operating instruction 6250t floating dock

Operating Instructions: 6,250 TLC Floating Dock

Doc No. NSRY1-0-22-0002 Rev A

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Consultant:

Clark & Standfield Limited

Document No CP3978-803 Issue

ERHAMA BIN JABER AL JALAHMA SHIPYARD

PORT OF RAS LAFFAN, QATAR

Project Manager:

Client:

Document No: NSRY1-0-22-0002

ERHAMA BIN JABER AL JALAHMA SHIPYARD

PORT OF RAS LAFFAN, QATAR

OPERATING INSTRUCTIONS FOR

6250 LIFT CAPACITY FLOATING DOCK

A 05.11.12 First Issue DMW AMacV DMW Rev Date Revision Description Written by Checked by Approved by



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FOREWORD

The information in this manual has been supplied by:

Clark & Standfield Limited Floating Dock Engineers Unit 21, Sir James Clark Building Abbey Mill Business Centre Seedhill, Paisley PA1 1TJ, Scotland, U.K.

Tel: + 44 (0) 141 887 4131 Fax: + 44 (0) 141 887 6437 Email: [email protected] URL: www.lobnitz.com

The information supplied in this manual is for guidance only and does not free the Dockmaster from his responsibility of ensuring adequate stability and safe operation in all conditions of operation.

When a new Dockmaster takes command of the dock the manual should be transferred into his keeping.

The operating manual gives guidance in docking ships under ordinary conditions. For unusual conditions the docks designers, Messrs Clark & Standfield, should be consulted.

Warning

This a provisional document and is to be updated after commissioning trials to reflect the As Built Lightship Weight and Centre of Gravity and any other areas that may be affected by variations between design and As Built particulars, for example stability, deflections, etc.

The information provided in this booklet is on the basis of cranes being fitted. Final booklet to reflect final quantities of cranes fitted.



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CONTENTS

Foreword ..........................................................................2 Contents .............................................................................3

1 RESPONSIBILITIES ....................................................4

2 PARTICULARS OF THE DOCK ...................................... 4

2.1 Dock Type ............................................................4 2.2 General Dimensions of the Dock ...........................4 2.3 Port and Starboard Sides of the Dock ...................4 2.4 Capacity of the Dock ..........................................4 2.4.1 General .................................................4 2.4.2 Dockwell Dimensions...........................5 2.4.3 Deep Sink Draught...............................5 2.4.4 Lifting Capacity.......................................5 2.4.5 Freeboard ................... 5 2.4.6 Stability...................................................5 2.4.7 Maximum Distributed Load...................5 2.4.8 Longitudinal and Transverse Strength...................5 2.4.9 Pontoon Deck and Apron Loading...................5 2.4.10 Water Density .............................................5 2.5 Depth Measuring Equipment ...............................6 2.5.1 Ballast Tanks..........................................6 2.5.2 Depth Gauges (Control House) ......................6 2.5.3 Draught Boards........................................6 2.6 Optical Deflection Sight......................................6 2.7 Dewatering System .............................................7 2.8 Control House Control Console.....................................7 2.9 Loss of Power 8 2.10 Contaminated Water Tanks ..8 2.11 Weather Conditions .8 2.12 Tidal Restrictions 8

3 PREPARATION OF THE SHIP FOR DOCKING ....................8

4 PREPARATION OF THE DOCK TO RECEIVE A VESSEL ................................................................................

7

4.1 Docking Plans ............................................9 4.2 General Principles to be Observed in Placing the

Ship.....

9 4.2.1 Longitudinal Position .9 4.2.2 Transverse Position 9 4.3 Pumping and Flooding Plans.9 4.3.1 General 9 4.3.2 Objectives 9 4.3.3 Ship Weight Distribution ..10 4.3.4 Preparation of Pumping Plan .10 4.3.5 Knuckle load .11 4.3.6 Stability ..11 4.4 Dock Blocks and Cappers.11 4.4.1 The datum Plane..11 4.4.2 Arrangement of Blocks ..11 4.4.3 Keel (Centre Line) Blocks..12 4.4.4 Bilge Blocks.12 4.4.5 Miscellaneous..12 4.4.6 Dock Block Loading.12 4.4.7 Timber12 4.4.8 Dock Block Stability13 4.4.9 Hull Preservation13

5 DOCKING AND UNDOCKING ........................................13

5.1 Docking Down ...........................................13 5.2 Precautions in Dock .....................................14 5.3 Undocking ...............................................14 5.4 Correction of List and Trim in the Ship .................14

6 DOCKING OPERATION ............................................14

6.1 Precautions .............................................14 6.2 Preparation ...............................................15 6.3 Docking .15 6.3.1 General ...................................15 6.3.2 Sinking .......................................15 6.3.3 Deep Sink .16 6.3.4 Pumping out the Dock ..........................16 6.3.5 General Considerations ..........................16 6.4 Raised ...............................................17 6.5 Undocking ...............................................17

6.5.1 Preparation .....................................17 6.5.2 Sinking .......................................17

7 SPECIAL PRECAUTIONS ........................................18

7.1 Docking of Damaged Vessels ..............................18 7.1.1 Position in the Dock ...........................18 7.1.2 Vessels with Heel or Trim .......................18 7.1.3 Vessels Seriously Damaged .......................18 7.1.4 Vessels with Damaged Bottom Plating18 7.2 Docking Ships with Considerable Trim ....................18

8 CAREENING THE DOCK .18

8.1 Method to be Adopted ...................................18 8.2 Cranes ...................................................18 8.3 Miscellaneous ............................................18

9 Figures 19

Figure 1 Dock Profile .20 Figure 2 Forward End Elevation Looking Aft .21 Figure 3 Dockwell Dimensions and Blocking 22 Figure 4 Weight to Block Length Curve 23 Figure 5 Ship Weight Centre of Gravity Curve 24 Figure 6 Maximum Allowable Hydrostatic Heads ..25 Figure 7 Optical Deflection Sight ..26 Figure 8 Dewatering System .27 Figure 9 Vessel Distributed Load on

Compartments Weight Curve Available 28

Figure 10 Vessel Distributed Load on Compartments Weight Curve Unknown

29

Figure 11 Dock Ballasting to Match Ship Distributed Load

30

Figure 12 Docking a Vessel with Heel .31 Figure 13 Docking a Vessel with Trim ..32 Figure 14 Standard Keel Block 33 Figure 15 Dock Block Arrangement 34 Figure 16 Examples of Block Placement 35

10 APPENDICES.................................................36

Appendix 1 Standard Ship weight Distribution 37 Appendix 2 Ballast Tank Air Pipes .38 Appendix 3 Pumping Plan Exampe39 Appendix 3 Lift Tables ..40



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1 RESPONSIBILITIES

Before attempting to operate this dock, it is essential that the personnel directly responsible for operating the dock (especially the Dockmaster) make themselves thoroughly acquainted with the pumping and flooding systems of the dock and the control system for pumps and valves as fitted in the control house.

The Dockmaster is to have a competent deputy to assist him in the control house, and who is to be trained to relieve the Dockmaster. The dock control system is provided with a Black Box recording system to monitor the dock status throughout a docking evolution recording deflection, draughts at corners of dock, trim and list of dock, state of tanks, pumps in use, compartments being pumped or flooded, the operation of the isolating valves, stoppages for block inspections.

The company responsible for the dock is to see that the Dockmasters organisation of the crew is efficient for immediately dealing with such emergencies as loss of power, and consequent immediate loss of control of operation, sticky valves or pump failures, etc. in order to ensure the safety of both the dock and the ship being docked.

The company responsible for the dock, the Dockmaster, and the engineer responsible for docking the ship, are to make themselves thoroughly acquainted with the following instructions as to the preparation of the dock to receive a ship, and as to the position of the ship in the dock. The safety of the dock is not to be hazarded by a risky docking operation.

Longitudinal deflections, large trims, lists and twists are not to be allowed to develop. In an emergency, if necessary, stop the whole operation by speedily closing down pumps and valves. Consider all factors and decide whether to proceed with pumping, or sink the dock and refloat the ship. The Dockmaster is to consult the engineer immediately in charge of the docking and the company, if necessary, and obtain their concurrence in any such decision.

The Dockmaster is to ensure that when ships are docked the appropriate Safety Precautions are strictly followed.

2 PARTICULARS OF THE DOCK

2.1 DOCK TYPE

The dock is of the box or caisson type, non-self-docking, and consists of one continuous pontoon with two sidewalls mounted on top and is of all welded construction. The dock is suitable for service in sheltered conditions.

The dock is subdivided by six watertight bulkheads longitudinally and three watertight bulkheads transversely, providing a total of 24 water ballast compartments and a cross dock duct.

The dock was designed by Clark & Standfield in accordance with the requirements of Lloyds Rules Rules and Regulations for the Construction and Classification of Floating Docks.

