APPLYING THE APPROACH
You must have a consolidated and up-to date asset register with full details for each plant or unit within the
manufacturing location before starting ACR. For a greenfield project, your
engineering/procurement/construction contractor should provide you with this list; it should include tag
numbers for all critical control valves, flow meters, transmitters, and electrical drives. For an operating plant,
you can extract the equipment master report from your ERP system. Asset criticality analysis should include
rotating equipment; static equipment; mobile equipment; pipelines; electrical assets like transformers and
switchgear; and process control assets, such as the distributed control system (DCS), instrumentation and
control valves.
Other necessary documents are process flow diagrams, equipment data sheets, etc.
Then, you should follow eight steps:
1. Establish a cross-functional team consisting of process, mechanical, electrical and instrument personnel
who have a thorough understanding of plant and equipment functions as well as constructional
features of assets. This team will brainstorm to assign each asset appropriate scores for a number of
key parameters.
2. Identify assets required for site safety. Label these assets as safety critical and put them into the
critical class (A). They must be operational 24/7. (A spare nearby or an assembly in a warehouse
don’t ensure uninterrupted protection.). Such assets typically include fire pumps, fire tender, fire alarm
system, flare stack systems, etc. If you have multiple fire tenders, all should be available in healthy
condition 24/7. You need not provide further details. Assign these assets a score of 40. (This is the
maximum, as detailed later.)
3. Similarly, automatically classify assets required for legal, environmental, and statutory compliance
as Class A. Such assets include analyzers on stacks for online monitoring of emissions, flow meters on
effluent discharge, the ambient air-monitoring system, etc. Give them a score of 40.
4. For each of the remaining assets, the cross-functional team must perform a more-detailed review of
its role in production, media handled, operating conditions and maintainability (see Table 1). The
team should review all documents and assign a score of 1 to 5, with 5 for most-severe, for each
parameter based on specific criteria. The criteria listed in Table 1 are only illustrative; the team
should alter them as appropriate.
5. Add the scores of all parameters from Table 1. The maximum score for any asset is 40 (8×5). The
cross-functional team must decide the boundary lines for categorizing assets into Class A, B and C.
In Table 2, assets scoring 25–40 are Class A, those scoring 12–24 are B, and ones scoring below 12
are C.
6. Populate the equipment master with the rankings and scores against each characteristic as shown in
Table 2. Put all auxiliaries or child assets into the same class as the parent equipment. So, for instance,
if you categorize a centrifugal compressor as Class A, also automatically classify auxiliaries such as
its drive motor or steam turbine, lube oil and auxiliary pumps, etc., as Class A because the objective
is to make the entire system reliable.
7. After completing classification, review the count of Class A, B and C assets within a plant area and
perform any finetuning required. (Unlike the A, B and C classification of inventory where you can
apply Pareto’s Principle to demarcate between the classes, in ACR most assets will go into Classes A
and B with only about 10–20% in Class C.) The team then should sign off on the ACR; it should be
treated as a controlled document and circulated per the distribution list. All process, maintenance,
and reliability engineers as well as planners and schedulers should get a copy.
