Engineering Training

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ASSIGNMENT SHEET

Assignment Sheet Number 62B-402

INTRODUCTION

LESSON TOPIC LEARNING OBJECTIVES

Terminal Objective:

Enabling Objective:

11.35 UNASSIGNED; reserved for future use.

11.36 UNASSIGNED; reserved for future use.

11.37 UNASSIGNED; reserved for future use.

STUDY ASSIGNMENT

1. Read Information Sheet 62B-402
1. Outline Information Sheet 62B-402 using the enabling objectives for lesson 62B-402 as a guide.
1. Answer study questions and study scenarios.

STUDY QUESTIONS

1. How long does it take to raise and lower the stern gate?

 

1. By what emergency means of operation can the stern gate be lowered?

 

1. What is the purpose of a vehicle turntable?

 

1. What is/are the emergency operation means for the vehicle turntable?

 

1. What are the methods of raising and lowering the water barrier?

 

1. Explain (in detail) the sequence of operation of firemain filled and seawater filled ballast tanks during ballasting and deballasting operations. Be sure to include all components involved and their respective modes of operation.

STUDY SCENARIO

How does the complete loss of power affect auxiliary equipment that supports ops?

1. Stern Gate and Water Barriers

 

1. Turntables and Well Deck Ventilation

 

1. Ballasting/Deballasting

INFORMATION SHEET

Information Sheet Number 62B-402

INTRODUCTION

REFERENCES

INFORMATION

1. Stern Gate

1. Structure

1. The stern gate consists of a paneled, steel structure extending vertically from the well deck to the main deck and transversely from well bulkhead to well bulkhead. Figure 1 depicts the location at the end of the ship.
2. The gate is hinged at its lower edge at the well deck level and swings down and aft 20 degrees below the horizontal plane.
3. In the down position it rests on a transverse support bracket which is welded below the well deck level on the transom.
4. Hardware fittings are provided for pulling the gate against the gaskets on the hull to make watertight joints. The fittings consist of dog bolt assemblies that engage slotted retainers in the stern gate.
5. Clearance is provided around the hinge pins to allow the gate to be pulled tight against the gaskets and prevent binding at the hinges.

2. Operating capabilities

1. The stern gate is designed to meet the following capabilities:

1. Raise and lower the gate in three minutes or less (using both hydraulic rams).
2. Raise and lower the gate using either ram (no time limit is established for this operation).
3. Provide positive control of the gate during travel.
4. Hold the gate in all operating positions and resist sea forces in both directions of gate travel.

2. Additional requirements

1. With the gate resting on a dock and off the outboard support, it is capable of supporting the load of one M-60 tank, or two M-55 five-ton cargo trucks.
2. The stern gate is capable of operation in a Condition 3 sea state with the ship underway at three knots. Underway operations for Landing Craft Air Cushion (LCAC) vehicles require the stern gate to be fully lowered with the ship heading into the seas at 10 knots.
3. With the gate lowered to a horizontal position level with the well deck and with one foot of water at the well deck sill (transom), the gate is capable of supporting loads imposed by launching two Landing Vehicle, Tracked, Personnel Carriers (LVTP) simultaneously.



Stern Gate- Figure 1

3. Stern gate operation

1. The stern gate is normally operated by two hydraulic cylinders attached (by links) to the gate. The cylinders are moved by hydraulic pressure supplied from an electro-hydraulic power unit through two electric, motor-driven pumps.
2. Each pump, combined with either cylinder, is capable of providing sufficient pressure to raise and lower the gate.
3. The electro-hydraulic power unit is installed in the Stern Gate Operating Gear Room, along with two manually operated hydraulic standby pumps.
4. The hydraulic cylinders are located in the Stern Gate Operating Rooms. Figure 2 illustrates a basic stern gate machinery space.
5. Hydraulic docking valves are provided in the system to permit direct passage of hydraulic fluid between ends of each cylinder. The docking valves are provided with limit switches which energize indicating lights when the valves are open (The docking valves permit the stern gate to "float"). These valves are also used when the stern gate is raised or lowered under emergency conditions by the port and starboard warping capstans.

4. Emergency operation

1. Standby hand pump operation

1. Two back-to-back hand pumps are installed in the Stern Gate Operating Gear Room No. 2 to operate the stern gate if the hydraulic power unit fails or electrical power is lost. This arrangement permits simultaneous or individual use of the hand pumps.
2. Interlocks are provided as required to prevent starting of the electric motor during manual pump operation, or vice versa.



