Dedicated Solutions for Exceptional Pipe Materials

REHABILITATION
REHABILITATION
Dedicated Solutions for
Exceptional Pipe Materials
Photo: STRAUB Werke AG
Considerations for the selection of adequate
joining and repair products for GRP and
concrete pipework
By Sascha Radosevic and Jan Treiber
The article shows how to realise pipe connections and repairs of GRP-, concrete and fibre
cement pipes. These pipe materials are more or less uncommon in the water supply. Their
special characteristics and typical joining methods will also be illustrated.
Piping network operators using these pipe materials may also be aware of the standard
connectors often not to be very useful in case of maintenance and repair. Therefore, great
importance should be placed on the analysis of the pipework. The authors display key factors for the professional technical evaluation of the pipelines, as well as they show current
„trench-proven“ solutions for the issues mentioned.
Some pipe materials are rarely to be found in
the water supply. That’s why piping network
operators should come to an understanding
with these materials. In case of maintenance
and repair they could then react correctly and
in time. To avoid disagreeable experiences
it is highly recommended to dispose of the
know-how of leading manufacturers of pipe
joining and repair technology.
Differences...
Fibre cement pipe
30
■
Soaking of the pipe surface when it is in
permanent contact with the ground water
A lot of joining methods have been developed for fibre cement pipes [3]. There is not
enough space to name all of them. Generally, the plain-ended and calibrated pipes are
joined together with push-on couplings. The
current types are:
■ SIMPLEX-coupling
■ RINGTITE-coupling
■ REKA-coupling
The pipework inventory of these pipes mainly
consists of asbestos cement (AC) pipes which
were used until the early 1990s, and their
asbestos free successors.
The REKA type, which features an easy installation as well as a reliable sealing, is most
commonly used. The REKA design was taken
over for today’s GRP couplings.
For maintenance and repair works on AC
pipes, special prevention measures [1] have
absolutely to be observed!
Glass-fibre reinforced plastic pipes
(GRP)
Fibre cement pipes where used in the water
supply since 1930 [2] in nearly all diameters.
Many of these pipes are still in use without
difficulties today. Damages caused by sediments or abrasion are extremely rare to be
found. Frequent cases of damage are:
■ Leaky lugs caused by brittle gaskets
■ Leaky lugs caused by stress and/or angular deflection
■ Shell break-off caused by punctual stress
and tension
Used primarily as a substitute for the asbestos cement pipes, GRP pipes have established
for various applications in the water supply.
Their main advantages are that they can be
produced in nearly every required bore and
also would withstand a high working pressure
even in greater diameters. GRP pipes consist
of glass fibre, (polyester) resin and reinforcing
materials like limestone or quartz. Typically,
GRP pipes are used in diameters larger than
DN 300 (Figure 1).
Fig. 1: GRP pipe (OD 924 mm, PS 23 bar)
with STRAUB-FLEX coupling
It is important to distinguish between
■ centrifugally cast GRP pipes (e.g. HOBAS)
and
■ filament wound GRP pipes (e.g. FLOWTITE).
This article does not deal with particular properties of these manufacturing technologies
but some differences are worth knowing:
■ centrifugally cast GRP pipes have an absolutely plain outside and therefore a clearly
defined external diameter
■ filament wound GRP pipes are coiled
around a core which leaves their inside
plain and glossy
■ centrifugally cast pipes are made by using
chopped glass fibres, filament wound
pipes by using endless glass fibre roving
■ filament wound GRP pipes can be suitable
for higher working pressure
When laying new pipe schemes, GRP pipes
are usually connected with REKA-couplings.
If necessary, pull-out resistant joints working
with shearing rods are provided.
Damage caused by corrosions cannot be
found with GRP pipes. They offer a high
structural stiffness and mechanical strength.
Facing a punctual overload, single fibre layers
would release from the composite matrix, a
process better known as delamination. Leakages which arise from delamination appear as
areas of “transpiration”, where small amounts
of medium drip out of the pipe wall.
Pre-stressed concrete pipes
In the field of water supply, pre-stressed concrete pipes are mostly used in nominal diameters from at least DN 800. For example, the
backbone lines of some important European
water suppliers [4] are made of pre-stressed
concrete.
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REHABILITATION
The pipes are manufactured by casting concrete all around a pre-stressed wire mesh.
Different types of pipes can be found, normally labelled by the producer’s name. Some
examples:
■ DYWIDAG-Sentab-pipe (DS)
■ Brespa-pipe
■ Zueblin-pipe
■ Arkel-pipe (AR)
■ Bonna-pipe (BO)
These pipes differ in the wire mesh design as
well as in the wall thickness, the outside diameter and the joining method. Aside the “classical” bell-and-spigot type, a lot of constructions
with different functionalities can be found.
bar)
Global Data
Pipe material
e.g. concrete / GRP / AC...
