Ultrasonic Device Versatile

Concerned with equipment failures and increasing downtime, management of Alcoa's Newburgh plant decided to upgrade their preventive maintenance efforts. The Mechanical Maintenance Dept. was particularly concerned with inspections of mechanical equipment and machine components.

What the craftsmen needed was instrumentation that could detect all types of malfunctions and leaks. Preferably, it would enable one craftsman with one instrument to test many types of operating equipment.

Solution
Alcoa purchased an ultrasonic detection system. A Technical Specialist from the plant had seen a demonstration of this instrument at an engineering equipment show and was impressed with its capabilities.

The instrument gives data to its user in three ways: through auditory means via a headset, through a bi-modal analog meter and through the ability to switch to auxiliary interfacing for chart records.

Two features of this tester are notable:

• Frequency tuning enables a user to tune into problem sounds while minimizing background interference.

• Meter mode selection adjusts the meter response from a real time response to an averaging

response. This feature allows accurate adjustments for leak detection and for mechanical analysis.

Sensitive only to ultrasonic frequencies, the instrument will not respond to the low frequency noises often associated with most plant equipment. Thus it can be effectively used in extremely loud environments.

Components of this system include an instrument with a pistol grip, ballistic meter, frequency tuning dial, potentiometer, sensitivity dial with selection lock, bi-modal meter selector switch, battery, battery indicator light, battery recharger receptacle and head set receptacle.

Additionally, there is a contact type stethoscope probe for monitoring internally generated ultrasound such as from bearings, steam traps and heat exchangers. The stethoscope probe includes an extension that increases the contact range to 31 ins.

Valve seating can be easily checked with this instrument. A properly seated valve produces no noise at all, while the flow of gas or liquid through an open valve makes a rushing sound in the ultrasonic frequencies. A break in the seat of a closed valve causes a turbulence that generates a distinctive ultrasonic signal. The user of the instrument need only touch the contact probe to the valve body to determine its condition.

Alcoa has been using the instrument to check for malfunctions of steam traps and valves and to locate pressure leaks. They also use it to check the condition of slow moving bearings, to determine if hydraulic jacks are leaking, and to test the cutter heads on scalping machines.

Results
Alcoa has found this ultrasonic inspection system so effective that three instruments have been kept in use for the past two years and a fourth one was recently purchased. The Maintenance Department feels that the system is one of the company's primary tools for preventive maintenance work.

An ultrasonic detection instrument is a powerful tool
for preventive maintenance because it has many advantages in the early detection of problems. It is light in weight, versatile, easy to use and relatively inexpensive. At left the system is in use on a bearing.