2.2 GENERAL DIMENSIONS OF THE DOCK

Table 1 Dock Particulars Particulars Dimension

Overall length of dock (including end platform) ...........................................................................163.13 metres Overall length of dock over pontoon (mld) ........................................................................149.94 metres Overall width at pontoon deck level (mld) .......................................................................35.00 metres Overall width including mooring columns ............................................................38.75 metres

Clear width of entrance between fenders .......................................................................26.00 metres

Depth of pontoon at centreline (mld) .......................................................................3.40 metres Depth of pontoon at inner sidewall (mld)............................................................3.25 metres Length of sidewall 149.94 metres

Height of sidewall above pontoon at inner sidewall . Mld10.95 metres

Depth of tween deck space (mld).4.00 metres Width of sidewalls (mld) 3.50 metres

Draught of water over keel blocks ..7.00 metres

Corresponding Freeboard of Sidewalls 2.00 metres

Height of Keel Blocks .1.80 metres

Dock Draught at Maximum Deep Sink (moulded) ..12.20 metres (extreme *) 12.80 metres * Projection of mooring column support structure Maximum Lift Capacity .6,250 tonnes

Lightweight (incl 95% FW Tanks, gangways) 6573 tonnes Lightweight KG .6.817 metres

Lightweight Draft ..1.210 metres

Lightweight Draft (incl Residual Ballast) .1.592 metres

See also Figures 1 & 2

2.3 PORT AND STARBOARD SIDES OF THE DOCK

The side of the dock on which the control house is situated is hereafter called the port side. The control house is situated towards the forward end of the dock (Shore End).

2.4 CAPACITY OF THE DOCK

2.4.1 General

The capacity of the floating dock is limited by the following

(a) Dimension of dockwell (b) Deep Sink Draught (c) Lifting Capacity (d) Stability (e) Maximum Distributed Load

Before a vessel can be considered for docking the Dockmaster should ensure that the following criteria defined below can be met.



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Typically, the maximum ship particulars that can be accommodated are:

Table 2 Maximum Allowable Dimensions of Vessel Docking Displacement 6250 tonnes

Maximum Length (see note #1) Approx 160.00 metres Maximum Blocking Length 147.56 metres

Max Beam (see note #2) 25.00 metres Maximum Draft ( See note #3) 6.50 metres

#1 Length over pontoon and Aft end apron. However, may be greater see cl 2.4.2 below

#2 determined using 500mm clearance iwo entrance fenders #3 determined using 500mm clearance on 1.80m high blocks

2.4.2 Dockwell Dimensions

The dockwell dimensions are set out in Figures 1, 2 and 3. The Dockmaster should ensure that the following clearances can be met:

500mm minimum clearance around the hull and any projections.

There is no length restriction, as the dockwell is open ended. However,

a) Extensive overhangs require further investigation, particularly in regard to the longitudinal strength of the vessel being docked and blocking loads.

b) The flying gangways at the forward end will require being in the open position.

c) The road access ramp will limit the forwardmost extent that a ship can be positioned on the dock.

2.4.3 Deep Sink Draught

The dock is designed for a deep sink of:

Draught (mld) at Deep Sink 12.200 metres Depth over pontoon at centre 8.800 metres Depth over 1.80m Blocks 7.000 metres

When the vessel enters the dock the minimum clearance over the blocks to the underside of keel is 500 mm. Special considerations may be given in exceptional circumstances to reduce this to 300mm but under no circumstances to any lower.

2.4.4 Lifting Capacity

The maximum lifting capacity of the floating dock, with a working pontoon freeboard of 450mm at dock centreline, is:

6250 tonnes

When a vessel is docked in a floating dock the disposition of her weight in the dock must be carefully considered to avoid straining the structure of the dock.

The maximum lift capacity is for a Pontoon freeboard of 450mm at the centreline. When the dock is used in exposed areas it may be necessary to increase the freeboard with consequent decrease in lifting capacity.

2.4.5 Freeboard

The mean normal working freeboard to the pontoon deck at the centreline is 450mm. This is sufficient to

accommodate the 100yr maximum significant wave height, Hs, of 0.80m at the shipyard within Ras Laffan Harbour.

The minimum permissible freeboard is 300mm at centreline when floating level. The maximum permissible trim due to ballasting, movement of cranes or additional loads (e.g. trucks, repair gear) should not result in any part of the pontoon deck becoming immersed.

Consideration should be given to increasing freeboard in poor sea conditions or if pontoon manholes are opened to permit access into the pontoon for inspection.

The minimum allowable freeboard in the submerged condition is 2.000m to the top deck at any position along the dock. The depth that the dock can be sunk is limited by an air cushion in the side tanks so that the maximum draft cannot be exceeded. This can be adjusted by the extent the air pipes protrude into the tanks. These will have been set during the docks original commissioning trials. Under no circumstances should these air pipes be adjusted except when they need to be reset to accommodate weight changes to the dock lightship weight. Freeboard marks are provided on the sidewalls of the dockwell for this purpose.

2.4.6 Stability

Minimum stability occurs during the raising of the dock, the GM of dock and vessel combined should never be less than 1.50m (NB Lloyds Register use 1.00m). A significant increase in stability will occur once the pontoon deck emerges above the waterline. The Dockmaster, in determining the maximum permissible centre of gravity of a vessel to be docked, should refer to the ship weight centre of gravity curve, see figure 5, and Table 3 below. This Curve is based upon a minimum GM of 1.50m with a keel block height of 1.80m. Values, which are close to the weight centre curve, should be examined in more detail. See also section 4.3.6

Table 3 Maximum Allowable KG of Vessel

Ship Weight KG Ship Weight KG tonnes metres tonnes metres

250 722.728 3750 45.107 500 359.878 4000 42.058 750 238.912 4250 39.366

1000 178.416 4500 36.969 1250 142.109 4750 34.823 1500 117.896 5000 32.888 1750 100.594 5250 31.136 2000 87.611 5500 29.540 2250 77.507 5750 28.081 2500 69.420 6000 26.742 2750 62.798 6250 25.507 3000 57.276 6500 24.366 3250 52.599 6750 23.307 3500 48.587 7000 22.323

2.4.7 Maximum Distributed Load

The maximum longitudinally distributed load of the vessel should not exceed

a) For Centreline blocking:

100 tonne/metre over block length on centreline longitudinal bulkhead



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b) For Offset Docking:

40 tonne/metre along a line 4200mm off dock centreline, port and starboard

As a quick guide, the minimum blocking length is given in the weight to block length curve shown in figure 4. This curve takes into account distributed load and longitudinal bending moments.

Where values are near to the limit, a more detailed investigation should be carried out. Procedures for determining the ships longitudinal weight distribution are outlined in cl. 4.3.4

2.4.8 Longitudinal & Transverse Strength

The Midship Section Modulus for this dock is 4.96m3

The maximum permissible Stillwater Longitudinal Bending Moment in accordance with Lloyds Register is:

43,015 tonne-metres (421,830kNm)

The dock is designed for differential ballasting longitudinally for the reduction of longitudinal bending moments and deflections. The maximum permissible Stillwater Bending Moment is expected to produce a longitudinal deflection of 70mm (actual value to be determined by trial)

The dock transverse strength is designed for level ballasting transversely and to accommodate a load on each transverse of 357 tonnes either at the centre line or distributed.

2.4.9 Pontoon Deck and Apron Loading

(a) Pontoon Deck

The pontoon deck is designed to accommodate the following loadings:

HA Vehicles Forklift Trucks up to 17 tonnes Gross Weight

The Pontoon deck is stiffened and framed to provide strong points for the provision of dock blocks. Their positions are covered in section 4.4.2.

(b) Aft End Apron

The Aft End Apron is designed to accommodate the following loadings:

Forklift Trucks up to 17 tonnes Gross Weight

The aft end apron may carry Forklift trucks providing not more than 1 truck is carried at any one time by apron area 10m long by 3m wide (transversely with respect to the dock). HA Vehicles or fork lift trucks exceeding 17 tonnes are not permitted. Dock blocks should NOT be used to support vessels on the apron.

2.4.10 Water Density

The density of sea water used in the production of this document has been taken as 1025 kg/cu.m.

2.5 DEPTH MEASURING EQUIPMENT

2.5.1 Ballast Tanks

Ballast Tanks use a pressure sensor located low down in the tanks. These pressure readings are converted to depth of water and displayed on VDUs in the control house.

The depth of water in a tank is limited by the position of the air pipe opening and this has been pre-set to permit the dock to reach, but not exceed, the deep sink draught with all ballast tanks open to the sea.

Note: When the water level is higher than the air pipe opening the trapped air presses up and the tank gauge no longer gives the correct water level reading. However, more importantly, the difference in readings between tanks will give the correct hydrostatic head on the tanks boundary bulkheads.

