DEVELOPING A MAINTENANCE VALUE STREAM MAP

DEVELOPING A MAINTENANCE VALUE STREAM MAP

Soundararajan Kannan
Yanzhen Li
Naveed Ahmed
Zeid El-Akkad
Department of Industrial and Information Engineering
The University of Tennessee,
Knoxville, TN 37996-2210


Abstract
availability. When equipment breaks down in a
As a result of increasing focus on lean
manufacturing cell, it shuts down the entire
manufacturing (henceforth referred as Lean) in
production line, until the equipment is brought
today’s competitive manufacturing environment,
back to its normal working condition. Hence high
maintenance management has found a new vigor
amount of non-value added time between
and purpose to increase equipment capacity and
machine stoppage and completion of repair,
capability. Tremendous efforts have been put into
compounds the production loss.
in developing different types of maintenance
Another dimension for streamlining maintenance
strategies for enhancing the performance of the
activities is the cost associated with downtime.
equipment but very little has been done in
The cost of maintenance downtime as stated by
actually streamlining maintenance activities. This
Cooper [16] is typically $500 per hour for a stand-
refers to systematically eliminating non-value
alone machine, $1,500 to $8,500 per hour for a
added activities from the maintenance function.
cell or line of machines, and up to $3,500 per
One of the primary lean manufacturing tools that
minute ($181,500 per hour) for an entire auto
can provide a different dimension in identifying
factory line. Further, the cost of downtime in lean
and analyzing non-value added activities is Value
manufacturing environment is five to thirty times
Stream Mapping (VSM). However, the traditional
more than other manufacturing environment as it
VSM cannot be utilized “as is” because the
directly and immediately results in lost
maintenance activities do not completely
opportunities [19]. Maintenance cost is directly
correspond with the VSM terminology. The
proportional to the downtime hours and hence
purpose of this paper is to develop a VSM
increase in the downtime hours due to non-value
specifically for maintenance to evaluate the non-
added maintenance activities can alarmingly
value added activities and provide
increase the maintenance costs.
recommendations to reduce the Mean
Thus, there is an immediate need for an
Maintenance Lead Time (MMLT).
approach that explicitly evaluates the

maintenance function to eliminate any
unnecessary time between machine stoppage
Problem Statement
and the completion of the repair function.
With the modern manufacturers trying to strive for

Lean in order to reduce inventory, production
Literature Review
lead time, direct labor, indirect labor, space
requirements, quality costs and material costs
One of the primary lean tools that was found in
[18], the emphasis on equipment availability has
the literature and has been effectively used in
become even more critical in order for the
evaluating non-value added activities is VSM. It is
manufacturers to successfully implement and
a tool that helps in visualizing a system by the
sustain Lean. One example is cellular
representation of information and material flow. It
manufacturing, a concept of lean, in which
also creates a common language about a
equipments are grouped together according to
process, by which purposeful decisions can be
the process sequence to form a cell. These cells
made to eliminate the non value adding activities.
are extremely efficient in achieving single piece
Seven different VSM tools namely, big picture
flow of product but at the same time extremely
mapping (Rother and Shook, 1999), supply chain
susceptible. The susceptibility is due to the fact
response matrix (Hines, Rich and Jones, 1997),
that cells are highly dependent on equipment
production variety funnel (New, 1974), quality

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filter mapping (Hines and Rich, 1997), demand
tool to measure the maintenance activities
amplification mapping (Hines and Taylor, 2000),
themselves. The delineation of MMLT is shown in
decision point analysis (Hines, Rich and Jones,
Figure 2
1997) and physical structure mapping (Hines and
MMLT is given by the following equation.
Rich, 1997) were reviewed; however none of
MMLT = MTTO +MTTR + MTTY
them directly correspond to the maintenance
Where,
operations and hence cannot be applied “as is”.
MTTO = Mean time to organize (Time required to
This clearly illustrates the uniqueness of this
coordinate tasks to initiate the maintenance
paper, wherein for the first time ever a value
repairs)
stream map is introduced specifically for
MTTR = Mean time to repair (Time required to
measuring maintenance operations.
repair and maintain of the equipment)

MTTY = Mean time to yield (Time required to
Methodology
yield a good part after maintenance)
A general methodology that will be utilized for
developing a Maintenance Value Stream Map
(MVSM) is shown in Figure 1. The methodology
is categorized into three distinct phases. The first
phase involves developing a framework for
MVSM. This framework will include all the
necessary symbols that will be employed for the
Figure 2: Delineation of MMLT
mapping process. The second phase involves

establishing a step by step standard mapping
Within the MMLT delineation, the only time
process by which maintenance practitioners in
component that adds value to the maintenance
industry could baseline maintenance activities
operations is MTTR, since this is the only time
and form a current state map of the maintenance
component that involves the actual performance
function. The third phase involves developing a
of the maintenance repair task. The other time
simulation model based on the current state map.
components MTTO and MTTY are non-value
The purpose of this simulation is to evaluate the
added time. Hence value added time and non-
non-value added activities and the efficiency of
value added time are given by,
the maintenance function by incorporating
Value added time = MTTR
variation associated with factors such as
Non-value added time = MTTO + MTTY
processing time and delay time
Maintenance Efficiency is calculated as the

