Predictive Maintenance (PDM) program is an important philosophy, which can be applied to effectively manage plant maintenance. Under PDM program `Signature Analysis' technique is widely used to study the vibration behavior of machines. Cooling towers in process industry are mainly engaged for evaporation of water to reject heat from processes (such as cooling the circulating water used in oil refineries, chemical plants, power plants and building cooling). In the present study, PDM program has been applied in these cooling tower fans of a process plant as a case study to reduce the severity of their vibrations. The outcome of the present research work is, reduced vibration of fans, thereby improving the fan reliability. The results of study suggested that vibration level of the fans could be reduced by 63%.

Predictive Maintenance (PDM) program helps in planning the jobs in an effective manner. Vibration measurement and collection and analysis of data tell us about the health of the machine and are one of the many tools which are used in preventing sudden failures which are expensive. The decision to establish a PDM is the first step toward controlling the maintenance costs and improving process efficiency in a plant (Anthony Kally, 1991 and IRD Training Manual on Vibration Analysis, 1999). Cooling towers are required to remove heat from the water that has been used to cool different systems throughout the plant. The water travels in an endless loop, from all the systems and then back to the tower where its heat is removed and sent back to the same systems. On top of the cooling tower, there is a large fan that draws the air through the fill, cooling the water and exhausting the hot air into the atmosphere. The fan is a very critical part as far as the performance of the cooling tower is concerned (Copp Ralph and Aaron Pieroway, 2001; Brown Michael, 2003; and Dave Gallagher, 2004). Operators and technicians often detect unusual noises or vibrations on the shop floor or the plant where they work on a daily basis. In order to determine whether a serious problem actually exists, a vibration analysis is done. If a problem is indeed detected, additional spectral analyses can be done to accurately define the problem and estimate how long the machine can continue to run before a serious failure occurs. Vibration measurements in the analysis (diagnosis) mode can be cost-effective for less critical equipment, particularly if budgets or manpower are limited.

Another application for vibration analysis is an acceptance test to verify that a machine repair was done properly (Forrest Perdue, 1994; Grall, 2002; and Hardy, 2005). The analysis can verify whether proper maintenance was carried out on bearing or gear installation, or whether alignment or balancing was done to the required tolerances. Additional information can be obtained by monitoring the machinery on a periodic basis, for example, once per month or once per quarter. Periodic analysis and trending of vibration levels can provide a more subtle indication of bearing or gear deterioration, allowing personnel to project the machine condition into a foreseeable future. Literature review reveals that a lot of research has been done in the field of vibration analysis regarding the assessment of running machine health (Forrest Perdue, 1994; Copp Ralph and Aaron Pieroway, 2001; Grall, 2002; Davze Gallagher, 2004; and Hardy, 2005). The PDM program was also applied in many fields and remarkable improvement was observed in the machinery behavior. Not much work has been reported hitherto on the application of PDM program in the field of cooling tower fans for process industry. In this study, an effort has been made to implement the PDM program as a case study in one of the process industries to improve the performance of cooling tower fans.

Mechanical Engineering Journal, Predictive Maintenance Program, PDM, Signature Analysis’ Technique, Cooling Towers, Process Plant, Vibration Measurements, Periodic Analysis, Mean Time To Repair, MTTR.