Dock inspection is a very important ship inspection, that is, dock repair inspection. Dock inspection generally refers to the relevant inspection of the ship in the dry dock, including the external inspection of the ship bottom and the classification dock inspection. After obtaining the approval of the classification society and the flag state, the external inspection of the ship bottom and the dock inspection of the classification can also be carried out when the ship is floating (underwater inspection).

The general classification society also considers that the external inspection of the ship bottom is completed at the same time after the completion of the classification dock inspection. After completing the external inspection of the ship bottom, the surveyor shall sign in the signature column of the external inspection of the ship bottom in the cargo ship construction safety certificate to keep the certificate valid. Similarly, after completing the classification dock inspection, the surveyor shall also sign in the relevant signature column of the classification certificate to keep the classification certificate valid.

Then, do you know what items are to be inspected in dock inspection? Here, the author gives a detailed introduction to relevant issues:

1、 External inspection of ship bottom

This check is mandatory from SOLAS as follows:

Article 10 Inspection of cargo ship structure, machinery and equipment in Chapter I (v) In any 5-year period, except for the application of Article 14 (e) or (f), the exterior of the ship bottom shall be inspected at least twice. If Article 14 (e) or (f) is applicable, the 5-year period can be extended to be consistent with the extension of the validity of the certificate. In any case, the interval between any two such inspections shall not exceed 36 months; (For the understanding of "any five years", see another article of mine, see below: understanding of any five-year period for external inspection (dock inspection) of cargo ship SC certificate)

Detailed explanations and regulations on the external inspection of the ship bottom in the Inspection Guide of the 2011 Inspection and Certification Coordination System:

Times

The external inspection of the cargo ship bottom shall be carried out at least twice in any 5-year period, unless the requirements of Article I/14 (e) or (f) of SOLAS 74/88 are applicable. One such inspection shall be conducted at or after the fourth annual inspection in combination with the cargo ship construction safety certificate or the renewal of cargo ship safety certificate. If the cargo ship construction safety certificate or cargo ship safety certificate has been extended according to the requirements of Article I/14 (e) or (f) of SOLAS 74/88, the five-year period can be extended to be consistent with the validity of the certificate. In all cases, the interval between any two such inspections shall not exceed 36 months.

Underwater inspection:

Generally, the external inspection of the ship bottom should be carried out in the dry dock, but alternative inspection can also be considered when the ship is floating. Except for bulk carriers and oil tankers, special consideration shall be given to ships aged 15 years and above before allowing such inspections when they are floating.

For bulk carriers and oil tankers aged 15 years or above, the external inspection of the ship bottom shall be carried out in the dry dock. Only when the ship is in good condition and has appropriate equipment and properly trained personnel can the inspection be carried out when the ship is floating. For ships that implement enhanced inspection, the applicable provisions of 2.2.2 in Annex A or B of the revised Guidelines for Procedures for Enhanced Inspection during Bulk Carriers and Oil Tankers Inspection (Resolution A.744 (18)) shall be implemented.

External inspection items of ship bottom:

1. Check the shell plating, including the bottom shell plating, the head shell plating, the keel, the bilge keel, the bow column, the stern column and the rudder;

2. Pay attention to the measured clearance of rudder bearing;

3. Check the propeller and shaft seal as much as possible;

4. Pay attention to the measured clearance of propeller shaft as much as possible;

5. Check the sea valve box and filter;

6. Inspection of relevant items shall be carried out at the same time of inspection: those items that can only be inspected in the dry dock or underwater for external inspection of the ship bottom include the following items:

1) Internal inspection shall be carried out on representative places used for water ballast for ships over 5 years old;

2) Internal inspection shall be carried out at the selected loading place for ships with a ship age of more than 10 years (excluding ships only engaged in carrying dry goods);

3) For ships over 15 years old and only engaged in carrying dry cargo, internal inspection shall be conducted at the selected loading place.

4) For cargo ship hull, machinery and equipment, additional requirements for oil tanker inspection shall include:

(1) If there is any doubt about the condition of each pipeline system when checking, the pipeline system can be required to be pressure tested or measured, or both. Special attention shall be paid to repair such as welding cladding;

(2) Internal inspection shall be carried out at the selected loading place for ships older than 10 years;

(3) Insulation resistance test shall be carried out for electrical circuits in dangerous areas such as cargo pump room and area adjacent to cargo tank. However, if appropriate test records are kept, the latest reading shall be considered.

