To June, for her love and encouragement to keep me moving.

Copyright © 1986, 1997 by Butterworth-Heinemann. All rights reserved. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without permission of the publisher.

Originally published by Gulf Publishing Company, Houston, TX.

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Library of Congress Cataloging-in-Publication Data

Brown, Royce N.

Compressors : selection & sizing / Royce N. Brown.—2nd ed. p. cm.

Includes bibliographical references and index. ISBN 0-88415-164-6

1. Compressors. I. Title. TJ990.B76 1997





Compression Methods_

Intermittent Cycle Compressors_

Reciprocating Compressors. Rotary Compressors.

Continuous Compression Compressors _ Ejectors. Dynamic Compressors.

Basic Relationships_


Gas and Vapor_

Perfect Gas Equation.


Generalized Compressibility Charts.

Partial Pressure_

Gas Mixtures_

Specific Heat Ratio. Molecular Weight.

Specific Gravity_

Mixture Compressibility_

Mollier Charts, First Law of Thermodynamics. Second Law of


Real Gas Exponent. Power. Velocity Head.

Isothermal Compression.


3. Reciprocating Compressors_______48

Description___ 48

Classification. Arrangement. Drive Methods.


Compression Cycle. Cylinder Displacement. Volumetric Efficiency. Piston Speed, Discharge Temperature. Power. Valve Loss. Application Notes.

Mechanics_ 67

Cylinders. Pistons and Rods. Valves. Distance Piece. Rod Packing. Crankshaft and Bearings. Frame Lubrication. Cylinder and Packing Lubrication. Cooling. Capacity Control. Pulsation Control.

4. Rotary Compressors____93

Arrangements and Drivers.

Helical Lobe_ 95

History. Operating Principles. Displacement. Dry Compressors. Flooded Compressors. Flooding Fluid. Application Notes—Dry Compressors. Application Notes—Flooded Compressors. Casings. Rotors. Bearings and Seals. Timing Gears. Capacity Control.

Straight Lobe__121

Compression Cycle. Sizing. Applications. Mechanical Construction.

Sliding Vane____ 126

Compression Cycle. Sizing. Application Notes. Mechanical Construction.

Liquid Piston__130

Operation. Performance. Mechanical Construction.

5. Centrifugal Compressors _____________________132

Classification. Arrangement, Drive Methods.

Pe rformance_ 147

Compression Cycle. Vector Triangles. Slip. Reaction. Sizing. Fan Laws, Curve Shape. Surge. Choke. Application Notes.

Mechanical Design__ 188

Introduction. Casings. Diaphragms. Casing Connections. Impellers. Shafts. Radial Bearings. Thrust Bearings. Bearing Housings. Magnetic Bearings. Balance Piston. Interstage Seals. Shaft End Seals.

Shaft End Seals_ 211

ReNtrictive Seals. Liquid Buffered Seals. Dry Gas Seals. Capacity Control. Maintenance.

6. Axial Compressors_____224

Historical Background_____224


Performance__ 226

Blades. Compression Cycle. Reaction. Stagger. Curve Shape. Surge. Sizing. Application Notes.

Mechanical Design_ 247

Casings. Stators. Casing Connections. Rotor. Shaft. Blading. Bearings. Balance Piston. Seals. Capacity Control. Maintenance.

Objectives. Hydrostatic Test. Impeller Overspeed Test.

Operational Tests____407

General. Mechanical Running Test.

Objectives of Centrifugal Compressor Mechanical Tests___ 408

Rotor Dynamics Verification. String Testing. Stability. Helical-Lobe Compressor Test. Reciprocating Compressor Test. Spare Rotor Test. Static Gas Test. Testing of Lubrication Systems. Shop Performance Test. Test Codes. Loop Testing. Gas Purity. Sidestream Compressors. Instrumentation Test Correlation. Reynolds Number. Abnormalities in Testing. Field Testing. Planning. Flow Meters. Gas Composition. Location. Power

Measurement. Speed Conducting the Test.

11, Negotiation and Purchasing_____438

Procurement Steps. Supplier Partnerships.

Basic Data. Operations.