Ballast tanks are provided with sounding pipes in way of the safety deck. These sounding pipes are provided with self-closing covers and cap. These must ALWAYS be closed during sinking and raising the dock and must NEVER be opened during docking operations. NB once the tank level is higher than about 8m, opening the sounding pipe risks loss of air cushion and flooding of the tween deck space.

2.5.2 Depth Gauges (Control House)

The draught of the dock is measured by pressure sensors at the four corners of the dock, and each side midships.

2.5.3 Draught Board

The dock is provided with draught boards at each end of the dockwell (port and starboard) and midships giving the depth of water over the dock pontoon deck at centreline.

2.6 OPTICAL DEFLECTION SIGHT

An optical sight is fitted to the top deck of the Port Sidewall See figure 7. It consists of a telescope in the Control House aimed onto sight boards at the middle and at the end of the wall. The longitudinal deflection in the vertical plane of the top of the Port Sidewall is given by the scale reading on the middle sight board related to the sight line on the end sight board. (The position of the crosswires in the telescope can be ignored, where fitted). The purpose of the sight is to indicate the trend of the longitudinal deflection of the pontoon and thus the shape of the keel blocks and the forces and bending moments on ship and dock during the operation of the dock. It should be noted, however, that the relative stiffness of pontoon and side walls, effects of temperature and solar radiation and disposition of local loads can result in the actual deflection of the top of the side wall in the vertical plane being different not only in magnitude but sometimes in sign from the vertical deflection of the centre of the pontoon. The change of deflection seen through the sight should, therefore, be minimal. The sight is, therefore, monitored at frequent intervals.

It should be the aim of the Dockmaster to endeavour to keep the sight line through the middle of the White Band (i.e. Black horizontal line) corresponding to no deflection.

If unexpected deflections develop the operation should be halted until an explanation can be found. Typical causes would be:-

(a) A sunny day distorting the side walls (b) A large difference between air and sea

temperature (c) An inaccurate tank gauge possibly coupled with

a valve not opening or shutting correctly or a pump operating below its correct performance.

(d) Lack of fit between blocks and keel of the vessel due to, for example, an unfair keel or an incorrectly aligned cradle.



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The markings on the sighting board, also see figure 6, have the following meaning

Red Band

DANGEROUS SAGGING: Deflection exceeding maximum permissible. Under no circumstances must the sight line be allowed to go into the red band. If it does, immediately halt the docking operation and consider carefully method of reducing deflection.

White Band Normal Operating Zone: To be observed every 10 minutes during operation. Dock Sagging

Horizontal Black Line Zero longitudinal Deflection

White Band Normal Operating Zone: To be observed every 10 minutes during operation. Dock Hogging

Red Band

DANGEROUS HOGGING: Deflection exceeding maximum permissible. Under no circumstances must the sight line be allowed to go into the red band. If it does, immediately halt the docking operation and consider carefully method of reducing deflection.

In no circumstances must the sight line be allowed to go into the Red Band on the middle sighting board.

2.7 DEWATERING SYSTEM

The dock has 24 ballast tanks which are used to

(a) Raise or Sink the Dock (b) Control Trim and Heel (c) Control Longitudinal Deflections.

The layout of these tanks is shown in figure 8 together with the dewatering/flooding system. Sinking of the dock is by free flooding the tanks, whereas raising is by pumping the tanks. The dewatering system consists of:

(A) Inlet Valve (4 off)

These screw-down gate valves are operated from the control house. They have variable opening and use electric motor actuators.

(B) Discharge Valve (4 off)

These screw-down gate valves are operated from the control house. They have variable opening and use electric motor actuators.

(C) Compartment Valves (24 off)

These valves control the flooding/dewatering of each ballast compartment and are operated from the control house. They are electro-pneumatically operated

(D) Isolating(Separation) Valves (4 off)

These valves connect the dewatering/flooding system of one group of compartments with neighbouring groups. Valves are normally kept closed. Valves are operated by electric motors. They are only opened in the event of a pump failure to enable an adjacent pump to undertake the duty of the failed pump.

(E) Non Return Valves (4 off)

These valves are located between the discharge valves and the pump and are provided to prevent backflow past the pump. They also prevent flooding if the pump has stopped whilst the discharge valve is being closed.

Compartment valves are operated by an electro-pneumatic system with air provided by a shore main. All other valves use electric motor actuators.

In the event of power failure, battery backup is provided to operate the valves sufficient for at least 30 minutes of dock operation. In addition, all valves have the facility for manual operation. Valve actuators are located on the safety deck above each of the four pump rooms.

2.8 CONTROL HOUSE CONTROL CONSOLE

The dock is controlled during docking evolutions from a control console provided in the control house. From here, the following are:

Push Button Controls: Inlet Valves Open/Intermediate/Close Discharge Valves Open/Intermediate/Close Compartment Valves Open/Close Isolating Valves Open Close Pump Motors Stop / Start Contaminated Water Tank Drain Valve

Open/Close

Emergency Stop Closes all valves Berthing Trolley Winches Fwd/Reverse/Stop

Monitoring: (VDUs) Inlet Valves Open/Close/Percentage Open Discharge Valves Open/Close/Percentage Open Compartment Valves Open/Close Isolating Valves Open/Close Pump Motors Ammeter /Running/Stop/Fault/Live Compressed Air System Pressure Ballast Tanks Tank Level Indication Contaminated Water Tanks Tank Level Indication Freshwater Tanks Tank Level Indication Dock Draught Draft/Trim/Heel/Deflection Meteorology Wind/Pressure/Temperature Fire Main Pressure Berthing Trollies Position, Ammeter Boundary Bulkheads Hydrostatic Head on Ballast Tank

Boundaries

The control console also contains other features such as communications, utility service pressures etc. but do not form part of this operating manual.

The dock is provided with an automated docking control system enabling the dock to be automatically pumped up to user defined waterlines. The details for this system are beyond the scope of this operating manual which defines the manual operation of the dock, although the automated system will follow similar procedures. For details of the use of the automated docking system, the manufacturers literature should be referred to.

2.9 LOSS OF POWER

The Dock is dependent on shore supplies for electrical and compressed air services. The electrical services are provided with an onshore emergency generator for supply to the shipyard facility.



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a) Loss of Electrical Power

In the unlikely event that there is a complete loss of electrical power to the dock, the dock is provided with battery backup for a minimum 30 minutes of dock operation of the compartment valves and dock control system. This will enable sufficient time to bring the dock to a safe condition (i.e. level the dock up and remove deflections, or if in the early stages of a lift, to refloat a vessel being docked) after which all valves shall be closed.

During a power failure, the dock will not be capable of being pumped and all adjustment to the dock must be made by free flooding of the tanks. If the power failure is likely to be lengthy, the dock is provided with a shore power connection for hooking up an emergency portable generator to the port Switchboard for the purpose of recovering the dock.

All dewatering system valves are capable of manual operation.

b) Loss of Compressed Air Services

Loss of compressed air services only affects the compartment valves, as all other valves are operated by electric motorised actuators. These valves are fail safe (i.e. shut) on loss of compressed air, or loss of electric control signal. However, these valves are provided with manual backup.

2.10 CONTAMINATED WATER TANKS

To prevent pollution of the harbour water, the dock is provided with a contaminated water collection facility. A grated trough is provided at the forward end of the dock at the side of the pontoon deck, one port and one starboard. An upstand is provided running across the forward end of the dock to prevent contaminated water running off the end of the pontoon. The troughs drain to collection tanks in the sidewall, one port and one starboard.

The tanks are provided with an automatic pumping system with hi-low switch to pump the contaminated water ashore.

When submerging the pontoon during docking evolutions, it is necessary to prevent large amounts of seawater entering the contaminated water tanks, or the drain pipes between the troughs and the tanks. The drains from the troughs are provided with a closing valve which should be closed when submerging the dock to prevent water entering the tanks. In addition, a cap is provided in way of the drain hole in the troughs which should also be closed during submergence to prevent large amounts of seawater in the drain pipes..

The tank structure has been designed for any accidental flooding during docking operations.

For operation of the pontoon deck collection facility, it is necessary to ensure that the dock is trimmed by the head.

The dock bilge system for pumping the cross dock duct and pump rooms are designed to pump into the contaminated water tanks.

2.11 WEATHER CONDITIONS

The dock has been designed to accommodate a wind speed in any direction of 59mph (100 year return) with the dock at an operational freeboard of 450mm.

In the event of higher winds the dock should be lowered and any docked vessel removed.

Docking evolutions should be carried in wind speeds not greater than 20mph.

The 100 year return significant wave height is 0.80m which should not require any adjustment to the operational freeboard of 450mm at dock centreline.

2.12 TIDAL RESTRICTIONS

The dock has been designed to accommodate a full range of draughts from dock lightship (with no ballast) to deep sink draft for tidal conditions ranging from:

+0.13m CD Lowest Astronomical Tide +1.86m CD Highest Astronomical Tide +2.20m CD Future Design High Water Level

There is no restriction on dock operation for any tide level within the above range.

