Saturday, September 19, 2015

Mechanical Equipment Supporter in Cooling Tower

The framework of a cooling tower is not totally inflexible, even on concrete towers which utilize structural members of relatively massive across section. Considering the tremendous torsional forces encountered in the operation of large fans at high horsepower, it becomes apparent that some means of assuring a constant plane-relationship throughout the motor-gear reducer fan driver train must be provided in order to maintain proper alignment of the mechanical equipment.

For smaller fan units, unitized steel weldments of structural cross section serve well. However, the forces imposed by the operation of larger fans dictate the use of unitized supports of greater sophistication. These usually consist of large, heavy-wall torque tubes welded to outriggers of structural steel.

Customary material for these unitized supports is carbon steel, hot-dip galvanized after fabrication, with stainless steel construction available at significant additional cost. The combination of heavy construction, plus galvanization, generally makes stainless steel construction unecessary

Friday, September 18, 2015

How to Control Temperature in Cooling Tower

Temperature control is an important consideration in industrial cooling tower technology. The cold water temperature from a cooling tower reduced with any declination in wet-bulb temperature or heat load assuming continued full-fan operation and constant pumping rate.

Many processes benefit from reduced water temperature, with product output or process efficiency increasing with colder water temperatures, offering little incentive for the user to operate the tower at anything less than full capacity.

On the other hand, there are any number of processes where cold water temperatures below a certain level are either non-rewarding or in some cases, actually harmful to the process. Those situations offer the opportunity for significant energy cost saving, brought about by proper operation of the tower.

Cooling tower water distribution systems whether spray-type or gravity-type are calculated to produce maximum efficiency within a relatively narrow range of flow rates. Appreciably high flows produce either over pressuring or spray systems or overflowing of open hot water basins. Significantly lower flow produce inadequate water coverage on the fill, which not only disrupts heat transfer efficiency, but also increases the work load of the fan (s).

Source: Cooling tower fundamentals pdf file

Thursday, September 17, 2015

Reasons for Foaming & Discoloration in Cooling Tower

Did you know, if a new cooling tower is put into operation then heavy foaming occurs? Yes,
sometimes you may see heavy foams occurring as you start operating the tower. However, this type of foaming usually subsides after a relatively short operating period.

Persistent foaming can be caused by the concentrations of certain combinations of dissolved solids, or by the contamination of the circulating water with foam-causing compounds. This type of foaming is often alleviated by increasing the rate of blowdown. In extreme cases, foam depressant chemicals must be added to the system, which are available from a number of chemical companies.

Woods contain some water soluble substances and these commonly discolor the circulating water on a new tower. The discoloration is not harmful to any of the components in the system and can be ignored in that regard.

However, a combination of foaming and discolored water can result in entrained in the air stream and discharged out the fan cylinders. In those cases, operation of the fans should be avoided until the foaming is controlled.

Wednesday, September 16, 2015

Expert Tips for Cleaning Cooling Tower

Cooling towers need to be clean on regular basis to minimize bacterial growth, including Legionella
Pneumophia (which causes Legionaires disease) and avoid the risk of sickness or death. Cooling tower operators should always follow maintenance procedures which reduce to a minimum, the opportunity for bacterial contamination.

Regular cleaning procedures are a basic concern for cooling tower operators in HVAC industry. Because the towers are close to public, the risk of infection from poorly maintained cooling towers is high. Visual inspection of towers should take place weekly when the towers are operating. Flushing and cleaning should be performed before and after each cooling season, twice per year is the preferred frequency.

Cooling tower engineers often suggest that a reliable water treatment program including biocial control means, should be maintained at regular interval of time. 
Filtration devices must be used to reduce the suspended solids concentration, this increasing the effectiveness of the water treatment program. 

It is necessary to drain down the water system, clean all debris and dirt from the tower. Refill the water basin with clean water. While operating the cooling tower pumps and prior to operating the cooling tower fan, execute one of the two alternate biocidal treatment programs.

Resume treatment with biocide which had been used prior to shutdown.

Treat the system with sodium hypochloride

Once the above two treatment is successfully completed, the fan can be turned on and the system can be returned to service.

Tuesday, September 15, 2015

How to Control Biological Growth in Cooling Tower

Cooling tower performance is highly disturbed due to biological growth following scale formation in
certain parts. Slime, a gelatinous organic growth and algae, a green moss is common formation in the cooling tower interior. Their presence interfere in the tower efficiency. 

Water treatment companies provide proprietary compounds to control the growth of slime and algae. Chlorine and chlorine containing compounds are also effective algaecides and slimicides, but excess chlorine can damage wood and organic materials of construction. 

In case, chlorine has to be used it should be added intermittently as a shock treatment and only as frequently as necessary to control slime and algae. Residual levels of fee chlorine must be removed from the water. Chlorine or chlorine containing compounds has be added carefully since high levels of chlorine will occur at or near the point of entry into the circulating water system. This kind of situation cause a localized reduction of pH and resultant corrosion.

One best way to get rid of scale formation and corrosion problem is to install scale ban in the system. It is a non-chemical equipment which requires no maintenance and ensures zero pollution. For details, feel free to contact engineers @ CASE Group.

Monday, September 14, 2015

How to Control Noise in Cooling Tower System

Maintaining low sound pressure is becoming increasingly important in cooling tower system. It has
become compulsory in commercial field. Noise is objectionable sound , intangible and relative. A sound pressure level that may irritate one person can be quite acceptable to others. However, as any user who has experienced a noise complaint knows, the irritated few can become very vociferous and their cries are usually heard. 

Sound generated by a cooling tower compiles from the the energies expanded by the motors, the speed reduction or power transmission units, the fans, and the cascading water, all of which combine to produce a typical sound level of 70 dBA at a horizontal distance of 50 feet from the louvered face of the tower. 

Since sound is manifestation of consumed energy, the same parameters that result in an energy efficient tower also produce a tower with reduced noise generating capability.

Equipping a tower with two-speed motors can effect a periodic reduction in noise output for the time that the fans are operated at half-speed. 

An over-sized tower designed for reduced fan speed and power will generate significantly less noise. Externally mounted sound attenuators can be added to the tower.

Saturday, September 12, 2015

How to Measure Noise of Cooling Tower

Known to all, sound energy is transmitted through the atmosphere in the form of pressure waves. Sound pressure levels (SPL) is expressed in terms of decibels (dB). The frequency of sound is expressed in Hertz (cycles per second). 

The overall measurement of sound is converted to an A-scale weighted level (dBA). In order to identify and evaluate an objectionable component of a broad band of sound, the sound pressure levels at various frequencies must be known. To facilitate this, the human sensitive sound spectrum has arbitrarily been divided into eight frequency bands called octaves. These bans have center frequencies of 63, 125, 250, 500, 1000, 2000, 4000 and 8000 Hertz. The instrument utilized to measure the sound pressure levels within these specific bands is known as an Octane Band Analyzer.

To check correct value obtained with the Octave Band Analyzer, it is necessary to develop standards of comparison purposes. For more info, contact cooling tower engineers.