Mechanical Seal Maintenance and Application Guide


Mechanical Seal Maintenance and Application

by EPRI


1 INTRODUCTION

2 GLOSSARY OF TERMS

3 TECHNICAL DESCRIPTION
3.1 Operating Principles and Basic Components of a Mechanical Face Seal
3.2 Major Design Variations
3.3 Multiple Seals
3.4 Seal Cartridges
3.5 Seal Chamber Design and Flushing
3.5.1 Seal Arrangements for Abrasive Applications
3.6 Closing Force
3.6.1 Balance Ratio
3.6.2 Pressure Distribution Between the Sealing Faces
3.6.3 Stationary Versus Rotating Seal Balance
3.7 Pressure Velocity (PV) Parameter and Limit
3.8 Temperature Considerations and ‘T Limit
3.9 Improved Seal Face Designs
3.10 Hydrostatic Seal Design

4 FAILURE MODES AND FUNDAMENTAL MECHANISMS
4.1 Introduction
4.2 Definition of Seal Failure
4.3 Industry Survey
4.4 Fundamental Failure Mechanisms
4.4.1 PV Limits Exceeded
4.4.2 ‘T Limits Exceeded, Causing Film Vaporization/Collapse
4.4.3 Inadequate Cooling
4.4.4 Transients Causing Excessive Seal Face Coning
4.4.5 Operation Away from Best Efficiency Point
4.4.6 Seal Misalignment/Premature Degradation of Primary and Secondary Seals
4.4.7 Excessive Out-of-Flatness (Warpage) During Operation
4.4.8 Seal Faces Too Perfectly Flat to Generate a Film

5 APPLICATION AND SELECTION RECOMMENDATIONS
5.1 Introduction
5.2 Selection Specification
5.3 Selection Data Sheet
5.4 Qualification Testing

6 CONDITION-BASED MONITORING GUIDELINES
6.1 Introduction
6.2 Typical Performance Data Logging
6.3 Seal Performance Parameters
6.4 Instrumentation
6.4.1 Temperature Gauge
6.4.2 Thermowells
6.4.3 Pressure Gauges
6.4.4 Alarm, Trip, and Control Switches
6.4.5 Pressure Switches
6.4.6 Level Switches
6.4.7 Level Indicators
6.4.8 Flow Indicators

7 TROUBLESHOOTING TO IDENTIFY CAUSE OF SEAL FAILURE
7.1 Introduction
7.2 Failure Diagnosis
7.2.1 External Symptoms of Seal Failure
7.2.2 Checks Before Dismantling
7.2.3 Checks During Dismantling
7.2.3.1 General Checks
7.2.3.2 Premature Failure Checks
7.2.3.3 Mid-Life Failure Checks
7.3 Visual Seal Examination

8 MAINTENANCE
8.1 Introduction
8.2 Installation and Operation
8.2.1 Seal Handling and Inspection
8.2.1.1 Packaging
8.2.1.2 Storage
8.2.1.3 Handling
8.2.1.4 Physical Checks of Mechanical Seals
8.2.1.5 Seal Rotating and Stationary Components
8.2.1.6 Seal Faces
8.2.1.7 Gaskets
8.2.1.8 Spring
8.2.2 Pre-Installation Equipment Checks
8.2.2.1 Shaft Straightness
8.2.2.2 Shaft Runout
8.2.2.3 Squareness of Stuffing Box
8.2.2.4 Rotational Balance
8.2.2.5 Shaft Bearing Clearances
8.2.2.6 Shaft/Sleeve Diameter and Surface Finish
8.2.2.7 Sleeve Hardfacing
8.2.2.8 Sharp Edges
8.2.3 Seal Installation Checks
8.2.3.1 Seal Dimensional Checks
8.2.3.2 Seal Cavity Dimensions
8.2.3.3 Compression Length Tolerance
8.2.3.4 Auxiliary Glands
8.2.4 Seal Removal
8.2.4.1 Safety
8.2.4.2 Failure Evidence
8.2.4.3 Seal Re-use and Inspection
8.2.5 Startup
8.2.5.1 Avoid Dry Running
8.2.5.2 Filtration
8.2.5.3 Venting the Stuffing Box



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2 thoughts on “Mechanical Seal Maintenance and Application Guide

  1. condino condino

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