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cooling towers - pet series

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cooling tower specifications

General

This series of cooling towers are designed for continuous & heavy duty operation in industrial cooling water system. The cooling towers are designed to operate within a harsh industrial environment where airborne particles present at surrounding is unavoidable, contamination of the cooling water with dissolves solids is expected and formation of scales and clogging of fill packing is anticipated.

Cooling Tower Type

PET Series cooling towers is the induced draft cross-flow type with timber splash bars as the fill packing for the heat exchange transfer surface. Although cooling towers can operate individually as a single unit, they can also be assembled into multiple cells and operate as a single cooling tower. The cooling tower is shop fabricated and shipped to site completely knock down and ready for immediate site assembly and erection without further fabrication work required. As such, they are also commonly termed as field erected cooling tower. The cooling tower are usually supported by reinforced concrete supporting columns at all tower columns within a reinforced concrete cold water basin with suitably design holding volume of cold water to provide uninterrupted supply of cold water to the process.

Tower Mainframe Structure

The entire cooling tower mainframe structure and all members forming the cooling tower are constructed from the rain forest of Malaysia, Chengal i.e., Balanocarpus heimii. Chengal timber is a Class 1 hardwood and is highly resistant to decay when in ground contact or in persistently damp or poorly ventilated situations. This timber has been used for structural members which require high strength and durability, railway sleepers, wharf and bridge constructions, poles, piles, mining timbers and boat building.

Chengal hardwood with superior mechanical properties offers the highest strength required to provide a robust framework to support all the cooling tower components such as the fan machineries and power transmission system, hot water distribution system, splash bars and drift eliminators, as well as the tower casing and louvers. The very strong and robust framework is also vital and essential in anticipation of unusual operating weight imposed onto the cooling tower when the splash bars system has been contaminated and accumulated with sludge and scales trapped within the fill packing section.

Chengal hardwood is also naturally durable which is commonly used for marine engineering construction, is capable of withstanding long-term contact with untreated industrial water application where water is highly acidic or alkalic, this timber has proven to be highly resistant to chemical attack. Since this species of timber is a naturally durable hardwood, chemical preservatives are difficult to penetrate into the timber in treatment processes; it is used without chemical treatment with expected operating life span of the tower structures of at least 15 years. This extremely superior property avoids the failures experienced by chemically treated timber used for cooling tower construction where preservative chemicals are bleached out from the timber and eventually only leads to timber deterioration.

All load carrying tower columns are directly seated onto the concrete supporting foundation below. All vertical and lateral loadings are transmitted to foundation below by the tower columns and bracing members to the reinforced concrete columns and are evenly distributed to the foundations. All tower columns are secured by SS304 stainless steel footing brackets and anchor bolts to the supporting reinforced concrete columns. All loads carrying structural framework members are through bolted with SS304 stainless steel bolts and nuts while non-load carrying components such as FRP hot water basin panels and casing are attached to tower structures with SS304 stainless steel screws. Since operating weight of the cooling tower is substantially increased due to the formation of sludge in fill packing section and in worst condition, the operating weight of the cooling tower is expected to quadrupled, the tower structures are designed to withstand such excessive operating weight.

Hot Water Distribution

The hot water distribution system is the open basin type located on top of the cooling tower with polypropylene nozzles embedded on the FRP basin floor to distribute hot water by gravity to the fill packing section below. For multiple cells cooling tower, each cell will be provided with a single inlet pipe connection to regulate the hot water to each cell while distribution of the hot water within the tower cell will be provided with a hot dip galvanized cross over pipe with all flow control valves attached at discharge outlets to regulate volumetric flow. Water levels of all individual hot water basins are regulated and maintained at similar level by the cast iron flow control valves at each pipe discharge outlet. Hot water discharge from the flow control valves enter into the FRP splash boxes to ensure even distribution as well as prevent water splashing out of the cooling tower. Since performance of the cooling tower is very dependent upon the distribution of the hot water over all the splash bars, a very efficient splash box of FRP design has been developed to provide even distribution and prevented water which may contain water treatment chemicals from splashing to the tower surroundings or onto the personnel operating the cooling tower.

