See the Plant Engineering edition where this Fluke article first appeared in print.
Savvy maintenance professionals know that infrared (IR), non-contact thermometers fit beautifully into motors, drive and electrical maintenance. Simply scan the equipment while it's operational and look for components that are running hotter than they should be. Find problems before they burn up, and you save money and time.
But are you saving as much as you could? Keep reading to see what other common maintenance and troubleshooting applications these thermometers are good for.
And just in case you've written off infrared as inaccurate: Not any more.
Top three methods for infrared testing
Here's the basic application.
- Measure the absolute temperature at a spot. This type of measurement is useful for trending the temperature of an object or comparing a measurement to a specification.
- Compare the temperature differential of two spots. You might, for example, compare the same component on two different motors.
- Scan an object and detect changes within a continuous area on it. This allows you to find hot or cold spots on housings, panels and structures. For example, you can check the heat sink of air-cooled transformers for cool tubes that indicate a restricted flow or a lack of flow.
Seven not-so-common applications for IR thermometers
Using one of those basic methods above, turn your thermometer onto some of these applications.
Troubleshooting special electrical components:
- UPSs (uninterruptible power supplies) use direct-current (dc) batteries with terminal connections that are susceptible to loosening and corrosion resulting in excessive heat. Look, too, for hot localized connections in UPS output filters. Since large 3-phase UPS systems have capacitors wired in series and arranged in banks, the simplest way of testing a filter's integrity is to check its relative phase-current balance.
- Low-voltage back-up batteries also should be checked for sound connections. Poorly attached cell-strap connections in a battery string can overheat enough to burn the posts.
- Light ballasts and other lighting fixtures overheat due to aging electrical components. A non-contact IR thermometer can detect an overheated ballast, for example, before it starts to smoke.
In one survey of electrical service and maintenance personnel, 100 percent of those using IR thermometers said that they prevented thousands of dollars of downtime and repair expenses as a result of finding hotspots in electrical systems.
Checking other important systems:
Use an IR thermometer to monitor everything from ovens and boilers to freezers and steam systems.
- Steam systems are especially important. Regularly compare the inlet and outlet temperature on steam traps. A properly operating steam trap produces a significant temperature drop. If the temperature doesn't drop, the trap has failed open and is passing superheated steam into the condensate line. If the temperature drop is very large, the trap may be stuck closed and is not ejecting heated condensate. Condensate in steam lines waste energy, since the condensate reduces the effective energy of the steam, and can cause operational problems in steam-driven processes where the unwanted liquid can hamper operations or even corrupt the finished product. A faulty steam trap can cost a plant $500 (US) or more per year. In a typical year, 10 percent of industrial steam traps fail. So, if a plant has 1,000 traps, an IR thermometer can save that plant $500,000 or more each year.
- Building comfort (HVAC) systems are candidates for significant energy savings. Monitor all HVAC components as well as the building's envelope. A non-contact IR thermometer provides data for quick energy audits and room balancing. A 50:1 distance-to-spot ratio (or better) makes elevated vents and returns very accessible. Know, too, the operating parameters of HVAC equipment. If a chiller should produce 44°F water, an IR thermometer can instantly reveal whether the chiller is operating within spec.
- Process monitoring makes a handheld IR thermometer a quality-control tool. You can use it to monitor processes to ensure that temperature-related process parameters are within specifications. In many instances, especially when only periodic temperature monitoring is required, a handheld IR thermometer is the natural choice for condition monitoring. Given the number of process industries (refineries, paper mills, pharmaceutical companies, bakeries, canneries, etc.), the possibilities for using a handheld IR thermometer are almost limitless. Likewise, the kinds of equipment that might be monitored are nearly limitless, too. In processes, fluids need to be delivered to the right place at the right time and in the right amounts. A handheld IR thermometer can pinpoint obstructed piping, malfunctioning automatic valves, cooler and heater malfunctions and a host of other potential problems.
- Monitoring of products themselves also allows a handheld IR thermometer to become a quality-assurance tool. Documented uses of handheld IR thermometers on products on production lines include rubber tires, aluminum auto wheels, urethane-molds and chocolate bars, among a host of others.
Getting the most for your thermometer money
Most IR thermometers operate pretty much the same way, so it's not necessarily obvious how one model could be vastly more accurate than another. Here's what to look for.
High optical resolution.
The optical systems of all IR thermometers collect infrared energy from a circular area or "spot" created by an infrared beam. The farther from the target one gets, the larger the spot is. The resolution of an instrument is defined by the ratio of the distance from the instrument to the target compared to the size of the spot ("distance-to-spot" or "D:S" ratio) at its focus point.
Some low-end instruments have a relatively low D:S ratio of 6:1 or 8:1. So, to measure a one-inch spot, the user must be six or eight inches from the target. More sophisticated yet affordable IR thermometers have distance-to-spot ratios of 30:1, 50:1 or higher. An instrument with a 50:1 D:S ratio can measure the same one-inch spot from a distance of approximately four feet. From four feet away, the entry-level instrument described earlier would be measuring a spot eight inches or more in diameter.
In order to get a good reading the target must be larger than the spot size and ideally should be twice as large. For example, from the floor, you probably could not record the temperature of an overhead conveyor motor using an instrument with an 8:1 D:S ratio. However, it is likely that you could get the job done with an instrument with a 30:1 or 50:1 D:S ratio. High resolution is also important when working closer up because it allows precise measurement of smaller targets from a safe distance.
IR thermometers calculate the surface temperature of an object using the amount of energy emitted by the object and the efficiency with which the surface of the object emits that energy. The latter is its emissivity. Since the emissivity of most organic materials and painted or oxidized surfaces is 0.95, many IR thermometers use this factor in all temperature measurements. However, certain materials, such as concrete and shiny metals, are poorer emitters. So, using an emissivity setting of 0.95 in taking their surface temperatures of will not yield an accurate result. In order to use your IR thermometer in the widest variety of applications you'll want an instrument with easily adjustable emissivity settings.