NL1043211B1 - A multi-saw hydrodynamic dredger - Google Patents

Abstract

A multi-saw hydrodynamic dredger, Fig. 1 vertica I longitudinal and tra nsverse sections, with a bed leveler at the top, with slanted front and bristies at rear, towed over the bed of waterways, cuts, crumbies and brushes silt from the water bed and brings it into re- suspension in the water body, which is then carried away by the current. The crumbie capability is effected by increasing saw tooth settings. Silt cutting strength is enhanced by adding weight on the bed leveler. 1043211

Description

i & multbsaw hyiradynamic dradpey Technics! Held The invention is in the Held of hydrodynamic dredging, 8 multhsaw dredge with slanted from and bristles at rear, towed over walerways, cuts, crumbles and brushes silt from the waterbed ang brings i into resuspension in the water body, which is then carried away by the currant. Price art Lredging comprises an extended feld of sctivities, Each situation is addressed by an appropiate dredger, referred to by the name of the category In the Hersture, In the context of the hwention, sxplich reference To the Hermure B limited to hlradynamic vredsing, defined in II 9, 4 and degalled in [2] p02, including WID {water indeotion dredging}, plough and agitation dredging, auger dredging and jetting with str jet, is The common feature is thet sediment deposited on the water bad In the pours of Hime is brought Bio resuspension in the water body and then carried away by the river or tidal current, Ne hopper or Heating discharge ne, nor loss of Ume to sal to discharge location and back ere needed, H is especially sulted for the maintenance of waterways, is zost effective, emndronment friendly ond has a ower carbon Tavir! zompared to traditional dradger, 3 TSND trailer swoon hopper dredger) for that matter. Tharsis, there is growing interest in hydrodynamic dredging, Nonetheless, in WID the jet pump requires engine power, which can be several hundreds to mere then a thousand EW, a significant exirs load in kilo Watts and Blo grams added to the thrust capacity of the lugboat, see a fleet ist of WID In [3], p, 83. Jetting with 35 air, while alsa using engine power, tums aut to be ineffective, On the other hand, plough dredging does not need that extra engine power, but is Jess effective than WID, it Is used mainly as an aid To a main dredger, to do the places where the main dradger cannot come by and as bed leveler after the main dredge has finished the dredging. Therefore, a better alternative for this type of dradger is preferable.

In the next section, the application desoribes an hwenllon of a muiik-sew dredge suitable for hydrodynamic dredging and does not need engine power,

Description #1 this description the divection of tow Is called the longiuding! and that across the ww is called the transverse direction, The design of the vention ìs depinted In the drawings, Fig. 1, and the specification i giver in this description.

Fig. 1 a; Vertical jonghuding! section and 5: Vertical transverse section, front and rear view, with 1 bed leveler at the top, 2 8 mulliplichy of ential saws welded against 1, vertically from below, paraliel in the longfudinel direction, with slanted pointed front fr better cut i the mud while deflecting bulky waste, The saw teeth are only In the straight pants of the saws, Fis, 1 a, with straight cuts umward Hi half the saw height, slanted soross the saw Blade thickness for sharp edges In the saw direction, The tooth ends and pointed front of the saws facing the waterbed ars sharpened.

The sew tooth settings, La. the successive saw teeth shernataly bended fo the ai and to the right across the cutting divection, increases fron front 10 rear, Fig. 1h left part, thus progressively crumbing the mud, stead of having a regular cut through the mud as ancrmal saw with a constant tooth setting would 35 do. 3vows of oulindrical bristles at rear end, Big. 1 bright part, around vertical axes brush off sift frony the mud crumbs coming out freer the dress, 4 eves for the attachment of the tow calles & and § is the lwgbast With respect to dimensions and materials of choice, an exemplar is ghee 1 bad loveler, material marine grade Duplex stainless steel Ís. w, 8000 kgf), length Ln, Fin tow divection 2 my width 3.8 19, thickness 20 mm, 2 a dozen of identical saws of same materia as 1, thickness 1D mm, height 8.5 my, slanted AS degrees at the front, top length 1.5 m, so bottom length 3 wy, welded parallel in the longitudinal direction from below against the bed leveler, lemving al rear a space of 05 m of 1. The saw teeth are onb in the straight part of the saws and are cul for half the saw height tooth tps dloding the front part of the saws are sharpened to 3 nny thickness.

