Accuracy class for gauges - Class 1,0 gauges - NS-5504 (Norwegian Standard)

G

Gandi

Guest
#1
Hi,

I have a lot of Class 1,0 gauges. According to NS-5504 (Norwegian Standard) the maximum deviation during calibration is 0,8% F.S. But, what do you do if you have a gauge that, during calibration, is only 1,2% F.S. Which will give it Class 1,6. Do you recommend the customer to throw it away? Or do you give the customer a certificate stating the class and results without saying more to the customer? Or do you put a sticker on the gauge, stating its new class?

Regards,

Anders
 

jfgunn

Inactive Registered Visitor
#2
This is a great question.

The ISO 17025 standard would have you report the measurments with uncertainties. The decision to pass or fail would be completely up to the customer.

In the real world, customers want to know if a gage passes or fails. Another issue is how you take measurement of uncertainty into account when making the Pass/Fail decision.

We take these situations on a customer by customer basis. We give the customers the following options:

1.) Pass / Fail based upon readings only while ignoring uncertainty.

2.) Readings and uncertainties only with no pass/fail statement.

3.) Pass/Fail based upon readings where the pass window has been expanded by a value equal to the uncertainty.

4.) Limited Calirbation where a gage is said to meet a different class and this new class is indicated on the calibration certificate. When choosing this option for plugs and rings customer need to let us know if we can change a gage from a Master (Bi-lateral tolerance) to a GO or NOGo as needed. You need to know what is more important. Would they rater have a Class X Master or a Class XX GO?

Whatever you do, you should spell out the options to the customer and let him/her decide. Just get your options and their response in writing.

You could also specify what your standard practice would be when quoting the customer.

Hope this helps.
 
G

Gandi

Guest
#3
My "problem" is that the customer is inhouse..... I'm running the calibration lab in our company, and calibrate a lot of gauges for another department. The gauges are mounted on equipment which is sent offshore. I'm sure none of the guys offshore look at the certificate. So, if a gauge had an accuracy of 5% instead of 0,8%, they wouldn't know....... So my option is to either throw the gauges in the thrash, or change the class by putting a sticker on the gauge notifying the users of the new class. I'll ask the person in charge.

But, is it an accepted practice to change the class of a gauge to a poorer one? I.e. from class 1,0 to class 1,6?

Thanks,

Anders
 
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