[0001] The invention relates to a dredging vessel comprising a loading space for receiving
spoil, for example, sand and at least two effluent devices for conducting away the
head water standing above the settled sand, said effluent devices comprising a conduit
having a level-adjustable inlet and an outlet opening out in the outboard water, the
inlet of the conduit being adjustable between an inactive position and an active siphon
position, whilst the conduits of at least. two effluent devices are coupled on board
with a coupling conduit opening out in a common outlet conduit.
[0002] Such a dredging vessel is known from Dutch patent application 6816677.
[0003] When the loading space is loaded with comparatively clean sand, there is no objection
for the hardly polluted head water to flow directly away into the water stream moving
around the vessel. However, when the loading space is filled with sand containing
much sludge or another pollutant, the head water will be seriously polluted, which
may result in an unacceptable pollution of the environments when conducted . away
into the flowing water.
[0004] In order to avoid pollution of the environment across a wide region, the head.water
can be conducted away beyond the stream range around.the vessel which is located near
the bottom in a quiet stream so that the particles floating in the head water will
readily settle on the ground and will not spread over a large region.
[0005] From the Japanese patent specification 46-9297 of 1971 it is known to provide each
overflow of a dredging vessel with an effluent duct that can be lowered as far as
below the plane of the vessel. Such a lowerable effluent duct structure is comparatively
large and costly to guarantee a low effluent rate. Moreover, the flow through the
separate outlet ducts can be controlled'only with difficulty.
[0006] The-invention-has for its object to restrict environmental pollution with the aid
of a not excessively expensive, readily controllable effluent device. For this purpose
the outlet conduit comprises a tubular sheath, inside which is telescopically arranged
a level-adjustable, common outlet conduit which can be withdrawn into said tubular
sheath and be brought out thereof to a considerable distance below the vessel respectively,
and which is connected with the coupled conduits, said level-adjustable, common outlet
conduit having an outlet extending, during the loading operation, beneath the vessel
and being brought beyond the water stream moving beneath the vessel, and said common
outlet conduit being suspended to elevating means extending through the tubular sheath.
[0007] In order to ensure such an effluent of a large loading space that during loading
the location of the vessel can be checked, a further embodiment is characterized in
that at the front and rear ends the loading space is provided with two coupled, downwardly
pivotable nozzles which open out through a front coupling conduit and a rear coupling
conduit near the bottom of the vessel in a common outlet conduit.
[0008] It should be noted that it is known per se, for example, from Dutch patent application
6902178 laid up for public inspection to couple a plurality of effluent dishes not
forming part of the vessel to be loaded, but being associated with a dredging system'loading
the vessel with a coupling conduit not forming part of the vessel to be loaded and
opening out in the common outlet conduit, the outflow nozzle of which is level-variable
by being fixedly secured to a suction pipe of said dredging system to be inserted
into the ground.
[0009] The invention will be described more fully with reference to a preferred embodiment
of a dredging vessel in accordance with the invention as shown in the drawing.
[0010] In the drawing:
Figure 1 is a side elevation of the dredging vessel,
Figure 2 is an enlarged sectional view taken on the line II-II in Figure 1,
Figure 3 illustrates on an enlarged scale detail III of Figure 2, and
Figure 4 shows a variant of the detail III of Figure 2.
[0011] A dredging vessel 1 comprises a loading space 2 for receiving spoil, for example,
sand and at each of the four corners of the loading space 2 an effluent device 3 for
conducting away the head water 5 standing above the settled sand 4. Each effluent
device 3 comprises a conduit 12 consisting of a fixed tube 6 with an upward bend 11,
which is mechanically connected through a hinge 7 with and joined through a flexible
length of conduit 8 to a nozzle 9, the inlet 10 of which is level-adjustable, since
the nozzle 9 can he-lifted by means of a hydraulic ram 13 into an inactive position
9' . indicated by dot-and-dash lines and can be displaced into the deepest siphon
position 9" indicated by broken lines. A siphon position 9 is indicated by solid lines.
