The natural draft cooling tower is an open, direct-contact framework.
It works with the help of a heat exchanger, permitting heated water from the tower to be cooled through direct contact with outside air. The heated water is splashed from spouts inside the pinnacle. This increments both the temperature and the humidity of the air in the tower. The hotter, moister air moves to the highest point while the water is gathered at the base. The natural air supply is situated in the lower part of the tower to exploit the distinction in thickness between the hot air at the top and the barometrical air outside the cooling tower.
Exposure
The natural draft cooling towers are continuously exposed to unforgiving working conditions. As such, the conditions can foster extreme erosion of the inserted steel support, substantial delamination, and spalling. Condition evaluation of cooling towers is tiresome. This is mostly because of their size, math, and functional requirements, yet cautious examination can give basic information to viably describe the primary wellbeing of the tower, the strength of its support, and focus on the fixings that are holding the natural draft cooling tower still.
All of it to amplify the shelf life. A cooling tower analysis is performed to conduct a preliminary evaluation, upon which the information is gathered, deciphered, and used to create and carry out fixation of the cooling towers that undergo terrible corrosion. While assessing the natural draft cooling towers, the erosion rate, and the expected service life is primarily considered.
Thereafter, an audit of the plan and establishment of the Impressed cathodic protection and galvanic cathodic protection exposes the ongoing cooling tower difficulties that create an operational hindrance.
Repair Of Natural Draft Cooling Tower
Considering the health, cost, and strength of the cooling towers, the repair is done to accomplish a service life expansion of somewhere around 25 years. To accomplish this, the cooling tower is usually put on standby, to achieve most of the repair, without stressing the operational efficiency.
Cooling tower manufacturers primarily begin the repair from the upper part of the tower if the cooling tower undergoes a high amount of corrosion and delamination in the upper part of the tower shell, where an engineered demolition is done to rebuild the shell above the throat. Underneath the throat, if the amount of corrosion is less serious, substantial fixes are done both on the inside and outside of the shell. The pillars responsible for maintaining the structural capacity by way of mitigation, are repaired to keep the ongoing strength of the cooling tower.
Cathodic Protection
The cathodic protection for the natural draft cooling towers is done to repair the strategy of the entire tower and prevent it from continued deterioration. The impressed cathodic protection of the tower is done to control the voltage levels at different locations throughout the service life of the tower. In some cases, only one cathodic protection is employed. However, on the contrary, given the existing condition and the need to repair the cathodic system – three types of protections are also employed.
The type of anode used to repair includes the titanium suboxide ceramics tube anodes that are mostly of a concrete base and are heavily reinforced. To protect the height of the existing shell, mixed metal oxide further coated with titanium ribbon anodes are placed to prevent corrosion. Additionally, galvanic cathodic protection is employed based on the durability of the components. Galvanized jackets are installed with the cement motor in fiber-reinforced polymer forms.
While maintaining the natural draft cooling towers a substantial amount of consideration needs to be paid in case there is loss of protective properties, in the form of delamination, spalling, blistering, and scaling. The indications call for the repair of the operational cooling towers. There are structural safety hazards including deep cavities which consistently reduce the thickness and integrity of the shell, therefore increasing the amount of corrosion experienced by the steel reinforcement. The ultimate motive is to prevent degradation and repair the surface defects.
Cooling towers experience limited durability mostly because the thermal constraints during operation induce concrete cracks. A detailed investigation needs to be done in case the chimney is damaged or the cooling tower expresses mechanical actions while coming up with crack patterns. While the power plant operates, the evaporative cooling tower also undergoes hygric effects that induce thermal damage, further leading to deep cavities.
The design of the cooling towers is largely responsible for the shelf life. In some cases, cooling towers may only experience more cracks due to a lack of circumferential reinforcement. As such, a proper investigation of the actual repair needs to be done. It may not be the case that the entire tower needs to be repaired from scratch or replaced because of minor issues. Operational efficiency comes into play when the ongoing difficulties can be categorized as major and minor.