3 PREPARATION OF SHIP FOR DOCKING

Before a vessel enters the dock the ship's officers and dockyard personnel are to make the following preparations:

(a) Clear all bollards and fairleads in the ship and lay out numerous heaving-lines along the ship's side in readiness to take dockyard wires.

(b) Turn in or top up all derricks, davits, accommodation ladder platforms, leadsmen's chains, deck cranes and any other items which project beyond the ship's side and are likely to foul dock cranes, dock wires, etc. Close up anchors.

(c) "House" bottom logs, stabilizers, and sonar domes, unrig bottom lines, and remove any other projections under the bottom which are likely to foul the dock blocks. Lock the rudder at zero helm, and turn and, where propellers extend below the keel line, lock the propellers so that maximum clearance is obtained over dock blocks and other obstructions unless instructions are received to the contrary.

(d) Bring ship to an upright position without undue trim and to the draughts specified by dockyard personnel.

(e) Check the draughts immediately before the ship enters the dock.

(f) Take steps to see that no weights are moved or water taken in, transferred, or pumped overboard during the docking operations.

(g) Close all side scuttles, square ports, etc., and furl awnings.

(h) For naval ships, magazine and main service flooding bonnets are held in readiness to be fitted if required.

(i) Positions of shores, if required, are marked on the weather deck edges or hull and, where applicable, the centreline of the ship is marked on the transom.



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4 PREPARATION OF THE DOCK TO RECEIVE A VESSEL

4.1 DOCKING PLANS

Before commencing any docking operation it must be established that the dock is capable of accommodating the ship. Each ship usually has a set of drawings called the DOCKING PLAN, a copy of which is held by the ship or owners technical department. The docking plan consists of a PROFILE and PLAN and a BODY PLAN. The following information is contained:

(a) GENERAL

1. The position of all decks and bulkheads at ship's side and principal longitudinals, stringers and WT frames.

2. Draught marks as set off on the ship.

3. The extent of docking keels, bilge keels and stabilisers.

4. All projections on the outside of the ship such as rudders, propellers, shaft brackets and shafting, sonar domes, bilge keels and stabilisers.

5. The positions most suitable for the heads of all shores and also the positions where special shoring or additional docking blocks are considered necessary.

6. The position and weight of any permanent ballast fitted.

7. The position and size of principal holes or openings in the bottom.

8. Information on shaped side blocks for docking in a dock without breast shores.

9. Length of the ship overall and between perpendiculars.

(b) BODY PLAN

1. Midship section including projections and a section drawn at each shore/bilge block position.

2. Section in way of propellers showing sweep and dimensions.

4.2 GENERAL PRINCIPLES TO BE OBSERVED IN PLACING THE SHIP

4.2.1 Longitudinal Position

Vessels whose longitudinal position on the dock are not pre-determined (by a cradle or other specific instructions) are to be placed in the dock such that the meaned curve of its weight over each discrete longitudinal section of the dock gives the minimum variation of ballast water along the length of the dock and in no case requires the differential head in any tank to exceed the values given in Section 6.1. If the length of the vessel allows, the end tanks should be clear of the vessel so that they can be retained for trim adjustments during the operation of the dock.

Generally, the ship should be placed so that the common centre of gravity of the dock and ship is over the centre of buoyancy of the dock when level. When the weight of the ship approaches the limit of the lifting power of the dock, this is essential. There may however, be special cases of

ships with abnormally long overhangs leading to high loadings in the way of the cut-up, which make it necessary to consider pitching the cut-up to minimise the longitudinal dock stresses.

In addition, bending moments and stresses can be better reduced if the vessel is positioned so that the aftmost block (or forward block if the distributed weight is higher at the forward end) is placed over a transverse bulkhead.

4.2.2 Transverse Position

The ship should be placed with its keel over the middle line of the dock. There is sufficient margin of lifting power to balance the dock on a level keel.

For small vessels, offset docking i.e. where the ships centreline and keel blocks are positioned 4200mm from the dock centreline. Longitudinal under deck girders are provided for this purpose. Care must be taken to avoid twists developing in the dock structure as a result by the use of differential ballasting transversely in way of the vessel to minimise the torsional moments.

4.3 PUMPING AND FLOODING PLANS

4.3.1 General

The simplest and safest method of operating a Floating Dock is to ensure that at all times the total weight (dock and water and vessel) of any longitudinal section is equal to the buoyancy of that section, see Figures 11. This ensures that the longitudinal bending moment and so deflection is kept to a minimum, not only avoiding undue stresses in the dock bottom and side walls but also deflections which can affect the shape of the docking blocks. Docking blocks which do not match the shape of the vessel can lead to very high local forces in the vessel, dock blocks and dock structure in way. Particularly a sag should be avoided as this overloads the blocks at the cut-ups which are already heavily loaded from the overhanging structure at these points. The disposition of ballast water to maintain the correct condition when raising a vessel is given in Pumping and Flooding Plans.

A plan can be prepared from the weight curves of ship and dock and the hydrostatic particulars of the dock. In all cases, great care must be taken to avoid under-pumping or over-flooding the centre sections of the dock relative to the end sections, as this will cause a sag/hog to occur. Any departures from the plan are to be kept to a minimum necessary to correct small amounts of heel and trim. Large heels or trims can only develop if a vessel is docked in an incorrect condition or there are defects in the flooding or pumping arrangements. If these arise, the docking is to stop and the cause of the discrepancy ascertained. On no account in any operation of the dock is the differential head on any tank to exceed the values given in section 6.1 see also figure 6.

4.3.2 Objectives

A pumping plan is to be provided for each ship to demonstrate the following objectives:

a) Ensure that the dock has sufficient lifting capacity to lift the ship in the desired longitudinal position on the dock.

b) During the docking evolution, neither the ship nor the combined dock and ship will become unstable

c) The longitudinal bending moments are within acceptable range

d) The tank boundaries will not be overloaded due to excessive differential ballast levels



Page 10

e) The blocks are not overloaded

4.3.3 Ship Weight Distribution

The weight distribution of a vessel is required to prepare the ballast distribution in the dock. See figure 8 and 9. However, not all ships will have their weight distribution available. Where the docking displacement, LCG, and blocking length relative to the LCG are known then the procedure in Appendix 1 can be used to provide a weight curve.

Note: Where there is no reliable information, a ship may be docked subject to the vessel being of conventional form and the minimum blocking length in figure 4 is complied with. In such circumstances, a pumping plan cannot be prepared and the dockmaster will require relying on pumping the dock under the vessel with unloaded compartments being kept approximately 1.200m below the waterline.

4.3.4 Preparation of Pumping Plan

The pumping plan will show the stability and ballast levels at key stages of the docking evolution. Typically these will cover the case for the dock waterline at:

a) Deep Sink b) Ship Sued c) Ship half Draft d) Top of Blocks e) Top of Pontoon f) Working Freeboard

Note in cases where a ship with large trim sues at one end first, the stability of the ship is to be checked just prior to fully suing over the blocking length.

For each stage the amount of ballast is to be determined for each section. The amount of ballast can typically be calculated as follows:

1) From the ships weight distribution curve, calculate weight of vessel supported by each section of the dock (Refer figures # & #). Using a typical trapezoidal weight distribution as an example:

24.99m

LB

d1d2

Ws

LC

dm

= =

SHIP WEIGHT

DISTRIBUTION

dm = mean weight distribution (tonnes-metres) = d1- (d1 d2) x LC / LB Ws = weight of ship supported on section (tonnes) = dm x 24.99m

2) Correct this weight, Ws, for contribution of ships buoyancy, when the waterline is above the keel block level. If the buoyancy is unknown, then the net weight supported by a section can be approximated as follows:

WNET = Ws x T / Ts

Where: WNET = Net Weight supported by a dock section

Ws = Weight of ship supported by a dock section

Ts = Docking daft of Ship T = Draft of ship at waterline being

considered.

3) Each section (tank group) of the dock must provide sufficient lift to support the net weight over the section. The required ballast level to provide this lift will depend on the dock waterline. Using the tank group lift tables in Appendix 4, the required ballast level can be determined for the water level considered.

Using Tank Group 3 as an example:

Dock Waterline, Td = 8.20m Dock Waterline to top of blocks, h = 5.20m Ship Waterline, T = Td h = 3.00m

Ship Docking draft (mean) = 4.40m Weight of Ship Supported, Ws = 700 Tonnes Net Weight of Ship Supported = Ws x T / Ts

= 700t x 3.00m / 4.20m = 500t

From Tank Group 3 Lift Tables the ballast level for a lift of 500t at a dock waterline of 8.20m is 2.651m

In some circumstances, particularly when lifting short ships near to the docks lift capacity, the weight supported by the tank group may be greater than available. If this is the case then, the deficiency shall be added to the required lift of the adjacent tanks.

