Descaling and Pickling Water-Cooled Compression Chillers

1) With the condenser heat transfer surface being one of the main four components of a water-cooled chiller system on the one hand, and the possible reduction of heat transfer capacity in the condenser due to precipitation over the said surfaces on the other, the condenser is required to be cleaned regularly every year (depending on the properties of the water and the climatic conditions, cleaning may need to be repeated during the season).

2) The water circulating the water-cooled compression chiller is the main heat transfer agent; therefore, it must be controlled in terms of precipitation, corrosion, and biological contamination. Further, all screens must be regularly inspected in two to three-months intervals. 3. Condensers in chillers need descaling after a while, which is carried out as follows:

3.1) If the condenser can be opened, inspect the inside of the device for foreign bodies, such as metal or plastic bits and check where they in from. For example, if you found metal or rust, inspect all screens, pumps, and towers and change them if needed.

If there is a minuscule amount of precipitates in the condenser or you are dealing with a low-capacity water-cooled compression chiller, add a certain amount of descaler to the basin of the cooling tower after its fans are shut down, then turn the condenser on and let the water–descaler mixture clean the path and the condenser. This must be repeated until the condenser is clean. The amount of liquid acid required for descaling can be estimated by 20 lit of descaler for each 15–20 tons of refrigeration. The length of the path is also important to take into account. After the condenser is cleaned with acid, the pipes and the condenser must be washed with clean water, making sure the remaining acid has left the equipment. Anti-corrosion acids must be used in this method to prevent damages to the cooling tower fan.

3.2) In case of massive amounts of precipitate in the condenser, or a high-capacity chiller, another method is used. First, the precipitates are pushed out of the condenser by water pressure, then, after making sure no condenser pipe is blocked (if the inside of the pipes can be inspected), the type of the precipitate must be identified to select a suitable descaler.

However, in most regions, precipitates are of the calcium type which is the result of high water hardness and inadequate softening processes and requires using descalers such as A.N.A.L or natural descalers.

4) After blocking both supply and return lines between the cooling tower and the condenser and ensuring there are no leaks in the valves (if the valves are not sealed, blind caps can be used). Pickling can be carried out using an electric pump with an appropriate head and flow rate and a tank sized in proportion to the capacity of the condenser. To ensure all fittings and pipes are fastened in place and all condenser pipes are open, the process is carried out first using only water by filling the pickling tank with water—preferably hot—and pumping the water to the lowest part of the condenser. After the condenser is filled with water, it is depleted from the top, returning the water back to the tank.

5) After making sure the water circulated with no difficulty, the diluted acid (diluted by hot water) is pumped (the impeller and housing of the pump must be made of corrosion-resistant materials such as plastic) from the tank to the condenser. In the end, the output acid is, again, discharged back into the tank. After washing off the precipitate, the process is repeated with clean water, then neutral fluids, and then water again.