Integrated Machinery Management
James W. Taylor
LAFAYETTE INDUSTRIAL TRAINING
Abstract: This paper proposes a holistic,
integrated approach to machinery management. Such a program
is comprised of four major elements. There must be a systematic
planned maintenance system for routine maintenance and
condition assessment. A system must be in place to insure
needed spares are available without carrying excessive
inventory. Most importantly, a measurement system must
collect necessary data and present it to management in
such a way that they understand their problems and what
action to take. Once good measurements are available, there
must be a continuous improvement system to make the maintenance
function more effective, the equipment more reliable and
efficient, the work performed more professional and less
expensive, while minimizing spares inventory carrying costs.
Key Words: Continuous improvement; integrated
maintenance; machinery management; predictive maintenance;
preventive maintenance; reliability engineering; spares
management
INTRODUCTION:
Manufacturing today is becoming increasingly competitive.
Production processes have been squeezed for the last pound
per hour, for one more component per shift. The production
equipment itself is one of the few remaining areas in plant
operation where significant gains can be made. To maintain
your manufacturing leadership, you must move from a defensive
strategy of maintaining the status quo to a proactive,
aggressive plan to improve plant reliability and capacity.
You must manage the production assets in a systematic and
professional way.
Much attention has been given lately to the use of modern
condition monitoring techniques such as vibration analysis
and oil analysis. Many claims, most of them true to some
extent, have been made for their ability to spot failure
s before they happen. Though these methods are powerful,
it's important to remember that they must be used as part
of an overall system of maintenance. Without a complete
program, only minimal , short term benefit will be gained
from condition monitoring.
The most progressive, competitive manufacturing organizations
see management of production assets as a potential strategic
advantage. They are developing integrated machinery management
programs that pull all the separate technologies and management
techniques together in a way that allows them to understand
where the problems are and how important they are. Knowing
that, they can make plans to solve those problems permanently.
Until you know what the problems are, any action taken
will at best result in short term solutions. In the worst
case it may make the problem worse.
I want to remind you of some of the other types of information
that we should consider. (see Figure 1 ) Each piece is
important on its own. Each area has its own techniques
and tools, both hardware and software. The real advantages
come from the synergy that results from combining this
information.
Machinery i nformation comes from many sources. A machinery
information management system (MIMS) often consists of
several parts. For purposes of this discussion, the major
ones are:
• Planned maintenance system (PMS)
• Spares management system (SMS)
• Production system (PS)
• History collection system (HCS)
• Continuous improvement system (CIS) (Reliability
Engineering)
There must be a systematic Planned Maintenance System
for routine maintenance and condition assessment. A Spares
Management System insures needed spares are available without
carrying excessive inventory. Accurate history on maintenance
expenditures and experience is essential to identify the
most troublesome problems. But most importantly, to achieve
the potential production improvements and reductions in
cost per unit, all the information available to plant management,
including history, must be used . This is the
Measurement System. Once good measurements are available,
the Continuous Improvement System guides you in making
the planned maintenance function more effective, the equipment
more reliable and efficient, the work performed more professional
and less expensive, and in minimizing spares inventory
carrying costs.
The difficult part of maintenance management is to balance
the maintenance expenses and needs, while minimizing overall
costs. But these gains are not free. An objective of self-
assessment of your maintenance processes may be to identify
opportunities to improve equipment performance or reduce
maintenance costs. However, these improvements cannot be
accomplished without some investment in manpower or improved
technology.
Done correctly, costs may go up but sales revenue and
gross profit will go up faster. The payoff from putting
in place an integrated machinery management program is
longer Mean Time Between Failure (MTBF), shorter Mean Time
To Repair (MTTR) and shorter Mean Logistics Delay Time
(MLDT). Those factors mean higher reliability and availability.
This pays off in higher product throughput and lower operating
expenses.
The MIMS is a system in the true sense. As can be seen
in Figure 2 Machinery Information Management System .,
i t has inputs and outputs. And it has feedback. They are:
Inputs:
• Maintenance actions on the machine
• Spare parts actions
• Engineering / design change actions
• Machine operation
Outputs:
• Routine and adhoc reports
• Program improvement objectives
• Machine improvement objectives
• Personnel improvement objectives
Feedback:
• Continuous improvement system
PLANNED MAINTENANCE SYSTEM:
All work is planned! If it is not pre-planned, then it
is planned during execution. Pre-planning insures needed
parts, materials and skills are available. Multiple trips
to the tool room or store room are eliminated. Crafts are
coordinated, avoiding wasted manpower caused by people
standing around waiting. Work planned during execution
suffers from false starts, missing parts or information
and wasted manpower. Work that is not pre-planned can cost
you as much as 25 times more to accomplish.
