Maintenance Strategy Development for a Hydraulic Excavator

ENGG4103 - Assignment 1 2012

Maintenance Strategy Development for a Hydraulic Excavator

Dan Keating - 42050836

Alex Wheeler - 41767669

Katherine Peiterbon

Bradley Batterham

Table of Contents

Executive Summary. 3

Introduction. 4

Scope. 5

Functional Description Analysis. 6

Component and Functions Register. 6

HAZOP Analysis. 10

History. 10

Procedure. 10

Limitations. 11

Hydraulic Excavator HAZOP Analysis. 11

FMEA. 15

History. 15

Procedure. 15

Limitations. 15

Hydraulic Excavator FMECA Analysis. 16

Maintenance Strategy. 34

Theory. 34

Daily Maintenance Strategy. 37

Monthly Maintenance Strategy. 40

Overhaul Maintenance Strategy. 43

Bibliography. 48


Executive Summary

To develop a successful operations system, it is first necessary to create an optimal maintenance program. A prudent maintenance program is one that ensures safety and is environmentally and economically responsible. Our report delves into five key aspects of the scope. To begin with, the primary, secondary and protective functions of all major components were identified to produce a functional analysis of the physical assets of the hydraulic excavator. Following this, a HAZOP process was performed to analyse possible failures of each major component. Once these functional failures were identified, they were inserted into an FMEA analysis master sheet, where the frequency index, delectability rating and severity index were used to produce a Risk Priority Number. The risk priority number provided the basis for the decision making that eventually developed maintenance tasks for all major components.

Maintenance tasks are completed for different purposes with differing time scales required for implementation. The proposed overall maintenance strategies satisfy the requirements of daily, monthly and overhaul maintenance strategies. Using Ledet’s Maturity Model as a basis, a strategic or proactive maintenance plan is optimal. In modelling the maintenance strategy the graph below should be skewed to the right. However, without previous failure data, the most optimal maintenance strategy is predictive. Taking into account all consideraions the graph below is skewed to the right as much as possible given the available information.

TABLE

The proposed overall maintenance strategy is summarised in three tables (refer to section 6 of report). These tables explain the maintenance tactics that should be implemented to produce an optimal maintenance strategy for each component of the hydraulic excavator. This includes implementation technique, direct and indirect labour requirements and performance measurements. This technique was applied to develop daily, monthly and overhaul maintenance schemes.


Introduction

Maintenance has evolved dramatically over the past years, and now not only plays a key role in profit maximisation as a direct result of cost reduction but it has morphed into an increasingly important means of hazard and risk minimisation. As the latter has become such a strongly policed facet of the construction world coupled with increased legislation and global financial uncertainty, organisations throughout the world are searching for new initiatives to enhance their existing processes. As such, maintenance has been put under the spotlight and has become heavily investigated and scrutinized with the goal of gaining the greatest maintenance efficiency.

Maintenance can be defined as ‘the work needed to maintain an asset in a condition that enables it to reach its service potential’ (Queensland Government Chief Information Office, 2008). There are four main maintenance tactics which can be implemented on a daily, monthly or overhaul basis. These include:

  • Proactive Maintenance – root cause based maintenance which includes minimising the probability of failure by re-designing and operational restrictions.
  • Predictive Maintenance – performance deterioration based maintenance which relies on the condition of the components.
  • Reactive Maintenance – based on run to failure policies, or repair only at breakdown
  • Preventative Maintenance – time based maintenance conducted periodically to lower the probability of failure

It is vital that of these maintenance strategies, the most effective option is chosen. To aid in the assessment, a decision tree is often utilised (Campbell, 2006, pp.4). However, there are also external factors which must be considered as they can affect a company’s triple bottom line and often prevent the best maintenance strategy from being implemented. In this case, a balance must be created between demand for maintenance resources and supply of maintenance resources (Knights 2008, pp. 30). When investigating the hydraulic excavator, or any physical asset for that matter, it is essential that these factors be considered.

QUICK PARAGRAPH ON WHAT THE HYDRAULIC EXCAVATOR DOES AND WHY IT IS IMPORTANT THAT THE MAINTENANCE STRATEGY BE A GOOD ONE.


Scope

The report aims to develop a maintenance strategy for a hydraulic excavator. To do this, functional descriptions for the operation of the system and each major component were developed. A HAZOP analysis was used to then identify any possible functional failures. A FMECA analysis was then used on these functional failures and the RPN values obtained were to rank the possible failure modes. A RCM decision tree was then used to decide on appropriate maintenance tasks for each critical failure mode. Finally, maintenance tasks were then grouped in a way that describe the checks, inspections, maintenance activities and overhaul activities that are recommended. The report is not written in relation to a specific hydraulic excavator and thus the results can be applied elsewhere, however the scope of this report assumes unlimited maintenance resources.


Functional Description Analysis

A functional analysis critically describes the physical assets of components on a machine, a hydraulic excavator in our case. It aims to define the primary, secondary and protective functions of each component. These functions of the plant components centre around a business based methodology. It looks at what the asset was designed for use to fill this particular need.

The primary function refers to the core need for the component. The secondary function of the component refers to the additional roles the component must fulfil in order to maintain their primaries function. These supplementary functions can be more subtle, but the consequences of failure will be no less severe (Campbell 2006). The protective functions are design features which mitigate possible safety features. These usually consist of things such as warning alarms and sensors (Knights 2008).

Component and Functions Register

Component

Primary Function

Secondary Function

Protective Function

Hydraulic oil tank

Stores the hydraulic oil used to power the machines hydraulic cylinders.

It must carry sufficient oil to enable the machine to operate safely and efficiently.

The vessel contains a flammable, environmental and health hazardous substance. Therefore it must be fashioned as to prevent leaks and spills.

Hydraulic pump

Delivers the required oil flow and pressure to the relevant hydraulic cylinders.

The pump gets put under enormous stress on a regular basis. It must be have a long service life and will not fail.

A variable displacement function controls the pressure of the oil released into the discharge line. This ensures under or over pressurisation is avoided (Hydraulic Equipment Manufacturers 2012).

Hydraulic cylinder

Hydraulic oil is either pumped into the cylinder or sucked out. This in turn moves the cylinder and thus moves the relevant component, i.e the boom.

It must be able to carry the required pressure to move and hold the relevant load. If this fails

Aeration in the rod of the cylinder can cause explosions. To counter this intake of air, float valves are present in the hydraulic cylinder to keep air out.


Check valve

Allows flow in only one direction. It does not require external control to perform this.

They must have a low failure rate as to maximise the production hours of the hydraulic excavator.

By only allowing oil to flow in one direction, it protects the equipment’s components that can be damaged by reverse flow. This is a major safety feature especially when the system shuts down.

Cylinder control valve

A valve with a pneumatic, hydraulic, electric or other externally powered actuator that automatically, fully or partially opens or closes the valve to a position dictated by signals transmitted from controlling instruments” (Considine 1985).

Low failure rate, which has the primary task of maximising production hours of the bucket. It is highly sensitive, so it is very reactive to changing conditions in the process.

It has the ability to quickly shut the machine in case of emergency. It also has the ability to release the pressure in case of power failure.

Pressure line

Transports the hydraulic oil safety an unobstructed around the excavator to its endpoint.

Needs to be able to withstand high variable temperatures without cracking or lowing pressure.

