If you have a standard Digital Flowmeter from EXAIR, you can convert it to a Wireless Digital Flowmeter. Making this conversion allows you to transmit you r compressed air data over a ZigBee mesh network. This data can be passed from meter to meter, which extends the distance the data can be transmitted. Each meter has a wireless range of 100′ (30meters). Once converted, a wireless to ethernet gateway transmits the data to EXAIR’s free graphing software. By Here is an informal video demonstrating this.
The Digital Flowmeter is available from stock for use on Schedule 40 pipe with sizes ranging from ½”-4” I.D. Sizes up to 8” for Schedule 40 and ¾”-4” for copper pipe are also available. Metric sizes are also available for 25mm, 40mm, 50mm, 63mm, 76mm, and 101mm. With a digital readout display, it’s easy to accurately monitor your compressed air usage throughout the facility. Creating a baseline of your usage will allow you to understand your compressed air demand, identify costly leaks, and replace inefficient air products.
The Digital Flowmeter installs in minutes with help from a drill guide and locating fixture to assist in mounting the Digital Flowmeter to the pipe. Two flow sensing probes are inserted into the drilled holes in the pipe. The meter then seals to the pipe once tightened. There is no need to cut, weld, or do any calibration once it is installed. With blocking rings also available, installation can be permanent or temporary. Below is a easy to follow video on how to install EXAIR’s Digital Flow Meter!
The newest addition to this product line is the Digital Flowmeter with wireless capability. Using a ZigBee® mesh network protocol, data is transmitted to an Ethernet connected gateway. This allows you to mount the Digital Flowmeter in areas that you may not be able to easily access and wirelessly monitor and graph the usage with the EXAIR Logger software. Take a peek at this video blog for a demonstration of the use of a wireless Digital Flowmeter software to compare an open pipe to an engineered Air Nozzle.
In addition to communicating wirelessly with the gateway, the Digital Flowmeters can “piggyback” off of each other to extend their range. Each meter has a range of 100’. Using multiple Digital Flowmeters within the same ZigBee® mesh network, data can be passed from meter to meter to extend the distance over which the meters can operate. These can be installed on each major leg of your compressed air system to continuously monitor usage throughout the facility.
If you’d rather go with a hard-wired data collection method, the Digital Flowmeter is also available with a USB Data Logger. Simply remove the Data Logger from the Digital Flowmeter and connect it to the USB port of your computer. The data can then be viewed directly in the accompanying software or exported into Microsoft Excel.
Two special flow meter options we now offer are the Pressure Sensing Digital Flowmeters, and the Hot Tap Digital Flowmeters!
Pressure Sensing Digital Flowmeters help by generating a pressure and consumption profile of a system can help to pinpoint energy wasters such as timer-based drains that are dumping every hour versus level based drains that only open when needed. Hot Tap Digital Flowmeters offer a way to install a flow meter on a pipe that is currently under pressure. It uses a series of valves and mufflers to maintain a safe working environment for the installer.
If you’d like to get a clear view of your compressed air usage, give us a call. An Application Engineer will be happy to work with you and get the proper Digital Flowmeters installed in your facility!
Fluid mechanics is the field that studies the properties of fluids in various states. Fluid dynamics studies the forces on a fluid, either as a liquid or a gas, during motion. Osborne Reynolds, an Irish innovator, popularized this dynamic with a dimensionless number, Re. This number determines the state in which the fluid is moving; either laminar flow, transitional flow, or turbulent flow. For compressed air, Re < 2300 will have laminar flow while Re > 4000 will have turbulent flow. Equation 1 below shows the relationship between the inertial forces of the fluid as compared to the viscous forces.
Re = V * Dh / u
Re – Reynolds Number (no dimensions)
V – Velocity (feet/sec or meters/sec)
Dh – hydraulic diameter (feet or meters)
u – Kinematic Viscosity (feet^2/sec or meter^2/sec)
To dive deeper into this, we will need to examine the boundary layer. The boundary layer is the area that is near the surface of the object. This could refer to a wing on an airplane or a blade from a turbine. In this blog, I will target pipes, tubes, and hoses that are used for transporting fluids. The profile across the area (reference diagram below) is a velocity gradient. The boundary layer is the distance from the wall or surface to 99% of the maximum velocity of the fluid stream. At the surface, the velocity of the fluid is zero because the fluid is in a “no slip” condition. As we move away from the wall, the velocity starts to increase. The boundary layer distance measures that area where the velocity is not uniform. If you reach 99% of the maximum velocity very close to the wall of the pipe, the air flow is turbulent. If the boundary layer reaches the radius of the pipe, then the velocity is fully developed, or laminar.
