Net-Weight Drum and IBC Fillers for Trade Use: Which Certificate, Class and Verification to Write Into the Contract

Does your use trigger mandatory type approval and official verification?

Start with the destination, not the machine. In the US, a device used for commercial purposes must comply with the law of the state where it is used, and all 50 states have adopted NIST Handbook 44⁹.

Handbook 44 §2.24 applies to automatic gravimetric filling machines that weigh discrete loads of loose materials and determine package and production lot compliance with net content representations¹⁰. If your drum or IBC filler settles a quantity for sale, purchase, exchange or custody transfer, you are buying into that regulated regime.

And the machine must be inspected and approved by an authorized body of the state before commercial use⁹¹³. Read the scope of §2.24 carefully before you assume it covers you.

The code lists its exceptions — belt-conveyor scale systems, railway track scales, monorail scales, automatic bulk-weighing systems and devices that measure quantity on a time basis¹⁰. A gravimetric filler that produces a predetermined mass per fill is not on that list.

But the applicability turns on what the machine does with the weight, so confirm the function in writing rather than inferring it from the machine category.

Which certificate goes into the contract: NTEP or OIML R61?

For a US destination, write an active NTEP Certificate of Conformance into the contract as the compliance document. The US sources describe only that route: an active NTEP CoC is the key proof of Handbook 44 compliance for a commercial device⁹.

And the certificate is issued by the National Council on Weights and Measures after a device has been evaluated¹³. Treat an OIML R61 certificate as supplementary evidence, not as a substitute.

Nothing in this source set states that a US jurisdiction accepts an OIML certificate in place of NTEP. So a contract that relies on one is relying on an assumption the supplier cannot back with these documents.

If a supplier offers an R61 certificate as the compliance proof for a US installation, ask which state authority has accepted it and on what basis. The answer belongs in the contract file before the deposit is paid.

Why a quoted accuracy class needs its framework named

Suppliers quote accuracy in percentages and class labels, and the two frameworks behind those labels are not interchangeable. OIML R61-1 defines accuracy class X(x) and a reference value Ref(x), with the maximum permissible deviation of each fill equal to the tabulated limit multiplied by the class factor x².

The same recommendation says the class is specified for the intended usage — product, installation, environment, fill value and operating rate . And that the use of accuracy classes for certain applications may be determined by national prescription².

Handbook 44 works on a different structure. Section 2.20 divides weighing devices into classes I, II, III, III L and IIII, designated by the manufacturer according to Table 3 parameters¹¹.

No source in this set maps an R61 class onto a Handbook 44 class, and the two rest on different error bases. When a quotation names a class, ask which document it comes from and who prescribed it for your application.

A class label without that attribution tells you nothing you can put in a contract.

Who performs initial verification, and when

Initial verification is the first official inspection of a newly installed commercial device by a regulatory official¹⁶. In the US that official belongs to an authorized body of the state where the device is used, not to the manufacturer⁹.

Plan the installation schedule around that inspection: the machine is not cleared for commercial use until it has been inspected and approved. Write the responsibility split into the contract.

The supplier's obligation ends at delivering a device covered by a valid certificate and supporting the state inspection; the inspection itself is the state's act. The sources in this set do not state who performs subsequent verification or what interval applies.

So obtain the re-verification requirement from the destination weights-and-measures office and record it as a buyer obligation with its source.

Certificate evidence to demand before the order is accepted

An NTEP certificate covers a device type that may vary in measurement range, size, performance and operating characteristics¹³. So a certificate for the model family is not automatically a certificate for the unit you are buying.

Make each item below a condition of order, not a document promised at shipment.

• ✓Certificate number and issuing body, with the certificate confirmed as active at the time of order
• ✓Exact model and measurement range on the certificate matched to the model and fill range in your purchase order
• ✓Written statement of which accuracy class applies and which document prescribes it for your application
• ✓Confirmation that the supplier will support the state's initial verification inspection after installation
• ✓Named contact at the supplier responsible for certificate validity through delivery

Check the machine's declared scope against the certificate

Confirm the instrument is genuinely gravimetric — it produces a predetermined mass per fill by automatic weighing — because that is the family both frameworks describe²¹⁰. Then check the declared fill range and resolution against the certified type, since the certificate's coverage is bounded by the range and characteristics it lists¹³.

Two scope conditions in R61-1 change what the supplier must declare. Fills of 25 kg or less may also need to comply with OIML R87 on prepackages.

And an instrument that can be operated in non-automatic mode in normal use may also need to comply with OIML R76². Drum and IBC fills sit well above that threshold, but a machine with a manual top-up or calibration mode can still pull in the second condition.

Ask the supplier to state in writing whether either applies to the model offered.

Acceptance tests and the cost of certification

The sources do not specify what a verification certificate, MPE test report, traceability record or factory and site acceptance test should contain for a filling instrument.

That leaves the acceptance deliverables to you: define the test loads, the record format and the sign-off in the purchase order, and tie final payment to the state's approval rather than to shipment.

Certification cost, who bears it, its effect on lead time, and whether approval runs per model or per unit are likewise not established here. Ask the supplier and the issuing body directly, and get the answers before you compare quotes.

A price that excludes certification is not comparable with one that includes it.

Where the sources disagree or stay silent

The two frameworks describe accuracy on different bases, and one secondary summary of the R61 tables is the only source here that puts numbers on the class limits. Keep both sides visible before you write a tolerance into the contract.

What to confirm before you order

• Ask the supplier for model-specific evidence and record the condition that would change your buying decision.
• Request certificate numbers, issuing bodies, scope and validity for the exact model and destination market.
• Ask the supplier for model-specific evidence and record the condition that would change your buying decision.
• Request certificate numbers, issuing bodies, scope and validity for the exact model and destination market.
• Ask the supplier for model-specific evidence and record the condition that would change your buying decision.
• Ask the supplier for model-specific evidence and record the condition that would change your buying decision.
• Request certificate numbers, issuing bodies, scope and validity for the exact model and destination market.
• Ask the supplier for model-specific evidence and record the condition that would change your buying decision.