Case Study Of The Implementation Of Advanced Maintenance Techniques At Baa Heathrow Airport Ltd

of 11 Case Study of the Implementation of Advanced Maintenance Techniques at BAA Heathrow Airport Ltd

Case Study of the Implementation of Advanced Maintenance Techniques at BAA Heathrow Airport Ltd Andy Watson Sim Energy Ltd September 2009 Email: [email protected] Abstract By rethinking and re-planning maintenance procedures and making use of advanced planning techniques and technology it is possible to significantly reduce maintenance costs as well as the more considerable business impact costs through equipment failure. This case study examines how this was carried out on a practical level and what successes were achieved through actual examples of implementation. Introduction During the period from 1995 to 2001 the author was involved in the research, development, implementation and improvement of advanced maintenance techniques at Heathrow Airport. This document provides information regarding the various techniques involved and seeks to quantify some of the benefit gained and to be gained through implementation of these techniques. The document is broken down into key periods which reflected the emphasis on certain aspects of the implementation. A New Focus on Engineering The Engineering Department at Heathrow had existed for nearly as many years as the airport had been operational. Maintenance craftsmen were employed as direct employed labour by the airport authority (which since privatisation became known as BAA) to compliment the range of specialist contractors also employed to maintain the various types of equipment across the airport campus. Airports are relatively rare commercial sites comprising standard office buildings, large baggage processing infrastructure, passenger conveyors and other passenger sensitive equipment as well as airport terminals which combine many types of building in one. Airport specific equipment is also operated and maintained such as passenger boarding bridges (airbridges), fixed electrical ground power, runway, apron and taxiway lighting etc etc. Demands on the equipment vary with some requiring they deliver a service constantly during the operational period (such as baggage handling) to others which suffer great wear and tear due to its high use (such as airbridges and autodoors). While the Engineering Department were involved in the various company-wide initiatives it wasn’t until 1994 that a particular focus was put onto Engineering to

a) prove their worth based on the cost of operating the Engineering Department b) provide them a chance to improve themselves from both a customer service

perspective as well as a cost efficiency one


Around this time a Mr David Virgo was employed as General Manager of Engineering and in addressing the above two challenges asked himself and the Engineering Department a number of pertinent questions:

• How much does it cost to maintain the equipment that the department looks after?

• How much does it cost the company for that equipment to fail?

• How do we balance the cost of maintenance against the cost of not maintaining equipment?

• How would we know that we had achieved the optimum engineering performance?

At about the same time, the author was working for Engineering and was preparing to be dispatched to Tokyo International Airport (Narita, Japan) on a secondment. David Virgo seized this opportunity to use the author’s position to identify how much investment was made by the Japanese in preventing things from going wrong. During the two-year secondment in Japan the author worked with various departments within Narita Airport Authority and provided regular reports on the financial performance of their engineering department back to Heathrow. It became clear from this study that:

• On the whole, Japanese industry tends to avoid unexpected breakdown and failure of equipment

• Planned preventive maintenance is given considerable emphasis and investment to reduce the probability and frequency of unexpected failure.

• Design and development of equipment also incorporates a heavy amount of failure-avoidance testing and redesign in order that availability is maximised

To summarise, the Japanese psyche in industry has a preference to work proactively rather than reactively and the Japanese are willing to invest heavily to ensure that proactive measures are effective and reactive occurrences are minimised. On completion of the two-year secondment the author returned to Heathrow and worked with the Engineering General Manager to evaluate and quantify the findings and apply them usefully to the maintenance strategy at Heathrow. The prime conclusion is summarised in the graph below:


To understand the conclusions it is better explained through a number of steps: 1. On the lower graph the horizontal scale indicates proactivity, in this case

the amount of planned preventive maintenance (PPM). 2. As the amount of PPM is carried out, the cost of PPM increases to the

business shown by the increasing blue line. 3. When PPM in minimal or zero the amount of corrective maintenance

(CM) is very high as engineers work reactively to repair failed equipment. As the amount of PPM increases so CM decreases but naturally suffers the principal of diminishing returns and so the slope gradually peters off as shown by the red line.

4. The total cost of maintenance to the business is the sum of the blue line (PPM) and the red line (CM) and is shown as the purple line (overall maintenance cost.

5. From analysis it is recognised that maintenance at BAA and likely in most of the rest of the UK is described by the area within the pink shaded block to the left. In this behaviour, approximately 30% of maintenance cost is in planned preventive maintenance and 70% is in corrective reactive maintenance.

6. It is further recognised that maintenance in Japan is better described by the area to the right of the light blue shaded block. In this area of behaviour, approximately 90% of maintenance cost is in planned preventive maintenance with only 10% being reactive corrective reactive maintenance.

7. There exists an area described by the light-blue shaded block where annual overall maintenance costs were the same as in the pink area.