The hydraulic oil is highly flammable. It can have health risks which relate to eye, skin and respiratory irritation. The pressure line is designed to hold this oil safely.

Return line

This diverts hydraulic fluid away from the system should the pressure exceed safe standards.

It needs to be able to transport fluid at high temperatures and pressures. It needs to be flexible while carrying out the above conditions.

If the pressure in the circuit rises too high serious safety issues arise. Pipes and hoses can burst, leading to serious safety incidents and equipment damage.

Pilot circuit

This controls the hydraulic fluid that flows through the machine. It is the first circuit which overrides the fluid system.

It needs to be functioning if the excavator is to maximise production hours. Thus meaning it needs to have an extremely low failure rate.

Because the pilot circuit is the first circuit to receive hydraulic oil from the oil tank. It has the ability to shut the flow of oil off. This has the potential to avoid a safety risk if something is faulty further down the system.

Control lever

These levers control the hydraulic fluid which goes into the cylinder. They control the pitch and movement of the excavator’s arms.

The control lever deactivates hydraulic functions during start-up and prevents unintentional operation.

These need be in good operating order all the time, in order to safely control the excavator.

Pressure relief valve

Releases pressure in the system and prevents over pressurisation.

To safeguard against over pressurisation for the machine and operator.

A spring loaded component opens when the over pressurisation occurs. It then flows into an auxiliary passage.

Accumulator

The accumulator is the energy storage device. Potential energy is stored via compressed nitrogen

It has the ability through storing energy to allow the pump to idle. This reduces the wear and ultimately lengthens its lifecycle by resting it during the normal work cycle.

Because it has stored energy. It can maintain power in the event of power failure. This gives it the ability to safely shut down the excavator and prevent damage.

Boom

It is used to manipulate the bucket up and down.

It has baffle plates which reinforce the boom for higher rigidity. This ensures the boom is designed for maximum payload and therefore ensuring maximum production rates.

Stick

It is used to manipulate the boom in and out horizontally.

The connection between the boom and the forged steel. Like the boom it also has baffle plates. This ensures that maximum production rates can be achieved.

Bucket

Located on the end of the stick via supports. It can cut into solid material excluding very hard materials such as rock. Used to pick material up and place it in a different location.

The bucket must be able to withstand the forces of picking material up. To do so and adequately tough material must be selected to be resilient over a long time period.

The material used in making the bucket is designed to fail in such a way as to not cause shrapnel to fly off. The teeth at the end of the bucket fail in the same manner.


Bucket cylinder fitting

Provides the hydraulic pressure which enables the bucket to be able to be operated.

The bucket cylinder fitting must be able to provide enough pressure to handle the loads carried by the bucket.

Aeration in the rod of the cylinder can cause explosions. To counter this intake of air, float valves are present in the hydraulic cylinder to keep air out.


HAZOP Analysis

History

Developed around 1966 the HAZOP analysis (Hazard and Operability Analysis) was used in its most primitive form for the management of highly hazardous materials by the Imperial Chemical Industry. Since this time Lawley officially published HAZOP as a disciplinary procedure in 1974 and titled it “Operability Studies and Hazard Analysis” as a way of identifying when a process deviates from what was intended (Dunjo et al, 2009). HAZOP over time has been developed and improved since the days of its inception by Lawley and other pioneers and is now widely accepted as an excellent study to conduct in order to prevent human, environmental and economic loss within industrial processes (Rossing et al, 2009).

Procedure

There are numerous different methods from which a HAZOP study can be undertaken. Whilst the steps differ ever so slightly the overall goal that is achieved remains the same. In this report the HAZOP designed by Skelton in 1997 will be focused on and its method is as follows:

· Defining the studies aim, process information gathered, dividing plant into different sections and then possible deviations and variances are identified.

· The studies technique is revised and the scope established, each section described and their associated variations examined with the aid of guidewords (such as that in the below table).

· Action items are followed up, results reported and reviewed if necessary (Khan & Abbasi, 1997).

Table 1 – HAZOP Guidewords and their physical significance (Khan & Abbasi, 1997)

Limitations

HAZOP analysis will always be dependent upon two limiting factors. Firstly the team put together to conduct the study should comprise of several pertinent individuals to the particular area of the study. They should include a chairperson with previous HAZOP experience, engineers, management and operating staff (NSW Department of Planning, 2008). Some sources of literature say that the analysis can be completed with as little as 4 people however the best results will always be achieved when the widest range of suitably skilled individuals comprise the HAZOP team.

The second limiting factor to a successful HAZOP analysis is that of the accuracy of information referred to by the members of the group. Things like MSD’s, PFD’s and P&ID’s need to be up to date in order to be used as a helpful reference tool. Along with this, the environment the chairperson provides for the group needs to be conducive to brainstorming. He or she needs to encourage an overall theme of equality between the group, contrasting what sort of influence a particular stakeholder may or may not have normally (Harding, 1998).

Hydraulic Excavator HAZOP Analysis

COMPONENT

FUNCTION

FUNCTION FAILURE

FAILURE MODE

Hydraulic Oil Tank

Storage container for hydraulic oil

· Tank holds less oil than required

· Tank holds no oil

· Oil is unable to flow from the tank

· Tank not made big enough

· Tank entry and exit paths blocked

· Tanks structure was compromised

Hydraulic Pump

The device that pumps hydraulic oil

· Pump fails to pump oil

· Pump can’t pump oil fast enough

· Pumps oil to fast

· Pump creates too much pressure

· Pump doesn’t create enough pressure

· Mechanics of pump fail

· Pump isn’t powerful enough

· Pump is too powerful

· Pump isn’t being supplied with power

Hydraulic Cylinder

Hydraulic cylinder gets the oil pumped into it or sucked out which in turn moves the adjacent component

· Fails to handle oil pressure

· Cylinder moves too slowly

· Cylinder moves too fast

· Cylinder doesn’t move

· Cylinder fails structurally

· Mechanical components of the cylinder fail

· Cylinder gets too much oil

· Cylinder isn’t receiving enough oil

· Oil entrance into cylinder is blocked


Check Valve

Stops flow from going in the wrong direction

· Check valve fails to stop flow going in the opposite direction

· Check valve stops flow going in the correct direction

· Check valve only stops some of the flow going in the opposite direction

· Check valve is blocked

· Check valve fails mechanically

· Check valve fails structurally

Cylinder Control Valve

Used to partially or completely inhibit flow

· The cylinder control valve fails to inhibit flow correctly

· Control valve fails to open or close

· Structural integrity of valve is compromised

· Valve fails mechanically

· The cylinder control valve is obstructed

Pressure Line

Allows hydraulic oil to be transported around the machine

· Pressure line carries less oil than is required

· Pressure line carries too much oil

· Pressure line fails to divert fluid away from the system

· No fluid is being recycled into the system

· Pressure line is compromised structurally

· Pressure line isn’t connected properly

· Pressure line isn’t properly designed

· The recycle line is compromised

Return Line

Diverts fluid away from the system when the pressure gets to high

· Line diverts less fluid than required

· Line diverts too much fluid

· Return line fails too divert any fluid away from system

· Return line isn’t recycling any of the fluid it diverts

· The return line is compromised structurally

· The return line is connected incorrectly

· The return line isn’t designed properly

· Entry back into the pump is obstructed


Pilot Circuit

Controls hydraulic flow through the machine, first circuit to override the fluid system

