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In many examples given within the industry of the P-F Curve the spot indicated by a functional failure is almost always close to or next to catastrophic failure.  In reality this isn't always the case.  The functional failure can only be derived accurately if a proper functional statement (FS) is developed.  A functional statement isn't accurate without some performance standards and operating context.  Based on the performance standards within the FS a functional failure can be derived.

For instance, if we have a pump that is capable of pumping 600 gpm of water.  The process has indicated that they need a desired performance from the pump of at least 500 gpm.  Then according to the performance standards within the functional statement the pump is technically failed (Functional Failure) at 499 gpm.  The functional failure in this pump is far from catastrophic failure.  The pump could actually run for months if not years before catastrophic failure occurs.

It is for this reason, and many others, that the loss of function can only accurately be determined if a proper functional statement is develop for your assets.




Original Post

I agree, you have to have a baseline/engineered output to know what has functionally failed.

To further describe your analogy/failure description....pump is designed to move 500 gpm @ 50 psi with 1.2 specific gravity @ 110F with 20 cps viscosity. Whether the size of the pump can deliver 750 gpm or 600 gpm as long as it delivers the 500 along with the design pressure using system design specifics. You could cause a functional failure just by changing temp or SG or Visc. Keep in mind, what was designed/engineered/installed is many cases worked out on paper but in reality the actual performance is lower or higher than design

A heat exchanger/fan/conveyor/boiler/dryer/mill etc all with have design criteria to describe the capabilities of the machine within a system. If the performance of the one machine within the system changes then the system too will change.

Have seen new construction intentionally install larger wire/bases/MCC/piping etc knowing they will expand in the future using the same pipe/system. So if you increase the output of one pump then the functional failure would have to be modified to meet the new system design

Hope this adds value


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