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Work Instructions for the Verification of

Automatic Checkweighing Instruments

under the Measuring Instruments Directive

Index
Introduction / 1
Legislation / 2
Staff / 3
Equipment / 4
Verification procedure / 5

1 Introduction

This document is intended to be read in conjunction with the MID quality management system. It forms the technical procedures in relation to the verification of automatic checkweighers under the Measuring Instruments Directive. It is a guide for all officers involved in the verification of automatic checkweighers. Its aim is to establish best practice and provide a basis for our confidence that such equipment is verified to a consistent level of quality across the area of the notified body. It cannot cover every situation that will arise but provides a framework within which all situations can be handled.

It should be born in mind that an Automatic Checkweighing Instrument may often be capable of functioning as an Automatic Catchweighing Instrument as well and that therefore the Instrument may need to be verified in accordance with the procedure for such instruments as well.

2 Legislation

The legislation and guidance relevant to this document are as follows:

·  The Measuring Instruments Directive 2004 2004/22/EEC

·  The Measuring Instruments (Non-Prescribed Equipment) Regulations 2006 SI 2006:1270

·  The Measuring Instruments (Automatic Catchweighing Equipment) Regulations 2006 SI 2006:1257

·  OIML Recommendation R51-1 & R51-2 Automatic Catchweighers

3 Staff

·  All staff involved in the testing of automatic catchweighers must have regard to their health and safety code of practice and risk assessments for the testing of weighing equipment.

·  Staff will be monitored to ensure compliance with the above requirement

4 Equipment

1.  Before use all equipment to be used during the verification should be checked for damage and its calibration status. The authorised verification officer will make a decision as to whether any damage is sufficient to affect the accuracy of the equipment. If the damage is considered significant alternative equipment must be used and the damaged equipment removed from use until it has been repaired.

2.  Before commencing any tests, the verification officer must ensure they have a suitable control instrument to determine the true mass of all test loads. Accuracy should be as determined by the criteria set out on the test sheet depending on the testing history of the control instrument.

3.  Test loads for the verification shall, where feasible, be of the same type of material that the measuring instrument is intended to weigh. Where it is not possible to make test loads up using appropriate material calibrated weights should be used.

4.  The following test load values will need to be prepared prior to or during testing:

1.  Of mass below Minimum load of the instrument under test,

2.  Of mass as near to the Minimum load as practical,

3.  Of mass as near to the first error transition point as practical, or other suitable intermediate load as appropriate,

4.  Of mass as near to the second error transition point as practical, or other suitable intermediate load as appropriate,

5.  Of mass as near to the Maximum load as practical,

6.  Of mass in excess of Maximum load by an amount equivalent to 10 divisions.

7.  Of mass as near to 1/3 of the Maximum load as practical for the eccentric test

  1. All staff attending on the verification activities will need suitable personal protective equipment in accordance with the risk assessments identified above.
  1. All test equipment being transported by the authorised verifying officer to and from the location of the verification shall be loaded onto the vehicle in such a way that the risk of damage to it is minimised.
  1. On return to the office all equipment shall be returned to its storage location, unless any damage has been noted or occurred during use. If this is the case the damage shall be reported and the equipment quarantined until it has been repaired and recalibrated.
5 Verification Procedures

1.  When responding to a request for the verification of an automatic catchweighing instrument the verifying officer shall arrange with the person submitting the equipment to provide all or any of the following:-

·  Copies of the type examination certificate (TEC) in English.

·  A sufficient quantity of articles and suitable material for the test loads that shall be of the same type of material that the instrument is intended to weigh.

·  Additional weighing equipment, a control instrument, to determine the true mass of the loads.

·  Sufficient personnel who may be required to assist in the performance of the tests.

2.  On arrival at the site, authorised verification officers shall introduce themselves to the site manager, sign in and comply with any health and safety requirements of the premises.

3.  Carry out a visual inspection to ascertain that the instrument and any ancillary equipment submitted for verification complies with the type examination certificate as declared in the declaration of conformity.

4.  Check that the instrument is correctly marked and record the relevant details on the verification test sheet.

5.  The officer shall then prepare and mark suitable test loads to complete the series of tests (See 4.4).

Zero setting device

The operation of the zero setting device of the instrument should be tested as specified in the type examination certificate.

Standard operational tests

1.  Tests shall be carried out under normal conditions of use using material of a type that the instrument is intended to weigh.

2.  Additional tests should also be undertaken dependant on any descriptive markings on the instrument as to any weight limits or weight range, normal or alternate operating speeds and tare facilities.

3.  Where Instruments are designed to weigh statically these may be tested in a non-automatic mode.

Alternative operating speed

Where the instrument is constructed to operate at different belt speeds the accuracy of operation should be tested. With the instrument in dynamic mode and the zero-setting function in operation, tests should be performed using at least two different loads; one near to minimum and one near to maximum; at a speed corresponding to the maximum speed of operation and also at a mid speed.

If the instrument is specified to operate with different maximum capacities for alternative speeds then the correct maximum load should used to test at each speed.

Tilt test

Instruments that are not permanently installed or are not fitted with a level indicator should be tested at loads as near to minimum capacity and maximum capacity at an incline of 5%.

Eccentric load tests

Instruments that weigh in motion

Under normal operating conditions with zero-setting in operation a test load with a mass of 1/3 of the maximum capacity (plus additive tare if applicable) should be placed on the Transporting system halfway between the centre and the back of the transporting system and then repeated with the same load the on the opposite side of the transporting system. The load should be repeated through a minimum of 10 cycles.

Instruments that weigh in a static mode

A test load with a mass of 1/3 of the maximum capacity (or where the instrument has n points of contact n<4 the fraction 1/(n-1) of the max) should be loaded in each of the four quadrants in the stationary load conveyance system or points of support.

Range

The specified range of the instrument should be tested using the loads specified in the standard operational tests and additional loads just below minimum and just above maximum.

Determination of errors

For each different pre-determined test load (See 4.4) used to test the instrument a minimum of 20 consecutive cycles should be performed and the indication of the weight as shown by either the instrument indicator, the printer or labeller should be recorded on the verification test sheet.

The errors, being the standard deviation of the complete set of test runs for any given test load at any given test speed, should not exceed the appropriate maximum permissible error.

Pass or fail

·  If, pursuant to accuracy testing, the automatic checkweighing instrument is found to be within the prescribed limits of error for its accuracy class and conforms to the legislation in all other respects the instrument shall be passed as fit for use for trade.

·  If the instrument has been passed the verification marks shall be applied in accordance with the legislation and as detailed in the type examination certificate.

·  A certificate of conformity or non-conformity, as appropriate, shall be issued for the automatic checkweighing instrument and its reference number recorded on the verification record sheet.

·  Where a certificate of non-conformity is issued a notice of rights of appeal shall also be served.

Automatic Checkweighing Instruments | Work Instructions | Version 1 | 3/6