Iron is by far the most important metal to monitor for trending and limits. Accordingly this section describes unique capabilities for detecting and measuring ferrous particles. Because the technology can be applied at all three analytical Tiers, there is an appropriate instrument or sensor for virtually any system.

Kittiwake have a particular expertise in magntometry for detecting both ferrous (magnetic) and non ferrous (non magnetic) metallic contamination off-site, on-site and on-line. Their instruments are the de-facto laboratory standard for PQ measurement worldwide.

Screening Instrumentation - On-Site and Off-Site:

PQ (Particle Quantifier) – This is an industry standard test method and part of our Analex product range. A scalar reading generated from applying a magnetic field directly to the sample container without preparation. The sample container is placed upon the magnetic sensor - this results in a PQ value, returned in seconds, that can be used as a trigger for more detailed analysis when trended or when limits have been set

DRF (Direct-Reading Ferrography - RPD) – The oil sample is diluted with solvent then pumped into a capillary tube mounted on a housing containing a permanent magnet with a graduated magnetic field, allowing precipitation of ferrous particles at roughly 6µ and 14µ sizes. A typical example is the rotary Particle Depositor from Kittiwake. Ratios of the two values can be evaluated as well as their sum. Like PQ, DRF is best viewed as a trigger for additional analysis, once ‘abnormal’ values are seen

Discussion: Both techniques offer similar value and insight into possible ferrous wear trauma, but the PQ is far more easily and inexpensively wielded in a laboratory setting in Tier 3 venues. The PQ comes in portable versions for Tier 2 venues; the DRF is not easily adapted to remote locations owing to solvent requirements and its relatively larger weight and footprint.

Lube Oil Metallic Debris, Particle Count and Total Debris – On-Line

Test Description: On-line sensors are now available to monitor ferrous and non-ferrous (none magnetic, metallic) debris.

Metallic Wear Debris: allows categorization in to particle size ranges. The count is continuous and cumulative over time, and can readily be trended as to rate of increase. Lower size limit for ferrous debris is circa 40µ and for none ferrous circa 135µ.
Total ferrous: some wear mechanisms produce particles typically smaller than detectable by particle count sensors. Kittiwake have developed PQ technology to measure total ferrous debris on-line irrespective of the particle size (<1µ). This can be likened to measuring the density of water droplets in fog, you can measure the density but not count the individual particles). LinerSCAN is a typical application of this unique technology, reporting in PPM.

Sensors are able to inspect virtually every aspect of routine in-service oil analysis. That most of the inspections are ‘fair’ is notable, but keep in mind that this is still a timely warning well in advance of a sample sent to an off-site lab 30-days hence. The fact that there is a warning allows for investigation or vetting as appropriate. Because they ‘live’ in the lubricant, they are unaffected by oil-water immiscibility, which precludes the impossibility of extracting a perfectly representative sample. It gets worse if an outside lab is employed, as the technician must sample the sample in order to test it. This, too, is an inexact aliquot.

Note that the sensor is able to sidestep the entire sampling issue. With additional On-Site testing, they can take care of almost all the needs to make an informed maintenance decision. Again, the one-two punch with On-Line and On-Site in play can provide up to a 30-day, or even more, vetting advantage over offsite testing. In many instances it will be the difference between failure, and success.

RPD: Rotary Particle Depositor – On-Site and Off-Site

Description: A measured volume of sample is applied, by pipette, to a glass substrate located on a rotating magnet assembly. Particles of debris are deposited radially as three concentric rings by the combined effects of rotational, magnetic and gravitational forces. Microscopic examination of the deposits on the substrate is possible, a viable and less tedious alternative to analytical ferrography. One can also quantify ferrous deposition on the substrate via a PQ ferrous debris monitor.

Discussion: Fatigue wear begins at particle sizes as low as 10-15µ wear particle diameters. It is clear that the smaller the particle that can be identified and quantified, the earlier warning and opportunity to respond one will have as to catastrophic failure potential.

Since the entire idea of online sensors is ‘first position’ alerts as to potential trauma, the notion of minimum size detection is critical, thus a 40µ detection level is on the order of fifteen times the sensitivity of particle detection at, say, 100µ. Such significantly better detection sensitivity can mean all the difference in having the ability to respond early enough, performing a minor repair with correspondingly less downtime, rather than experience a catastrophic failure and a huge loss of production income. The element of safety, as well, should not be discounted.

Applications: There are very few components that cannot benefit from a PC-Ferrous Debris sensor; however, there are certain applications that should be most strongly considered, including: