TECHNICAL
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The local standard that was focused on at the last
quality workshop, was the SANS/ISO 4427. This is also
comparable with a similar series type standard used
internationally for U-PVC, namely ISO 1452. These
standards are typically divided into sections: the first
section covers general aspects and raw material,
followed by piping, fittings and systems, whilst the
second section focuses on providing guidance for the
assessment of conformity.
“It is important to emphasise that one section in the
standard builds onto the following. However, it is even
more important to ensure that a sound design code
is used, based on standards stating performance
requirements of the components. For our last training
session we referred to guidance from an international
standard, namely EN 805 Water supply - Requirements
for systems and components outside buildings. The details
from EN 805 offers value to the design engineer and helps
to understand what variables are of importance. It gives
clear guidelines with regards to the aspects that need to
be covered by new standards, when none are available,
and they need to be drawn up,” Venter explains.
During the presentation, the importance of not only
looking at the basic hydraulic design principles such
as pipe sizing, pumping costs and water hammer, but
also the dynamic conditions leading to the fatigue of the
components was explained. Venter also stressed that
although most design engineers have the basic elements
in place, they rarely consider the fatigue component.
It was also highlighted on the day and in the subsequent
discussions that took place, that the stress-strain curves
which are derived from the logarithmic curves are
only for static application and only relevant for water
at 20°C. As soon as any of these variables change,
the design approach needs to be adjusted by applying
the appropriate design coefficient or then temperature
de-rating or chemical de-rating, to align it with the
application.
“It is important to note that raw materials need to be
compliant to the Part 1 section, and only once it is
compliant can it be rolled over into manufacturing pipe.
It is also important to take cognisance of the fact that
current certification systems do not necessarily indicate
a quality product. It only indicates that the manufacturer
has the necessary capability to manufacture the product,”
he explains.
When looking at conformity assessment, certification only
forms one part of this process. The second component,
and which is also of extreme importance, is the quality
management of the product itself and also the processes.
Says Venter: “Looking at the guidelines for the
assessment of conformity, it is important to state that
when a product is manufactured to a standard (which
November 2019 Volume 25 I Number 9
that these system standards need to work in conjunction
with one another and should be combined with a sound
design, construction, operation process and procedures.
If any of these aspects are neglected, the life expectancy
of the system may be compromised. SAPPMA hopes that
by hosting these regular training sessions and workshops,
they will be able to demystify the understanding of these
standards and clarify how the one flows into the other.
Pipeline system components are appraised and supplied to nominated industry
standards under third-party product certification systems.
would be one of the components of the series
standard), it would have a section called the Product
Quality Plan related to the section. This would be pulled
through into your ISO 9001 Quality Management
System. When this is done in a way where we have
type testing, batch release testing, process verification
testing and audit testing, it will go a long way in
ensuring an ongoing conformance process.”
The importance of a proper procurement process
implemented throughout the total value chain was also
highlighted. As a minimum, it needs to cover sections
detailing the Specification, Evaluation, Surveillance and
Acceptance processes. It is also important to note that
the evaluation process of specific quality requirements
from the end-user needs to be communicated to the
contractors through specific quality specifications,
as their evaluation procedures and processes often
cannot be proven to align with the end-users needs.
All product delivered to clients (even if it bears the
certification mark) needs to be received via a well
thought through product quality plan and process.
“The supporting, final water test is often performed
on pressure pipe and is used to confirm that sound
construction procedures and processes were
followed and that no obvious product abuse took
place, no excessive leaks exist, and that little shoddy
workmanship exists prior to the sign-off of the system.
However, passing this test does not necessarily indicate
that the system will perform as designed,” Venter says.
Thermoplastic pipe system life is dependent on many
factors. If the design stress was used in relation to
the regression curve, the predicted pipe life would be
indefinite, not 50 years. As with other materials, the
life is dependent on manufacture, transport, handling,
installation, operation, protection from third party
damage and other external factors.
“It is also
important
to take
cognisance
of the fact
that current
certification
systems do not
necessarily
indicate
a quality
product. It
only indicates
that the
manufacturer
has the
necessary
capability to
manufacture
the product.”
Provided that pipeline system components are
appraised and supplied to nominated industry
standards under third-party product certification
systems, appropriate product receipt quality control
processes and provided pipelines are designed and
constructed correctly, then the likelihood of failure is
minimised. For correctly manufactured and installed
systems, the actual life cannot be predicted, but can
logically be expected to be well in excess of 100 years
before major rehabilitation is required. PA
www.plumbingafrica.co.za