the free-air figure at 7 bar(g). Thermal mass meters report normal flow directly, which is why they avoid this argument entirely.
- Insertion depth and orientation. An insertion probe set to the wrong depth is measuring the wrong part of the velocity profile.
What every WiseAir flow sensor gives you
Across the thermal mass range the instruments report standard flow, mass flow, cumulative consumption and temperature from one device, with an RS485 Modbus RTU interface and a 4–20 mA current or pulse output. There are no moving parts, so there is nothing to wear, and the signal is stable under vibration.
Cumulative consumption is the output that changes behaviour. A flow rate tells an engineer what is happening now; a consumption total tells a finance team what a department used last month, which is what makes departmental accountability for compressed air possible.
Frequently asked questions
Which flow meter is best for compressed air?
A thermal mass meter, in almost all cases. It measures mass flow directly, so it is unaffected by changes in pressure and temperature, and it reports in Nm³/hr without correction. Choose insertion for larger mains and inline for small lines.
Can a flow meter be installed without shutting down the plant?
Yes, with an insertion type. The WAFS 104 installs through a 1/2 inch ball valve under pressure on DN20 to DN1000 lines. This is the usual reason insertion meters are specified on existing plants.
How much straight pipe does a flow meter need?
As a working rule, 15 diameters upstream and 5 downstream for a thermal insertion meter. Less than that and the reading reflects the disturbance rather than the flow. If the run is not available, tell us at the enquiry stage — the meter choice and mounting position can often be adjusted to suit.
What is the difference between Nm³/hr and CFM?
They are the same quantity in different units, but the reference conditions differ. One Nm³/hr is about 0.589 CFM on a normal basis, or 0.622 against US SCFM. Use the flow unit converter to convert between all of them, including actual to normal flow at your line pressure.
Do I need a flow meter if I already have a compressor controller?
The controller tells you what the compressor is doing. A flow meter tells you what the plant is taking, which is a different number as soon as leaks and storage are involved. Comparing the two is how most leak problems are first quantified — see the leak cost calculator.
Which model is right for your system?
Selection depends on pipe size, pressure, flow range and how the data needs to reach you. Tell us your application and we will shortlist the models that fit and send the datasheets.
Prefer to talk? Call +91 90477 78715. Working out whether it pays? Try the savings and ROI calculator or the leak cost calculator.
