Page 226 - Intro Predictive Maintenance
P. 226
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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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