Thirty years ago Alfa Laval patented its first automatic, self-cleaning filter. Over the years this technology has been further developed and refined. Recently a large-capacity model was added to the range – the ALF80-R.
When the supply of high-quality water for closed loop cooling is limited or as in some parts of the world very expensive, a widely accepted solution is to use water from the sea, lakes and rivers. However, solving one challenge creates another. In this case, preventing particles in low-quality cooling water from causing excessive fouling and expensive downtime.
The ALF can be used in many sectors of industry, including power plants and district heating and cooling systems. It operates as an integral part of such a cooling system to remove debris that can foul and clog plate heat exchangers, tubular condensers, cooling tower spray nozzles and similar equipment. The filter provides protection for all downstream equipment, helping ensure better performance along with longer service life, increased uptime and reduced maintenance costs.
The ALF80-R is the largest member of the filter portfolio family to date. This new model is distinguished by a particularly large capacity, capable of dealing with the escalating demand for greater quantities of cooling water. Higher capacity means fewer filters are needed, resulting in reduced space requirements and less piping.
The complete product range, with connections from 100-800 mm, features a flexible design that makes it easy to fit and install. Automatic backflushing makes these filters easy to operate and helps ensure continuous operation, resulting in less down time.
The low pressure drop through the filter permits a greater pressure drop for the downstream PHE or condenser, which in turn makes it possible to use a smaller heat transfer area and therefore fewer plates.
In terms of how it works, water or other media is first pumped into a filter basket. After having passed through the filter basket, the media is discharged. Impurities with debris or other objects are kept inside the filter until flushing. As an option the process can be controlled through differential pressure measurement. However, a timer is always used in order to prevent the basket getting too dirty.
Flushing is conducted in two steps. At the first step, a flushing valve is opened and debris collected in the debris section, is released. At the second step (back flushing), a flow diverter valve placed in the basket closes while the flushing valve remains open. The closing of the diverter valve causes the full stream to divert.
After passing through the inlet section of the filter basket, a part of the stream back flushes the rear section of the filter basket to dislodge stuck debris. This ensures efficient cleaning of the basket, and debris is thus released through the flushing outlet. Meanwhile the majority of the stream passes through the filter outlet being cleaned as usual.