· Fails to control oil flow through the machine

· Circuit sends oil to incorrect locations

· Fails to send oil quick enough

· Sends too much oil

· Fails to override flow system where appropriate

· Circuit compromised mechanically

· Circuit inappropriately designed for application

· Circuit fails electrically

Boom Control Lever

Control levers control flow of hydraulic oil which in turn controls the pitch of the boom

· Lever fails to control flow

· Lever fails to send enough fluid to the boom

· Lever sends too much fluid to boom

· Lever fails to operate

· Structural integrity of the lever fails

· Mechanically the levers aren’t suitable

· Levers aren’t connected appropriately to the system

Boom Relief Valve

Used to release pressure from the boom system

· Valve fails to release pressure when necessary

· Valve fails to release enough pressure

· Valve releases too much pressure

· Relief valve fails mechanically

· Relief valve fails structurally

· Relief valve is obstructed

Accumulator

Used to store energy

· Accumulator unable to store energy

· Accumulator unable to store enough energy

· Accumulator is storing too much energy

· Accumulator is unable to release any energy

· Accumulator is releasing too much energy

· The accumulator is compromised structurally

· The accumulator used is not powerful enough

· The accumulator is not big enough

· The accumulator is too big for the system

· Control valve mechanism fails

· Too much energy is being sent to accumulator


Boom

Used to manipulate the bucket up and down

· Boom isn’t strong enough to lift bucket with materials

· Boom moves bucket to slow

· Boom moves bucket to fast

· Boom is too large for applications

· Boom fails structurally

· Not enough pressure is being provided to the boom

· Too much pressure is being supplied to the boom

· The boom isn’t properly designed

Bucket

Used to move large quantities of earth material

· Bucket can’t carry enough material

· Bucket isn’t big enough

· Bucket isn’t strong enough

· Bucket is structurally compromised

· Bucket isn’t designed properly

· Bucket isn’t manufactured correctly

Bucket Cylinder Fitting

Provides the hydraulic pressure to enable bucket manipulation

· Hydraulic cylinder fails to handle pressure

· Cylinder moves too slow

· Cylinder move too fast

· Cylinder doesn’t move

· Hydraulic cylinder fails structurally

· Hydraulic cylinder fails mechanically

· Hydraulic fluid entrance blocked

· Cylinder is getting too much fluid

· Cylinder isn’t getting enough fluid

Stick

Used to manipulate the boom out and in horizontally

· Stick isn’t strong enough to hold bucket

· Stick moves bucket to slow

· Stick moves bucket to fast

· Stick doesn’t provide bucket with correct range of movement

· Stick fails structurally

· Not enough pressure being supplied to the stick

· Too much pressure being supplied to the stick

· Stick is poorly designed

· Hydraulic fluid not flowing consistently into stick

FMEA

History

The Failures Mode, Effects and Criticality Analysis, herein referred to as FMECA, was developed in the 1960s as a way of preventing the effects of equipment failure in the aerospace industry. It is the methodical study of cause and effect (McDermott 2008, pp.22). There are three common variations of the analysis that exist, and the choice of which analysis to use is dependent on the level of depth of analysis required. The FMECA identifies the way in which a component can fail, by identifying the failure modes. It can also identify the frequency and consequences of these failures, and, most importantly the relative importance of these failures. It is useful as a tool for risk assessment because it is a standardised method and thus uses a common language able to be understood by many and thus, information can be exchanged between companies (McDermott 2008, pp1.).

Procedure

The procedure for this analysis is as follows;

· Consider and list the functions of the device or mechanism

· List the possible functional failures

· List the failure modes of each of the functional failures, that is, list how each of the failures could come about

· List the failure consequences –the 4 types are hidden, safety and environment, operational and non-operational

· Make a judgment about the Severity, Frequency and Detectability of the failures and assign each a numerical value based on the Severity Rating Table, Frequency Rating Table and the Detectability Rating Table

· Assign each functional failure a Risk Priority Number using the formula RPN = S*F*D where S, F &D are the values given to Severity, Frequency and Detectability.

· Assign a method of control to monitor and prevent failure

· Make recommendations to improve the controls relating to the failure

· Assign responsibility for these actions and recommendations

Limitations

There are several limitations associated with this method. The NSW Department of planning identifies that the FMECA does not effectively identify combinations of failure modes. The systematic approach of the method, analyses the failure modes for each unit individually and thus combinations can be overlooked. This method also overlooks the cause of failure and focuses more on the effects and consequences of failure. This is a reactive way of dealing with the issues in question and other methods may be better suited to risk and hazard management and produce better results in the long term.


Hydraulic Excavator FMECA Analysis

Function

Functional Failure

Failure Mode

Consequence

Severity

Frequency

Method of Control

Detectability

RPN

Recommended Actions

Responsibility & Completion

Hydraulic Oil Tank

Storage container for hydraulic oil

Tank holds less oil than required

Tank not made big enough

Possible pump failure

9 - Due to production losses >8hrs

1-Once in the lifetime

Compensation by increase in working hours

1-Very high

9

Redesign

Hydraulic system designers

Tank holds no oil

Tanks structure was compromised

Possible pump failure

9 - Due to production losses > 8hrs

1-Occur up to once/ year

Regular inspection

3-High

27

Repair or replace where necessary

Maintenance supervisors

Oil is unable to flow from tank

Tank entry and exit paths blocked

Possible pump failure

3 – Failure generates safety hazard

3-Occur up to once/ month

Regular Inspection

3-High

27

Remove obstruction

Maintenance supervisors

Hydraulic Pump

The device that pumps hydraulic oil

Pump fails to pump oil

Mechanics of pump fail

Device does not work

7 – Due to production losses between 2 & 8 hrs

2-Occur more than once a year

Monthly recalibration and testing

4-high

56

Repair/ replace

Operator/ Maintenance supervisors

Pump isn’t powerful enough

Device does not work

9 – due to production losses > 8 hours

1-Once in a lifetime

Increase of working hours

6-Can be detected using a verification process

54

Pump capable of capacity required

Operator/ Maintenance supervisors/ hydraulic system designers

Pump isn’t being supplied with power

Device does not work

1 – Minimal downtime, no replacement costs

3-occur up to once a month

Check power source

1-certainty

3

Repair/replace

Operator


Pump can’t pump oil fast enough

Mechanics of Pump Fail

Device does not work

7 – Due to production losses between 2 & 8 hrs

2-Occur more than once a year

Monthly recalibration and testing

6-Can be detected using a verification process

84

Repair/ replace

Operator/ Maintenance supervisors/ hydraulic system designers

Pump isn’t powerful enough

Device does not work

9– due to production losses > 8 hours

1-Once in a lifetime

Increase of working hours

6-Can be detected using a verification process

54

Pump capable of capacity required

Operator/ Maintenance supervisors/ hydraulic system designers

Pump isn’t being supplied with power

Device does not work

3– minimal downtime, no replacement cost

3-Occur up to once a month

check power source

1-Definite

9

Repair/ replace

Operator

Pump creates too much pressure

Pump is too powerful

Failure of components not designed for this speed

5-replacement cost if other components are damaged

1-Once in a lifetime

N.A

1-Very high

5

Recalculation of pump size

Operator/ Maintenance supervisors/ Hydraulic system designers

Pump doesn’t create enough pressure

Pump is not powerful enough

Efficiency is reduced/ device does not work

7 – due to production losses between 2 &8 hrs

1-Once in the lifetime

Increase working hours

6-Can be detected using a verification process

42

Pump capable of capacity required

Operator/ Maintenance supervisors/ Hydraulic system designers

Hydraulic Cylinder

Hydraulic cylinder gets the oil pumped into it or sucked out which in turn moves the adjacent component

