Definition Preventive Maintenance vs. Predictive Maintenance - Distinction between

[darkafar]

Case description:
One manufacturer designates 22 machines as key equipments needing planned maintenance. This company has daily, weekly, monthly and yearly planned maintenance. When asked, their maintenance director said, “We have a very good maintenance system. In the past two years the equipments have never been down by accident.” When asked for relevant data, he said that because the equipments hadn’t been down they had no data.

A senior auditor suggested this company violated TS2 clause 7.5.1.4, saying they didn’t have a predicative maintenance system.

I found I disagree with him, because I think the daily, weekly, monthly and yearly maintenance can be counted as both preventive maintenance and predicative maintenance. I think I might be a little confused with the distinction preventive maintenance and predicative maintenance. May someone help to explain the difference between the two kinds of maintenance?

 

[Govind]

Re: distinction between preventive maintenance and predicative maintenance

Case description:
..... I think I might be a little confused with the distinction preventive maintenance and predicative maintenance. May someone help to explain the difference between the two kinds of maintenance?

I believe you mean “Predictive Maintenance”.
See Wikipedia definition Predictive_maintenance
The Overview paragraph provides a good distinction between both approaches.
In short, adding intelligence to an existing preventive maintenance is Predictive maintenance.

Regards,
Govind.

 

[Marc]

Summary:

PdM or condition based maintenance attempts to evaluate the condition of equipment by performing periodic or continuous (on-line) equipment monitoring. The ultimate goal of PdM is to perform maintenance “just in time”, before the equipment fails in service. This is in contrast to time and/or operation count based maintenance where a piece of equipment gets maintained whether it needs it or not. Time based maintenance is labor intensive, ineffective in identifying problems that develop between scheduled inspections and is not cost effective.

Most PdM inspections are performed while equipment is in service, thereby minimizing disruption of normal system operations. Adoption of PdM in the maintenance of equipment can result in substantial cost savings and higher system reliability.

 

[Steve Prevette]

In the past two years the equipments have never been down by accident.” When asked for relevant data, he said that because the equipments hadn’t been down they had no data.

Another item to be wary of is "have never been down by accident". Some companies play games with downtime, shuffling the books to make it look like the equipment was down for "planned maintenance". You do have to watch out for "the machine just broke, now it is time to do its planned maintenance". I'd ask to see the records for downtime for non-accidental reasons.

 

[Tim Folkerts]

Time based maintenance is labor intensive, ineffective in identifying problems that develop between scheduled inspections and is not cost effective.

Or at least, such scheduled maintenance can be ineffective.

I have heard tales (although I haven't seen the raw data) that some operations like changing lightbulbs can be more efficient on a fixed schedule. If you have to run a requisition, call a guy to get a ladder from some other building and then climb up to change one bulb, there is a lot of extra labor. By changing bulbs before they actualy wearout, there is extra material cost, but reduced labor cost. In some cases, this type of maintenance might be the most effective approach.


Tim F

 

[darkafar]

Thank you all. Problem solved.

 

[vanputten]

Also, Predictive maintenance tends to include direct measurement of the item. Example, an infrared picture of a circuit board to determine hot spots.

Preventive tends to be done on time schedules (as you have.) Predictive tends to be direct measurement of the item to determine if it needs maintenance.

Other examples of Predictive Maintenance - evaluation of particles in suspension in a lubricant, sound and vibration analysis of a machine.

Regards,

Dirk

 

[Tadek]

Also, Predictive maintenance tends to include direct measurement of the item. Example, an infrared picture of a circuit board to determine hot spots.

Preventive tends to be done on time schedules (as you have.) Predictive tends to be direct measurement of the item to determine if it needs maintenance.

Other examples of Predictive Maintenance - evaluation of particles in suspension in a lubricant, sound and vibration analysis of a machine.

Regards,

Dirk

I agree with you

 

[Marc]

Also see: Preventive vs. Predictive Maintenance - What is the difference? TS 16949 - 7.5.1.4.
and
Preventive vs. Predictive discussion threads.

 

[jrubio]

In Europe we are involved in a new and Experimental Standards EN (Europeean Norms) for Maintenance.

ENV 13269: Maintenance - Guideline on preparation of maintenance contracts
EN 13306: Maintenance - Terminology
prEN 13460: 2001 Maintenance - Documents for Maintenance
prCEN/TS 15331: Criteria for design, management and control of maintenance services for buildings
prEN 15341: Maintenance - Maintenance Key Performance Indicators

http://www.wear-management.ch/?path=root+standards&lang=en


PDF:

http://www.dienstleistungs-standards.de/englishsite/020903/franlund.pdf

My University of Engineers of Seville (Spain) is leadering these new Standards