Evaluation of glassfibre reinforced plastic pipe couplings for high pressure applications
Date
1992
Authors
Gutmayer, Johannes
Journal Title
Journal ISSN
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Abstract
This research was conducted in order to establish the
feasibility of manufacturing GRP pipe couplings for high
pressure GRP piping systems.The use of GRP pipes in high
pressure piping systems is desirable due to their light
weight, high corrosion resistance and their extremely low
friction factors.
To date no official standard exists that details the design of
GRP pipes or GRP couplings for high pressure applications in
excess of 7 MPa. In this report various existing steel and
GRP couplings are discussed. From this the GRP coupling
tested during the present investigation was developed.
Tensile testing of couplings was carried out at each stage of
the development phase in order to assess design modifications
and to obtain an overview of the behaviour of GRP couplings.
The test specimens were made from 400 rom long E-glass/epoxy
pipe sections which an internal diameter of 50 rom, a wall
thickness of 8 rom and a fibre orientation of ±55°.
The most suitable design suggested in this report consists of
a pipe with ? machined step and a flange laid up directly onto
the pipe. The load is transferred from the pipe to the flange
via adhesive shear stresses and through a mechanical
interaction between the pipe and the flange. The seal is made
with a hydrostatic "U"-type rubber seal, which is located on
the outside of the pipe. An outer split clamp clamps over the
flanges on adjacent pipes, thus holding these together. A
thin sleeve over the split clamp secures the clamp.
The maximum load bearing capacity for this coupling was 75 kN,
which is equivalent to an internal pressure of 22 MPa. Three
different failure modes occurred, viz. interlarninar shear of
the pipe, buckling of the fibres on the inside of the pipe and
compression of the fibres on the face of the step. The type
of failure depended on the location and depth of the step on
the pipe. Since failure occurred only in the pipe, it was
concluded that the pipe needs to be tailored at the ends in
order to achieve higher pressure capabilities.
A finite element. model was used to simulate one of the
experimental pipe/coupling configurations. This allowed
experimental and ·theoretical results to be correlated, and a
prediction of the coupling performance to be made.
Description
A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements
for the Degree of Master of Science in Engineering.
Keywords
PIPE, PLASTIC., GLASS REINFORCED PLASTICS., COUPLINGS., HIGH PRESSURE (TECHNOLOGY)., FINITE ELEMENT METHOD.