Cooling Tower Pumps
Warm water from a heat source such as a commercial air conditioning or industrial equipment is pumped to the top of the cooling tower. The warm water enters the cooling tower and is evenly dispersed over the tower fill. It then flows down the fill which spreads the water over a large surface area increasing evaporation and thereby removes heat.
Large fans draw air across the fill which accelerates and further cools the water. The cooled water continues to flow down into the tower sump and back to the system to cool the heat source.
As system water evaporates, only pure water is lost. All of the elements in the system water remain behind in less water volume. To make up for the water that is lost with evaporation, fresh water is introduced into the cooling tower system through the make up line. This fresh water carries additional elements into the system water where they accumulate.
The more water that evaporates, the greater the need for makeup water to replenish the system and the faster the concentration elements build up. To reduce the concentration developments in the system. a bleed off valve opens and dumps a portion of the saturated water, to drain as wastewater. The wastewater discharge must also be replenished by adding even more fresh water makeup water to the system.
Because makeup water carries fewer elements than the system water, it will slowly reduce system concentration. During normal operation, evaporation bleed off and make up are balanced to maintain the proper water volume while creating a continuous open loop.
The basic principle behind boiler operation is relatively simple. Water is heated by a burner and steam is produced. As the water is evaporated the level will naturally fall and fresh water must be pumped in to keep the level topped up. The water level can also be extremely sensitive to changing circumstances, such as an increase in steam demand.
The primary purpose a boiler control system is to make sure that the water level stays between upper and lower limits. If it falls too low, the heating surfaces could become exposed and the boiler would overheat. Too high and the water could be sucked into the steam take-off point leading to poor quality steam and carryover.
The compact design of modern boilers means that this operating band is very narrow so accurate control has become increasingly important for safe and efficient operation.