1. Risk Management with Minimum Weight
Conference Centre, Centurion
August 1st
Denis LOUVEL, MT-SI
Risk Management with Minimum Weight

2. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
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For internal use - Confidential

3. Introduction
Many companies may be unaware that their weighing instruments do not meet their process accuracy requirements.
An analysis of weighing instruments is imperative in providing data which can be used to minimize non conformity related to accuracy.

4. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
To shift Highlight
Click the arrow, press shift key and move top or bottom
For internal use - Confidential

5. Reading, Rounding and Relative error
All balances generate a risk during weighing
This phenomenon is not limited to balances
It occurs for all instruments having a digital display (e.g. a voltmeter, a thermometer, a speed meter, etc.)
The weight measured by the balance is not the weight displayed by the balance
Amazing but true!!
Let me explain to understand this risk with a closer look to the balance digital display

6. Reading, Rounding and Relative error What you see is NOT what you get
To each weight displayed corresponds a set of measured weights limited by 2 changeover points (yellow circles).
This set of values generates an ambiguity during the conformity assessment of a weighed product.
The range of the measured weights before rounding (e.g g – 1999.5 g = 1 g ; g – 2000.5 g = 1 g) corresponds to the balance readability d.
The official name for d is "actual scale interval".

7. Reading, Rounding and Relative error
The relative error depends on the displayed mass
With a displayed weight of 2000 g, the relative error is then:
With a displayed weight of 200 g, the relative error is then:
With a displayed weight of 20 g, the relative error is then:

8. Reading, Rounding and Relative error
We can plot the relative error E%, (ratio between d and the displayed weight, m)
The relative error becomes increasingly larger as the load approaches zero.

9. Reading, Rounding and Relative error
If the user wants to guarantee a weighing of 0.5 %, the minimum weight with this balance will be 200 g (red dotted lines).

10. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
To shift Highlight
Click the arrow, press shift key and move top or bottom
For internal use - Confidential

11. Weighing Range Red or Green
With a relative error of 0.5%:
Below 200 g (red area) the weighing is not safe
Above 200 g (green area) the weighing is safe
WEIGHING RANGE

12. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
To shift Highlight
Click the arrow, press shift key and move top or bottom
For internal use - Confidential

13. Minimum Weight, MW Simple calculation
The definition of the minimum weight is based on the same formula but few changes are necessary.
with:
d, is the actual scale interval
Acceptance limit is the relative error (E%) as percentage replaced by the acceptance limit (always defined by the user)
The weight displayed m becomes the minimum weight “MW ”

14. Minimum Weight, MW A better definition for MW
As the actual scale interval, d, doesn't show the quality of a measurement, it is better to replace d by the balance uncertainty U.
This leads to a minor change in the formula.
d is replaced by the balance uncertainty U
MW is still the Minimum weight
The Acceptance Limit, in percentage, is always defined by the user
A last improvement is necessary.
It consists to account the Safety Factor defined by the user.

15. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
To shift Highlight
Click the arrow, press shift key and move top or bottom
For internal use - Confidential

16. Safety Factor, SF The safety factor accounts for:
changes during working conditions
different people working with the instruments
historical data of the weighing instrument verification
therefore and not to be forgotten, economic factors
changes that could affect measurement in daily routine use
A safety factor equal to 1 reflects the balance uncertainty only at the point and time when it was last calibrated with standards weights.
In the worst case, it can happen that the temperature vary right after the calibration, thus leading to an increase of the measurement uncertainty and consequently out-of- specifications results.
Therefore a safety factor >1 adds safety to the manufacturing process.
Typically a safety factor between 2 and 5 is recommended.

17. Safety Factor, SF The user decides what factor to apply.
If the weighing is critical, a safety > 2 is necessary.
Today, no tables are available to define a safety factor.
As a general rule of thumb, within an industrial context, a safety factor of at least 2 is always suggested – even if everything appears to be under control.

18. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
To shift Highlight
Click the arrow, press shift key and move top or bottom
For internal use - Confidential

19. Safe Weighing Range, SWR Red, Orange and Green like traffic lights
The safety factor improves the weighing:
In the red area, the weighing is not safe
In the orange area, the weighing is safe, but the safety factor is not fulfilled
In the green area, the weighing is fully safe
SAFE WEIGHING RANGE

20. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
To shift Highlight
Click the arrow, press shift key and move top or bottom
For internal use - Confidential

21. GWP Verification® A scientific approach to assess a process
With GWP® (GWP = Good Weighing Practice), the METTLER TOLEDO service, you can assess the risk
GWP Verification® consists to establish the link between the balance performance (its uncertainty) and the acceptance limits defined by the user.
GWP Verification® applies to all models and brands of weighing instruments and to all balances in the production field.

22. GWP® Life Cycle Management
GWP®, the science-based standard for efficient life-cycle management of weighing equipment.
GWP® gives clear answers how to specify and calibrate balances and scales – covering every relevant step in the equipment's life cycle.
GWP is the global weighing guideline for managing of weighing instruments. It helps the user get accurate results at all times and guides them in five simple steps, following the life cycle of the instrument. In each of these important 5 steps, GWP helps the user make the right decisions.
->>>> Allow me to highlight each of these 5 steps briefly in the subsequent slides. 33

23. Certifies the accuracy of the scale for the weighing process
GWP® Verification
Certifies the accuracy of the scale for the weighing process
For every instrument
Documents whether the accuracy of the scale, based on minimum weight and safety factor, satisfies the process requirements
Sample
Determines the minimum weight based on the calibration of the scale

24. GWP® Verification
Analysis of the scales and their accuracy in the process
Recommendations for measuring equipment monitoring based on risk analysis
Complete documentation
Overview of the status of all scales
Training

25. Agenda 1 Introduction 2 Reading, Rounding and Relative error 3
Weighing Range 4
Minimum Weight, MW 5
Safety Factor, SF 6
Safe Weighing Range, SWR 7
GWP Verification® 8
ISO 9001:2015 9
To shift Highlight
Click the arrow, press shift key and move top or bottom
For internal use - Confidential

26. ISO 9001:2015 and Weighing GWP complies with Risk-based thinking
One of the key changes in the 2015 revision of ISO 9001 is a focus on risk-based thinking.
Whilst risk-based thinking has always been a part of ISO 9001, the 2015 version gives it increased prominence by building it into the whole management system.
In previous editions of ISO 9001, a clause on preventive action was separated from the whole.
The aim is to establish a systematic approach to considering risk, rather than treating “prevention” as a separate component of a quality management system.
Risk-based thinking is part of the process approach.
ISO 9001:2015
0.3.3 Risk-based thinking
Risk-based thinking is essential for achieving an effective quality management system. […]
To conform to the requirements […] an organization needs to plan and implement actions to address risks and opportunities.
For internal use - Confidential

27. Thank you for your attention
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