2、 Classification dock inspection

According to the relevant requirements of CCS, the in dock inspection of cargo ships shall be conducted not less than twice within five years, and the longest interval shall not be more than three years, but one of them shall be conducted during special inspection. CCS can shorten the interval of in dock inspection according to the specific conditions below the hull waterline.

Specific items and main requirements of classification dock inspection:

1. Shell plating

Check the corrosion, wear and deformation of shell plating (including bottom plate, side shell plating and bilge strake) and its welds

2. Keel plate

Refer to the above inspection requirements.

3. Bilge keel

The bilge keel is allowed to have appropriate deformation that does not affect its effectiveness, but in case of large deformation, fracture damage or crack, permanent repair shall be carried out. Attention should be paid to checking the condition of the outer plates at the front and rear ends of the bilge keel.

4. Bottom plug

Check the bottom plugs of all liquid tanks, including seawater, fresh water and oil tanks.

5. Stern and stern post

Check the condition of stern and stern post, pay special attention to the corrosion of outer plates and welds, the outer plates at the connection of stern tube support, axle support and hull, the welds between stern post and stern post cladding, and the rudder bracket in the stern post.

6. Accessories (apron, hydrofoil, etc.)

Check the underwater structures attached to the hull, such as apron sealing structure of hovercraft, hydrofoil of hydrofoil craft, anti rolling fin, rectification facilities, etc.

7. Submarine valve box and its grating

Check the internal condition of the submarine valve box, the fastening reliability of the submarine valve box grille, and the integrity of the purging device, the vent pipe and its valves (if any). The surveyor may require thickness measurement (referring to the dock inspection between two special inspections), hydrostatic test, and hydrostatic test after the repair of the submarine valve box when he deems it necessary.

8. Seabed valve

Check the technical conditions of high and low seawater inlet valves, emergency suction valves and their connectors. Pay attention to the corrosion and fixation of valve bodies, as well as the opening and closing indications of valve stems, valve cores, valve seats and valves.

9. Side discharge valve

Check the technical conditions of the side discharge valves and their connections for the cooling sea water, ballast water, water discharge and bilge water of the main engine and auxiliary engine. See the above article.

10. Sanitary water discharge valve

Check the technical conditions of the side discharge valve and its penetration for sanitary water, see the above article.

11. Other openings in the hull

Check the structure and tightness of these openings.

12. Rudder (disassembled for inspection or on-site inspection)

1) Measuring records of rudder blade 2) rudder stock 3) rudder pin 4) rudder shaft 5) connecting flange and bolt 6) rudder.

13. Water jet propulsion device

1) Impeller housing and impeller 2) Stern seal plate 3) Shaft seal and wear 4) Fastening bolts

14. Oil lubrication sealing device of propeller shaft

Check and confirm the effectiveness of the sealing device (see the inspection items of propeller shaft and tail pipe shaft for details).

15. Propeller

Check the integrity, bending deformation and corrosion of the propeller, anti cable device, rectification device and fastening device (see the inspection items of propeller shaft and tail pipe shaft for details).

16. Boiler blowdown valve

Check the overboard discharge valve specially used for the blowdown outlet under the boiler, which is sometimes set in the submarine valve box.

17. Dynamic positioning/lateral thruster

Check the conditions of these devices and conduct tests (see inspection items of propeller shaft and tail pipe shaft for details).

18. Tail shaft bearing clearance

When conducting the dock inspection specified by the classification separately, the stern shaft bearing clearance shall be measured (see the inspection items of propeller shaft and stern tube shaft for details).

19. When the ship is in dock repair, the mooring test shall be carried out to confirm that the main and auxiliary machinery operate normally.

Inspection of propeller shaft and tail pipe shaft

The basic task of the ship shafting is to transmit the power of the main engine to the propeller, and at the same time, transmit the thrust generated by the rotation of the propeller to the hull to promote the ship movement. The propeller shaft is externally connected with the propeller inline intermediate shaft and the main engine runs through the inside and outside of the ship, so the working conditions are very bad. Therefore, the purpose of inspection within a certain period is to ensure that the tail pipe shaft and propeller shaft are in good working condition to prevent accidents caused by wear, fatigue or damage.

