| Sensor Bore (mm) | Particle Diameter (µm) | Flow range (litres/min) |
| 6 | 30 | 0.7 - 35 |
| 11 | 50 | 2 - 100 |
| 25 | 100 | 6 - 300 |
Units are suited to debris detection in a wide range of lubricants, hydraulic fluids, and even water based emulsions. Reliable operation has been established (synthetic lubricant) to in excess of 175 C, oil and unit temperatures. PATROL employs a pair of sensing coils arranged around and mechanically isolated from an inner (typically PEEK) sensor bore. The coils are connected in a bridge configuration for good common mode rejection and environmental compensation. The bridge is driven by a differential transformer coupled low noise oscillator to provide excellent signal to noise performance. Dual phase detection is used so a transient change in coil impedance due to the passage of a 'magnetic or conductive material provides two output channels, with minimal interaction between the two. Contrast this aspect with devices which provide a single sensor output with only a polarity reversal indication of ferrous/non-ferrous material. These may completely fail to indicate passage of particles consisting of materials with intermediate permeability and high conductivity. Close attention in the magnetic modelling of the sensor geometry has ensured an insignificant variation of output for a particle regardless of its flow path. Output is independent of flow rate through the sensor across a wide range, as well as viscosity and temperature variations. This flow characteristic independence cannot realistically be claimed for magnetic plug based monitoring devices however sophisticated.
PATROL provides a unique set of benefits to the user. These do not emerge solely from the sensor alone or its electronics aspects. Whilst the impedance of the sensing coils is interrogated electronically, impedances changes are caused by electromagnetic effects. The efficacy of the particle detector results from the careful consideration of the fundamental (electro)physical phenomena within in the sensor coils. The coils combine seamlessly with the most appropriate circuitry: PATROL is not just another R & D inductive debris sensor. There have been many debris monitoring solutions proposed and brought to market over the years. Some have fallen by the wayside due to immature or overly expensive technology. Others have provided limited performance despite grand claims. Meanwhile PATROL has been steadily developed with the aid of invaluable feedback from independent, practical and realistic evaluation.
There is considerable interest at present in future technologies aimed at giving a comprehensive on-line analysis of wear debris in lubricant systems. Features including particle morphology and material composition are being targeted by use of high resolution optical scanning techniques and magnetic resonance imaging. Arguably, these remain many years from emerging as a demonstrable possibility let alone and affordable practical solution. On the other hand claims made for instrumented magnetic plugs (chip detectors) have proven unsustainable in practice. Lack of sensitivity, drift, capture efficiency variations continue to plague these purely inductive techniques, and clearly they will never 'see' on-magnetic debris. PATROL today offers a rapidly maturing capability to see wear debris as it is produced. There are no sampling errors or capture efficiency uncertainties. Integral shielding and electronics promote excellent sensitivity and vector outputs give enhanced material type.
Of critical importance to debris monitoring success are the costs associated with its implementation. The relatively simple construction of PATROL and its low component count provide both good reliability and a highly cost-effective solution. Furthermore the clean, stable and unambiguous electronic outputs render signal processing more straightforward and reliable with concomitant overall cost benefit. Similarly unsurpassed sensitivity will determine onset of any problems at the earliest possible stage reducing maintenance expenses.
We can supply one-off or larger quantities. We are interested in furthering discussions re PATROL with a view to technology transfer, licensing or other commercial arrangement.
In particular MTML welcome opportunities to work alongside specialist Condition Monitoring and other
interested organisations to develop powerful and practical debris monitoring solutions.