Operator Diagnosis of Equipment Operation

D. Mark CooperPrincipal Machinery EngineerLyondell Chemical Company

Channelview, Texas

Outline

Introduction

Equipment troubleshooting by an Operator

A troubleshooting guide for Operators

Development of the guide

Implementation

Summary

Introduction

In most cases, the first person to know about equipment problems is the operator.

Knowledgeable decisions regarding equipment operation and effective communication facilitates effective maintenance.

Lists of equipment operation abnormalities with potential causes covering the most common situations can assist operations with root cause analysis.

Equipment Troubleshooting by an Operator

Operators are around the equipment more than most other people.

One role of the operator is to evaluate current equipment operation.

If equipment operation is found to be outside of normal operating parameters, the operator must decide on the next course of action.

A Troubleshooting Guide for Operators

A troubleshooting guide assists an operator in determining the next course of action.

Operator uses the guide to determine a possible root cause.

Operator can use the guide to determine if the equipment can remain in operation.

Possible root cause from the guide can be input or referenced in work order descriptions to provide maintenance with additional insight into the problem.

Development of the Guide

The three steps for developing a troubleshooting guide for equipment are:

Develop a list of common abnormalities.

List the potential causes for each abnormality with a percent probability for each cause.

If possible, provide a solution or test for each potential cause. The test would be a method of determining the validity of the potential cause.

Example Troubleshooting GuideSEALLESS PUMP TROUBLESHOOTING (Canned motor) %

Chance Solution or testNOISY INTERNALLYPotential causes:

1 Cavitation 90%2 Low NPSH 80%3 Worn bearings allowing stationary and rotating parts to contact 75%4 Specific gravity change 50%5 Impeller rubbing casing (Axial or radial rub) 40%6 Specific heat change 30%7 Change in pumpage causing pump conditions to change.

NOISY EXTERNALLYPotential causes:

1 Low NPSH 90%2 Severe cavitation (excessive heat) 90%3 Worn bearings allowing strong metal to metal contact. 60%4 Liquid hammer 30%5 Solids inside of the pump.6 Loose on foundation7 Loose valve handles

NOT ENOUGH FLOWPotential causes:

1 Plugged suction strainer if there is one 90%2 Reduced NPSHA 90%3 Plugged discharge strainer if there is one (If separate from the pump.) 85%4 Wrong impeller diameter 85% Impeller diameter too small. Check discharge pressure.5 Plugged impeller 60%6 Discharge piping restricted in some way 60%7 Wrong direction of rotation (Most likely after recent motor change) 50% If three phase motor change any 2 leads and see if improves.8 Wrong pump speed 50% 1800 RPM motor when should be 3600. Not likely in can motor pump.9 Extra piping length added to the discharge or suction system of the pump. 40% Check the discharge pressure gauge. Should be normal not high.

10 Specific gravity change (increase) 35%11 Viscosity change 30%12 Solids in between rotor and stator wall slowing rotor 30% Check power and if low it can not be this.13 Discharge check valve on spare pump leaking through? 30% Check discharge pressure gauge on spare pump, if high tap check to seat.14 Drag slowing pump impeller. 20% Check the pump power, if low this can not be.

Implementation

The guide should be used as part of a broader training program on the design and operation of process systems.

As the guide is used, feedback on the accuracy and completeness of the guide is required.

Increases the accuracy of the document.

Captures repair experience in the document for future reference.

Summary

Troubleshooting guide is meant to document and preserve equipment troubleshooting history.

Use of the guide, along with training on equipment operation, can help reduce maintenance dollars.

Improving communication between departments

Improving repair accuracy

Increasing equipment operation knowledge.

Increased equipment operation knowledge can also reduce equipment damage caused by continued operation under abnormal conditions.