10-04-2017, 08:27 PM
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STRUCTURAL DESIGN OF DRYDOCK FRONTAGE DREDGING SYSTEM
EXECUTIVE SUMMARY
In the present era of globalization, transportation has an important role, being the cheapest mode of transport, ships and boats contribute much to business and industry. Their repair maintenance and manufacturing are carried out in docks. The moment of floating crafts towards and outward the dock faces the problem of mud deposits on the path. In order to maintain an accident free dock, these mud deposits are to be removed off periodically. This process of removal of mud in the ship channels and front portion of the dock is known as dredging.
In our project we have designed a dry dock frontage dredging system.
PROJECT REPORT Submitted by
ELDHO PAUL JOBIN JOSE SREEKUMAR S. VINEESH T.V.
1. INTRODUCTION
Dredging is one of the important fields on which major ship yards and ports are concentrating and spending a lot of money per year. The deposit of mud on ship channels and front portion of dock, where all the repair works of vessels are carried out is a problem faced by the port. This will reduce the draft and prevent the vessels from entering the port for berthing and to the dock for repair works. We concentrate our project on designing the dock frontage dredging system and by that maintaining a neat and accident free dock.
A cutter suction pump is used to do the dredging operation. A readymade cutter suction pump is available at the Port Trust. So in our project we have designed a framework to hold and manipulate the pump. Also a floating platform is designed, on which the frame work is mounted. This float can be moved very close to the gate so that the regions closer to the gate can be dredged most effectively.
2. RELEVANCE OF OUR PROJECT
Dock frontage dredging is very important for the accident free functioning of the dock. The gate of the dry dock remains closed until the repair work or maintenance of the floating vessels is over. By this time the mud deposits may have reached to a height of nearly 1.5mts in front of the dock gate.
Conventionally the dredging operations at Cochin port trust are done by using a dredger ship and an L & T Poclain and hopper unit. Both these systems could not dredge the dry dock region effectively.
In our project we have concentrated in designing a dredger unit, which can dredge the dock frontage region most effectively. Also it was found that the mud deposit does not contain rock particles and the cutter suction pump is most effective for this.
3. COMPANY'S PROFILE
When the Cochin Port trust was brought under the major port trust act, the activities, of the mechanical engineering department were allocated to the chief engineer. The separate department was formed only in 1970.
The Mechanical engineering department, headed by the chief mechanical engineer has a vital role to play in the following areas.
Container terminal
Workshops and Dry dock
Electrical divisions
Internal combustion engines division
The operational and maintenance activities of the equipment at the Rajiv Gandhi container terminal of the port is looked after by the container terminal division of this department.
The port workshop and the dry dock is situated at the southern side of the Willington island, where the vessels come for underwater repairs and maintenance of their hull and machinery.
Electrical divisions are mainly involved in the distribution of electricity and repair of electrical equipments and their installation of the port.
The I C engines division of this department carries out major overhauling and operates a fleet of light equipments like forklift, light duty mobile cranes etc. for cargo handling operations. The major repairs and overhauling of the land equipments of Port Trust are also carried out there.
The mechanical engineering department is also involved in the in the procurement of the entire minor/major equipments for the cargo/container terminal operation and for the procurement of floating cranes, vehicles etc.
4. COCHIN PORT TRUST : PORT FACILITIES
Cochin port is an all weather port. A draft of 38ft is maintained in the Emakulam channel along with berthing facilities, which enable the port to bring in large vessels, in the Mattanchery channel, the port provides round the clock pilot age to ships subject to certain restrictions on the size and draft of vessels. There is an efficient network of railways and waterways and airways connecting the port with other centers spread over the state Kerala, Tamil Nadu and Karnataka . Facilities for supply of water and bunkering to vessels are also available.
