Sourcing thyratron tubes from China

0% duty on thyratron tubes

Read from the UK Trade Tariff on 2 October 2026, heading 8540 covers thermionic, cold cathode and photocathode valves and tubes, including gas-filled tubes. Every supplied line carries 0% duty for goods from China. The supplied data lists no anti-dumping or countervailing duty, suspensions or attached import controls.

For a complete thyratron, check the other valves and tubes line, 8540 89 00 99; separately imported qualifying tube parts may fall under 8540 99 00 90. The table shows thyratron variants sharing a candidate code, rather than separate tariff subdivisions. Confirm the commodity code from the datasheet and function. See the power triode vacuum tubes guide for wider heading context.

Specify the thyratron and its pulse circuit

Specify the manufacturer's type, approved equivalents, gas fill, envelope construction, base connections and mounting drawing. State anode voltage, peak and average current, pulse duration, repetition rate, trigger waveform, heater supply and cooling conditions. For reservoir-equipped tubes, obtain the reservoir settings and operating instructions. Agree acceptance limits for trigger delay, timing variation, recovery and unintended firing in the intended circuit.

For tubes incorporated into electrical products sold in the UK, obtain hazardous-substance declarations and identify any exemption relied on, as explained in our published valve guide. Some hazardous-substance uses have exemptions; do not assume an exemption covers the ordered tube. Manufacturers of equipment within scope must maintain technical documentation demonstrating compliance with the hazardous-substance regulations. Arrange testing and certification support around the actual application.

Worked duty example

Illustrative example, not a quote: Illustrative small-business batch of replacement thyratron tubes under 8540 89 00 99, invoiced at £20,000 free on board, with £900 of freight and insurance to the UK. The customs value is £20,900. Duty at 0% is £0. Import VAT at 20% is charged on the customs value plus duty, £20,900, so it is £4,180. 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

Identity: compare type markings, manufacturer, batch records and declared new or refurbished condition with the order; reconcile test records with the delivered tubes.

Mechanical condition: inspect glass or ceramic envelopes, seals, terminals and mounting surfaces for cracks, chips, distortion and transport damage; check connections against the drawing.

Pulse performance: have a competent test operator check heater and reservoir behaviour, trigger delay, timing variation, recovery and unintended firing under the agreed circuit conditions.

Packing and documents: check individual supports protect envelopes and terminals, retain operating instructions and material declarations, and photograph damage before unpacking further. Use our quality inspection guide.

What goes wrong

A tube described as an equivalent may fit the socket but need different trigger, heater or reservoir settings. Incorrect settings or unsuitable pulse conditions can produce erratic firing, slow recovery or early failure. A generic valve test does not establish performance in the buyer's pulse circuit.

Relabelled stock, missing operating history and cracked seals can undermine an otherwise matching order. Approve a sample in the intended circuit, agree traceable test records and specify protective packing before ordering the batch.

Cambridge China Bridge sources these products for UK businesses, checking the factory and the documents before shipment. See factory verification. For components and parts, see sourcing for manufacturers.