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O-ring and Seal Design Theory

The use of an o-ring as a seal is mainly to prevent the transfer of fluid (liquid, solid or gas) between two or more regions. The components of the seal are the o-ring itself and the contact surfaces. The elastomeric o-ring relies on a compressive force acting on the o-ring to prevent the transfer of fluid between regions. Successful seal design ensures adequate seal compressive force while optimizing the destructive stress acting on the o-ring as a result of the compression or of the environment.

Three Models for Characterizing Viscoelastic Behavior Are:

1. Maxwell Model (dashpot and spring in series)
2. Kelvin (Voigt) Model (dashpot and spring in parallel)
3. Standard Linear Solid (dashpot and spring in series with a spring in parallel).*

O-ring and Seal Design Topics

* © Photographer: David Lemery of Milpitas, California, USA

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What Does The “O-Ring” Theory — Named After The Challenger Disaster — Mean For Us?

What we can learn from an economic theory of development, that many of us have not heard of.

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The 1986 Challenger shuttle explosion’s culprit — the “O-Ring” — inspired the name of Michael Kremer’s “O-Ring” production function. What is an “O-Ring”? And how could it caused an explosion of an entire space shuttle 73 seconds after launch, killing seven astronauts?

Anyone who has seen an O-Ring will not find it significant. It is a rubber ring that seals two machine joints together, to prevent any air from leaking. Yet, the failure of this small part led to the disaster. The O-Ring’s inability to seal the joints led to gas leaking, which led to the explosion of a booster, leading to the shuttle’s explosion. All in rapid succession.

It did not matter that everything else went right.

As Kremer describes in his seminal paper, published in 1993, setting out the production function -

Production consists of many tasks, all of which must be successfully completed for the product to have full value.

I repeat: production consists of many tasks, all of which must be successfully completed for the product to have full value.

Kremer aptly named this theory after the Challenger shuttle explosion’s culprit. It is probably the starkest example of how the O-Ring production theory operates in practice. The single failure of the O-Ring, an insignificant often overlooked part, led to catastrophic failure.

However, the starkness of that example should not detract from the generality of the theory’s application. In a less stark example in the paper, Kremer observed –

Companies can fail due to bad marketing, even if the product design, manufacturing, and accounting are excellent.

Careful consideration of this production function can explain and provide a lot of insight into what goes on in our life, our workplaces, and our economy. And perhaps how to make sure that we can…