M-05–Standards Required for the Initial and Subsequent Inspection of Weighing Devices

M-05 – Standards Required for the Initial and Subsequent Inspection of Weighing Devices (PDF, 90 KB, 7 pages)

Category: Mass
Document(s): W&M Regulations 172, NAWDS
Issue Date:
Effective Date:
Supersedes: M-05 (rev. 3)

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 (NAWD) and Automatic (AWD) weighing devices.

2.0 Background

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

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 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 Test Standards Required

The following outlines the minimum acceptable amount of test standards and test load suitable for 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 Device (NAWD)

3.1.1 All Devices

Subject to subsections, and 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; or If the device has a repeatability error of:

3.1.1.1 Not greater than 0.3 e, the amount of test standards required may be further reduced to 1/3 Max (33.3%).

3.1.1.2 Not greater than 0.2 e the amount of test standards required may be further reduced to 1/5 Max (20%).

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 procedure for Break Point Determination (Gravimetric Field Inspection Manual, Appendix III).

3.1.2 Large Capacity Device (Except Railroad & Combination Rail/Vehicle Scales)

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

Max > 200 000 kg

Unless test standards to 100% Max are available, 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 below.

3.1.3 Railway or Combination Railway / Vehicle Scales

  • 3.1.3.1 Two certified railway test cars representing at least 30 000 kg or 10% Max whichever is greater (preferred option); or;
  • 3.1.3.2 One certified railway test car plus 10 000 kg of test standards is permissible rather than two test cars, provided that they represent at least 30 000 kg or 10% Max whichever is greater; or
  • 3.1.3.3 An equivalent amount of test standards (30 000 kg or 10% Max whichever is greater) and an appropriate method to move the standards for the test.

Unless test standards to 100% Max are available, 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 below.

3.1.4 Hopper and Tank Scales

3.1.4.1 Up to 1 000 kilograms capacity: test standards for a full capacity (Max) test.

3.1.4.2 Over 1 000 kilograms but less than or equal to 10 000 kilograms capacity: at least 1 000 kilograms of test standards.

3.1.4.3 Over 10 000 kilograms 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 as outlined in section 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 (AWD)

3.2.1 Automatic Discontinuous Totalizing Weighing System (DTWS) – Bulk Weigher

Test standards as required by section of the Non-automatic Weighing Device requirements listed above 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 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 Automatic Weighing Device (AWD), Discontinuous Totalizing Weighing System (DTWS), Standard Test Procedures (STP) for more information.

3.2.2 Automatic Continuous Totalizing Weighing System (CTWS) – Conveyor Belt Scale

Sufficient test standards to test a suitable Non-automatic Weighing Device to be used as a reference scale for the product test. See Automatic Weighing Device (AWD), Continuous Totalizing Weighing System (CTWS), Standard Test Procedures (STP) for more information on the development of a suitable test load.

3.2.3 Automatic Catch Weighing Device (ACWD) – Overhead Rail or Belt scale

Test standards as required by section of the Non-automatic Weighing Device requirements listed above for a similar device.

3.2.4 Automatic In-Motion Railway Weighing Device (IMRW)

Test standards as required by section of the Non Automatic Weighing Device requirements listed above.

3.2.5 Other Automatic Weighing Device or System

Test standards as required by section of the Non-automatic Weighing Device requirements listed above for a similar device.

4.0 Substitution and Strain Testing

When the quantity of test standards available is less than Max (Non-automatic Weighing Device) or Capacity (Automatic Weighing Device), Strain or Substitution tests must be used to extend the range of testing.

Strain Test

Strain tests shall be conducted on large capacity scales when the number 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 Test

Substitution is generally only appropriate when the inspector has adequate control over the weight of the substitute test load (within 0.1e). This effectively restricts its use to tank and hopper scales weighing liquid or fine granular products.
Further details on the minimum number and manner of performing such tests can be found in the Non-automatic Weighing Devices (NAWD), Field Inspection Manual (FIM), STP-13.

Product Test

Product testing is 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 STP 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. Remove the 1 000 d requirement from heavy capacity scales. This is to promote the use of larger graduations on these scales without incurring a penalty when it comes to number of test standards required.
  2. Remove reference to regulation 172(2) from NAWDS 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 Automatic Weighing Devices with those for Non-automatic Weighing Devices.

6.2 The purpose of revision 3 (08/2003) 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. To make minor editorial and formatting changes.
  4. Remove the note from section 3.2. (previously section 2.2 in bulletin M-05-E (rev. 2)).

6.3 The purpose of revision 2 (11/2001) was to:

  1. Replace the term “recommended” with “minimum” in section 3 to maintain consistency with the requirements for strain testing outlined in the Field Inspection Manuals.

6.4 The purpose of revision 1 (05/1998) was to:

  1. Update the bulletin to take into account the Specifications Relating to Non-automatic Weighing Devices 1998 (NAWDS).
  2. Indicate that the specified quantities of standards are required for initial inspections year round.
  3. Increase the quantity 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 quantity of standards, namely 1 000 e, for the inspection of railroad track or combination railroad track / vehicle scales.
  5. Direct readers to the NAWDS FIM for the performance of substitution and strain tests.
  6. Make minor changes to the text.

7.0 Additional Information

For additional information regarding this bulletin, please contact the undersigned.

Luciano Burtini
Senior Program Officer, Gravimetric
Weighing and Measuring Division
Program Development Directorate