The answer to these questions
is this simple fact to understand that any asset is put into service because
someone wants it to do something. It follows that what we wish to preserve must
be the state in which the user wants the asset to perform – so is the function
of the asset.
A function of an asset
defines that the asset is operating as per user requirement, and this
definition is not wholesome unless it specifies as precisely as possible the
level of performance desired by the user – a minimum performance standard that
cannot surpass the built-in capability of the asset. As no maintenance program
can go beyond that point.
So, the role of an asset in
business is always defined by the user - what the user wants from an asset is
the actual function rather than what the asset’s inherent capacity is – this
emphasis provides a whole new objective of the maintenance process which is
known as RCM (Reliability Centered Maintenance).
RCM stands for Reliability
Centered Maintenance is a modern most effective maintenance program of an asset
that focuses on the user requirement and expectations from the assets – a
process used to determine what must be done to ensure that the installed asset
continues to do whatever its users want it to do in its present operating
context.
Defining Function
The function statement should consist of a verb, an object, and a desired standard of performance.
for example: To pump water from tank X to Tank Y at not less than 800 liters per minute.
Types of Functions
Typically, each asset has more than one function and all of them must be identified together with their current desired standards of performance if we wish to ensure that the asset continues to fulfill these functions. Functions are divided into two categories:
Primary functions:
Primary functions of any asset are those reasons the asset is acquired, it can be one, two, or three reasons – the main reasons why the asset exists at all. This category of functions covers issues such as speed, output, storage capacity, product quality, and customer service.
For example, the primary function of the packaging machine is to pack things.
If
assets have more than one primary function then all of them should be listed in
the functional specification. Each primary function will have a separate
maintenance program. These are called multiple independent primary functions.
There is another function we call it serial function in which an asset can also
have two or more primary functions in series – where 2nd function works after
the first function fulfills its requirement.
Secondary Functions:
Most assets are expected to
fulfill one or more functions in addition to their primary functions. These are
known as secondary functions. Secondary functions can’t be overlooked as the
loss of a secondary function can still have a serious consequence so they must
be clearly identified so that their maintenance can be properly done as
frequently as the primary function.
Secondary
functions that users expect to fulfill from each asset other than primary
functions are:
Environmental Integrity: Environmental Integrity is conformity in fulfilling official environmental requirements. It is the adherence to all environmental regulatory requirements that apply to your organization’s activities, services, and products. Compliance with the environmental regulations may not be the primary function of the asset but it’s the critical secondary function and the ethical and moral obligation as well to protect the environment and prevent harm to the environment. Authorities tend to sanction more seriously those companies that over time have shown themselves indifferent to compliance with environmental regulations.
Safety: Although safety is not a primary function of an asset it’s the crucial one. The asset should be safe and hazard-free, should not pose any threat to human life, and have a necessary obligation to fulfill safety standards in order to avoid unforeseen incidents or fatality.
Safety
hazards are must to address before installing an asset. However, it’s best if
all safety concerns or hazards are identified during the initial phase of
designing by writing clear functional statements which deal with specific
threats to safety.
If
any chance, processes, or components are failed to fulfill the safety expectations
then this will add the additional feature in the form of a protective function.
Structural integrity: Structural integrity is supporting some other functions or components. House walls are one example of structural integrity where the prime purpose may be to protect people and equipment from the weather, but it also supports the roof.
Control: The user not only wants the asset to fulfill the functions to a given standard performance but also wants to regulate and record the performance as per their need. Functions like getting the real-time information about the process and their assimilation though come under secondary functions but their requirement in the new era of maintaining modern assets is no less than primary functions.
Comfort: Ease is another thing people want from the asset. Nobody likes anxiety, pain, and discomfort. This function should be addressed in the design phase, however, deterioration of the asset can cause this function to fail like any other. To avoid such a situation is to ensure the functional specifications are appropriately defined.
Appearance: Function that mostly gets the last spot to discuss but its importance is not to be ignored because it supports other vital secondary functions such as appearance may take part in enhancing visibility and minimizing safety risk. it gives comfort to the eyes and exudes fresh vibes.
Economy & Efficiency:
Run-to-failure
maintenance is one example where analysts work on the cost of replacement vs
cost of maintenance and chose the RTF maintenance type on basis of cost-benefit
analysis.
Another
example to understand is that a car consumes 6 liters of fuel per 100km at a
constant speed of 120km/h and the same car consumes 4 liters of fuel per 100km
at a constant speed of 60km/h.
By
looking at the second example it’s concluded that at the operating context
level, functional expectations concerning costs have a major say in the limited
financial resources. Economic issues can be addressed directly by function
statements that define what the user expects in the area such as fuel economy
and loss of process material.
Containment: For assets whose primary functions are to store or transfer things, containment is an important secondary function. This includes pipes, pumps, conveyors, gearboxes, transformers, etc. in case of containment functional statements of an asset should be very clear about the performance standards to maintain – a minimum requirement and the containment procedure.
Performance Standards:
Performance Standards are a benchmark – those documents that lay the foundation for the expected performance of the equipment to behave within. A set requirement that constitutes that asset continues to perform to the extent to which the user wishes it to do something without deteriorating.
Performance
can be defined in two ways:
1-
Desired performance – what the user wants to asset to do.
2-
Initial capability – the maximum capacity of the asset to perform.
Performance
can be further divided into two measures:
Quantitative
Performance Standard:
Performance
standards are quantitative if the description of the asset’s functionality is
precisely defined and are tangible quantities. Quantitative performance
standards are of utmost importance when we talk about asset management and
Maintenance and reliability as it provides an adequate basis – a target to
obtain in maintenance and thus is the objective of maintenance.
A
functional statement of the asset should contain a clear and precise
performance requirement to meet, for instance, To transport up to 5 people along made roads at
speed up to 140km/h have
performance expectations related to speed and number of passengers. Statements
like “to produce as many samples as required” and “to go as fast as possible”
are meaningless statements in terms of maintenance and reliability as they make
it impossible to define exactly when the item failed and to what extent.
Qualitative Performance Standard:
Sometimes
performance of the function cannot be specified so the only chance is to settle
with the qualitative statement. Qualitative functional statements are difficult
to comprehend as it involves intangible requirements and makes it a challenging
job for maintainers to achieve the level of acceptance.
If
there is no chance of avoiding qualitative statements, then the user and
maintainer need to share a common understanding of what is the minimum
acceptable limit of function to preserve.
Sometimes
we do come across those functional statements that say nothing about
performance standards or the level of acceptability to meet, such statements
are said to have absolute performance standards.
Such
as the statement “to contain liquid” lacks the information about the type of
liquid and has no performance standard at all then any leakage at any amount
will be considered a functional failure.
Concluding
with a brief explanation of the importance of operating context in the
operation and maintenance world because what the users want from the asset
always depends on the surrounding environment – where and how the asset is
being performed. The operating context also profoundly influences the
requirements for secondary functions whether it be environment, safety,
redundancy, regulations, etc. It is also to be noted that the effects of
operating context hit drastically on the functions and performance standards.
So, careful consideration should be paid while defining maintenance strategies
of the asset.
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