Planned maintenance is the purposeful rejuvenation of equipment before parts
start failing.
Planned maintenance is the purposeful rejuvenation of equipment before parts
start failing. It is a maintenance strategy based on continual renewal so
that you always have plant and equipment that are in good condition and hence
free of age related defects.

Abstract :

A Planned Maintenance Procedure Based on Equipment Criticality. This article
takes you through the factors which you need to consider and perform when
developing a planned maintenance strategy. If you are spending the majority
of your maintenance effort in reactive tasks then your maintenance costs
are high. If you can spend the majority of your maintenance effort doing
planned maintenance activities you will lower your maintenance costs and
have more reliable production plant.

The approach relies on identifying equipment criticality based on the impact
that equipment failure has on production. The failure modes that cause breakdowns
are identified and the necessary planned maintenance to address the failures
are specified. The required frequency to perform the planned maintenance
activity is set so that it is done before a failure occurs.

Keyword:  planned maintenance, reactive maintenance, proactive maintenance,
equipment criticality,

Start of Article

Objective:

a.   To reduce the maintenance costs in the plant to industry standard
percentage of replacement asset value.

b.   To reduce breakdown maintenance costs below 10% of total maintenance
cost for the plant by conducting planned maintenance activities that renew
plant and equipment before failure occurs.

Methodology:

The method to achieve the above objectives are summarized in the following
steps;

It is first necessary to check what proportion of maintenance effort is being
used on reactive work fixing things verses pro-active work that stops them
from breaking in the first place. You want to be spending most of the maintenance
time doing proactive work. It is also necessary to identify what proportion
of maintenance effort is being used on not doing maintenance related work.

Review the last two years history of maintenance work and separate into four
categories of Proactive, Reactive, Improvement and Assistance work. Compile
costs and man-hours per category to determine proportions of cost and effort
spent for each.

Proactive includes preventative maintenance, predictive maintenance, condition
monitoring, statutory maintenance, etc. Reactive includes breakdown maintenance,
corrective maintenance, emergency maintenance, safety or incident related
maintenance, etc. Improvement includes equipment or process modifications.
Assistance is maintenance resources used in capital projects, plant upgrades,
production requirements, etc.

Collate full plant equipment list from plant drawings, process drawings and
equipment asset lists.  Be sure to capture all equipment in operation
as it will later be necessary to go to component and sub-sub-component levels
of analysis, and maybe further.
Using the equipment listing create a spreadsheet showing all the equipment
used in each part of the production process.  Logically divide the production
process into definable sections of the process.  Under each section
list each item of equipment in process use order.
Layout the spreadsheet so that in column 1 you list the process section,
column 2 the equipment it contains, column 3 the individual equipment’s components,
column 4 the sub-components, column 5 the sub-sub-components.

It is necessary to identify the impact of losing each item of equipment on
production.  This is done by conducting a criticality assessment of
the plant and the equipment used in each part of the production process.

Start by meeting with experienced Operations people to determine the failure
impact on production for each item of equipment.  Rate the impact of
the individual equipment on the process sections using a 5-point scale. 
1 is immediate and total impact. 2 is delayed total impact.  3 is reduced
or hindered operation.  4 is inconvenience to operation.  5 is
no impact.

Work your way through all the plant deciding how the equipment impacts on
the process should it fail.

On the same spreadsheet used in the Operations criticality review extend
it to include all the equipment assemblies and sub-components under the respective
equipment.  List down to the lowest sub-assembly or component in the
equipment for which you are willing to store as a spare part.
Meet with experienced maintenance personnel and rate the criticality of assemblies
and components in each item of equipment using the same criteria as previous. 
For each item of equipment record the spare parts considered critical to
have to keep the equipment operating.

To get a numerical criticality rating see the spreadsheet below. Basically
you sum the ratings and divide by the number of time an item is rated. If
the rating is between 1 and 1.33 it is highly critical and you should consider
stocking critical spares. It will require condition monitoring and preventative
maintenance. If between 1.4 and 1.67 it is moderately important and a preventative
maintenance strategy is required. If above 1.67 it is of lesser importance
and a mix of preventative and breakdown maintenance would be considered.