Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery

13Using Standby Machinery to Improve Process Reliability

By Robert X. Perez

Introduction

The goal of this chapter is to introduce readers to the concept of reliability modeling in processes using machinery. Reliability modeling methods are a proven way of predicting the availability and reliability of process systems made up of machinery and flow elements. Some common questions that arise when designing machinery installation are: 1) Do I need build redundancy into my machinery installations? and 2) If so, what is the most cost effective way to build redundancy into my installation? There are always tradeoffs between process reliability, initial capitals costs, operating complexity, and maintenance costs (see Figure 13.1). The right design configuration for your particular system depends on the cost of downtime, equipment, and maintenance. I will use Raptor, a reliability modeling tool, to illustrate the benefits and tradeoffs of different machinery sparing configurations.

Basic Reliability Theory [1]

Before we begin talking about reliability modeling, we need to understand the difference between system availability and equipment reliability. Availability is a metric that measures the probability that a system (or equipment) has not failed or is undergoing a repair action when it needs to be used. This usually equates to the financial performance of the system or process. Availability is defined as: Uptime/Total time (Uptime + Downtime). For example, let’s say we want to ...