Dry-Docking major event , first special survey

  Q:- Why is dry-docking referred to as a major event in the maintenance of a ship?

As a Chief Engineer explain different steps that need consideration while planning a dry-docking project of a ship due for its first special survey.

ANSWER :- 

1. Dry-docking is referred to as a major event in the maintenance of a ship because of reason that without it the underwater portion of ship cannot be assessed and due to the extent of survey/items to be examined during dry docking.
2. Dry docking is a process whereby a ship is brought into a dock which is then emptied of sea   water so that work can be performed on the exterior part of the ship below the waterline.
3. The purpose of dry docking is to examine underwater hull and fittings, assess their  condition and carry out  required repair and maintenance.
4. As per M.S. cargo ship construction and survey rules (INDIA) 1991, every vessel has to dry dock twice in 5 years in which the intermediate dry dock should be at two and half years but can be extended up to 3 years. Intermediate dry dock can be replaced by in water survey, but the ship has to be dry docked at 5 year interval.
5. M.S. cargo ship construction and survey rules 1991 also states that propeller shaft and the tube shaft driving screw propellers shall be withdrawn and surveyed at intervals not exceeding two and half years, but Principal officer can extend it up to 3 years. However, depending upon the tail shaft system like oil bath or water bath, keyless propeller or keyed propeller, the survey requirement can be extended. One of the dry docking has to coincide with the special survey, which is done once in 5 years.

Requirement of special or class renewal survey; - for first special survey ship <= 5 years

  Special Surveys are to be carried out at 5 years intervals to renew the Classification Certificate. 

A docking survey in accordance with the requirements of class is to be carried out as part of the special survey.

there are two special survey  special survey Hull and machinery 

Special survey hull 

The first special survey is to be completed within 5 years from the date of the initial classification survey and thereafter 5 years from the assigned date of the previous special survey. However, an extension of class of 3 months maximum beyond the 5th year may be granted in exceptional circumstances. 

 For surveys completed within 3 months before the expiry date of the special survey, the next period of class will start from the expiry date of the special survey. For surveys completed more than 3 months before the expiry date of the special survey, the period of class will start from the survey completion date.

The special survey may be commenced at the 4th annual survey and be progressed with a view to completion by the 5th anniversary date. 

 As part of the preparation for special survey, the thickness measurement and survey programme is to be dealt with, in advance of the special survey. The thickness measurement is not to be held before the 4th annual survey.

 Record of special survey will not be assigned until the machinery survey has been completed.

Special Survey I (5 years old) :-Tank internal examination requirements for steel craft

• Peaks:-All tanks
• Salt water ballast:-All tanks
• Lubricating oil:-None
• Fresh water:-None
• Oil fuel:-None
• Sanitary:-All tanks

 Thickness measurement 

The thickness measurements are normally to be by means of ultrasonic test equipment and are to be carried out by an approved firm.

Thickness measurements may be carried out within the 12 months prior to the due date of the special survey.

The minimum requirements for thickness measurements are As per ship type and age of ship.

Thickness measurements are normally to be carried out under the supervision of the Surveyor. However, the Surveyor may accept thickness measurements not carried out under his supervision subject to re-checking the measurements as deemed necessary to ensure acceptable accuracy.

A thickness measurement report is to be prepared. The report is to give the location of measurements, the thickness measured as well as corresponding original thickness. Furthermore, the report is to give the date when the measurements were carried out type of measurement equipment, names of personnel and their qualifications and has to be signed by the operator. The report is to be verified and countersigned by the Surveyor.

Special Survey I (5 years old) Suspect areas, as required by the Surveyor and may include areas where the coatings are found to be other than in GOOD condition .

special survey- machinery

 The machinery special survey becomes due five years from the date of build or from the last assigned machinery special survey (SSM) date.

 Upon satisfactory completion of the machinery special survey an appropriate record will be entered in the supplement of Register of Ships.

Continuous survey of machinery (CSM)

 At the request of the Owners and upon approval of the proposed arrangement a system of continuous survey of machinery (CSM) may be undertaken whereby the requirements of special survey of machinery are completed within a five year period. The survey cycle is to be such as would ensure that the interval between consecutive examination of each item does not exceed five years and it is expected that approximately an equal proportion of the machinery would be subjected for survey each year.

Further parts of machinery may require to be opened if  any defects are found during the course of Survey of any item and the defects made good to the satisfaction of the Surveyor

Survey requirements machinery

         All auxiliary engines driving the generators and other essential machinery together with their coolers and attached pumps are to be opened up and examined as considered necessary by the Surveyor. Alarms and safety devices fitted on these units are to be included in this survey.

      All air receivers and other pressure vessels for essential services together with their mountings and safety devices are to be cleaned internally and examined internally and externally. If an internal examination of an air receiver is not practicable it is to be tested hydraulically to 1.3 times the working pressure.

        Air compressors are to be opened up and coolers tested as considered necessary by the Surveyor. Selected pipes in the starting air systems are to be removed for internal examination and hammer tested. If an appreciable amount of lubricating oil is found in the pipes the starting air system is to be thoroughly cleaned by steaming or other suitable means. Some of the pipes selected are to be those adjacent to the starting air valves at the cylinders and to the discharges from the air compressors.