Fails to handle oil pressure

Cylinder fails structurally

Spillage, damage, pressure build-up

7-production losses and downtime between 2-8hrs

2-occur more than once a year

Monthly testing and recalibration

1-Very high

14

Repair/replace

Operator/ Maintenance supervisors

Mechanical components of the cylinder fail

Spillage, damage, pressure build-up

7-production losses and downtime between 2-8hrs

2-occur more than once a year

Monthly testing and recalibration

1-very high

14

Repair/replace

Operator/ Maintenance supervisors

Cylinder moves too slowly

Cylinder gets too much oil

Efficiency reduces/ device does not work

7-production losses and downtime between 2-8hrs

2-occur more than once a year

Monthly testing and recalibration

2-high

28

redesign

Operator/ Maintenance supervisors/ Hydraulic system designers

Cylinder moves too fast

Cylinder isn’t receiving enough oil

Efficiency reduced/ device does not work

7-production losses and downtime between 2-8hrs

2-occur more than once a year

Monthly testing and recalibration

2-high

28

redesign

Operator/ Maintenance supervisors/ Hydraulic system designers

Cylinder doesn’t move

Oil entrance into cylinder is blocked

Spillage damage, pressure build-up

7-production losses and downtime between 2-8hrs

2-occur more than once a year

Monthly testing and recalibration

1-very high

14

Repair/replace

Operator/ Maintenance supervisors

Check Valve

Stops flow from going in the wrong direction

Check valve fails to stop flow going in the opposite direction

Check valve is blocked

Possible explosion and damage to machinery

6-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

24

Remove obstruction

Mechanical maintenance supervisors

Check valve fails mechanically

Possible explosion and damage to machinery

6-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

24

Repair/ replace

Mechanical maintenance supervisors

Check valve fails structurally

Possible explosion and damage to machinery

6-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

24

Repair/ replace

Mechanical maintenance supervisors

Stops flow going in correct direction

Check valve is blocked

Possible explosion and damage to machinery

6-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

24

Remove obstruction

Mechanical maintenance supervisors

Check valve fails mechanically

Possible explosion and damage to machinery

6-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

24

Repair/ replace

Mechanical maintenance supervisors

Check valve fails structurally

Possible explosion and damage to machinery

6-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

24

Repair/ replace

Mechanical maintenance supervisors

Only stops some of the flow going in the opposite direction

Check valve is blocked

possible explosion and damage to machinery

3-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

12

Remove obstruction

Mechanical Maintenance supervisors

Check valve fails mechanically

possible explosion and damage to machinery

3-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

12

Repair/ replace

Mechanical maintenance supervisors

Check valve fails structurally

possible explosion and damage to machinery

3-generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (every 6 months), redesign of valves

2- High

12

Repair replace

Mechanical maintenance supervisors

Cylinder Control Valve

Used to partially or completely inhibit flow

The cylinder control valve fails to inhibit flow correctly

Structural integrity of valve is compromised

possible explosion and damage to machinery

6- generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (6 months), redesign of valves

2- high

24

Replace/repair

Mechanical Maintenance supervisors

Valve fails mechanically

possible explosion and damage to machinery

6- generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (6 months), redesign of valves

2- high

24

Replace/repair

Mechanical Maintenance supervisors

The cylinder control valve is obstructed

possible explosion and damage to machinery

6- generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (6 months), redesign of valves

2- high

24

Replace/repair

Mechanical Maintenance supervisors

Control valve fails to open or close

Valve fails mechanically

possible explosion and damage to machinery

6- generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (6 months), redesign of valves

2- high

24

Replace/repair

Mechanical Maintenance supervisors

The cylinder control valve is obstructed

possible explosion and damage to machinery

6- generates safety hazard, can be controlled

2-Occur more than once a year

Testing and recalibration (6 months), redesign of valves

2- high

24

Replace/repair

Mechanical Maintenance supervisors

Pressure Line

Allows hydraulic oil to be transported around the machine

Pressure line carries less oil than is required

Pressure line is compromised structurally

Spillage, pressure build-up, damage

7- production losses and downtime between 2-8hrs

2-More than once a year

Frequent inspection

2- high

28

Replace/repair

Operator/ maintenance supervisor

Pressure line isn’t connected properly

Spillage, pressure build-up, damage

5-Production losses and downtime < 2hrs

1-Up to once a year

Frequent inspection

1-definite

5

repair

Operator/ maintenance supervisor

Pressure line carries too much oil

Pressure line isn’t properly designed

Spillage, pressure build-p, damage

9-production losses and downtime >8hrs

1-Once in a lifetime

Data monitoring

1-Very high

9

redesign

Operator/ maintenance supervisor/ hydraulic system designer

Pressure line fails to divert fluid away from the system

Pressure line is compromised structurally

Spillage, pressure build-up, damage

7- production losses and downtime between 2-8hrs

2-More than once a year

Frequent inspection

2- high

28

Replace/ repair

Operator/ maintenance supervisor

Pressure line isn’t connected properly

Spillage, pressure build-up, damage

5-production losses and downtime <2hrs

1-Up to once a year

Frequent inspection

1-definite

5

repair

Operator/ maintenance supervisor

Pressure line is not properly designed

Spillage, pressure build-up damage

9-production losses and downtime >8hrs

1-Once in a lifetime

Data monitoring

2- high

18

redesign

Operator/ maintenance supervisor/ hydraulic system designer

No fluid is being recycled into the system

The recycle line is compromised

Total loss of oil

7-production losses and downtime <2hrs

1-Up to once a year

Frequent inspection

2-high

14

Replace/repair

Operator/ maintenance supervisor

Return Line

Diverts fluid away from the system when the pressure gets to high

Line diverts less fluid than required

The return line is compromised structurally

Spillage, pressure build-up, damage

7- production losses and downtime between 2-8hrs

1-Up to once per year

frequent inspection

2- high

28

Replace/repair

Operator/ maintenance supervisor

The return line is connected incorrectly

Spillage, pressure build-up, damage

5-production losses and downtime <2hrs

2-More than once per year

frequent inspection

1-definite

10

repair

Operator/ maintenance supervisor

Line diverts too much fluid

Return line not properly designed

Loss of pressure in hydraulic system

9-production losses and downtime >8hrs

1-Once in the lifetime

data monitoring

1-Very high

9

Replace/repair

Operator/ maintenance supervisor/ hydraulic systems designer

Return line fails to divert any fluid away from system

The return line is compromised structurally

Spillage, pressure build-up damage

7-production losses and downtime between 2-8hrs

1-Up to once per year

frequent inspection

3- high

28

Replace/repair

Operator/ maintenance supervisor

Return line isn’t recycling any of the fluid it diverts

Entry back into the pump is obstructed

Total loss of oil

7-production losses and downtime between 2-8hrs

1-Up to once per year

frequent inspection

2-Very high

14

Replace/repair

Operator/ maintenance supervisor

Pilot Circuit

Controls hydraulic flow through the machine, first circuit to override the fluid system

