Download Can RCM and Streamlined RCM peacefully co

Can RCM and Streamlined RCM peacefully
co-exist?
Extracted from Chapter 14 of Reliability-centered Knowledge
By Murray Wiseman
Optimal Maintenance Decisions (OMDEC) Inc.
www.omdec.com
Introduction
Religious or political zealots confront one another, often, not on
the basis of the mores of their respective doctrines, but rather from
superficial differences in the details surrounding each other’s cultural
reference points. Mathematicians take pride in their ability to adopt a
new set of definitions and symbols as effortlessly as they would don a
fresh suit of clothes. Thus they proceed, unfettered by prior points of
view, to build new theorems upon old. The world of maintenance has,
not dissimilarly, spawned a multitude of cultures and languages for
formulating solutions to real problems.
In the preceding chapters we conducted RCM on several diverse item
types. We systematically answered each of the seven RCM questions
about the item, and, in the order stipulated by the SAE JA-1011
standard: 1) functions?, 2) failures?, 3) failure modes?, 4) failure
effects?, 5) consequences?, 6) scheduled tasks?, and 7) default
tasks?. We entered the answers to the questions in an electronic
spreadsheet (for example, MS Excel or a database form) formatted as
the RCM Worksheet illustrated in Figure 11-2 on page 138.
This chapter explores one of several streamlined RCM software
programs. We begin with an examination of what is meant by
“streamlining”. We illustrate the streamlined approach by describing a
popular representative RCM software package called RCM Turbo1. We
set up a cross-reference “dictionary” of terms describing similar
sounding but, sometimes, differently applied concepts in the two
“languages”. Finally we summarize the relative advantages and
potential drawbacks of the “streamlined” RCM and the RCM processes.
Through this process, we discover how the juxtaposition of two
approaches may enlighten the proponents of both.
1
Available from Strategic Corporate Assessment Systems, www.strategicorp.com.
Why streamline RCM?
Chapter 11(page 137) cited the SAE Standard “Evaluation Criteria for
Reliability-Centered Maintenance (RCM) Processes” that defines RCM
as:
“… a specific process used to identify the policies which must be
implemented to manage the failure modes which could cause the
functional failure of any physical asset in a given operating context.”
It goes on, to define the process by adding:
“…Any RCM process shall ensure that all the following seven questions
are answered
satisfactorily and are answered in the sequence shown as follows:
a. What are the functions and associated desired standards of
performance of the asset in its present operating context
(functions)?
b. In what ways can it fail to fulfill its functions (functional
failures)?
c. What causes each functional failure (failure modes)?
d. What happens when each failure occurs (failure effects)?
e. In what way does each failure matter (failure consequences)?
f. What should be done to predict or prevent each failure
(proactive tasks and task intervals)
g. What should be done if a suitable proactive task cannot be
found
(default actions)?”
Were we to consider the process (of answering the 7 RCM
questions in the sequence stipulated) unacceptably resource intensive,
then, understandably, we would seek to replace it with a process that
consumes less time and fewer resources, but by one that provides, no
less a responsible (sufficiently rigorous) analysis. We emphasize that
the JA 1011 SAE standard stipulates a minimal set of criteria for a
process to be called “RCM”. Therefore, it is to be expected that most
commercially packaged RCM software systems and methodologies will
add a considerable number of features that will enhance and facilitate
the experience.
The original2 as well as the various streamlined RCM methods all
demand that the assembled team of analysts (operational, process,
and maintenance specialists) possess, collectively, the knowledge
necessary to make informed decisions regarding the maintenance
characteristics of the item under scrutiny. The process chosen (either
original or streamlined) must, therefore, encourage the maximum
contribution by each participant so that RCM decisions will carry the
force of all knowledge and experience available on the team. The
success of any “RCM” methodology, therefore, depends heavily on its
ability to gain true consensus, throughout every stage of the
analysis. The group, guided by a well trained facilitator, exercises its
best judgment when visualizing the typical worst case scenario
(TWCS) surrounding each functional failure analyzed.
With these objectives in mind, we compare the two processes, by
presenting a comparative lexicon of some of their respective terms of
reference.
RCM/RCM Turbo dictionary
Table 14-1 Relationship between RCM and RCM Turbo terminology
RCM
Item: a collection of parts, or systems
that is convenient to analyze as a group.
It has been selected at a high enough
level of indenture that its failure may
easily be related to that of the
equipment as a whole, but at a low
enough level so that the analysis is of
manageable size (i.e. having a
manageable number of failure modes).