SPECIFICATIONS
APPROACH CHANNEL
Outer channel length 1 OOmts
Draft 11.7mts
Width 200mts
47200mts 9.14mts 244mts
BERTHING FACILITIES
Number of wharfs 2
Length
Mattanchery wharf 670mts
Ernakulam wharf 918mts
Coal berths 2
Length
North coal berth 170mts
South coal berth 170mts
Draft
Tanker berth
9.14mts 3nos.
North tanker berth accommodates ships up to 198mts in length and of size 27,000 DWT and 9.14 mts draft
Cochin oil terminal accommodates ships up to 1,59,000DWT AND 11.7 mts DRAFT. 4.1. Dry dock
Dry stock is the place for maintenance and repairing of underwater section of marine vessels. Since the underwater sections cannot be assessed in floating conditions, it needs a special system and for this a dry dock is provided.
The main functions are.
1. Repairs of floating cranes and other marine floats brought near the dock .
2. Fabrications, welding and fitting works of vessels.
3. Effective implementation of quality system in dry dock.
Specifications of dry dock
Length 66mts
Breadth 12.5mts
Draft 4mts
Cranes provides in the dock side for hoisting and erection operations.
1. Steam operated crane SWL:8T
2. Diesel carne SWL:6T
Filling and evacuation time
Filling time
De watering time
4. hours
4.5 hours
Pump specifications
Centrifugal pump no. 1 Centrifugal pump
3 0Hp,960rpm(Self primed) 90HP, 985rpm
4.2 Docking and Undocking Of Floating Cranes
1. The MS receives work order , together with the docking plan of the vessel with copy to the AMS for under water repairs of the vessel.
2. After the work order is registered the AE instructs the AF to pump out water from the dock using the pump fitted adjacent to the dock to clear the dock.
3. Ensure the dock gate is closed before water is pumped out.
4. Once dewatering is completed, the blocks are arranged under the supervision of AE by the workers as per the docking plan of the vessel.
5. Flood the dock again
6. Open the dock gate.
7. Bring the vessel into the dock through the gate by towing manually.
8. Close the dock gates
9. Position the vessels to mark inside the dock
10. Pump the water from the dock.
11. Check the markings, position the vessel and give instructions to the AF and other workers to ensure that the vessel is seated properly on the blocks and the same is reordering the docking register.
12. Clean the underwater areas of the vessel.
13. Clean the dock floor.
J 4. Repair works are carried out as per the work order received.
15. After completion of repairs, AE inspects the vessel and if fit for flooding the AF instructs to flood the dock. The dock is flooded and the vessel is kept on a float. AMS and the engineer in charge/master of the vessel carry out a joint inspection.
16. Open the dock door and vessel is taken out of the dock by towing manually or by using tug.
5. DREDGING
It is process of removing the sludge from the channels of vessels and from the front point of the dock. The mud is deposited due to various natural phenomena such as flow of rivers, sea tidal effect and many other reasons. The mud, which is carried out by river water from remote areas, is deposited in the channels of the ship. This makes difficulty for the ships and vessels for their travel. So periodical dredging should be carried out.
The Cochin PORT Trust has repair dock. The front portion of the dock consists of a gate, which faces towards the backwaters. Once the dock gate is closed for repair works the gates should be reopened only after completion of under water repairs, during this period the gate is kept closed. Due to natural phenomenon the sludge is deposited in front of the dock and this makes difficulty in opening the gate as the gate is opened towards the backwaters. The deposited sludge may have a height of nearly 1.5 meters. Although conventional methods can be used, the dredging is not perfect. Before each and every docking and undocking operation, the channels and front side of the dock is dredged.
5.1 Study of dredging
Conventionally various methods are used for dredging . The main methods, which are used at Cochin Port Trust, are 1. using G.H.D,a dredger ship . 2. By L &T poclain and hopper unit. 3. By using shovel and floating cranes.
