Note: Descriptions are shown in the official language in which they were submitted.
1- 1 336663
Process for sealinq damaqed pipes.
The invention relates to a process for sealing damaged
or faulty pipes and to an apparatus for performing the
process.
The sealing of damaged pipes, particularly sewer pipes
has its own special problems. Several factors occur tog-
ether if a damaged sewer has to be repaired. The damaged
points can merely be fine cracks, which are just large
enough to leak, but can also be arm-thick breaks which
lead to an unhindered passage of the sewer content into
the surrounding ground. Usually these damaged points
are underneath a sludge layer and are very much exposed
to the wet. Sewer pipes, which in certain circumstances
can have a man-high width, are usually difficult of access
or inaccessible to humans, even in the case of large dia-
meters. Without exception, it is also cold in the under-
ground sewers. The medium is influenced by methane and
other gases. In addition, generally only the obvious
damage (leaks) can be detected, whereas the preliminary
stages which can grow so as to constitute visible damage
points are not readily detectable. Therefore shortly
after repairing a sewer, it can again have leaks subseq-
uently formed at such non-detectable points.
In order to obviate the aforementioned problems, a number
of procedures have been developed enabling such pipes
to be repaired. However, they have only lead to a dis-
placement of the problems. Instead of the damaged points
being observed and repaired by a human, this is now done
by machines, which are also susceptible to damage. Such
machines e.g. drill the damaged points found and backfill
them with synthetic resins (e.g. W0-86/03818) or another
apparatus is used for priming and in this way sealing
the damaged point (W0-86/04975). Another procedure involves
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the virtual replacement of a complete pipe section with
the damaged point or points by drawing in a resin-
impregnated tube, which is inflated in the damaged pipe
and subsequently cured, e.g. according to EP-0 082 212,
DE 35 13 956 and W0-87/04226.
All these methods use hardenable synthetic resins (resin
systems) and the basic problem in connection therewith
is their curing. In the medium in which such synthetic
resin systems must cure or completely harden is
encountered dirt, wet, cold, constricted conditions and
other unfortunate circumstances, i.e., in no way ideal
conditions to reliably and permanently obtain a hardened
resin layer with a long service life.
The problem of the present invention is to provide a
process for repairing pipes, which can be simply used,
which requires no complicated mechanical equipment and
which leads to continuous pipe castings, which rapidly
and reliably completely harden and which in a relatively
short time can be used again, whilst having long service
life characteristics. The necessary apparatus must be
inexpensive and simple to operate and maintain.
Various aspects of this invention are as follows:
Process for sealing pipes, particularly sewer pipes, by
applying a resin system to the inner surface of the
pipe, characterized in that the resin system to be used
is a two-component, hardenable polyurethane resin system
and that in a preparatory process step the inner surface
of the cleaned pipe is treated with a water-active
component of the used resin system.
1 336663
.
2a
Apparatus for lining pipes, particularly sewer pipes,
according to the process set out hereinabove, which can
be drawn through the pipe to be lined, characterized in
that apart from a mixing chamber and a plurality of
casting or spraying nozzles it has a jacket pipe, which
forms an extension and serves as a forming means for a
zone in drawing direction behind the apparatus, in which
the resin is hardening, and can for this function be
centered in the pipe to be treated.
Various embodiments of the invention are discussed
hereinafter with respect to the following drawings.
Fig. 1 shows in cross-section a sewer pipe laid in
the ground, which has a insulating
intermediate layer formed from a foam resin
and a bearing hard, smooth and impermeable
epoxy resin inner layer. Compared with the
size of the sewer pipe, the layer thicknesses
have been greatly exaggerated. In reality the
thickness of the
- _ 3 _ l 3 3 6 6 63
intermediate layer is preferably 0.5 to 1.5 cm
and that of the bearing inner layer preferably
0.5 to 1.5 mm.
Fig.2 shows in longitudinal section a sewer pipe and
diagrammatically an embodiment of an apparatus
for applying the insulating intermediate layer.
The apparatus in which the resin components
are brought together, mixed and injected, draws
or drags a shaping pipe with it, which forms
a circular gap between the mould and the sewer
pipe, which is filled with curable foam. The
shaping pipe is in multisection form and adapts
to any pipe bends.
