Refrigerant Leak Detection — Electronic Detectors, UV Tracer and Bubble Methods in Practice

When to use an electronic heated-diode/infrared detector, UV tracer dye or bubble solution for refrigerant leak search, what sensitivity classes mean under EN 14624 and the F-gas inspection regime, sensor replacement practice (Inficon D-TEK, TIF), and a structured search routine that actually finds the leak.

Three methods, one sequence

Serious leak search is a sequence, not a single tool: electronic detector to localise the area, bubble solution to pinpoint and prove the joint, and UV tracer as the long-term witness for intermittent and assembly-internal leaks. The F-gas regulation's periodic checks (frequency by CO2-equivalent charge) accept direct methods — electronic detection, bubbles, UV — applied systematically; the plant log must record method and result.

Electronic detectors

Heated-diode and infrared cells detect halogenated refrigerants at the grams-per-year level demanded by EN 14624-class instruments; A2L-capable and hydrocarbon-capable versions extend coverage to R32, R1234ze/yf and R290. The sensing cell is a consumable: sensitivity decays with exposure, and the maker's replacement interval (typically annually in service use) is the difference between an inspection and a ritual. The catalogue stocks the replacement sensors — Inficon D-TEK 3 / Stratus sensor (HFC + A2L), D-TEK Select sensor, and TIF tips and elements (ZX-14 tip, ZX-2 sensor, ZX-15 filters). Search technique: plant off or fans quiet, probe moved slowly (2–5 cm/s) under joints since refrigerants fall, confirm every alarm twice from fresh air, and verify the instrument daily against a reference leak if it has one.

Bubble solutions

The pinpoint tool: a film of leak-detection fluid over the suspect joint shows the exact pore as growing foam. Use purpose-made fluid, not washing-up liquid (chlorides + copper = corrosion). Bubbles need positive pressure — on a recovered system, a dry-nitrogen stand at test pressure makes every joint testable; that is also the EN 378 tightness-test setup. Limitations: slow on large plants, useless on sub-gram/year seepers, awkward overhead — exactly the gaps the electronic detector covers.

UV tracer

A small dose of UV-fluorescent dye (UV tracer canister, 4.5 kg) circulates with the oil; any escape path accumulates a glowing witness mark inspected with a UV lamp weeks later. It is the method for intermittent leaks (vibration-opened joints, pressure-dependent seals) and for finding which of fifty flare nuts weeps. Rules: dose per the dye maker's oil-charge table — overdosing thins oil; use dye compatible with POE; log the dye addition in the plant record so later samples are interpreted correctly; and clean old dye off repaired joints, or every future inspection re-finds the ghost.

A search routine that works

1. History first: where was the last repair, what does the oil spot pattern on the floor say, how fast is the charge going (log data)?
2. Electronic sweep of the usual suspects: flare nuts, rotalock gaskets (renew PTFE gaskets), Schrader cores and caps, valve bonnets, braze joints at vibration points, pressure-switch capillaries.
3. Bubble-confirm every electronic hit before wrenching.
4. If nothing found and loss continues: nitrogen stand-test section by section, then dye for the long game.
5. Repair, evacuate, recharge by weight, and record method + result in the F-gas log.

On A2L/A3 refrigerants, detectors must be rated for the gas and the space ventilated during search; hot work only after recovery and nitrogen purge — see the purging guide. Fixed gas detection in machinery rooms (EN 378 occupancy rules) complements, never replaces, the periodic hand search.

Compiled by cBallast for identification and cross-reference. Part numbers, designations and trademarks belong to their respective manufacturers. Confirm ratings and dimensions against the manufacturer's current documentation and the nameplate of the installed equipment before ordering or installation.