Page 226 - Intro Predictive Maintenance
P. 226

10




            PROCESS PARAMETERS




            Many plants do not consider machine or systems efficiency as part of the maintenance
            responsibility; however, machinery that is not operating within acceptable efficiency
            parameters severely limits the productivity of many plants. Therefore, a comprehen-
            sive predictive maintenance program should include routine monitoring of process
            parameters.  As an example of the importance of process parameters monitoring,
            consider a process pump that may be critical to plant operation. Vibration-based pre-
            dictive maintenance will provide the mechanical condition of the pump, and infrared
            imaging will provide the condition of the electric motor and bearings. Neither pro-
            vides any indication of the operating efficiency of the pump. Therefore, the pump can
            be operating at less than 50 percent efficiency and the predictive maintenance program
            would not detect the problem.

            Process inefficiencies, like the example, are often the most serious limiting factor in
            a plant. Their negative impact on plant productivity and profitability is often greater
            than the total cost of the maintenance operation. Without regular monitoring of process
            parameters, however, many plants do not recognize this unfortunate fact. If your
            program included monitoring of the suction and discharge pressures and amp load
            of the pump, you could determine the operating efficiency. The brake-horsepower
            formula could be used to calculate operating efficiency of any pump in the program.

                                                                     (
                        Flow  GPM) ¥  Specific Gravity ¥  Total Dynamic Head  Feet)
                             (
                  BHP =
                                          3960 ¥  Efficiency
            By measuring the suction and discharge pressure, the total dynamic head (TDH) can
            be determined. Using this data, the pump curve will provide the flow and the amp
            load of the horsepower. With this measured data, the efficiency can be calculated.

            Process parameters monitoring should include all machinery and systems in the plant
            process that can affect its production capacity. Typical systems include heat exchang-
            ers, pumps, filtration, boilers, fans, blowers, and other critical systems.

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