Central Cooling System (Drawing)

Alternative Figure

Very useful objective questions about ship

What does the word "draught" (draft) mean ?
The distance from the waterline to the keel. 

Where is the monkey island ?
On top of the bridge.

What does the word "master" mean ?
The legal title of the captain.

What is the "after peak" ?
An enclosed space at the aft end of the ship.

What does the word "leeward" mean ?
Places where there is no wind blowing.

What does the term "in ballast" mean ?
A ship carrying water in place of any cargo.   

What does the term "coil" mean ?
To stow a rope in a circular fashion.

 What does the word "fathom" mean ?
 A measurement equal to 6 feet (1.83 meters).

What does the word "overboard" mean ?
 To discard items into the sea.

What does the term "weatherside" mean ?
The side of the ship from which the wind blows.

What does the word "gangway" mean ?
The means of access to the ship from the quayside.

What does the word "pallet" mean ?
A tray to carry cargo or on which cargo is fixed.

What does the term "sea time" mean ?
The difference between the ship's clock and Greenwich Mean Time.

What does the term "athwartships" mean ?
Across the ship from one side to the other.

What does the term "turn-to" mean ?
To start work.

What does the word "bitts" mean ?
Short cylindrical steel posts used to secure mooring lines.

What does the word "wake" mean ?
The disturbed water left astern of a ship.

What does the term "capsize" mean ?
To turn over.



          

Short Notes about Propeller

      If propeller not coming out:

• 5 – 10% extra oil pressure to be applied, if not
• Isolate boss & apply dry ice to shaft, if not
• Heat the boss uniformly with low flame torch at not more them 200^OC, if not
• Ask recommendation from manufacturer.

      Check during propeller fixing:

• Ensure Main engine is not turning (hang notice).
• Test report of seal assembly to be checked.
• Report of tail shaft polishing and magnetic crack detection
• Detail report if propeller repaired.
• Report of propeller polishing and crack detection (LPT)
• Visual inspection of threaded part of the shaft and boss.
• Cleanliness of shaft cone and re - roughen of the surface to be checked.
• When fixing to ensure that makers instruction to be followed.
• Radial reference mark on both propeller & shaft to coincide.
• Final push up pressure according to the temp of the boss, if boss TP↓ move oil pr.
• Loading ring should not come out more then 1/3 of the ring width.
• Distance travel by the boss.

Nut bolt to be wire lashed and cemented

Case Study: Hydraulic hose bursting

Introduction

On 10 May 1997, the "JEANNIE," on a voyage from Boulogne, France, was bound for Montreal, Quebec. The vessel, under the conduct of a pilot, was abeam of Lotbinière, Quebec, when the bridge watch realized that the rudder angle indicator was hard-a-port. They tried in vain to bring the vessel back on course by changing the steering gear mode from the steering position on the bridge. At approximately 2255, the "JEANNIE" grounded on the south edge of the channel in the approaches to buoy Q83, before the anchor could be let go or the main engine put astern.^[3]

After the grounding, the tanks were sounded and it was found that only the forepeak was holed. The vessel's pumps were unable to reduce the level of water in the tank below the waterline forward.

On May 11, at approximately 0700, two tugs departed the Port of Québec to assist the bulk carrier. At approximately 1010, as the tugs arrived on the scene, the vessel refloated herself on the rising tide. At 1043, the vessel advised the Quebec Marine Communications and Traffic Services that she had refloated and was anchored on the north side of the channel.

The steering gear of the "JEANNIE", manufactured by Donkin & Co. Ltd., is of the articulated-cylinder type. The gear consists of two units, each including two double-action cylinders. Each unit is fitted with a constant-speed pump. These pumps are mounted on a single hydraulic fluid reservoir. A multiple-valve collector isolates either of the units for maintenance or emergency manual operation.

Accident Analysis

Breaking of a Hydraulic Hose

Visual inspection of the hydraulic hose showed that it was hardened and cracked and that it had separated from the coupling. The deterioration of the hose is attributable to the surrounding sources of heat and wear. When a break occurs on a hydraulic component, the single reservoir quickly empties its contents because of the constant-speed pumps.

Alarms

When the amount of hydraulic fluid in the reservoir drops to a predetermined level, an alarm sounds in the engine control room. A crew member has to go into the steering gear compartment, identify the problem, shut off four valves using a special wrench, and then open two other valves to isolate the unit in trouble and thereby restore steering capability to the vessel. When the first person arrived in the steering gear compartment, the hydraulic fluid reservoir was already empty; thus, nothing could be done to counter the failure.