The first method is the major and effective method. This is done by a dredger ship named "Nehru Sathabdi" Having four 'grabs', operated by four electrical cranes . The cranes collected sludge in its grabs and deposit it inside the V shaped hoppers, which is situated inside the ship as a separate unit. The simultaneous operation of four cranes will fill the four hoppers. This operation would tale nearly two and half-hours of time to fill the hopper. The time consumption depends on density and
availability of sludge. After stopping the operation, the ship sails towards the. dumping area in the outer sea. There it will discharge the contents inside the hopper by opening the hoper by electrically operated winches. The time for traveling and discharging should take nearly one and half hours and this will be the most effective and useful method because the rate of sludge removal is high. The dredger removes sludge upto nearly 10 meters from the gate of the dock.
Advantage of the System
1. The sludge removal rate is high
2. Transportation is done by the system itself.
3. Fast method.
Limitations of the System:-
1. It cannot reach the front portions of the dock.
2. The dredger needs self-dredging for its own path
3. Transportations time is considered as idle time
5.2 Specifications of Dredger ship
Name
Technical name No. of Cranes No. of Grabs
Nehru Sathabdi Grab Hopper Dredger Four Four
The second method is by means of a poclain and hopper unit. This is a combination of two units. The first unit consists of a poclain placed on a floater. The poclain that is used for earth moving, instead of its grab used in the dredger ship, is fitted. This collects the mud and deposit it in the hopper unit, which consists of two V shaped hoppers which can be opened at its bottom by manually operated winches. After continuous dredging, the hopper gets filled and this is carried out to path of main dredger by guide boats and sludge is discharged. Both the two units have no self-propulsion facilities. This is also used to dredge the front portion of the dock. The shape of the gate and the grab does not permit effective dredging.
Specifications of The Poclain
Type of machine Operating weight
Crawler type hydraulic excavator
20-150tons
Max Digging depth Max dumping height
5.85m
6.58m
Engine
Make
Model
Type
No. of Cylinders Gross power
Ashok Leyland LTD ALU4112
Inline, direct injection 4 stroke,
water cooled, diesel
Six
136HP@2150rpm.
Advantages:
1. It can dredge much closer to dock.
2. It can be used for dredging remote areas.
3. Operation is simple
Limitations:
1. The unit is not self- propelled
2. It can dredge a depth of only 5.85mts
3. Travelling and discharging is time consuming.
These dredging methods are effective, but not much effective for one
specific tasks that is for dry dock frontage dredging.
This led to the requirement of new dredging system, Our project is aimed at
designing a new dredger system for the effective dredging of the dock frontage.
6. NEW DREDGER SYSTEM
The components of the new systems are
A cutter suction pump (dredger pump)
A power winch for the lifting and lowering the pump
A frame work tor the suspension of pump and the winch
Bearings about which the frame work can rotate
A floater
Chain mechanism for rotation of the frame work
Power Control panel
Fenders
Each of the components are explained in detail
Figure 6.2: Side view of the new dredging system
All dimensions are in mts
6.1 CUTTER SUCTION PUMP
The mud or slurry deposits at the dock frontage and near by regions are found to have small and only negligible rock particles. It mainly consist of sand grains and mud. Thus a cutter suction pump is suitable for the dredging operations.
The main components of the dredger pump are the cutter, pump and the
motor.
In cutter suction pump, the cutter head first cuts the deposited mud, diluted it with water, the booster pump or the dredger pump sucks these diluted mixtures by means of impeller and makes it into a slurry and delivers. All these operations are combined and performed by specially designed pump.
The maker of the pump - TOYOTO DENKI INDUSTRIAL CO.LTD, after their years of experiments and trials, have developed this pump to effectively convert solid mud to a slurry and pump it off. The delivery hose connected to the delivery pipe of the motor, deposits this pumped mud to any other regions.