Stern Gate Machinery Room- Figure 2

2. Air motor operation - An auxiliary air motor, driven by the ship’s service air system (with an adapter for attaching to the hand crank of each hand pump) is provided. When not in use, the air motor, with its air hoses, adapter, and control valves, is stowed in the Stern Gate Operating Gear Room No. 2.
3. Raising and lowering by capstans- In the event of a hydraulic power failure (electric or manual) or an air motor failure, the stern gate may be raised or lowered using the port and starboard warping capstans rigged with wire rope.

5. Stern gate controls

1. Local controls for the stern gate are located in the Stern Gate Operating Gear Room No. 2. The stern gate hydraulic power unit has two motors, each driving a hydraulic pump. Each motor has a separate controller.
2. Each controller has START, STOP, and EMERGENCY RUN push buttons.
3. Located next to the controllers are a control station which permits selection of one of the two motors to RAISE and LOWER the stern gate with hydraulic power.
4. Remote controls for the stern gate are located at the stern gate control and the Well Deck Officer Control Station on the main deck, port side. This station has control panels with hoist and lower push buttons, indicator lights for motors and docking valves, and a horn control station. An audible alarm sounds when stern gate opens and closes.

2. Vehicle Turntable

1. Turntable structure - The turntable is a radially framed structure that revolves in a circular watertight recess so that the table plating is flush with the deck. The center of the table is supported by a rotating trunion shaft mounted on roller bearings (see Figure 3).
2. Turntable Support - Around the edge of each turntable are twenty equally spaced rollers. Each roller is secured to the ship and rolls on a track along the bottom of the turntable. Located at the edge of each table are ten stops to prevent the turntable from jumping out of its recess during vertical shock. Two wedges are set in the deck at the edge of the turntable (port and starboard) to positively prevent the tables from rotating when secured. Sixteen vehicle securing fittings are located in the plating of each turntable for use only when shock requirements need not be met.
3. Drive train and power unit - Mechanical clutches and an electric disk brake govern the operation of this motor arranged through a vertical drive shaft and sprocket assembly. When the turntable is loaded with one five-ton truck the output speed is one foot per second, or one revolution in 2 minutes. One clutch is normally used for motor operation. A second clutch can be utilized when operating in an emergency condition. Both clutches are manually controlled through a gearbox at the turntable level.
4. Emergency air and hand drive mechanism - The turntable can be operated by an air-powered tool driving a separate vertical shaft through the turntable sprocket. The second clutch is used for the alternate air tool drive operation. The first clutch is disengaged when the second clutch is engaged to prevent the motor shafting from driving the air tool-driven shafting. An alternate method is also provided by using a hand crank.
5. Electrical controls - There are two control stations located on the 01 level walkway that control turntable rotation in clockwise and counterclockwise direction. An automatic alarm will sound five seconds before the turntable starts rotation when the controls are energized (the alarm does not sound when manual operation is used). Electrical interlocks are provided to prevent the motor from starting when the hand crank is used. An audible alarm sounds when the turntable rotates.



Vehicle Turntable- Figure 3

6. Turntable leveling - The turntable trunion bearing housing and all twenty roller foundations (per table) are mounted on mild steel shims. All of these shims have been tack-welded into place and machined at installation to insure that the turntable is level.
7. Drive Train Alignment - Since a perfect match between the turntable circumference and the length of the main roller chain is unlikely, shims are also required between the chain and the table. Other shims ensure proper drive sprocket engagement with the main roller chain, proper alignment of motor and speed reducer, and correct height of the entire drive unit.
8. Operating safety precautions - To ensure safe and smooth operation of the turntables, the following safety precautions and operating procedures must be followed at all times.

1. The turntable should never be operated when accesses are open or other signs exist that personnel are within the turntable recess or machinery pit.
2. The turntable should never be operated with electric power when the explosion proof covers of the electric motor, brake, magnetic controller, master switch, bell, or indicator switch have been damaged or removed.
3. The turntable should never be turned, even by hand, when the explosion-proof covers of the motor or brake have been removed.
4. Due to increased explosion hazard, the turntable should never be operated when automotive gasoline has been spilled in the vicinity of the table or an abnormal amount of gasoline vapor is present.
5. Before and during operation of the turntable, the operator should continually check that no damage will be done to personnel or equipment by interference with gun barrels or other projecting objects located on the vehicle being turned.

