Selecting a Self Cleaning Strainer for Cooling Tower Side Streams

Selecting a Self Cleaning Strainer for Cooling Tower Side Streams

A cooling tower pulls airborne dust into the basin with the air it cools, and makeup water adds solids of its own. Left alone, that material settles in the basin, fouls fill and nozzles, and eventually deposits on heat exchanger surfaces. A side stream strainer removes it continuously by filtering a portion of the circulating flow, which is why tower retrofits so often begin with the question of how to pick the right one.

Why a side stream works

Full-flow filtration of a large cooling loop is expensive and rarely necessary. Because the basin holds the circulating volume, cleaning a side stream, a fraction of the total flow returned to the basin, steadily lowers the solids concentration of the whole loop. The strainer can be smaller, the piping lighter, and the pressure drop confined to one branch of the circuit.

Sizing the strainer for tower duty

Start with the side stream flow the piping can take and the solids load the tower actually sees. Airborne dust near a construction site, a process leak into the loop, or a muddy makeup source all push toward finer screens and more cleaning cycles. Choose the screen aperture against what the heat exchangers and nozzles can tolerate, not against the minimum that will keep the strainer itself from clogging.

Materials and controls

Cooling water chemistry is rough on metals. Chlorination, cycles of concentration, and warm water all accelerate corrosion, so stainless screens and wetted parts hold up better than coated carbon steel in this service. The cleaning mechanism should trigger on differential pressure and include a manual test function, and the actuator and solenoid voltage should be checked against what the tower controls actually supply.

Matching the strainer to a supplier that knows towers

When a project calls for a self cleaning strainer for cooling tower side streams, the selection discussion shifts from a catalog exercise to a process question. YAOTONG, a Wuxi-based water treatment equipment manufacturer founded in 2007, supplies self-cleaning filters alongside cooling tower systems, so the strainer and the tower duties are considered together, backed by process design, factory testing, and commissioning support for projects in more than 30 countries.

Placing it in the loop

The typical arrangement takes suction from the circulating line or the basin, passes the side stream through the strainer, and returns it to the basin. Install the unit where the purge water has a drain within reach and where a differential pressure reading across the screen can be seen by the plant's control system, not only by a local gauge. Operators who can watch the reading tend to catch screen loading days before an alarm would fire.

A strainer on the side stream is one of the cheaper reliability upgrades a cooling system can get, but only when it is sized for the real solids load and built for cooling water chemistry. Spend the specification effort there, and the tower keeps its fill, nozzles, and heat exchangers clean season after season.