A PM Audit is Not a Preventive Maintenance Effectiveness Audit

A PM Audit does not Improve Your PM Program—Doing a PM Effectiveness Audit is far more Useful than Conducting a PM Audit when a PM Program Does not Stop equipment breakdowns

A Preventive Maintenance Audit will check what your PM program contains. But it will not check if your PM program is effective.

To check PM program effectiveness requires you to look at the impact your PM program is having on the maintenance costs and productivity of your assets.

It’s important that you know the difference between a PM Audit and a PM Effectiveness Audit.


Many managers hope that by doing a PM Audit they will get the insights they need to fix their PM program. You might be lucky, but if you want to fix your PM program it’s better to do a PM Effectiveness Audit than a PM Audit.

The reply to the question asked below will help you understand the difference between a PM Audit and a Preventive Maintenance Effectiveness Audit.



Just read your article on Preventive Maintenance Effectiveness and it is great! Maintenance Effectiveness Audit Process.

Do you have a sample audit sheet template that has been used to audit PM’s on equipment?

If so, I’d love to see one. Thanks.



Hello Jason,

One thing you need to be aware of is, a Preventive Maintenance (PM) Audit is not the same as a PM Effectiveness Audit. A PM Audit implies that you review your PM program. But your request is about auditing individual equipment items. To audit the usefulness and coverage of your equipment PM’s, you could develop a Reliability Checklist to audit each asset. Here is a sample PDF Mechanical Equipment Reliability Checklist, and a sample PDF Mobile Equipment Reliability Checklist.

Preventive Maintenance effectiveness has two aspects. One is whether each Preventive Maintenance activity eliminates the possibility of equipment breakdowns. The second is how much your entire PM program contributes to operational success, e.g. operating profit, workplace safety, plant uptime, etc.

Situations that benefit from Preventive Maintenance include where parts will:

  • over-stress, (like fasteners, parts suffering high bending, torsion or shear forces, etc.)
  • be contaminated during operation (like oil filters, fuel filters, air filters, etc.)
  • wear-out (like brake pads, pump impellers and volutes, mechanical seals, etc.)
  • degrade from “time aging” (like rubber parts, V-seals, O-rings, etc.)
  • degrade because of service conditions (they suffer high temperatures, they suffer abrasion or erosion, etc.)
  • fatigue from accumulated stress in their microstructures (like moving parts, vibrated components, parts under impact loads, etc.)
  • collect dirt, rubbish, dust, etc. that will cause damage if not cleaned away in time

What is Preventive Maintenance? What is a Preventive Maintenance Audit? What is Preventive Maintenance Effectiveness?

American National Standards Institute (ANSI) defines Preventive Maintenance as, “the planned maintenance of plant infrastructure and equipment with the goal of improving equipment life by preventing excess depreciation and impairment. This maintenance includes, but is not limited to, adjustments, cleaning, lubrication, repairs, replacements, and the extension of equipment life.”

The definition of audit, from ‘ISO 19011 Guidelines for quality and/or environmental management systems audits’ is, “systematic, independent and documented process for obtaining audit evidence, and evaluating it objectively to determine the extent that the audit criteria are fulfilled.” Audit criteria is defined as, “set of policies, procedures or requirements.”

In the online Oxford Dictionary, effectiveness is defined as, “the degree to which something is successful in producing a desired result; success.”

Doing a Preventive Maintenance Audit

In a Preventive Maintenance Audit, you start with the set of Preventive Maintenance policies, procedures and requirements specified by the company. Then you obtain evidence from the audited workplace of how well their practices meet the prescribed policies, procedures and requirements. A Preventive Maintenance Audit does not necessarily measure Preventive Maintenance Effectiveness, i.e. the extent of success of Preventive Maintenance in delivering its intended business purpose.

In a PM audit, you check that the PM program delivers all the requirements that the organization stipulates must be done to its plant and equipment. You can have an ineffective preventive maintenance program, but if you use and follow its procedures you will successfully pass a PM audit, even though your plant and equipment are unreliable.

Start a PM Audit by gathering together the organization’s Maintenance Management Policy, the equipment maintenance strategy, any preventive maintenance policy, the PM process, all PM process procedures and requirements—requirements include the PM activities noted in PM work orders. That is the first audit check—to find out if there is predetermined PM strategy targeted to minimized operating risk in a specified and documented PM program. If there is no formal risk removing PM strategy for each equipment item, then both the PM program that is in use (there is always a PM program. Even if no PM work orders exist, that is the PM program), and the entire Maintenance Management philosophy behind it, are deficient of sound risk management logic.

The PM audit reviews if the PM philosophy, program, and work done in the operation keep the assets reliable. You develop a tabulated checklist of the issues and requirements to be inspected and confirmed as being in practice. For a randomly selected, statistically correct sample size of equipment in the PM program, you go and check if their service life history contains all the intended preventive maintenance requirements on your list.

