Maintenance spare parts are held to support planned maintenance tasks and to avoid or mitigate the risks associated with stockouts. For critical equipment, stockouts can result in lengthy asset downtime and production losses while spare parts are being replenished.
The Problem – Which ones to hold and how many?
The decision on what spares to hold and how many is therefore a very important one. Overstocking will result in waste, as valuable capital is tied up in inventories. Under stocking exposes the organisation to elevated risks which may result in significant production losses. To determine the optimum level for maintenance inventories therefore requires calculation, balancing the risk costs against holding costs over the life of the asset. The factors that enter into this calculation are as follows:
- Cost of the spare
- Re-order lead time
- Demand rate (or MTBF)
- Number of supported installations
- Asset configuration (standalone or duty/standby)
- Cost of downtime at each installation
- Cost of capital (discount rate)
- Remaining Life
The Solution – Optimisation using Isograph AWB software
To solve this complex problem requires a powerful modelling tool. Asset Dynamics Asia have teamed up with Isograph to offer their Availability Workbench (AWB) optimisation software. Isograph AWB uses a powerful Monte Carlo calculation engine to model complex inventory scenarios and determine the optimum level of spare holdings. Isograph AWB has a simple user interface, so its easy to learn and quick to generate results making it the ideal solution for taking the guesswork out of spares decisions. More information on Isograph AWB is available here.