The values may require some adjustment to the end tank groups for correction of trim.

The preparation of Longitudinal strength curves (shear force and bending moments) for the condition is beyond the scope of this manual. However, by matching the lift with the weight of vessel on each tank group will minimise the bending moments. However, there may be circumstances where this is not achievable, in which case the longitudinal bending moment at midships can be approximated as follows:

A B C D = C-B E F = DxE

Tank Group

Ship Weight,

WNET

Lift provided by

TankLoading Lever M oment

tonnes tonnes tonnes metres t-m

1 100 150 -50 62.475 -3124

2 200 150 50 37.485 1874

3 300 400 -100 12.495 -1250

4 500 400 100 12.495 12505 200 150 50 37.485 1874

6 100 150 -50 62.475 -3124

Total Moment = -2499

Longitudinal Bending Moment = Total Moment / 2 = -1250

If dock cranes are fitted then the value above must be increased by weight of cranes (tonnes) x 37.485m to allow for possibility of cranes being at midships during the drydocking period.

The maximum Stillwater permissible longitudinal Bending Moment is

43,015 tonne-metres (421,830kNm)



Page 11

The methods outlined should be sufficient for most circumstances. Detailed assessments should be performed when docking vessels of unusual form or weight distribution or when the vessel is close to the limiting criteria (load distribution, longitudinal strength, stability, etc.) However, detailed assessments for example, the provision of longitudinal and transverse strength curves etc. are beyond the scope of this manual, requiring a more detailed knowledge of Naval Architecture.

4.3.5 Knuckle Load

When a vessel is docked with a trim, measures should be undertaken to minimise the trim of the vessel relative to the dock. The required trim of the dock for a trimmed vessel can be determined as follows (values in metres):

Trimdock = 149.94 x trimship / LBPship

The trim of the dock should not exceed 1.50m nor should the freeboard of the sidewall be less than 2.00m at any point.

Where the vessel has a trim relative to the dock, i.e. when the vessel trim is greater than the dock, special care is required involving:

a) The block on which the ship sues first (i.e. first touches) should be well stabilised against lateral movement.

b) The load on the block during suing is to be checked. This can be done as follows:

Block Reaction, RKN = Trim x MCT X

Where Trim = Trimship - Trimdock x MCT 149.94m

MCT = Moment to change trim from Ships hydrostatic particulars

X = distance from suing block to LCF (longitudinal centre of floatation from ships hydrostatic particulars). In the absence of the LCF it can be taken as approximately at midships for the ship.

4.3.6 Stability

Where the vessel experiences a knuckle load the stability of the ship will be reduced until the vessel has fully sued on all blocks, at which point the vessels stability becomes part of the docks stability. The reduced stability of the vessel due to a knuckle load can be determined as follows:

GMT = KMT - D x KG D RKN

Where: KMT = Transverse metacentric Height above keel for afloat vessel in docking condition.

D = Displacement of afloat vessel in docking condition.

KG = Vessels vertical centre of gravity (corrected for free surface effects) in docking condition.

RKN = Knuckle load from Block (see 4.3.5 b) above )

For positive stability, GMT must be positive. Recommended minimum allowable value for GMT is 0.15m

After the vessel fully sues, the stability is calculated for the combined dock and ship.

Trim and Stability of the ship-dock combination becomes critical when the outside water level is between the top of the keel blocks and the top of pontoon deck. At this point the ship provides little or no stabilising waterplane, the stabilising waterplane is only that provided by the sidewalls and the VCG of the ship-dock combination is almost at its highest point. The minimum transitional stability occurs during this period.

However, once the pontoon deck emerges the stability increases significantly. The minimum stability permissible during the lifting operation is 1.50 metres.

To assist in readily determining the maximum permissible vertical centre of gravity of a vessel for a given docking weight a Weight to Centre of Gravity curve has been prepared, Ref Figure 5 and section 2.4.6. This is based upon a minimum GM of 1.50 metres occurring during a docking evolution. (NB these are based on level ballasting, however, differential ballasting does not significantly affect the values typically 15mm for normal operation).

For detailed assessment of stability, refer to the vessels stability booklet Ref Doc. No. NSRY1-0-22-0001

4.4 DOCK BLOCKS AND CAPPERS

4.4.1 The Datum Plane

The Datum Plane to which the shape of docking block heights and other key dimensions are related is set to the shape of the dock when in an unloaded and unstrained condition. It should be noted that this plane will move slightly during changes of temperature and variations in the distribution of water in the ballast tanks as the dock is an elastic structure. However, the Datum Plane will recover its planarity when the dock is sunk and ready to receive a vessel if the ballast water is spread evenly throughout the dock in accordance with the Pumping and Flooding plan.

4.4.2 Arrangement of Blocks

The dock is provided with 173 standard blocks used for keel, side and bilge blocks and is illustrated in figure 14. These are composite blocks consisting of a reinforced concrete base with hardwood timber with a sandbox mounted on top which supports hardwood timber blocks and softwood capper.

Placement of blocks should be arranged to pickup both the dock structure (transverse and longitudinal bulkheads) and ship structure. For allowable arrangement of blocks see figure 15 & 16

The dimensional tolerances for the vessel's docking plan shall be the following:

a) The height of the vessel's keel and bilge side/blocks are within 5mm.

b) The distances in the longitudinal direction are within 25mm.

c) The distances of the half breadths (transverse) for side/bilge blocks are within 15mm.



Page 12

When arranging the blocks, the dock personnel shall ensure that no obstructions exist between the pontoon deck and hull openings or fittings. Also, ensuring horizontal and vertical clearance to remove and replace appendages, including but not limited to rudders, shafts, fin stabilizers, transducers, sonar domes, and retractable bow thrusters, as applicable. This clearance shall be considered whether or not removals are specified in the work package.

4.4.3 Keel (Centre Line) Blocks

The dock is designed for keel blocks spaced longitudinally at 1190mm centres. The blocks must be positioned so that they are spaced either on a transverse or 1190mm either side of a transverse in order to align with the breathing plates fitted under the deck.

650

1190

650

1190

650

1190

650

1190

650

3570

TRV TRV

The maximum allowable load on each block is 200 tonnes. Note When the keel blocks are uniformly spaced at 1190mm the keel blocks will experience a load of 119 tonnes when subject to the maximum distributed load of 100 tonne/metre.

The standard keel block height is 1.800m. Alternative block heights can be used subject to the following:

a) Block Stability Criteria are met(see Cl. 4.4.8) b) For increase in height, the maximum weight of

vessel that can be lifted may reduce depending on the vessels draft and weight to avoid exceeding hydrostatic loadings on the ballast tanks.

4.4.4 Bilge Blocks

The dock is provided with bilge blocks which are the same design as the keel blocks. They may be positioned transversely over any transverse girder as shown in Figure 15. The bilge blocks may not be placed at intermediate positions between transverse frames unless they are 4200mm off the dock centreline where the deck is supported by longitudinal girders for this purpose.

The maximum allowable load on each block is 150t when directly over a transverse or 200t at the dock centreline.

The maximum load 4200mm off the dock centreline between transverses is 47.6 tonnes per block at 1190mm spacing. I.e. 40t/m

4.4.5 Miscellaneous

When it is possible that sonar domes, rudders, tailshafts, etc., will have to be unshipped, care should be taken to ensure that the height of the blocks and clearances around the ship are adequate to permit these operations. The installation specifications for certain sonar hull outfits require the height of blocks to be increased by plinths.

When docking ships with double vertical keels, the blocks should be long enough to permit a good bearing over both keels.

Dock block stacks with different crushing potentialities should not be intermixed, i.e. Depth and type of timber should be the same throughout.

To enable intermediate blocks to be released whilst under load, all blocks are provided with both a sand box and wedged timber blocks, either of which can be used.

The soft caps shall be made of Douglas Fir or Pine, on both keel and side/bilge blocks with a thickness minimum of 50mm and a maximum of 150mm. The keel line soft caps shall not be thicker than those on the bilge blocks. Reused soft caps shall be free from any permanent deformations, i.e. crushing, cracking or other material defects.

The docking blocks shall be made of homogeneous materials. Every block in the keel line shall be fabricated of the same materials. Every block used for bilge/side support shall all be fabricated of uniform structure and materials. The bilge blocks shall not be fabricated with stiffer construction material than the keel blocks. Block material below the soft cap, shall be constructed of one of the following materials: concrete, hard wood or steel.

All blocks shall be securely dogged to prevent wood from floating out of the dock during the docking/undocking evolution

4.4.6 Dock Block Loading

The width and spacing of dock blocks and their capping pieces should ensure that mean bearing loads do not exceed values given in section 4.4.7. The maximum allowable load on the standard block base is 200 tonnes when used as a keel block on dock centreline and 150 tonne when used as a bilge block on the pontoon transverse frames.