In an operation with 3,000 equipment items in the PM program, the sample size is proportionately smaller than an operation with 300 equipment items in their PM program. To have a high confidence that the sample size reflects the whole population in a PM program for 3,000 separate equipment items, you need to check the service history of 150 pieces of equipment (5%). In a population of 300, you would need to check 100 individual equipment items (33%). A PM Audit that is not statistically correct in its sampling is rubbish, and its recommendations should not be believed.

Doing a Preventive Maintenance Effectiveness Audit

A Preventive Maintenance Effectiveness Audit reviews the PM program in terms of its chance of successfully “improving equipment life by preventing excess depreciation and impairment.” You review a range of PM work orders to gauge if they are truly preventing component failures and sustaining the plant and equipment in “as good as new” condition. Second, it looks at the contribution of the whole PM program to the success of the operation.

During a PM Effectiveness Audit, you look at a representative sample of the work orders used by each discipline—mechanical, electrical, instrumentation and control. It requires a random sample size of PM work orders large enough to give a fair “snap-shot” of the situation. The sample size must be statistically correct and you’ll need to calculate how many work orders to grab randomly from each discipline’s PM work order population to be confident your sample reflects the truth.

For the PM work order samples, compile the following details.

  • Master PM Number,
  • Master PM Title,
  • Identification number of the equipment that undergoes the PM,
  • Site name for the equipment,
  • The operating criticality of the equipment, i.e. the highest operating risk the organization carries because of having the equipment,
  • Whether the equipment has a standby, or other redundancy option, to cover a breakdown—a redundancy will substantially reduce operating criticality,
  • The range of maintenance strategies used on the equipment, i.e. Run to Failure, Condition Monitoring, Preventive Maintenance, etc.
  • PM frequency of occurrence,
  • Type of PM, i.e. component inspection, renew (replace with new), refurbish (restore a working component to ‘as good as new’), overhaul (strip and rebuild to replace worn components)
  • Work tasks to be done during the PM,
  • List of all components, by part number and description, replaced during each equipment PM work order (includes oil and other fluid changes),
  • Person(s) responsible to do each PM task, i.e. mechanical maintainer, electrical maintainer, instrumentation and control maintainer, equipment operator, external specialist contractor, etc.

For each item of equipment covered by the sample PM work orders, compile the following information.

  • The entire parts lists and all parts drawings, and the equipment assembly drawings,
  • All PM work orders done on each equipment asset during its service life, complete with all work order history,
  • All Corrective work orders done on each equipment asset during its service life, complete with all the order work history,
  • All Breakdown/emergency work orders done on each equipment during its service life, complete with all the order work history,
  • Full costs of each work order type, PM, Corrective, and Breakdown—parts, labour, outside services, overheads—done on each equipment during its service life,
  • List of all components, by part number and description, replaced in each equipment during its service life, for PM, Corrective, and Breakdown work orders,
  • Dates on which components, by part number and description, were replaced in each equipment,
  • Operator log notes about unacceptable behaviour of the equipment during its service life,
  • Maintenance workshop shift log notes about the equipment during its service life.

Checking Preventive Maintenance Program Effectiveness

One way to check the effectiveness of the PM program is to plot work order timelines. On a standard timescale, mark when each PM work order was done for an asset. On a separate timeline, mark when each corrective work order was done. On a third timeline, plot when the breakdown work orders occurred. Aline all the timelines for an equipment asset one under the other and look for “the story.”

Do the PM work orders clearly extend the time between breakdowns, or do breakdowns happen randomly? Are corrective work orders raised from the PM activities, or are corrective work orders random?

An operation with an effective PM program would have no breakdown work orders other than for the specified components approved to fail on a Run-to-Failure maintenance strategy. In the ideal PM program, corrective work orders ought to only arise from PM activities and not be generated at any other time.

You can also timeline when part numbers were replaced in an item of equipment to look for the story it tells about PM program effectiveness.

Another check on PM effectiveness is to look at the contents of the tasks on the PM work orders done to each equipment asset. For an item of equipment, are all the components in the parts list that can fail addressed in a Master PM work order? Are all PM tasks matched to component failure prevention, or to renewal before breakdown? Are the PM tasks appropriate to prevent the component’s failure from the expected, the likely, and the possible failure modes? Are PM work order frequencies set to the correct schedule to eliminate all breakdowns from preventable failures?

Benefits of a Preventive Maintenance Program Ought Be Obvious and Huge

A PM program ought to prevent all unpermitted breakdowns. The cost of every breakdown is an unnecessary expense incurred by the operation. Tally the direct maintenance costs of all unwanted breakdowns during the equipment service life—parts, labour, outside services, overheads—and multiply the total by ten. That is the extra operating profit the company could have made from the equipment if there was an effective preventive maintenance program.

A truly insightful PM Effectiveness Audit will tell you a visionary story about the business benefits to be gained by creating a highly effective preventive maintenance program.

Mike Sondalini
Lifetime Reliability Solutions