Coating type
e.g. bitumen / paint...
Measured values
Nominal diameter DN [mm]
Often to be found in the pipewokr plans; relevant for
hydraulics engineering.
Typical damages found with pre-stressed
concrete pipes are leaky lugs or corroded
wires. Leakages of the bell-and-spigot joints
are mostly caused by brittle gaskets and/or
ground settlement. Rehabilitation can be
done in different ways:
■ Lug renovation by using internal sealing
devices (e.g. AMEX [5])
■ External sealing of the lug gap
■ Rehabilitation of a whole pipe section
using a polyethylene liner [6, 7]
Wall thickness s [mm]
Important value for the pipe statics and the pressure
resistance.
Other nameable damages are circular cracks
due to corroded wires [8] or leaky butt joints.
Misalignment h [mm]
Extremely important fo repairs and when reinstalling pipe
sections!
...and similarities
Even if all the named pipe materials may seem
to be quite different, they have one thing in
common: used as pipelines, they are mostly
the backbone mains of the water supply system. Disruptions as a result of maintenance
and repair are always time-critical and should
be avoided if possible.
The above mentioned typical pipe joints used
with new-laid schemes are often disadvantageous for tie-in sections, maintenance and
repair because they can neither be slipped
over the pipe nor can they be installed into
the existing pipework.
Outside diameter d [mm]
To pinpoint d always means to regard the ovality and the
circularity of the pipe!
Angular deflection α [˚]
Extremely important for repairs and when reinstalling pipe
sections!
Additional parameters and factors
Ovality
Mostly occurs on pipes in larger diameters.
Circularity
Pipes made of GRP, pre-stressed concrete and fibre
cement rarely are truly round!
Collect data!
Especially the lack of key information will allow the “worst case” to come to pass. The
authors are often confronted even with larger
utilities or network operators not understanding enough about the state and properties of
their pipework. Some even do not dispose of
important data which leads to a certain hectic
activity in the event of damage.
Specific values of the really important pipelines should be well-known or determined at
every opportunity. The following pages display
a checklist with important evaluation parameters for pipelines. These parameters allow to
estimate correctly the status quo. In case of
maintenance and repair they only have to be
completed by the local circumstances (e.g.
soil conditions, accessibility).
Pipe surface conditions
Spalling of concrete and local damages eventually have to
be smoothed out!
Axial elongation and/or movement
Temperature difference will affect the length of the pipes!
Dimensional accuracy
The external siameter of a pipe section – in particular
when made of concrete –may rather vary!
Table 1: Check-list of assessment factors for pipes
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Photo: STRAUB Werke AG
REHABILITATION
Fig. 2: Cross section of the STRAUB-FLEX gasket
The STRAUB product range offers flexible couplings and repair couplings up to an outside
diameter of more than 3500mm. Depending
on the application type, the products STRAUBFLEX or STRAUB-OPEN-FLEX can be selected
to solve the specific problem. They are manufactured stepless for any existing diameter
and will therefore “fit like a glove”.
The above check list only displays the factors
relevant for the daily practice and does not
claim to be complete. In the particular case it
will be necessary to go further into the details,
e.g. to analyse the pipe statics.
On the market, a lot of different products are
offered to manage maintenance and repair
of GRP-, concrete and fibre cement pipes.
Coupling systems which are adapted for the
requirements mentioned above cope with
these tasks. Aside the product features the
know-how of the coupling manufacturer is of
utmost importance.
The gasket of the STRAUB couplings (Figure
2) provides a pressure-supported sealing
principle, compensates for tolerances and is
damping noise, vibration and movement. It ensures a long-term and leakage-free sealing on
any pipe material. STRAUB couplings are optimised for their distinct type of use in extensive
test-runs at the in-house R&D laboratory. The
system pressure (PS) plays an important role
for the dimensioning of the coupling.
Piping network operators taking responsibility
for their assets very often opt for pipe couplings made by STRAUB Werke AG in Switzerland. STRAUB offers a 40-year experience
and leading know-how in pipe joining tech-
For example, STRAUB-OPEN-FLEX couplings
(Figure 3) can be wrapped around a damaged pipe; this avoids the cutting of the
pipe and allows a quick and durable repair.
STRAUB-OPEN-FLEX is frequently used to
Fig. 4: STRAUB-OPEN-FLEX replaces an untight
REKA-coupling
32
Fig. 3: Repair realised with STRAUB-OPEN-FLEX
replace untight REKA-lugs (Figure 4) or to
tighten circular cracks on concrete pipes.
As even STRAUB couplings would not solve
any existing problem, customised and dedicated solutions will be developed if required.
In the event of damaged pipe surfaces, an onsite method to achieve a smooth pipe surface
was generated in company with the specialty
chemical producer SIKA AG.
