The Shock Pulse Method: Catching Bearing Faults Early

The shock pulse method (SPM) is a condition monitoring technique built specifically for rolling-element bearings. Instead of measuring how much a machine shakes, it listens for the tiny high-frequency shock waves that a damaged or poorly lubricated bearing produces, which lets it catch a developing bearing fault long before broadband vibration rises.

What it measures

Every time a rolling element strikes a flaw or runs through a thin oil film, it sends a sharp pressure pulse through the metal. The shock pulse method uses a transducer tuned to its own resonant frequency, around 32 kHz, so it responds strongly to these short, high-frequency impacts and ignores ordinary low-frequency machine vibration. The result is a measurement dominated by bearing condition, not by the rest of the machine.

The two numbers it produces

• The carpet value is the background level of weaker, frequent pulses. It rises when the lubricating film breaks down, so it is an early warning of a lubrication problem.
• The maximum value is the level of the strongest pulses. It rises when surfaces are actually damaged, so it indicates mechanical deterioration.

The gap between the two tells you whether you are looking at a lubrication issue or real damage.

Why readings are normalised

A big, slow bearing naturally produces different pulse levels than a small, fast one, so raw numbers cannot be compared. The method normalises each reading using the bearing bore diameter and shaft speed, producing a value that maps onto simple green, yellow and red condition zones regardless of the bearing.

Where it fits

Shock pulse monitoring is a specialist complement to broadband vibration. A machine can still sit comfortably inside its ISO 10816-3 vibration severity limits while a bearing is already generating shock pulses, which is why the method catches problems earlier for the specific bearing failure modes it targets. For a broader comparison of detection techniques, see thermography vs vibration analysis.

From an early warning to a work order

An early bearing warning only helps if it turns into planned work. A monitoring platform that trends the carpet and maximum values and raises a job when they cross a limit converts a subtle rise into a scheduled bearing change rather than an unplanned stop. Fabrico closes that loop from the reading to the routed repair. Book a Fabrico demo to see it on your machines.

Frequently Asked Questions

What does the shock pulse method detect?

It detects the condition of rolling-element bearings, specifically lubrication breakdown and surface damage, by measuring the high-frequency shock waves those conditions produce.

How is it different from vibration analysis?

Vibration analysis measures overall machine movement across a broad frequency range. The shock pulse method focuses on a bearing's own high-frequency impacts, so it can flag a bearing while overall vibration still looks normal.

What are the carpet and max values?

The carpet value is the background level of frequent weak pulses and warns of poor lubrication; the maximum value is the level of the strongest pulses and indicates actual surface damage.

Why are shock pulse readings normalised?

Because pulse levels depend on bearing size and speed, readings are normalised using bore diameter and shaft speed so that any bearing can be judged against the same green, yellow and red zones.