M-05—Standards required for the initial and subsequent inspection of weighing devices

Category: Mass
Document(s): W&M Regulations 172, NAWDS
Issue Date:
Effective Date:
Supersedes: M-05 (rev. 4)


Table of contents


1.0 Purpose

The purpose of this bulletin is to indicate the standards and test loads required for the initial and subsequent inspection of both non-automatic weighing devices (NAWDs) and automatic weighing devices (AWDs).

2.0 Background

In order to ensure that an appropriate amount of test standards is available to conduct a satisfactory inspection, the minimum amount of test standards, as stipulated in section 3.0 below, must be made available for both the initial and subsequent inspections of a weighing device. This minimum amount of standards applies regardless of location, road restrictions or other annually recurring events such as spring breakup.

For situations not addressed in the bulletin or in other exceptional circumstances, the Regional Gravimetric Specialist should be consulted to determine the appropriate amount of test standards and test loads required for the inspection. It is important that the required amount of test standards is neither increased nor decreased without appropriate consideration to the effect this will have on the ability to perform an adequate inspection and to ensure that a company does not find itself in a competitive disadvantage because of the change.

Note 1: If Measurement Canada test standards are used for inspections, they are to be used for inspection purposes only and are not intended to be used to install, calibrate or adjust a device prior to or following an inspection.

Note 2: For the purposes of this bulletin, requirements and capacities in pounds shall be determined by multiplying the number of kilograms shown by 2. Max and capacity shall be considered synonymous.

Note 3: When loading a weighing device with test standards and other test loads, care must be taken to ensure that the load is stable and properly supported. If at any time the ability to safely apply the required load is in doubt, the Regional Gravimetric Specialist should be consulted to discuss changes to the test load requirements.

3.0 Required test standards

The following outlines the minimum acceptable amount of test standards and test loads suitable for the inspection of a weighing device as described below. The Regional Gravimetric Specialist may amend these requirements for a particular installation.

3.1 Non-automatic weighing devices

3.1.1 All devices

Subject to subsections 3.1.2, 3.1.3 and 3.1.4 below, test standards to Max (100% capacity) shall be used for the inspection, except that a strain or substitution load may be used to increase the tested capacity, provided that test standards of at least ½ Max (50% capacity) are used.

If the device has a repeatability error:

Note 4: The repeatability error is to be determined with a load equal to the amount of test standards available by placing it 3 times on the load receiving element in approximately the same location each time. Repeatability is to be assessed using the Break Point Determination procedure (Field Inspection Manual—Automatic Weighing Devices and Field Inspection Manual—Non-Automatic Weighing Devices, Appendix III).

3.1.2 Large capacity devices (except railroad and combination rail/vehicle scales)

3.1.2.1 At least 10 000 kg of test standards is required for the inspection of a large capacity weighing device where:

20 000 kg < Max ≤ 100 000 kg

3.1.2.2 At least 20 000 kg of test standards is required for the inspection of a large capacity weighing device where:

100 000 kg < Max ≤ 200 000 kg

3.1.2.3 At least 10% Max test standards is required for the inspection of a large capacity weighing device where:

Max > 200 000 kg

Unless test standards to 100% Max is available, the large capacity weighing devices identified above shall be tested to capacity using a combination of test standards and strain loads following the procedure for conducting strain load testing as outlined in section 4.0 below.

3.1.3 Railway or combination railway/vehicle scales

Unless test standards to 100% Max is available, the large capacity weighing devices identified above shall be tested to capacity using a combination of standards and strain loads following the procedure for conducting strain load testing as outlined in section 4.0 below.

3.1.4 Hopper and tank scales

3.1.4.1 Scales up to 1 000 kg capacity: test standards for a full capacity (Max) test.

3.1.4.2 Scales over 1 000 kg capacity, but less than or equal to 10 000 kg capacity: at least 1 000 kg of test standards.

3.1.4.3 Scales over 10 000 kg capacity: test standards of at least 10% Max.

Hopper and tank scales shall be tested to capacity using a combination of standards and substitute loads following the procedure for conducting substitution tests as outlined in section 4.0 below. The minimum amount of standards required is set out above. More standards, and therefore fewer required substitutions, may be used to facilitate testing. If the development of a substitute load is not practicable, strain loads may be employed instead.

3.2 Automatic weighing devices

3.2.1 Automatic discontinuous totalizing weighing systems—bulk weighers

Test standards that comply with the requirements of section 3.1.4 above for NAWDs are required for a similar device.

