Hitachi EX5500 / EX5600 Hydraulic Excavator Critical Spares Determination using RBD

Industry: Mining Sector

Services Required: Critical Spares Determination, Reliability Modelling

Location: Australia 

The client has a fleet of Hitachi EX5500 and EX5600 to load coal into haul trucks.

The client had identified that their hydraulic excavator fleet had not achieved their forecast availability with numerous major component failures combined with increasing Mean Time to Repair (MTTR) resulting in production loss. Holistic Asset Management (HolisticAM) was engaged by the mining company to undertake a review of their Hitachi excavator fleet critical spares.

The objective of this project was to understand key drivers for extended MTTR and to make a critical spares determination for the fleet.

The project utilised a hybrid onsite-offsite execution approach and was delivered on time and within budget.


Leveraging our OEM and site based experience we understand the challenges that mining companies face. Materials shortages and global logistics delays have driven up parts costs and lead times have increased resulting in extended downtime for assets. Some key challenges faced during this project included:

  • Downtime Data reporting
  • The client had an FMEA, however had not undertaken Criticality Analysis.
  • Determining which parts to hold and the minimum stock holding to ensure continued availability of the fleet. As the fleet ages, there is an added risk of age-related failures. It was important to accurately predict performance of the excavator and its parts consumption.
  • Rationalization of parts to determine what parts were common and interchangeable between the EX5500 and EX5600.


The client chose HolisticAM based on their OEM experience, condition monitoring expertise, on-site experience and proven record of delivering results in the mining industry.

As with all projects executed by HolisticAM, our methodical approach includes identifying the current state, identifying and review opportunities for improvement and presenting these opportunities to the client for consideration.

HolisticAM worked closely with the client’s engineering, planning and maintenance execution team to undertake the following reliability engineering tasks:

  • Downtime Data Analysis to determine systems, subsystems and maintainable items that contributed to unplanned maintenance on the trucks
  • Life Data Analysis (LDA) was undertaken to determine the Failure Characteristics, Mean Time Between Failure (MTBF) and reliability.
  • FMECA development including criticality analysis to determine the risk profile of the excavator
  • Identify parts costs, logistic delays etc.
  • Reliability Block Diagram (RBD) modelling of the excavator to undertake ‘what-if’ analysis to determine recommended spares holdings.


Key deliverables included:

  • Updated FMECA
  • Critical Spares identification
  • Minimum Spares holdings by fleet wide availability against spares quantities
  • Prediction of fleet performance over the next 5 years using RBD Model

“Using our data to create a Reliability Block Model of the excavator was a clever way to predict performance and determine critical spares holding”

Engineering Superintendent

Added Value

HolisticAM was able to create value by

  • Predicted saving of $4.6M in production loss over 5 years by ensuring critical spares were on hand
  • Increase in fleet availability and reduction in MTTR
  • Parts rationalisation across the fleet

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