What is a Flow Indicator?
The term “flow indicator” is used for a few different elements in the industrial instrumentation world. It is helpful to be aware of the differences because if you don’t understand them, it can make finding the right device for your needs more difficult.
The most traditional usage of the term “flow indicator” is to refer to a device that does not measure the flow rate. Nor does it monitor the flow rate in the sense that it can provide switching capabilities. It simply provides verification that flow is occurring. In essence, it answers the question “is flow happening, yes or no?”. It generally does not provide any data on the flow, although most models enable direct viewing of the media inside. KOBOLD uses the term “flow indicator” to refer to this class of flow instrumentation.
Another usage of the term “flow Indicator” would more accurately termed as a “flow meter with a mechanical indicator”. This is a flow meter that does provide the measurement of flow rate and displays the rate on a mechanical indicator. Typically, these are pointer “arms” that are on a pivot point that rotate up with an increase in the flow rate. A corresponding scale is on the faceplate and the pointer arm points to the flow rate on the scale.
Another usage of the term “flow indicator” can be a flow meter that also provides a visual indication of the flow. These are typically variable area flow meters, also known as rotameters, that employ a clear glass or plastic tube and an internal float as the measuring principle. Because the tube is transparent, the flow can also be verified visually as you can see if the float has been moved up in the tube and is no longer seated at the bottom of the tube, as it would be if there was no flow present. Certain variable area flow meters can also give an indication of the flow conditions as well because the media can be seen through a sight glass.
Sometimes the term “flow indicator” is used interchangeably with the term “flow meter” because the flow meter provides an “indication” of the flow rate either through mechanical, digital, or other output means. This is not as common of a usage for the term.
What Does a Flow Indicator Do?
For purposes of our discussion and how we classify our products, we will be using the term “flow indicator” for the devices that simply let us know if flow is occurring. Flow indicators signal if flow is occurring within the piping system as most piping systems are not transparent to allow direct observation. Verifying flow requires a mechanism of some kind that is inserted into the piping system as a “window” and provides a visual cue as to what is going on inside.
How Does a Flow Indicator Work?
How a flow indicator works depends on which manner of indication that it is providing. All types of flow indicators function on the same simple principle. Flow through the devices generally moves something or sometimes nothing, in the case of a simple sight glass. Typically, the flow moves a ball or spins a paddle wheel. Flaps, chains, and other less common moving mechanisms are also used. If no mechanism is present at all, then the flow can still be verified by looking closely at the glass tube to see if there is flow happening. The advantages to a flow indicator with a moving mechanism is that they can be seen from much further away.
How Do You Read a Flow Indicator?
Unless you are using the term “flow indicator” to refer to a “flow meter”, you do not “read” a flow indicator. You can view it to see if flow is occurring, but there is nothing to “read” as an indicator does not provide a flow rate measurement to “read”. You typically view a flow indicator for indication that flow is occurring by verifying movement of the indication mechanism.
What is the Difference between Flow Indicators, Flow Meters, Flow Transmitters, Flow Switches, Flow Sensors, and Flow Restrictors?
Now that we have seen the different ways that the term “flow indicator” can be used, it is worth noting the other classes of flow instrumentation to ensure that you are searching for the right type of flow instrumentation.
To help further clarify which type of instrumentation is needed for your application, below is a general listing of most flow instrumentation, from simplest to most complex, with a brief description.
- Flow Restrictor: A flow restrictor simply restricts the rate of flow within a system to a predetermined amount. It cannot provide flow measurement.
- Flow Sensor: This term is more of a general catch-all terms for flow instrumentation because they all sense flow, to one degree or another. The term “flow sensor” is sometimes used interchangeably with any of the terms above, but really should be used as more of a general term for the entire class of instrumentation.
- Flow Indicator: They show that flow is happening. They answer the question, “Is flow happening at all, yes or no?”. Most models allow a clear view of the media as well.