8. The upper graph however shows overall cost impact to the business. This uses a much high value scale on the vertical axis and would be typical for processes where stoppages in production would result in high financial losses (such as in manufacturing where productivity is directly proportional to profitability).

The emphasis of the upper “Cost of Breakdowns to the Business” graph is that while maintenance costs vary depending on the level of proactivity, these costs are usually far outweighed when compared to the massive financial impact caused by these breakdowns occurring. In the context of Heathrow Airport some well established examples of these cost impacts due to equipment failure included:

• £50 per bag misconnected on a transfer flight (£20,800 for a Boeing 747-400) due to a baggage failure

• £400 repaid to the airlines for a scheduled passenger boarding bridge failing to operate

• £36,000 in retail losses for an evacuation due to the fire alarm system sounding on a fault

From this recognition of BAA’s position it became intuitive to establish the following conclusions:

1. Engineering/Maintenance performance should be measured by gross material and labour cost but this should be of relatively low importance in comparison to failure and repair statistics.

2. To shift to a culture of 70% proactive maintenance and 30% reactive maintenance would require the same annual overall maintenance investment but would reduce impact to the business from failures and faults disproportionally higher than the maintenance costs.


3. To shift even further over to the right and make even more effort to be proactive would not yield the same savings in impact to the business costs. This might be seen to be too intrusive in maintenance and would cost more in overall maintenance costs.

4. To make the shift to the 70/30 proportion would require an investment in training, technology and time.

A Review of Proactive Maintenance The shift to a more proactive approach to maintenance required a planned approach beginning with a review of BAA Heathrow Engineering’s current stock of planned preventive maintenance records and requirements. The following diagram shows the elements which influenced the current maintenance procedures:

Insurance

Inspection

Requirements

Manufacturers

recommendations

Craftsmen’s

personal

methods

Historical

data/methods

Current

Maintenance

ProceduresHealth & Safety

at Work

Legislation

Areas of Influence

Areas of

Regulation

- No solid grounding

- Decided subjectively

- Inconsistent

- Insensitive to upgrades in technology

and procedure

Insurance

Inspection

Requirements

Manufacturers

recommendations

Craftsmen’s

personal

methods

Historical

data/methods

Current

Maintenance

ProceduresHealth & Safety

at Work

Legislation

Areas of Influence

Areas of

Regulation

- No solid grounding

- Decided subjectively

- Inconsistent

- Insensitive to upgrades in technology

and procedure It became clear that the maintenance procedures in use were a mix of partly-relevant and largely irrelevant requirements. There were some requirements which were bound in legality and legislation such as insurance inspections and Health & Safety at Work Acts. These however were normally very general and did not consider the equipment in a working context experiencing a variety and strains and stresses. The softer areas of influence included:

• Manufacturers’ recommendations which were often too focussed towards scheduled parts replacements (provided by the manufacturer of course) and again did not consider the equipment in its working context.

• Craftsmen’s personal methods which were inconsistent and not generally based on any objective requirement for maintenance.

• Historical data and methods which often meant that work plans were inherited from previous pieces of equipment and were not relevant to the current equipment stock.


This all resulted in a largely subjective, inconsistent and insensitive set of maintenance procedures. What was clearly required was a review of all maintenance and a process for establishing what was appropriate. The First New Technique – Reliability Centred Maintenance (RCM) RCM was developed by the airline industry following a change of emphasis in reducing the number of commercial aircraft crashes. The first reaction was to begin a programme of intensive scheduled parts replacement. This resulted in an increase of failures and so further research was undertaken by running to fail each component in an aircraft. The researchers discovered a number of surprising behaviours which can be largely summarised by the realisation that parts failure occurs more through human interference or lack of care during installation and commissioning than though wear-and-tear and life-related failure. The conclusion of this research work was a structured maintenance planning process based on:

• establishing appropriate maintenance tasks through analysis of failure type

• prioritising maintenance approach by the nature of the failure curve The RCM process works through a series of key questions:

• What is the FUNCTION of the equipment (what is it’s purpose and what are it’s performance expectations)?

• How does it fail to achieve that function i.e. what is its FUNCTIONAL FAILURE (which performance criteria aren’t met)?

• What is the cause or FAILURE MODE for that functional failure?

• What is the FAILURE EFFECT on both the equipment and the environment in which it operates?

• In what way does the failure effect MATTER?

• What maintenance task can be undertaken to prevent such a failure based on the failure curve for the failure mode?

• What should be done if a suitable maintenance task cannot be identified?

Time

Probability of failure

Above: Infantile Mortality behaviour failure curve

Through the realisation that most failures occur because of

• Poor design or specification

• Poor installation or commissioning

• Intrusive or inappropriate maintenance

• The above during a replacement task


and therefore that human interaction and interference was the prime cause of equipment failure, RCM seeks to minimise intrusion through its prioritising of maintenance tasks. The process asks the questions:

1. Is the failure hidden (i.e. does the evidence of failure only become apparent when something else fails thereby causing a catastrophic event)?

