oiml recommendation r87 tare determination ben aitken trading standards officer trading standards...

OIML RECOMMENDATION R87TARE DETERMINATION

Ben AitkenTrading Standards OfficerTrading Standards MBIENew Zealand

Kevin Gudmundsson Legal Metrology AdvisorTrading Standards MBIENew Zealand

OIML Recommendation R87

Tare Procedures

Annex B OIML R87 (Informative)

Tare Procedures

R87 procedures permit the use of:

1. Unused dry tare

2. Used dry tare

Tare weight = term for weight of the packing material

Tare Procedures

Procedures permit the use of:

1. Unused dry tare– the weight of unused packing material of one pre-

package.

Empty packaging material supplied by the packer.

Tare Procedures

Procedures permit the use of:

2. Used dry tare– packing material that has been used as part of a pre-

package and that has been separated from the product and cleaned using normal household procedures used by consumers of the product

– (e.g. the material should not be dried in an oven).

Tare Procedures

2. Used Dry Tare

– In practise packaging material used for wet products such as chicken and other meats can be difficult to dry. With these products it is often best to wash the packaging material and dry with a cloth then allow it to dry overnight.

Tare Procedures

Tare weight includes the weight of all of the packing material

Tare Procedures

Determine the actual quantity of product in the pre-package as follows:

Actual Quantity of Product =

Weight of the Prepackage – Average weight of the packing material

The average weight of the packing material is referred to as the average tare weight (ATW).

Tare Procedures

Average Tare Weight – ATWTable B.1 Tare

Tare Procedures

Tare Procedures

Determine the unused dry tare or the used dry tare.

1. Randomly select an initial sample of 10 packing materials.

– These can be taken from an inspection lot (used dry tare) or from a lot of packing materials at the point of pack (unused dry tare).

– Note: in practise it is recommended to use unused dry tare if at all possible.

Tare Procedures

2. Determine the individual weight of each of the 10 packing material

3. Record the Nominal Quantity of the goods as labelled by the packer

4. Using Table 2 (R87) determine the amount of error allowed (T)

Tare ProceduresTable 2 (R87) - determine the amount of error allowed (T)

Nominal quantity of product (Qn) in g or ml

Tolerable Deficiency (T)a

Percent of Qn


g or ml

0 to 50 9 -50 to 100 - 4.5

100 to 200 4.5 -200 to 300 - 9300 to 500 3 -

500 to 1000 - 15100 to 10 000 1.5 -

10 000 to 15 000 - 15015 000 to 50 000 1 -

a T values are to be rounded up to the next 1/10 of a g or mL for Qn ≤ 1000 g or mL and to the next whole g or mL for Qn > 1000 g or mL.

Tare Procedures

5. Determine the average tare weight (ATW) and the standard deviation (s)

Table B.1 TareIf Then

The ATW is ≤ 10 % of the nominal quantity of

product

Use the ATW to determine the actual quantity of product in the pre-packages according to A.2 step 7.

The ATW is > 10 % of the nominal quantity and

s < 0.25 x T

Use a total of 25 packages to compute the ATW and determine the actual quantity of product in the pre-packages according to A.2 step 7.

The ATW is > 10 % of the nominal quantity and s > 0.25 x T

An ATW cannot be used. It is necessary to determine and to consider every individual tare weight.Determine the actual quantity of product in each pre-package according to A.2 step 7

Tare Procedures

Example Tare Procedure – Exercise

Tare Procedures

Tare Procedures

• Nominal Weight = 500g• 10% of Nominal Weight =

50 g• ATW = 4 g• 4 is ≤ 10% 500 g

Use Average Tare Weight

Tare Sample Tare Weight (g)

1 32 43 44 35 46 57 48 49 510 4

ATW 4

Standard Deviation (s) 0.66

Tare ProceduresTable B.1 Tare

If ThenThe ATW is ≤ 10 % of the

nominal quantity of product



s < 0.25 x T




Tare Procedures

Scenario 2

We calculate the ATW of our 10 packing material’s and it is >10% of the nominal quantity

Tare Procedures

Tare Procedures

Scenario 2• Nominal Quantity (Qn) = 180 g • ATW (10 packing materials) = 45.1 g • 10% of Qn = 18 g• ATW > 10% Qn (45.1 > 18)

We now need 1. To determine standard deviation of 10 packing

material weights, and2. To determine T (from Table 2 of R87)

Tare Procedures

Table 2 - Tolerable deficiencies in actual content for prepackages

Nominal quantity of product (Qn) in g or ml


Percent of Qn


g or ml

0 to 50 9 -50 to 100 - 4.5

100 to 200 4.5 -200 to 300 - 9300 to 500 3 -

500 to 1000 - 15100 to 10 000 1.5 -

10 000 to 15 000 - 15015 000 to 50 000 1 -

a T values are to be rounded up to the next 1/10 of a g or mL for Qn ≤ 1000 g or mL and to the next whole g or mL for Qn > 1000 g or mL.