9. Operation

1. Normal operation

1. Ensure power is available to the turntable
2. Ensure automatic brake is engaged
3. Ensure emergency clutch is disengaged
4. Remove locking wedges from the edge of the turntable
5. Center vehicle on turntable and depress either the CLOCKWISE or COUNTER-CLOCKWISE buttons
6. Jogging (small adjustments) can be made by momentarily depressing the JOG button from either the CLOCKWISE or COUNTER-CLOCKWISE control panel.

2. Emergency operation

1. Use of the EMERGENCY RUN button bypasses motor overload protection and may result in permanent damage to the system. Use this feature only when safety of personnel is at stake.
2. Tripping of the overload relays is an indication that a malfunction has occurred in the turntable system and the motor is overheating.
3. Depress EMERGENCY RUN and either the CLOCKWISE or COUNTER-CLOCKWISE buttons simultaneously to operate the turntable in an emergency condition.

3. Vehicle Stowage Well Ventilation

1. During vehicle stowage well operations, large quantities of smoke and fumes, including highly toxic carbon monoxide, will be generated. During fueling operations, spillage of fuel will result in highly flammable fumes.
2. The fuel vapor removal system should be operated at all times when vehicles are in the stowage well.
3. The main reason for ventilating the vehicle stowage well is the dilution of carbon monoxide produced by combustion engines. The following is a guide for personnel safe exposure times versus the number of vehicles (LCACs are not included in this chart):

4. The carbon monoxide concentration will vary from a minimum at natural supply openings to a maximum in the vicinity of the exhaust system openings. Personnel should avoid prolonged activity in the high concentration areas when vehicles are operating.
5. Since carbon monoxide is a colorless, odorless gas, its presence cannot be detected by the senses. The first signs of overexposure to carbon monoxide are dizziness, headaches, or shortness of breath during exertion. Personnel experiencing these symptoms should immediately exit the area. Safety observers must constantly check personnel to ascertain their alertness and ability to perform.

3. Well Deck Ventilation

1. The opening in the boat deck and the exposed wing-walls allow for natural ventilation of the well deck. The LCAC ventilation fans assist in moving a rapid amount of air through the well deck.
2. LCAC operations expose the well deck area and walkways to extremely high temperatures and harmful exhaust gases. During LCAC operations, all hatches and passageways exiting the well deck are to be closed.

4. Portable Vehicle Ramps

1. A portable vehicle ramp (53 feet long and 10 feet wide) is installed to provide a vehicular passageway between the well deck and the sloping vehicular passageway leading from the turntable area.
2. A fixed ramp is installed between the 01 level and the turntable area and allows vehicles to travel from the boat deck to the well deck via the turntable.
3. The lower end of the portable vehicle ramp is restrained from athwartships movement by guide pins which are mounted on the ramp. These pins can be extended downward into slotted inserts in the deck.
4. To prevent upward movement of the ramp, adjustable vehicle lashing tie-downs are provided.
5. The upper end of the ramp is restrained by pins and supporting brackets.
6. The underside of the ramp is fitted with rubber wheels for sliding purposes when it is being stowed.
7. The portable ramp is normally handled by the bridge crane and a forklift truck with a tow bar.

5. Well Deck Water Barrier

1. The water barrier is a hinged, watertight closure that (when up and dogged) limits well deck flooding to the aft part of the well deck.
2. The forward compartment that is created by the water barrier is kept free of seawater and can be used for the stowage/maintenance of land vehicles or landing craft. At the same time, the aft compartment can be used in a flooded condition for wet well operations.
3. The water barrier is a steel structure installed so that it normally lies flush with the well deck planking surface. It is covered with planking in the same manner as the surrounding well deck.
4. The gate hinges are installed in the forward transverse section of the structure. When raised, the gate lifts toward the vertical in a forward direction.
5. A molded gasket is fitted on the forward portion of the deck recess edge and also vertically on the wingwalls. It provides a watertight seal between the forward and aft compartments when the gate is in the raised position.
6. Hinged sections of the port and starboard wing-wall batter-boards must be raised to allow the water barrier to be lifted. The hinged sections are lowered and secured after the barrier is raised into position.
7. Barrier Operation

1. Two methods of handling the water barrier are available. The primary method is either by the port or starboard crane on the 01 level. The secondary method is by utilizing the bridge crane.
2. Prior to rigging topside crane, the bridge crane is positioned over the water barrier gate and the hinged batter-boards are lifted to clear the water barrier’s arc of movement. The water barrier is then rigged to be raised or lowered by the port or starboard crane on the 01 level.
3. To raise or lower the water barrier by the bridge crane, the batter-boards are raised by the bridge crane and secured from the overhead padeyes. The water barrier is then rigged to be raised or lowered by the bridge crane.