percentage of MMLT that is actually spent on

repairing the equipment

% Maintenance efficiency = MTTR * 100





MMLT

Incorporating variation into MVSM

Profozich [20] stated, “You cannot use a static
Figure 1: Methodology
tool to study a dynamic problem. A static tool

gives an optimistic performance assessment. The
Metrics for measuring maintenance
greater the variability in the system, the greater
Analogous to the concept of lead time in
the error in static analysis.” The MVSM in
manufacturing, the concept of Mean Maintenance
essence presents a static picture of a system that
Lead Time (MMLT) is being suggested for
breaks the maintenance function into time values
maintenance measurement. MMLT is defined as
(like process time, delay time etc.). In the actual
“the time between recognizing the need for
scenario, all these time values are associated
maintenance on a particular piece of equipment
with some variation and as stated by Profozich
to the actual performance of such maintenance
[20], greater the variability associated with these
and the repair of the equipment”. [17] MMLT
time values, greater the error in static analysis.
takes the maintenance activities into account
Hence for the purpose of establishing a dynamic
from an operational level. Unlike the existing
evaluation by incorporating variation into MVSM,
indicators for measuring the maintenance
a simulation based approach is carried out in this
performance, it does not examine the impact of
paper.
poor or lack of maintenance strategy on the

manufacturing front; instead it acts as a powerful


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Framework
7. Timeline – The timeline presents two
In this first phase, a general framework is
categories of time. The first category is the value-
introduced for developing the MVSM. Within this
added time and it is typically associated with the
framework there are seven categories that are
processes. The second category is the non-value
utilized to represent the actual maintenance
added time and it is associated with both the
function. Specifically, these seven categories are
processes and delays in the system.
utilized to represent MTTO, MTTR, and MTTY as

presented in Table 1. Appropriate MVSM

symbols are provided for each of this category.

These are a combination of newly developed

symbols as well as symbols adopted from the

traditional VSM. The following are definitions of

each of the seven categories.

1. Equipment breakdown – This activity

represents the actual event of an equipment to

stop production due to maintenance

requirements.

2. Processes – These are actual activities that

occur from the time an equipment is stopped to

the time it is producing good products. In a typical

maintenance operation, there are eight different

processes. They are Communicate the problem,

Identify the Problem, Identify the resources,

Locate the resources, Generate work orders,

Repair equipment, Run the equipment and Finish

work order. Definitions for each of these

maintenance processes are provided in Table 1.

These activities represent a combination of both

value added and non-value added activities.

3. Physical flow -The physical flow sequence of

processes is critical to baseline the overall

maintenance process. In some case the

sequence of processes may illustrate

opportunities for improvement.

4. Information flow – The physical flow of

processes is dependent upon the flow

information to enable the physical flow. It is

sometimes the information that is the constraint

in the system.

5. Data Boxes – Associated with each process

there is a data box that provides information

regarding each process. This information is

critical in determining the opportunities for

improvement.

6. Delay – There is a possibility of delay between

any two processes. This delay is viewed as non

value added that increases the MMLT and

therefore the responsiveness to the customer. In

a typical maintenance function, there are three

different types of delay. They are Delay due to

unavailability of equipment operator, Delay due to

unavailability of tools and parts and Delay due to

unavailability of appropriate maintenance

personnel. Definitions for each of these delay
types are given in Table 1.
Table 1: MVSM Framework

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Figure 4: Step 2 of MVSM

Step 3 involves identifying the intermediate
processes between the first process
“communicate the problem” and the last process
Table 1: MVSM Framework
“Finish work order”.

Place all the intermediate process
Mapping Process
symbols namely, “Identify the problem”,
This phase describes the mapping process
“Identify the resources”, “Locate the
involved in developing the MVSM. The process is
resources”, “Generate work order”,
presented in the seven steps provided below:
“Repair equipment” and “Run the

equipment” right next to each other
Step 1 involves the following tasks associated
according to the process sequence as
with the equipment that has been shut down as
shown in Figure 5.
presented in Figure 3.

Draw the equipment breakdown symbol

for the equipment that has shut down.
Place this symbol at the top left hand
corner of the MVSM page
Write the equipment name at the top
rectangular box.

