P & TS ASSET MANAGEMENT

Transcription

1 .5 System Cost Per Time.5.5 OPTIMAL P & TS ASSET MANAGEMENT SUBASSEMBLY NORMS Time Between Actions

2 CONTENTS Problem Statement Objectives Proposed strategy Anticipated Benefits Scope Illustrative Approach Optimality (Hypothetical Data) Optimality (Real Data) Case for change Basis for recommendation Key Success Factors Questions

3 PROBLEM STATEMENT Syst em Cost Per Time Time Bet ween Prevent ive Maint enance Act ions Given the need to minimise running cost, the use of gut feel to estimate repair/replace points can have negative impacts on future cash flows. The paper to be presented is to show how one can use a combination of statistical methods and the concept of present value of money (LCC) to determine the optimum replacement time.

4 OBJECTIVES Syst em Cost Per Time Time Bet ween Prevent ive Maint enance Act ions To resolve the above-stated problem, the following objectives were set: To calculate the optimal lives of subassemblies To determine the Life Cycle Cost (LCC) implications for both the current paradigm and the scientific approach (Time Value of Money) To determine the failure and reliability profiles of the various subassemblies To determine the failure characteristics of the various subassemblies

5 PROPOSED STRATEGY Syst em Cost Per Time Time Bet ween Prevent ive Maint enance Act ions To meet the set objectives the following strategy using asset management techniques is proposed: Renewable theory of electromechanical subsystems to determine optimal cost for a specific tonnage carried by each subassembly WeibullDistribution to analyse equipment failure characteristics, reliability profiles and spreading out the cost on a continuous distribution Net Present Value Analysis to determine Life Cycle Cost

6 ANTICIPATED BENEFITS Syst em Cost Per Time Time Bet ween Prevent ive Maint enance Act ions The following benefits are anticipated: Current Paradigm Optimal Route More accurate budgeting process. Time saved on unnecessary cost on late or too early PM intervals Net reduction in Life Cycle Cost of a CM from one overhaul to the next. Management will have reliability information data at subsystem level for an informed decision-making purposes.

7 SCOPE Syst em Cost Per Time Time Bet ween Prevent ive Maint enance Act ions Using a subassembly from one of the Continuous Miners from one of the mines at Sasol Mining, the following exercise will cover the work as follows: Collect historical data SAP R/3 regarding cost and life history Conduct a literature review on the subject Carry out a thorough mathematical modeling Generate a model usable for section engineers and planners at the mine

8 ILLUSTRATIVE APPROACH A sub assembly in operation will follow either the failure cycle (Cf) or the expected norm cycle (Cp): T = Early, tf Replacement point, tp Cost = Cf Cost = Cp The total cost Ct for the entire cycle is given by: C T = C ( t p p R + C f t p ) R + ( R) f ( t) dt Where Cp is the cost of preventive maintenance, Cf is the cost of a failure, tp is the time or tons between preventive or norm maintenance actions and R is the reliability given by the Weibull Function. The optimum time or ton between maintenance actions is found by minimizing the total cost equation above.

9 OPTIMALITY (Hypothetical Data) cost in (R) Optimal Cost

10 OPTIMALITY Real Data 5. Optimal Curve for Traction Motor. Cent per ton 5.. Optimal point 6 tons, 5.4 cents/ton Current strategy, 75 tons, 5.77 cents/ton 5.. 7, 3, 3 3, 3 6, 3 9, 4, 4 5, 4 8, 5, 5 4, 5 7, 6, 6 3, 6 6, 6 9, 7, 7 5, 7 8, 8, 8 4, 8 7, 9, 9 3, 9 6, 9 9,,,, 5,, 8,,, Replacem ent Tons

11 CASE FOR CHANGE LCC IMPLICATION Decision Complex: Maintain Status Quo or follow the optimal approach? WACC = 5% per annum Optimal Route Cycle CYCLE COSTS NPV of Cycles Re F Cost Subassembly Norm Optimal Norm Cycle Re Replacement Cost Cycle - Re Cost Current Paradigm Optimal Norm Cycle Re Replacement Cost

12 .5 BASIS FOR RECOMMENDATION S yst em C ost P er Ti m e Time Bet ween Prevent ive Maint enance Act ions FOR A PERIOD OF CYCLES LET : Lp = LIFE CYCLE COST OF OPTMIMAL METHOD and Ls = LIFE CYCLE COST OF CURRENT PARADIGM IF Lp < Ls, then optimal norms should be adopted. Benefit: Implicitly -Budget Value will also be minimised. NB: Non-optimal Cycles do not carry minimal costs regardless of higher or lower number of tons

13 .5 KEY SUCCESS FACTORS Syst em C ost Per Ti m e Time Between Actions Quality data from the information management system Management Buy-In Continuous improvement in relevant data storage Willingness to shift paradigms

14 .5 System Cost Per Time.5 QUESTIONS Time Between Actions