University of Twente Student Theses

Login

The transition from operational availability to mission availability - Case study

Schmal, J.L. (2014) The transition from operational availability to mission availability - Case study.

This is the latest version of this item.

[img] PDF
4MB
Abstract:Thales is planning to deliver systems with a Performance Based Logistic contract. Thales is responsible for the whole maintenance process against a fixed fee. The key performance indicator is the mission availability per ship over a certain time period. The mission availability is defined as the system uptime during the mission divided by the mission time (mission uptime + mission downtime). The downtime is measured by the supply availability. Within a performance based logistic contract, Thales will receive financial penalties when the mission availability drops below the agreed mission availability target. Thales receives a financial bonus when the system performed as agreed. It is of great importance for Thales to determine what the effects are of a performance based contract. Thales performed several studies to estimate the effects and costs of a performance based logistic contract. This research focuses on the transition from the key performance indicator ‘supply availability’ to the mission availability. The objective of this research is to find an optimal spare parts allocation procedure for the antenna of the Smart-L ELR case. An optimal spare parts procedure involves minimizing the cost with as constraint a minimum mission availability target. Simultaneously it should take into account the mission’s length, annual operational hours, repair lead-time, of the multi-indenture antenna. In addition Thales prefers an spare parts allocation procedure which is “robust”. The solution of the optimized procedure are as less sensitive as possible for variations of the Mean Time Between Failure. In that case the solution may have slightly higher cost. With this objective the main research question is formulated: What is the optimal spare parts allocation procedure of the antenna of the Smart-L ELR to ensure that the minimum mission availability constraint is satisfied, the cost are minimized, considering mission profiles, annual operational hours, and repair lead-time? In this research there are four allocation procedures constructed, whereby the transfer point from Inventri to Simlox is different per procedure. The second procedure uses two types of ships, namely a mission ship and a short-mission ship. A mission ship goes on mission for several months and the short-mission ships will perform multiple short missions per year. The second procedure calculates the supply availability of the mission ships and the short-mission ships separately by Inventri. The mission ship allocation is combined with the ship spare parts of the short-mission ship allocations. Subsequently, Simlox is used to allocate the spare parts following a single-site METRIC allocation process, whereby the ships together are considered as single-site. Procedure 3 calculates the spare parts allocation to a supply availability level of 99.99% with Inventri. Afterwards checks the allocation list when the short-mission ship is allocated too. The spare parts allocation list, until the short-mission ship is allocated, is implemented in Simlox. Subsequently, Simlox is used to allocate the spare parts following a single-site METRIC allocation process, whereby the ships together are considered as single-site. The case study consists of a 3-echelon, multi-indenture supply network with three ships, one shore stock location and one original equipment manufacturer (Thales). From this case study, we can conclude: The third procedure generates higher mission availability solutions which are less sensitive to MTBF variations, but costs slightly more An experiment is conducted whereby it seems that the mission availability in procedure 3 is less sensitive to MTBF variations due to higher average mission availability solutions. The slightly more expensive procedure copes better to MTBF variations. Thales prefers a procedure which copes better to MTBF variations, regardless it has slightly higher costs. The third procedure can cope for this case at least to 12.5% lower Smart-L antenna MTBF values, but costs maximal 11% more. Procedure 2 generates overall the most cost-effective solutions Procedure 2 generates overall the most cost-effective solutions. Compared to procedure 3 this is a more labor-intensive procedure (more iterations), but generates cheaper solutions. The probability of backorders reduction is made plausible linearly proportional to the mission availability addition. It is made plausible that the delta probability of backorders (PBO) is linearly proportional to the delta mission availability. This is made plausible for a 3-echelon structure whereby in all the stock locations the delta EBO is made plausible to be linearly proportional to the delta mission availability. This results in that the choices of the VARI-METRIC model can be used to allocate the spare parts. The reduction of the repair lead-time can reduce the initial spare parts cost in this case with 39.76%, but it can only be realized by stocking component spare parts. The largest total initial spare parts cost is achievable by reducing the repair lead-time. The reduction of the repair lead-time is only allowable when Thales stocks components as spare parts. The component spare parts cost is much lower than the Line Replaceable Unit (LRU) spare parts. The maximal initial spare parts cost reduction is for a steady state model in this Smart-L case 39.76%. The reduction of the shipment cycle time reduces the initial spare parts costs, in this case 28.13%. The one month shipment cycle time and two months shipment cycle time is studied and how it influences the initial spare parts costs. The total initial spare parts cost is higher for the shipment time of two months than the total initial spare parts cost of one month. The initial spare parts costs reduction is in this Smart-L case 28.13%. The following recommendation can be presented based on this case study: Use the third procedure to allocate the spare parts for requested minimum mission availability target, because it generates in general higher mission availability solutions which are less sensitive to MTBF variations This procedure, which generates a solution with slightly higher costs, can cope better with the MTBF variations due to higher average mission availability solutions. Therefore the recommendation is to use the third procedure for allocating the spare parts to stock locations. Reduce the repair lead-time, because it reduces the initial spare parts costs In the systems of Thales there are a lot of printed circuit boards. These printed circuit boards are designed to be an LRU. In a PBL contract environment the inventory costs are at the expense of Thales. The recommendation is that costs can be saved by reducing the repair lead-time in a PBL contract environment. Reducing the repair lead-time can only be realized by stocking components as spare parts. Reduce the shipment time between customer’s site and the ships from two months to one month The total initial spare parts cost is higher for the shipment time of two months then the total initial spare parts cost of one month. Therefore, the recommendation is to agree in terms of the PBL contract a one month shipment time. The initial spare parts costs reduction is in this Smart-L case 28.13%.
Item Type:Essay (Master)
Faculty:BMS: Behavioural, Management and Social Sciences
Subject:50 technical science in general
Programme:Industrial Engineering and Management MSc (60029)
Link to this item:http://purl.utwente.nl/essays/65145
Export this item as:BibTeX
EndNote
HTML Citation
Reference Manager

 

Repository Staff Only: item control page