Specification of the pump
Part List of Type DP Standard Type
No PARTS NAME QTY MATERIAL
t CA3TYRE CABLE
2 CABLE PROTECTION TUBE 1 RUBBER
3 PACKING GLAND 1 EC 250
4 SET RING 1 SS400
5 PACKING RUBBER
5 i SET BOLT 16 SS-iOO
7 IEAD COVER 1 FC250
a PACKING 1 RUBBER
10 HA.vOLE 1 3GP
; T UPPER COVER 1 EC 2 50
11 THERMAL PROTECTOR 1
u fi. HEARING 1
"tS PACKING RU80ER
17 SHAFT 1 SCM135
IB ROTOR t
19 STATOH 1
20 MOTOR CASE 1 SS400
22 SEARING LOCK PLATE 1 S25C
23 R. BEARING , 1
24 T. BEARING
25 BEARING COVER 1 SS40Q
25 27 SET SOLT SS400
MECHANICAL SEAL 1 SET
28 HOUSING t FC250 .
29 PACKINfl 1 RUBBER
30 SHAFT SLEEVE 1 SP. STEEL
No. PAHTS NAME QTY MATERIALS
31 OIL SEAL \
32 OIL CHAMBER COVER 1 . FCD503
13 PACKING 1 RU9DER
3-1 SET DOLT SSJOC
35 UNDER COVER 1 FC250
3S KEY 1 S45C
3/ IMPELLER 1 HCR
30 CASING 1 F CO 500
33 IMPELLER COLLAR 1 S25C
40 IMPELLER NUT 1 ss-ioo
41 SUCTION COVER HI;R
42 PACKING _ RUB3ER
43 SET BOLT SUS304
H ADJUST BOLT . 3 Sl>S3C-4
45 CUTTER f AN 1 HCR
<S6 STRAINER 1 SS400
47 SET BOLT SS400
49 OIL INLET PLUG
51 PACKING 1 RUBBER
52 BENO 1 FCOSOO
53 PLATE PACKING 1 RU3BER
54 SET BOLT 4 SS-WT
55. HOSE NIPPLE 1 FC-.'M
56 PLATE PACKING 1 RUDDER
57 SET BOLT 0 SS .0O
Dimensions of Type DP
TYPE A 81 B2 C D E F F2 H
DP-3 785 636 370 580 350 320 320 103 353
OP-5 K0S
700
DP-7.5-1 850 665 415
400 300 340
'373
DP-7.SB-1
727 425
305 K3 413
DP-tO-1
DP-10H-1 (60 Hz) 890
740
OP - 10H - 1 {50 Hz)
786 490
440
44 3
Table 6.2: Part list and Dimensions of type DP
6.1.1 OPERATION OF TOYO DREDCER PUMP
The Toyo Dredging System is very simple in its operation. The pre operation checks are simple and few;
1. The power supply voltage and frequency should be checked
2. The direction of rotation of the cutter is also to be ascertained.
3. The pipeline is also to be checked for any misalignment.
4. The delivery end should be at a height of at least 2-3mts from the ground level.
The Toyo Pump should be lowered under water level and then started. Then Toyo Pump has very high initial torque and hence it is found that the starter, which is normally fitted, has best results both in terms of current reduction as well as torque requirements. One the required rpm is reached, the power is automatically transferred to the autotransformer. This usually takes only a fraction of second.
This can be easily established from the ammeter as well as by physically watching the pump. The pump is totally vibration free and noiseless.
Once the rated rpm is reached, the pump is lowered to the bottom gradually and the dredging starts. The cutters of the pump rotate and cut the mud and then mix it with water and produce the slurry, the mixture of mud and water. The system is designed to pump an optimum concentration of slurry( 15-20% by volume), which can be maintained by operating the rated amperage. The Toyo Pump model DP 1008 has been found to be the optimum model for dredging in harbor and minor ports. It can be dredge about 60-72 m3 of solids/hours at an average static head of 3-6mts and a delivery distance of about 300mts. The distance may be increased by use of booster pumps. The standard range of Toyo Pumps can operate up to a depth of 30mts under water without any modification. Special range pumps are available for dredging at greater depth up to 100-120 meters. The operation of the pump is heavily influenced by the depth of operation.