Writing the Specification__443

Specification Outline. General. Basic Design. Materials. Bearings. Shaft End Seals. Accessories. Lube and Seal System. Drivers. Gear Units. Couplings. Mounting Plates. Controls and Instrumentation. Inspection and Testing. Vendor Data. Guarantee and Warranty.

Coordination Meeting_____457

Installation and Startup____462

Commissioning the Compressor. Commissioning the Lube Oil System.

Overview. Robust Design.

Foundations. Suction Drums. Check Valves. Piping.

Compressors___ 474

Type Comparison. Reciprocating Compressors. Positive Displacement Rotary Compressors. Centrifugal Compressors. Axial Compressors.

Drivers_._ 47S

Turbines. Motors. Gears. Expanders.

Process. Experience.

General Comments. Gas Considerations. Operating Envelope.

Lubrication. Couplings.


Methodology. Manufacturing Tolerances.

About the time the first edition was written, the process industries, which represent a large part of the compressor market, were at a low ebb. As a result, the activity in the compressor world was almost at a standstill. Development at best was relatively slow. Currently, however, activity level has increased significantly. A look at the credit lines on many of the suppliers will tell of the many changes that have taken place. Even many of the companies whose names have not changed are now under different ownership than they were at the time of the first edition. Large investments have been made in facilities, in terms of new or remodeled factory buildings and the addition of new improved machine tools. Development funds are being expended and improved designs are becoming available. Management styles have changed and the theme of continuous improvement is quite prevalent. With all this activity, it seemed appropriate to offer an updated edition of this book.

Many of the readers of the first edition have commented that the book was easy to read. I have attempted to maintain that tone in this new edition. The major change to the book is the addition of a chapter on reliability. As in the other chapters, this one also leaves the high power statistics for someone else and instead uses a "common sense" approach. It probably has a "do and don't" flavor, which just seemed appropriate as I was writing it. Because the subject of reliability is so important and so much can be written about it, the chapter had to be limited to what I felt was the more pertinent information. I had to remind myself that the subject of the book was compressors, not just their reliability. It is hoped that a proper balance was obtained.

Another area that is addressed in the new edition is the dry gas seal. The subject of dry gas seals, which are now widely used by the industry, was expanded considerably in Chapter 5, and a discussion of dry gas seal systems has been added to Chapter 8. Also in Chapter 5, I added a section on magnetic bearings, which are emerging in the industry although they are not as quick to catch on. Chapter 8 expands the discussion of dry flexible element couplings to reflect current industry practice. The section on gear couplings was left because gear couplings are still used and I felt the information would provide some useful background.

I touched up some of Chapter 3 by reworking the valve section, and I hope it does a better job of describing the currently available valves, I also expanded the area of unloaders to more adequately cover the differ ent styles available to the industry.

Where current practice seemed to dictate I updated curves, and added a table in Chapter 4 to help with the sizing of the oil-free helical lobe compressors. Instrumentation was updated to take rod-drop monitoring of reciprocating compressors into consideration. Improvements in torque monitoring are also included.

In general, wherever I felt the organization of the material could be improved, I did it. The most notable of this are the changes to the testing chapter to aid in clarity.

Rover N. Brown

I would like to thank Alex and Linda Atkins of Alta Systems for coming to my assistance when I got overloaded with the chore of scanning my photographs and line illustrations. They helped get the illustrations organized and kept them in the proper order. Linda also helped with debugging the text and keeping the format consistent. Alex put the finishing touches on the figures and then put them on a CD Rom so they could be transported to the publisher. They were very flexible and made themselves available to fit my schedule.

I also want to thank Dan Beard and his son Sean for computer support and some tedious image editing.

Thanks go to Brown and Root for scanning the first edition, and for giving me an electronic form on which to build the revised edition. Thanks also to Buddy Wachel of EDI for giving me an assist at the reciprocating compressor acoustics, and to Susan Dally, Terryl Matthews, Rick Powell, Kelly Fort, Rich Lewis, Carl Fredericks, and Mary Rivers of Dow Chemical for their reviews of the revised chapters.

Finally, a sincere thanks to all the suppliers who provided material for the figures.

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