Dale R.Blann

Principal/CEO

Marshall Institute Inc.

dblann@marshallinstitute.com

USA

Why is it that (almost) everyone carries out PM (Preventive Maintenance), but that only few are satisfied with how their PMs are being carried out?
If you ask most maintenance people how they feel about their Preventive Maintenance (PM) practices, they will frequently (very frequently) express some form of disappointment with them. Mechanics often feel that their PMs are poorly designed at best, generally not executed well (when done at all), and often totally unnecessary (adding no value, whatever) at worst.

Production operators have their own problems with current PM practices, too; they often consider them to have no value at all, and will often complain that PM causes them more problems than it solves (in the form of startup delays, yield loss, quality deviations, etc.).

What’s happening here?

One of the problems in many instances is that maintenance is not perceived as a “value-added” contributor to desirable ends, such as output, quality, productivity, safety, and environmental security.
In many companies, maintenance practices are somewhat informal, not well-organized, and not based on “best practice” approaches. Systems of work control are either inadequate or not present at all. Breakdowns are frequent and the majority of maintenance activity is reactive. In the pressure of time, maintenance may be subjected to a “quick fix” mentality, a “bandaiding” approach that actually exacerbates the situation.

In addition, other problems may be present:

• There is not a consistency of policy, or philosophy for the programme
• There is no consistency of analysis; symptoms are addressed (over and over), rather than causes being resolved or eliminated
• PMs are often redundant, unnecessary, or inadequate, having little or no meritorious effect on the asset
• The desire to be risk-averse results in some procedures which actually over-service equipment, and/or use overhaul or intrusive maintenance processes, often to the detriment of equipment reliability
• There is a lack of systematic process in execution; PM procedures are not well defined, lack detail, or are not followed with consistency in method of execution, standards of judgment, or frequency of execution
• There is no audit trail; it is impossible to objectively review the programme for benefits or effectiveness
• Etc….

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Figure 1. Finding the Right Strategy.

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Figure 2. PM Optimization for Existing Tasks.

It has been our experience that in many PM programmes:

• Many PM tasks duplicate other tasks
• Some PMs are done too often
• Some PMs are done too late
• Some PMs serve no purpose whatsoever
• Some obvious and effective tasks are not in the system at all
• Many tasks are too intrusive in their own right; many would be more effective and less costly if they were condition-based
• Even some condition-based tasks are overly intrusive, or cause too many stoppages for production, and can be reduced in frequency, based on failure data (that is usually not being gathered)
• Modern diagnostic tools and technologies offer unrealized opportunities for effective and efficient tasks not now being performed.

In other words, the PM programme is costing too much, producing too little benefit.

If that is the case in your plant, you have a prime opportunity to make a positive contribution to your company in this current, very difficult, economic environment. If your current PM practices suffer from those deficiencies, you may find the potential exists for

• Moving 20–40 % of your PMs to condition-based criteria (PdM)
• Eliminating many PMs that are not adding value (sometimes as many as 30 % of PMs are worthless!)
• Improving the effectiveness or extending the frequencies of those PMs that are useful
• Adding PM/PdM routines that address current failures not covered by any strategy whatsoever.

The fact is that maintenance costs can almost always be reduced with increased effectiveness and better results (performance) simultaneously. There are a lot of ways maintenance can reduce costs. We can improve the work order system, implement better information management (CMMS), and initiate formal planning & scheduling. These initiatives produce significant long-term gains, but they often take a significant investment of time and money, too. Improving your PM programme is another matter; it’s not difficult and the benefits can be achieved in short order.  

Finding the Right Strategy

A good preventive maintenance programme will incorporate a variety of types of preventive maintenance. The actual types and mix of maintenance will vary from plant to plant, depending on plant’s specific equipment, performance needs, safety or environmental requirements and consequences of failure. Some of those types are shown in Figure 1:

• Routine inspections, lubrications, cleaning, and adjustments
• Routine replacements or rebuilding
• Predictive maintenance (technologies using measurement of physical conditions)
• Condition based maintenance (continuous monitoring of physical conditions)
• Failure Finding tasks The challenge is to select an appropriate mix of types, while producing the required performance at reasonable and justifiable costs.

