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Anonymous Poster #1

Quality and Purity

08/07/2011 4:54 AM

What is the difference between Quality and Purity. If something is not of the right purity then it will not be of the right quality, is this correct? However if something is of the right purity can it still fail to be of the right quality.

I have earched the internet but have failed to come up with anything that clears this up for me.

Thanks in advance for your help

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#1

Re: Quality and Purity

08/07/2011 4:59 AM

For an interesting take on "quality", you might enjoy Robert W. Pirsig's Zen and the Art of Motorcycle Maintenance.

Or a dictionary.

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#2

Re: Quality and Purity

08/07/2011 5:52 AM

Quality is a general term, purity is much more specific.
You could have a product which is incredibly pure but is of the wrong quality, say the spec' calls for it to be a dilute product not 100% pure.
Quality depends on a specification, whereas purity is a measurable attribute.
Without a spec' or a general concept like 'fit for purpose' quality is meaningless.
Del

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#3

Re: Quality and Purity

08/07/2011 9:49 AM
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#4

Re: Quality and Purity

08/07/2011 10:10 AM

In my own interpretation my answer would be " pure copper transmission wires have low quality to be use for power transmission systems"

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#5

Re: Quality and Purity

08/07/2011 1:54 PM

Philip Crosby, one of the grand old men of quality assurance said something like this,

"A VW with a Mercedes price tag is poor quality."

"But, a Mercedes with a VW price tag is also poor quality."

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#6
In reply to #5

Re: Quality and Purity

08/07/2011 2:04 PM

Was he having an off day? That's a cr*p explanation of anything (IMO)
Del

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#7
In reply to #6

Re: Quality and Purity

08/07/2011 2:20 PM

Nah, he was just trying to make the point that quality is achieving exactly, no more, no less, than what you meant to.

He was an intellectual and a manager. You gotta cut him some slack.

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#8

Re: Quality and Purity

08/07/2011 3:50 PM

Quality is conformance to specifications.

Purity has to do with the composition or makeup of a substance- it is a measure of the relative freedom from contaminants.

Quality is a general term applicable to a broad range activities.

Purity is a more specific term elated to chemical composition of materials.

Milo

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#9
In reply to #6

Re: Quality and Purity

08/07/2011 11:39 PM

one of my hero's

What he actually said is:

Quality is conformance to requirements! nothing more, nothing less.

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#10
In reply to #8

Re: Quality and Purity

08/08/2011 1:32 AM

Quality - an attribute of a product or service that is intrinsic and is measured and accepted, as agreed between the buyer and seller. quality as agreed can be benchmarked by a reference to any or a combination of an approved sample, a standard, a code, a drawing or a specification. the benchmarking can provide for tolerances depending on agreement between buyer and seller.

Purity - one of the measurable relative attributes of quality. purity is often referred to whilst talking about chemical composition. however purity can be a term used for many measurable parameters whilst benchmarking. purity when expressed as a fraction or a percentage is the relative correctness of the measured parameter wrt the exact value designed for. 1 minus the fraction or 100 minus the percentage denotes the quantum of contaminant present.

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#11

Re: Quality and Purity

08/08/2011 6:43 AM

Purity = objective. Quality = subjective. Usability at some point.

This may help. jt

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#12
In reply to #1

Re: Quality and Purity

08/08/2011 10:29 AM

For an interesting take on "quality", you might enjoy Robert W. Pirsig's Zen and the Art of Motorcycle Maintenance.

I read that years and years ago and it was one of the best i have ever read. There is a fine line between genius and insanity.

Ron

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#13

Re: Quality and Purity

08/08/2011 11:39 AM

What about beer? Purity of water with quality of ingredients!

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#14

Re: Quality and Purity

08/08/2011 11:50 AM

I encountered this problem in a shipyard where I worked in the 1970s, the rolled steel (12mm thick) plates were of the right quality (purity) steel, but during the rolling proccess slag was rolled out into a thin layer midway in the plates, thus the quality was the problem, this was discovered using an ultra-sound device!

Spencer.

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#15
In reply to #14

Re: Quality and Purity

08/08/2011 12:20 PM

The slag was entrained during ingot pouring. (I'm not aware of any continuous casters back in the 1970-'s)

Or it could have been insufficient cropping of the ingot top.

To your point, from a routine product check chemical analysis, yes, the material probably met specification- for chemical analysis.

However, for Entrained slag this was likely rejectable only upon finding it and calling it an injurious defect, there is no requirement in ASTM A6 , 131, or others that called this out specifically at the time.

Now, ASTM A6 General Requirements for rolled Structuiral steel bars, plates shapes and sheet piling, Supplemental requirement S8, Ultrasonice examination can be specified to assure that any material with such slag entrainment is rejected.

Semantically, one could argue that the steel containing enmtrained slag is not pure steel, it is steel contaminated with contained slag nonmetallics. And so lacking in 'Purity.' But since this is detected by physical means (UT inspection) rather than chemical analysis, we tend to not look at it as a chemical issue as much as an "internal cleanliness / homogeneity" issue.

But your point is exactly right using the lens of ASTM A6, section 10 Quality, item 10.1: the plates you described do not meet the quality standard of being "free of injurious defects and shall have a workmanlike finish..."

Specifications for steel products need to cover more than just chemical composition: mechanical properties, compliance to required processing paths (ie q&T rather than just heavy Cold work, compliance to dimensional and reduction ratios specified, and supplemental requirements for metallurgical structure- Grainsize, and metallurgical structure, frredom from nonmetallic inclusions beyond acceptable levels, Impact test minima Weldability, Bendability, and even how the product is marked and packaged and other requirements not known to me (flatness, straightness, square of cut, type of cut, whether or not it was vacuum degassed, etc. etc.) have a place in determining whether a shipment is a "quality delivery" or not.

Milo

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#16

Re: Quality and Purity

08/08/2011 12:54 PM

I hope others have given you a feel for the meaning. In some cases, they are totally unrelated.

Rolls Royce makes a quality car. How does purity apply at all in this case?

A chemical may be near 100% purity, but if it does not meet the required physical specifications (say granule size or bulk density) it is of poor quality.

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#17

Re: Quality and Purity

08/08/2011 4:25 PM

= Purity

= Quality

If you don't know the difference I'm not going bar hopping with you.

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#18
In reply to #17

Re: Quality and Purity

08/09/2011 4:35 AM

Three thumbs up on that GA!

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Anonymous Poster #1
#19
In reply to #17

Re: Quality and Purity

08/09/2011 7:51 AM

Ah, now I get it, GA. Best explanation by a mile. Did not find that in the dictionary !!!

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#20
In reply to #17

Re: Quality and Purity

08/14/2011 8:21 AM

hahaha, true that is.!

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