Annex D - Further Guidance on Re-Verification

Further guidance on re-verification

There have been a number of questions raised recently regarding when a weighing instrument may need to be re-verified. There has been guidance issued on this subject by the NMO in the document WM1003 (Version 3) that can be found at:

These notes are supposed to be read in conjunction with that document.

The criterion as to whether an instrument needs to be re-verified derives from the ability of an Inspector of Weights and Measures (or other authorised person) to disqualify the instrument in the first place. The general assumption is that if an instrument:

a)   Has fallen outside of its permitted tolerances
b)   Does not fully comply with the requirements which apply to it,
c)   In the opinion of the inspector, has undergone any alteration, adjustment, addition, repair or replacement that could affect its accuracy or function. an inspector has within his power the authority to disqualify the instrument.

It is advised that if you form the view that any of the above criteria has been met it is likely that the instrument should be re-verified.

The next question we must ask is what kind of alteration, adjustment, addition, repair or replacement would cause us to believe that an inspector may disqualify an instrument which therefore means that we must re-verify it.

Unfortunately, it is very difficult to offer clear guidance on this, as it will ultimately be decided by the view of the Inspector. This means that it will be decided on a “case by case” basis. Some of the questions that may help in resolving this are:

1. Could the accuracy of the instrument have changed?

If it is possible that the accuracy of the instrument could have changed because of any work that you have carried out, then it is recommended that you re-verify the instrument. It must be remembered that the work does not actually have to change the accuracy; it is a question of whether it could affect the accuracy that is important. The examples that are referred to in the NMO document are the change of a load cell or headwork in a weighbridge.

2. Could the change of a module affect the functionality of the metrological aspects of the instrument?

If the change of the module adds new functionality to the weighing aspects of the instrument, it is likely that it will need to be re-verified. An example of where and instrument would need to be re-verified would be if a software upgrade added extra weighing applications

3. Is the type approval certificate still applicable?

If you are the view that any alteration, adjustment, addition, repair or replacement means that the type approval certificate would no longer apply, the instrument will need a new or updated type approval and then be re-verified

4. Does the Declaration of Conformity (DoC) still apply?

If you believe that the because of the work that you have carried out, the original Declaration of Conformity may no longer apply to the machine, you will have to re-verify the instrument. This will obviously depend on how the original DoC is worded. An example of this may be; if the DoC specifies a location for the instrument or a serial number and the instrument is in a different place or has a different serial number, you will need to re-verify the instrument.

These questions are supposed to be guidelines to help you decide whether or not you may need to re-verify a weighing instrument. If the answers to any of them lead you to believe that an inspector may have a good reason to reject an instrument, it is advised that you re-verify it after you have undertaken any work.

Please remember it is the responsibility of the owner of the instrument to have it re-verified, not the responsibility of the company servicing or repairing the instrument.

If it is your view that the instrument should be re-verified and the owner of the instrument contradicts this view, you should ensure that the organisation, which owns the machine, is informed of your view. This should be in writing to a responsible person in that organisation and should clearly state that its continued use may be illegal if it is not verified.

If you have decided that the instrument should be re-verified, this must be done as soon as is practicable after the work has been completed. The local weights and measures department should be notified when the verification has been completed.

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