Creep — the exchange rate between degrees and years

The component is designed to last its full service life at its design temperature. Drag upward to run it hotter than that; drag down to run it cooler. The arrow keys do the same. End is as hot as this goes; Home is the coolest. The pale bar is the life it was supposed to have. Sound is off until you turn it on.

What you are looking at

Hold metal hot and loaded and it slowly changes shape, even under a stress it could carry indefinitely when cold. It is not yielding and it is not cracking: the atoms are simply rearranging, a little at a time, and the part is getting longer. Eventually it thins enough somewhere to let go.

How long that takes depends on time and temperature together, and the two are traded against each other. The same damage can be bought with a long spell at a moderate temperature or a short spell at a high one — and because the trade is exponential, a small step in temperature buys a very large amount of time.

So a component that drifts ten degrees above its design temperature has not lost ten degrees' worth of margin. It has lost half its life. Thirty degrees costs about four fifths of it, and fifty takes a decade down to a season.

The two things worth taking away

Temperature control is life extension. Nothing else available to an operator moves creep life as far as a few degrees does. A burner adjustment, a cleaned heat exchanger or a corrected instrument buys years — and the same few degrees the other way spends them.

There is nothing to inspect for, for most of the life. The metal is deforming a few millionths at a time, uniformly, with no crack to find. By the time anything is visible the remaining life is short. The instrument that would have caught this is a thermometer, read years earlier — which is why operating records matter more than inspection reports for plant that runs hot.

What is not verified

Stated plainly, because a piece whose value is trustworthiness should not overclaim. The first list is the part that would change how you read the result. The second is scope — true, worth saying, and not load-bearing.

• No engineer has reviewed this. If you are one and would check it, REVIEW.md says what would actually help and is meant to cost about fifteen minutes. The relation is the standard Larson-Miller parameter with an ordinary constant for steels, and the built-in checks confirm the arithmetic exactly — but that check is the author's own, not a plant or materials engineer's.
• The constant is a fitted number, not a law. Twenty is the usual starting value for steels; real materials are fitted individually and the value varies. Change it and every life on this page changes with it.
• One stress, held constant. Creep life depends on stress as strongly as it depends on temperature, and this piece holds stress fixed to isolate the temperature trade. A real assessment moves both.
• Extrapolation is the whole difficulty in practice. Design lives run to decades and test data does not, so the numbers that matter are always extrapolated from shorter, hotter tests — which is exactly the operation this relation was invented to perform, and exactly where it is least trustworthy.

Scope, for completeness. True of the model, and none of it changes the answer above.

• No damage accumulation, no history. Real components see varying temperature and accumulate damage in fractions; this shows steady operation at one temperature, which no plant does.
• The bulge drawn on the component is indicative. It shows that deformation is happening, not how much — the model gives a time to rupture, not a strain history.

Commissions

The subject changes; the method does not. If you have a failure mode, a mechanism, or a process that people keep getting wrong because the diagram cannot move, that is the shape of problem this suits. You get one file, the checks that hold it honest, and the notes explaining every decision including the ones that were reversed. Commissions start at £4,000 and take three to four weeks from an agreed brief. yinxueshi1017@gmail.com

Not commissioning anything? Still worth an email. If your version of this failed differently — other geometry, other numbers, a mechanism this piece leaves out — tell me in one line. Corrections are the main thing that decides what gets built next.