Spare parts and METRIC

Question 1

What is a spare part?

Answer 1

An extra part used to replace a lost or damaged part of a product or machine

• Ensures operation of companies equipment –> continuous production

Question 2

What is preventive maintenance?

Answer 2

Maintenance is performed before the occurrence of a failure

Question 3

What is Mean down time (MDT)?

Answer 3

The average time a system, machine or equipment is not operating/active due to maintenance or failure

Question 4

Mentions the 5 different types of spare parts

Answer 4

1. generic parts: standardized and widely used parts
2. Specific parts: Custom parts for the plant/machine
3. Strategic parts: purchased with specific investments
   - critical to achieving long-term goals and maintaining competitive advantage
   Ex. turbine blade in a power plant
4. Repairable parts: Technically and economically repairable
5. Consumable parts: Cannot be technically/economically repaired

Question 5

Name 2 categories of repairable parts

Answer 5

Non-interchangeable: Are not replaced but required when they fail –> time-consuming!!

Interchangeble: When the part fails, it can be changed to a new temporary one and sent to the repair centre

Question 6

What is scrap rate?

Answer 6

The %v of materials that cannot be repaired or restored after failure

Question 7

What is the VED classification scheme?

Answer 7

Specifies the criticality of specific parts depending on how much damage their failure can cause to the system

1. Vital parts
2. Essential parts
3. Desirable parts

Question 8

What is the METRIC model?

Answer 8

Multi-Echelon Technique for Recoverable Item Control:

A method used in supply chain management to optimize the availability and repair of recoverable items (items that can be repaired and reused, like aircraft parts). It focuses on minimizing costs while ensuring operational readiness. Has a more holistic/process approach and focuses on multiple stages of the supply chain

The model uses Poisson distribution and also follows Palms theorem for demand forecasting:
- Helps analyzing the behavior of random events like repair time and failure, which can help optimizing spare part inventory

Question 9

What are the constraints of the metric model?

Answer 9

The METRIC model works only If Palms Theorem is applied, which gives the following assumptions:

1. Failures occur randomly and predictable
2. The system behaves the same overtime (steady state)

These assumptions may not always be realistic and the prediction of the spare part inventory may be inaccurate

Question 10

What is the difference between EOQ and METRIC model?

Answer 10

The METRIC model is used for managing several recoverable items, focusing on balancing availability and repair across multiple locations. It’s ideal for situations where parts are reused

—> Has more holistic approach: looks at the whole supply chain and focuses on several items with dependent demand

The EOQ model applies mainly to non-repairable items. It calculates the best order quantity to minimize inventory costs

—> Has a more product oriented, narrow approach: Looks at the economic order lot for one certain part of a supply chain and focus is on products with independent demand