Cooling system maintenance |
Figure 4. Water jet lance in operation. Front nozzles rotate; rear nozzles push the jet lance through the tube
Figure 6. Examples of different brushes, drills and grinders adaptable to a flexible shaft that can be pushed through condenser tubes by an operator. Images courtesy:
Drechselnundmehr.de;
boostedbuys.com;
norarienshoppe.com
tubes independent of their location is also way easier to achieve than with all-liquid chemical cleaning (Figure 8).
Figure 5. Water gun cleaning, with projectiles suitable for removal of various kinds of scale
Because of the large amount of cleaning solution required, waste disposal might be an issue and, depending on the chemicals added, might be a costly experience. Therefore, chemical cleaning is usually only applied to smaller heat exchangers.
Foam cleaning
Foam cleaning (described also in a previous article in Modern Power Systems, but as applied to steam and gas turbine blades, see MPS July/August 2025, pp 23-30) uses the same principles and chemicals as chemical cleaning. But as the cleaning process is done with foam instead of a liquid solution, the amount of chemicals and the quantities of waste that need treatment and special disposal are way smaller. The foam combines the properties of a gas with those of a liquid. The foam bubbles are 95-98% gas and only 2-5% liquid, which forms the bubble’s skin. The liquid part of the foam, which has a shaving-soap-like texture, is what brings about detachment and dissolution of the scale. Because of the density of the foam, it is able to disperse and carry out detached particles and flakes. Filling of the entire condenser is not complicated, and an even flow through all
Not to forget that the amount of wastewater to be treated and disposed of is much smaller, which also has a favourable impact on EHS compliance.
Foam cleaning case studies The advantages of foam cleaning can clearly be demonstrated by looking at two case studies, a lignite fuelled power plant and a
combined cycle plant: ● Lignite fuelled power plant, Poland The condenser of a 225 MWe lignite fired power plant in Poland suffered from scaling, sedimentation and biofouling. River water in once-through configuration is used as coolant. The 13 500 condenser tubes are made from brass (CuZn29Sn1), tube dimensions are 30 x 1 mm and the total filling volume of the water side of the condenser is 137 m³. Figures 9 and 10 show the inlet tube sheet and the tube inner surfaces before and after the cleaning. In total the cleaning was done over seven days (one shift operation) and the contact time of the active foam in the condenser was only ten hours. Tubes, tube sheets and water boxes were completely cleaned, producing only 20m³ of liquid waste that needed to be disposed of after pH correction.
● Combined cycle power plant
The second case study demonstrates that foam cleaning is able to remove scale even in complicated configurations, where other
24 | March 2026 |
www.modernpowersystems.com Figure 8. Foam cleaning of a condenser
cleaning methods fail. The intercoolers of a combined cycle power plant gas turbine compressor suffered from phosphate and other mineral residues that entered the heat exchangers due to the unintentional use of boiler water instead of the specified demineralised water for online compressor washing (Figure 11).
Figure 7. Foaming skid connected in series for chemical cleaning
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