The widths and spacings depend upon the type of ships usually accommodated in the dock. Keel Blocks are normally 1190mm apart. In regions of very heavy loading, solid blocking should be used. In the case of vessels with bar keels, in order to cause minimum damage to the blocks, the preparation of the blocks is to include the fitting of a 20mm thick M.S. plate the same length and width as the capping piece and secured by four coach screws to the top of each capping piece.

4.4.7 Timber

All timber used for the construction of blocks shall be sound structural grade timber and should not have excessive side checks or shakes.

Loadings on timber blocks:

Material Permitted Compressive Stress Proportional

Limit Perpendicular

to Grain Perpendicular

to Grain Parallel to

Grain SOFTWOOD

Douglas Fir 28 kgf/cm2 98 kgf/cm2 56 kgf/cm2 Yellow Pine 21 kgf/cm2 63 kgf/cm2 49 kgf/cm2

HARDWOOD Red & White Oak 42 kgf/cm

2 91 kgf/cm2 91 kgf/cm2

Dock block stacks should be solid, with well faying surfaces, and should not contain gaps, packing pieces or



Page 13

slivers of softwood. Softwood cappings are generally of fir, and care is to be taken that capping pieces are not split when they are secured in place.

4.4.8 Dock Block Stability

Regular inspections should be made to ensure that all dock blocks are vertical and true. Timber stacks should be constructed of blocks of the largest practical size so that the crush on the blocks is uniform and hard spots are avoided.

For block stability, the height of the block should not exceed 2 x the minimum width of the block base. The standard blocks for this dock have a base width of 900mm for a block height of 1800mm. Where this is exceeded, the stability against tripping/crippling as a pillar must be avoided by such methods as:

(1) Fully cribbed blocks throughout, i.e. alternate layers placed longitudinally.

(2) Double spur shoring between the stacks. (3) Multiple stacks, through bolted.

Note: Dagger planks fixed to the ends of blocks and the iron dogs used to connect blocks, do not provide adequate insurance against tripping.

The line of normal force for all blocking shall pass through the middle one-third of the block base as shown below:

Bilge blocks higher than 1.80m, as measured from the bottom of the block to the highest point of the soft cap, shall be tied together in pairs by means of cribbing or bracing. If the side blocks are hauled into position during the docking evolution while tied together, then they shall be hauled simultaneously.

Keel blocks higher than 1.80m shall be cribbed together in the both forward and after one third of the keel block line. The cribbing shall be a minimum of 300mm thick when used with timber blocks

4.4.9 Hull Preservation

Arrangement should be made to allow for inspection and preservation of the underwater hull, including parts obscured by dock blocks. This may be achieved by regular variation of the position of the vessel at dockings, or by systematic removal of blocks. If blocks are removed care is to be taken to provide compensating support.

5 DOCKING/UNDOCKING

5.1 DOCKING DOWN

The ship is to be brought to the dock entrance with her bow just inside the entrance and pointing along the dock centreline. Lines are attached from the ships forecastle to the berthing trolleys which will have been hauled into position at the aft end (entrance) of the dock. With the

tug(s) assisting in keeping the vessel centred, the berthing trolleys are hauled towards the forward end of the dock.

Just before the stern of the ship passes the dock entrance, after wire/ropes are passed to the stern and secured. External means of positioning the ship, e.g. tugs, are now cast off.

The berthing trollies continue to be hauled until the ship is in line with the position marks prepared for the purpose on the docksides and is finally positioned using the docks capstans or alternatively using guys and jiggers. The plumb bobs and tallied wires are rigged across the dock at the bow and stern to give a visual check on the alignment of the centreline of the ship with that of the dock.

Under certain circumstances, for example naval vessels, a diver may be in attendance. In this situation, the dock is raised until the clearance between the underside of the keel and the top of blocks is 500mm at which time raising is temporarily stopped. The diver is sent down to ensure that blocks are clear and still secure (e.g. have not tripped). Pumping is then resumed.

Divers should generally be used to check clearances when:

a) When hauling bilge blocks to verify the success of hauling operations.

b) When cradles are used for docking.

After the vessel has sued at one end, pumping should not be stopped for any reason other than an emergency until she is fully sued i.e. when the water level is seen to leave the forward suing marks indicating that the whole of the keel is resting on the blocks, and particular attention should be paid to guys and tackles during the intervening period.

If an emergency necessitates stopping the pumps during this time, the ships position should be checked before recommencing pumping to ensure that leakages have not caused the ship to float up and change her position.

After the dock has been raised 500mm after fully suing, pumping is temporarily halted whilst the vessel position is checked and that the blocks fit the vessel (when a diver is present).

Pumping is then resumed and the dock raised.

If bilge shores, bottom shores and cut-up shores are required, they shall be erected as required. The shores should be cut about 150mm short to allow for packing and wedging. Shores should be positioned at hull (dock and ship) strong points, e.g. bulkheads, frames and decks. Normally, ships rely on bilge/side blocks for stability, in which case breast shore may be dispensed with.

At this stage, responsible personnel should inspect the ship and blocks to ensure that the vessel is resting in the correct position and the blocks are secure and intact as follows:

a) Examine all blocks for total contact. Shim the blocks as necessary to provide total block contact with the vessel's hull.

b) Install any supplemental blocking or shoring for the bow and/or stern overhanging structure as specified in the ships docking plan.

c) Refloat the vessel and take corrective action if any tendency to strain or injure the vessel is observed, or if the vessel is more than 150mm off the centre of the keel blocks.



Page 14

5.2 PRECAUTIONS IN DOCK

Immediately after the ship is docked she is to be electrically "earthed" to safeguard men working on and around her. It is most important that no shifting of weight on board should take place whilst the ship is in dock as, in addition to the effect on stability, the conditions of undocking are thereby altered. If a shift of weight is absolutely necessary the change in horizontal and vertical movement should be calculated and allowed for when undocking. Drainage of water from the bilged compartment in a damaged ship should be treated as a shift of weight.

5.3 UNDOCKING

Before sinking the dock all scaffolding and loose equipment should be removed. A check should be made to ensure that all anodes are properly secured, that all valves are closed and that the indicating gear, which shows whether a valve is open or shut, is registering correctly. The rudder and propellers are to be locked in position if there is likely to be a tidal current passing through the dockwell. Bilge shores and cut up shores, if fitted are removed about an hour before flooding, except in some cases where the bilge shores are lashed to the dockside so that they can be hauled clear when the ship floats off the blocks.

In all cases, any shores under the cut up forward and aft must be removed before flooding the dock to avoid the risk of crushing the bottom plating. For instance, if the vessel when rising from the blocks trims by the stern, a considerable pressure would be exerted on the shores under the after cut up, and as this pressure would be localised over the area of the heads of the shores, crushing of the bottom plating would result.

Whilst the vessel is in dock a careful record is to be kept of all weights removed, shifted or placed aboard in order to estimate the draughts at undocking. As a result of the calculations involved, it may be found necessary to load the vessel to prevent any appreciable trim or heel that would otherwise occur on undocking.

Before undocking, the 'Undocking Certificate', prepared by dockyard personnel and checked by the dockmaster and ships master, must be signed. This states that:

(a) All openings in the ship's bottom are shut, and any valves worked on by ship's staff are in good order.

(b) All details of any weights added, removed or moved in the ship since entering dock have been listed on the certificate.

5.4 CORRECTION OF LIST AND TRIM IN THE SHIP

When docking a ship of normal form on middle line blocks only, care must be taken to see that the ship is upright, as if docking in a graving dock. When docking a ship on three or more lines of blocks, provided that the angle of the heel does not exceed 3 degrees, it is not so important to take measures to upright the ship, as the dock may be laid over to suit.

Great care must be taken, however, that the ship is well centred on the blocks, proper allowance having been made for the heel; also that the dock has been heeled over to exactly the same angle as the ship. It is most important that the ship is upright when the dock is levelled up.(See figure 12).

If the trim is not more than 1% of the ship length (ie1.5m over the length of the dock), it is unnecessary to bring the ship to a level keel; the dock can be trimmed to suit providing the freeboard of the sidewall top deck is nowhere less than 2.00m. Precautions must be taken to see that all loose gear has been properly secured. In pumping up, no attempt should be made to level up the dock until the ship touches the blocks all along.(See figure 13)

When using plumb-bobs for positioning the vessel, ensure that effect of trim angle on the plumb-bob indicating the fore and aft position of the vessel has been allowed for.

6 DOCK OPERATION

6.1 PRECAUTIONS

The dock is designed for longitudinal differential ballasting to control longitudinal bending moments, trim and heel. For each transverse group of tanks the ballast should be kept approximately level i.e. transverse differential ballasting is not required to control transverse bending moments. In the case of offset and if operated normally will lift any vessel up to the limits of the docks capacity - without the differential pressure heads exceeding the following limits:

Maximum Permissible Differential Pressure Heads

Height of Dock Waterline wrt Ballast Level 6.7m Ballast Levels Between Adjacent Tanks 4.3m

See also Figure 6 for more details

The dock should never be sunk with a dry ballast compartment, as the differential heads will exceed the maximum permissible. All manhole covers in the pontoon deck are to be properly bolted down in place.

