Ultrasonic Sensors Enhance Preventive Maintenance and Energy Conservation Programs

-By Paul Tashian

It has been nearly five years since Ultrasonic leak detectors began their rise in popularity in the HVAC/R trade.  To many, however, it is still considered the “new” method of refrigerant leak detection.  Ultrasonics has proved to be a valuable tool for finding leaks in windy or gas saturated areas.  They work by detecting the ultrasonic hissing sound of turbulent gas as it escapes from a leak orifice.  The sound is then heard through a headset and viewed on a display.  Because this method works by sound, it can detect ANY gas, including vacuum leaks.

Five years however, seems like a short period of time considering the advancements which  have been made.  Earlier ultrasonic instruments would make a beeping, clicking, or squealing sound to indicate a leak.  Anyone who used these instruments knew how frustrating that beep could be when background noise was present.  Technological advancements like those made by Superior Signal Co., Inc. in New Jersey, offer a vast improvement in sound quality.  Ultrasonic users can now discriminate the rushing sound of a gas leak from other mechanical background sounds.

Ultrasonic detectors have been used for years by large industrial plants for a variety of leak detection, maintenance and preventive maintenance applications.  Until recently however, the price for such equipment was generally a few thousand dollars!  Not bad if your a refinery,  pharmaceutical manufacturer or auto maker, but a bit hard to swallow for most who service HVAC/R systems.  New developments, however, have brought the price of such instruments well within the reach of most contractors.

Ultrasonics is now available not only as a reactive type instrument (used to find or solve a known problem such as a leak), but as a proactive preventive maintenance tool  (one to be used on every regular service call).

The old idea… “If it ain’t broke, don’t fix it!” is quickly disappearing in today’s profit conscious environment.  In a large industrial facility such as an auto assembly plant, refinery or food processing plant, downtime of the equipment and systems being used can cost a company tens or even hundreds of thousands of dollars a day should they fail.  It is not unlikely for a plant to own tens of thousands of dollars in sophisticated test equipment designed to establish trends, and predict failure points in vital equipment.  These programs usually involve vibration testing, infrared imaging, and ultrasonic testing.  Why do they do this?  Because they know that an investment made today can easily be justified if only one fault can be repaired before an unexpected failure occurs.

On a smaller scale, most everyone practices the same sort of preventive maintenance on their own personal property.   Your automobile for example.   You probably change the oil regularly.  Why?  To prevent severe damage to your expensive engine.   You most likely check you tires periodically as well.  You check air pressure, and examine the treads for wear.  With experience you notice a trend, that every 40 to 50 thousand miles its time to replace them, and start putting the money aside for a set of new tires.  Why do you keep such a close eye on your tires?  To avoid the unpleasant and dangerous experience of an unexpected blowout!

Shouldn’t the same practice hold true for expensive air conditioning, heating, and refrigeration systems?  If a chiller goes down in a food storage facility the results could be devastating.  This idea is understood by the many contractors who are already involved in preventive maintenance and successfully promote the practice by selling service agreements.

Incorporating ultrasonics into your business
Ultrasonic testing can add significant value to the services you offer.   It is a simple, and  effective way to create a report card or trend a systems health.  Ultrasonic instruments let you hear sounds that could never otherwise be heard by the human ear.  New advancements in the technology such as contact probe sensors are excellent for hearing internal system sounds like worn bearings, and leaking valves and steam traps.  Digital units are now available which let you assign a numerical value to the intensity of the sound from a particular test point such as a bearing.

Compressors, pumps, and motors contain bearings which are constantly wearing down, and without proper maintenance will eventually fail.  The ultrasonic instrument’s contact probe is incredibly sensitive to the internal friction within a bearing housing.  A digital display indicates the intensity of the sound on a scale from 0 to 255, and can be set to “Peak Hold” to lock in on the reading even with major sound fluctuations.  After a few tests, a baseline can be established to use as a comparison for future tests.  As internal bearing components wear, you will see a corresponding trend of increased ultrasonic sound levels.  When readings are inconsistently high for a particular test point, chances are there is a problem deserving attention.  Ultrasonic instruments can help you gauge the extent of this wear and warn customers before it’s too late.  A chart can be used to show the customer  hard data.  And if you are computer oriented, you can use a spreadsheet such as Microsoft Excel to record the readings, and create graphs and charts to clearly illustrate these problems.  The ability to provide this information can be incredibly valuable to your customers.  Ultrasonic instruments can also be used to prevent over or under lubrication while greasing bearings.  Induce lubricant until you hear the bearing running smoothly, and relatively quiet, then stop.

Energy conservation is another cost saver for ultrasonic users.  As we compared your automobile and preventive maintenance, think about your home and energy conservation.  You wouldn’t leave your windows open in the winter, and still expect to effectively heat your house.  Actually if your windows were old and drafty you might even spend thousands of dollars to replace them with a new energy efficient replacement window. 

There are two popular energy saving uses for ultrasonic detectors.  The first is for testing steam traps.  Steam is used in many homes and buildings, especially older ones.  Simply stated, the steam trap is designed like an automatic faucet to purge cooler condensate (water) from the system while retaining the hot steam.  When steam traps leak, or fail in the open position, the steam which is costly to produce will escape.  In a sense this is like leaving your windows open in the winter.  An ultrasonic detector offering a solid contact probe can detect this internal leakage.  Replacing failed steam traps has proven to save hundreds, thousands, and even tens of thousands of dollars in large facilities.  A steam trap survey using ultrasonics is easy to do, and adds value to the services you offer.

Testing the tightness of an enclosure such as a walk/reach in refrigerator or freezer is another energy saving application for ultrasonics.   With an accessory called an ultrasonic sound generator, a contractor can quickly locate gaps in door gaskets, cracks in the case, or any point where cold air can escape.   The ultrasonic tone generator placed inside the case emits a high frequency tone which is over 100 decibels loud.  Because the tone is ultrasonic your unaided ear cannot hear it, however it will travel through any holes or cracks, and be detected using an ultrasonic detector.  Sound generators with a constant tone rather than a “warble” sound are beneficial if you want to compare the sound intensity of one leak to another.  This technique can also be used to check the weather tightness of a building.  Use the sound generator to test windows, doors, and skylights.  You might find areas that need to be caulked or sealed.  Again, this is an additional service you can provide with your service agreements, and possibly charge a premium for.

With so many diverse applications, the potential of ultrasonic technology is tremendous.  Incorporating ultrasonics into your business can provide your company with a significant competitive advantage, and selling tool which generally requires only a minimum investment in time and equipment.