Ultrasonic cleaning in heavy industry: energy, oil and gas, mining, rail

Heavy industry cleans in two situations: during a planned outage, when everything that can be removed is removed and must be back in service by a date, and in the maintenance workshop, where the parts that failed are overhauled. Both want a tank that takes large, heavy, badly fouled components and cleans them completely in one cycle, because there is no time for a second.

What comes in

• Heat exchanger bundles, plates and coolers: scale, sludge, oil and biological fouling from cooling water and process fluids. Ultrasonic cleaning reaches between plates and tubes where jetting cannot; see the power plant article for the sequence.
• Valves, actuators and pump parts: heavy oil, carbon, scale and product residue in the bores and seats. Cleaned before inspection and re-machining.
• Compressor and turbine components: blades, vanes, rotors, bearings and housings with oil coke and deposits; cleaned before non-destructive testing, which sees nothing through a layer of soil.
• Hydraulic blocks, cylinders and manifolds from mobile and fixed plant: contaminated oil and particles in cross-drillings, to a cleanliness specification.
• Filters and strainers: reusable metal filter elements, cleaned instead of replaced; see porous materials.
• Rail and rolling stock components: traction motor parts, gearboxes, brake components and bogie parts with grease, brake dust and road dirt.
• Mining equipment parts: everything above, plus abrasive dust ground into the grease.

What the tank has to be

Size and load. The AL series carries baskets of 200 to 1000 kg in tanks of 300 to 2000 litres on a pneumatic lift; the AU series goes to 8000 litres and 2000 kg per basket. Tanks beyond the tables are built to drawing; see custom units. Useful basket dimensions, not tank volume, decide the model; a heat exchanger bundle of 1500 mm sets the AL-1000 or an AU-2000 regardless of its weight.

Power. 28 kHz for cast, forged and heavily fouled parts. Ultrasonic power from 3.6 kW on the AL-300 to 20 kW on the AL-2000 and 70 kW on the AU-8000; heating from 9 to 64 kW, because a cold two-tonne basket takes heat out of a bath fast.

Chemistry. Alkaline degreasers for oil and grease; carbon cleaners for coke; acidic descalers in a 316 tank or an insert for scale; see rust and scale. A soak stage at 85 to 95 °C in the same tank before the ultrasound halves the time on heavy coke.

Filtration and skimming. A bath in an overhaul shop carries kilos of sludge and litres of oil per week. Modular filtration and an oil skimmer on the AL and AU series, a floor drain used monthly, and a bath-change schedule; see filtration and bath life.

Agitation. The lift's vertical oscillation pumps liquid through bores and between plates. On heavy, dense loads it is the difference between one cycle and three.

Rinse, protect, dry. Bare steel out of a hot alkaline bath rusts in the hour. An inhibitor dip and a hot-air dry, or immediate re-oiling, are part of the process; see rinsing and drying.

Outage work

For outage cleaning the tank is sized to the largest component on the list, the schedule is built around the cycle time per basket, and the chemistry is chosen once for the mix of soils rather than per part. A spray washer, the SPR series, in front of the ultrasonic tank takes the gross sludge off and keeps the bath alive for the week; see spray washer or ultrasonic bath. Where components cannot be brought to a workshop, immersible transducer boxes in a site tank bring the process to them.

Safety

Large tanks of hot alkali, baskets of a tonne over open liquid, and generators of tens of kilowatts. The AL and AU series run the cycle with the lid closed, move the basket on the lift platform, and carry the fittings that the safety article lists.

The articles below cover individual parts and processes as they are written. The quote article lists what we need to size a tank for an overhaul shop or an outage.