The two effluent devices 3 at the front end 14.comprise nozzles 9, which can be pivoted
downwards in common, since their 'hydraulic rams 13 have common control-means 16,
which actuate the rams 13 simultaneously and to the same extent. This also applies
to the two effluent devices 3
'at the rear end 15 of the loading space 2. The two tubes 6 at the front end 14 and
those at the rear end 15 are coupled with a front coupling conduit 18 and a rear coupling
conduit 19 respectively,- which are located on board and which open out near the bottom
20 of the dredging vessel 1 in an outlet conduit 21 common to all effluent devices
3, said conduit consisting of a fixed wide tube 23 arranged on board-and accommodating
telescopically a tube 24, which is level-adjustable by elevatig means 22 and which
has an outlet 25 located, during the loading operation, in the lowered state beneath
the dredging vessel 1 and even beyond the water stream 26 moving below the dredging
vessel -1, for example, at a depth of 8 to 10 ms beneath the bottom 20 of the dredging
vessel 1.
[0012] When the loading space 2 of the dredging vessel 1 is loaded, a suspension of mainly
sand and water is fed into the loadig space 2 from a suspension feeder 27, which may
be associated with another dredgig tool (not shown). The sand 4 settles down and the
water of the suspension will form the head water 5 above the.sand. The head water
5, which may contain, in particular, sludge and other impurities and even unsettled
sand is conducted out of the loading space 2 by means of the effluent devices 3 described
above. It is removed by siphon effect, since the upper bend 1.1 is located at a higher
level than the inlet 10. In order to actuate the siphon the air should be removed
at least for the major part from the siphon.
[0013] As shown in Figure 3 each upper bend 11 is connected with a water jet pump 34, the
water spray 28 of which is fed from a water pump 29. At an inlet 10 immersed in the
head water 5 vacuum is created'in the outlet conduit 12, which starts the siphon operation
so that the head water 5 flows through the conduit 12, a coupling conduit 18 or 19
and the common outlet conduit 21 and the outlet 25 into the outboard water 35 below
the stream 26 so that the impurities 33 can readily settle on the subaqueous ground
30 and will not be carried along by the stream 26.
[0014] Each inlet 10 preferably comprises a flap 31 (Figure 4), which narrows, by means
of a hydraulic ram, the passage of the inlet 10 in an adjustable manner to regulate
the head water flow rate through the inlet-10 concerned. This flap 31 may, in addition,
be utilised for starting the siphon effect. For this purpose, whilst the flap 31 is
closed, water is pumped by a pump 32 into the conduit 12, particularly, into the nozzle
9, the flexible length of conduit 8 and the upper bend 11. The siphon effect and hence
the outflow can be stopped by lifting the inlet 10 above the head water 5.
1. A dredging vessel comprising a loading space for receiving spoil, for example,
sand and at least two effluent devices for conducting away the head water standing
above the settled sand, said effluent devices comprising a conduit having a level-adjustable
inlet and an outlet opening out in the outboard water, the. inlet of the conduit being
adjustable between an inactive position and an active siphon position; whilst the
conduits of at least two effluent devices are coupled on board with a coupling conduit
opening out in a common outlet conduit, wherein the outlet conduit comprises a tubular
sheath, inside which is telescopically arranged a level-adjustable, common outlet
conduit which can be withdrawn into said tubular sheath and be brought out thereof
to a considerable distance below the vessel respectively, and which is connected with
the coupled conduits, said level-adjustable, common outlet conduit having an outlet
extending, during the loading operation, beneath the vessel and being brought beyond
the water stream moving beneath the vessel, and'said common outlet'conduit being suspended
to elevating means extending through the tubular sheath.
2. A dredging vessel as claimed in claim 1, wherein at the front and rear ends the
loading space is provided with two coupled, downwardly pivotable nozzles which open
out through a front coupling conduit and a rear coupling conduit near the bottom of
the vessel in a common outlet conduit.