Guide

How do legal-metrology checks affect a weigh filling line?

A weigh filler helps control the dose, but the buyer remains responsible for the finished-pack measurement system, records and any legal-for-trade requirements that apply.

Weight-control boundary

Distinguish process control from legal compliance.

This guide gives general planning information only. Final legal-metrology and packaged-goods compliance should be confirmed against the actual product, pack, market and measurement system.

Is a weigh filler automatically a legal-for-trade instrument?

A weigh filler is not automatically suitable as a legal-for-trade measurement instrument. The buyer must confirm the applicable measurement requirements, reference checks, finished-pack controls and any approved weighing equipment needed for the product and sales route.

The UK Government guidance on packaged goods explains the legal framework for products sold in fixed quantities, including the average and minimum systems. The finished pack, not only the dosing machine, is the important commercial evidence.

Authoritative reference: GOV.UK packaged goods guidance.

Where does a checkweigher fit?

A finished-pack checkweigher can provide a separate confirmation point after filling, sealing or closure. It can help identify underweight packs, overfill, drift and reject events, but it must be specified, calibrated and used within the buyer’s quality and legal-metrology process.

For some projects, the important interface is not simply whether a checkweigher exists, but how the data, reject confirmation and any feedback to the filler are controlled.

Planning questions for legal-metrology discussions.

Topic	Question	Evidence to prepare
Sales route	Is the product sold by fixed weight, variable weight or internal transfer?	Label quantity and market route.
Measurement system	Will the process use average quantity, minimum quantity or another control method?	Buyer’s quality procedure and Trading Standards advice where relevant.
Reference checks	What scale or checkweigher will verify finished-pack results?	Instrument details, calibration records and sample plan.
Reject handling	How will suspect packs be removed, recorded and reconciled?	Reject procedure and responsibility.

Does the filler replace quality sampling?

No. The filler is part of process control. Finished-pack checks and records should still confirm that accepted packs meet the buyer’s required measurement system.

What data should be kept?

Keep target weight, reference checks, sample results, rejects, adjustments, batch identity and any checkweigher reports needed by the quality system.

Who confirms legal requirements?

The buyer should confirm requirements with its quality team, competent metrology advice or Trading Standards where appropriate. Lancing can help define machine and checkweigher interfaces.

Read packaged-goods planning guidance Plan checkweigher integration Discuss measurement controls

Send the product and pack details for a practical weigh filling route.

Include the product, target weight, pack format, target output, sample availability and any existing line equipment. Lancing can then advise which weighing route is worth testing.

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