No equivalent terminology is specified by
the RCM minimum criteria standard. (Any
convenient or existing equipment
hierarchy naming system may be used.)
Operating context is often recorded in a
flexible text structure at the top of the
RCM worksheet.
Worksheet: A document (conveniently
an electronic spreadsheet or simple
database application) onto which the
answers to the 7 RCM questions are
RCM Turbo
Maintainable item (MI): same
meaning
Productive unit (PU): A system that
includes several maintainable items. A
convenient place to record the operating
context of the MI. A productive unit
belongs to a “Major Unit” and a “Plant” is
the highest level in the Turbo RCM
hierarchy.
The RCM Turbo software product is not
meant to be populated during the
sessions, but afterwards by the facilitator
or other person trained in the use of the
“Original” is meant here to refer to processes that conform closely to the RCM process developed by
Nowlan and Heap as described in their 1978 report Reliability-centered Maintenance. Processes that
conform to RCM as originally defined include: Ministry of Defence (UK) Defence Standard 02-45 Issue 2
CATEGORY 2 (NES 45 Issue 3 July 2000), John Moubray”Reliability-centered Maintenance”, MSG3.2002
Air Transport Association, Washington DC., NAVAIR 00-25-403., and others.
2
recorded during the RCM team session.
The RCM minimum criteria standard does
not specify a criticality or priority scale
with which to schedule the order of items
to be analyzed. Nowlan and Heap
developed a simple priority system for
the aviation industry that has only two
criticality ratings: 1)significant item3, and
2) non-significant item. This classification
system has proved useful in a variety of
other industries. For structurally
significant items (SSI) Nowlan and Heap
apply a further classification of one to
four for each of the five categories:
1)Residual strength after failure, 2)
Fatigue life, 3) Crack growth, 4)
Corrosion, and 5) Accidental damage.
The minimum class (for all 5) determines
task frequency. There are two categories
of SSI: 1) Damage-tolerant and 2) Safelife. Classifications 1 to 5 apply to
damage-tolerant items, but only
classifications 4 and 5 apply to safe-life
items. (See Example 4 of Chapter 13 on
page 178).
Failure: Describes the way in which a
specified function no longer performs as
required. It distinguishes (for example)
“full” from “partial” failure of a function.
The RCM Worksheet enforces a one-tomany integrity constraint between
Function and Failure.
Failure Mode: A reasonably likely cause
of a specified failure. Consists of a noun,
a verb (active or passive form) and a
phrase such as “due to …”. For example
“bolt cracks due to stress corrosion
fatigue”. The number of failure modes to
list and their “depth of causality” depend
on operating context. RCM enforces a
one-to-many integrity constraint
between failure and failure mode. RCM
Turbo does not.
Failure Mode: In RCM, the terms “Root
Cause”, “Failure Mode”, “Failure
3
software. A MS Excel form (Figure 14-2)
is provided for use during the sessions.
Criticality/Priority: values used to set
priorities for PUs and MIs. It is derived by
question and answer sessions driven by
the program. (Criticality calculations in
no way detract from RCM. They merely
add another dimension to the analysis.)
Failure: same basic definition. However
Turbo-RCM does not constrain a one-tomany (software) relationship between
Function and Failure.
Failure Mode: A superset of the RCM
definition. Structured in 3 parts as
follows:
1) a component reference, 2) a
“Failure Mode & Effect” field - a single
field that includes both RCM concepts
(Failure Mode and Failure Effects), and 3)
a “Root cause” reference. An example
of a RCM Turbo failure mode is:
“Bearings” + “wear between rolling
elements and racers leading to increased
vibration levels, localized heating and
eventual seizure and total stoppage of
process due to” + “normal wear and
tear”.
Root cause: related to Failure Mode.
Same definition. That is, “Root Cause” in
One whose failure has hidden, safety, environmental, or serious economic consequences.
Mechanism”, “Failure Reason”, etc are
synonymous and represented by the
term “Failure Mode”. It is an “event” in
the causality chain that leads to the
failed state. The “link” in the causality
chain selected as the “Failure Mode” is
the one that the organization can
manage effectively and practically by
whichever means (proactive, detective,
or redesign).
Failure Effects: Text answering the
following:
• what sequence of events (considering a
TWCS4 in the component, in the system,
organization wide, and in the external
world) could be touched off by the failure
mode?
• how does the failure make itself
known? What observable events lead up
to the failure?
• how is safety or the environment
impacted? (without mentioning the words
"safety" or "environment")
• how is production impacted? (quality,
cost, customer service)
• is there any additional damage caused
by the failure?