Fill Packing System

The fill packing system for the PET Series consist of the timber splash bars of Chengal hardwood supported on grids made of heavy gauge SS304 stainless steel. The splash bars are installed in the cooling tower extending from the operating water level in the cold water basin to the hot water basin above and covered the entire air inlet area along the longitudinal sides of the tower. Each timber splash bars is supported by 3 pieces of supporting grid and each grid is directly attached to tower framework member using grid hangers and SS304 stainless steel screws. Grids are welded at all contact points using resistance welding to ensure the dimension and shape is maintained at all time. This is extremely important to prevent deformation or distortion of the grids to ensure all the splash bars are maintained at its original configuration even when they are clogged with sludge which can be very heavy and to withstand the extraordinarily operating weight.

All splash bars are installed with a predetermined arrangement on the supporting grids to form an "open" configuration to evenly expose maximum surface for hot water and ambient air interaction for heat exchange. The configuration also prevents clogging of the fill packing by foreign materials or debris, scales build up and sludge accumulated. The splash bars arrangement also provides substantially large openings for cleaning of the fill section using water jets to dislodge the build ups from the splash bars and collected from the cold water basin below.

Drift Eliminator System

Since PET Series cooling towers are specifically designed to handle all kinds of industrial cooling water including very dirty and contaminated water, the drift eliminator systems installed are capable of allowing high deposition of muck commonly found in most cooling tower as well as allowing the drift eliminator system to be cleaned without damaging the materials easily. The drift eliminator system is installed inside the tower at the entire air exit plane after air passing through the fill packing system. The drift eliminator system is designed with a two pass drift elimination to remove all the larger water droplets carried by the moving air stream and to eliminate the drift loss to as small as 0.01% of the total circulation flow rate.

As such, the drift eliminator panels are made from extruded PVC profile which provides features which restrain airborne water droplets as airflow passing through the eliminator panels. The extruded materials used for the eliminator panels are made sufficiently thick to provide the rigidity and durability for the application. Moreover, eliminators are factory assembled into panels which are readily to be installed into the cooling tower with ease thus making installation, maintenance and replacement becomes very easy. This innovative drift eliminator system has completely address many problems previously encounter with using timber drift eliminator such as algae growth due to exposure to sunlight and missing and broken timber eliminators each time after cleaning. This drift eliminator system had also successfully proven itself far more superior to PVC drift eliminator system made of thin PVC film formed into honeycomb shape type in terms of life span and durability.

Mechanical Equipment

The mechanical equipment consisting of the fan assembly, gear speed reducer, drive shaft and electric motor forming the fan machinery to produce the airflow required for the tower must be supported on a common sturdy base. It is located on the top of the cooling tower along the tower axis and housed within a FRP fan stack to operate efficiently and safely.

The fan assembly is the energy efficient axial flow adjustable pitch propeller type with the fan blades made of hollow FRP construction and the fan hub made hot dip galvanized steel construction dynamically balanced with the fan blades tip speed operating not exceeding 60 m/s. The fan assembly is mounted on a spiral bevel gear speed reducer and operates at an optimum speed to achieve best tower performance. Gear speed reducer used has been specifically designed for cooling tower application and has power rating at least 2.0 the power of the motor power rating. Gear speed reducer used is oil-lubricated type with the lubrication pipelines being extended to the outside of the fan stack to facilitate inspection and maintenance.

Electric motors of various voltages, frequencies and operating speeds can be supplied but only reputable manufacturer approved by Panwater will be used on the cooling tower in order to enjoy the standard cooling tower warranty provided by Panwater. As a standard, electric motors used are conforming to IEC Standards and is totally enclosed fan cooled type with IP55 protection and Class 'F' insulation to provide complete protection against contact with dust and the effects of water. Its materials of construction should have cast iron frame frames, terminal box, end shields with oil seals, and polypropylene cooling fan. The motor is located outside the humid air stream discharge by the fan assembly and seated on the unitized mechanical equipment support common to the gear speed reducer to avoid contamination of electric motor by the saturated and humid discharge air from the cooling tower. All hold down bolts used for the motor are of stainless steel material. Electric motor is designed to operate with at least power rating 1.15 times to maximum brake horsepower of the fan at duty.