The resin systems (generally polyesters) used for repairing
the faulty or damaged pipes are generally thermosetting,
so that adequate heat energy must be supplied to the resin
mixture in order to allow the complete chemical hardening
to take place. The damaged pipe (e.g. wetted concrete)
together with the soil surrounding said pipe forms such
a large heat sink behind the resin layer to be hardened
that only with considerable effort is it possible, if
at all, to supply sufficient thermal energy to cure the
resin, so that e.g. the necessary strength and/or long
service life can be obtained.
Thus, in one of the aforementioned prior art examples
the heat is supplied to the resin system to be hardened
by water, which has a high specific thermal capacity,
so that the tube which has just been resined must be inverted
over the sewer pipe, because hardening cannot take place
in an aqueous medium.
Although water is a sufficiently good energy carrier and
is also inexpensive, other methods have been proposed,
1 336663
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namely supplying the energy by UV-radiation to the resin
system, which can only be in polyester form. Thus, resined
tubes have been inflated in the pipe and subsequently
irradiated with UV. UV-hardened resins suffer from the
disadvantage that they more easily become brittle and
are more readily attacked by bacteria. Pipes treated
in this way and inserted in damaged pipe systems will
not have an adequate service life. In addition, the costs
for obtaining completely satisfactory radiation hardening
are high.
A further possibility consists of the curing of a harden-
able resin with gases, to which is added a hardening comp-
onent. This can take place at the same time as the pumping
up of the tubular carrier for the resin system introduced
into the sewer. The hardening gas is allowed to flow
through the resin-coated tube until curing has taken place.
However, gas hardening only makes it possible to obtain
thin coatings, whose strength is often inadequate in the
pipe. The gas layer cured on the surface acts as a barrier
between the hardening gas and the underlying resin material
to be hardened.
This lead to the idea of producing for the resin system
used for providing the strong pipes a medium in which
problem-free curing can take place, leading to a wall
(pipe) structure, which has the necessary strength. As
the curing is chemically complete, such a resin layer
will also achieve the necessary service life.
Between the resin layer forming the inner, new sewer pipe
and the aforementioned heat sink outside the resin layer
to be hardened is placed an insulating layer, i.e. an
intermediate layer, which keeps away dirt and wet and
which forms a barrier against ~e passage of heat energy.
Apart from an adequate mechanical strength, this insulating
intermedlate layer must form a chemically adequately good
~ _ 5 _ 1 3 3 6 6 6 3
substrate, so that a hard, resistant resin layer is formed
thereon. In order to realise this, it is necessary to
find a material satisfying all these requirements and
which also can act as an intermediary between the outside
world and the protected medium, whereby it is compatible
with such an outside world of dirt, wet, microbes, etc.
The material is preferably a polyurethane resin.
This specific problem was also solved by the invention
described in Swiss Patent Application 01849/88-7. The
latter deals with the complete problem on the basis of
a new idea. For the resin system to be used for forming
the desired strong pipes is created an environment, where
a problem-free curing can take place. Thus, as curing
is chemically complete, the applied resin layer will also
have the requisite service life. Between the resin layer
forming the inner, new sewer pipe and the said heat sink
outside the resin layer to be hardened, is placed an insul-
ating layer, i.e. an intermediate layer, which keeps away
the dirt and wet and forms a barrier against the passage
of thermal energy. Apart from an adequate mechanical
strength, this insulating intermediate layer must also
form an adequately chemically good substrate to enable
a had, resistant resin layer to form thereon. In order
to achieve this, it was necessary to find a material ful-
filling all these requirements and, as the intermediary
between the outside world suitable for the resin lining
and the shielded medium for applying the resin coating,
must also be compatible with such an outside world of
dirt, wet, microbes, etc. This material is preferably
a polyurethane resin.
The following procedure is adopted for repairing leaky
sewer portions. The pipe to be repaired, whose leaky
points have been detected beforehand, is washed out accord-
ing to a known procedure. Following a basic drying, the
still wet pipe (which must not have any water puddles
1 336663
-- 6
and these should be sucked off if necessary) is completely
foamed in a spraying process with a polyurethane resin
rM
system, e.g. o~ type Polylite VP-626 RG30/8664. The com-
ponent Polylite VP-626 RG 30 contains polyether polyols
and the component Polylite 8664 contains a reactive iso-
cyanate. The mixing ratios can be gathered from the data
sheet and instructions provided by the manufacturer, as
can the mixing and foaming requirements.