7. DESIGN ANALYSIS
The floater is the floating member. It is rectangular in shape. All the other components rest on this floater. It mainly consists of a frame to support the pump and hoist. As the pump and hoist have a combined weight of approximately 500 kg ie 4905 N, the frame should have sufficient strength to with stand the forces that will be produced .
Another important factor, which should be taken into account about the floater, is that the floater should be in proper balance. As the pump is supported on an overlapping frame the weight of the pump causes an unbalanced condition. More over we have to dredge around the floater, the frame has to be rotated. This also has to be taken into account while considering the stability of the floater..
Another factor is that the frame has to rotate carrying the weight, so a rotating member should be added for smooth rotation.
Size of the floater should be less than the size of the dock; so that easy turning and rotation of floater inside the dock is possible.
7.1 THE FRAME WORK
The frame work for the suspension of pump and the winch consists of a horizontal beam, a column and a support member.
Figure 6.4: Free body diagram of the frame work
The detailed design of the frame components is as follows.
Design Procedure .
The cutter suction pump is hung from the end of the beam. For the safe reaching of this pump around the float, the length of the beam is taken as 4.2 m. An extra support is given at the centre of the beam to reduce the bending of the beam and also to reduce the bending stress acting at the cantilever support.
Length of the beam (L) = 4200mm
Distance from the cantilever
Support at which extra support is given = 2100 mm
Weight of the cutter suction pump = 300 kg
Total weight including power winch,
chain or chain for lifting the pump &
suction force (W) = 1200 kg
11722N.
This weight W is acting at the beam end. As trail and error method applying taking outer diameter of beam as 127 mm, inner diameter as 110 mm from standard Is tables.
Outer diameter, D
127 mm
Inner diameter, d
110 mm
self weight w
16.2 kgf/m = 0.15889 N/mm
7.1.1 BEAM DESIGN
To find the reaction at the extra support, following procedure is adopted. Consider only the weight watching at the end of the beam.
r
Figure 6.6: Free body diagram of beam The equation for deflection at any distance 'X' is given by
EIyD = W
v 2 6
= 11.772xl03
= 90.85xl03
90.85xl03
2.12 2.13A
(1)
W= 1200x9.81 = 11.772
Now consider the self weight of the beam only. This can be considered as a uniformly acting load.
EIyD= {l-x)A +
D 24V ' 6 24
= 250(2 l)4 I 250x4-23x2-1 25Q(1 2)4
" 24 V ' ^ 6 24
= 3444
3444x103
yD=+ - (2)
EI
Next considering a force R acting as shown below.
1
/
r
/
R
Figure 6.8: Free body diagram of beam
For this deflection equation is,
EiyD=^[3/-x]
= R& - [3x4.2-2.1]
6 1 J
(3)
yD =
R(7.717)
EI
(l)+(2)+(3)=0
90.85xl03 + 3.444xl03 - R (7.717)=0 R= 12.22x103 N
= 12KN
The bending moment acting at the beam support is given as
BMn = "Wx--W(;x-x-
D 2 s 2 4
= -11.772xl03x2.1 -250x2.1x1.05
M
l =-25.272kNM (Anticlockwise)
Section modules at the beam
z=7i(D4-d4)= 7t(1274-U04)
32D 32x127
= 87920.25 mm4
M
Bending equation for the beam ab =
ab= 25272xl0^= 2874N/mm2 87920.25
Where ab is the safe stress. For c- 35 martial, ob should be less than 440 N/mm3
Here ob = 138 N/mm2 < 440 N/mm2.
Design is safe with c- 35 steel of outer diameter 127 mm and inner diameter
110mm.
