Proper planning and control of spare parts inventory is a critical component of an effective asset management program .If the right parts are not on hand when needed for routine maintenance or repairs, downtime is prolonged. If too many parts are on hand, the enterprise absorbs excessive costs and the overhead of carrying the inventory.

There are tried and true strategies to manage spare parts in support of effective asset management, along with some that can be considered questionable, and a variety of new and innovative practices. Advanced enterprise asset management (EAM) solutions support the proper implementation of these capabilities. Following are examples of each.

ABC and XYZ analyses

The generally accepted 80:20 rule illustrates that approximately 80 percent of any storeroom’s volume is associated with only 20 percent of the items in inventory. It is important to pay extra attention to that critical 20 percent.

ABC and XYZ codes are commonly used to identify those parts. The codes are assigned based on value or quantity of stock movement, and each code will have an associated "upper limit." Highest value parts, for example those that cost more than $5000 each, can be assigned the ABC code of "A," and fastest moving parts can be assigned an XYZ code of "X."

Automatic replenishment

Automating the thought process related to reorders has generated proven savings. Suggested reorder functionality creates requisitions based on reorder points (ROP) and reorder quantities (ROQ) that are stored in the inventory record. Once inventory levels for a part fall below the reorder point threshold, a suggested reorder is placed for the reorder quantity, which in turn creates a requisition. This saves time and prevents the delays and errors that can occur with manual purchasing processes.

When a simple ROQ value is not enough, an economic order quantity (EOQ) algorithm can be used to calculate the right quantity of a spare part to purchase when replenishment is needed. The EOQ can consider volume discounts, the cost of placing an order, carrying costs, and other factors.

Vendor service levels

Capturing supplier service level data within the inventory record helps bring to light the most efficient, dependable, and cost-effective vendors. Preferred suppliers can be identified based on historical lead times, pricing, quality, number of short- or over-shipments, how often goods are received damaged, frequency of backorders, and other criteria. Preference can be given to these vendors in the procurement process.

Where used

A view of where a part is used, for example on which assets a certain ball bearing is installed, provides benefits to both the plant floor and storeroom. This view enables inventory personnel to understand how extensively a part is used throughout the operation, and helps the maintenance planners to determine the item number and quantity of parts installed on an asset.

Multi-stores capability

Taking where-used one step further, a multi-stores capability enables an enterprise-wide view of spare parts inventory that is stored at more than one warehouse or off site by a third party. In a multi-plant environment or when maintenance departments are distributed, visibility into inventory at the various storerooms permits monitoring of parts availability and service-level agreements across the enterprise as a whole or on an individual basis

Statistical Models for Spare Parts Management

• Forecasting Erratic Demand of Consumable Spare Parts
• Spare Parts Optimization Using Poisson Distribution
• Demand Forecast for spares
• Economic Order Quantity
• Spare Parts Usage Estimation Using ARIMA Model

Benefits

• Convince management to invest into correct level of spare parts
• Find the right level of inventory in seconds
• Identify slow moving stock and plan alternative strategies