Fails to control oil flow through the machine

Circuit is compromised mechanically

Spillage, damage, pressure build-up

7-production losses and downtime between 2-8hrs

2- more than once per year

Testing and calibration every 6 months

2- very high

28

Repair/ replace

Operator/ maintenance supervisor

Circuit sends oil to incorrect locations

Circuit is inappropriately designed

Spillage, damage, pressure build-up

7-production losses and downtime between 2-8hrs

1-once per lifetime

Testing and calibration every 6 months

1-certainty

7

Redesign

Operator/ maintenance supervisor/ hydraulic systems designer

Fails to send oil quick enough

Circuit is compromised mechanically

Efficiency loss

4-losses of up to 1 hour, safety hazard, can be controlled

2- more than once per year

Testing and calibration every 6 months

2-very high

16

Repair/ replace

Operator/ maintenance supervisor

Circuit is inappropriately designed

Efficiency loss

4-losses of up to 1 hour, safety hazard, can be controlled

1-once per lifetime

Testing and calibration every 6 months

2-very high

8

redesign

Operator/ maintenance supervisor/ hydraulic systems designer

Sends too much oil

Circuit is compromised mechanically

Efficiency loss, spillage, damage

4-losses of up to 1 hour, safety hazard, can be controlled

2- more than once per year

Testing and calibration every 6 months

2-very high

16

Repair/ replace

Operator/ maintenance supervisor

Circuit is inappropriately designed

Efficiency loss, spillage, damage

7-production losses and downtime between 2-8hrs

1-once per lifetime

Testing and calibration every 6 months

2-very high

14

redesign

Operator/ maintenance supervisor/ hydraulic systems designer

Fails to override flow system where appropriate

Circuit fails electrically

Spillage, damage, pressure build-up

7-production losses and downtime between 2-8hrs

2- more than once per year

Testing and calibration every 6 months

6- failure can be determined by verification procedure

84

Repair/ replace

Operator/ maintenance supervisor

Boom Control Lever

Control levers control flow of hydraulic oil which in turn controls the pitch of the boom

Lever fails to control flow

Structural integrity of the lever fails

Device fails to operate, operates in an unsafe of less efficient manner

7-production losses and downtime between 2-8hrs

2-more than once a year

Frequent inspection

2-very high

28

Repair/replace

Mechanical maintenance supervisors

Lever fails to send enough fluid to the boom

Mechanically the levers aren’t suitable

Device fails to operate, operates in an unsafe of less efficient manner

7-production losses and downtime between 2-8hrs

2-more than once a year

Frequent inspection

2-very high

28

Repair/replace

Mechanical maintenance supervisors

Lever sends too much fluid to boom

Mechanically the levers aren’t suitable

Device fails to operate, operates in an unsafe of less efficient manner

7-production losses and downtime between 2-8hrs

2-more than once a year

Frequent inspection

2-very high

28

Repair/replace

Mechanical maintenance supervisors

Lever fails to operate

Levers aren’t connected appropriately to the system

Device fails to operate, operates in an unsafe of less efficient manner

7-production losses and downtime between 2-8hrs

2-more than once a year

Frequent inspection

2-very high

28

Repair/replace

Mechanical maintenance supervisors

Boom Relief Valve

Used to release pressure from the boom system

Valve fails to release pressure when necessary

Relief valve fails mechanically

Possible explosion, leakage, movement becomes too forceful

6- safety hazard, can be controlled

2-Occur more than once a year

Testing a recalibration every 6 months, redesign of mechanism

2-Very high

24

Replace/repair/ remove obstruction (where applicable)

Mechanical maintenance supervisors

Relief valve fails structurally

Possible explosion, leakage, movement becomes too forceful

6- safety hazard, can be controlled

2-Occur more than once a year

Testing a recalibration every 6 months, redesign of mechanism

2-Very high

24

Replace/repair/ remove obstruction (where applicable)

Mechanical maintenance supervisors

Relief valve is obstructed

Possible explosion, leakage, movement becomes too forceful

6- safety hazard, can be controlled

2-Occur more than once a year

Testing a recalibration every 6 months, redesign of mechanism

2-Very high

24

Replace/repair/ remove obstruction (where applicable)

Mechanical maintenance supervisors

Valve fails to release enough pressure

Relief valve fails mechanically

possible explosion, leakage, movement becomes too forceful

6- safety hazard, can be controlled

2-Occur more than once a year

Testing a recalibration every 6 months, redesign of mechanism

2-Very high

24

Replace/repair/ remove obstruction (where applicable)

Mechanical maintenance supervisors

Relief valve fails structurally

possible explosion, leakage, movement becomes too forceful

6- safety hazard, can be controlled

2-Occur more than once a year

Testing a recalibration every 6 months, redesign of mechanism

2-Very high

24

Replace/repair/ remove obstruction (where applicable)

Mechanical maintenance supervisors

Relief valve is obstructed

possible explosion, leakage, movement becomes too forceful

6- safety hazard, can be controlled

2-Occur more than once a year

Testing a recalibration every 6 months, redesign of mechanism

2-Very high

24

Replace/repair/ remove obstruction (where applicable)

Mechanical maintenance supervisors

Valve releases too much pressure

Relief valve fails mechanically

Less efficient

3-Losses of less than one hours

2-More than once a year

Testing and recalibration every 6 months, redesign of mechanism

2- high

12

Repair/replace/ remove obstruction where applicable

Mechanical maintenance supervisors

Relief valve fails structurally

Less efficient

3-Losses of less than one hours

2-More than once a year

Testing and recalibration every 6 months, redesign of mechanism

2- high

12

Repair/replace/ remove obstruction where applicable

Mechanical maintenance supervisors

Relief valve is obstructed

Less efficient

3-Losses of less than one hours

2-More than once a year

Testing and recalibration every 6 months, redesign of mechanism

2- high

12

Repair/replace/ remove obstruction where applicable

Mechanical maintenance supervisors

Accumulator

Used to store energy

Accumulator unable to store energy

The accumulator is compromised structurally

Loss of efficiency

4-losses of up to 1 hour, safety hazard, can be controlled

1-Up to once per year

Testing and recalibration every year, data monitoring, regular inspection every 3 months

1-Very high

4

Repair/replace

Mechanical maintenance supervisors

Accumulator unable to store enough energy

The accumulator used is not powerful enough

loss of efficiency

4-losses of up to one hour

1-Up to once per year

Testing and recalibration every year, data monitoring, regular inspection every 3 months

1-definite

4

redesign

Mechanical maintenance supervisors

The accumulator is not big enough

loss of efficiency

4-losses of up to one hour

1-Up to once per year

Testing and recalibration every year, data monitoring, regular inspection every 3 months

2-very high

8

redesign

Mechanical maintenance supervisors

Accumulator is storing too much energy

Accumulator is too big for the system

Capital costs

4-Cost of replacement

1-Up to once per year

Testing and recalibration every year, data monitoring, regular inspection every 3 months

2- very high

8

redesign

Mechanical maintenance supervisors

Accumulator is unable to release any energy

Control valve mechanism fails

pressure build-up, damage

6-safety hazard, can be controlled

1-Up to once per year

Testing and recalibration every year, data monitoring, regular inspection every 3 months