The saw tooth settings increasing from ont to rear progressively crumble the mud within the dredge, but leaving enough space for coarse dirt fo pass between Teeth and through the space above the saw teeth, see Fig. 1 b left part, The side plates of thickness B wim, without teeth, with rounded edges ave Tor safety. 3 oylindrical bristles at rear to brush off 39 the silt from the mud orombs. 4 eyes for attachment of tow cables. § tow cables, material

UHMWPE Ll, prefarably Oynsema SKIS Ís, w, 370 kgm’, vield strength 240 kg/m i Hoats on waist is 35 strong as high-strength steel cable, but 8 times lighter. § tughast Wis noted, that in contrast to the plough dredger, the bad leveler Lis not at the bottom of the dredge, but zt the top. This is an Important feature of the multhsaw dredge, allowing for high efficiency. The muRi-saw dradge weighs 1500 kg in water, The syrface of the bed leveler is § m3, zo the ground pressure at the water bad Is 300 kgf’, small compared to the hydrostatic pressure at the waterbed {1000 kg/m per meter deh of an ordinary river. However, the ground surface of the sharpened multh-saw Is DAF2 5 its ground pressure is 1500/0073 w 20800 kg/m, good enough to cut in sit So, In the rudtbsaw dredge the bed leveler serves not andy as bed pveler, but mors importantly & serves also as ground pressure reducer by the large surface of the hed levpler, while the sulting power Is determined by the much higher ground pressure of the multhsaw, a distinctive Teature of the muith-saw dredge comparad to the plough dredge.

Moreover, the cutting power can be enhanced by adding more weight on the hed leveler, This gives the mudth-saw drage the capability of a cutter dradger, thus crating a new category: the hydrodynamic putter dredger, For geen more cutting efficiency the adilitional weight can be spring loaded to gat ihe effect of a demolition hammer, with an onfoff provision, on spring vibrations allowed ang off: spring vibrations hacked, The dredge depth that can be reached depends only of the length of the tow calde, 8s js obvious, the depth can be caloulated fram the length of the cable and iy Inclination angle.

Fivadly, detail Jor mega! righoity and stability of the construction does not belong to the vention and is not desorbed, but is Implicit, 5 Short description of Fig. 1 Fig 1a Vertical longtudinal section, D: Vertical transverse section, left: front view and right rear view, with 1 bed leveler at the top, 2 a multiplicity of saws with slanted fronts, welded in paratiel under the bed leveler in the ongituding! direction, with increasing tooth 20 sotiings from front to voor, 3 rows of oylindries) bristles at rosy ond, 3 eves for the attachment of tow cables, S high-strength UHMWPE tow cables and & tughost

Application To tow a single unit a boat long 8 - ID m, width 3 wm B appropriate. As tow cable Dyneema SK75 of 13 mmm diameter, which has a pull strength of 13000 kg, one cable at gach side of the dredges, can be weg, The dredge capecty can be estimated as follows. S Dredge width 2.5 m, saw tooth length 0.25 mm, tow speed 2000 mm/h, Assume an intrusion depth through the silt layer of 0.35 my, the capacity is 3.5 x 0,25 x 4000 = 2500 mh, The capacity can be regulated by increasing or decreasing the tow speed/engine power of the boat, itis also possible to scale up the dredge In a modular way, by parallel coupling of 2 to 4 units, As a typical application the situation at the dynamic mud coast of the three Guyvanas at the north coast of South America is considered, The Amazone River carries sediment from the Amazone region to iis river delta m the Adantic Ocean. The Guyana stream parries the mud slong the nonh coast of the three Guyanas and further westward, Within 10-30 km of the coast the ses depth is less than 10 m, Moreover, as the mud banks move with the stream, the situation ts changing with Ume, So a ses port on the coast is hot feasible. Furthermore, rivers with their mouths at the Atlante Ocean is silted from Ds proper sift and from the moving mud from the Amazone. For example, according to the MAS {Maritime Authority Suriname} the Suriname River gathers 0.5 m slit in two years, By mid of 2018 at low tide the depth Is 4m, causing problem Tor ships to sail iy, to reach the pant of Paramaribo, capital of Suriname, some 30 km up river, The situation is critical and dredging is urgently needed, as iustratad by twe incidents mentioned in the news media. End of June 2018 the ship Marine Prince stranded at the mouth of the Suriname River and on August 10 2018 a freight ship stranded near the port of Paramaribo ending with a hole jn the hull near the rudder.