A good planned maintenance system is designed with an
optimal mix of preventive (PM) and predictive (PdM) maintenance
tasks. As much corrective maintenance as possible is planned
to make best use of manpower and spares. The number of
unplanned repairs is minimized. A good planned maintenance
system will reduce the number of emergency repairs to a
minimum because many of the failures that would be emergencies
are found early while doing PM or PdM tasks. Because they
are found before the failure occurs, they can be repaired
with the least impact on production.
Preventive (Time Directed) Maintenance :
FACT: Equipment that is operated can fail, and not all
failures can be prevented. Preventive maintenance forms
the backbone of a planned maintenance system. PM tasks
are either fault finding (inspection) or preventive replacement.
The routine of time directed tasks fosters discipline and
focus in the maintenance organization. A well designed
program has a standard daily and weekly routine that encourages
systematic planning and performance of maintenance tasks.
Predictive (Condition Directed) Maintenance:
A good planned maintenance system has a heavy emphasis
on condition directed tasks, often called predictive maintenance.
Periodic monitoring of equipment condition will optimize
use of manpower, consumables and spares because work on
the machine is only done when it's needed. Both installed
production instrumentation and special technologies are
used to monitor and trend equipment condition. Some of
the most common technologies are vibration analysis, oil
analysis, motor analysis and infrared scanning.
Planned Corrective maintenance:
Corrective maintenance must be accomplished in the most
cost effective manner possible. Because equipment problems
are detected sooner by PM and PdM tasks, corrective action
can be planned. Planned repairs result in much lower maintenance
costs. Labor costs are lower because the crafts people
start the job with all the parts and tools they need. Overtime
can be reduced or eliminated. Spares costs will be lower
because they don't have to be ordered on a crises basis,
with the resulting high freight fees and expediting costs.
And lost production cost will be lower because the repair
is done during a scheduled shutdown.
Even if a special shutdown has to be scheduled for the
repair, it will be shorter because all parts, tools and
people can be in place before production is stopped. The
work will proceed more efficiently because the crafts know
what they will be doing. Lost product or off quality product
is minimized because production is shut down in an orderly
manner rather than by a casualty. And because the line
is shut down in an orderly manner, secondary, cascading
failures are avoided.
Even emergency work can be planned. Some emergencies can
be anticipated. For these, a pre-planned work order can
be on file ready to go. For repairs that are not anticipated,
the savings resulting from a conscious, formal planning
step can still be significant. Planning will minimize trips
to the tool and store room. It can ensure all needed parts
are ordered the first time, and that the correct crafts
and tools are on hand.
Most CMMS systems collect general work and performance
data. The various condition monitoring technologies have
their own, often proprietary, supporting software. Each
technology has pieces of information that are unique to
it. Each of these pieces of information are important and
must be captured.
SPARES MANAGEMENT (SM) SYSTEM:
Spare parts are kept on hand so repairs can be made in
the quickest time possible. But do you know what spare
parts you have on hand? Do you know what parts you should have
on hand? A good SM program has a spares allowance list
(SAL) for each piece of critical equipment. The SAL differs
from a Bill of Materials because it lists all the parts
that should be kept in the store room to repair that machine.
The lists for the individual machines are combined into
a consolidated list for the whole facility. Consolidation
accounts for duplicate usage of some of the parts, resulting
in lower total parts inventory.
SM also provides for systematic storage, inventory control
and issue of spares. As a part is issued, it is charged
to the proper job order and machine. This assigns the cost
of the part to the cost of maintaining the machine and
is information needed to assess the usage of the part.
Knowledge of usage lets you update the allowance lists
as the equipment ages and conditions change. A periodic
audit of spares will identify parts no longer needed or
additions to the allowance because of increased usage.
You will be able to adjust order points and minimum levels
to insure parts are available when needed.