From Figure
Rl=R cosG
= 12 x 103xcos60 = 6xl03
Pj = R1cos60
= 6x 103xcos 60 = 3000 N Rh = R1 cos 30
= 6x 103xcos30
= 5196N
Moment due to Rh at B, M = R ^ xl
= 5.2x1 = 5.2KNM
= 5.2xl06NMM
Net moment = 25.27x 106- 5.2x106
= 20x 106Nmm
P2 =20x 106
P!=^I9:=.4761.9N
4200
Slenderness ratio of the column:
considering the column to be fixed at the bottom and free at the other end. Effective length, Le = 2 L = 2x1000 = 2000mm
Slenderness ratio =
K
as by trail and error method,
Outer diameter D = 152.4mm
Inner diameter, d =135 mm
Self weight, w = 19.6kgf/m
D2+d2
Radius of gyration, K = = 51 mm
there fore slenderness ration, = ^999_= 39 22
K 51
Area =n(o2-d2)
4
n/A (l52.42 -1352) = 3927.6mm2
Then for eccentrically loaded column according to Eulers formula, max. compressive stress,
A
P P2.e
1 sec
A Z
(P A Lx.P-
VEI
L = column length = 1000 mm Z = section modulus K
D4-d4
32D
K (l52.44 -1354)'
32x152.4 v ;
133531.4mm
3
I = Moment of Inertia of section = (D4 = d4)
64 v ;
71
64
(l52.44 -1354)
= 10.18xl06mm4
E- young's modulus = 2x 10 N/mm
EI = 2.035xl012
ac = + A
3000 3927.6
Lxi
EI 4200
P P e
+ sec A Z
4762
4762
3927.6 133531.4
Sec
100
4762 EI
oc = 0.764 + 1.212 + 149.8xl = 151.7 N/mm2
Corresponding to this oc steel 88 or C-55 Mn 75 steel can be selected with diameter Dout = 152.4 mm and Din = 135 mm.
7.1.3 Design of Support Member
Rn 5196N
Length = V 12+1.72
Radius of gyration, K
Taking outer diameter, D Inner diameter, d
Therefore K
Area
2147 mm D2 + d2 4
127 mm 110 mm 1272 + 1102
7T (D - d2)
42 mm
7t(127 - 1102)
Slenderness ratio, Le/K
3164.37 mm2 51.1
Assume C - 35 steel is taken as member material with yield strength,
ay = 280 N/rara2.
Using Johnson's parabolic formula for a columns
buckling load, pc = A ay
r
2 \
Pc
3164.37x280
r
280
2147
2^
4TX2X4X2X 105
42
where A
865.5 KN 3164.37 mm2
2147 mm 40 mm
4 for two ends fixed column 2 x 105 N/mm2
ay = 280N/mm2
From the designed L =
Pc = 865.5 KN is the K
Safe load that can be n
transmitted through the member E Without failure
But the load coming on the member in our design in Rn which is only 5.19 KN. The design with above parameters are safe.
7.2 BEARINGS
The frame work is connected to the float through a bearings. The base of the frame work is inserted into the journal bearing. The bearing is welded onto a carbon steel casting plate and this is mounted into the float structure by four bolts and nuts.
Sliding contact journal bearing is used to support the beam. The bearing material selected is cast iron. The reason for selection of a journal bearing is due to it's minimum maintenance required, less initial cost etc.
To support the axial load, thrust bearing is used at the bottom.
Lubricant used in the bearings is grease. The reason for selecting grease is due to the conditions prevailing at the port. There is no high temperature rise in the bearing. Grease can harmlessly embed the material and does not require much care as in the lubricant oils. Therefore grease is the ideal lubricant, which can be used here.
Design of bearing for bending
Trial diameters Inner diameter, di = 152.4mm Outer diameter, do = 182 mm Bearing material is carbon steel casting Grade 27 - 54
Yield strength of the material ay = 270 N/mm
Factor of safety, F.O.S/ = 2
Working stress [ab] should be less than, ab/F.O.S.
i.e., [ab] < 270/2
< 135 N/mm2
Section modulus, Z = TT/32 (d04-di4)
do
TI/32 (1824- 152.44) 182
3 00.869 x 103 mm3
Bending moment, M = 25.272 x 106 N mm
[ab] =M 25.272 xlO6 = 83.997 N/mm2
300.869 x 103
83.997 N/mm2 < 135 N/mm2
Thus the bearing with selected dimensions is safe. Bearing with outer diameter 182 mm and inner diameter 152.4 mm is selected.