1-definite

6

Repair/replace

Mechanical maintenance supervisors

Accumulator is releasing too much energy

Too much energy being sent to the accumulator

loss of efficiency

4-losses of up to one hour

Up to once per year

Testing and recalibration every year, data monitoring, regular inspection every 3 months

1-Very high

4

Redesign/ replace

Mechanical maintenance supervisors

Boom

Used to manipulate the bucket up and down

Boom isn’t strong enough to lift bucket with materials

Boom fails structurally

Device is unable to be used productively

7- production losses and downtime between 2-8 hrs

1-up to once per year

Frequent inspection (and testing where applicable)

2-Very high

14

Repair/replace

Mechanical maintenance supervisors

Not enough pressure is being provided to the boom

Device is unable to be used productively

4-losses of up to 1 hour, safety hazard

2-more than once per year

Frequent inspection (and testing where applicable)

2-Very high

16

Repair/replace/ redesign

Mechanical maintenance supervisors/ operator/ system designer

Too much pressure is being supplied to the boom

Device is unable to be used productively

4-losses of up to 1 hour, safety hazard

2-more than once per year

Frequent inspection (and testing where applicable)

2-Very high

16

Repair/replace/ redesign

Mechanical maintenance supervisors/ operator/ system designer

The boom isn’t properly designed

Device is unable to be used productively

9-production losses and downtime >8hrs

1-once in the lifetime

Frequent inspection (and testing where applicable)

1-Certainty

9

redesign

System designer

Boom moves bucket to slow

Not enough pressure is being provided to the boom

Loss of efficiency

4-losses of up to 1 hour, safety hazard

2-more than once per year

Frequent inspection (and testing where applicable)

2-Very high

16

Repair/ replace/ redesign

Mechanical maintenance supervisors/ operator/ system designer

The boom is not properly designed

Loss of efficiency

9-production losses and downtime >8hrs

1-once in the lifetime

Frequent inspection (and testing where applicable)

1-certainty

9

redesign

System designer

Boom moves bucket to fast

Too much pressure is being supplied to the boom

Loss of efficiency, safety hazard

6-safety hazard, can be controlled

2-more than once per year

Frequent inspection (and testing where applicable)

2-Very high

24

Replace/ repair/ redesign

Mechanical maintenance supervisors/ operator/ system designer

The boom isn’t designed properly

Loss of efficiency, safety hazard

9-production losses and downtime >8hrs

1-Once per lifetime

Frequent inspection (and testing where applicable)

2-Very high

18

redesign

Mechanical maintenance supervisors/ operator/ system designer

Boom too large for applications

The boom isn’t designed properly

Loss of efficiency, safety hazard

9-production losses and downtime >8hrs

1-Once per lifetime

Frequent inspection (and testing where applicable)

1-certainty

9

redesign

Mechanical maintenance supervisors/ operator/ system designer

Bucket

Used to move large quantities of earth material

Bucket can’t carry enough material

Bucket is structurally compromised

Failure of device

5- production losses and downtime between 1-2 hours

2-more than once a year

Frequent inspection

2-very high

20

Replace/repair

Mechanical maintenance supervisors/ operator/

Bucket isn’t designed properly

Loss of efficiency

9-production losses and downtime >8hrs

1-once a lifetime

Frequent inspection

2-very high

18

redesign

Mechanical maintenance supervisors/ operator/ system designer

Bucket isn’t manufactured correctly

Failure of device, safety hazard

4- replacement cost

1-up to once a year

Frequent inspection

2-very high

8

Replace/repair

Mechanical maintenance supervisors/ operator/

Bucket isn’t big enough

Bucket isn’t designed properly

Loss of efficiency

9-production losses and downtime >8hrs

1-once a lifetime

Frequent inspection

2-very high

18

Redesign

Mechanical maintenance supervisors/ operator/ system designer

Bucket isn’t strong enough

Bucket is structurally compromised

Failure of device

5- production losses and downtime between 1-2 hours

2-more than once a year

Frequent inspection

2-very high

20

Replace/ repair

Mechanical maintenance supervisors/ operator/

Bucket isn’t designed properly

Loss of efficiency

9-production losses and downtime >8hrs

1-once a lifetime

Frequent inspection

2-very high

18

redesign

Mechanical maintenance supervisors/ operator/ system designer

Bucket isn’t manufactured correctly

Failure of device, safety hazard

4- replacement cost

1-up to once a year

Frequent inspection

2-very high

8

Replace/ repair

Mechanical maintenance supervisors/ operator/

Bucket Cylinder Fitting

Provides the hydraulic pressure to enable bucket manipulation

Hydraulic cylinder fails to handle pressure

Hydraulic cylinder fails structurally

Device is unable to operate properly

7- production losses and downtime between 2-8 hrs

1-up to once a year

Frequent inspection

3-high

28

Replace/ repair

Mechanical maintenance supervisors/ operator/

Hydraulic cylinder fails mechanically

Device is unable to operate properly

7- production losses and downtime between 2-8 hrs

1-up to once a year

Frequent inspection

3-high

28

Replace/ repair

Mechanical maintenance supervisors/ operator/

Cylinder moves too slow

Cylinder is getting too much fluid

Device is unable to operate properly

5- production losses and downtime between 1-2 hours

2-more than once a year

Frequent inspection

2-very high

20

Replace/ repair

Mechanical maintenance supervisors/ operator/

Cylinder move too fast

Cylinder is getting too little fluid

Device is unable to operate properly

5- production losses and downtime between 1-2 hours

2-more than once a year

Frequent inspection

2-very high

20

Replace/ repair

Mechanical maintenance supervisors/ operator/

Cylinder doesn’t move

Hydraulic fluid entrance blocked

Device is unable to operate properly

7- production losses and downtime between 2-8 hrs

2-more than once a year

Frequent inspection

2-very high

28

Replace/ repair

Mechanical maintenance supervisors/ operator/

Stick

Used to manipulate the boom out and in horizontally

Stick isn’t strong enough to hold bucket

Stick fails structurally

Failure of device

5- production losses and downtime between 1-2 hours

2-more than once a year

Frequent inspection

2-very high

20

Replace/repair

Mechanical maintenance supervisors/ operator/

Stick moves bucket too slow

Not enough pressure is being supplied to stick

Loss of efficiency

9-production losses and downtime >8hrs

1-once a lifetime

Frequent inspection

2-very high

18

redesign

Mechanical maintenance supervisors/ operator/ system designer

Stick is poorly designed

Failure of device, safety hazard

4- replacement cost

1-up to once a year

Frequent inspection

2-very high

8

Replace/repair

Mechanical maintenance supervisors/ operator/

Stick moves bucket to fast

Too much pressure being supplied to stick

Loss of efficiency

9-production losses and downtime >8hrs

1-once a lifetime

Frequent inspection

2-very high

18

Redesign

Mechanical maintenance supervisors/ operator/ system designer

Stick is poorly designed

Failure of device

5- production losses and downtime between 1-2 hours

2-more than once a year

Frequent inspection

2-very high

20

Replace/ repair

Mechanical maintenance supervisors/ operator/

Stick doesn’t provide bucket with correct range of movement

Stick is poorly designed

Loss of efficiency

9-production losses and downtime >8hrs

1-once a lifetime

Frequent inspection

2-very high

18

redesign

Mechanical maintenance supervisors/ operator/ system designer

Hydraulic fluid not flowing consistently into stick

Failure of device, safety hazard

4- replacement cost

1-up to once a year

Frequent inspection

2-very high

8

Replace/ repair

Mechanical maintenance supervisors/ operator/



class=Section4>

Maintenance Strategy

Introduction

A maintenance strategy is important in business and management as maintenance is an important tool to produce cost reductions and also has the ability to reduce the risk involved with projects and also to minimise hazards. Maintenance is defined by the Queensland Government as ‘the work needed to maintain an asset in a condition that enables it to reach its service potential’.