6. Ballasting and Deballasting.

1. Description - The ballast system is comprised of a series of dedicated ballast tanks both above and below the ships water line, a ballast tank valve control system, ballast control console (BCC), deballast air system, and a communications system. The quantity of ballast is controlled by filling or emptying the ballast tanks, as necessary, from the BCC located in the ballast control room (See Figure 4). Tank level indicators (TLI) and sounding tubes are installed to allow remote and direct monitoring of tank levels.



Ballast Control Console - Figure 4

1. Ballast tanks above the water line. The upper set of ballast tanks consists of various sized wing tanks located below the first deck but above the normal water line (second, third or fourth decks dependent on ship class) along the port and starboard sides of the well deck. This group of tanks is filled from the firemain system through hydraulically operated fill valves and emptied by gravity through hydraulically operated drain valves. All tanks can be filled or drained either individually or simultaneously as desired from the BCC.



Ballast tank (below water line) - Figure 5

2. Ballast tanks below the water line. The majority of the ship’s ballasting capability is contained in the series of ballast tanks located below the ships normal water line (fifth, sixth or seventh deck dependent on ship class). Figure 5 illustrates general tank location. This series of ballast tanks consist of various sized structural tanks running most of the ship’s length. This group of tanks are filled from the sea by opening the hydraulically operated sea valves located in the bottom of the tanks and the electrically operated tank vent valves located on the second deck. Tanks are emptied by forcing the seawater out of the tank through the same sea valves with air pressure from the air deballast system with the tank vent valves closed. These tanks are equipped with electrically operated vent and blow valves to allow the tanks to be vented when filling and to admit low pressure air to the tanks when emptying. All tanks can be filled or emptied either individually or simultaneously as desired from the BCC.
3. Ballast tank valve hydraulic control system. The ballast tank valve hydraulic control system is arranged for operation of the hydraulically operated valves remotely from the BCC (primary) and remote manually from each hydraulic station (secondary). This system is divided into a series of hydraulic control stations, the number of which is dependent upon the quantity of ballast tanks and the size of the hydraulic control stations. Each station consists of a motor driven hydraulic pump to supply hydraulic pressure to a group of hydraulically operated valves. The hydraulic control stations control the firemain fill, drain, and sea valves for their assigned tanks. To allow for system flexibility (during emergency operation on some classes of ships) the control stations can be cross connected to allow any station to provide hydraulic power to operate the hydraulic valves of any other station.

1. The ballast control console (BCC) is located in the ballast control room, and remotely controls ballasting/deballasting operations by controlling and monitoring the hydraulic control stations, air deballast system, tank levels, well depth, and ship draft. Normally, the ballast control room is manned by the Damage Control Assistant (DCA), one or two operators and a phone talker. The controls and monitoring indicators necessary for remote operation consist of push buttons, TLIs, and lighted indicators labeled for their specific functions.
2. Air deballast system. A typical air blow deballast system consists of an air main loop from which branch lines supply air to ballast tank and remote operated blow valves. Cross connection and isolating valves are provided in the loop main to enhance reliability of the system.

1. The air main is supplied by several rotary-type air compressors (often referred to as ROOTS blowers) to ensure reliability of the air supply. These compressors are designed to supply a large volume of air at low pressure. Compressor unit capacities for deballast applications vary from 1,400 to 2,200 cubic feet per minute (CFM) and are set for a normal discharge pressure of 12 to 22 psig depending on the type of ship. Compare this to the output of a typical low pressure air compressor of 100 CFM at 125 psig. Intake air is supplied to the compressors by an air inlet filter and silencer designed to minimize the possibility of water entrainment.
2. Each compressor is provided, in the following order, with a discharge silencer, a diverter valve leading alternatively to a blow-off line fitted with muffler or to the air main, and a check valve and isolation valve upstream of the connection to the air main. A relief valve and appropriate local and remote-reading instrumentation are provided. The diverter valve and blow-off line permits starting the compressor without load. A hydraulically operated unloading valve is also provided for each deballasting compressor on LHA and LHD class ships.
3. Upon starting each compressor under a no-load condition, air is discharged to the atmosphere through the compressor unloader valve. A time delay relay in the compressor control circuit inhibits closure control of the unloader valve until the compressor attains normal speed. Earlier ships such as LSD 36 through LSD 40 and LPD 4 through LPD 15 were not provided with unloading valves for the deballasting compressors. However, it should be noted that when deballasting, compressors start under unloaded or light load conditions, since the 10-inch deballast mains are depressurized and initial pressure required for deballasting is low (approximately 5 PSI). The isolation valve permits deballasting with as few compressors as required. Generally, the controls provide for local starting and local or remote shutdown of the compressors.
4. At each ballast tank fitted for air blow deballasting, compressed air is supplied by way of a motor-operated air blow valve. A motor-operated tank vent valve discharging to a vent line is provided. The vent and air blow valves are usually interlocked mechanically, acting as a unit so that the vent valve is closed when the air blow valve is open and vice-versa.

