Page 40 - Gi_DecJan2020

igem news – yppc

cleanse has been in motion since FIGURE 4 TYPICAL PREFABRICATED ISOLATION JOINT
the commencement of the project,
requiring extensive survey work and steel rubber ‘o’ rings epoxy resin ductile iron
analysis to ensure accurate updates sealant
are recorded. An additional contractor
has also been engaged to carry out
line walking surveys and subsequent
pipeline test post mapping to a Google
Earth-style application. This will
provide the basis for future documents
depicting the full extent of each
end to suit stanton and
cathodic protection scheme. a) steel to ductile iron stavely stanlock fitting
Isolation
Isolation of the protected steel from
other metals has also proven to be a FIGURE 5 INSULATION FLANGE KIT
major challenge. In order for a cathodic
protection scheme to function, there insulating gasket
has to be effective isolation from other connection stud connection stud
and cable
and cable
structures which are not intended to be
protected by the scheme.
Lack of knowledge within the
business and lack of clarity in
procedural requirements has led to
instances of either incorrect isolation
installation or no isolation installation
during pipeline modification projects.

Typical isolation locations are found at:
Offtake points at above ground
installations
Connections to other pipeline systems steel washer
Dissimilar metal interfaces insulating washer insulating sleeve insulating washer steel washer
Connections to domestic, commercial
or industrial services
Gas conditioning plant Coating type and quality have occurred with scheme designs
Control instrumentation Soil resistivity and pipeline modifications, the North
Metal bridge crossings Surface area of the pipe within West network has realised significant
The cross section in Figure 4 depicts the scheme improvements in compliance and
the preferred method of isolation The pipeline coating type is often Cadent has successfully initiated a
between steel and iron pipe. However, known and the current requirement to project that will continue to add value
engineers and project managers have protect the scheme can be considered and reduce the risk of gas escapes.
often opted for a more fiscally attractive after calculating the surface area of
option in their designs. steel and conducting soil resistivity Acknowledgements
Figure 5 depicts the choice of tests. However, it has become apparent I would like acknowledge my mentor
isolation more common in the North that areas of diversionary work, new Bob Harrison and also Cadent for
West network. The disadvantage of connections to mains and polyethylene providing me with the opportunity to
insulation flange kits is that they should pipe replacement tie-in areas have lead this project in the North West.
only be used on above ground flanges often had a detrimental effect on the
that have not been used as a final tie-in coating coverage. Go to IGEMtv to watch Lance deliver his
prior to commissioning. In some instances, excavations presentation. Visit bit.ly/IGEM-tv
Final tie-in flanges can be slightly have uncovered completely uncoated
misaligned in a way that prevents the steel valves and flanges. This has
sleeves from inhibiting the metal to inadvertently led to larger quantities FIGURE 6 - UNCOATED FLANGE DISCOVERED DURING EXCAVATION
metal contact between the bolts and of anode requirements in order to
holes within the flanges. If they are ensure compliance.
used below ground and not adequately
coated, then they can be vulnerable Conclusion
to moisture ingress and ultimately Lessons have been learned and
become conductive, therefore rendering procedural modifications have been
the isolation ineffective. implemented to increase clarity. A new
process has been initiated to promote
Coating engagement between all relevant
The quantity of anodes required to stakeholders at the initial design stage
achieve compliance varies depending of mains replacement projects.
on a number of factors: Despite the historical errors that

40

14/11/2019 16:29
IGEMNews_YPPC.indd 3 14/11/2019 16:29
IGEMNews_YPPC.indd 3