- Flow Switch: They monitor the flow and trigger an electrical impulse at a certain rate of flow within the system. They do not provide continuous measurement unless the flow switch is part of a full flow meter. They answer the question, “is the flow too high, too low, or happening at a specific point?” or they trigger a specific action in the system. Some flow switches, like variable area flow switches, can also allow for direct viewing of the media as well through a plastic or glass tube.
- Flow Transmitters: These measure the rate of flow in the system and provide the measurement as an electrical output. Some flow transmitters may be fitted also with integral displays, controllers, or totalizers. Typical flow transmitters are sometimes referred to as “blind transmitters” because looking at the device tells you nothing, unless it connected to something that can interpret the signal produced by the transmitter. They answer the question, “how much flow is happening right now”.
- Flow Meters: These also provide a continuous measurement and are somewhat erroneously used interchangeably with “flow transmitter”. These devices also provide continuous measurement, but the rate can typically be seen directly at the device itself by a mechanical or digital means. They can also have integral switches. Some flow meter technology types allow for direct observation of the media as well. They can also have integral electronics that enable batching functions, where a precise amount of a media is dispensed. They can also have totalizers that tell you how much media has flowed in a certain period of time or for the total life of the instrument. They also answer the question, “how much flow is happening right now”, and provide many other features.
Other “Flow Indicator” Misnomers: When You Really Need a “Flow Meter” and not an “Indicator”
- Flow Indicator with Controller If you are looking for a “flow indicator” with controller, you will have more success looking for a “flow meter with controller”. ”Flow indicator”, in this sense, is a bit of a misnomer. You can view our comprehensive line of flow meters here.
- Flow Indicator with Totalizer If you are looking for a “flow indicator with a totalizer”, again, you are really looking for a “flow meter with totalizer”. Flow indicators do not measure, so they cannot totalize. You can view our comprehensive line of flow meters here.
- Flow Indicator Transmitter If you are looking for a “flow indicator with a transmitter”, the better terminology would be “flow transmitter” or “flow meter transmitter”. You can view our comprehensive line of flow meters here.
- Magnetic Flow Indicator The usage of the term “magnetic” is suggesting again that the actual device that is needed is a flow meter and not a flow indicator. Simple flow indicators are not made in magnetic flow technology as it would be expensive overkill if all that needs to be known is if flow is happening or not. Magnetic flow meters are a type of flow meter that use no moving parts or mechanical means to provide flow measurement. You can view our comprehensive line of magnetic flow meters here.
- Volume Flow Indicators Because flow indicators do not provide a flow rate, either volumetric or mass, it is likely that the type of device needed is a flow meter and not an indicator. Flow meter technology types that operate by a volumetric principle of measurement are all the flow meter technologies with the exception of thermal dispersion and Coriolis flow meters.
- Ideally it is best if the pipe remains full so that it properly engages the indication mechanism.
- Vertical flow up is an ideal installation as this orientation ensures a full pipe during flow.
- Suddenly starting the inflow may cause pressure peaks exceeding the working pressure of the instrument. This could cause damage to the indicator.
- Remove any coarse foreign matter before installing the instrument in the pipe.
What are Sight Flow Indicators?
Sometimes referred to as “sight glass flow indicators”, sight flow indicators do exactly what their name states. They enable sight of the flow, usually through a glass tube or a glass window. Sometimes “sight flow indicators” refer to indicators that have an integral mechanism to clearly display flow is occurring, and sometimes they refer to clear glass tubes or windows that simply allow the media to be seen. This is really a general term for the entire class of “flow indicators” as all indicators indicate flow is occurring by something being seen by the user. You can view our sight flow indicators here.
Our most popular sight flow indicator, the DAA Sight Flow Indicator, which has an integral cleaning mechanism, is an industry standard and comes with either a high visibility red paddle wheel for indication or without any mechanism at all. Our unique design features a mechanism that can remove periodic build up of media contaminants by simply twisting the device. It requires no system shut down or line removal to maintain and is made in the USA.