The low-level alarm apparently sounded in the engine control room. On the bridge, it was noticed that something was wrong when the rudder-angle indicator read hard-a-port and the helmsman could not return the helm amidships despite his efforts. The alarm was apparently not heard by the personnel on the bridge.

Reservoirs

In spite of the direct access to the steering gear compartment from the engine-room, the system was designed in such a way that it would have drained completely even with the intervention of an engineer. The two units are supplied by a single reservoir and there is no storage tank permanently connected to the hydraulic system. Had each of the units been fitted with an independent reservoir, the steering gear would have remained in operation without intervention by the personnel. On some of the more-recently built vessels, the steering gear remains in operation even when one of the units fails.

Regulations

Canadian regulations require that in the event of a failure, steering capability be maintained or speedily restored. The requirements are more stringent, however, for tankers and chemical tankers of over 10,000 gross tons. Such vessels have to be able to restore steering capability less than 45 seconds after failure of a power transmission system. In confined waters, all vessels should be able to regain steering capability in the event of failure regardless of their size or type. Several domestic and foreign tankers and chemical tankers of less than 10,000 gross tons that transit the St. Lawrence River and other confined waters in Canada are not subject to these requirements.

The loss of hydraulic fluid from one of the systems must be able to be detected and isolated automatically so that another system or systems can remain operational.

The International Convention for Safety of Life at Sea (SOLAS), Ch. II-1, Part C, contains regulations for steering gear that are adopted by some classification societies and are also found in the Canada Shipping Act. These regulations apply to all convention vessels. Some of them read as follows:

Regulation 29, Art. 1:

. . . [t]he main steering gear and the auxiliary steering gear shall be so arranged that the failure of one of them will not render the other one inoperative.

Regulation 29, Art. 6.1.3:

. . . the main steering gear is so arranged that after a single failure in its piping system or in one of the power units the defect can be isolated so that steering capability can be maintained or speedily regained.

Regulation 29, Art. 12.2:

. . . a low-level alarm for each hydraulic fluid reservoir to give the earliest practicable indication of hydraulic fluid leakage. Audible and visual alarms shall be given on the navigating bridge and in the machinery space where they can be readily observed; and

Regulation 29, Art. 12.3:

. . . a fixed storage tank having sufficient capacity to recharge at least one power actuating system including the reservoir, where the main steering gear is required to be power-operated. The storage tank shall be permanently connected by piping in such a manner that the hydraulic systems can be readily recharged from a position within the steering gear compartment and shall be provided with a contents gauge.

2.5 Compatibility with International Requirements

Where the main steering gear comprises two identical power units, it should have the same capability and reliability as a main power unit fitted with an auxiliary steering gear, and be capable of being brought into operation from a position on the navigation bridge. In the event of a power failure to either of the steering gear power units, an audible and visual alarm must be given on the navigation bridge.

The steering gear of the "JEANNIE" met regulatory requirements at the time of its construction. This type of steering gear, in use on both foreign and Canadian vessels, can be modified to prevent such a failure.

Conclusions

Findings

A steering gear hydraulic system hose separated from its coupling, causing the hydraulic fluid reservoir to empty.

The crew could not intervene in time to isolate the defective power unit.

A single reservoir supplied both steering gear units, and there was no storage tank permanently connected to the hydraulic system in such a manner that the system could be speedily brought back into operation.

No audible or visual alarm indicating the problem was noticed by the crew on the bridge.

Following the failure of her steering gear, the "JEANNIE" grounded, causing damage to her forepeak.

This type of steering gear is in use on both foreign and Canadian vessels.

Causes

The "JEANNIE" ran aground because a steering gear hydraulic hose failed and the crew of the vessel could not intervene and regain steering control before the two power units became inoperative.

POWER CALCULATION (Power Card & Draw Card)

Q.  What is power card?

   ü  The power generated in the engine cylinder can be evaluated by indicator diagram.

Q.  What you will get from power card?

   ü  We can get by power card:

       ¨   Mean Indicated Pressure

       ¨   Combustion and compression pressures

       ¨   Evaluation of the combustion process

       ¨   Evaluation of scavenging process

       ¨   Calculation of air temperatures in the compression chamber.

   Q.     How you will calculate power

   o   Determination of the indicated engine output… using power card and PLAN formula

o   In order to determine the indicated power, a set of diagrams are taken consisting of one diagram for each cylinder. The area of the diagrams, and therewith the (MIP) Mean Indicated Pressure is determined by means of a planimeter.

o    MIP =         Wnet (Area of the p-V diagram)              

                           Stroke volume

Power (Watts) = Pm x L x A x n   

Where Pm = Mean Indicated Pressure (N/m²)

             L   = Length of piston stroke (m)

             A  =  Piston area (m²)              

             n   =  Power strokes / second   ….

