Geotherm Logo Mobile Nav Icon
Ultra-sound the safe, non-invasive means to detect PD and other facility concerns before a downtime incident occurs
Ultra-sound detection makes the inaudible audible to determine which asset needs repairing or imminent replacement
Ultra-sound identifying a problem at its earliest stage of development
Using our fixed CBM Ultra-sound systems to provide constant information on the growth rate and severity of a PD issues anywhere in the world

Ultra-sound (HVPD)

All operating equipment produce a broad range of sound. The high frequency ultrasonic components of sound are extremely short wave in nature and above the range of human hearing. A shortwave signal tends to be fairly directional, enabling location of the anomaly; within high background noise.

Partial discharge (PD) is a condition that occurs in high voltage electrical switchgear. When insulation deteriorates, it create a characteristic high-frequency noise. Using the EA Techology Ultra-TEV Plus+ and/or the UE Systems Ultraprobe 15000, we can passively listen for electrical PD anomalies. The use of these probes provide a fast, reliable and non invasive inspection method of collating audio and spectrograph data to determine the form of PD, be it Corona, Tracking and/or Arcing.

PD are small electrical sparks that occur within the insulation or on its surface which are caused from a defect or void in the insulation and can occur on both new and old, medium or high voltage electrical systems.

If PD is allowed to continue, it will erode the insulation and eventually result in a complete breakdown and failure, causing an electrical outage. These failures cause unplanned power outages, loss of production, equipment damage and personnel injury.

Data obtained through our handheld PD testing probe, or our fixed continuous conditioning monitoring system using the EA systems Ultra TEV Monitor system can be remotely monitored anywhere in the world; providing critical information about insulation quality and its impact on electrical system health.

By detecting and trending PD over time, it is possible to observe its development and assist decision making processes to repair or replace the electrical asset before any unexpected outage occurs.

The three main types of electrical PD can be categorised as:


TThis occurs when air molecules around conductors become electrically charged (ionized) in equipment operating over 4kV, producing an invisible (to the human eye) corona arc bursts This is usually coupled with a continuous inaudible (to the human ear) high frequency sound, which resembles a buzzing, frying noise which warn of an existing problem. Corona sound file.


This is the early stage of arcing and a result of carbonation on the surface of insulation which leaves a dendritic branch like pattern of carbon on the insulator surface. The carbonisation degrades the resistance pathway to earth and a point for flashover. Tracking is revealed as subtle infrequent popping sound: Tracking sound file. These are inaudible sounds, when they become audible it is time to implement corrective actions.


This is the flow of electricity through the air from a conductor, to another conducting object. It can include visible signs such as sparks and flashes and indicates the presence of worn or damaged insulation. The high frequency erratic stop and starts resembles the noise of a badly used arc welding set. PD Arching sound file.

Ultra-sound & Leak Detection

Ultrasound leak detection can provide a safe means to find a wide range of high or low pressure leaks, (within vacuum leaks too). Buried or above ground fluid leaks (be it gaseous or liquids) are quickly detected using an ultrasound probe since the by-product of any leak is turbulent flow and cavitation, which generates ultrasound. Turbulent flow occurs when gas moves from a high-pressure side to the low-pressure side of a leak. Locating leaks up to 15 metres away are identifiable, minimising the need to work at height, the system is relatively straight forward since ultrasound is:

  1. Directional – locating the discharge source quickly.
  2. The signal intensity gets louder the closer one gets to the leak.
  3. The fixed frequency – makes Ultrasound more effective to locate leaks in noisy areas.

Hydrocarbon and compressed air leaks become expensive commodities. A leak reduction plan will reduce energy and product waste and likely to save you thousands of pounds through the lifetime of your facility.

Implementing a regular leak reduction program will have immediate energy savings, on average 4% could be saved on the energy bills through compressed air leaks alone. A regular leak survey will allow leak detection, tagging and prioritize repair planning.It’ll also provide environmental benefits and a fast financial return.

Ultra-sound - Steam Traps

When steam traps leak or fail, it can be extremely costly in terms of product quality, safety and energy loss. Nearly all steam trap manufacturers consider Ultrasound inspections as the most reliable method in determining their operational state and condition.

Ultra-sound - Bearing Monitoring

Predictive & pro-active inspections of rotating and reciprocating equipment using a Ultrasonic detection probe has many advantages, such as detecting the earliest stage of bearing failure and bearing lubrication issues. Ultrasound can be used on all bearing speeds.

Since Ultrasound is a high frequency short wave signal, it is possible to filter out background noise and focus on the specific bearing to be inspected, even at a distance. As the roller bearing rotates, the friction impacts between component parts to generate Ultrasound.

Operating bearings produce a steady level of Ultrasound. If the bearings are under lubricated the Ultrasound becomes harsher. Conversely over lubricated bearings give rise to overheating and a rapid degradation of the lubricant. Bearings which are beginning to fail willtypically have small particles of metal in the lubricant or have surface irregularities. Good bearings make a consistent low level whirring sound without variation.

Mechanical movements produce a wide spectrum of sound. One of the major contributors to excessive stress is friction. By focusing on a narrow band of high frequencies any subtle changes in amplitude and sound quality can be further investigated.

There are three inspection methods for ultrasonic bearing monitoring:


Compare same type bearings and note deviations.


Establish a trend over time of measured values.


Utilize analysis software to store, trend and report findings.

Bearing failure noise levels are typically grouped as follows:

  • An 8 dB gain over baseline indicates pre-failure or lack of lubrication.
  • A 12 dB increase establishes the very beginning of the failure mode.
  • A 16 dB gain indicates advanced failure condition.
  • A 35-50 dB gain warns of catastrophic failure.

Converting high frequency sounds to the audible range and displaying and recording the signal spectra using our Ultra-probe allows troubleshooting diagnosis and comparative analysis; to confirm whether the bearings require attention or replacement. Data can then be presented into a exception based report to record all survey findings for immediate or timely based maintenance corrective sanctioning.