What is PM Optimization?

PM Optimization is a structured process, which uses the principles of Reliability Centred Maintenance (RCM) to review and optimize existing preventive, predictive, and autonomous maintenance activities procedures on existing equipment, using existing failure history. Thus it is not a zero-based analysis, such as in pure RCM, but a practicable and economical alternative to it (Figure 2).
The heart of the PMO process is a workshop that provides for input from the following typical participants, as required: 

• Facilitator – Acts as PM Optimization facilitator & participates in PM Optimization process.
• Craft(s) – Provides feedback on execution of current PM tasks and experience with failure modes & history.
• Operator(s) – Provides feedback on execution of current PM tasks and experience with failure modes & history.
• Others – to provide insight into failure history, failure modes, and potential maintenance activities.

How Does PM Optimization Work?

PMO increases the effectiveness of the existing reliability strategy by:

• Optimizing the current predictive or preventive maintenance procedures by making sure the right procedures are being done by the right people at the right frequency
• Addressing failures not addressed by the current maintenance and reliability strategy
• Managing (reducing) the consequence associated with failure
• Selecting more effective (nonmaintenance) alternative strategies when appropriate. PMO increases the efficiency of the existing reliability strategy by:
• Making sure that the consequences of, or losses associated with, certain failures warrant the cost of doing something versus nothing
• Eliminating strategies and procedures that add little or no value
• Writing tasks and procedures clearly, applicable to the equipment to which they are being applied
• Assigning tasks and procedures to the right resources
• Writing tasks and procedures so that they can be accomplished efficiently, without waste of time, money or effort.

The Basic Process

Typically a PMO workshop involve 4–6 people, meeting over one to three days, so organizing one is not a trivial undertaking, but it’s not complicated, either. It’s an iterative process: get the current data, identify the known and probable failure modes, and ask the same series of questions for each, over and over. Then implement your recommendations. (Figure 3)
 

The basic questions being asked in a PM Optimization Workshop are:

1. What maintenance tasks are currently being undertaken by the operations and maintenance personnel? What OEM equipment information exists (has it been used appropriately)? What is the experience of the incumbent maintenance and operations personnel? What actual failure data is available?
2. What are the failure modes associated with the equipment PMs being examined (failure modes analysis)?
   1. What is (are) the failure mode(s) that each existing task is meant to prevent or detect?
   2. What other failure modes have occurred in the past that have not been listed or have not occurred and could give rise to a hazardous situation?
3. What happens when each failure occurs? (Failure effects) 
4.  In what way does each failure matter? Establish consequences of each failure mode: hidden or evident; hazard, operational, or repair only. (Failure consequences)
5. What should be done to predict or prevent each failure (proactive tasks and task intervals)? Revise/add/delete maintenance tasks based on failure data, Craft/ Operator input, and Reliability- Centred Maintenance logic (see Figure 4).Remove low- or non-value-added maintenance tasks. Determine if there is a task that will predict or prevent each failure mode from occurring - this may be an existing task or possibly a new task. Predictive (condition monitoring) tasks are typically preferred. Each maintenance task must be feasible and worthwhile.

• Feasible = reasonably capable of predicting, preventing, or eliminating the targeted failure mode.
• Worthwhile = prediction, prevention, or reduction of the failure mode justifies the cost of the maintenance task. 

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Figure 3. PM Optimization Process.

 6. What should be done if a suitable proactive task cannot be found (default actions) or the current tasks cannot be improved (accept consequences; no scheduled maintenance)?

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Figure 4. RCM/PMO Logic for Evident Failure Modes.

Do It Now!

Take a good hard look at your current PM practices and procedures right now. If your PM programme doesn’t measure up, you have a gold mine ready to be mined for short-term gains in downtime reduction, production improvement, and increased maintenance productivity, through the application of PM Optimization, based on fundamental RCM logic.

Remember, Maintenance is a contributor to be optimized, not just a cost to be minimized. That's because maintenance is not (strictly) a cost. Maintenance may be on the expense side of the ledger, but it can't be treated like office supplies.

When done right, maintenance is a contributor of capacity, thru-put, safety/environmental integrity, quality and scheduling agility – all things manufacturing plants need more of, not less.