Definition:
The ratio of time that a machine is capable of functioning in the intended operation (available hours) to total calendar hours in the period under consideration, expressed as a percentage. The calculation of available hours is not a pure calculation since the result is amended by downtime hours that are specifically excluded or limited by the terms of the contract.
Description:
Contracts are written largely to ensure that production equipment is available for operation a sufficient number of hours to enable the mine to meet its production goals at a reasonable, predetermined operating cost. The specific provisions of a contractual availability guarantee vary significantly from site to site, i.e. time that the contractor will be given credit for (available hours), time that the contractor will be held accountable for (contractual downtime), as well as specific exclusions, e.g. tires, dump bodies, welding, etc. are defined in detail in the contract. Furthermore, contracts frequently specify caps or limits on downtime that apply to things such as delays waiting on facilities, repair equipment and or other support infrastructure that the contractor is not expected to provide and has little control over. Because these exclusions and limitations vary so widely from one site to the next, it is not possible to link performance in this area to any kind of Benchmark nor does it make any sense to attempt to make comparisons from one site to the next.
Calculation Methodology:
As mentioned previously, contractual availability formulae vary significantly from site to site thus there is no unique calculation method that is applicable across the board. Calculations for contractual availability are typically made using the following general form:
It is worthwhile to note that the determination of MARC Downtime Hours contributes to the lack of standardization as does the use of Total Calendar Hours. Many sites choose to use Scheduled Hours rather than Total Calendar Hours while others exclude Operational Delay Hours from the calculation of Available Hours. Since both of the elements in the equation are subject to individual site interpretation, the results can be highly variable.
Total Calendar Hours - MARC Downtime Hours Total Calendar Hours
Data Source(s):
Total calendar hours is equal to the total time in the period to be analyzed, e.g. 8760 hours / year, 720 hours / 30 day month, 168 hours / week, etc.
If the available hours calculation involves the combination of operating hours, stand- by hours, production delay hours and operational delay hours (as it does in many instances), that information can be obtained from the machine service meter reading and information coded within the dispatch system.
MARC downtime hours are obtained from the machine workorder history as well as the dispatch system. Dispatch information must be used to account for downtime that is not accompanied by a workorder. It is essential that the machine repair history contain detail sufficient to determine if individual downtime events are excluded from the MARC downtime calculation.
Benchmarks:
There is no Benchmark that is applicable to the Contractual Availability performance metric. Target performance should be compliance with the provisions defined within the contract or, in the absence of a contract, with customer expectations.
Usage:
While it is a valid indicator of customer satisfaction, Contractual Availability has very little value as an equipment management tool due primarily to the lack of standardization in calculation methodology. It can be beneficial to monitor Contractual Availability over time in conjunction with the Availability Index to detect trends in performance that can enable the equipment manager to take appropriate preemptive actions.
Interpretation:
Interpretation of Contractual Availability is very straightforward in that performance trending downward toward or falling below target levels implies that some type of corrective action(s) be taken. Availability Index is the equipment management tool in this case thus the interpretation is common to both metrics.
Action:
If Contractual Availability is trending toward or falls below contractual guarantee, the equipment manager should investigate as follows:
• Analyze the Availability Index to determine if the decline or shortfall is the result of frequency (MTBS) or duration (MTTR) of machine downtime events.
• Assess performance on an individual machine basis to determine if the shortfall is the result of overall fleet performance or if it is related to the performance of
• Perform a Pareto analysis to define the cause of the shortfall on a component or system basis.
• Once the causes of the problem have been identified, .he equipment manager is in a position to devise corrective actions or, at minimum containment strategies until corrective actions can be identified.
Has Impact On:
• Customer Satisfaction.
• Production.
• MARC financial risks, … falling below the target may require the payment of penalties or guarantees defined in the MARC agreement.
Is Impacted By:
• MTBS & MTTR, … since availability is a direct result of frequency and duration of downtime events.
• Asset Utilization, … since low utilization sites tend to exhibit higher availability and vice versa.
(Please see contributing factors in the previous sections on MTBS and MTTR.)
Presentation Format:
Contractual Availability data should be collected, analyzed and reported monthly. If Contractual Availability is in decline or has dropped below guaranteed target levels, it may be necessary to collect and analyze the data on a daily basis in order to track progress of corrective actions and to reconcile performance. Trending monthly Contractual Availability data over a twelve-month period in conjunction with MTBS, MTTR and Availability Index as illustrated by the graph on the following page is the most visual and effective method to define trends in performance.
0 5 10 15 20 25 30 35 40
Nov-02 Dec-02 Jan-03 Feb-03 Mar-03 Apr-03 May-03 Jun-03 Jul-03 Aug-03 Sep-03 Oct-03
Month - Year MTBS / MTTR - ( hour s) 84% 86% 88% 90% 92% 94% 96% 98% 100% Co n tra c tu a l Av a ila b ility & Av a ila b ility In d e x
Target Contractual Availability