Reader Question – “PM” of Ultrasonic Equipment

The preceding blog addressed the most common service issue with ultrasonic equipment, the ultrasonic generators, along with Preventive Maintanance measures that can help minimize generator failure events.  Today’s blog will cover additional Preventive Maintenance measures which apply not only to ultrasonic cleaning equipment but to the broader range of cleaning equipment of all types as well.

“Routine”  Preventive  Maintenance 

First and foremost, read and follow the guidelines provided in the maintenance or instruction manual that is provided with the machine.  This document will recommend necessary routine maintenance procedures including filter changes, lubrication type and frequency, required calibration and other activities that are relevant to the particular machine.  It should also provide a detailed list of recommended preventive maintenance procedures.  Following the recommended manufacturer’s guidelines is an absolutely necessary part of any preventive maintenance routine.  If the manual can’t be found, contact the manufacturer to get one.  If yours is a “custom” machine, make sure you get a copy of the manual specifically written for your machine and not just a generic document.  A copy of the instruction manual is probably available as an easily read and printed PDF file.  If not, a hard copy might cost $100 but is well worth the expense.

Pet Peeve – One of my “pet peeves” is the supervisor or manufacturing engineer who confiscates the instruction manual to the “safety” of his or her filing cabinet immediately on receipt of the machine never to be seen again.  That document is only of value if it is available to those who actually operate the machine.  Verbal transmission of operating procedures, for example, is seldom accurate after one or two generations.

Keep It Clean

Since so much of a preventive maintenance program relies on visual inspection, it is important that cleaning equipment be kept as clean and accessable as possible not only above the deck but below as well.  When buying and placing new equipment, make sure there is access to all parts of the machine and that the access doors (or whatever) are not positioned so that they are blocked by obstructions (walls, posts, etc.).  Frequent cleaning by vacuuming or the use of compressed air helps to minimize any accumulation of dirt and dust that might interfere with a thorough visual inspection.


It is important that all preventive maintenance procedures be documented.  A permanent record of what should be done as well as what has been done and when it was done is the only way that continuity of the preventive maintenance efforts can be assured.  A good way to provide this documentation  is to maintain a log at the machine location.  All operators and maintenance personnel should have access to the log to record preventive and other maintenance activity.  Good documentation is a valuable resource when it becomes necessary to troubleshoot the cause of a major machine malfunction.

Special Emphasis on Electrical 

In general, electricity and water do not mix well.  Cleaning equipment utilizes electricity for controls, sensors, various kinds of drives, automated valves, heaters and a host of other necessary functions.  In ultrasonic systems, the cables connecting the ultrasonic generator(s) to the transducer(s) are an additional concern as these cables may operate at voltages of 1,000 volts and above.  Because of the amount of wiring in even a small cleaning system, keeping water and electricity from mixing requires ongoing vigilance.  System engineers make every effort to isolate electrical systems in the design phase of the equipment but, over a period of time, even their best efforts may be compromised as the equipment ages and necessary modifications and upgrades are implemented.  Plumbing and tank leaks are obvious sources of liquid contamination and should top the inspection list.  There are also however, some sources of liquid contamination that may not be anticipated during the equipment design process.  In the normally humid environment of the cleaning area, condensation, overspray and such things as parts dripping during transfer can be a potential for unexpected electrical failure due to moisture.  In order to prevent electrical failures, preventive maintenance should include frequent and thorough inspection of all electrical wiring and connections to make sure they are both dry and corrosion free.  Inspection should not be limited to high current carrying conductors such as those supplying pumps, ultrasonic transducers and heaters but should also include sensors such as thermocouples, proximity sensors, level sensors and micro switches.  Failure of wiring connected to a thermocouple, for example, could result in a false temperature reading that could cause a heater to overheat resulting in damage to both the heater and, potentially, to the tank to which the heater is attached.  Malfunctioning level sensors intended to prevent a pump from running dry could cause irrepairable damage to a pump, etc.

Sensors That Don’t Sense Correctly 

Failures of interconnecting wiring is not the only potential source of sensor-related failure.  Heat sensing thermocouples, level sensors, proximity sensors and other detectors are all subject to giving false readings due to improper calibration or changing in position over time.  The best temperature controller can not compensate for a false reading provided  if the thermocouple sensor has become detached from the tank it is intended to control.  The ONLY way to prevent this type of failure is to visually verify that the sensor hasn’t vibrated loose from its mouting to the tank.  It’s always a good idea to verify temperatures using a thermometer to make sure that the indicated temperature is the same as that in the tank itself.  The same thing goes for proximity sensors, level sensors and other sensing devices.  Sensors usually operate at low voltage and current which makes their wiring especially vulnerable to moisture and corrosion.

I could continue with a list of preventive maintenance recommendations but, since all machines and equipment are different, that list could not possibly address early detection of all potential failures.  The best preventive maintenance scheme is, in my opinion, to have at least one person on the maintenance staff who is intimately familiar with every machine.  This person should be able to anticipate potential failure modes and be able to monitor the pulse and other “vital signs” (figuratively) of the machine on at least a daily or weekly basis.  Signs of problems including blowing circuit breakers or fuses should be traced to the source and not just “reset” repeatedly to keep the equipment running.  I think I remember an old adage (probably from my grandmother) that a “stitch in time saves nine.”  “Stopgap” measures are likely to only postpone and perhaps complicate proper repair at a later date.

In conclusion, I am sure that readers will be able to add suggestions to the above from their own personal experience.  Fire those suggestions to me at and I’ll publish a blog to clean up loose ends using your suggestions in the next week or so.  Thanks in advance for your help.

–  FJF  –

2 comments on “Reader Question – “PM” of Ultrasonic Equipment

  • Stephen – This is a good question and one that I will address on the blog in the near future. Yours is a problem faced by many so I’ll get the information out there soon.

  • Stephen Sharkey says:

    Hi John,

    We have experience failures of transducers coming away from the bottom of the cleaning tank. The transducer can still be operating, with less sonic power in the cleaning tank. How would you monitor this?

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