DESIGN OF BOLTS FOR MOUNTING THE BEARING ON THE FLOAT.
C 45 steel bolts are used
No. of bolts n
Yield strength of bolt in tension
Factor of safety, F
Maximum shear stress, Tmax
Tmax
Net moment acting at the
bearing base, M Also M F
380 N/mm'
0.5 x ay = 0.5 x 380
Y 2.5
76 N/mm2
25.272 x 106 N/mm PxL
25.272 =' 39/75 x 106
L
L 250
Length of bearing 250 mm 159 x 103 N
L=250
All dimension in mm
Figure : 6.10 Bearing with Dimensions
Shear force on the bolt, P1
159x10J
Direct shear stress on the bolt, T
'A' = the cross sections area of one bolt Tensile force, P"
i i and I2 are shown in the figure b = 682 mm I2= 100 mm
P"
Tensile stress in the bolt, at
n 4
39750N
nl
39750
(P x L) I, 2(I,2 + I,2)
(25.272 x 106 x 682
A
18137.90
According to maximum shear stress theory
Tmax =
yh+T2
76
18137.90 +
^39750^
2A
762
1662.06 x 106
A = 536.46 mm2
Corresponding to this cross sectional area, from the standard series of bolts, M #0 coarse series bolts can be selected.
7.4 DESIGN OF FLOAT
The float is designed as rectangular box type as shown in figure.
7.4.1 Float Design (Structural)
Total Weight Equal Leg Angles
(4x4)m2x2 + (l x4)m2x 4+ (1.3 x 1.3)m2x 1 49.7 m2 48 x 49.7 2385.2 Kg.
Equal leg angle are used at the edges of the float. <90, 90 x 10 angle is selected
Length of Legs A x B Thickness, 1 Mass, m
Total length used Total weight Parallel Flange Channel
90 x 90 nun2 10 mm 13.4 kg/m
8 x 4m x 4 x lm + 8 x lm 589.6 Kg
t, \
t
8 J
MCP 75 channel is selected D B
Mass
Length of channel used
Total weight
Steel tube used
Outer diameter, D
Inner diameter, d
Weight w
Length
Total weight Total weight of the float
75 mm 400 mm 7.14 Kg/m
8x4mx4xl.9m+lxl .3m 40.9 m 7.14x40.9 292.03 Kg
33.7mm 25mm 2.93 kgf/m lm
2.93 x 1-2.93 Kg
2385.2 + 590 + 292.03 + 2.93
3270.16 Kg
Fencing used = 100 Kg
Extra weight = 100 Kg
Total weight of frame and load 2m x 19.6 Kg/m + 4.2m x
16.2 Kg/m + 1200 Kg. 1307.24 Kg
Weight of 3 person 3 x 70 = 210 Kg
Net weight = 4987 Kg
48926 N
7.4.2 Float Design
Total weight of the float i.e. W
48926
Thus, Depth of immersion Center of gravity of float, G Center of buoyancy, B
weight of water displaced
Density of sea water x volume of
water displaced x 9.81
1025 x 4x4 x (depth of
immersion) x 9.81
304.10mm
500mm from bottom
(Depth of immersion)
Area moment of inertia, I +
304.10 2
152.1 mm from bottom bxd3
b-d
21.13 x 10i3 mm4
Volume of immersed part, V
Area x depth of immersion 100x4000x304.1 4.86 x 106mm3
Distance BG
500.152.1 347.9 mm
M is the metacentric point. M is the point about which the body tills or
oscillates when an unbalanced force acts pm the body.