Automatic discontinuous totalizing weighing systems should be tested to capacity using the known standards and substitute loads following the procedure for conducting substitution as outlined in section 4.0 below. If the development of a substitute load is not practicable, strain loads may be employed instead. Product testing will likely be required to ensure the system is functioning correctly. See the Field Inspection Manual—Automatic Weighing Devices for more information.

3.2.2 Automatic continuous totalizing weighing systems—conveyor belt scales

Sufficient test standards to test a suitable NAWD to be used as a reference scale for the product test. See the Field Inspection Manual—Automatic Weighing Devices for more information on the development of a suitable test load.

3.2.3 Automatic catch weighing devices—overhead rail or belt scales

Test standards as required by section 3.1.4 of the NAWD requirements listed above for a similar device.

3.2.4 Automatic in-motion railway scales

Test standards as required by section 3.1.3 of the NAWD requirements listed above.

3.2.5 Other automatic weighing devices or systems

Test standards as required by section 3.1 of the NAWD requirements listed above for a similar device.

4.0 Substitution and strain tests

When the amount of test standards available is less than Max (NAWD) or capacity (AWD), strain or substitution tests must be used to extend the range of testing.

Strain tests

Strain tests shall be conducted on large capacity scales when the amount of standards available is less than the capacity of the device. Strain loads shall be selected to allow testing throughout the range of the device and especially through the typical gross and tare weighing ranges.

Substitution tests

Substitution tests are generally only appropriate when the inspector has adequate control over the weight of the substitute test load (within 0.1 e). This effectively restricts its use to tank and hopper scales weighing liquid or fine granular products.

Further details on the minimum amount of standards and manner of performing such tests can be found in section 13 of Part 3 of the Field Inspection Manual—Non-Automatic Weighing Devices. (STP-13)

Product tests

Product tests are used in addition to, or in place of, testing with known standards. Many automatic weighing systems as well as some non-automatic weighing systems may be tested with the aid of a product test. Please consult the appropriate standard test procedure to determine if a product test is required or suggested for the device under test.

5.0 Restrictions

5.1 Where sufficient test standards and other loads are not available to test to maximum approved capacity during initial inspection of large capacity scales, the device will be derated to the inspected and certified capacity.

5.2 Whenever the capacity of a device is derated from the approved or previously certified capacity, this derated capacity must be marked on the device.

5.3 Electronic indicators must not indicate any load greater than 105% (or 9 e for electronic computing scales—preferred for all devices) of the certified capacity.

5.4 The weighing capacity of a weighing device shall not be decreased from the original certified capacity subsequent to the initial inspection, except as requested by the trader.

6.0 Revisions

6.1 The purpose of this revision is to:

  1. Modify section 3.1 of the French version to make it equivalent to the English version.
  2. Make minor editorial and formatting changes.

6.2 The purpose of revision 4 was to:

  1. Remove the 1 000 d requirement from heavy capacity scales to promote the use of larger graduations on these scales without incurring a penalty when it comes to the amount of test standards required.
  2. Remove reference to subsection 172(2) of the Weights and Measures Regulations from NAWD requirements, as it does not apply.
  3. Remove Canadian units of measure and replace with 2:1 conversion factor.
  4. Reword various sections for consistency and OIML harmonization.
  5. Harmonize load requirements for AWDs with those for NAWDs.

6.3 The purpose of revision 3 was to:

  1. Make the requirements applicable to initial and subsequent inspections.
  2. Clarify and expand the ability of the specialist to grant exemptions.
  3. Make minor editorial and formatting changes.
  4. Remove the note from section 3.2 (previously section 2.2 in bulletin M-05 (rev.2)).

6.4 The purpose of revision 2 was to:

  1. Replace the term "recommended" with "minimum" in section 4.0 (formerly section 3.0) to maintain consistency with the requirements for strain testing outlined in the field inspection manuals.

6.5 The purpose of revision 1 was to:

  1. Update the bulletin to take into account the Specifications Relating to Non-automatic Weighing Devices (1998).
  2. Indicate that the specified amount of standards is required for initial inspections year round.
  3. Increase the amount of standards required for the inspection of class IIII vehicle scales used exclusively for weighing gravel, land fill or other raw materials for road construction.
  4. Set a minimum amount of standards, namely 1 000 e, for the inspection of railroad track or combination railroad track / vehicle scales.
  5. Direct readers to the Field Inspection Manual—Non-Automatic Weighing Devices for the performance of substitution and strain tests.
  6. Make minor changes to the text.
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