By using a corresponding foam spraying machine, this resin
system can be applied vertically and horizontally overhead
to particularly difficult surfaces, as well as in cavities
therein. As stated, this resin system contains reactive
isocyanate, so that contact with the skin, eyes and clo~ing
must be avoided. Mechanical spraying taking place in
remotely controlled manner without any direct human assist-
ance is very advantageous here. When working or handling
these substances protective goggles must be worn and possibly
also protective gloves and a respiratory mask.
The indicated resin system is self-foaming at ambient
temperature. It is possible as a result of the short
cream time and tack-free time to insulate particularly
difficult surfaces in a very short time. Despite the
low density, the foam has good mechanical characteristics.
Compared with its weight, the cured foam has a high strength
and excellent insulating characteristics.
Such a resin system leads to an over 90% closed-cell layer
with a heat transfer coefficient of 0.015 to 0.025 kcal/
mhC, which is completely adequate for the 0.5 to 1.5 cm
thick layer required here. The cream time is 2-3 sec
and the tack-free time 10-15 sec., whilst the ideal mixing
temperature if 20C. The compressive strength of the
cured foam is 2 kJ/m2, so that further processing or working
within the pipe structure is readily possible. The short
curing time, which can be assisted by introducing hot
1 336653
-- 7
air, makes it possible with an apparatus of the type described
hereinafter to achieve a pipe coating speed of up to approx-
imately 2m/min, which is a very satisfactory.
The further working in the now insulated sewer consists
of applying a further resin layer, the actual "pipe",
which is now sprayed onto the insulating layer. Preference
is given to the use of an epoxy two-component resin, e.g.
Araldite, which even in the form of a thin coating of
approximately 0.2 to 1.5 mm forms a sealing insert with
the necessary stability. As this resin system is applied
to the previously formed, insulating substrate, it is
subsequently possible to thermoset in problem-free manner,
e.g. with heated air. The supplied air is not then lead
off into the environment, being instead stored in the
resin, so that the entire energy is available for hardening
purposes. This second resin layer is then the mechanically
strong, sewer-sealing layer, which comes into directe
contact with the content carried in said pipe.
If necessary, a further, final layer of the same resin
material with a different viscosity can be applied, in
order to make the surface even more fine-pored and smoother
from the flow standpoint, whilst at the same time increasing
the pipe thickness.
Fig.1 diagrammatically shows in cross-section a sewer
pipe 1 in the ground 4 and which is generally formed from
thoroughly wetted concrete, which has a foam resin insulating
intermediate layer 2. The foam resin, a PUR, after a
certain pretreatment of the basically dried and still
moist to wet concrete surface has an adequate adhesion.
A description of this pre-treatment will be given herein-
after.
1 336663
_ - 8 -
A bearing, hard, smooth and impermeable epoxy resin inner
coating 3 is applied to the intermediate coating and said
substrate is chemically and physically suitable for the
connection. The coating thicknesses have been exaggerated
compared with the sewer pipe. In reality the intermediate
coating is preferably 0.5 to 1.5 cm thick and the bearing
inner coating preferably 0.5 to 1.5 mm thick.
Everything now depends on the flow requirements within
the sewer. If for flow reasons importance is attached
to a very smooth and uniformly rounded wall, then an injec-
tion apparatus can be combined with a shaping pipe, as
represented e.g. in conjunction with Fig.2. As the PUR
firmly adheres to the substrate, i.e. is very tacky, said
shaping pipe must have surface characteristics such that
there is no firm adhesion of the resin. It is most advan-
tageous to carry out teflonization (PTFE) of the pipe
surface or a PTFE coating. If the uniform rounding is
not essential, then an injection apparatus without a shaping
pipe can be used.
Preferably working takes place without a shaping pipe.
Usually the resin system can be applied in free foam
form. The prepared, mixed resin system, with the uniform
withdrawal of an injecting, extruding or casting head
is sprayed onto the correspondingly pretreated sewer wall,
from where the forming foam can rise freely or can completely
form. This procedure is e.g. advantageous if a pipe section
has to be sealed in a short time. However, this procedure
leads to an irregular, not-level surface, which is less
ideal from the flow standpoint, but in many cases is adequate.