35 As is obvious from the above story about the cause of the silt up, maintenance dredging is appropriate in this case, with a TSHD traditona! maintenance dredger, a WID hydrodynamic dredge with engine power for the jet pump ov the mubtb-saw dradge.

While comparing three different categories of dredgers is not a simple matter, maintenance dredging is en ongoing activity and decision needs to be made on some vital cluss, like cost and efficiency for long term recurrent projects.

With regard to costs, taking into consideration the purchase prices alone, a TSHD costs 1010 30 million Eros depending on the hopper capsclty, newts a craw of §- B to operat, a WID mounted on a mult cat costs 1 ~ 2 million Burns, needs a crew of 3-4, wile the muitbsaw dradge, including tow cables snd motorboat cen be of the order of 100 ~ 200 5 thousand Euros, a tiny Traction of TSMD or WID and can operate with a mew of ZL To compare the efficiency for the envisage tase, the duty oydde, Le, the duration of dredeing during the work period, for 20 km of river from mouth to port and discharge 10 km at sea a TSHD filly the hopper Tull with dredge in about 1 hour, sails to discharge location and hack, on the average 50 boy 3 hours, discharge time i short, the duty opcde is 25%, So, a TSHD is dredging ondy 25% of the total working hours, A WID can do more, yet the jet pump engine cannot run continuousiy either, On the other hang, the multisaw dredge car remain in the water, while crews shift 3x por day, The muitheaw dredges cen ba used Jdhfday.

Conclusion, The above Nustrates that the overhead as well as the running costs of the mult-saw drgdge are the lowest compared to the altermatives.

Referens {1} A.

Birchenough and L.

Howe, Project MES403- Module 19-Hydradynamic Dredging and Plough Dredging, Oktober 2011, wwwastlencesaarchudeda govauk FIR Sigwald, S Ledo and K, Spencer, GEODE, Water injection dredging, February 2015, www. ceramaldr {31 R.

Swart, Autonomous dredging of mud, MSc thesis TU Realty, December 2015, www repository tude, n 4] https fen wikipedia orgfwikifUlrahigh-molecular weight polyethylene NOTE related to the wijten opinion Besides this nate no change made in the text of the application.

Prior arts DID in the written opinion are of the cstegoies plough, agitation and auger deasiging, already shscussed on page 4, ines 13-39, Claim 1 is redressed In response fo the written opinion, eluidating the construction of the multh-saw dredger to achieve a better efficiency than afore mentioned, though useful cormnan auxiliaries Nke bristles are aise used in this nase.

Claims (3)

Lonchsies 1. A hydrodynamic dredge with a bottom leveling load, characterized by a multitude of identical saws. 5 vertices at equal distances in the drag direction of the dredge! fixed against the underside of the bottom leveling ring. The saw blades are constructed according to the successive operations: 122. The saw blades are cut diagonally downwards at an angle of 45 degrees on the front edges, so that the front edges become pointed, 3%. The underside of the saw blade is sharpened, causing the saws to exert high pressure on the sludge, 3%. The teeth of the saw blade are vana? the underside straight up, but cut alternately diagonally across the thickness of the bisd to half the height of the saw blade and only in the straight side of the saw blade. As a result of this operation, the seed teeth in horizontal cross-section get the worn of sen Trapesium, with the sharp edges in and against the direction of drag. This operation also prevents the sawter from hindering their teeth while eating. 49 ° The tooth retention of the saws move from front to back, so that the crumbling of the sludge also tends from front to back. 2. Eon dagger according to claim 1, provided with brushes at the back for brushing the sludge from the mud crumbs flowing out of the dredge, 36 A dredge according to claim 1, wherein on the one hand the pressure of the seine on the water bottom is increased by weight on the bottom leveling puddle in order to dredge through harder slip layers. BijR to keep the sigepwesrsiand low, 4. A dredge according to claim 3, characterized in that the imposed weight is applied resiliently, so that the dredge also functions as a demolition hammer, with a provision to set this function san and ull.