• how long will it take and what actions
must be accomplished to correct the
failure?
• How does the likelihood of this failure
depend on deeper causes? Has it
happened before? How often? Under
what circumstances?
Turbo RCM is equivalent to “Failure
Mode” in RCM.
Hidden Function: A Function whose
failure will not be detected under normal
circumstances. Identified by RCM during
functional analysis when examining each
component (from schematics, p&ids,
photographs, and physical walkaround)
and listing the functions they suggest.
Code phrases (such as “able to”, “in the
presence of”, etc) are used to point out
that a function is hidden or protected by
a hidden function. Subsequent questions
address the hidden function. The
“hidden” consequence supplants the
other (three) failure consequences in the
Hidden Failure Mode: Same meaning
as RCM’s “hidden function”. It is
structured in the fields: Component,
Failure Mode & Effects, Task Description,
Frequency, Duration, Initiate Date, Job
Group ID, Service Period, No. of Units in
Service, No. of failures, and MTBF of the
protective device (calculated).
4
Same definition but it is structurally
embedded in the “Failure Mode &
Effect” field. In addition the following
“Failure Mode” fields (with sample data)
contribute to the “Effects” narrative:
Unit Output Reduction: Total
stoppage,
PU Downtime Cost: $11,390 / hour,
MI Downtime Cost: $11,390 / hour
F/mode&Effects: Shaft failureChemical corrosion, overtorque, indicated
by cracks, increase in vibration leading to
shutdown of Brownstock washer
Characteristic: Definitive life / wear out
characteristics
Measurability: Moderately easy to
monitor
Category: Normal Operation
Typical Warn Time: 4 Weeks
Root cause: Normal wear & tear
MTBF: 5 years
Consequence: Total stoppage
Strategy: CBM
Typical worst case scenario. A collective judgement that balances the extent of detail recorded with the
gravity and likelihood of the failure consequences.
RCM logic for determining a mitigating
task.
RCM records this information in the free
text answer to question 4, “Failure
Effects”. However the JA1011 standard
does not specify an explicit data field or
structure for MTBF.
RCM records this information in the
answer to question 6 and 7 “Tasks” when
following one of the four branches (H, S,
O, N) in the RCM decision logic tree.
Same definition. RCM records this
information in the free text answer to
question 4, “Failure effects”.
Potential failure: An indicator that a
failure mode has initiated.
No equivalent concept in RCM. If a failure
mode is due to design, lubrication,
overload, or maintenance practices, they
would each constitute a separate failure
mode, and this information would be
included in the failure mode description
itself. The word “Safety” or
“Environment” is not mentioned until the
consequence phase of the RCM logic
diagram.
RCM records this information in the free
text answer to question 4, “Failure
effects”. However no explicit data
structure is specified by the JA1011
standard.
Consequences: Question 5. Takes one
of four possible values: 1) Hidden, 2)
Safety /Environmental, 3) Operational,
and 4)Non-operational.
RCM records RCM Turbo’s “Consequence”
in the free text answer to question 4
“Failure effects”.
RCM records this information both in the
free text answer to Question 4 “Failure
effects” and in the answer to Question 6
“Tasks”. Q6 asks whether there is an
applicable CBM task. Once a (CBM or
other) task is found to be applicable
(practical) RCM then asks whether it will
be effective. That is, will it sufficiently
reduce or entirely avoid the
consequences of failure at acceptable
cost?
Redesign: RCM records this information
MTBF: related to the Failure Mode.
Strategy: related to Failure Mode. Takes
one of three possible values: 1) fixed
time maintenance, 2) condition based
maintenance, or 3) operate to failure
P-F Interval: related to Failure Mode.
Estimated interval (measured in working
age units) between the appearance of a
potential failure and a functional failure.
S/A (secondary action) Indicator:
same meaning as “Potential failure” in
RCM.
Category: related to Failure Mode. Takes
one of six possible values: 1) Design, 2)
Lubrication, 3) Normal Operation, 4)
Overload Condition, 5) Maintenance
practices, or 6) Safety
Characteristic: related to Failure Mode.
Takes one of three possible values: 1)
Definitive life/wearout, 2) General
degradation, and 3) Random
Consequence: related to Failure Mode.
Takes one of four possible values: 1)
Total stoppage, 2) Partial
stoppage/quality, 3) No immediate
effect, or 4) No effect. This information
Measurability: related to Failure Mode.
Takes one of three possible values: 1)
Easy, 2) Moderate, or 3) Impossible
Design Notes: related to the Failure
in the free text answer to question 7,
“Default Tasks”. Differs from RCM Turbo
only in the sequence in which this
question appears (i.e. following a
determination that no proactive or failure
finding task adequately mitigate the
consequences of the failure.)