Mechanical torque from the electric motor is transmitted to the gear speed reducer via a floating type drive shaft. The drive shaft is designed with mechanical power rating of at least 2 times the power rating of the electric motor and is constructed from carbon composite. Flexible elements of the drive shaft are also made from carbon composite while all hardwares of the drive shaft are made of SS 316 stainless steel. The drive shaft is dynamically balanced at its operating speed and no lubrication of any parts is required.

Having all the mechanical components carefully designed and put together as an complete fan machinery, it is very important that all these mechanical components are mounted on a well designed and constructed mechanical supporting base to ensure the entire fan machinery is operating efficiently and safely to maintain a long life span. Mechanical support for PET Series fan machinery are mounted onto the water distribution cross-over pipe while the larger tower models has its independent mechanical support fabricated from carbon steel and hot-dip galvanized after all fabrication is completed. Emphasis has been given to the design of the mechanical support to ensure alignment of the drive shaft is maintained within tolerance at all time during operation.

Fan Stack

The entire fan assembly system is housed within an aerodynamically bell mouth FRP fan stack to minimize velocity pressure loss as airflow passing through the fan stack. FRP fan stack are designed with box profile reinforcement ribs and molded with thick layers of FRP materials to ensure very strong hoop stress to maintain rigidity during operation and very long life span as well as to provide safety protection to operator. Velocity recovery stacks for large diameter fans are also available for high efficiency fan performance for optimum power consumption. The fan stake is assembled from multiple panels of similar design forming into a circular cylinder with all flanged joints located at the outside for easy assembly and dismantling.

Tower Cladding & Air Inlet Louvers

The entire external of the cooling tower consisting of the cladding walls and air inlet louvers are constructed with FRP panels. FRP cladding panels are molded with box rib designs overlapped at all joints to ensure complete sealing to prevent water and air leakages and are firmly secured directly to tower structure to withstand wind load. Cladding at the tower end wall extends from the fan deck level to the base of the tower and below the operating water level. No air leakage is allowed at the end wall cladding. Access door made of FRP materials is provided at both end walls and at each cell partition. All doors are hinged and can be operated at any time with ease. FRP louver panels are freely supported on louver holders to prevent water from splashing and diverting water back to cold water basin. They are made easily removable for access into the fill packing section for cleaning and maintenance.

Access To Fan Deck & Internal

PET Series cooling towers internals are accessible through the FRP doors installed at the end wall and partition. All the cooling towers are provided with internal timber walkway extending the entire length of the cooling tower for inspection and to carry out maintenance routines. Areas accessible are the drift eliminators, splash bars section after removal of drift eliminators, tower structures and mechanical equipment.

The fan deck level of the cooling tower is accessible by ladder or stairway installed at the end-wall and the entire fan deck is surrounded by safety handrail in compliance with OSHA requirement. Areas accessible at the fan deck level are fan machinery, hot water distribution basin and flow control valves. This safe and easy access allows periodic inspection and maintenance works for the mechanical system such as checking of lubrication system, detection of abnormal vibration caused by the rotating equipment, tightening of loosened fasteners and to carry out preventive maintenance requirement. Access to the flow distribution system allows operation of the flow control valves to balance flow to all the hot water basins are maintained and cleaning of the hot water basin and the nozzles is done periodically so that cooling tower is performing efficiently. All towers are installed with perimeter handrail surrounding the tower at the fan deck level to ensure accessing to the various areas on the fan deck is safe.

Cold Water Basin & Foundation

The cold water from the cooling tower is collected by the cold water basin below. Cold water basin for the PET Series cooling tower are normally construct with the reinforce concrete with all the tower foundation and supporting columns being constructed within the basin. Although other basin materials have been used for some special application, concrete basin is highly recommended for most industrial applications due to various reasons and advantages.

The most obvious advantage of the concrete basin over the others is due to its long life span and requires minimum maintenance or repair during its entire service life. A sufficiently large basin retention volume is a pre-requisite for the safe and efficient operation of many continuous industrial processes especially any interruption of supply of make-up water may cause major plant shut down. Moreover, in most industrial processes, a complete plant shut down requires all equipments in the plant to be shut down in stages and requires the cooling water to be circulated through all the equipment during the entire shut down process. Thus having an adequately designed basin with sufficiently large retention volume for the cooling tower will ensure there is always cooling water available for any unexpected catastrophe.