 Propulsion system:-shafts thrust block and all bearings are to be examined. The lower halves of bearings need not be exposed if alignment and wear are found to be acceptable.

      An examination is to be made as far as practicable of all propulsion gears complete with all wheels, pinions, shafts, bearings and gear teeth, thrust bearings and incorporated clutch arrangements.

All pumps, heat exchangers, forced draught fans, etc. used for essential purposes are to be opened up and examined as considered necessary by the Surveyor.

 The valves, cocks and strainers of the bilge system including bilge injection are to be opened up as considered necessary by the Surveyor and together with pipes, are to be examined and tested under working conditions. If non-return valves are fitted in hold bilges, these are to be opened up for examination.

Reduction gears, flexible couplings and clutch arrangements are to be opened as considered by the Surveyor in order to permit the examination of the gears, gear teeth, spiders, pinions, shafts and bearings, reversing gears, etc. Essential parts of other power transmission arrangements are to be opened up and examined as considered necessary by the Surveyor.

Holding down bolts and chocks of main and auxiliary engines, gear cases, thrust blocks and tunnel bearings are to be checked.

 Intermediate shafts and bearings, thrust bearings and their seating are to be examined. The lower halves of bearings need not be exposed if alignment and wear are found acceptable.

 Sea connections:- All openings to the sea including sanitary and other overboard discharges in the machinery spaces and pump rooms together with valves and cocks are to be examined internally and externally. 

 Internal combustion engines for propulsion:-All working parts of the engines and their attached pumps are to be opened and examined. These are to include all cylinders, cylinder heads, valves and valve gear, pistons, piston rods, cross-heads, guides, connecting rods, crankshafts, vibration dampers and all bearings, camshafts and driving gear, fuel pumps and fittings, scavenge pumps, scavenge blowers and their prime movers, superchargers, air compressors, inter coolers, clutches, reverse gears, crankcase door fastenings and explosion relief devices and such other parts of the machinery as may be considered necessary. Integral piping systems are to be examined. The maneuvering of engines is to be tested under working condition.

Unattended machinery spaces/Remote control systems:-the proper operation of the safety devices will be checked, in particular, such as emergency stops, emergency astern movement, standby control of the propelling gear, fire alarm.The log recording the operating conditions is to be checked.  

Electrical equipment survey requirements:-An electrical insulation resistance test is to be made on the electrical equipment and cables. 

 The fittings on the main and emergency switchboards, verify that they provide suitable protection for their respective circuits.

 Generator circuit-breakers are to be tested, so far as is practicable, to verify that protective devices, including preference tripping relays, if fitted, operate satisfactorily.

The electric cables and their securing arrangements are to be examined, 

All generators and steering gear motors are to be examined and are to be operated under working conditions, though not necessarily under full load or simultaneously.

Navigation light indicators are to be tried under working conditions, and correct operation on the failure of supply or failure of navigation lights verified.

Emergency lighting, transitional emergency lighting, supplementary emergency lighting, general emergency alarm and pump address systems are to be tested as far as practicable.

 Where batteries provide the source of power for any essential services, their installation, including charging and ventilation arrangements, is to be examined.

Preparation for survey:-

C/E should consider following things while planning for dry dock /first special survey

The ship is to be prepared for overall survey in accordance with the requirements . The preparation is to be of sufficient extent to facilitate an examination to ascertain any excessive corrosion, deformation, fractures, damages and other structural deterioration. 

• Defect list to check
• class status report to be checked and prepare a list of items due for the survey. and send it to the superintendent for arranging surveyor for this.
• Necessary action, such as Tanks and spaces are to be safe for access, i.e. gas freed, ventilated and illuminated. 
• Also stock of spare ,tools and store to be check and ensure adequate is available for dry docking .
• The Detailed dry dock plan will be prepared together with the ships superintendent .
• Check painting requirements for hull and advise master accordingly for raising a requisition for paints.
• Check the; last anchor chain report and accordingly prepare for anchor and anchor chain inspection.
• Carry out a gauging inspection / thickness measurement and establish the scope of steel repairs.
• Make a complete list of all certificates expiring; list of conditions of class to be dealt with is clear, list of new applicable regulations to be attended to is available.
• Modifications /fabrications if any as per new regulations should be prepared.
• In preparation for survey and thickness measurements and to allow for a thorough examination, all spaces are to be cleaned including removal from surfaces of all loose accumulated corrosion scale. 
• Sufficient illumination is to be provided to reveal corrosion, deformation, fractures, damages or other structural deterioration.
• For the survey, means are to be provided to enable the surveyor to examine the hull structure in a safe and practical way. 

 Equipment for survey :-Thickness measurement is normally to be carried out by means of ultrasonic test equipment. The accuracy of the equipment is to be proven to the Surveyor as required. Thickness measurements are to be carried out by a firm approved by the society.

One or more of the following fracture detection procedures may be required if deemed necessary by the Surveyor: 

• Radiographies equipment; 

• Ultrasonic equipment; 

• Magnetic particle equipment; 

• Dye penetrant.
Document and drawing to be kept ready before dry dock

• General arrangement plan
• Tank arrangement and capacity plan
• Shell expansion plan
• Fire plan
• Muster list
• Detail of ship's communication system
• Class survey reports,