Figure 5: Step 3 of MVSM


Step 4 involves recording the information

associated with each maintenance process as

shown in Figure 6

Place the data box symbol underneath

each process.
Figure 3: Step 1 of MVSM
Calculate the process time for each

process. The variation associated with
Step 2 involves identifying the boundary of the
the process time can also be recorded.
process. Specifically this involves identifying the

Enter the value of the process time in the
first process after a machine is shut down and
data box. Arbitrary process time values
the last process when a first good part is
are assigned for the purpose of
produced.
illustration.
The first process is associated with
It should be noted that the finish work order
symbol “communicate the problem”.
process does not contribute to MMLT and hence

Place this symbol to the left hand side of
its process time is not included.
the page under the equipment

breakdown symbol.
Place the finish work order symbol to
extreme right hand side of the page such
that it is aligned with communicate the
problem symbol as shown in Figure 4



Figure 6: Step 4 of MVSM

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value added times at the bottom of the
Step 5 involves recording the delay time between
time line as shown in Figure 9.
maintenance processes.

Place the delay symbol between all the

processes.


Write the appropriate numbers inside the

delay symbol to indicate the type of delay.

If there are two or more types of delays

associated with a process, write all the

numbers corresponding to the delay type

separated by comma as shown in Figure


7.

Calculate the delay time. The variation

associated with the delay time can also

be recorded.
Figure 9: Step 7 of MVSM
Write the delay time below the delay

symbol. Arbitrary delay time values are
Simulation
assigned for the purpose of illustration.
This phase involves the use of computer software
to incorporate variation into the MVSM and
perform a dynamic evaluation of the maintenance
function. This will also provide user friendliness to
the model, wherein the user can input different
time values for all the delays and processes in
the MVSM. The simulation will then automatically
calculate MTTO, MTTR, MTTY, MMLT, non-
value added time, value added time and
Figure 7: Step 5 of MVSM
efficiency of the maintenance function.
Step 6 involves creating the physical flow and
A simulation model for MVSM was developed
information flow for maintenance processes.
using ARENA 8.0. The model receives input from

Connect the break down equipment with
the user as shown in Figure 10.
the first activity in the value stream using

the down arrow symbol.
Connect all the processes with physical
flow (dashed lines) and information flow
(continuous line) arrows as shown in
Figure 8

Figure 10: Simulation Input Screen
Figure 8: Step 6 of MVSM


The simulation inputs; number work orders per
Step 7 involves the following tasks associated
year and time between each work order
with developing the time line.
determines the number and the frequency of
Draw the time line at the bottom of the
simulation runs required to evaluate the
page.
maintenance function. The other simulation

Write down all the non-value added times
inputs are the MVSM parameters. Values for all
at the top of the time line and all the
the simulation inputs can either be an average
value or any type of distribution. Table 2 lists the

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various types of distribution and the format in
grain size of the powder. Various different grain
which it should be given as input to the model.
sizes of tungsten powder are blended in the
blender to get the appropriate mix of grain size.
The tungsten powder from the blender is then
sent to the lab (Inspection 2) for a final inspection
of the grain size. The inspected tungsten powder
is stored in drums for shipping. The bottleneck
process within this production process is the
furnace operation. Since the downtime of the
furnace will impact the production the most, it
was decided to develop a MVSM for the furnace.
Figure 12: Tungsten Powder Production Process
Table 2: List of Distribution


Using the seven step standard mapping process,
After getting all the inputs from the user, the
a MVSM for the furnace equipment was
simulation automatically evaluates the
developed as shown in Figure 13.
maintenance function in terms of MTTO, MTTR,

MTTY, MMLT, Non-value added time, Value
added time and % Maintenance Efficiency. After
performing all the evaluations, the simulation
displays the results as shown in Figure 11.

Figure 13: MVSM of Furnace

The simulation model was used to evaluate the
MVSM of furnace. The simulation inputs; number
Figure 11: Simulation Output Screen
work orders per year was found to be 36 to 83

and time between each work order was found to
be 1 to 36 days. Normal distribution was used for
Application
all the input values.
Tungsten powder production process as shown

in Figure 12 was used as a case study to
demonstrate the practical application of the
Results and Recommendation
proposed MVSM. The raw material used for the
The results obtained from the simulation model
powder production is tungsten oxide powder.
are shown in Figure 14. MMLT is 3012 minutes,
This powder is fed in to the furnace, which
MTTO is 2742 minutes, MTTR is 143 minutes,
converts tungsten oxide into tungsten. The
MTTR is 127 minutes, Non-value added time is
tungsten powder obtained from the furnace is
2869 minutes, Value added time is 143 minutes
sent to lab (Inspection 1) for determining the
and the Maintenance efficiency is 4.76%.

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Overall, the IE community now has a tool by
which they can effectively evaluate the
maintenance function; this in essence will provide
scope for reducing the areas of non-value added
activities within maintenance and thereby
enhancing the availability of the equipment and
the capacity of the manufacturing facility.

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Figure 14: Simulation Results
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12. Burbidge, J., "Automated production control
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1984.
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Industrial and Information Engineering at
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Soft Drinks Ltd, Lutterworth, 6-7 July 1995.
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system reliability. He has been actively
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25-26 January 1995.
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continuous improvement engineer at La-z-boy.
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been actively involved in sponsored research
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scheduling and lean office. He has been
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