Page 599 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Preventive and Predictive Maintenance Best Practices Best Practice 1 1.6

Best Practice 11.6

Always perform transient oil system tests (main oil pump did not properly respond during plant operation resulting in
forced trip and aux. pump start without system instability a unit shutdown on low oil pressure.
or shut down) prior to shutdown to ensure optimum oil If it is suspected, from past experience, that the transient test
system operation and reliability. will not be successful it is recommended that advance engineering
These tests performed during equipment shutdown (at turn- be performed for installation of a properly sized and instrumented
arounds) do not duplicate operational characteristics and lead to false dual stainless steel accumulator assembly during the turnaround.
conclusions regarding system transient response. See B.P. 7.14.
Follow the procedure noted below (see Supporting Material) im-
mediately before the turnaround and take appropriate action to correct Benchmarks
issues during the turnaround. This best practice has been recommended since the late 1980s, to
identify and resolve long term critical oil system reliability issues that
Lessons Learned had previously caused large unit revenue losses over the life of the
Oil system transient tests performed during a turnaround critical machinery train.
have shown acceptable results only to find that the system

B.P. 11.6. Supporting Material correctly such that all system design objectives have been
obtained and that equipment reliability is optimized.
Functional testing One remaining factor to be proven is the successful operation
of the system with the critical equipment unit in operation.
Having satisfactorily installed and flushed the auxiliary system, During initial start-up, it is recommended that the functional
all auxiliary equipment should be functionally tested and all test be re-performed with the unit operating. While this advice
instruments and controls checked for proper setting prior to may seem dangerous, unless the unit operators ensure that the
operation of equipment. A functional test outline and procedure subject system has the ability to totally protect critical equip-
is included in the end of this section. We will highlight the major ment while operating, auxiliary equipment will never be tested
considerations of the procedure at this time. while the unit is in operation.
It is recommended that the console vendor and/or the Remember, critical equipment is designed for 30 years or
equipment purchaser prepare a detailed field functional test greater life. The components that comprise the auxiliary system
procedure and calibration check form. The format of this are many and have characteristics that will change with time.
procedure can follow the factory test procedure if this is ac- Therefore, reliability of auxiliary systems can only be main-
ceptable. As a minimum, the auxiliary system, bill of material, tained if the systems are totally capable of on-line calibration
and schematic should be thoroughly checked in order to in- and functional checks. The functional pre-commission pro-
clude the calibration and functional test of each major com- cedure should be modified to include an on-line periodic func-
ponent in the auxiliary system e that is, components on tional checking procedure. Such a procedure is included at the
consoles and at unit interfaces. A detailed record should be end of this section.
kept of this functional test procedure. This will help signifi- At this point, we can clearly see that the major determination
cantly during the operation of the unit. The test procedure of continued equipment reliability rests with the operation,
should be accomplished without the critical equipment running calibration and maintenance of the equipment. In order to
initially and then with the auxiliary system at design operation assume maximum continued auxiliary equipment reliability,
conditions as closely as possible. The functional test procedure periodic on-line functional checks and calibrations must be
should first require that all instrumentation is properly performed. How can this be done? The only way is by
calibrated before proceeding. Each specific functional test convincing plant operations of the safety and reliability of the
requirement should then be performed and results noted. If procedure for on-line checking. This can be reinforced during
they do not meet specified limits as noted, testing should stop pre-commissioning by including operators in functional testing
and components should be corrected at this point. Each step checks and on-site training sessions to show the function of the
should be followed thoroughly to ensure each component system. A site training course modified for the specific equip-
meets all requirements. It is recommended that operators ment would prove immensely valuable in achieving those
assigned to this particular unit assist in functional testing to results.
familiarize themselves with the operation of the system. In Only by involving unit operators in the pre-start check ups
addition, site training courses should be conducted prior to can it be hoped to establish a field functional checking
functional test to familiarize operators with system’s basic procedure that will be utilized and followed through. Re-
functions. This training, again, significantly increases un- member, a pressure switch less than $400 in cost could cause
derstanding of the equipment and ensures unit reliability. equipment shutdown that could reduce on-site revenue on the
Satisfactory acceptance of a functional test then ensures that order of $1-2m U.S. dollars a day. The pressure switch selected
the unit has been designed, manufactured, and installed could be the best, the highest quality in the world, properly

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