structural design of drydock frontage dredging system

8/6/2019 Structural Design of Drydock Frontage Dredging System

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STRUCTURAL DESIGN OF DRYDOCK

FRONTAGE DREDGING SYSTEM

PROJECT REPORT

Submitted by

ELDHO PAUL JOBIN JOSE

SREEKUMAR S. VINEESH

T.V.

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.

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.

3



SPECIFICATIONS

APPROACH CHANNEL

Outer channel length 1 OOOOmts

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

4

INNER CHANNEL

Length

Draft

Width



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.

7



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

8



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

10



11



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

13

TypeDP - 10H-1Head20mCapacity0.8m3/minMax. sizesold14mmMotor output7.5kwPoles4Frequency50HzWeight240kg

Table 6.1: 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

" t S 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. BE ARI NG , 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 S LEEV E 1 SP. STEELNo. PAHTS NAME QTY MATERIALS

31 OIL SEAL ~\

32 OIL CHAMBER COVER 1 . FCD503

13 PACKING 1 RU9DER3-1 SET DOLT SSJOC

35 UNDER COVER 1 FC250

3S KEY 1 S45C3/ IMPELLER 1 HCR

30 CASING 1 F CO 500

33 IMPELLER COLLAR 1 S25C

40 IMPELLER NUT 1 ss-ioo

41 SUCTI ON CO VER 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

4 7 SET BOLT SS400

49 O IL INLET PLU G

51 PACKING 1 RUBBER

52 BENO 1 FCOSOO53 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-1DP-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

15



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.



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.

rFigure 6.6: Free body diagram of beam The equation for

deflection at any distance 'X' is given by

EIyD = Wv 2 6

= 11.772xl0

3

= 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.

21

4.2x

Figure 6.7: Free body diagram of beam



E Iy D = — { 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

R(7.717)

EI -----------

(l)+(2)+(3)=0

90.85xl03 + 3.444xl03 - R (7.717)=0 R=

12.22x103 N

(3)yD =



= 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 = 7 i (D4-d4) = 7t (127 4 -U0 4

)

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.

23



From Figure

R l = R cosG

= 12 x 103xcos60 =

6xl03

Pj = R 1cos60

= 6x 103xcos 60 = 3000 N R h

= R 1 cos 30

= 6 x 103xcos30

= 5196N

Moment due to R h at B, M = R ^ xl

= 5.2x1 =

5.2KNM

= 5.2xl06 NMM

Net moment = 25.27x 10 6- 5.2x106

= 20x 106 Nmm

P2 =20x 106

P!=^I9: =.4761.9N

4200

Slenderness ratio of the column:

7.1.2 COLUMN DESIGN

Figure 6.9: Free body diagram of

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 = 1 3 5 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 ( o 2 - d 2 )4

n

/A (l52.42

-1352

) =

3927.6mm2

Then for eccentrically loaded column according to Eulers formula, max. compressive stress,

25



AP P2.e------1------secA Z

(P

~ A

L x.P-VE I

L = column length = 1000 mm Z =

section modulus K

D 4 -d 4

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

P P e — + sec A Z

4762

47623927.6 133531.4

Sec 100476

2

EI

o c = 0.764 + 1.212 + 149.8xl =

151.7 N/mm2

Corresponding to this o c 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)

26

LxiEI

4200+



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 3164.37x280r

280 21472^

4T X2

X 4X 2X 10542

where A

865.5 KN

3164.37 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 (d 04 -d i 4 )

27

2147 mm

40 mm

4 for two ends fixed column 2

x 105 N/mm2

1 - ay (l/K ) 4

7t2 n E



do

TI/32 (1824- 152.44) 182

3 00.869 x 103 mm3

28



Bending moment, M = 25.272 x 106 N mm

[ab] = M 25.272 x l O 6 = 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 mmand 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 P x L

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 DimensionsShear 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 stressin the bolt, at

ay

2.5

30 bolt x 4

2 (6822+ 1002)

18137.90N P"



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 = y h + T 2

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.

a\



Chann

els

Equal angfc

ironFigure 6.11: Frame work of the

float

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

(4 x 4 )m 2 x 2 + ( l x 4 )m 2 x

4+ (1.3 x 1.3)m2x 1 49.7 m2 48

x 49.7 2385.2 Kg.

Sheet metal used ,

Place thickness = 6 mm

Weight/area = 48 Kgf/m2

Total area of steel metal used =



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

8 x 4 m x 4 x l . 9 m + l x l .3m

40.9 m 7.14x40.9 292.03 Kg

33.7mm

25mm 2.93

kgf/m l m

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 4 x 4 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

bxd 3

b - d

21.13 x 10i3 mm4

Volume of immersed part, VArea x depth of immersion

1 0 0 x 4 0 0 0 x 3 0 4 .

1 4.86 x 106mm3

Distance BG500.152.1

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)

WT an G

347.9

12

400mm



(wx) - moment acting =

W - total weight

25.272 x KfNmm

48926N

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

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 chainFrom 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 sprocketd2

Linear velocity of

the chain V

(wx)

W * GM

25.272 x 106

48926 x 4034.8

0.128

7.29°

BG + GM

4382.7 mm

347.9 mm

Water Level

Figure 6.12 Float in stable Equilibrium G-Centre of gravity

B-Centre of

buoyancy M-

Metacentre

Water Level



15.875 mm '

40 p = 635 mm x Zi = 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 K 2 =

Factor for center distance

of sprockets K 2

Factor for position of sprockets K3

Lubrication factor K5

Rating factor K6

60

T I X 126 .7x50 60

331.7 mm I s

1 (Assuming constant load)

1.5

Service factor K 5 = K, K 2 K 3 K4 K 5 K 6 = 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 = 2T T X 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

3.6 x75 x7x 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

structural design of drydock frontage dredging system

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