2. Well Deck Drainage There must be a means of efficiently flooding and draining the well deck when conducting ballasting operations. The well deck drain system consisting of drain wells, piping, valves, and remote manual valve operating gear serves this purpose. The well deck drains are manually opened when preparing to ballast the ship to aid in even flooding of the well deck. As the ship is deballasted, these drains permit the complete drainage of the well deck, the water barrier recess, and the ramp stowage space.
3. Operations. Ballasting is accomplished by flooding directly from the sea, or by using the firemain system. Deballasting is accomplished by eductors, pumps, gravity, and compressed air. In an emergency, other methods are available to ballast and or deballast such as filling tanks using fire hoses or emptying tanks using P-250 portable pumps, submersible pumps and portable eductors.

1. During ballasting operations, there are many risks such as internal flooding caused by overfilling ballast tanks or causing a list condition, which decreases stability, by improper sequencing of tanks. To prevent any flooding or stability problems certain precautions must be taken when conducting ballasting operations. When topping off tanks keep a close watch on tank level indicators (TLIs). Most ballast tanks are not designed to withstand high pressure and often the access covers to the tanks are inside the skin of the ship. Over pressurizing a tank can either burst the tank or blow the access cover off causing flooding. Ensure that tanks on port and starboard sides are filled or emptied simultaneously so as not to create a list condition. While deballasting using air, it is important for the engine room to open the vents on all condensers and pumps that are taking a suction directly from the sea. Remember, we’re using compressed air to force the water out of the ballast tanks and there is a strong chance some of that air will blow out the bottom of the tanks and cause condensers and pumps to become air bound.
2. The characteristics and the physical arrangements of a ballasting/deballasting system and components are fundamentally the same for all of the amphibious ships. Of course, there are variations in size and number of tanks, number of hydraulic stations and number of deballast air compressors.

4. Communications. All normal communications for safe and effective control of ballasting operations are made by the sound powered telephone circuits 1JV and 6JV (primary), and 21MC (secondary). Messengers and the dial telephone system are used as supplemental and backup methods of communication.
5. Other Ballasting Systems. Non-amphibious ships also have the ability to ballast and deballast in order to maintain or correct stability.

1. Automatic fuel oil compensating systems provide automatic ballasting for all fuel oil storage tanks. By constantly supplying firemain water to the tanks through a reducer the tanks are kept full of fuel, water or a combination of the two. Ships equipped with this system include DD 963, DDG 993, DDG 51 and CG 47 classes. Even with the automatic ballasting system there are still some tanks and voids that must be manually ballasted. Oilers can typically ballast cargo fuel tanks from the sea to avoid improper attitude and draft when low on cargo fuel.
2. Manual fuel oil tank ballasting is accomplished by using several systems that are interconnected by a manifold. Ballasting water is supplied to the tanks from the firemain system. Tanks can be dewatered by either the bilge stripping pumps or eductors to the main drainage system.

6. Guidance for ballasting. There are many references available that will give guidance on how to conduct ballasting operations and how to manage the ship’s liquid loading. The following references provides guidance on ballasting:

1. Fuel oil tank sequencing section of Engineering Operational Sequencing System (EOSS)
2. Flooding effects diagram. DC Plate #1. Uses a color code system to indicate whether flooding of a compartment increases stability, decreases stability or has no effect on stability. In addition, for specified compartments it lists the tonnage of salt water if 100% flooded and the transverse moment of the weight in foot tons about the centerline of the ship for all asymmetrical compartments.
3. Liquid load diagram. On the very bottom of DC Plate #1 giving information for all tanks including the following:

1. Capacity
2. List caused by filling
3. Change in draft aft and forward caused by filling
4. Use of each tank
5. Damage control book
6. TYCOM Instructions
7. Damage Control Stability and Buoyancy, NSTM Chapter 079 Vol. 1. - Can be used to develop a ballast bill if none of the other references apply to your ship.