TS–011 General sealing requirements for weighing and measuring instruments

Reference documents

• Weights and Measures Act 1987(external link)
• Weights and Measures Regulations 1999(external link)
• Certificate of Approval Register

Policy

Instruments must be sealed in accordance with the requirements specified in the certificate of approval and, where applicable, meet the requirements listed below: 

General sealing requirements (all instruments): 

• All sealing requirements shall be secured with a mark of verification. 
• All seals must be indelibly marked with the personal identifier of the accredited individual, consisting of the letters “AP”, together with that person’s unique number. 
• All seals must be suitable for the equipment they are used on and be designed so that their removal irreparably damages the seal.  
• A seal must be applied to any access point to the calibration function(s) of the instrument such as, calibration switches, housing, cover plates or screws. 
• A seal must be applied to any connection point (unless hardwired) where a component or module, that is, flowmeter, load cell or indicator, may be replaced or adjusted, which may affect the accuracy or metrological characteristics of the equipment.
• A seal must be applied to any interface port such as, RS 232 and / or USB, where it is possible to manipulate data and / or affect the measurement performance / metrological characteristics of the instrument via the interface port. 

Weighing instrument sealing requirements:

• The junction box housing.
• The cable between the indicator and the load cell(s) or junction box should also be secured by sealing to prevent components being changed or tampered with, unless the cables from the load cell or junction box are hard wired into the indicator housing.

Where an event counter is in operation, the post calibration reference number shall be recorded on an approved seal or label attached to the equipment in an easily visible location.

Measuring instrument sealing requirements:

• Any test points for example, air eliminator test valves.
• Any flow meter that can be adjusted by a k-factor shall be sealed to the frame of the instrument or sealed directly to the pipework.
• Any point where measurement results can be changed by altering a parameter.

Sealing methods: 

Acceptable sealing methods include wire with lead or plastic seals, or self-destructible labels. Where an alternative method of sealing is to be used that is not described in the certificate of approval, prior approval from Trading Standards is required.