2. Can the failure be detected early on through some form of on-condition task? 3. Can the failure or the impact of failure be satisfactorily reduced by a scheduled

restoration task? 4. Can the failure or the impact of failure be satisfactorily reduced by a scheduled

replacement task? 5. Can a failure finding task be calculated and useful?

The essence of RCM is in planning the maintenance appropriately and it provides a background into which to consider:

• Condition Based Monitoring (CBM)

• Calendar based maintenance

• Predictive maintenance

• Run-to-fail options RCM was first trialled on baggage handling facilities but the author was quickly requested to implement RCM across the range of passenger boarding bridges (or airbridges) within the airport. Airbridges consist of an extendable tunnel driven and elevated by an electric-motor driven apparatus. The modern airbridge is equipped with a variety of devices to provide shelter and safety in the area between bridge and aircraft. Furthermore equipment is installed to make the driving of the bridge safe and reduces risk of damaging the aircraft. It is a considerable high technology device considering the simplicity of its function but it is used in high demand times and could cause serious injury or damage if misused or poorly maintained. Above: A simple diagram of an airbridge

The author worked with the airbridge maintenance team on a model of Thyssen airbridge which was of a fairly modern version for the time. After a 15-session project each lasting 2-3 hours and with some site visits the RCM programme was completed. Each maintenance task was now traceable to a functional failure and the most appropriate maintenance technique applied. In all the programme saw the following benefits:

Cab

Rotunda

Extendable tunnels

Drive unit

Elevation pistons

or drives

Cab

Rotunda

Extendable tunnels

Drive unit

Elevation pistons

or drives


• An actual reduction of planned maintenance resource time by 25% (where ineffective tasks had been deleted or frequencies had been extended)

• A reduction of reported failures of 40% following a 2-year evaluation.

• Identification of several multiple failures including one which would have led to an aircraft collision merely due to an override button spring failing.

• Identification of an operator training requirement which would significantly reduce the number of false callouts of maintenance staff.

The savings gained from merely the improvement in planned maintenance effectiveness are shown below: Technician hourly rate £100

Airbridge maintenance duration (hrs/yr) 1600

Number of technicians required 4

Number of airbridges 120

Planned maintenance/Total Maintenance 30%

Cost of this maintenance regime £768,000

Reduction through RCM implementation 25%

Maintenance cost saving £192,000

Resource cost invested in programme £34,000

Simple payback (months) 2.1 Through the incorporation of RCM on the airbridge stock and thereby used on other equipment, investment in Condition Based Monitoring (CBM) equipment was made to support the RCM implementation. The Second New Technique – Condition Based Monitoring The first active maintenance task suggested by the RCM process was to carry out on-condition or condition-based inspection tasks. These involved measuring some quantity of the equipment in a non-intrusive manner and while the equipment was still running. The quantity measured has to be useful in that:

1. It must be measurable to a usable degree of accuracy

2. It must be clear what the normal operating parameters of this measured property are

for the equipment in question

3. The criteria must be related to the “health” of the equipment.

The first large investment in CBM was made in acoustic monitoring devices. These would translate high frequency sound waves from machinery into a quantity known as distress and was related to the types of noise from metal-on-metal wear. These monitors were first used to detect early wear and tear in the bearings supporting the extendable tunnels of the airbridge but were later implemented for use on the baggage handling system.


Bearings

Motor Gearbox

Belt

Tension roller Drive rollerChassis

Above: A standard baggage conveyor belt

A typical component of a baggage handling system is the conveyor unit. As shown in the diagram above, it consists of a chassis on which two rollers are mounted, one for maintaining tension and one for driving. A rubberised or fabric belt is wound around the unit and the entire system is driven by a motor and gearbox arrangement on the drive roller. A relatively small airport baggage handling system could contain as many as 400 of these baggage conveyors. With high system demand and a lack of built-in system redundancy, one conveyor failure could cause a massive back-up of the system and bring an airport terminal to a standstill. Typical causes of failure of this conveyor include:

• Bearing failure in the motor

• Winding failure in the motor through overheating

• Bearing failure on the rollers

• Oil leakage from the gearbox

• Belt tearing On testing of the conveyor’s maintenance requirements through an RCM process it seemed as expected that the majority of failures were not life related but merely through incorrect installation, commissioning or maintenance. Contamination or failure of the bearings was considered to be a common occurrence and thus maintenance focussed traditionally on inspecting and greasing these bearings. Unfortunately the customary strip-down to inspect each bearing turned out to be one of the most likely causes of contamination and subsequent failure as well as being labour intensive. A standard maintenance overhaul of a conveyor required two engineers working for approximately one hour each. At the technician’s financial rate at the time this would thereby cost approximately £200 per conveyor (with two overhaul’s per year). For the Terminal 2 Baggage Handling System this planned task alone would mean:


