Air Cooler and ACC Cleaning in Shandong: Judging the Fin Side and the Tube Side Separately

Abstract: Air-cooled equipment has to be judged on two sides before it is cleaned. The fin side carries dust, catkin and salt spray that reduce air flow; the tube side may carry hardness scale from circulating water that reduces heat transfer. The two deposits need different methods, and one method applied to both usually fails on one side and flattens fins on the other. This article follows the sequence used on the two common Shandong installations, refinery air coolers and power-plant air-cooled condensers: where to sample, how far the jetting pressure can go on fins, which material limits apply inside the tubes, and the three things checked at acceptance. Deposit typing and acceptance follow GB/T 25146-2010, jetting safety follows GB/T 26148-2025, and unit-specific figures are marked as pending confirmation.

1. Two kinds of air-cooled plant, identified before anything is opened

A refinery air cooler mounts finned tube bundles on a frame and forces air across them with axial fans. The tube side carries process medium or cooling water; the fin side carries whatever the air brings. Both cleaning drivers are common: dust between the fins cuts air flow, and circulating-water scale inside the tubes cuts the temperature approach.

A power-plant air-cooled condenser is a different object: large bundles, dense fins and turbine exhaust steam inside, condensed by very large fans. It cannot be cleaned online the way a water-cooled unit is cleaned, and the work has to fit the unit outage ([TO BE CONFIRMED: nameplate data and pre-cleaning baseline]).

Identifying the equipment decides the sampling points, the pressure setting and the chemistry, so it is settled from the nameplate, the process drawing and the operating history rather than from appearance or from the last job.

2. Sample three places to decide which side is cleaned first

On the fin side, sample the fin root and the windward face with a white paper lift or a finger wipe, then look for grit, fluff and white crystallised salt. On coastal sites white deposits usually contain chloride from salt spray, which is not the same as inland dust and does not respond to the same rinse volume.

On the tube side, sample after shutdown and depressurisation from the header or the vent connection, and record thickness, colour and adhesion at each point ([TO BE CONFIRMED: deposit thickness and appearance by point]). The laboratory should split the sample into carbonate (as calcium carbonate), iron oxide and acid-insoluble matter.

Typing follows GB/T 25146-2010: carbonate at 60% or more as calcium carbonate may be judged carbonate scale, iron oxide at 80% or more as rust scale. The ratio decides the route; experience does not. Sampling maps and analysis reports are filed with the acceptance package.

3. On the fin side, the pressure limit matters more than the chemical

A fin is a thin aluminium leaf; once a jet folds it over the area is lost for good, and nothing on site bends it back. Use a fan nozzle, move along the fin length, keep distance from the surface and step the pressure down according to fin stiffness and how hard the deposit has baked on. Never strike the bundle square-on. Fix pressure and distance on a trial patch first ([TO BE CONFIRMED: trial pressure, nozzle distance and travel speed]) and only then scale up.

After washing a dry air cooler, blow or air-dry the bundle: water trapped at the fin root accelerates corrosion. A wet air cooler with spray humidification also carries scale and biological slime on the fin side, so the slime is loosened with a biocide first and the wash is run wet; the chemical has to be safe for aluminium fins and is not the tube-side acid bath.

Jetting safety follows GB/T 26148-2025, the safety specification for high-pressure water jetting: relieve pressure before breaking a connection, restrain hose couplings, isolate the work area, and never point the lance at a person. On an air-cooled condenser the access is at height, so edge protection and fan lock-off with tags are preconditions, not details arranged during the job.

4. Inside the tubes, water hardness decides the bath

Make-up water differs widely between plants, from surface water and well water to reclaimed water, and cycles of concentration differ as well, so a dosing ratio copied from another site either fails to dissolve the scale or over-etches the metal. A bench test comes first, its record is filed, and this article quotes no dosing ratio or concentration.

Material limits fail faster than deposit typing. Carbon steel bundles may be warmed to speed the reaction. Stainless bundles hold the bath at 25 mg/L chloride or less, and coastal plants test the mixing water separately because the make-up water is already high in chloride. Where copper tubes or copper alloy parts are present, the components that attack copper are excluded at the bench test instead of being patched up with an inhibitor mid-run.

Circulation is closed-loop with three readings taken on a schedule: acidity, total iron and turbidity. Falling acidity means chemical is still being consumed; a stable iron reading means the soluble deposit has largely reacted. The flow direction is switched once so headers and dead corners see fresh solution. Temperature, duration and sampling interval follow the site plan ([TO BE CONFIRMED]) and are written into the monitoring sheet, because "normal" on its own proves nothing at acceptance.

5. The outage window and the three acceptance checks

Air-cooled condensers follow the unit outage and refinery coolers follow the process unit shutdown; in Shandong most of that work falls in the spring and autumn rounds. The window is short, so sampling, bench tests, the temporary loop and the crew are arranged in advance and only execution and acceptance are left on site.

Acceptance looks at three things. First the fins: visual check for flattened or deformed fins and residual dust, with the area and extent of any flattened zone recorded. Second the operating figures: fan current and outlet temperature at the same load, back pressure or vacuum on a power unit, compared line by line with the pre-cleaning baseline, and no improvement figure is stated when no baseline exists. Third the documents: analysis report, trial-patch record, dosing and monitoring sheets, waste disposal record and acceptance sheet filed as one package.

FAQ

Can fins that have been bent by water jetting be straightened again

No. A fin is a thin aluminium leaf, and once it folds over the heat-transfer area is lost; no field method restores the original angle. That is why pressure and nozzle distance are fixed on a trial patch of about 1 square metre before the full run, and why the pressure is dropped one more step where salt-spray pitting has thinned the fin roots.

Is cleaning the fin side enough for an air cooler

Not always; both sides have to be judged. The fin side carries dust, catkin and salt spray that cut air flow, while the tube side may carry hard carbonate scale that cuts heat transfer. Cleaning only the fins leaves the tube-side scale in place, so the outlet temperature does not return to the pre-cleaning baseline and the acceptance figures do not line up.

Why is the chloride limit repeated for stainless steel tubes on coastal sites

Because chloride in the cleaning solution causes pitting and chloride stress corrosion cracking that cannot be seen afterwards. The tube-side bath is held at 25 mg/L chloride or less, and on coastal sites the make-up water itself is often high in chloride, so the mixing water is tested separately instead of being drawn from the plant service line.

How does cleaning a wet air cooler differ from a dry one

The difference is whether one side or two need work. A dry air cooler mostly carries dust on the fins, and drying after washing is enough. A wet air cooler with spray humidification also builds scale and biological slime on the fin side, so 2 deposit types are handled together and a biocide loosening stage comes first, otherwise the spray water blocks the bundle faster.

Why must an air-cooled condenser be cleaned inside a unit outage window

Because the tubes carry turbine exhaust steam, and there is no way to isolate and open them while the unit runs. The window sits inside the spring or autumn planned outage, so sampling, bench tests and the temporary loop are finished before shutdown and only the work and the acceptance remain on site.

Related reading

• Air cooler fin bundle high-pressure water jetting
• Fouling diagnosis for heat exchangers
• Power plant condenser chemical cleaning
• All cleaning articles

Deposit typing and acceptance follow GB/T 25146-2010, Acceptance specification for industrial equipment chemical cleaning quality; jetting safety follows GB/T 26148-2025, Safety specification for high-pressure water jetting.

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