Can Flow Indicators Handle High Pressures?
Most standard pressure capability flow indicators are a combination of a metal and/or glass housing and typically employ a plastic means of indication within the line. The metal used is typically brass or stainless steel.
High pressure applications require a more rugged build to handle higher pressures. This requires higher-pressure capability metal, glass, and seals. It also requires a more durable flow indication mechanism than the plastic indication elements of lower pressure flow indicators.
We offer high pressure sight flow indicators and would recommend the DA High-Pressure Sight Flow Indicators which are of a heavy-duty industrial grade build for pressures up to 580 PSIG with a variety of indication mechanisms.
Our other flow indicators offer pressures up to 230 PSIG or 85 PSIG. To see if any of these indicators may fit your needs, visit our flow indicator line.
What are Paddle Wheel Flow Indicators?
Probably the most common type of flow indicator, a paddle wheel flow indicator, employs a paddle wheel to indicate flow. The same simple technology is also used in paddle wheel flow meters, except in paddle wheel flow meters, flow rate is provided by measuring the speed of the paddle rotation. Depending on the model of paddle wheel flow indicator, visual flow indication can also be provided by a paddle wheel flow meter.
Although no flow measurement is provided by a paddle wheel flow indicator, the speed of the turning wheel can very, very roughly indicate whether the flow is low or high by observing the speed at which the paddle is revolving around its axis. Visit our product page to learn more about the paddle-wheel flow indicators that we offer.
What is a Rotameter Flow Indicator?
Rotameter technology is also referred to as “variable area” technology. Simple flow indicators are not usually created in variable area technology. Most variable area flow devices are flow meters and not indicators, although variable area flow meters provide visual flow indication if they are built with a translucent tube that houses the float. Because the only extra step needed to create a flow meter out of what would be a “rotameter flow indicator” is a scale printed on the glass tube by which the top of the float can be read against for a flow rate, most variable area devices are flow meters.
KOBOLD carries one of the industries largest lines of rotameter variable area flow meters and many of our meters also provide visual indication of flow via the float movement in the glass tube. We also provide low-flow flow meters in variable area technology. Visit our article to learn more about rotameters or view our rotameters.
What are Water Flow Indicators?
Most liquid flow indicators are compatible with water and can be used as water flow indicators. Besides the general application parameters such as pressure and temperature, the other consideration to be aware of when choosing a water flow indicator is accounting for the characteristics of the water in the system.
Is it clean, ultra-pure, dirty, or mixed with other media that causes it to be aggressive or viscous? These factors can determine the suitability of certain models of flow indicators for a specific water application. To see which of our water flow indicators are compatible with different kinds of water, view our flow product comparison page or speak with one of our knowledgeable engineers.
What are Air Flow Indicators?
Most gas flow indicators are suitable for use as air flow indicators. To determine whether an air flow indicator is right for your application, make sure that it meets the pressure and temperature requirements of your system and pay attention to whether or not the air has any characteristics that could damage the visual indication mechanisms, such as large particulate matter that may be carried in the air flow stream.
Our suggested air flow indicator is our DKB Air Flow Indicator that offers indication via a ball mechanism.
What are Water Cooling Flow Indicators?
Water cooling systems protect expensive equipment by removing heat produced by the process by transferring it to water and moving the water into a cooling process where the temperature is reduced and then the cooled water is sent back to reduce the heat once again. Without proper water flow, the system can become compromised and cause a lot of costly damage. Flow indicators can be used in various parts of the process to verify flow.
Flow meters or flow transmitters, go one step further than a flow indicator and provide a continuous rate of flow. They are an even better safeguard for water cooling systems as they can offer more information and they can control functions that a simple flow indicator cannot.
For example, a flow meter would be able to detect leaks by sensing a significant unexpected drop in the flow rate. Flow meters also offer more automation to the process because they can transmit the data to control centers for continuous monitoring. A simple flow indicator usually requires on-site visual confirmation of flow.