The cranes, if and when fitted, are to be at their hold down locations, jibs facing fore and aft and secured by clips. Cranes are not to be unclipped and moved whilst the dock is being pumped or flooded.

Electric power and air are to be available to the dewatering pumps, valves and valve control table. All valves, valve operating gear and depth indicators are to be checked as in an operable condition and valve positions set and recorded for the operation.

Isolating (Separation valves) valves in the dewatering system are to be SHUT unless a defect to an inlet valve occurs. In this case tanks can be flooded or pumped from an adjacent section by opening the appropriate isolating valve. Care is to be taken that, when an isolating valve is open, siphoning or levelling between tanks does not occur. Control is to be maintained by use of the tank valves, and not more than one pair of sections, made common by the open isolating valves.

The stability, both longitudinal and transverse, is at a minimum during the period between when the blocks and the pontoon deck become awash. During this part of the lift or sink, particular care must be taken to keep the dock on an even keel.

All four dewatering pumps should be available together with the necessary electrical supplies.



Page 15

6.2 PREPARATION

Prior to sinking the dock, the following prechecks should be made:

a) Check functionality of all compartment valves by cycling once. Any sticky valves to be attended to. (To be carried out with main inlet, discharge and isolating valves closed).

b) Check functionality of inlet and discharge valves by cycling once.

c) Run pumps for 5 minutes by opening both inlet and discharge valves. All four dewatering pumps should be available together with the necessary electrical supplies.

d) Check functionality of isolation valves by opening and closing once.

e) Check all pontoon deck manholes are closed

f) Check Contaminated Water Tank valves are closed and that the drain covers (under the pontoon deck grilles over the troughs) are closed.

g) Check all gauges and indicators relating to the dewatering system in the control house are functional.

h) Check that battery backup for valve control and actuators are fully charged.

i) Sounding pipe caps are closed.

j) Compressed Air System from shore supply is not less than 10 Bar (NB this will lower during operation of valves)

k) Watertight doors in Safety Deck are closed.

l) Check all winches and capstans are functional

Opening and closing valves to check functionality shall be sequenced to ensure no change to the ballast levels. For example, two compartments valves from the same main drain (manifold) are not open at the same time, to prevent transfer of ballast from one to the other.

Ensure that all material within the dockwell is secured against floatation, where applicable. This includes block timbers etc. The pontoon deck should be clear of all contaminants/pollutants.

6.3 DOCKING

6.3.1 General

Prior to sinking ensure that:

a) Docking plan has been prepared b) Docking Blocks have been checked and are

properly levelled to sit the vessel. c) Dock Checks have been carried out in

accordance with clause 6.2 d) All personnel are clear of the pontoon deck e) 24hour weather window forecasts wind speeds

not greater than 20mph.

Docking should not be undertaken if any valve or pump is not functioning correctly.

6.3.2 Sinking

Tanks are flooded through the inlet valves, dewatering main and compartment valves. To sink, open the inlet valves. Regulate by means of the compartment valves. To reduce the sink rate, throttle the inlet valves.

The main drain isolating valves are to be kept closed throughout the sinking operation. Tanks are to be flooded uniformly except insofar as adjustments are required to correct departures from level heel and trim. This procedure will ensure that the planarity of the pontoon deck is maintained and the longitudinal bending moments on the dock are kept to a minimum.

As deep sink is approached care is to be taken that the freeboard is never less than 2000mm corresponding to a draught of 8.80m over the pontoon deck, indicated by a white line on the inner walls at each end and midships. As a precaution the optical sight should be monitored at intervals of not more than 10 minutes; if the reading changes by more than 15mm from that recorded at the start of the operation, the sinking is to be stopped and the disposition of ballast water checked. Sinking is not to recommence until the cause of the anomaly has been cleared. Should, in an emergency, it be necessary to sink the dock with a defective tank which precludes its correct flooding or subsequent pumping, this is permitted providing only one tank in the dock is so affected and that during the subsequent operations the differential head on the tank does not exceed the values specified in Section 6.1.

port Quayside

ster

n 21 17 13 9 5 1

bow

22 18 14 10 6 2 23 19 15 11 7 3 24 20 16 12 8 4

starbord

During sinking of the dock the following effects can be controlled by regulating the compartment valves:-

Stern Trim: Close Compartments 21,22,23, and 24 until dock is level.(i.e. aftermost compartments)

Bow Trim: Close Compartments 1,2,3 and 4 until dock level.(i.e. forwardmost compartments)

Heel to Port: Close one or two side Compartments on Port side until dock is level.

Heel to Stbd:

Close one or two side compartments on Starboard side until dock is level.

Hog: Close Compartments at the ends of the dock until zero deflection.

Sag: Close Compartments over the mid body of the dock until zero deflection.

Unless there are very special reasons, trims exceeding 1.5m in the overall length of the dock should be avoided. Large trims may cause problems with dock sensors, outfit and access.

Always close the compartment valves and inlet valves immediately after sinking. In case of emergency during sinking, at once close all valves.

Should it be necessary to keep the dock lowered for a long time, the pumps are to be kept in readiness so that water may be pumped out should the dock be damaged by collision whilst in this condition. Regular checks of the dock draughts should be made to ensure no leakage is occurring.



Page 16

6.3.3 Deep Sink

The maximum depth to which the dock can be sunk is controlled by an air cushion in the sidewall tanks. The size of the air cushion, Y, is set by the extent, X, the ballast tank air vents protrude into the tanks and is pre-set from the commissioning trials. Therefore with all valves open it should not be possible to sink the dock below the maximum deep sink waterline.

If the weight or horizontal centre of gravity of the dock lightship is changed, for example by the provision of additional blocks, the air vents will require readjustment.

As a precaution, when the dock reaches deep sink, or the intended dock draft for the docking operation, all valves should be closed.

There are no tidal restrictions for the deep sink draft.

Whilst at deep sink, the dock drafts should be monitored for change. If changes occur, the cause shall be cleared, failing which, the dock shall be raised. On no account must the dock waterline exceed the deep sink waterline at any position along the sidewalls.

6.3.4 Pumping Out the Dock

Tanks are pumped using the 4 dewatering pumps through the main discharge valve and the compartment valves. When ready to pump, the main Discharge valves are opened and the pumps started. The pumping rate can be controlled by throttling the main discharge valve. Regulate using the compartment valves.

During pumping, the main inlet valve and isolating valve shall remain shut.

When stopping at intermediate levels, for example when undertaking block inspection by diver, the compartment valves shall be shut, although it is unnecessary to close the main discharge valve. If the stoppage is of short duration (less than 5 minutes the pumps may be kept running) whilst for longer periods the pumps shall be temporarily stopped.

(a) At all times whilst pumping, the differential pressure head on any tank is never to be allowed to exceed values in Section 6.1.

(b) Up to the time the ship sues, the dock should be pumped uniformly by pumping on all tanks. Trim and heel can be controlled as necessary by regulation of the compartment valves.

(c) Pumping should be slowed whilst the ship touches down and any initial trim is corrected by throttling the main discharge valve. Pumping should be temporarily

halted after the vessel has sued 500mm to check the blocking with the vessel correctly positioned. To ensure that the longitudinal bending moments and deflections are kept to a minimum, ballast water removed from the tanks should be appropriate to the weight distributions of the vessel and dock. The final disposition of ballast water is given in the Pumping Plan for the particular vessel. At all times tanks beyond the bearing length of the keel of the vessel should be pumped only to the levels necessary to support the weight of the dock and correct trim.

(d) Particular care is to be taken to avoid lagging in the removal of water from the tanks near midships as this will cause a sag to develop in the dock.

(e) As a precaution the optical sight should be monitored at intervals of not more than 10 minutes; if the readings change by more than 15mm from that recorded at the start of the operation, the pumping is to be stopped and the disposition of ballast water checked. Pumping is not to recommence until the cause of the anomaly has been cleared.

(f) Loss of dewatering pump suction can be expected to occur when the depth of the water in the ballast tanks approaches 300mm. To reduce this tendency, the pumping rate is to be slowed down (by throttling the discharge valve) as this depth is approached, i.e. at about 600mm. Should a pump loose suction at this depth it is to be shut down together with the relevant tank valves. If it is essential to recommence pumping with the dewatering pumps the main should then be refilled from an adjacent transverse tank or from sea by opening the inlet valve of the section. When the dewatering main is full, the system valves are to be reset for pumping and the pumping rate kept low by throttling the discharge valve..

(g) If a pump breaks down, an adjacent pump can be used by opening the appropriate isolating (Separation) valve on the dewatering main. This should be done with care. The tanks are to be isolated by appropriately setting the tank valves to avoid siphoning between them, only one transverse pair of tanks being pumped at a time.

