• Alarms before impeding failure occurs.
• Alarms way before any vibration detector. How so? Simple, as a bearing is failing large pieces of itself are released increasing clearances. When enough clearance is generated the vibration is detected. At the beginning of this event, even before there was any change in clearance, the Grid Switch has warned you.
• Quick disassembly and visual inspection of trapped debris allows you to determine if you have a problem before costly damage occurs.

How's it work? (The simple explanation)

Oil enters in the top port of the grid switch and flows through a multitude of small holes in the fiber composite material to which the metal grid is bonded and exits out the bottom port. If a bearing shell for instance begins to flake a single metal fragment if it breached the grid would alert you of trouble. Since the metallic piece that caused the alert is still on the grid a visual inspection can often identify the offending particle's source and the offending part can be replaced BEFORE major damage is caused, at a planned time when all personel are available, minimizing downtime and expense and not when vibration detectors finally flag the component after clearances have increased to the point where particulate matter has overwhelmed the filtration system resulting in metal throughout the entire lube system with resultant damage to ALL bearings and journals. This failure of course happens at the most inconvenient time, (usually in the wee hours at the beginning of a long weekend) maximizing repair expense, downtime and lost production.

How's it work? (The more involved explanation, for you engineer types)

The Grid Switch Metal Particle detector is an on-line device detecting unusual metal spalling and helps an operator anticipate catastrophic failure of a key lubricated component. By use of an electrical grid, large, failure-linked metal debris is intercepted, bridging the contacts and providing an alert signal.

It has been widely-applied in the drilling market for over 25 years, helping maintenance people intercept hardware failure before it does the expensive crash & burn.

It can be applied on any critical lubed system, including hydraulic pumps (on the case drain) or on heavy duty pressure lubricated gear sets.

It is useful to reflect on ways to convey the operation of the Grid Switch as opposed to off-line debris detection methods like spectrographic oil analysis. The 3-D graphic below is an adaptation of work done by others in their studies of tribology during failure and has been confirmed in a number of different operating systems.

What this graph describes is that a normal wear condition on lubricated components produce relatively small particles. As the component approaches catastrophic failure, the debris sizes and the range of sizes increases.

In selecting a device for tracking the health of a component, it would be logical to match its particle size sensitivity to those sizes being produced by the lubricated item. Indeed, from comparison of the two graphs above, the Grid Switch detection "sweet spot" is at optimum.

Traditional spectroscopy does not detect larger particles:

Research has been done into the accuracy of traditional spectrographic oil analysis at detecting the onset of a failure condition. The U.S. Air Force undertook a large survey to uncover why they were red-lining jet turbines that later proved to have no failure condition, yet often missed others that proceeded to during flight.

It took some detective work, but they found that the various spectro methods had very poor accuracy on wear metals present when the particles were larger than 1 to 2 µm.
Because the debris size distribution at various states of turbine "health" conformed to the graph above, spectro's tended to miss the production of the larger particle sizes that would indicate the onset of failure.

With some good lab input, the Air Force changed their analysis approach to incorporate an acid dissolution of each sample so the metals present were forced into solution where they could be detected. Their accuracy at detecting the onset of failure improved dramatically.