RCM provides no specific field for this
information, leaving its provision up to
the implementer or commercial
packager.
RCM records this information in the free
text answer to question 4, “Failure
Effects”. However, without an explicitly
specified structure.
RCM develops this information in the
decision algorithm of question 5 (Is there
an on-condition maintenance task that is
both applicable and effective?) The RCM
standard does not elaborate an explicitly
specified structure for recording this
information.
RCM records this information in the free
text answer to question 6, “Tasks”. The
RCM standard does not elaborate an
explicitly specified structure for recording
this information.
RCM records this information in the free
text answer to question 4, “Failure
Effects”. The RCM standard does not
elaborate an explicitly specified structure
for recording this information.
Not called a “library”. However, the
records are accessible (structured as
answers to the seven questions) in the
RCM worksheets comprising the global
RCM table. No corporate harmonizing
process need be applied because every
Mode. Records decision/recommendation
to “design-out” the failure mode. (strictly
speaking it is presented out of “RCM
sequence”.)
Strategy Notes: related to Failure
Mode. A free text field used to store
comments or notes on the chosen
maintenance strategy. Useful where a
second or alternative strategy has been
considered and rejected.
Breakdown Action: related to Failure
Mode. Describes what must be done to
repair the functional failure. Also has the
specific fields: Work Order No., SOP,
Duration, Downtime, MI Status, S/A
Initiator, Resources (up to six steps),
Assumptions, Materials, Spares.
Primary Action: Related to the Failure
mode. Describes what should be done to
prevent the failure mode. Also has the
specific fields: Work Order No., SOP,
Duration, Downtime, MI Status, S/A
Initiator, Resources (up to six steps),
Assumptions, Materials, Spares.
Secondary Action: related to Failure
Mode. Describes what must be done
following the detection of a potential
failure. Also has the specific fields: Work
Order No., SOP, Duration, Downtime,
MI Status, S/A Initiator, Resources
(up to six steps), Assumptions,
Materials, Spares.
Overhaul Action: related to Failure
Mode. Records Overhaul Maintenance
actions. For example, where the
Secondary Action was the change-out of
a rotable item which itself requires
subsequent overhaul. Also has the
specific fields: Work Order No., SOP,
Duration, Downtime, MI Status, O/H
Venue, S/A Initiator, Resources (for
up to six steps), Assumptions,
Materials, Spares.
Failure Data Library: a table of “3 part”
failure modes referenced by Machine
Type. An administration process is used
to control the quality of data from
multiple sites and harmonize it for the
purpose of providing “templates” where
record is a “one-off” development.
However, tools, training, supervision and
support are required to validate and
maintain and update the knowledge base
with day-to-day experience. “Templating”
of an entire item, is, nonetheless,
possible by copying any or all records of
an item after carefully comparing their
respective operating context
descriptions.
applicable in future analyses of other MIs
or PUs. The focus on “templating”
justifies the appellation “Streamlined” in
the case of RCM Turbo.
We may conclude from Table 14-1, that, although RCM Turbo refers to
itself as a streamlined process, and, that some of its terminology
differs from that of RCM, it does not omit any vital knowledge element
specified by the SAE RCM minimum criteria standard. RCM Turbo does
deviate from the sequence stipulated in the standard. As pointed out
in Chapter 11 (page 137), in practice, however, RCM is not a
sequential process. RCM analysts anticipate the answers to
subsequent questions while working the current question.
Furthermore, the RCM process is iterative. That is, the analysts often
return to a previous answer and adjust it in the light of revelations
further on in the process. The iterative and non-sequential nature of
the RCM process tends to render less important the differences
between the two approaches.
The terminology comparisons of Table 14-1 show that RCM Turbo
expands the information elements of RCM into greater structural
detail. Such data structuring facilitates the post-RCM processes
(included in the RCM Turbo software package) of workload smoothing,
frequency calculations, and CMMS integration as well as integration
with a spares optimization (optional) package.
Figure 14-1 of Example 1 shows how the RCM Worksheet of Chapter
11 (Figure 11-2 page 138) might be combined with the extended data
fields of RCM Turbo.
