Show Machines as a Series Arrangement of Parts in a Reliability Block Diagram if You Want to Eliminate Defects and Failure

All operating plant, equipment and machinery are a series arrangement of parts. When a critical part fails the machine fails. How a machine is built and how each of its parts are interconnected is in its engineering drawings. The machine works properly when all its components operate properly.

The engineering logic of how machine parts work together is shown in their Reliability Block Diagram. The Reliability Block Diagram is a powerful reliability analysis tool for eliminating the causes of equipment failures.


Slide 28 – A Machine Is A Series Arrangement of Parts Operating Concurrently. Which Parts will Cause the Machine to Fail Can Be Seen in a Reliability Block Diagram


What is a machine? When you look at a machine you see a complete piece of equipment. You see an assembly of many parts working together. Expand the machine out to view its internals and you’ll find a series arrangement of parts. The electric motor shown in the slide above is made of many separate parts, but we consider it as a single piece of equipment.

Within a piece of equipment each component is put together one to the other. Part by part they join to work as a sub-assembly. Sub-assemblies become major assemblies, and major assemblies connect to become the whole machine. The drawing on the slide of an electric motor drive end bearing arrangement is an example of a sub-assembly. The engineering drawings of a machine explain how the parts form assemblies to become the complete operating equipment.

Every machine is built from individual parts. All machinery and equipment are a series arrangement of parts. If we laid each part out in the order it was assembled we would get a sequence of components in a series arrangement of parts.

Show the Series Arrangement of Parts in a Reliability Block Diagram

We could draw this series arrangement of parts on paper as a row of boxes connected by arrows. Such an arrangement of boxes and arrows in a drawing is known as a Reliability Block Diagram. An example of a Reliability Block Diagram for the motor drive-end bearing arrangement is shown at the top of the slide. Each component in the sub-assembly drawing is placed in the Reliability Block Diagram in the order it works when the machine operates. The Reliability Block Diagram makes it completely clear that the assembly is a series arrangement of parts.

If any part in the sequence fails, then the series is broken, and the machine breaks down. For example, if the boxes that represent the lubricant had a reliability of zero, then the reliability of the whole series falls to zero and the bearing assembly fails, which leads to a machine breakdown.

You can think about the string of parts in machinery as a DNA sequence in the human genome. If our DNA is harmed, or contains a fault, then our bodies will suffer the consequential effects. It is the same in machinery and equipment as well—if individual parts contain defects or faults they will fail at some time in future when the circumstances arise that trigger the defect to become a failure.

Once you have the Reliability Block Diagram you do “what-if” scenarios to identify the defects that can happen to each part. What defects will prevent each part from being 100% reliable? Then you decide how to proactively eliminate each defect’s causes so the defect can never exist in the part and the machine will never fail from the defect.


This slide is a companion to the new Industrial and Manufacturing Wellness book. The book has extensive information, all the necessary templates, and useful examples of how to design and build your own Plant Wellness Way enterprise asset life cycle management system-of-reliability. Get the book from its publisher, Industrial Press, and Amazon Books.

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