Inspection contents of stern tube shaft and propeller shaft of general marine propeller device:

1. Fit of tail pipe shaft, propeller shaft (sometimes with copper sleeve) and propeller

2. Stern bearing

3. Stern tube and accessories

4. Stern shaft sealing device

Generally, the inspection clearance for shaft withdrawal is 2 and a half years (plus/minus 6 months). The propeller and shaft should be removed and completely withdrawn. The relevant parts of the shaft cone should be inspected by crack detection method (such as magnetic powder or coloring); Measure the bearing spacing. If any, measure the bearing settlement, check the tightness of oil seal device, and check the tail bearing

However, under the following conditions, the withdrawal inspection interval of the shaft can be extended as follows:

(1) Single axis layout is extended from 3 years to 5 years;

(2) Multi axis layout is extended from 4 years to 5 years.

1. The propeller shaft and tailpipe shaft have continuous bushing protection, or oil lubricated bearings and approved oil seal devices are installed, or the tailshaft is made of anti-corrosion materials;

2. The propeller key is installed on the tapered propeller shaft and its design details are approved;

3. The propeller is installed on a keyless tapered propeller shaft. The shaft is protected from seawater corrosion and its design details are approved;

4. The propeller is installed at the rear end of the propeller shaft by means of integral flange connection. The shaft and its accessories are not easy to be corroded by seawater, and its design details are approved;

3、 Underwater inspection

Generally, the dry dock inspection must be carried out in the dry dock, but in some cases, the underwater inspection can be substituted after obtaining the approval of the classification society and the flag state.

Scope and requirements of underwater inspection

As far as possible, the underwater inspection shall be the same as the normal dock inspection to obtain the relevant data of the ship, such as thickness measurement and nondestructive testing, and the measurement of the propeller shaft bearing clearance and rudder bearing clearance lubricated by water.

Through the visual inspection of divers, underwater camera and underwater photography, as well as the monitoring of the inspection by the ship surveyor through two-way communication equipment and closed-circuit television, the underwater part of the ship can be visually inspected, such as checking whether the propeller blades are damaged, the condition of the hull outer plate, etc.

The underwater part shall be fully photographed and the following parts shall be photographed:

——Rudder blade

——Seabed valve box

——Propeller

——Side pushing device

——Anti corrosion zinc block or cathodic protection

4、 Concluding remarks

Docking repair refers to the activity that the shipowner arranges the ship to enter the dock of the shipyard for relevant repair, while dock inspection refers to the activity that the classification society inspects the repair items of the ship in the dry dock. Only the dock repair satisfactory to the classification society can be signed in the relevant certificate as a record.

Docking repair and inspection is a major project, which requires good communication and cooperation between the shipowner and the classification society to be successfully completed. I hope the above content will help you.

Understanding of any 5-year period for external inspection (dock inspection) of the bottom of cargo ship SC certificate

The keel of an international voyage freighter was laid in 2003, with a gross tonnage of 9554 and Belize flag. Its cargo ship construction safety certificate (hereinafter referred to as the SC certificate) was issued on November 17, 2013 and expired on November 16, 2018. Its external inspection (dock inspection) of the ship bottom was conducted on August 10, 2010 and November 24, 2012, and signed on May 28, 2015. At present, the ship owner has reported to the flag state for approval, It is planned to complete the renewal of the International Oil Pollution Prevention Certificate (hereinafter referred to as the IOPP Certificate) in advance on June 15, 2017 to avoid the requirement of IMO for mandatory installation of the ballast water management system. The IOPP Certificate will expire on November 16, 2018. When the IOPP Certificate is renewed, the classification society will be applied for the annual inspection of the SC Certificate.

At present, the ship owner has 2 questions:

If the IOPP is replaced in advance and the annual inspection of the SC certificate is completed at the same time, will the validity of the SC certificate be shortened?

