Posted on behalf of Larry

Has anyone ever come up with or found standard definitions for PdM and CBM? I’m developing standard maintenance policies and plans for a
federal agency and can’t get folks to even agree on basic terminology.

Larry

For my .02 cents worth, PdM encompasses all non-intrusive maintenance technologies and Condition Based Maintenance is the program in which PdM is executed.

The other Larry,

Some things never change.

I agree with Mr. Johnson somewhat.

I have experienced some companies teaching RCM as the way to go. I don't disagree however, they have tried to blend Lean, TPM, RCM, and any other kind of maintenance and production philosophy you can find. Now talk about terminology dysfunctionality !!!

Under this program PdM is a subset of the PM program and covers all nonintrusive activities including operator cleaning and lubrication.

The CBM is the mindset/philosophy where one would delay instrusive PM's based on condition.

Or

Schedule maintenance based on condition as found by the noninstrusive activities.

The goal being to run the equipment for as long as possible and doing the maintenace just prior to the functional failure. For this to work you would have to know and have an accurate P-F Intervals for all critical equipment.

All this should come under the Reliability Program which is driven by someones philosophy and variation of Reliability Engineering. The basics are the same the details usually vary depending on who's tune you are marching to.

Back in 1992 at the VI meeting in Hershey, PA John Mitchell got up to give a presentation on common terminology. The whole session came to a halt in about five minutes. No one could agree on anything.

There are many flavors and colors of maintenance philsophies in the world. The terminology differences and disagreements in terminology will drive you crazy?

The point here is you may have to do like had to be done in the DoD where the Systems Engineering and Configuration Management community had to come up with their own standards and terminology so we all knew what we were talking about. If you are doing this for a Federal Agency isn't there an existing standard that covers this work.

In all honesty you'll probably have to come up with your own. Getting anyone to agree with it is another issue.

Regards

Larry,

My take on this is as follows.

The timing of maintenance intervention is based on our expectation of time of failure.

This expectation can be based on the trends of a physical(or chemical or biological) degradation mechanism, using the so-called P-F curve. Or it may be based on a statistical evaluation of past data of physical failures.

1. PdM is any process that helps identify time to functional failure using physical parameters in a way that has a high confidence level. Usually, this means that failure has already been initiated, but the item is still able to function.

2. CBM is an approach or philosophy that uses the knowledge of equipment condition to determine the timing of maintenance intervention. Thus a heat exchanger fouling may be determined by the differential pressure trends (PdM) or from past records of equipment fouling condition. In the second case, it will be an age-based scheduled overhaul, predicting the failure using past data. CBM is understood to be primarily a PdM approach, i.e., based on physical condition trends. In theory, it should include predicted failures using a statistical evaluation as well. In practice, CBM is understood to use only physical trends.

Using RCM terminology, we use on-condition tasks, and scheduled overhaul or replacement tasks.

On-condition tasks are based on PdM trends. The expected time of failure is based on PdM.

Scheduled (age-based) tasks are timed by deterministic predictions of time-to-failure (peaky probability density curves). The expected time of failure is NOT based on PdM trends, but on statistical prediction based on past records.

The use of the terms PdM and CBM may have something to do with marketing; it is easier to sell a technology that 'predicts' and is 'condition-based'. If we can slip in 'pro-active' as well into the blurb, so much the better!

V.Narayan.

This message has been edited. Last edited by: Vee,

NavAir definitions in this ppt

C1-3(Term).ppt (162 Kb, 63 downloads)

More MIL Std definitions

c-3.pdf (524 Kb, 60 downloads)

Finally, from the NAVSEA Level 2 RCM training, attached.

CBM is a philosophy of guiding maintenance based upon condition of the equipment.

PdM is a tool for testing the condition of equipment using trendable test results.

Quick and simple.

Howard

a11_Basics_of_RCM.pdf (324 Kb, 62 downloads)

There are obviously several definitions of CM/PdM. It was called "diagnostic testing" when I started in the game. I now use this definition to make it clearly a part of maintenance activity (attached slide). Without a closure relating it to business purposes, it is only an academic activity!

Ray Beebe

What_is_CM.ppt (19 Kb, 61 downloads)

Is the one related to the quantity (CBM) of the failure and the other related to the quality of the failure (PdM) ?
Maybe this short last question is the way to say the same that in alot of words.
Any thought ?

Miguel Kovac

This message has been edited. Last edited by: Miguel Kovac,

I would think PdM falls under CMMS but CBM (condition based maint is as mentioned above). PdM = Predictive Maintenance and you predict when a machine will fail and base planning and scheduling on that. In RCM you have reliability as the main motive or dirving force; but PdM is a tool to take you there. I do put PdM at the top of the pyrimid......sorry, gotta scoot - being called but this is a good topic.

Condition-Based Maintenance is the philosophy of maintaining equipment based upon equipment. (Doing the right maintenance on the right equipment at the right time).

It involves all aspects of PM, PDM, CM, Servicing, Lubrication, RCM, etc.

RCM is a tool used as part of the CBM philosophy to select the proper PM, PdM, CM, etc.

PdM utilizes tools that provide measureable, trendable results and is a subset of CBM, as are other inspections for condition.

CMMS is a software tool for scheduling and maintaining a database of materials, etc. It also falls under CBM with RCM results and MER results feeding into it (when properly applied). PdM is not a subset of CMMS.

CBM: Condition-Based Maintenance
RCM: Reliability-Centered Maintenance
PdM: Predictive Maintenance
PM: Preventive Maintenance
CM: Corrective Maintenance
RM: Reactive Maintenance
CMMS: Computerized Maintenance and Management System

Hope this helps,
Howard

CBM_and_PdM.pdf (286 Kb, 48 downloads)