Ultrasonic detectors find leaks and faults

Compressed air is widely used and an effective propellant for many types of machines used in various locations within many industries. Indeed, almost 90% of industries use compressed air in some aspect of their daily use/production. One similarity discovered is that throughout all industry wasted energy in compressed air is quite common.

However compressed air (and other gases) are at the same time a very large cost to the company's budget each year.

It is therefore sensible to continuously inspect the company's air, vacuum or gas installations on a frequent basis.

Portable fault locating detectors are ideally suited, especially in noisy environments, to be used in energy conservation, predictive maintenance and proactive maintenance programmes for leak detection and mechanical inspection.

Logis-Tech Associates has recently introduced to the UK a range of ultrasonic devices for listening to leaks in compressed air and vacuum installations, leaks in tanks etc, and to listen to mechanical noise from for example in ball bearings or other movable parts.

A leakage test may prevent more serious and costly problems from occurring or even show that the installation of a newer larger compressor is unnecessary.

The Logis-Tech EP equipment consists of a very sensitive listening detector where a headphone or an authorised hearing protector with loudspeaker can be connected.

The system works by "listening" at a frequency band that normally is inaudible to humans - from 20kHz and upwards (ultrasound).

Audible noises from the surroundings are filtered off so that the device can be ideally used in a noisy environment.

The Logis-Tech EP equipment can also be used with an ultrasonic transmitter that transmits pulsating ultrasound.

The transmitter is placed inside the item to be examined, which is then closed.

The user can then examine the item from the outside and can easily detect, any leaks.

Air leakage can be defined as consumed air that contributes nothing to production.

In a well-managed system, wasteful air leaks should not exceed 5-10% of net production consumption.

This acceptable leakage still costs the company per year.

Although most engineering and maintenance personnel are aware their operations have air leaks; the biggest problem is they are unable to quantify those air leaks in order to make rational corrective decisions.

This is where a quality compressed air leak-detecting device comes into play.

Since air leaks are a reoccurring problem, it is imperative that plant personnel initiate a regular preventive maintenance programme allowing the detection of these wasteful air leaks.

Ultrasonic sensors detect the disturbance caused by turbulent flow, which is produced by a leak, and because they are sound sensitive, they can be applied to all types of fluid systems.

Detecting air or gas leaks in pressurised tanks, vacuums, boilers, tubing, pipe fittings, flanges, seals and gaskets are all possible.

Specific typical industrial systems include: condensers, furnaces, heat exchangers etc.

The advantage of using these sensors is that they are able to sense a leak in real-time.

During a scan, a user will hear the sound of the leak increase as the sensor passes by the place where it is located.

In the contact, or waveguide mode, leaks in steam traps and valves are also sensed.

Using permanently mounted sensors, valves can be monitored for both the onset of flow, such as in safety relief valves or for flow disruption.

A machine or another propellant loses its effectiveness if or when mechanical malfunctions occur.

Often these mean reduced production or at the worst an unintended and expensive production stop.

It is therefore important to be able to quickly locate the mechanical malfunction or in some cases to make a systematic monitoring of essential machine parts to always be able to make a controlled production stop with all the economical advantages this entails.

Also, in this case, the Logis-Tech EP equipment consists of a detector with a headphone or hearing protector where an electronic internal/external sensor (stethoscope sensor or clip) can be connected.

The sensor is used for listening to mechanical noise and only picks up mechanical low frequency vibrations so the stethoscope can also be used in noisy areas.

Within all mechanical operations bearings, pumps, motors, gears, gearboxes and compressors, produce some form of "typical" sound patterns, and a change in these patterns can be detected and analysed.

NASA in the USA paved the way for ultrasonic bearing inspection by demonstrating that ultrasonic monitoring provided the earliest warning of bearing failure.

In addition, conditions such as rubbing and lack of lubrication can also be detected.

The advantage of ultrasonic inspection is the short-wave nature of the signal allows inspectors to easily inspect specific components in operating equipment.