The calculation is shown in Equation 2.
d = 5 * X / (Re1/2)
d – Boundary layer thickness (feet or meter)
X – distance in pipe or on surface (feet or meter)
Re – Reynolds Number (no dimensions) at distance X
This equation can be very beneficial for determining the thickness where the velocity is not uniform along the cross-section. As an analogy, imagine an expressway as the velocity profile, and the on-ramp as the boundary layer. If the on-ramp is long and smooth, a car can reach the speed of traffic and merge without disrupting the flow. This would be considered Laminar Flow. If the on-ramp is curved but short, the car has to merge into traffic at a much slower speed. This will disrupt the flow of some of the traffic. I would consider this as the transitional range. Now imagine an on-ramp to be very short and perpendicular to the expressway. As the car goes to merge into traffic, it will cause chaos and accidents. This is what I would consider to be turbulent flow.
In a compressed air system, similar things happen within the piping scheme. Valves, tees, elbows, pipe reducers, filters, etc. are common items that will affect the flow. Let’s look at a scenario with the EXAIR Digital Flowmeters. In the instruction manual, we require the meter to be placed 30 pipe diameters from any disruptions. The reason is to get a laminar air flow for accurate flow measurements. In order to get laminar flow, we need the boundary layer thickness to reach the radius of the pipe. So, let’s see how that number was calculated.
Within the piping system, high Reynold’s numbers generate high pressure drops which makes the system inefficient. For this reason, we should keep Re < 90,000. As an example, let’s look at the 2” EXAIR Digital Flowmeter. The maximum flow range is 400 SCFM (standard cubic feet per min). In looking at Equation 2, the 2” Digital Flowmeter is mounted to a 2” Sch40 pipe with an inner diameter of 2.067” (52.5mm). The radius of this pipe is 1.0335” (26.2 mm) or 0.086 ft (0.026m). If we make the Boundary Layer Thickness equal to the radius of the pipe, then we will have laminar flow. To solve for X which is the distance in the pipe, we can rearrange the terms to:
X = d * (Re)1/2 / 5 = 0.086ft * (90,000)1/2 / 5 = 5.16 ft or 62”
If we look at this number, we will need 62” of pipe to get a laminar air flow for the worse-case condition. If you know the Re value, then you can change that length of pipe to match it and still get valid flow readings. From the note above, the Digital Flowmeter will need to be mounted 30 pipe diameters. So, the pipe diameter is 2.067” and at 30 pipe diameters, we will need to be at 30 * 2.067 = 62”. So, with any type of common disruptions in the air stream, you will always get good flow data at that distance.
Why is this important to know? In many compressed air applications, the laminar region is the best method to generate a strong force efficiently and quietly. Allowing the compressed air to have a more uniform boundary layer will optimize your compressed air system. And for the Digital Flowmeter, it helps to measure the flow correctly and consistently. If you would like to discuss further how to reduce “traffic jams” in your process, an EXAIR Application Engineer will be happy to help you.
The first step to optimizing compressed air systems within an industrial facility is to get a known baseline. To do so, utilizing a digital flowmeter is an ideal solution that will easily install onto a hard pipe that will give live readouts of the compressed air usage for the line it is installed on. There is also an additional feature that we offer on the Digital Flowmeters that can help further the understanding of the compressed air demands within a facility.
The Pressure Sensing Digital Flowmeters are available from 2″ Sched. 40 Iron Pipe up to 8″ Sched. 40 Iron Pipe. As well as 2″ to 4″ Copper pipe. These will read out and with the additional Data Logger or Wireless Capability options record the information. When coupled with the wireless capability an alarm can be set for pressure drops that give live updates on the system as well as permits data review to see trends throughout the day of the system.
Generating a pressure and consumption profile of a system can help to pinpoint energy wasters such as timer-based drains that are dumping every hour versus level based drains that only open when needed. A scenario similar to this was the cause of an entire production line shut down nearly every day of the week for a local facility until they installed flowmeters and were able to narrow the demand location down to a filter baghouse with a faulty control for the cleaning cycle.
If you would like to discuss the best digital flowmeter for your system and to better understand the benefits of pressure sensing, please contact us.