Subsequently a spraying head for the internal resin system
mounted on a sliding carriage is drawn through the foamed
pipe, from which the epoxy resin system is sprayed onto
the PUR substrate. This procedure can also be very rapidly
performed, so that the machinery does not have to be used
for long. Curing then takes place through the introdudion
- 9 1 3366`6~
of warm air into the particular pipe section until complete
curing has taken place. Curing is generally completed
after 24 hours and the sewer section is then ready for
use again.
Optionally, a further, final covering layer can be applied
but is generally unnecessary in the case of free foaming.
The final layer is applied wherever special surface require-
ments make this necessary.
In the case of the present automatic machine foaming,
numerous equipment and component parts are commercially
available for the assembly of the apparatus used. Automatic
mixing and injecting machines (casting machines) with
a capacity of up to 100 kg/min are nowadays supplied by
numerous manufacturers. These machines generally comprise
a material container Rl,R2 for each component and a dosing
mechanism on which the necessary quantity ratio can be
set, a mixing head M where the two components are mixed
and a plurality of injection or extrusion nozzles S, through
which the resin mixture passes out in homogenous form.
The machines are generally provided with a temperature
control for both components. Such a machine can be converted
for the present process.
For the apparatus with a shaping pipe, which is not commer-
cially available and forms part of the apparatus according
to the invention, a commercially available mixing and
injecting or extruding head is modified and installed
in a shaping pipe of approximately 50 to 70 cm which,
in much the same way as a telescopic pipe, comprises three
to four telescopable rings. On the circumference of the
outermost, first ring 5 in the pulling direction -~ of
the apparatus are installed the material nozzles (injection
or casting mouthpieces). The following one or two rings
7,8 form the shaping and/or post curing zone. Such a
shaping pipe can also be drawn through a sewer pipe bend,
because it can be bent upto a given radius. Fig.2 shown
`- lo - 1 33666~
an embodiment of such a shaping pipe.
With the aid of a winch on a cable 10, the apparatus (which
advantageoulsy has its own drive) is drawn or moved into
the sewer pipe 1 to be repaired. By means of hoses 11
and not shown electrical connections, the apparatus is
connected to units enabling the operating energy and means
for the apparatus to be supplied. The apparatus has separate
ducts Rl and R2 through which the resin components can
be fed into the mixing chamber M. In the latter, where
a mixing device 13 driven by a mixer motor 12 stirs, the
resin components are mixed and the foamable resin mixture
is supplied to the mouthpieces S through nozzle pipes
6, which are radial in cross-section and then ejected.
A centring and sealing device 9 prevents any swelling
out of the resin in the pulling direction, so that the
resin spreading to form a foam passes counter to the pulling
direction into the gap between ring portions 7,8. In
the case of an intermittent advance speed corresponding
to the tack-free time of 10 to 15 seconds, a foam layer
of up to 2m can be cast or extruded in one minute.
The resulting intermediate layer, with or without a shaping
pipe, is relatively smooth and sufficiently mechanically
resistant that subsequently a sliding carriage for the
epoxy resin injecting apparatus can pass through the same
without damaging the intermediate layer surface.
The foaming with the insulating intermediate layer can
be controlled in a random manner. At points with extensive
damage, "casting" can continue until the damaged point
is filled. Only when this has taken place is the spraying
or casting apparatus drawn on again. This leads to a
very flexible repair system because, despite the intermediate
layer thickness, the expensive aftercoating with the mechan-
ically and chemically resistant epoxy resin system always
`- 11 - 1 3~66~3
occurs with the same thickness.
The presently proposed, rapidly reacting PUR foam, in
the case of long sewer sections, permits a coverying layer
application of the epoxy resin a relatively short time
after foaming. The epoxy resin is the actual pipe part
which will subsequently fulfill the function of the damaged
sewer and for its curing, said pipe part requires 24 hours.
However, as the intermediate layer only requires a fraction
of this time, it can be assumed that a treated sewer section
will be ready for use again after 24 hours as a result
of forced postcuring, e.g. by flooding with hot air.
