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TECHNICAL
Stainless-steel piping
and crimp fittings
Stainless steel is typically considered an expensive solution; however, the
benefits of stainless steel in terms of longevity, quality, and maintenance
needs, show that it is a comparative solution.
By Arius Wantenaar
DESIGN CRITERIA
When designing a plumbing system, historically,
architects and engineers generally worked on the old
standards developed when galvanised and black mild
steel piping were in fashion.
Subsequently, copper tubing became very popular,
with good flow characteristics. This improved design
criteria, as dimensions were slightly smaller, but flow and
pressure losses were not negatively affected.
About the author
Arius Wantenaar is the
director of Stainless Piping
Utilities and has been
involved in various industries
with fluid reticulation systems
for over 30 years. He has
assisted in the establishment
of SANS standards for
stainless-steel pipes and
crimp fittings, and also
collaborated with various role
players, major consulting
engineers, and local
governments over the years.
With the introduction of plastic piping, wall thicknesses
were increased to handle the same pressure. External
diameters were increased to accommodate this, or
internal diameters were reduced. What really affects
system design was that the fittings, in many cases, had
significantly reduced internal bores. Therefore, in an
installation with a relatively high incidence where tees
and other fittings are required, this has an impact on
pressure and flow losses.
Stainless steel, however, has a thin tubing wall, and
crimp-on fittings can comfortably handle higher
pressures without affecting wall thicknesses. Also, the
same internal bore of the tubing is maintained with the
fittings, due to the flared-end design of the fittings, which
fit over the tube, and are then hydraulically deformed
onto the tube to give a consistently reliable joint. This
also maintains excellent flow characteristics.
This is an incredibly rapid process providing a permanent,
guaranteed leak-free joint, rated at a pressure of 16 bar,
with all the benefits that stainless steel provides. Pipe sizes
are available from 15mm diameter to 108mm diameter.
As a pipe reticulation system, it is highly user- and installer
friendly, hugely time saving, and resultantly cost-effective,
which tick all the boxes when efficiency is required.
Modern stainless manipulation techniques also mean
that stainless steel can be cut, welded, formed, and
May 2019 Volume 25 I Number 3
fabricated as readily as traditional steel and other
comparative materials.
EASE OF INSTALLATION
Training of the press-fittings concept is easily achieved,
even with the most junior of plumbers. Very few
components are involved and requires no technical
knowledge of welding, fluxes, solder, and so on.
Importantly, fittings are to be in accordance with
SANS11179, employing the press-fit concept. All fittings
are to be permanently marked with the manufacturer
name, diameter, and pressure rating PN 16.
The simple process of the stainless-steel pipe and
crimp-fitting design is:
1. Any tubing, or cut tubing, is to be deburred internally
and externally prior to inserting into the fitting.
2. Ensure the O-rings are in place in the fittings.
3. Tubes are to be externally marked at the face of the
fitting prior to assembly to ensure full insertion and
proper crimping to ensure a leak-free joint.
4. Crimping tools used are to be electrically driven,
hydraulic operation, and in accordance with fitting
manufacturers’ standards and specifications.
5. Provision is to be made for purchase of crimping
tools in your tender.
6. No solvents or oils are to be used on O-rings during
assembly of piping and fittings.
7. Pipe assembly to be loosely supported prior
to crimping to ensure the correct alignment is
achieved.
8. After crimping, perform a visual inspection that the
crimp has been executed correctly.
Tubing used is to be in accordance with SANS 1312
specifications, manufactured from material grade
4436(316), 4301(304), 4509(441), (444) and is
available in the following wall dimensions (size × wall
thickness):
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