INTRODUCTION
The objectives of a plant maintenance program
should be to the improve the over-all plant reliability and safety by
preventing equipment breakdown, and to maintain the equipment in a satisfactory
condition for normal operation or emergency use; all at the lowest possible
maintenance cost.
SCOPE
The program encompasses the practical
and technical approaches to provide a complete and well rounded program to
cover every aspect of good Preventive / Predictive and Equipment Condition
Monitoring Maintenance. The scope of this procedure will cover program
development, personnel requirements and responsibilities and equipment
requirements.
MAINTENANCE
STRATEGIES
Maintenance is the combination of all
those technical and administrative actions, including supervisory actions, with
the purpose of maintaining or restoring an item to a status allowing it to
execute the required function.
Maintenance has the following main
objectives:
Productive Objective – Guarantee the availability of Plants and Equipment to Production, so that they can perform their services under the best conditions, in terms of efficiency, reliability and safety.
Economic Objectives – Ensure that the services rendered is at minimum costs with the maximum of efficiency.
Opportunity
Maintenance – Work carried where the timing is determined by other events that
can either be predictable or not predictable, e.g key equipment failure or
production shutdown.
Predictive
Maintenance – Is the preventive maintenance carried out whenever the trend of
one, or more operating parameters of an item of equipment shows an incipient
failure. The Predictive Maintenance uses measuring or monitoring devices in order to identify conditions that require correction before a functional failure occurs. Typical condition monitoring techniques are vibration analysis, crack detection, thermography, pressure and temperature monitoring, oil analysis, etc.
Using the inspection data gathered to
accurately predict the allowable lapse time and point of expected equipment failure
for initiation of corrective action prior to catastrophic failure.
Fig. 1: Bearing Conditions Monitoring
Fig.2. Stationary condition diagnostics and monitoring system typically consists of a personal computer or a diagnostic station connected to signal commutation and conditioning blocks and then vibration and rotation speed sensors. The number of channels and measurement points in such a system may be from a few ones up to several hundreds.
Technical Inspection
Fig 3: Plant Technical Inspector using monitoring equipment
Practical
Inspections
Practical
inspections are those performed by maintenance personnel with many years of
field experience using less technical monitoring
equipment. Primarily, they apply their skills of looking at, listing to and
feeling of equipment on established daily routes to spot potential problems and
correct them. The practical ECM inspectors fill a very important void between
the technical inspection frequencies by monitoring every
piece of equipment daily and provide a constant flow of equipment daily and
provide flow of equipment conditions data.
Plant
Maintenance Program Development
Lubrication Program
The first and most important step in a
successful PM/ECM program is lubrication. Plant lubrication program will prevent
or solve approximately 60% of rotating equipment problems. Therefore, the
lubrication program must be initiated and implemented as designed by the
Lubrication Engineer.
Equipment Lists
Equipment lists are prepared from plant
Material Station Reports (MSRs). Preparation of the equipment list for the
PM/ECM program can vary depending upon the plant being a new facility, less
than one year old, or an older plant having operated more than one year.
Extreme care must be exercised to overloading the program with none PM/ECM
items such as statutory or
pre-turnaround inspections. To ensure optimum program effectiveness, equipment
list should be prepared using the following guidelines.
Equipment Lists for New Plants
v
Select
the top 20 pieces of equipment most critical to the continuity of plant
operations.
v
Select
the top 20 pieces of equipment that experiences has dictated will require the
most maintenance.
v
Select
the top 20 pieces of equipment that would result in the highest monetary loss
should they fail.
v
Then
progress down the MSR list selecting equipment, again as outlined above, for
the progress, considering frequencies, manpower a walked and remembering that
every piece of equipment will be walked by everyday by the practical
inspectors.
Equipment Lists for Old Plants
v
Select
the top 10 pieces of equipment most critical to continuity of plant operation.
v
Select
the top 10 pieces of equipment causing the most plant downtime or production
loss.
v
Then
progress down the MSR list selecting equipment, as outlined above, for the next
group of 10’s.
Equipment Classification
v
Each
piece of equipment is categorized or classified (pumps, motor, blowers,
compressors), and is assigned a service number, which indicates the type
equipment and its in-line process position.
v
Finalized
Equipment List should be reviewed and approved by the Maintenance Manager.
Inspection Frequencies
Using the finalized PM/ECM equipment
lists, frequencies for both the technical and practical inspections are
established. If equipment historical data is available, it is used to establish
the frequencies (how often individual pieces of equipment are looked at). If
historical data is not available (i.e., new plant) the frequencies are
established maintenance and maintenance engineering personnel with experience
and knowledge of similar plants and equipment. Frequencies will be set at
either daily, weekly, bi-weekly or monthly, depending upon the criticality of
the equipment. Care must be exercised to avoid overloading available manpower,
yet a full day’s activity should be planned for each inspection discipline.
Also, consideration must be given to the equipment cost, spares inventory,
installed spares and criticality to continuity of plant operation. Frequencies
should be reviewed annually.
Inspection Routes
Inspection routes are established by
actually walking through each unit, with the prepared equipment list and
established frequencies, formulating the routes to avoid excessive travel by
the Practical PM Inspectors, yet ensuring that all equipment is covered and
walked by each day. The routes must be plotted on equipment layout drawing in
order to train the inspectors. Inspection routes are not normally needed for
the Technical Inspections since these activities are usually confined to
certain pieces of critical equipment or dictated by request from the PM
Maintenance Supervisor.
Fig 5: Plants Inspection Routes
Inspection Schedules
Workable area PM schedule / check sheets
are prepared by calendar days based upon the number of pieces of equipment on each
route and their inspection frequencies. Schedules are prepared as a balanced
system to where the daily work load will be fairly consistent. The number of
schedules per area / unit can vary from one to as many as fifteen with each
schedule averaging four equipment list sheets.
Fig 6: Plant Maintenance Schedule
Inspection Calendar
PM calendars are designed into number of
periods with an open block under each day of the week. The schedule numbers are
entered in these blocks. The PM Inspector simply checks the day of the week and
the schedule numbers therein, pulls the appropriate schedule from the file
cabinet, providing that particular day’s inspection assignment. A calendar is
prepared for each process unit, depending upon the size of the plant.
Fig. 7: Equipment Maintenance Calendar
