What does a numerical rating mean? Mechanical equipment or device

Click For Summary

Discussion Overview

The discussion centers on the meaning of numerical ratings assigned to mechanical equipment or devices, particularly in relation to their operational lifespan and performance expectations. Participants explore the implications of these ratings, including how they are determined and what they signify regarding the reliability and longevity of the equipment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the rating indicates that the operation was performed until failure or if it is based on accelerated testing and predictions.
  • Another participant suggests that ratings may be based on material fatigue and mentions the automotive industry's use of accelerated tests to verify longevity.
  • A participant shares personal observations of equipment undergoing testing for a certain number of cycles until wear or damage occurs, though specifics are not provided.
  • One viewpoint emphasizes that nameplate ratings serve a legal purpose, indicating performance standards and voiding warranties if exceeded, but the basis for these ratings may vary.
  • Another participant interprets ratings as predictions of life expectancy or expected uses, providing an example of a spring's rating as a measure of its operational cycles.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of ratings, with no consensus reached on their exact meaning or the methods used to determine them. Some suggest they are based on testing, while others emphasize legal implications.

Contextual Notes

Limitations in understanding the basis for ratings are noted, including the potential variability in how manufacturers determine these numbers and the generality of the predictions involved.

symbolipoint
Homework Helper
Education Advisor
Gold Member
Messages
7,642
Reaction score
2,080
TL;DR
What exactly does "Rating" mean for a piece of equipment or mechanical device?
A certain mechanical appliance or device is given a rating that says, a certain operation or a certain movement can be performed some specified thousand times. What does the rating really mean? Was that movement or operation performed until the piece failed? Does it mean some advanced test was made in an abbreviated or accelerated fashion, and an estimate or prediction was made to give the number of times as a rating? Should the person receiving the information on a rating include some range up or down from the rating?
 
Engineering news on Phys.org
  • Like
Likes   Reactions: russ_watters and jack action
symbolipoint said:
TL;DR Summary: What exactly does "Rating" mean for a piece of equipment or mechanical device?

Was that movement or operation performed until the piece failed?
I've actually watched equipment do this. Not necessarily to complete failure but X cycles until a certain amount of wear or damage has occurred. This particular case was a cable assembly used in lab-type test equipment. Sorry I can't tell you the number of cycles.
 
  • Like
Likes   Reactions: symbolipoint
I look at the nameplate rating as primarily a legal thing. It is the standard of performance that the nameplate warrants. Exceeding the nameplate rating voids all guarantees and warranties of performance.

How the manufacturer set the numbers on the nameplate can not be determined in the general case. They may or may not be tied to factual evidence.
 
  • Like
Likes   Reactions: russ_watters, symbolipoint and DaveE
Something about the meaning, as indicated in one of the links says, "life expectancy" or "expected number of uses". That is likely as good as I will find. Just a prediction based on some testing or based on some kind of model.

Still very very general, if a spring has a rating of 1600 cycles, this is a prediction that it can be stretched & released OR squished & released 1600 times to still work at its best.

That seems to be just what "rating" means.
 

Similar threads

Replies
8
Views
4K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 109 ·
4
Replies
109
Views
12K
  • · Replies 15 ·
Replies
15
Views
3K
  • · Replies 17 ·
Replies
17
Views
3K