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
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.
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.
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.
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>
Introduction
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
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