Designing for Reliability and Maintenance

Bruce Dean, CMRP
Manager, Design Engineering
Ramesh C. Gulati, PE, CMRP
Manager, Asset Mgmt. & Reliability Planning
AEDC / ATA
Arnold Air Force Base, TN 37389

Abstract

One of the key factors in asset/system performance is its reliability- “inherent reliability” or designed in reliability. Are we designing the system with reliability and maintenance in mind? The O&M cost, which is typically about 80% of the total life cycle cost of the system, becomes fixed –whether intentionally or not- during the early design phase. Are we specifying the reliability and maintenance needs in our requirements document before the design phase begins? The reliability & maintainability are design attributes that should be designed into the assets to minimize maintenance needs by using reliable components, simpler replacements and easier inspections.

Introduction

Having high reliability of assets /plants is essential to the success of any organization, particularly with respect to its overall operations and maintenance cost. Understanding reliability and maintenance and how they’re interrelated is important.

Reliability focuses on the ability of an asset to perform its intended function to support manufacturing a product or providing a service. Reliability terminates with a failure —i.e., when unreliability occurs. Unreliability results in high cost to the organization.

Maintenance is an act of maintaining, or the work of keeping the asset in proper –operational condition. Maintenance is a “field” action and may consist of performing maintenance inspection and repair to keep assets operating in a safe manner to produce or provide the designed capabilities. So maintenance is to keep assets in an acceptable working condition, to prevent them from failing, and if they fail, bring them back to their operational level effectively and as quickly as needed.

The Relationship Between Reliability and Maintenance Costs

Introduction

When we say Reliability, do we actually mean Availability? Under certain circumstances, the two are numerically the same, but that is only in a specific set of cases. 

Operational reliability - that is what we actually achieve in our Plants, is almost always lower than the intrinsic reliability that the Plants were designed and built to achieve. To bridge this gap, some managers look for silver bullets. Thus RCM, TPM, Six Sigma or some other process is selected to improve reliability performance. If these are not part of a well thought out plan, sustained results are hard to achieve. The plan will follow steps such as those described below.