The four maintenance tactics most commonly used are proactive maintenance, predictive maintenance, reactive maintenance and preventative maintenance. They can implement on a daily, monthly or overhaul basis. Proactive maintenance focuses on the causes for maintenance which included minimising the likelihood of failure utilising redesign and operational restrictions. Predictive maintenance relies on the ability to detect performance deterioration which relies heavily on the condition of the components. Reactive maintenance is a reactive method whereby maintenance occurs after failure. And, Preventative maintenance is a time-based method whereby maintenance is conducted periodically to minimise the risk of failure.

It is important to pick the most effective of these four strategies for the specific project in question. A decision tree is often utilised for this purpose. However, external factors affecting a company’s triple bottom line often prevent the best strategy from being put into place. It is likely that a balance will be sought between a company’s demand for maintenance resources and supply of maintenance resources.

In this report the maintenance strategy for a hydraulic excavator will be developed. This is important as hydraulic excavators have increased in size and capability over the years and are an important part of many large mines. They are used in either back-hoe or face shovel configuration for loading broken rock on haul trucks. When considering a maintenance strategy for this piece of equipment, cost, downtime minimisation, availability of parts and environmental effects are all factors that need to be considered.

Theory

Overall, a maintenance strategy should aim at reducing equipment downtime and increasing machinery efficiency and production. An effective way of achieving this is through the development of a maintenance schedule and structure (Kelly, 1997). A successful organization is one that is able to maximize its machineries operating hours by implementing an action plan compromising of the following maintenance options.


Table 2 – Maintenance Options

Option

Strategy

Run to failure

No strategy, run till machine fails

Redundancy

Installing an unnecessary second unit in case of failure

Scheduled Component Replacement

Replacing units after a pre-determined time

Ad Hoc Maintenance

Maintenance is carried out only when time allows it

Preventive Maintenance

Repairs and servicing take place systematically on on-line hours or kilometres

Conditions Based Monitoring

Maintenance is carried out when aspect of machine isn’t performing

Redesign

Designing out the failure mode

When first coming to the conclusion of which maintenance strategy to go with, a maintenance decision tree will often be used. Ideally the option that creates smooth running machinery all of the time should be chosen however with demand always being so high a balance between all the options will generally be required (Knights, 2008). Once the strategy has been decided upon it can be evaluated by benchmarks of performance and these are as follows:

· Assess whether the object/target has been achieved

· Evaluate the internal performance

· Compare different companies

· Asses mechanical availability

~ (Choberka, 2003)

The mix of its implemented maintenance options can measure organizations maturity. Ledets Maturity Model priorities the different types of maintenance tactics used in industry in order of least to most effective.

Tying in all of this and designing an appropriate maintenance schedule for your organization can ensure a large increase in operating hours and profit optimization.


Daily Maintenance Strategy

Component

Maintenance Tactic

Maintenance Task

Direct Labour

Indirect Labour

Estimated Hours (Direct labour)

Warehouse Stock of Items

Performance Measurement

Hydraulic oil tank

Predictive (Conditions Based Monitoring)

·Inspection for preliminary signs of loose fittings

·Inspection of the pressure differential indicator data

· Operator

· System Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.1

N/A

N/A*

Hydraulic pump

Predictive (Conditions Based Monitoring)

·Inspection of pump electrical energy consumption

·Monitor fluid cleanliness

·Inspection of pump operating temperature

· Operator

· System Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

Pressure consistency checks daily

Hydraulic cylinder

N/A

-

-

-

-

-

-

Check valve

Predictive (Conditions based monitoring)

·Monitoring of pressure data

· System Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Cylinder control valve

Predictive (Conditions based monitoring)

·Monitoring of pressure data

· System Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Pressure line

Predictive (Conditions Based Monitoring)

· Inspection for leaks

·Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Return line

Predictive (Conditions Based Monitoring)

· Inspection for leaks

· Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Pilot Circuit

Predictive (Conditions Based Monitoring)

· Inspection for leaks

· Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Control lever

Predictive (Conditions Based Monitoring)

· Inspection of working order

· Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Pressure relief valve

Predictive (Conditions Based Monitoring)

· Monitoring of pressure data

· System Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Accumulator

Predictive (Conditions Based Monitoring)

· Inspection for preliminary signs of loose connections and/or fittings (screws, nuts and bolts)

· Inspection for preliminary signs of erosion/corrosion

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

Small quantity of machine housing material should be available for patching and repair jobs.

*This indicates that no specific performance measuring needs to be undertaken. The operator is responsible for adhering to company safety policies and training. The operator must be aware of his machine and the condition of the components. Daily prestart sheets must be filled out after the inspection carried out before the day’s work starts. The operations superintendent is responsible for managing these prestart inspections and any subsequent component issues that occur throughout a usual day’s work.


Monthly Maintenance Strategy

The monthly maintenance strategy encompasses the larger scale and more in depth maintenance tasks. It highlights the labour personnel requirements, the skillset required for each task and the administration/supervision staffing requirements.

Component

Maintenance Tactic

Maintenance Task

Direct Labour

Indirect Labour

Estimated Hours (Direct labour)

Warehouse Stock of Items

Performance Measurement

Hydraulic oil tank

Predictive (Conditions Based Monitoring)

Implement pressure differential indicator & automatic shut off switch

· Electrician System Programmer

· Electrician

· Fitter & Turner

· Technician

· Operations Manager

· Operations Superintendent

· Human Resources Staff

· Procurement Officer

· Workplace Health & Safety Officer

8

Frequency of replacement work is low. No stock recommended, capital cost too high.

· Suppliers checklist

· Successful trial of installation

Hydraulic pump

Reactive maintenance – run the pump to failure. This is due to the fact the average lifespan of a hydraulic pump is 10,000 – 12,000 hours (Vosburgh, 1964)

Replace or repair pump depending on severity of damage. Take into consideration the predicted lifespan after repairs vs. capital cost of replacement.

· 2 x Fitters & Turners

· Process Engineer

· Site Manager

· Operations Manager

· Operations Superintendent

· Human Resources

· Procurement Officer

· Workplace Health and Safety Officer

5

Frequency of replacement work is low. No stock recommended, capital cost too high.

