Frictional performance of an O-ring type seal at
the commencement of  linear motion
Results of  investigation into the relationship between friction in the O-ring type seal
and gauge pressure at the commencement of  linear motion of a shaft are presented and
discussed. A number of different O-ring materials were studied and  the lowest friction
under dry conditions was found to be produced by a PTFE-encapsulated silicone seal.
The effect of~i  number of  lubricating fluids on friction  in the seal was also studied and the
results obtained are  included.4888
Keywords: O-ring seal; dry  friction; lubricated friction; friction coefficient
1. Introduction
For  applications such as  rotary process pumps  in chemical and petrochemical
industries or compressors  in the offshore oil exploration industry, a seal is a vital
element for reliable and safe operation.
A seal is basically a device for closing a gap or making a joint fluid-tight. When
sealing  takes place between surfaces that have relative movement, e.g. rotation of a
shaft relative to a housing, the seal is of a dynamic type. The majority of dynamic
seal types in general use can be classified as contact  seals.  The other category of
dynamic seals  is usually referred  to  as clearance  seals because  they operate with
positive clearance.  They are usually called mechanical  face  seals or  rotary  shaft
seals. Successful operation depends on achieving the right conditions at the inter-
face,  i.e.  the  faces  themselves must be  separated  by a  thin film of the  fluid con-
tained.
The  rotary  shaft  seal  is mainly used  in  pumps  and  compressors.  A  reliable
operation  of  the  seal  is  especially important  for  compressors  used  to  circulate
high-pressure  natural  gas  extracted  from  the North  Sea  [1-3].  The  principle  of
operation  of the  so-called dry gas seal is the balancing of aerostatic  and aerody-
namic forces  to provide a  stable, minimal running clearance. The Department  of
Mechanical  Engineering,  Brunel  University has  been  involved  in  the  develop-
ment of a new type of dry gas seal [4]. A  schematic diagram of the dry gas seal is shown  in  fig.  1.  It consists of two  faces. The dynamic  face  is held  rigidly to  the
drive  shaft by  the  dynamic carrier  and  locking  sleeve.  The  static  face  is  free  to
move  axially with  retaining  three  springs  and  O-ring  arrangement.  The  axial
freedom  is  required  to  allow  for  the  gap  between  seal  faces  to  be  established
under given operating conditions.
The O-ring  seal prevents  pressurised  gas escaping behind  the  static  face.  The
retaining springs force the static and dynamic faces to be in contact until the cor-
rect  operating  pressure  across  the  face  is  reached  and  separation  of  the  faces
occurs.  Typically, on  start up  of a  compressor  the  seal  faces are  in contact with
one  another  due  to  the  action  of  the  retaining  springs. Any  clearance  between
the  two  faces at  this point of compressor  operation would  lead  to  an unaccepta- O形密封件摩擦性能英文文献和翻译:http://www.youerw.com/fanyi/lunwen_1699.html