Heat Exchanger Cleaning by Ultrasonic Immersion

The problem

A fouled exchanger costs you every hour it runs

Scale, oil sludge, biofilm and process deposits all insulate the heat transfer surface. The exchanger loses duty, the pressure drop climbs, and the plant makes up the difference with more fuel, more pumping or a lower throughput.

Most cleaning methods reach only part of the surface. A lance clears a straight tube bore but not the shell side. A pressure washer cleans the face of a radiator and bends the fins it reaches. Ultrasonic immersion cleans every wetted surface at once, because the cavitation happens wherever the liquid is.

Heat exchanger tube ends at the flange face bridged with scale and oil sludge before cleaning — Tube ends before the cycle: scale and oil sludge bridging the bores.

The same heat exchanger tube ends open and clean after ultrasonic immersion — The same bores after ultrasonic immersion, without rodding. From the radiator and heat exchanger case study.

Methods

Heat exchanger cleaning methods compared

Each method has its place. The right one depends on whether the unit can come out of service, what the deposit is, and what the exchanger is made of.

Method	What it reaches	Watch for
Hydro-jetting	Straight tube bores, open shell faces	Misses U-bends, fin roots and plate channels. Can erode thin or brittle tube walls.
Rodding and brushing	Straight tube bores	Scores tube walls. Not usable on finned, U-tube or brittle exchangers.
Chemical circulation (CIP)	The side the chemistry is pumped through	Works in place, but only where the flow goes. Dead legs and hard deposits stay.
Bundle blasting	Outside of the tubes on the shell side	Abrasive contact with the tube surface. Not for coated, soft or brittle tubes.
Ultrasonic immersion	Every wetted surface: tube side, shell side, fins, plates and passages	The unit has to come out and fit the tank. The chemistry must suit the material.

Ultrasonics is often used alongside the other methods, not instead of them. A bundle can be soaked and cavitated to loosen hard scale, then flushed, so the jetting pass is shorter and gentler.

What we clean

Exchangers we clean by immersion

Shell-and-tube bundles. Pulled bundles are lowered into a tank sized to them, and the tube side, shell side and tube sheet clean together. Bundles to 12 metres go in the UltraMax HX tanks.
Plate heat exchanger plates. Plates from an opened plate-and-frame pack are racked on edge in a basket so every channel face sees the liquid. Gaskets are removed or protected first.
Oil coolers, radiators and charge-air coolers. Fin-side dirt and tube-side oil sludge come out in one immersion. Air-to-oil and copper-tube cores are covered in the case study.
Cooler cores and finned coils. Engine, hydraulic and compressor coolers from mining, marine and transport fleets. See a fouled cooler core coming out of an UltraTecno tank.
Non-metallic exchangers. Graphite blocks and tubes, silicon carbide tube bundles and PTFE coils, covered below.

Large parts go in the EvoSonic and UltraTecno ACM tanks, which have platform lifts so a heavy core is lowered rather than dropped. For an existing pit or vessel, rod resonators retrofit the ultrasonics into it.

Non-metallic heat exchangers

Cleaning graphite, silicon carbide and PTFE heat exchangers

Where the process fluid would eat a metal exchanger, plants use impervious graphite, silicon carbide or fluoropolymer. Hydrochloric, sulphuric, phosphoric and hydrofluoric acid duties, pickling lines, vinyl chloride and pharmaceutical processes all rely on them. The best-known makers are SGL Carbon (DIABON graphite), Mersen (Graphilor graphite blocks and shell-and-tube units, and silicon carbide shell-and-tube exchangers) and Saint-Gobain (silicon carbide). They resist corrosion, but they foul like any other exchanger, and they are far less forgiving to clean.

Material	How it is built	What to watch when cleaning
Impervious graphite	Graphite blocks or tubes, impregnated with phenolic resin, PTFE or carbon to seal the pores. Block units use PTFE gaskets between blocks.	Brittle: no steel rods, no impact, support blocks on soft cradles. Phenolic grades resist most acids and solvents but not strong alkalis or oxidisers, so a caustic degreaser that suits steel can damage them. Stay inside the maker's temperature limit for the grade, commonly 220 °C for phenolic.
Silicon carbide	Sintered SiC tubes in PFA-lined tube sheets, inside a steel, lined or glass shell.	Very hard and almost universally corrosion resistant, so the chemistry can be chosen for the deposit. Tubes are still ceramic: handle the bundle without point loads and check the seals and linings separately.
PTFE and fluoropolymer	Bundles or immersion coils of thin PTFE or PFA tube.	Smooth and slow to foul, but soft. No abrasives or brushes. Thin tubes need low handling loads and a gentle rinse.

Ultrasonic immersion suits these materials because no tool touches the surface. A graphite block, silicon carbide bundle or PTFE coil sits on a support in the tank, and the cavitation works inside the bores and passages where a jet or a brush would have to be forced in.

How we approach a non-metallic exchanger. We read the maker's data first: material grade, impregnation, temperature limit and approved cleaning agents. We then trial the chemistry and the ultrasonic power on an offcut, a spare block or a single tube before the whole unit goes in. If the maker does not allow a step, we do not do it.

Material limits above are taken from published maker data. Always confirm against the data sheet for your unit and grade.

The process

How an ultrasonic heat exchanger clean runs

Identify the material and the deposit. Read the nameplate or flange stamp, and take a sample of the fouling if it is not obvious.
Release the oil. Heavy oil build-up in oil coolers and oil-fouled cores is broken down first with SolvoKleen, used neat.
Remove dirt, rust and scale. Red dirt, rust and scale come out of cooler cores in CoreKleen HX at pH 6, which is safe on aluminium and zinc. Oxide and heat scale on steel take an acid descaler such as Descale. For non-metallic exchangers the chemistry is matched to the material first.
Flush and neutralise. Rinse the unit through and bring it back to neutral before it goes back in service.
Verify. Flow or pressure test against the baseline, and inspect tube ends, plates or blocks.

Cycle times depend on the deposit. A cooler core in CoreKleen HX typically runs 60 to 90 minutes at 50 to 60 °C. Hard scale on a large bundle takes longer across the stages.

Questions

Heat exchanger cleaning: common questions

Can a heat exchanger be cleaned without taking it apart?

Plate packs have to be opened so the plates can be racked. Shell-and-tube bundles, coolers and radiators are usually cleaned whole once they are out of service: the unit goes into a tank sized to it and the liquid reaches the tube side and shell side together.

Can ultrasonic cleaning damage a heat exchanger?

Not when the frequency, power, temperature and chemistry suit the material. Most damage in exchanger cleaning comes from rods, brushes, abrasive blasting or the wrong acid. No tool rubs or strikes the surface. Thin, coated or brittle units are trialled on a sample first.

Can graphite heat exchangers be cleaned ultrasonically?

Yes, with care. Graphite blocks and tubes are brittle, so immersion avoids the rods and impact that crack them. The chemistry must suit the impregnation: phenolic-impregnated graphite resists most acids and solvents but not strong alkalis or oxidisers. Check the maker's data for your grade and trial a spare block first.

What chemical is used to clean a heat exchanger?

It depends on the deposit and the metal. Oil sludge needs a solvent or degreaser, rust and red dirt a mild acid cleaner such as CoreKleen HX at pH 6, and heavy oxide or heat scale on steel an acid descaler. Aluminium, copper and non-metallic exchangers each limit what can be used.

How big a heat exchanger can be cleaned by immersion?

Cooler cores and plates fit the EvoSonic and UltraTecno tanks. Shell-and-tube bundles to 12 metres long go in the UltraMax HX range, and an existing pit or vessel can be fitted with rod resonators.