Sourcing borosilicate sight glass discs from China

Duty and classification for sight glass discs

Heading 7020 covers other articles of glass. For bare borosilicate sight glass discs, consider 7020 00 30 00 when the material meets the tariff's low-expansion description. The table shows different disc finishes sharing that commodity line, rather than separate tariff categories. Confirm the expansion coefficient from the material certificate.

Read from the UK Trade Tariff on 1 October 2026, every supplied heading 7020 line carries 0% duty for goods from China. No anti-dumping or countervailing duty or suspension is recorded. The relevant line attaches import and export controls on cat and dog fur; the importer should confirm the requirement with their customs broker.

Confirm the commodity code using the material evidence and the condition in which the goods arrive, especially where a housing is included. For related products within the wider heading, see glass sight gauge tubes.

Disc dimensions, sealing faces and service conditions

Specify the glass grade, expansion coefficient, diameter, thickness, tolerances, flatness, face finish and edge bevel on a drawing. State whether the disc is annealed or toughened. Agree acceptable bubbles, inclusions and scratches, particularly within the viewing area and gasket contact area.

Give the equipment manufacturer the intended fluid, operating pressure, temperature changes, cleaning conditions, housing and gasket details. Official pressure equipment guidance sets requirements before equipment or assemblies can be placed on the Great Britain market. Ask the equipment manufacturer to establish how those requirements apply to the proposed disc and housing before agreeing the order.

Agree material certificates and sample thermal shock testing that matches the service conditions. Where the glass holds food or drink, obtain food-contact evidence. Settle the test brief through testing and certification, including which disc finish and batch the evidence covers.

Worked duty example

Illustrative example, not a quote: Illustrative order: 300 borosilicate sight glass discs under 7020 00 30 00, invoiced at £1,200 free on board, with £100 of freight and insurance to the UK. The customs value is £1,300. Duty at 0% is £0. Import VAT at 20% is charged on the customs value plus duty, £1,300, so it is £260. With no duty, the only import tax is the VAT, which a VAT-registered importer can usually reclaim. The import duty and VAT guide explains each step.

Inspection checklist

Material: match the batch certificate to the order and check the expansion coefficient against the agreed grade.

Dimensions: measure diameter and thickness, check flatness and bevels, and trial the sample in the intended housing with the specified gasket.

Surface and stress: inspect sealing faces for scratches, chips and cracks; check residual stress with a polariscope and record sample thermal shock results.

Packing: check individual separation, edge protection and carton condition, then record arrival damage against each batch. Agree the checks in the inspection brief.

What goes wrong

A replacement disc can match the diameter but have the wrong thickness, bevel or sealing-face finish. Uneven gasket contact, edge chips and incorrect clamping can cause leakage or cracking. Approve the drawing and a trial fit rather than ordering from diameter alone.

Material substitution and poor annealing can leave a disc vulnerable to thermal cycling. A material certificate does not establish suitability for every housing or operating condition. Keep damaged discs out of installation and investigate whether the cause is manufacture, packing or fitting before accepting replacements.

Cambridge China Bridge sources these products for UK businesses, checking the factory and the documents before shipment. See factory verification. For own-brand ranges, see sourcing for brands.