Tare Procedures

Scenario 2• Nominal Quantity (Qn) = 180 g • ATW (10 packing materials) = 45.1 g • 10% of Qn = 18 g

• T = 4.5% of Qn (180*4.5%)• T = 8.1 g• 0.25 x T = 2.025• s = 0.737In this instance• s < 2.025

Tare Procedures

• Nominal weight (Qn) = 180 g• T = 8.1 g• 10% of Nominal weight = 18 g• Average tare = 45.1 g• s = 0.738• ATW > 10% of Nominal weight

(45.1 > 18 g)• s < 0.25 x T • 0.25xT = (0.25 x 8.1 = 2.025)

Use ATW of 25 packages

Tare sample Tare weight (g)

1 452 463 444 455 456 467 458 449 4610 45

Mean 45.1

s 0.738






s < 0.25 x T




Tare Procedures

The sample number is increased to 25. • Use the original sample of 10 packages and select a

further 15. • Use the ATW of the 25 packages.• Consider whether such action is common sense

– e.g. where the weight of the packaging is greater than it’s contents, such as with small tubes of ointment, but the tare weight is very constant, there is nothing to be gained from checking a further 15.

Tare Procedures

Tare Procedures

Scenario 3

We calculate the ATW of our 10 packing material’s and it is >10% of the nominal quantityandThe standard deviation (s) is greater than 0.25 x T

Tare Procedures

Tare Procedures

• If the average tare weight of the initial tare sample is greater than10% of the nominal quantity and

• the standard deviation is greater than 0.25 x Tan ATW cannot be used. – In this case it is necessary to determine every

individual tare weight.

Tare Procedures

• Nominal weight = 45 kg• T = 0.45kg• 10% of Nominal weight =4.5kg• Average tare = 34.85 kg• s = 0.215• ATW > 10% of Nominal weight

(34.85 > 4.5 kg)• s > 0.25 x T

(0.25 x 4.5 = 0.1125 kg)Use individual tare weights

Tare sample Tare weight (kg)

1 34.62 34.93 35.14 35.35 34.76 34.97 34.58 34.79 34.810 35.0

Mean 34.85

s 0.215






s < 0.25 x T




Tare Procedures

Non Average Tare Weight

1. Non-destructive Testing

2. Destructive Testing

Tare Procedures


• A Legal Metrology Official should always look to avoid destroying the manufacturers product, especially if it is high value.

• In some instance destructive testing may be unavoidable

Tare Procedures


Non-destructive testing

Non-destructive testing may be achieved at the packers premises by pre-weighing the packaging material before it is filled

Tare Procedures


• Pre-weighed packing material must be easily identifiable, consider using colour coding – A sequence of coloured ribbon or elastic bands

• The unique tare weight of each packing material must be recorded before it is filled– Consider using adhesive labels and recording the tare

on the package itself

Tare Procedures


• Place each pre-weighed packing material on the production line at randomly generated time intervals

• This method generally involves additional personnel

• It is advisable to include additional samples on the production line just in case some are missed

Tare Procedures


• This may be desirable in the case of small necked bottles with dense products in them. Emptying the product from these type bottles, then washing and drying them can be very awkward and time consuming.

Tare Procedures


Destructive Testing

• Pre-packages have to be opened to determine compliance.

• Often involves handling of the product which may render it unsalable

• May be the only option for some types of goods– e.g. Frozen food goods

Tare Procedures


Destructive Testing

• Packaging material for the tare test may be obtained by:– Co-operation of the packer or importer– Seizing goods if satisfied on reasonable grounds that

an offence has been committed– Arranging to purchase from the packer

Tare Procedures

Thank you for your attention

Any Questions?

Calculating Error

Calculate error for rice exercise

Gross – ATW = Actual Quantity

Actual Quantity – Qn = Error

Calculating Error

Gross – ATW = Actual Net QuantityActual Net Quantity – Qn = Error

No. Gross ATW Net Qn Error1 505 4 501 500 +12 505 4 501 500 +13 505 4 501 500 +14 504 4 500 500 05 505 4 501 500 +16 501 4 497 500 -3

Product: Rice Lot Size: 400 Sample Size: 50 Qn = 500 g T1 = T2 =

Number of Non-standard packages permitted =Gross ATW Net Qn Error Gross ATW Net Qn Error

1 505 4 501 500 1 33 506 4 502 500 22 505 4 501 500 1 34 506 4 502 500 23 505 4 501 500 1 35 505 4 501 500 14 504 4 500 500 0 36 506 4 502 500 25 505 4 501 500 1 37 504 4 500 500 06 501 4 497 500 -3 38 504 4 500 500 07 501 4 497 500 -3 39 503 4 499 500 -18 501 4 497 500 -3 40 502 4 498 500 -29 502 4 498 500 -2 41 503 4 499 500 -1

10 502 4 498 500 -2 42 504 4 500 500 011 500 4 496 500 -4 43 506 4 502 500 212 502 4 498 500 -2 44 503 4 499 500 -113 505 4 501 500 1 45 505 4 501 500 114 503 4 499 500 -1 46 503 4 499 500 -115 501 4 497 500 -3 47 506 4 502 500 216 504 4 500 500 0 48 505 4 501 500 117 504 4 500 500 0 49 502 4 498 500 -218 502 4 498 500 -2 50 506 4 502 500 219 504 4 500 500 020 500 4 496 500 -421 505 4 501 500 122 505 4 501 500 1 Total Production Error (TPE) =23 505 4 501 500 1 Average Error (AE) =24 501 4 497 500 -3 Sample Correction Factor (SCF) =25 502 4 498 500 -2 Standard Deviation (s) = 26 501 4 497 500 -3 SEL (s x SCF)= 27 503 4 499 500 -1 Weighted Average (SEL + AE) =28 505 4 501 500 129 505 4 501 500 1 # of Non-Standard Pre-packages:30 503 4 499 500 -1 # of Inadequate Pre-packages:31 501 4 497 500 -332 501 4 497 500 -3

oiml recommendation r87 tare determination ben aitken trading standards officer trading standards...

Documents