Roundings between imperial and metric units
Roundings between imperial and metric units
(OP)
Here's one that's been bounding around for a while.
OK, when using a component from a catalogue that was originally rated to 10000psi for example it is often the case to see the equivalent metric rating to 690 Bar.
As long as it is proven to do both values that's fine.
However, if you take a component that only has a rating of 10000psi and try and install it into a design that has metric parameters a slight problem in roundings occurs.
If it's rated at 10000psi is it acceptable, safe and prudent to accept that it is also rated to 690 Bar or should the rating be converted to 689 Bar.
In an ideal world we wouldn't have the problem but we do, as a middle aged Englishman I've never used imperial units in calculations, always metric, I'm sure there are others my age who have never used metric. In the USA it is predominately imperial units while the rest of the world predominately uses metric. the world is in a state of flux and I don't want to enter into an argument about which is best or sticking to one and avoiding the other.
What are your thoughts?
As an example I have always taken the conservative approach of 689 Bar and this hasn't caused any problems until we had a design that had to meet 10000psi and we put a 15000psi rated valve on it because of the rounding issue (a small cost was incurred, negligible in the scheme of things).
OK, when using a component from a catalogue that was originally rated to 10000psi for example it is often the case to see the equivalent metric rating to 690 Bar.
As long as it is proven to do both values that's fine.
However, if you take a component that only has a rating of 10000psi and try and install it into a design that has metric parameters a slight problem in roundings occurs.
If it's rated at 10000psi is it acceptable, safe and prudent to accept that it is also rated to 690 Bar or should the rating be converted to 689 Bar.
In an ideal world we wouldn't have the problem but we do, as a middle aged Englishman I've never used imperial units in calculations, always metric, I'm sure there are others my age who have never used metric. In the USA it is predominately imperial units while the rest of the world predominately uses metric. the world is in a state of flux and I don't want to enter into an argument about which is best or sticking to one and avoiding the other.
What are your thoughts?
As an example I have always taken the conservative approach of 689 Bar and this hasn't caused any problems until we had a design that had to meet 10000psi and we put a 15000psi rated valve on it because of the rounding issue (a small cost was incurred, negligible in the scheme of things).





RE: Roundings between imperial and metric units
Fawkes, you are quite right, this stuff has been going round and round for a very long time and, rivers of ink have been employed to explain and satisfy the preferences of the users.
Here are some examples of what I am talking about:
thread404-236095: Design for multi-country manufacture - Metric vs. inch stock, thread194-234547: What should be a simple Pressure equation question, thread404-87352: unit conversion, thread769-106538: Who 'Invented' Metric.
I hope you will have the time to read them all and their related links.