Technician hourly rate £100

Conveyor overhaul duration (hrs) 1


Number of conveyors 393

Overhaul's per year 2

Cost of this maintenance regime £157,200 Through the RCM process and introducing CBM techniques in the guise of a handheld acoustic monitoring device, it became possible to inspect the “health” of the bearing (i.e. grease condition and quantity, bearing wear and contamination):

• By one person

• With the conveyor still working in situ

• Without the risk of contaminating the bearing

• Without the risk of reinstalling the conveyor incorrectly

• In ten minutes

• While maintaining a record of performance In order to establish a good inspection interval and thus catch a potentially failing bearing before it actually failed it was established that the inspection should take place on a 3-monthly basis. Even with this increase in frequency, the resultant maintenance regime was changed to:

Technician hourly rate £100

Conveyor inspection duration (hrs) 0.17


Number of conveyors 393

Inspections per year 4

Cost of this maintenance regime £26,200 This was an 83% saving in cost and time without even considering the savings from materials or parts replacement. Furthermore it is highly likely that the number of actual failures would be reduced through the reduction of contamination or mis-installation risk. The financial performance of this investment regarding merely the saving in planned preventive maintenance on the bearings is shown below:

Maintenance cost saving 83%

Acoustic monitor cost £4,000

Training and implementation £6,400

Total implementation cost £10,400

Simple payback (months) 1.0 Streamlining Implementation As time passed and the Engineering Department went through phases of reorganisation so system experts known as Maintenance Planners became appointed to oversee the planning of maintenance and its implementation over certain asset groups. Elements of the RCM approach were incorporated into maintenance planning and it became possible to reduce the duration in carrying out RCM studies by diverting focus onto evaluating frequencies and procedures on already existent planned maintenance


tasks. This in itself reduced the implementation resource cost considerably and further techniques and algorithms were created by the author to optimise maintenance to a preferred level of equipment availability, performance or reliability. CBM went on to see a gradual further implementation through the use of infra-red thermography, vibration testing, oil contaminant testing, current measurement and similar techniques.

Above: A thermographic camera pays for itself in its first usage at Heathrow by the author identifying where a high temperature hot water pipe had sprung a leak on a 30m underground leg thus nullifying the need to dig up the entire route.

Linking Advanced Maintenance with Energy Efficiency The links with energy efficiency would have been obvious at the time were there not so much focus on plant availability. During the author’s academic study he produced a major project for his Energy Engineering Degree on “Energy Saving By Appropriate Maintenance On Heavy Equipment” (Andrew Watson, 2001) which covers this area quite comprehensively. Within this study, research was carried out whose conclusions suggested various formula and routines for calculating the energy which could be saved through advanced maintenance techniques. It would seem second nature in the current climate to include energy efficiency as one of the equipment’s key functions back at the defining stage of any new RCM studies. Summary Advanced Maintenance Techniques such as RCM and CBM are not, in the author’s opinion, particular subjects of “rocket science”. They produce in fact the exact same conclusions as would be reached if any skilled and knowledgeable engineers were to sit down together for an extended duration and think carefully about what sort of maintenance should be carried out and why. RCM in particular relies very little on advanced mathematics or technical complexity; it is a structured and ordered process for establishing maintenance requirements based on the equipment in its working context. Since being involved in the RCM process, questions arise around the traditional maintenance regimes such as car servicing, MOT inspections, PAT testing and why these are carried out in the frequencies that are common. Having a tool as powerful as RCM means that any change to maintenance requirements can be justified using hard and objective data instead of instinct or tradition.


To summarise the benefits of these advanced techniques:

• They provide a structured and solid process for establishing maintenance requirements.

• They are designed and driven by the people who will be using the same procedures.

• They optimise maintenance requirements to the users or owners preferred level of service.

• They minimise intrusion and maximise maintenance that can be carried out without incurring plant downtime.

• They reduce the risk of accidents and incidents during maintenance procedures by eliminating unnecessary maintenance.

• They provide logical algorithms and formula for calculating maintenance frequencies even with complex, multi-layer systems.

• They minimise wastage whether that be in spare parts or energy/resource use. Suffice to say that most advanced maintenance techniques will pay for themselves well within one year of their implementation as well as reducing further risk and business impact as the examples in this case study have demonstrated.

For more information or if you are interested in implementing advanced maintenance techniques please contact Andy Watson on: Tel: 07737-385568 Email: [email protected] Website: www.simenergy.co.uk

Case Study Of The Implementation Of Advanced Maintenance Techniques At Baa Heathrow Airport Ltd

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