Coalescer Systems
At many locations in Central Europe and Asia, and generally in coastal areas, certain weather conditions can prevail, especially in spring and autumn, that lead to extreme formation of fog – conditions that can last for several days up to several weeks. During such periods, filter intake systems can input great amounts of moisture from the outside.
Under such conditions – especially in coastal zones – salt particles can occur in the air, together with fog, and can typically be deposited in significant amounts in fine filters. In such cases, it is particularly critical to keep these filter stages dry.
If the filters are not kept dry, it is possible for the deposited salt particles to undergo changes in their crystalline structure. They can then dissolve and pass as aerosol or liquid through the filters – and then form deposits on gas-turbine blades.
It is possible to effectively protect turbines from soluble salt or inorganic particles only by keeping the final filter stage dry: i.e., by preventing any moisture from the outside from passing into the fine-filter stage.
As solution here, the initial filtration stage can consist of vertical droplet collectors (effective for droplets > 15 … 20 µm), or of coalescer mats or cells. If circumstances require, it may also be necessary to combine both of these possibilities.
In a coalescer mat, which precipitates and collects droplets > 2 … 5 µm, the droplets run down vertically installed glass fibres, and pass into a drain system. If, during extremely moist weather conditions, the filter mats become saturated, the danger arises that water droplets are blown away directly into the downstream fine-filter stage. For this reason, droplet collectors can be installed between the mats and the fine filters, so that the blown droplets will fall into the drain system.
In addition, a second filter stage between the coalescer system and the fine filters will provide further protection. This solution ensures that the fine-filter stage will remain dry, even under extremely foggy conditions – and that the filter system will assure the overall degree of filtration required.