According to the process firstly an insulating priming
layer is applied to a pipe to be lined and on said insulating
priming layer is applied the mechanically and chemically
stable layer to be sealed. For the sealing resin system,
the priming layer forms the thermally and chemically correct
substrate, on which the desired coating, despite dirt
and wet in the sewer pipe, can be applied in such a way
that correct hardening is possible and the service life
corresponds to the material used.
In a further development of the process, a special coating
process has been found, which only requires one coating
operation and has no need for shaping means and therefore
separating or parting means. This new coating process
is a centrifuging process permitting a direct application
to the e.g. concrete substrate in a sewer pipe and which
can generally be performed in one operation. The polyurethane
spraying foams are either poured manually or mechanically
sprayed and the applied material can then rise. The liquid
foaming gas contained in the mixture through the liquid
- gaseous phase junction expands the viscose resin material
and thus forms a closed-cell body with a limited specific
gravity. On suppressing the rising or foaming process,
there is a successive increase in the density of the coating
1 3366~3
- 12 -
and a resin layer with few cells and a much higher specific
gravity is obtained, which is completely tight and also
mechanically stable. This lead to the idea of developing
a one-coating method in place of the two-coating method
having a similar resin base and using similar equipment.
This has been made possible by the centrifuging process
described hereinafter. In place of the resin material
being cast, poured or sprayed, it is centrifuged onto
the substrate, i.e. is applied to the pipe inner wall
with a high kinetic energy. The resin layer formed in
this way is tight, tough and hard.
In order that the thick layer applied does not flow back
on the sewer bottom prior to curing and following the
force of gravity, it must either be thixotroped by adding
a thixotropic agent (obtainable for such resin systems),
or in the same passage is applied in a less thick form,
i.e. as a partial layer. Although the latter requires
several passages, it is easier to conquer from the process
standpoint.
According to this process, the final layer is only optional.
If such a layer is desired, then the centrifuged layer
in the same way as the foamed layer serves as a heat insul-
ating substrate and although the heat insulating effect
is less, it is still adequate. However, generally a sub-
sequent coating with e.g. an epoxy resin is not necessary.
In order to repair a leaky sewer section, the following
procedure is adopted. The pipe to be repaired and whose
leaking points have been detected beforehand, e.g. by
TV, is washed out by a known procedure, e.g. a water jet.
After basic drying the still wet pipe (which must not
have any puddles of water, which have to be sucked off
if nece~ry) is sprayed with the isocyanate component
of the polyurethane resin system used, in order to bind
the residual surface moisture. This pretreatment is also
1 336653
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to be carried out when there is only a moderate amount
of moisture and even if there is no moisture. This pre-
treatment ensures that the resin layer does not become
detached from the substrate and form bubbles. This pre-
treatment leads to satisfactory service life characteristics
of the repair layer in the sewer. In this example, prefer-
ence is given to use of a resin system of Polylite VP-626
RG30/8664 of Reichhold Chemie AG, CH-5212 Hausen bei Brugg
Switzerland, for hard polyurethane spray foam, particularly
for mechanical spraying, whereby the mixing ratios can
be obtained from the data sheet and instructions of the
manufacturer, as well as the mixing specifications;
or an equivalent resin system of type Resicast GH65 of
Shell Chemie, a particularly strong polyurethane resin
with good adhesiveness to concrete and with a residual
elasticity in order to bridge cracks, whereby the mixing
ratios can be obtained from the data sheet and instructions
of the manufacturer, as well as from the mixing instruction.
This spraying can be performed with the same apparatus
with which the resin system is centrifuged. After approx-
imately 1 hour the isocyanate has adequately reacted with
the water in order to serve as an adhesive substrate for
the subsequent resin coating. This measure prevents any
bubble formation or any detachment between the resin layer
and the moist substrate. The same machine can then be
used for applying the resin mixture by centrifuging to
the prepared surface. As a result of the short cream
time and tack-free time it is possible to insulate very
difficult surfaces in a very short time. The resin applic-
ation is set in such a way that the coating formed is
approximately 0.5 to 1 cm thick (in exceptional cases
up to 1.5 cm thick). At particularly difficult points,
e.g. where there are breaks in the pipe, the advance can
be s~owed down, so that the coating becomes thicker and
therefore stronger. The coating has good mechanical
_ - 14 - l 3 3 6 6 6 3
characteristics as a result of its substantial freedom
from pores.