Note: (for 2 stroke engine  n power stroke/second

            for 4 stroke engine  n/2  power stroke/second)

    Q.     What are the things you consider when calculating power?

o    The following to be considered:

ü  The prop is fully immersed.

ü  The ship is fully laden at an even keel.

ü  The ship is running neither with nor against a head wind or heavy sea.

ü  The ship skin is not fouled by an underwater growth.

     Q.     What are the safety measures you are taking?

o   Before taking a set of indicator diagrams the following precautions should be taken. It is only then the diagram will record truly the engine power.

                        a)      To reduce the effect of friction the indicator piston is removed, the piston and the cylinder cleaned and lubricated with a few drop of cylinder oil.

                        b)      The tightness of the indicator piston in the cylinder should be checked. This can be done by dismantling the piston and allowing it to drop slowly through the cylinder by its own weight. If the bottom of the cylinder is closed the piston should be held at its position.

                         c)      The drum should not hit the stop at end positions. Play in the pencil mechanism will distort the diagram.

                        d)      The cock should be free from accumulation of soot and oil.

                        e)      The stylus should be adjusted to a light writing pressure.

Q. How you will take power card without any error?

o   To take the indicator diagram —

— fasten the instrument to the cock so that the cord is taut.

— Trace the atmospheric line with the cock shut.

— Open indicator cock and lightly press the stylus against the paper till the cycle is described.

— Close the cock.

Q. What is Draw Card?

ü  A draw diagram is in effect a pressure-time diagram which is obtained by moving the drum at constant velocity during the period covering a few degrees before and after the TDC.

Q. How you will take draw card without any error?

ü  Indicator diagram 90⁰ out of phase

ü  After taking the indicator diagram

— disconnect the c Open the indicator cock and pull it by hand. A con1prcs and ignition sequence is recorded. The pull is to be timed when the pencil is upward i.e. the piston is at the TDC.

Q. You have taken draw card, you got compression pressure low, what are causes?

ü  Engine conditions which lower the compression pressure are:

·         Piston ring and liner wear out,

·         Exhaust valve leak,

·         Defective lubrication,

·         Wearing out of bearings,

·         burning out of piston crown

·         Low scavenge pressure, fouling of exhaust and/or scavenge air system, etc.,

Q. What is light spring diagram? How you will take?

ü  The variation of pressure in the cylinder during exhausting and scavenging is magnified in this diagram.

ü  This diagram is taken with a light spring.

Q. How you will asses the light spring diagram?

1-     Exhaust valve open

2-     Scavenge port open

3-     Scavenge port closed

4-     Exhaust valve closed

Fig: Light spring diagram

The pressure during this part of the cycle being low, a light spring is utilised. For most of the time the cylinder pressure is outside the range of the spring. As the pressure drops part of the expansion curve is shown in the diagram. The exhaust opens at 1 and there is an instantaneous drop in pressure (Blow down). Exhaust gases rush towards the exhaust valve creating a pressure wave leaving a low pressure region behind. The pressure drops till the scavenge ports are opened at 2 and the scavenging takes place till scavenge ports close at 3.

The drop in pressure (Blow down) is a measure of clearness of exhaust passages (exhaust back pressure, Fouling of turbine and EGE).

This diagram also shows the pressure of scavenge air inside cylinder when scavenge port closes at 3. The scavenge port opening timing 2 and closing timing 3 is same.

Choked scavenge ports

In power card this defect will show as loss of power, low compression and ignition pressure and high exhaust temperature. A light spring diagram will show a low pressure at point 3 and 4 (closing of scavenge port and exhaust valve). The blow down will be normal indicating normal exhaust back pressure.

High exhaust back pressure

 

 

High exhaust back pressure manifests as loss of power in affected cylinder as well as high exhaust temperature and sooty exhaust. First power card is taken. If the compression pressure is normal and no defect is noticeable in fuel injection, a light spring diagram is taken. High pressure affects scavenging and fuel cannot burn properly.

Blow down is less compared to normal. This increase in back pressure may be due to fouled turbine or EGE.

Q. How could you confirm indicator drive is perfect?

Q. 4-stroke engine, power calculation (different type).

Q. 4-stroke engine power/draw card analysis. What are the limitations in case of 4-stroke engine?

Q. What is power balancing? 

n  Power produced in a diesel engine is related to the quantity of fuel injected and time when injected,

n  Balancing of power between the cylinders is carried out by small adjustments to individual fuel pumps on a running engine.

Q. How you balance power in two stroke & 4-stroke engine?

Q. What consideration you take when balancing power?