RELIABILITY CENTRED MAINTENANCE (RCM)

A pragmatic approach to improve crane reliability

Graeme MassieTechnical Resource Manager Cranes &

Lifting

Presentation Overview

• Background – Where RCM originated

• Benefits – Why Use RCM

• RCM Process

• Data Sources – Lack of Actual Data

• Discussion

Background

• Need identified due to some major disasters such as: Bhopal,

Chernobyl & several aircraft disasters

• Airline Industry were first to react

• Known within the airline industry as MSG3 (Maintenance

Steering Group 3)

• All aircraft maintenance regimes are generated using this

process

• Industry recognises John Moubray as one of the leaders in

developing the RCM process

Benefits

• Management of crane safety and environmental integrity

• Ensures an acceptable level of reliability/ Availability

• Provides an audit trail for maintenance selection and challenge of

current regime’s

• Greater Maintenance cost effectiveness - time and money is directed

to maintenance tasks that make a real difference to integrity and

reliability

• Selection of appropriate maintenance task

• Longer useful life of expensive items

• Identifies single point failures

Process

Input (RCM Check List)

Function Functional Failure System Main Equipment Sub Equipment

Applicable to Current

Crane Type/ Model

Single Line Component

Failure Applies

Included in RCM Review Comments

Provide structure to support the forces applied during crane operations

Unable to provide structure to support the forces applied during crane operation

Structure

A Frame

Structure X XSheaves X XBoom Rope Anchor (Dead End) X X

Connecting Pins/bolts to M/C Bed X X Pins

Boom

Structure X XSheaves X XBoom Foot Bearings / Pins X XConnecting Bolts/ Pins X X BoltsRamsMain Hoist Winch Support Fitted on chassisAux Hoist Winch Support Fitted on chassisMain Hoist Anchor (Dead End) X X

Chassis

A frame Support X XBoom Hoist Winch Support X XMain Hoist Winch Support X XAux Hoist Winch Support X XBoom Foot Pins Support X XSlewing Bearing Support X XOperators Cabin Support X X

PedestalStructure X XSlewbearing support X X

Check List FMEA FCA MSS PMR’S

Failure Modes and Effects Analysis (FMEA)

•Function – What operation the equipment is expected to do

•Function failures - the way it can fail to fulfil its function, and includes both

total & partial loss of function. This is normally the opposite of the function

•Failure modes - what credible physical events would cause each functional

failure

•Local and system effects – following or leading to the failure event, what

happens to equipment directly associated with the failure and what effect

does it have on other systems and equipment

•Category - The effects information is used to distinguish the consequence

category for each identified failure mode, five consequence categories

•It is essential that when carrying out FMEA the assumption is that no

maintenance is done.

Check List FMEA FCA MSS PMR’S

Failure Category

Check List FMEA FCA MSS PMR’S

Failure Category

Consequence

Category

Failure

Mode

Failure Mode Conditions Required

Failure Mode Consequence

A Hidden Combined with one other failure mode or event

Safety and/or environmental hazard.

B Evident Direct Only Safety and/or environmental hazard.

C Evident Direct Only Operational capability adversely affected, but no effect on safety or environment.

D Evident Direct Only No effect on safety, environment or operation.

E Hidden Combined with other failure modes or events.

No effect on safety or environment.

Check List FMEA FCA MSS PMR’S

Failure Modes and Effects Analysis (FMEA)Typical function groups considered are:

•Provide structure to support the forces applied during crane operations.

•Support and manoeuvre the load in a safe and efficient manner using the boom hoist

system.

•Support and manoeuvre the load in a safe and efficient manner using the main and

auxiliary hoist system.

•Support and manoeuvre the load in a safe and efficient manner using the slew system.

•Provide a safe and efficient method for transfer of oil under pressure between the

hydraulic pumps and motors.

•Provide pneumatic controls to ensure that the crane operates in a safe and efficient

manner

•Provide electrical supply to all crane components required for safe and efficient operation.

•Provide protection to ensure that the crane is operated within its design envelope.