The Spares Management System generates several kinds of
useful information. Parts should be designated as to usage
and inventory management method. There can be non-stock,
usage stock, insurance stock and project stock to keep
track of , each with its own management method . Storeroom
management needs information on location, layout, stock
catalogs, and issue/receipt. There are also other spares
management actions that generate information. Spares are
ordered, unused parts are turned in, kits are built for
specific jobs, bills of material and allowance lists for
each machine must be maintained. And the whole system must
be updated as a result of engineering change orders that
affect the machinery.
PRODUCTION:
Production generates a number of pieces of information
that can be useful to maintenance and engineering. In addition
to operating temperatures, pressures, speeds and other
data, the planned and actual production times and run times
are important. Records of change-over, bottle-necks, product
produced and operating problems provide needed information
to assess program effectiveness and machine improvement.
MEASUREMENT SYSTEM:
One of the difficulties in the maintenance field is objectively
judging the actions of those involved. The large machines
in major industrial installations are inherently reliable
and their natural rate of deterioration is very low. A
manager can spend very little money over a period of several
years without experiencing a marked decrease in availability.
He often appears to do a better job than a manager who
applies a more comprehensive approach. In the latter case,
corresponding expenses are visible , and have an immediate
negative impact on the budget. Because machinery information
is so hard to gather and present consistently, senior management
does not recognize the resulting aging and deterioration
until too late.
A measurement system is like the control panel of an aircraft.
It tells you where you are and what the conditions you
are operating in are like. Your measurements should accurately
represent the current conditions. Comparing measurements
from period to period, looking for trends, will tell you
where you are headed. By collecting the right data and
displaying it properly, the beneficial impact of maintenance
can be quantified in a way that is understood and believed
by upper management.
The basic requirement for good measurements is good records.
A common complaint of crafts people is that they are paid
to work on the machinery, not to do paperwork. At first
glance this seems to be true. But the paper work involved
in history collection is a vital part of understanding
the equipment. The cost of the time spent filling out good
history reports will be more than offset by the long term
savings in improved maintenance and reliability. Good records
let you know what the most expensive machines are, what
the most common failure modes are, what parts to keep on
hand, what machines need more or less PM or PdM. Accurate
detailed history gives you the information you need to
do root cause analyses of failures and fix the real problem
so it doesn't reoccur. Another advantage of detailed descriptions
is that they can act as a planning tool if the casualty
occurs again. Good records also provide you the data needed
to develop and justify your budgets. It gives you a management
tool to target budget cuts to the areas where they will
be most effective.
The history collection system must gather at least three
types of information. Statistical information must be captured
for overall analysis of the maintenance function. This
includes such data as man-hours expended, parts used, consumables
used. It must also capture production downtime and maintenance
downtime. The information contained in detailed narrative
descriptions of problems and actions taken is needed for
root cause analysis. It should include how the problem
was discovered, what the symptoms were, trouble shooting
steps taken, repair procedures used and any special problems.
Accounting information ? costs, badge numbers, wage rates,
special shipping costs, etc. ? is needed by plant management
to develop and administer budgets. It also is captured
as part of the life cycle cost of the machine.
Once the history is captured, it must be used. Serious
analysis of maintenance should :
• take into consideration indirect maintenance
costs (costs of reduced or lost production) .
• Judge the evolution of economic indicators
over a prolonged period.
• Evaluate the evolution of the equipment condition
over the same period.
The raw data must be manipulated to find the information
that's in it. MTBF, MTTR and MLDT are calculated. Costs
are summarized. Effects of varying production utilization
are accounted for. The resulting measurements should be
a true picture of the current situation.
CONTINUOUS IMPROVEMENT PLAN:
The Continuous Improvement System is where it all comes
together. In this system, the history collected is used
to identify areas where maintenance can be made easier
and cheaper. Unneeded maintenance or additional needed
maintenance is identified. Additional training requirements,
changes in logistics requirements and potential equipment
redesign or modification are other results of analysis
of the history. The review should not be limited to large,
costly or politically visible failures. Clusters of failures
should be sought out. Often several minor failures can
cost as much or more than one large failure. Looking for
clusters of failures and eliminating their cause will pay
for itself quickly.
A Maintenance Reduction System consists of several separate
but related parts. They are:
• Planned Maintenance Optimization
• Precision Maintenance
• Maintainability Improvement
• Equipment Improvement
• Logistics Improvement
• New Equipment Selection
Planned Maintenance Optimization:
Plant design characteristics can create a performance
limit for the plant, no matter how effective the maintenance
is. However, it is also true that improper, inadequate
, or too much maintenance can adversely affect performance.