Such a resin system gives a closed, watertight coating.
The cream time is 2 to 3 sec and the tack-free time 10
to 15 sec, the ideal mixing temperature being 20C. The
compression strength of the cured coating is over 2kJ/m2,
so that further working within the pipe structure is readily
possible. The short curing time, which can be assisted
by introducing warm air, makes it possible using a standard
centrifuging apparatus to obtain a pipe formation speed
of up to approximately 2m/min, which is very satisfactory.
The PUR resin readily adheres to the basically dried,
but still moist concrete surface, or to the substrate
pretreated with the isocyanate component. Optionally
a further, bearing, hard, smooth and impermeable epoxy
resin inner coating (final coating) can be applied, the
PUR substrate being chemically and physically suitable
for joining to the epoxy resin. These coating thicknesses
are relatively thin compared with the PUR layer, preferably
0.5 to 1.5 mm thick, whereas the outer layer is preferably
0.5 to 1.5 cm thick, i.e. the ratio is 1:10.
The question of whether or not a final coating is to be
applied depends on the desired flow needs within the sewer.
As stated, the final coating can improve the strength
of the overall coating system. It is also unnecessary
to provide such a second coating over the entire pipe
length. It need only be provided in the intended sections,
because as a rule the PUR layer centrifuged in one pass
is completely adequate.
If a final coating with an epoxy resin system is applied,
then it is recommended to use a separate applicator for
each resin system (epoxy and PUR), because these resin
systems react with one another. Mutual contamination
1 336663
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can lead to clogging of the nozzles and resin supply means
and such clogged material cannot be subsequently removed.
As in this novel process no means for shaping the coating
have to be provided, there is also no need for separating
agents, so that the speed of advance can be very high.
This is important, because a pipe section can be sealed
in a very short time (also in emergencies). However,
in the case of an unduly high speed of advance, an irregular
surface can be obtained, which is not flat and is less
ideal from the flow standpoint, although adequate in many
cases. Curing generally lasts about one hour and can
be assisted by introducing warm air into the appropriate
pipe section. Complete curing is generally obtained after
a few hours and the sewer section can then be used again.
In the case of the automatic resin centrifuging of the
present type, numerous pieces of equipment are commercially
available for the assembly of the apparatus to be used.
Automatic mixing, centrifuging and spraying machines (casting
machines) with a capacity of upto 50 kg/min are now supplied
by many manufacturers. These machines normally comprise
a material container for each component, a ~sing mechanism
on which the necessary quantity ratios can be set, a mixing
head where the two components are mixed and a centrifugal
head with a centrifugal nozzle directed onto the centrifugal
disk, through which the resin mixture passes out and is
distributed in a homogeneous form. The machines are generally
provided with a temperature control for both components.
Such a machine can be used for the present process.
The lining with the insulating intermediate layer can
be controlled in a random manner. At points with extensive
damage, "centrifuging" can take place until the damaged
point has been filled. Only when this has taken place
is the centrifuging apparatus moved on within the sewer.
The apparatus is passed through the sewer in such a way
that the rotation centre of the rotating centrifugal head
passes along the longitudinal axis of the pipe, so that
1 336663
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the centrifuged-on coating is uniform. This gives a very
flexible repair system, in which the parameters can be
easily adjusted.
The presently proposed, rapidly reacting PUR-resin system,
if necessary permits in the case of longer sewer sections,
a final coating application with an epoxy resin relatively
soon after the application of the previous coating. The
epoxy resin is then the final pipe part, which will sub-
sequently fulfil the function of the defective sewer and
this pipe part requires about 24 hours for its complete
hardening.
The presently proposed method eliminates all the known
disadvantages of the various known procedures for sealing
and repairing pipes, particularly sewer pipes. It makes
use of existing aids in an advantageous manner and is
inexpensive and unbelievably fast. The pipes or linings
produced with this method have long service life charac-
teristics, because they allow the resin systems to cure
in a substantially ideal manner and these characteristics
substantially coincide with those given for the corresponding
systems.