Flow meters can also provide switching options, that in tandem with the pumps in the system, can keep the flow rate steady to enable consistent cooling to the process. For a simple water-cooling flow indicator, we recommend the DA Industrial Flow Indicator.
Can Flow Indicators Be Used with Liquid Fertilizer?
Because flow indicators typically only use a mechanical means to indicate flow and no electrical components are part of the device, most any liquid flow indicator can be used as a liquid fertilizer flow indicator as long as the liquid characteristics are taken into account. Certain indicators will not tolerate particulate matter or higher viscosity liquids very well. Because of the corrosive nature of liquid fertilizer, flow indicators made of stainless steel are usually recommended, although the chemical composition of liquid fertilizer can vary, and a flow indicator should be specified for the exact composition of the fertilizer.
Because liquid fertilizer can also accumulate build up on the sight glass, our unique model DAA Sight Glass Flow Indicator with an integral cleaning mechanism, which does not require system shut down or device removal for cleaning, delivers an extra value for liquid fertilizer.
How Do You Install a Flow Indicator?
Installing a flow indicator is relatively easy as they are mechanical in nature do not require any menu programming. With little to no exception, all simple flow indicators, that are providing visual indication or flow only with no flow rate measurement, are inline devices that are inserted into the piping of the system.
Each end of the device will have an inlet for the flow and an outlet for the flow that are on opposite sides of the device. The inlets and outlets will have a connection type, here in the US it is usually an NPT thread or an ANSI flange that will connect with the pipe on each side of the device, effectively inserting itself directly into the piping system and the flow path of the media.
Here are some other considerations for installation and commissioning a flow indicator:
How Much Do Flow Indicators Cost?
Flow indicators are generally low in price compared to most other industrial flow instrumentation. The most prominent pricing variables will be the materials used in the construction. For example, high pressure models require higher grade materials to ensure longevity and will cost more as a result.
It is important to verify that the flow indicator that you are considering is an industrial grade flow indicator and not a flow indicator meant for more residential use. Cheap, all-plastic flow indicators are not going to stand up to the rigors of industrial applications.
Flow Indicator Manufacturers
There are many types of flow indicators available that are made by a wide variety of manufacturers. KOBOLD manufactures, sells, and supports our flow indicators and we are well versed in helping you select the best option, whether it be for a single flow indicator or for bulk quantity OEM flow indicators.
Most of our flow indicators are made in the USA, in our manufacturing facilities in Pittsburgh, PA. Our flow indicators are built and tested by hand for quality assurance and deliver the most seamless device integration. Contact our expert engineers now for free assistance in selecting the optimum flow indicator for your needs and your budget.
Learn more about why you should partner with KOBOLD for your application.
Flap, Rotor, or Drip Indication | SS, Cast Iron, or Cast Steel | Up to 580 PSI | 1/4"...2" NPT | 1/2"...8" ANSI
Made in the USA | Twist to Clean | With or Without Rotor | Up to 150 cSt | Up to 230 PSI | Brass or SS | 1/4"...1-1/2" NPT
Rotor, Ball, Flap, Chain, No Indication | Rugged Industrial Build | Up to 580 PSI | Up to 500° F | NPT or ANSI Connections
Made in the USA | Compact Size | Clear Indication | Up to 230 PSI | NPT Connections | 0.05...13.2 GPM
Made in the USA | Liquid or Gas | 85 PSI | NPT Thread | Up to GPM | Up to 88 SCFM
KOBOLD USA is a subsidiary of KOBOLD Messring GmbH, a world-leading instrumentation engineering business founded in Germany in 1980 by Klaus J. Kobold. With patented technology and superior service, the company quickly established itself as one of the global leaders in sensor and control systems with high quality products. The KOBOLD brand name became synonymous with superior quality and technological advancement in instrumentation engineering.
