independent of the pipeline and sleeve materials. Centralising
jacking bolts are used to position the sleeve and then backed off
when the certite putty end seals have hardened, prior to epoxy
grout injection. Figure 3 depicts the layout of the epoxy end
sleeve and illustrates how any misalignment between the sleeve
and the carrier pipe may be accommodated in the design of the
end sleeve.
Grouted Tee fittings
The Grouted Tee is a novel method of installing a branch
connection onto a live pipeline without interrupting or adjusting
the pipeline product supply and
is designed to have a minimum
of 40 years design life (Figure 4).
Developed in 1997, the technology
is based on the well-established
epoxy filled repair sleeve. Welding
new connections onto live pipelines
is hazardous and in some cases
impossible due to high flowrates.
Since its initial application, the
technology has been developed
further for use on thin wall pipelines,
cast iron pipelines and subsea to
depths of up to 200 m.
As it does not require any onsite
welding, the installation process is
much safer and can accommodate
larger pipeline ovality than
traditional welded tees. Hot tapping
offers zero disruption to production
during installation and has been
designed to be quick and simple
to install compared to alternative
connections.
On completion of the Grouted
Tee installation, the new connection
can be coated with a corrosion
resistant material and/or fitted
with cathodic protection. Extensive
analysis and full-scale testing has
successfully addressed all technical
and safety issues relating to live
pipeline intervention using the
Grouted Tee.
The general layout involves
two half shells, the branched half
shell and the lower half shell. The
thickness of the shell is calculated
to resist structural and internal
pressure loadings that the Grouted
Tee will experience in operation.
The branched half shell has an
integrated saddle seal assembly,
which eliminates the need for
longitudinal and circumferential
seals, typical of current bolt-on
mechanical fittings. The bottom
half shell has a set of built-in spreader plates that are sized
accordingly to assist with the compression of the saddle seal.
The saddle seal is the main pressure containment component
that is energised when the two halves of the shell are bolted
together. All Grouted Tee fittings are sized to allow an even
gap between the bore of the shell assembly and the outside
diameter of the parent pipe. This annular gap is filled with the
same epoxy grout to that of epoxy repair sleeves, while the end
circumferential seal is made up from a two-part Certite putty,
which is fast curing and designed to contain the grout whilst in its
liquid state.