Over-maintenance increases direct and indirect maintenance
costs by increasing voluntary production losses, speeding
aging due to excess dismantling a and re - assembly, and
increasing the risks of damage through human error . Given
these limitations, how do you establish the optimal maintenance
program.?
Planned Maintenance Optimization is a formal program to
review the effectiveness of the Planned Maintenance System.
Using data from the measurement system, reliability information
can be derived. The review of this information will
identify those machines with too much or too little PM
or PdM. It will assess the effectiveness of the planned
tasks and recommend added tasks if needed .
Finally, this review will tell management where they should
apply more expensive techniques such as Reliability Centered
Maintenance, condition monitoring, machine modification
and others. It can identify needed training and tools.
Precision Maintenance:
Precision maintenance denotes a high level of skill and
training of the crafts. Such things as use of standard
procedures for bearing replacement, correct preparation
of foundations before setting equipment to prevent soft
foot, and using vibration to verify correct installation
are examples. It also encompasses using tighter tolerances
than is normal. When balancing, take the little extra time
to make an extra run - it will pay off in increased bearing
life. Precision alignment to increase seal life, strict
cleanliness to avoid later problems because of dirt, and
extra care in seating surface preparation are other examples.
Analysis of the history will show where the training dollars
should be spent.
Maintainability Improvement:
Maintenance tasks should be reviewed to determine those
that take a long time to do or that require large manpower
expenditure. These tasks should be investigated to see
if there are changes that can be made to make the task
more economical. These might be procedures changes, special
tools or jigs, or modifications to the machine. All of
these improve the maintainability of the machine. Better
maintainability means the machine is cheaper and safer
to maintain and less problems are introduced while doing
maintenance.
An example might be a task requiring periodic checking
of gear tooth wear on a gear set. Because of equipment
design, the job takes three men (two mechanics and an electrician)
4 hours, a total of 12 man-hours. They have to remove an
interfering motor and rig a cover plate off the casing.
By installing an access plate in the gear casing, the job
can be done by one man in 30 minutes.
Equipment Improvement:
A history of frequent failures of a machine might lead
to a design change to eliminate the problem. For example,
review of the history reveals that maintenance is called
several times a week to un-jam product on the conveyer
feeding the wrapper. The product is getting cocked, and
following product shoves it into the rollers. Engineering
redesigns the guides to prevent the cocking, eliminating
the problem. The increased production and reduction in
off quality product more than pay for the modification.
Logistics Improvement:
The spares usage should frequently be reviewed to assess
the adequacy of the SAL's. Parts may no longer be needed
because of changes to the equipment, stocking levels may
need to be adjusted because of usage, additional parts
may need to be added to the SAL. History can help identify
parts that should be vendor stocked, vendors who are not
responsive either in timeliness or quality of parts, and
parts that have a high failure rate and should be substituted.
Incidences of not having the proper tools, drawing or manuals
will also be identified by history review. Correction of
these problems will reduce the delay before the repair
can start (MLDT), which means less lost production and
more sales dollars.
New Equipment Selection:
The best plants will monitor the life cycle costs of their
equipment. As your equipment ages, there may come a time
when it is more effective to replace it with new than it
is to continue to repair it. A recent study by Eastman
Chemical Company showed that maintenance costs can be as
high as 50% to 75% of total life cycle costs. A good machinery
history will give you the information needed to make an
overhaul / buy decision.
SUMMARY:
As we work towards an open system for machinery information
management, we need to think of all the aspects of machinery
information. Because a majority of our members are from
the condition monitoring field or from large user organizations,
there is a danger that we may become too narrowly focused.
While big companies have enough people and resources to
put together large projects to integrate the various sources
of machinery information, most companies don't. There are
350,000 manufacturing plants in the USA , but only 35,000
have more than 100 employees. It is those 315,000 who most
need our help.
One screen access to all required information will be a major
step towards giving management the tools needed to intelligently
set policy and improve their operation. By identifying problem
areas and suggesting solutions the MIMS can start the process
of continuous improvement. By collecting all pertinent information
consistently, it provides a measurement system that tells
management if they are on course or
RR 1, Box 105 ? Clarks Hill , IN 47930-9728
Phone (765) 324-2302 ? FAX (208) 445-1213
|