· Suppliers checklist

· Successful trial of installation

Check valve

Preventative maintenance (scheduled replacement/restoration)

Six monthly recalibration and testing

· Fitter & Turner

· Operations Manager

· Operations Superintendent

· Human Resources

· Procurement Officer

· Workplace Health and Safety Officer

1

At least one check valve should be kept in stock

Use manual override to induce an excessive pressure for testing in the check valve

Cylinder control valve

Preventative maintenance (scheduled replacement/restoration)

Six monthly recalibration and testing

· Fitter & Turner

· Operations Manager

· Operations Superintendent

· Human Resources

· Procurement Officer

· Workplace Health and Safety Officer

1

At least one cylinder control valve should be kept in stock

Use manual override to induce an excessive pressure for testing in the cylinder control valve

Pressure line

Reactive maintenance – run to failure

Replace pressure line

· Fitter & Turner

· Operations Manager

· Operations Superintendent

· Human Resources

· Procurement Officer

· Workplace Health and Safety Officer

2

Spare pipe seals and, one reel of reinforced flexible high pressure line (Progressive Hydraulics Inc. 2009)

· Seals leak tested

Return line

Reactive maintenance – run to failure

Replace return line

· Fitter & Turner

· Operations Manager

· Operations Superintendent

· Human Resources

· Procurement Officer

· Workplace Health and Safety Officer

1

Spare pipe seals and, one reel of reinforced flexible high pressure line (Progressive Hydraulics Inc. 2009)

· Seals leak tested

Pressure relief valve

Predictive (Conditions Based Monitoring)

· Monitoring of pressure data

· System Operator

· Foreman

· OH&S Inspector

· Operations

· Superintendent

0.05

N/A

N/A*

Accumulator

Predictive (Conditions Based Monitoring)

6 monthly inspections of the physical unit. ‘Real time’ sensors which measure the levels of gas in the accumulator

· System Technician

· Operator

· Operations Manager

· Operations Superintendent

· Human Resources

· Procurement Officer

· Workplace Health and Safety Officer

4

N/A

· Suppliers checklist

Bucket

Predictive (Conditions based monitoring)

Monitor and determine when age related maintenance costs and efficiency losses outweigh the capital cost & minimisation of production rates is occurring

· Fitter & Turner

· Operations Manager

· Operations Superintendent

· Human Resources

· Procurement Officer

· Workplace Health and Safety Officer

2

N/A – Order on need to have basis or predictive analysis. As they have a high capital cost

· Successful trial of newly installed bucket


Overhaul Maintenance Strategy

This strategy is only implemented over a shutdown, as this is the only real major scheduled downtime the maintenance carried out is more severe. It focuses on the maintenance tactics, labour personal involved and the inventory considerations. It highlights any likely skill sets that each part may need and also the relevant management and admin staff required. The decision making in this section follows the Simplified Reliability Centred Maintenance Logic Tree.

Component

Maintenance

Tactic

Maintenance

Task

Direct Labour

Indirect

Labour

Estimated

Hours

Warehouse Stock of Items

Performance Measurement

Hydraulic

Oil Tank

N/A

-

-

-

-

-

Hydraulic Pump

Preventative Maintenance (Scheduled Restoration)

• Dismantle • Inspect pump impeller

• Inspect Shaft

• Inspect screws

• Electrician System Programmer • Electrician • Fitter & Turner

• Technician

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

8

Frequency of replacement is low. No stock recommended, capital cost to high

• Vendor supplied checklist

• Successful trial of installed components

Check Valve

Preventative Maintenance (Scheduled Restoration)

·Dismantle

·Inspect valve

·Lubricate

·Fitter and turner

·Technician

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

1

Spare valves as replacement frequency would be quite high

Successful trial of installed components

Cylinder Control Valve

Preventative Maintenance (Scheduled Restoration)

·Dismantle

·Inspect valve

·Lubricate

·Fitter and turner

·Technician

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

1

Spare valves as replacement frequency would be quite high

Successful trial of installed components

Pressure Line

Reactive maintenance (Run to Failure)

Replace pressure line

• Fitter & Turner

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

1

Spare pipe seals & fittings, 1 reel of reinforced flexible high pressure line

• Seals leak tested

Return Line

Reactive maintenance (Run to Failure)

Replace return line

• Fitter & Turner

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

1

Spare pipe seals & fittings, 1 reel of reinforced flexible high pressure line

• Seals leak tested

Pilot Circuit

Predictive (Conditions Based Monitoring)

·Dismantle

·Check wiring

·Check connection

·Test circuit

·Auto-electrician

·Fitter & Turner

·Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

2

Spare wiring and other specific electronics

Current testing to see if circuit worked

Boom Relief Valve

Preventative Maintenance (Scheduled Restoration)

·Dismantle

·Inspect valve

·Lubricate

·Fitter and turner

·Technician

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

1

Spare valves as replacement frequency would be quite high

Successful trial of installed components

Accumulator

Preventative Maintenance (Scheduled Restoration)

6 monthly inspections of the physical unit, 'real time' sensors which measure the levels of gas in the accumulator

• Operator • System Technician

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

4

N/A

• Vendor provided checklist

Piston

Predictive (Conditions Based Monitoring)

Inspect piston rings & general condition of piston

• Fitter & Turner

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

6

Spare piston rings

• leak test piston rings.

Hydraulic Cylinder

Preventative Maintenance (Scheduled Restoration)

·Inspect condition of hydraulic lines

·Dismantle

·Inspect condition of unit

·Lubricate the cylinder

·Fitter and turner

• Operations Manager

• Operations Superintendent • Human Resources

• Purchasing Officer

• Work Place Health and Safety officer

2

Spare hydraulic hose, no spare unit as replacement cost too high

Successful trial of installed components



Bibliography

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Choberka, P. 2003, Characteristics of World Class Mobile Equipment Maintenance Management,

viewed 27th March 2012, http://elearning.mea.edu.au/mod/resource/view.php?id=1913

Considine, D. 1985, Process Instruments and Controls Handbook, McGraw-Hill Publishing, Sydney

Crosby 1997, Crosby Pressure Relief Valve Engineering Handbook, viewed 19th March 2012, <http://www.tycovalves-na.com/ld/CROMC-0296-US.pdf>

J. Dunjó, V. Fthenakisb, J. A. Vílchez, and J. Arnaldos. "Hazard and Operability (HAZOP) Analysis. A Literature Review." Journal of Hazardous Materials (2009): 21.

Dunjo, J., V. Fthenakis, V., Vilchez, J. & Arnaldos, J. 2009, ‘Hazard and Operability (HAZOP) Analysis – A

Literature Review’, Journal of Hazardous Materials, vol. 173, no. 1-3, pp. 19-32

Harding, R. (ed) 1998, Environmental Decision-Making – the Roles of Scientists, Engineers and the

Public, The Federation Press, Sydney

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Kelly, A. 1997, Maintenance Strategy: Business- Centred Maintenance, Butterworth-Heinemann

Publishing, Burlington

Khan, Faisal I., and S. A. Abbasi. "OptHAZOP-an Effective and Optimum Approach for HAZOP Study." J. LOSS Prev. Process Ind. (1997): 193+.

Knights, Dr. P., 2010, Engineering Asset Management and Maintenance, viewed 19th March 2012, <http://elearning.mea.edu.au/mod/resource/view.php?id=2572>

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Education Australia.

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Rossing, Netta L., Morten Lind, Niels Jensen, and Sten B. Jørgensen. "A Functional HAZOP Methodology." Computers and Chemical Engineering (2009): 245.

Vosburgh, D. E. 1964. “The Hydraulic Pump”, Denison Engineering Division, Ohio.

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Paolocruz 3 years ago from Philippines

Informative! Thank you for the information. :)


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