Seals and Sealing Handbook, Fifth Edition
An introduction to the subject of sealing technology, this book provides an understanding of the issues involved and sufficient information to assist with achieving reliable and effective sealing.
TABLE OF CONTENTS Seals and Sealing Handbook, Fifth Edition
3.6: Clearance Seals
3.6 Clearance Seals
3.6.1 Introduction
Clearance seals are very widely used on rotary shafts. There are a wide variety of seal types which are discussed in the sections of this chapter. A very obvious problem with a clearance seal is that it does not in isolation provide a complete barrier to leakage. However, they are used for a number of reasons including:
-
Very low friction.
-
High speed.
-
Absence of wear, especially if operating in gas at high speed.
-
Capability to deal with contamination with minimal wear.
-
Provide an effective throttle or as part of a pressure breakdown for protection of a main contacting seal.
The seals may vary from quite simple, very low cost, high volume products to very highly engineered designs for turbo machinery and very high speed spindles.
3.6.2 Labyrinth Seals
As implied by the name, a labyrinth seal functions by providing a contorted path to inhibit the leakage. With a rotating shaft the seal can be designed to work by two methods:
-
Rotating radial faces can cause centrifugal separation of liquid or solids from air.
-
A series of restrictions followed by a clear volume creates expansion of a gas and hence reduces the pressure.
There are thus two main areas where labyrinth seals may be used. The first is for the protection of bearings in environments where liquid contamination is a problem and the second is as a pressure seal on turbo machinery.
3.6.2.1 General Purpose Bearing Seals
A variety of shields and simple moulded elastomer or...
Copyright Elsevier Ltd. 2007 under license agreement with Books24x7