Example 1
PU Code: Repulper, MI Code: Repulper screw
Consequences Task Interval By
and Results of
Decision
Algorithm
Q5, Q6, Q7
Function Failure Failure Effects
Statement
mode
Q1
Q2
Q4
Q3
To feed
Does Shaft Unit Output
material 24 not
fails
Reduction: Total
hours/day feed at
stoppage,
all
PU Downtime Cost:
$11,390 / hour,
MI Downtime Cost:
$11,390 / hour
F/mode&Effects:
Shaft failure-Chemical
corrosion, overtorque,
indicated by cracks,
increase in vibration
leading to shutdown
of Brownstock washer
Characteristic:
Definitive life / wear
out characteristics
Measurability:
Moderately easy to
monitor
Category: Normal
Operation
Typical Warn Time:
4 Weeks
Root cause: Normal
wear & tear
MTBF: 5 years
Consequence: Total
stoppage
Strategy: CBM
Figure 14-1 RCM Worksheet applied to a RCM Turbo example
In the RCM worksheet of Figure 14-1 we note that most of the RCM
Turbo “failure mode” fields (in bold) fall quite readily into the RCM
Effects column, with the possible exception of the field “Strategy”. The
latter appears to pre-empt the RCM decision logic of Questions 6 and
7. We view this, nonetheless, as an insignificant departure (from
RCM), given that RCM analysts consider the mitigating task in the
normal course describing the effects of failure. It is essential,
however, that the RCM consequences (H, S, O, or M) be determined
and the meticulous decision logic of RCM (on page 171) be applied
immediately following this RCM Turbo step.
RCM Turbo facilitates data entry with a convenient Visual Basic MS
Excel form illustrated in Figure 14-2.
Figure 14-2 MS Excel failure mode entry form in RCM Turbo
RCM Turbo then will perform a “primary” (i.e. a CBM) task frequency
calculation (Figure 14-3) and display the results that 14 days (i.e. half
the PF interval) is the recommended task frequency. RCM Turbo
calculates the annualized cost of the CBM program so that it may be
justified by comparison with the annualized economic consequences
(based on the MTBF and the average cost of a failure) avoided by the
CBM program.
Figure 14-3 CBM Frequency and Cost optimizing calculation
For scheduled overhaul, discard, and failure finding tasks RCM Turbo
performs analogous calculations by applying a recorded MTBF, a
qualitatively estimated hazard function, and the recorded average
economic consequences of failure. The complete set of RCM Turbo’s
data fields is given in Appendix 12 on page 236.
Conclusions
1. Table 14-1 illustrates that streamlined RCM (as it is embodied in
RCM Turbo), is not “streamlined” (i.e. in the sense of being
“abridged” or “reduced”). Rather, it encompasses the principles of
RCM, adding features that address CMMS integration, quantitative
reliability assessment and task frequency calculations, spares,
workload scheduling and balancing, and other considerations.
2. RCM Turbo does address the 7 RCM questions, however, not in the
sequence stipulated by the RCM Standard. The software expands
the 7 information elements of RCM into various database fields. For
example, MTBF, P-F Interval, and Repair time are explicit fields
related to a Failure Mode.
3. A RCM Worksheet based on the SAE JA1011 standard, will provide
excellent team focus regardless of the software adopted. If
populated (perhaps adapted as in Figure 14-1) with RCM Turbo's
needs in mind, the worksheet (incorporating the RCM decision
algorithm) will benefit both streamlined and original RCM users.
4. Both RCM and RCM Turbo demand that the persons (primarily
maintainers and operators), directly impacted by maintenance
decisions, participate fully in the process. Indeed they must drive it.
External consultants can only teach the principles and techniques of
RCM. Regardless of the RCM software chosen, the organization
must select its analysts from among its most experienced and
competent operators and maintainers. It must chose a facilitator,
from within, who will learn the RCM process fluently, elicit, and
faithfully record the technical knowledge of the analysts. The
facilitator must ask the 7 RCM questions and ensure that consensus
has been reached. He or she must ask and ensure that each of the
questions along the appropriate branch of the RCM decision tree are
rigorously answered by the team, and duly recorded.
5. Finally, we emphasize that reliability-centered maintenance is not a
software dominated process. Software records the results of RCM
analysis in a convenient, accessible, and auditable format that
traces every maintenance task back to a failure mode that the RCM
team identified. Software enables integration with the CMMS and
implementation therein of the RCM analysis results. As importantly,
software, through regular feedback from the field, and integration
with the CMMS, supports continuous “living” enhancement of the
initial RCM analysis.
Do you have any comments on this article? If so send them to [email protected].
References:
1. RCM Turbo Maintenance Plan Development System Quick Reference
Guide
2. RCM Turbo V9.2 User Guide
3. RCM Turbo V9 desktop guide rev 2
4. RCMT92 Installation Instructions