Sometimes the corrosion resistance of the
stainless steel coupling could be an important
issue. To select the proper steel grade, the
soil would be classified. Based on this classification, the choice is then made between the
grades 1.4301 (AISI304) or 1.4571 (AISI316).
An anti-corrosion-coating could also be added
when necessary.
Photo: STRAUB Werke AG
Photo: STRAUB Werke AG
Facing the choice!
Photo: STRAUB Werke AG
nology together with numberless worldwide
references.
At first glance the multitude of parameters
and factors seems to be exaggerated. Those
who have experienced a construction project
being delayed or even interrupted by the unawareness of these parameters really know
about their significance.
Fig. 5: Connection of a stainless steel reducer with GRP pipes
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REHABILITATION
Examples
The below-mentioned practical examples
highlight some cases of troubleshooting with
STRAUB pipe couplings.
Fig. 6: Flexible
connection of a
concrete pipe and
a concrete manhole
Integration of a stainless steel
reduction into a GRP pipe system in
an inspection chamber
Photo: STRAUB Werke AG
On the Zurich airport, two GRP pipes of
DN 250 and DN 400 had to be connected
with a s/s reduction in a chamber. The reduction should be easily assembled and disassembled for inspection purposes, even in
the confined space. It was connected to the
GRP pipes by using STRAUB-FLEX 2LS/LU
couplings (Figure 5) which perfectly met all
the demands.
Installation of a concrete chamber
with a cardan joint
If pipe sections or especially chambers are
added to a concrete pipe scheme subsequently, uneven soil compaction often will
cause certain ground settlement. In Austria,
the extension of a rainwater retention pipe
system necessitated the installation of several manholes. To avoid severe damages a
cardan joint realised each with two STRAUBFLEX 3LS couplings was chosen to connect
the manholes to the existing pipework (Figure 6).
Adjusting diameter tolerances and
ovality
Existing pipework as well as new-laid schemes
can give reason to prepare the pipe surfaces
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Meeting the most stringent of requirements is what we
do every day. We focus our full attention on ensuring
that you obtain the right solutions for your pipe couplings. Your demanding, specialized problems are precisely where you can rely on our long years of experience
and expertise: in support and consultancy, handling
technical issues, engineering, project supervision and
documentation.
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More information from: Straub Werke AG, CH-7323 Wangs, Switzerland
www.straub.ch, Tel.: Germany: +49 (0) 621 486 2907
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REHABILITATION
be installed. A special 2-compound filler was
therefore developed together with SIKA AG.
[7] Treiber, J.: LinerGrip connectors for thin walled PE
liner, 3R International(2007) Nr. 3, p. 140 et sqq.
Conclusion
[8] Baumgartner, F.: Spannbetonrohre und -leitungen: ein Erfahrungsbericht, energie|wasserpraxis (2006) No. 7/8, p. 24 et sqq.
The STRAUB product range and the experienced STRAUB team offer the solution for maintenance, replacement, re-installation and repair
of GRP-, concrete and fibre cement pipes.
According to the complexity of the issue it is
absolutely recommended to get in contact with
the STRAUB application support team on time.
Internet sources:
·
Homepage of STRAUB Werke AG: www.straub.ch
·
SIKA specialty chemicals: www.sika.com
Authors:
Photo: STRAUB Werke AG
Literature
[1]
TRGS 519: Asbest Abbruch-, Sanierungs- oder
Instandhaltungsarbeiten, edition January 2007
Sascha Radosevic
STRAUB Werke AG, Wangs,
Switzerland
[2] Huenerberg, K.: Das Asbestzement-Druckrohr,
Berlin: Springer-Verlag, 1963, p. 4
Fig. 7: 2-component filler to level the diameter
tolerances of steel pipes DN 3500
at the junction. The pipe wall would either be
cylindrically turned or a levelling layer would
be applied. In this particular case (Figure 7)
the diameter tolerances and the ovality of a
steel pipe DN 3500 had to be equalised before
the STRAUB-OPEN-FLEX 3X coupling could
71027-IFATCH08-Anzeige-quer.qxd:Layout 1
[3] Huenerberg, K.: Das Asbestzement-Druckrohr,
Berlin: Springer-Verlag, 1963, p. 356 et sqq.
Phone: +41 81 7254173
E-mail: [email protected]
[4] Z.B. Zweckverband Landeswasserversorgung,
Stuttgart: www.lw-online.de; Zweckverband
Bodensee-Wasserversorgung, Stuttgart: www.
zvbwv.de
Jan Treiber
FRIATEC AG, Mannheim,
Germany
[5] For further information see: www.amex-10.de
[6] Haakh, F.: Sanierung einer Spannbetondruckleitung DN 1500 mittels HDPE-Inliner, GWF
Wasser/Abwasser (2007) No. 5, p. 375 et sqq.
14.12.2007
10:31 Uhr
Phone: +49(0)7551/301041
E-mail: [email protected]
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