•Provide sufficient power and method to drive the hydraulic pumps

Check List FMEA FCA MSS PMR’S

Failure Characteristic Analysis (FCA)

Maintenance Strategy Selection Category•On Condition Maintenance (OCM) - Monitor some incipient condition and undertake

maintenance based on the results of monitoring, e.g., vibration monitoring or rotating

equipment.

•Scheduled Overhaul (SO) - Undertake an overhaul based on an appropriate measure

of item age.

•Scheduled Replacement (SR) - Replace the item based on an appropriate measure of

age.

•Failure Finding Task (FFT) - Test the item to ensure that it will function when

required, e.g., test ringing the fire bells weekly.

•On Failure Maintenance (OFM) - Allow the item to fail then repair it.

•RE-Design (RED) - Change the equipment, system or procedures to eliminate the

failure or change its consequences.

Check List FMEA FCA MSS PMR’S

Failure Characteristic Analysis (FCA)

Decision Logic Example

Check List FMEA FCA MSS PMR’S

Failure Characteristic Analysis (FCA)Incipient Condition

• Wear

• Corrosion

• Out of Adjustment

• Fatigue

• Cracking

• Loosening

• Seizure

• Degradation

• Depletion

Check List FMEA FCA MSS PMR’S

Failure Characteristic Analysis (FCA)

Strategy•LTTF (Suitable for Safety and

•Non-safety Critical

•Safe (Safety Critical Equipment) and

•Useful Life (Non Safety Critical)

•MTBF (Not suitable for Safety Critical failure modes)Cumulative Operating Time

MTBF = Cumulative Number of Failures

Check List FMEA FCA MSS PMR’S

Maintenance Strategy Selection (MSS)

• Task Description – What maintenance task are we going to carry out

• Single Point Failure – Does a single failure result in an uncontrolled decent of a

load/ boom

• Risk (Enermech or Clients Risk Matrix) – What is the risk when failure occurs

• In Current PMR’s – Is it included in the current maintenance regime

• Procedure/ Work Aid Required – Is a details procedure required

• Interval – What interval has been selected based on the FCA

• Interval Selected – If driven by another failure mode this may be different

• Selection Criteria – Whether LTTF, MTBF, Safe Lift & Useful Life

• System – Hoist, Boom, Slew, Structure, Hydraulics, Pneumatics ...

• Discipline – Crane Op, Crane Tech, Rope Access, NDT, Vibration Tech ...

• Duration (Mins)

Check List FMEA FCA MSS PMR’S

Data Sources

Information Gathering

• Review of OEM manuals

• Review of previous inspection reports

• Review of historical crane maintenance data held by client

• Review of maintenance backlog

• Review of MOC’S (Management of Change)

• Previous experience of same of similar types of cranes

• Knowledge from personnel who have worked with or maintained

same or similar equipment

Check List FMEA FCA MSS PMR’S

Input (FMEA)Failure Mode Effect Analysis

Ser Function Functional Failure

Failure Mode Local and System Effects SPF Likelihood Severity Risk Cat

1.01 Provide structure to support the forces applied during crane operations.

Unable to provide structure to support the forces applied during crane operation.

A-frame structural fail due to metal fatigue.

A-frame fractures. Collapse of A-frame and boom structure. Any attached load will fall. Probable injury to personnel, possible fatality. Secondary damage possible to platform equipment, structure and/or supply vessel. Loss of crane operational capability.

Y 1 4 4 B

2.01 Support and manoeuvre the load in a safe and efficient manner using the boom hoist system.

Unable to support and manoeuvre the load in a safe and efficient manner using the boom hoist system.

Boom hoist winch primary brake failure.

The boom hoist winch has a multi-plate disc brake system which is used as holding brake only, slowing down is controlled by the hydraulic system. A pawl lock energized when prime mover is stopped.

Y 2 2 4 B

3.01 Support and manoeuvre the load in a safe and efficient manner using the main and auxiliary hoist system.

Unable to support and manoeuvre the load in a safe and efficient manner using the main and auxiliary hoist system.

