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.

Kiriman : Administrator

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 summarised 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 criticalty 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.