Functions and Failures

The concept of functions and failures in modern maintenance management is very important. You may already be familiar with Failure Modes & Effects Analysis (FMEA), since it is a well-documented and established technique. However when used as a tool in to determine maintenance through RCM, the difference in the two basic approaches to FMEA need to be understood;

  • equipment approach, which lists each item and analyses their possible failure modes (bottom up),
  • functional approach, which recognises that every item is designed to perform a function or number of functions.

These functions are identified and the failure modes resulting in loss of function are analysed (top down).

It is functional FMEA that is crucial to the success of understanding the equipment and to determine the most applicable and effective maintenance. To carry out a functional FMEA the consequences of loss of function (functional failure) need to be known. To achieve this, the effects of loss of function(s) of the item, component or system needs to be identified and understood and hence the functions themselves need to be defined.

The following light-hearted example serves to highlight the Functions, Functional Failures, Failure Modes, Effects and Consequences in an FMEA worksheet.

 

System:

Facility: STARSHIP

Compiled by: Scotty

Sheet 1

FMEA

Equipment:

Name: USS ENTERPRISE

Reviewed by: 1st Officer Spock

 

Worksheet

Component:

Tag No. NCC 1701-D

Approved by: James T. Kirk

of

 
 

Function

  

Functional Failure

  

Failure Mode

Local Effect

System Effect

Consequence

1

TO ACHIEVE 5 YEAR MISSION

A

ACHIEVES LESS THAN 5 YEAR MISSION

1

NOT SYNDICATED TO ENOUGH TV COMPANIES

REVENUES DROP, CREW AUDITION FOR DIFFERENT JOB

TV COMPANY SCREENS THE X-FILES INSTEAD

Production Critical
 
   

B

ACHIEVES LONGER THAN 5 YEAR MISSION

1

SYNDICATED TO LOTS OF TV COMPANIES

REVENUE INCREASES, CREW PUT ON WEIGHT THROUGH RICH FOOD AND EASY LIVING

MORE SCRIPTS WRITTEN, NEXT GENERATION CREATED

Safety Critical
 
       

2

TOO MANY MERCHANDISNG OPPORTUNITES

MANUFACTURERS OF T-SHIRTS, KEY RINGS AND PASTIC TOYS WORKING FLAT OUT

YOU TOO CAN HAVE A MOBILE PHONE THAT FLIPS UP LIKE CAPTAIN KIRK’S

No Consequence
 
       

3

TOO MANY SUCCESSFUL MOVIES

      
 

2

TO SEEK OUT NEW WORLDS & NEW CIVILISATIONS

A

DOES NOT SEEK OUT ANY WORLDS OR CIVILATIONS

1

UNABLE TO NAVIGATE

BEARINGS NOT AVAILABLE

NICK LEASON JAILED

Production Critical
 
   

B

SEEKS OUT OLD WORLDS AND CIVILISATIONS

1

TOO MANY REPEATS ON TV

EPISODES GET VERY REPETATIVE

PEOPLE WATCH THE X-FILES INSTEAD

Production Critical
 

3

TO BOLDLY GO WHERE NO MAN HAS GONE BEFORE

A

DOES NOT GO

1

DILITHIUM CRYSTALS EXHAUSTED

WARP DRIVE TRIPS ON LOW ION FLOW

SWITCH TO IMPULSE POWER

Safety Critical
 
       

2

DRIVE WARPED

ENGINE TEMPERATURE RISES: ALARM ANNUNCIATED

ANNOUNCMENT THAT "SHE CAN’T TAKE MUCH MORE CAPTAIN"

Safety Critical
 
   

B

GOES TIMIDLY

1

ANALYSED SEPARATELY

      
 
   

C

GOES WHERE MAN HAS GONE BEFORE

1

SEE 2.B.1

      

Having established the functions, functional failures, failure modes and their consequences the next step is to determine which of the six basic maintenance strategies would be applicable and effective to prevent or mitigate the consequences of the failure;

  • On Condition Maintenance,
  • Scheduled Replacement,
  • Scheduled Overhaul,
  • Failure Finding Task,
  • On Failure Maintenance,
  • Redesign.

Our 4 day RCM seminar fully covers strategy selection, supplemented by an intensive and comprehensive case study.

See what others have to say about our training seminars here.

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