Main hoist winch primary brakes fail.

The main hoist winch has a multi-plate disc brake system which is used as holding brake only, slowing down is controlled by the hydraulic system. An external caliper disc brake energized when winch motion has stopped.

Y 2 2 4 B

Check List FMEA FCA MSS PMR’S

Input (FCA)

Failure Characteristic AnalysisIncipient Condition LTTF Safe Life Useful Life MTBF Comments

Cracks 8760 The failure interval is based on information from four years operation and maintenance of same or similar cranes. The approximate cranes operational running hours is 2700 per year. A review should be undertaken if there is a substantially change to the cranes operational duties or running hours.

Wear 8760 The failure interval is based on information from four years operation andmaintenance of same or similar cranes. The approximate cranes operational running hours is 2700 per year. A review should be undertaken if there is a substantially change to the cranes operational duties or running hours.

Wear 8760 The failure interval is based on information from four years operation and maintenance of same or similar cranes. The approximate cranes operational running hours is 2700 per year. A review should be undertaken if there is a substantially change to the cranes operational duties or running hours.

Check List FMEA FCA MSS PMR’S

Input (MSS)Maintenance Strategy Selection

MSS Task Description In current PMR's

Procedures/ Work Aid

Interval Interval selected

Selection Criteria

System Discipline Duration (Mins)

Comments

B-OCM Carry out a visual inspection of the A-frame structure for signs of deformation, corrosion & distortion.

Yes No 6M 6M Based on a LTTF interval of 12 months the recommended task interval is 6 months (1/2 LTTF interval).

Structure Crane Op Maintainer

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B-OCM Carry out a stall test of boom hoist circuit in the raise position by manually stroking boom hoist pump, and record pressure (350 Bar).Note: Boom to be in rest. Do not test for more than 3 seconds.

Yes Yes 6M 6MBased on a LTTF interval of 12 months the recommended task interval is 6 months (1/2 LTTF interval).

Boom Hoist Crane Op Maintainer

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B-OCM Carry out a stall test of the hydraulic main hoist circuit in the raise function using the joystick and record pressure (350 Bar). Note: Test input brakes separate from disc brake. Do not test for more than 3 seconds.

Yes Yes 6M 6M Based on a LTTF interval of 12 months the recommended task interval is 6 months (1/2 LTTF interval).

Main Hoist Crane Op Maintainer

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Check List FMEA FCA MSS PMR’S

Output (PMR’S)

Check List FMEA FCA MSS PMR’S

Overview

• It is not uncommon to review between 400 and 500 failure

modes within an offshore crane

• Far higher that some other offshore equipments such as

pressure vessels and pumps

• Actual data is always difficult to attain

•Due to the age of some equipment OEM support is no longer

available or supported

Case Study #1

• Client purchased 3 new rope luffing pedestal cranes

between 2000 - 2002

• OEM stated rope change out every 24 months

• Based on our knowledge of crane utilisation and experience

in consultation with the client it was moved to a 12 monthly

change out frequency

• Continued to NDT ropes for 3 years

• Approx 75% of ropes unsuitable for extended use

• Retained at 12 month frequency

Case Study #2

• Client has used same techniques and frequency of

maintenance for years no reviews carried out

• No consideration to failure modes that had a direct impact

on safety/ integrity

• Maintenance intrusive based

By using RCM we:

• Reduced maintenance hours by 40%

• Reduced maintenance costs

• Increased reliability

Case Study #3

• Client was keen to reduce maintenance hours and costs

• Cranes not given priority and maintenance had evolved over

the years with no real strategy

• Reliability was in question

• RCM review unveiled:

• Some maintenance tasks were carried out too frequent –

no consideration to cyclic based failures

• No consideration to time based failures such as

corrosion

• Some safety critical tasks like spline inspection had not

been included in scheduled maintenance

Discussion

• Availability of data

• Practicality of sharing crane reliability data

through out industry and cross border

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