New research and techniques of World Maintenance

New research

Quite apart from greater expectations, new research is changing many of our most basic beliefs about age and failure. In particular, it is apparent that there is less and less connection between the operating age of most assets and how likely they are to fail.

Figure 1.2 shows how the earliest view of failure was simply that as things got older, they were more likely to fail. A growing awareness of 'infant mortality' led to widespread Second Generation belief in the "bathtub" curve.

However, Third Generation research has revealed that not one or two but six failure patterns actually occur in practice. This is discussed in detail later, but it too is having a profound effect on maintenance.

New techniques

There has been explosive growth in new maintenance concepts and techniques. Hundreds have been developed over the past fifteen years, and more are emerging every week.

Figure 1.3 shows how the classical emphasis on overhauls and administrative systems has grown to include many new developments in a number of different fields.

The new developments include:

decision support tools, such as hazard studies, failure modes and effects analyses and expert systems
new maintenance techniques, such as condition monitoring
designing equipment with a much greater emphasis on reliability and maintainability
a major shift in organizational thinking towards participation, team-working and flexibility.

A major challenge facing maintenance people nowadays is not only to learn what these techniques are, but to decide which are worthwhile and which are not in their own organizations. If we make the right choices, it is possible to improve asset performance and at the same time contain and even reduce the cost of maintenance. If we make the wrong choices, new problems are created while existing problems only get worse.

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Top 8 Reasons for Mechanical Seal Failure and How to Prevent Them

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Grounding brush discharge monitoring

In recognition of the possibility of static charge build up in condensing steam turbines, API 612 (2005) specifies that grounding brushes be installed. The electrical flow to ground through these brushes be monitored and useful information can be extracted. This article carries excerpts from the paper, “Babbitted bearing health assessment” by John K Whalen of John Crane, Thomas D Hess of Chestnut Run, Jim Allen of Nova Chemicals and Jack Craighton of Schneider Electric. Grounding brushes take current from the rotor to ground so that a charge does not build up on the rotor to the point where it discharges to ground though the best path possible – which is usually the closest point between the rotor and stator which is usually (hopefully) the point of minimum film thickness in a bearing. Typically this point of minimum film thickness is found in the active thrust bearing (as will be shown later). Shaft grounding brushes serve two purposes. The brushes are able to transmit modest amo...

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Dry Gas Seal Failure Modes

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Preventing Motor Bearing Damage from Shaft Current with the AEGIS® Ring

Electric motors are the workhorses of modern industry, powering everything from pumps and fans to conveyor belts and heavy machinery. But these vital components are not immune to wear and tear, and one common problem that can lead to premature motor failure is bearing damage caused by shaft current. Shaft current is a type of electrical discharge that occurs when there is a voltage potential between the motor shaft and the bearing, resulting in the flow of electrical current through the bearing. This current can cause a range of problems, including pitting and fluting of the bearing surfaces, which can lead to premature wear and failure. Shaft current Motor shaft current can have several harmful effects on bearings, including: 1. Bearing pitting and fluting: Electrical discharges can cause tiny pits and flutes to form on the bearing surfaces, leading to premature wear and failure. 2. Bearing noise and vibration: Shaft current can cause ...

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John Crane's Type 28 Dry Gas Seals: How Does It Work?

How Does It Work? Highest Pressure Non-Contacting, Dry-Running Gas Seal Type 28 compressor dry-running gas seals have been the industry standard since the early 1980s for gas-handling turbomachinery. Supported by John Crane's patented design features, these seals are non-contacting in operation. During dynamic operation, the mating ring/seat and primary ring/face maintain a sealing gap of approximately 0.0002 in./5 microns, thereby eliminating wear. These seals eliminate seal oil contamination and reduce maintenance costs and downtime. John Crane's highly engineered Type 28 series gas seals incorporate patented spiral-groove technology, which provides the most efficient method for lifting and maintaining separation of seal faces during dynamic operation. Grooves on one side of the seal face direct gas inward toward a non-grooved portion of the face. The gas flowing across the face generates a pressure that maintains a minute gap between the faces, optimizing flui...

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