Distance, GM = 1/V BG
GM
Also GM
2.13 x 1013 4.86 x 109 4034.8 mm
(wx) WTanG
347.9
(wx) - moment acting = W - total weight
25.272 x KfNmm 48926N
(wx)
W * GM
25.272 x 106
48926 x 4034.8
0.128
7.29
BG + GM 4382.7 mm 347.9 mm
0 - Angle of tilt when the load is applied Tan 6
9
For the safety of float, BM > BG Here BM
BG
Clearly BM >BG
Float is in a state of stable equilibrium
Water Level
Float
7.5 MECHANISM OF ROTATING BEAM
The beam is to be rotated 360 at a rate of 1 rpm. The mechanism used for is a chain drive. The reason for selecting chain drive is due to its simple construction, easy installation, comparatively lower cost and less maintenance required.
Design Procedure
Speed ratio selected = 3
Type of Chain = Roller chain
From PSG design data, for gear ratio of 3, number of tooth on sprocket of pinion, Zi = 24.
Pitch selected, P
Centre distance between the
two sprockets, s Teeth on sprocket of wheel Diameter of small sprocket di
Diameter of large sprocket d2
Linear velocity of the chain V
15.875 mm '
40 p = 635 mm xZi = 75
P +
Sin(180/Z,) 126.7 mm
P + Sin (180/Zi) 380 red, N!
15.875
Sin (180/25)
15875
Sin (180/75)
Load factor Ki
Factor for distance regulation K2 = Factor for center distance
of sprockets K2
Factor for position of sprockets K3
Lubrication factor K5
Rating factor K6
60
TIX 126.7x50 60
331.7 mm Is
1 (Assuming constant load)
1.5
Service factor K5 = K, K2 K3 K4 K5 K6 = 1.5
Factor for safety selected, n = 7
Power transmitted, P = 2 TC NT
60
T-moment acting = 25.272 x 103 Nm
Rpm, N = 1
P = 2TTX 1 x 25.272 x 103
60
2646.26 W
p = 3.6 hp
Power transmitted P O x V
75.n/Ks
Breaking load O P x 75 x n x Ks
V
3.6x75x7x 1.5
0.3317
Q = 8536.10 Kgf
Corresponding to this breaking load and the pitch, a single strap chain is not available.
Q/2 4268.05 Kgf
Corresponding to this breaking load, chain type to be selected is double strap ISO 10A-3 chain or Tolon TR 50.
A power control panel is fixed on the float. The power required for the operation of the pump and the winch is taken from the port through cables. Power is given to the winch and the pump through and control panel. Control panel consists of switches to control the winch. The starter for the operation of the pump is also installed on the controlled panel.
The float may come very close to the gate or nearby areas for effective dredging. A slight contact between the float and the gate, should not cause any damage to either part. For this, a synthetic rubber fender is fixed along the outer perimeter of the float. This fender provides a cushioning effect and protects the float and any other object in cases of a slight collision.
8. ALTERNATE USE FOR THE NEW SYSTEM
Although we have designed the dredger system specifically for the dock frontage dredging. It can be used for other purposes also. The system has been designed in such a way that the entire frame work can be detached from the float at the bearings.
Thus when there is no dredging, work, the frame work and the chain mechanism can be detached. The float can be use for carrying loads. The maximum load carrying capacity of the float after the removal of framework, pump and chain mechanism is 1.3 tons
9. CONCLUSION
The limitations of the conventional dredging systems for dry dock frontage dredging were studied and a new system was designed. During its design safety, cost and availability of material were considered. Thus the new system is used to dredge the dock frontage regions most effectively. The system can also be used for other purposes.
10. REFERENCES
1. Modi, Dr. P. N; and Seth, S.M., Hydraulics and Fluid Mechanics, Standard Book House; 15th ed., 2004
2. Khurmi, R.S., Machine design, 1st Multicolor ed.m, S. Chand, 2005
3. Gupta, Dr. A.B, Practical Hand Book for Mechanical Engineers,9th ed., Galgotia publications, New Delhi, 2002
4. Ramamrutham, s, Strength of Materials, 11th ed., Dhanpat rai & Sons, 2000
5. PSG Design Data Book