NEWS MAINTENANCE OF EVAPORATIVE CONDENSERS CFR-C AND COOLING TOWERS REF-C The life of any industrial equipment , be it an evaporative condenser or a cooling tower, also depends on the correct maintenance of its various parts. In this article we will try to specifically analyse the routine maintenance activities to be carried out on Decsa's CFR-C closed circuit evaporative condensers, made of Z-725 galvanised steel sheet, equipped with centrifugal fans and ideal for industrial refrigeration applications. We would like to remind you that the indications given here are also valid for the closed circuit cooling tower model REF-C, which is also built with centrifugal fans and designed for water cooling in industrial and HVAC applications. The two machines differ only in the type of fluid circulating inside the coils. While in the REF-C series cooling tower only water (H2O) is circulated, in the evaporative condenser the fluid flowing is a refrigerant gas (e.g. ammonia). Both models consist of an upper exchange section and a lower ventilating section with a water collection basin. Let us start from the latter to present in detail the various activities to be carried out. ‍ When to service an evaporative condenser Routine maintenance activities on a cooling tower or evaporative condenser are generally carried out when it is scheduled to shut down equipment, a period which is in turn determined according to the needs of the plant operator. In the case, for example, of a system serving the air conditioning of a commercial complex, the cooling unit remains operational for around seven to eight months a year, so the remaining period can be used to carry out all the necessary checks and any extraordinary maintenance. On the other hand, if the unit is part of an industrial plant that operates all twelve months of the year, it is advisable to set aside consecutive days for maintenance activities and, in addition, to define a few more hours outside this period to allow for those periodic maintenance activities that require more than a single annual intervention. ‍ Routine maintenance of the water catchment area Checking belts Before carrying out any maintenance work, it should be ensured that the motor of the evaporative condenser (or evaporative tower) is switched off and that the area concerned is secured in accordance with the procedures of the applicable regulations. The first maintenance activity we suggest is to check the drive belts on the fans, an operation that should be carried out at least twice a year using a tool designed for this purpose: the tensiometer. To carry out the check, the protective grilles must first be removed by unscrewing the bolts that secure them to the structure. Next, calculate the free stroke (t), as shown in the image below, to know the force to be applied with the tensiometer. The free distance (t) defines the distance between the centre of the two pulleys, i.e. the motor pulley and the pulley connected to the drive shaft. The force to be applied by using the tensiometer is the one according to which the minimum and maximum values for type A belts and type B belts are determined. Once the free length (t) has been calculated, the centre shall be calculated and the belt shall be flexed using the tensiometer to a defined measurement based on the length of the free length. Let us consider that the force to be applied is that required to flex the strap by 1.6 mm per 100 mm of the length of the free end (t). If, for example, the free end (t) is 1 metre long, the strap will have to be flexed in relation to the one alongside by 1.6 cm. If the free length is two metres, the strap shall be flexed by 3,2 cm. It is very important to periodically check the tension of the belts: incorrect tension will shorten the life of the belt and bearing, especially if the belt is over-tensioned. Once the belt has been flexed, the tensiometer reading should be between the minimum and maximum values, as shown in the table below. ‍ Belt lubrication A second operation to be carried out during the maintenance of the evaporative condenser is the lubrication of the belts; in this case it is necessary to use a lubricating silicone spray suitable for the purpose. We recommend spraying the product on every single belt of equipment and then turning the transmission manually in order to distribute the product uniformly. If the cooling unit is not to be used for several months, it is a good idea to remove the belts and store them in order to preserve their integrity. When restarting the unit, the belts must be remounted and lubricated. ‍ Greasing the bearings Greasing the bearings is an operation that should be carried out every four months or 3,000 hours of operation of equipment. A pump containing a cartridge of lithium grease suitable for bearings is required for this maintenance activity. Above each bearing there is a grease nipple to which the pump tube is connected and then a quantity of grease corresponding to about three pump strokes should be introduced. Again, once the bearings have been lubricated, it is important to run the transmission manually to distribute the grease evenly within the bearing. Remember that an ungreased or undergreased bearing will dry out and become damaged; similarly, putting in too much grease can also cause damage to the bearings. Excessive grease can escape from the seals and introduce dirt into the bearing, inevitably damaging it. ‍ Checking the inside of the water catchment area Another important maintenance activity is to check the inside of the evaporative condenser water basin. To carry out this operation it is first necessary to manually remove the inspection door and then the protection filter and clean it. At this stage it is possible to assess whether it is necessary to clean the inside of the basin and check for sediment or scale. We would like to remind you that, in addition to correct maintenance, the integrity of any unit also depends on correct water treatment, which must be carried out by a specialised company. For any clarification on this matter, please refer to the water treatment company of your reference and to the appropriate table provided in our manual. When checking the inside of the basin, the fall of water from the nozzles to the bottom of the basin should also be checked for obstructions in the heat exchange coil: if the rain from the bottom of the heat exchange coil flows evenly over the entire surface, it is possible to rule out specific problems due to obstruction of the coil. ‍ Checking the electric recirculation pump The inspection of the water recirculation pump is a visual check to ensure that there are no signs of wear, scaling or oxidation inside the terminal box (after removing the cover). Then, with the pump in operation, it is also a good idea to check that the data from the electrical panel to which the pump is connected corresponds to the data on the nameplate attached to the pump. ‍ Maintenance of the exchange section For inspection and maintenance of the heat exchanger section, it is necessary to reach the height of drift eliminators, i.e. the top of the unit. If the evaporative condenser does not have a walkway installed on the unit, a lifting platform or a vehicle with a basket must be used. As this is work at height, it is essential to wear the PPE required for this type of activity (safety harnesses, helmet, etc.). First of all, it is advisable to remove the drift eliminators, to check their integrity (dirt, clogging) and to check the water distribution system. In particular, it is advisable to check that the water sprayed by the nozzles uniformly covers the entire surface of the exchange coil; if this is not the case, it is necessary to manually remove the secondary collectors (i.e. the pipes to which the nozzles are connected), bring them to the ground, clean them and replace them if necessary, Once all checks in the exchange section have been completed, the drift eliminators can be repositioned and the unit restarted. It is important to remember that while it is necessary to stop the motor for maintenance work on the ventilating section (checking belts, greasing bearings, etc.), in the case of the exchange section it is possible to keep the unit running, at least if maintenance work is being carried out. ‍ Decsa Srl Via Cappelletta 1 Voghera (PV) - Italy +39 0383 69411 P.I. 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