(h) Always close the screw-down discharge valves and compartment valves immediately after pumping up.

6.3.5 General Considerations

From ammeter readings during pumping, determine that each pump is doing its work. Watch the deflection indication, and adjust the valves so that the deflection is reduced to a minimum.

When the dock is submerged, the internal water will not only fill the pontoon compartments, but will stand up in the sidewalls. When the dock is raised and carrying the ship, the proper distribution of internal water is such that as much water as possible has been removed from the compartments immediately below the central bearing length, and the remainder of the ballast water has been left in the end compartments. To effect this, in the first stages of the pumping, all the compartment valves should be opened. When the internal water has levelled up across the dock at the level of the pontoon deck, continue to pump all the compartments directly beneath the bearing length right across the dock, but only take enough water from the compartment at each end to:

(a) support the weight of the dock itself. (b) obtain longitudinal balance.



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A difference of about 1200mm between the inside and the outside water lines of the end compartments is required to support the weight of the dock.

Longitudinal balance can be obtained by regulating compartments 1, 2, 3, 4, 29, 30, 31, 32; transverse balance by shutting one or two wall compartments as may be required; otherwise the water can be kept level across the dock.

Throughout the operation of pumping, the isolation valves in the main pump line are to be kept shut and each section of the dock pumped by its own pump.

When, during the lift of a short ship, the desired height of water is reached in the end compartments, the valves of these compartments must be closed, and pumping continued from the compartments under the keel of the ship. Towards the end of the lift, it may be necessary to take more water from the end compartments.

In pumping up the dock when trimmed to suit the ship, keep the isolating valves closed and open up all the compartments. Pump slowly until the ship touches the keel-blocks all along, and then so regulate the pumping as to bring the dock on an even keel. When the dock levels up, the lift follows its normal course.

In no case must more water be taken from the end compartments than is necessary to satisfy the conditions in this paragraph under (a) and (b) above.

During the pumping operation the dock is to be kept as free as possible from longitudinal deflection. Any deflection observed is to be corrected by appropriate pumping. The dock must be brought level as soon as possible after the ship is fully in contact with the blocks, and this level condition is to be maintained during the remainder of the operation.

Particular care is to be taken to avoid a sag in the dock, as sagging causes a large increase of block pressure towards the ends of the ship, particularly at the after cut up, which can cause damaging stresses in the adjoining structure.

6.4 RAISED

Should access to pontoon tanks be required when the dock is raised and carrying a ship, not more than 2 pontoon deck manholes should be open at any one time in the dockwell. If pontoon deck manholes are open then the Dockmaster should ensure that there is sufficient freeboard that in the event of compartment damage flooding through the open manhole will not occur. When the dock is not carrying a ship and has considerable freeboard no restrictions are applicable on the number of manholes permitted to be open.

When the dock is raised a daily log of the dock condition giving draughts and tank depth readings should be kept. If either draughts or tank gauges are found steadily increasing, i.e. indicating leakage, then the cause is to be ascertained and remedied.

If shores are fitted, they are to be "hardened up" each day, particularly the day after docking in hot, dry climates.

When it is desired to rotate the shafting and propellers whilst the ship is on the blocks, the personnel responsible should first verify that this can be done safely.

6.5 UNDOCKING

6.5.1 Preparation

Preparations as directed in section 6.3 are to be taken. In addition, a careful check is to be maintained during the docking period on the condition of the vessel and any changes of weight and position of items. No changes are to be permitted which would prejudice the lifting capacity of the dock or the strength of the dock blocks without the prior approval of the operators technical department. Changes within the capacity of the dock can be permitted at the discretion of the Dockmaster. Should changes have occurred which result in a shift of the longitudinal centre of gravity of the ship, a change of trim of the dock will have occurred. This will be magnified when the pontoon deck of the Dock is submerged. This trim can be corrected by appropriate redistribution of ballast water in the dock tanks under the vessel to obtain a level trim on the dock before sinking. The dock is then sunk in the normal way. In case of doubt the dock should be sunk until the pontoon deck is about to go under and then taken through this phase slowly using the tanks under the ends of the vessel to retain control over the trim. When the ship is within 300mm of the light draught, the dock can be allowed to take on the original trim to avoid excess pressure on the blocks at the Forward or Aft cut-up.

6.5.2 Sinking

Prior to sinking the dock, the pre-checks given in section 6.2 shall be carried out.

As during the docking process great care must be taken to reduce longitudinal and transverse stresses. Tanks should therefore be flooded in the same sequence as they were pumped, keeping end tanks for balance of dock weight. These will, therefore, not be opened up until the later stages of the sinking and it should be noted that at the start of the operation the water levels in them will be higher than that in the tanks under the vessel, thus indiscriminate opening up would lead to rapid siphoning and high stresses. Pumps are always to be kept in readiness to correct any abnormal condition.

When undocking short ships, where most of the water from the pontoon has been taken from the compartments immediately beneath the ship, a considerable difference in the height of internal water may exist between the middle and end compartments. In such cases, only the valves of the compartments under the ship should be opened at the beginning of the sinking until the water in the pontoon begins to level up, then all valves may be opened and the sinking may proceed normally.

If material alterations have been made to the ship while in dock, likely to alter her trim when afloat, sink with only one of the two inlets valves per section open until a significant portion of the vessels weight is being supported by its own buoyancy, the remainder still being on the blocks.

Throughout the sinking, the dock must be kept as free as possible from longitudinal deflection and the admission of water must be regulated accordingly. Any deflection observed must be corrected immediately by appropriate flooding or pumping. Pumps are to be kept ready for immediate use if required to assist in correcting any abnormal condition caused by temporary loss of control, damage etc.



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7 SPECIAL PRECAUTIONS

7.1 DOCKING OF DAMAGED VESSELS

7.1.1 Position In The Dock

When docking a damaged vessel which has compartments open to the sea allowance must be made, in the calculation for the longitudinal position of the centre of gravity of the vessel, for the fact that the bilged compartments will empty themselves when the vessel is lifted. The ship should therefore be regarded as having the displacement, trim and heel that existed before the compartments were bilged.

7.1.2 Vessels With Heel Or Trim

When sinking the dock to receive a damaged vessel having a heel or trim, the dock may be inclined to some extent to suit the inclination of the vessel, see section 5.4 herein. For ships to be docked on middle line blocks only, requiring fairly long shores, listing of the dock must not be undertaken. The ship must be brought upright before docking down.

7.1.3 Vessels Seriously Damaged

If a ship proposed for docking is so seriously damaged that attempted docking would prejudice the safety of the dock, the operation is not be undertaken.

The guiding principle is always not to take such a risk with a badly damaged ship as to jeopardise the use of the dock for other ships. The operators technical department must decide this.

Ships which are so seriously damaged that their longitudinal strength is considerably reduced at any transverse section should not be completely docked down without detailed technical appraisal. The dock should be pumped out sufficiently to take the weight of the ship on the blocks and prevent any movement of the ship by the tide. A report should be made to the appropriate technical department of the extent of damage and docking should not be completed until instructions are received. If the circumstances do not permit this action, the responsible personnel should satisfy themselves that completely raising the dock will not endanger the ship or dock. Care must be taken when pumping up the dock to allow any compensating water on the undamaged side of the ship to escape as the dock rises, otherwise the permissible displacement of ship for block length may be exceeded.

7.1.4 Vessels With Damaged Bottom Plating

Prior to the ship being brought into the dock, the position of the damage is to be ascertained by a diver, and the dock blocks removed in the vicinity. When the ship is in position in the dock a diver is to be sent down again to examine the bottom to see that all jagged or loose plating is clear of the blocks. It may be necessary to cut away some of the damaged structure if this is liable to touch the bottom of the dock or the top of the blocks.

7.2 DOCKING SHIPS WITH CONSIDERABLE TRIM

For a vessel with considerable trim the period between initial and full suing is very dangerous, as the stability of the ship decreases and the pressure on the "suing" blocks increases as the water level falls. The effect on the stability

may be so great as to cause the vessel to list, and on the blocks as to cause them to crush. As a safeguard against these eventualities, the following precautions should be taken:

(1) The trim of the ship should be reduced as much as is practical, and if possible the ship should be docked so that her trim is assisted by the trim of the dock.

(2) Side scuttles and other openings in the ship's side are to be kept closed during docking and undocking.

(3) The ship should be ballasted as necessary to ensure adequate stability and care should be taken to reduce the free surface of liquids in oil and water tanks to a practical minimum.

(4) The blocks in the vicinity of the "suing" position should be reinforced and well spur-shored or cribbed.

(5) As soon as the keel touches the blocks, one "pinning" shore on each side as near as possible to the "suing" position is to be set up "hand-tight", and kept so until the ship sues all along, when all the breast shore

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