Dynamic behaviour of rotary mechanical seals
This thesis covers both experimental and computer investigations
into the dynamic behaviour of mechanical seals. The
literature survey shows no investigations on the effect of vibration
on mechanical seals of the type common in the various
process industries. Typical seal designs are discussed.
A form of Reynolds' equation has been developed that permits
the calculation of stiffnesses and damping coefficients
for the fluid film. The dynamics of the mechanical seal floating
ring have been investigated using approximate formulae, and
it has been shown that the floating ring will behave as a rigid
body. Some elements, such as the radial damping due to the
fluid film, are small and may be neglected. The equations of
motion of the floating ring have been develofed utilising the
significant elements, and a solution technique described.
The stiffness and damping coefficients of nitrile rubber
o-rings have been obtained. These show a wide variation, with
a constant stiffness up to 60 Hz. The importance of the effect
of temperature on the properties is discussed. An unsuccessful
test rig is described in the appendices.
The dynamic behaviour of a mechanical seal has been investigated
experimentally, including the effect of changes of speed,
sealed pressure and seal geometry. The results, as expected,
shorf that high vibration levels result in both high leakage and
Computer programs have been developed to solve Reynolds'
Equation and the equations of motion. Two solution techniques
for the latter program were developed. The unsuccessful technique
is described in the appendices. Some stability problems
were encountered, but despite these the solution shows good
agreement with some of the experimental conditions. Possible
reasons for the discrepancies are discussed.
Various suggestions for future work in this field are
given. These include the combining of the programs and more
extensive experimental and computer modelling.