2. What is the latest date for the next external inspection (dock inspection) of the ship bottom?

First, we will read the first question and read the relevant provisions of the Convention:

SOLAS 2009 Chapter I/14 Term of Validity

(h) If the annual inspection, intermediate inspection or periodic inspection is completed before the time limit specified in the relevant rules, then:

(i) The anniversary date indicated on the relevant certificate shall be signed for amendment, and the amended anniversary date shall not be more than 3 months from the date of completion of the inspection;

(ii) The subsequent annual inspection, intermediate inspection or periodic inspection required by the relevant rules shall be completed at the intervals specified in these rules using the new anniversary date;

(iii) If one or more corresponding annual inspections, intermediate inspections or periodic inspections are carried out so that the maximum inspection interval specified in the relevant rules is not exceeded, the expiration date may remain unchanged.

Assuming that this round of annual inspection of SC certificate will be completed on June 15, 2017, we first need to revise the anniversary date according to the above clause (i). In order to maximize the use of rules and open the annual inspection interval, we generally revise the anniversary date as: 3 months after June 15, that is, September 14. Then three months before and after September 15, 2018, that is, from June 15 to December 14, is the window period for annual inspection.

However, the certificate renewal inspection will be carried out before November 16, 2018, so this annual inspection is not necessary, and the certificate renewal inspection will be carried out directly. It can be concluded that this advance annual inspection will not affect the validity of the SC certificate, nor will it add another annual inspection. Because the maximum interval of any inspection mentioned in the above clause (iii) has not been exceeded.

Let's take another look at the second question and read the relevant provisions of the Convention:

SOLAS 2009 Chapter I/10 Inspection of Cargo Ship Structure, Machinery and Equipment

(5) In any 5-year period, the exterior of the ship bottom shall be inspected at least twice, except for those applicable to Article 14 (e) or (f). If section 14 (e) or (f) applies, the five-year period may be extended to coincide with the extension of the validity of the certificate. However, in any case, the interval between any two such inspections shall not exceed 36 months;

2011 Inspection Guide for Inspection and Certification Coordination System (HSSC)

5.7 The meaning of "any 5-year period"

Reference: SOLAS 74/88 SOLAS Article I/10 (a) (v).

Any 5-year period means the 5-year period of validity of the Cargo Ship Construction Safety Certificate or the Cargo Ship Safety Certificate.

We simply estimate according to the requirements of 5 years and 36 months. The next docking inspection date is: November 24, 2012 plus 5 years is November 24, 2017, and May 28, 2015 plus 36 months is May 28, 2018. Literally, we must conduct the docking inspection on November 24, 2017 to meet the requirement that any five-year period should have at least a second inspection.

But in fact, we carefully studied the interpretation of HSSC2011/5.7 and found that, first of all, the five-year term refers to the five-year validity of the SC certificate or SE certificate. That is to say, during the five-year period from November 17, 2013 to November 16, 2018, there are two inspections to meet the requirements, and it is not necessary to select any one to break the five-year period beyond the five-year validity of relevant certificates.

"However, in any case, the interval between any two such inspections shall not exceed 36 months". In combination with the previous expression of this sentence, in any case, it should refer to a 5-year extension or no extension. Any two such inspections shall refer to any two adjacent external inspections of the ship bottom, including only the two adjacent external inspections of the ship bottom within a 5-year period and two 5-year periods before and after the crossing. Therefore, "no more than 36 months" is a very mandatory requirement. If you read the original English text, it may be easier to understand the above analysis.

According to the above analysis, the deadline for the next docking inspection of this round should be May 28, 2018.

In addition, according to the provisions on extension in Article 10 (V) of Chapter I of SOLAS 2009, this five-year period can be broken through to keep consistent with the extension of the SC certificate. That is, if the SC certificate of this round is extended to February 16, 2019 (no more than 3 months), the requirements for at least a second inspection can be completed from November 17, 2013 to February 16, 2019. Of course, such extensions need to be approved by the flag State.

Some people asked why the expiration date of the certificate was not kept consistent with the completion date of the external inspection of the ship bottom. In fact, due to the practical difficulties of the inspection, it was impossible to complete the external inspection of the ship bottom (dock inspection) when the certificate replacement inspection was just completed. In practice, after the ship was undocked, it would continue to carry out relevant repair projects in the shipyard, which led to the delay of other inspection projects. In addition, it was also possible to arrange dock repair in advance because of problems in the dock arrangement or equipment failures. Therefore, the signing position of the external inspection (dock inspection) of the ship bottom for two times is provided in the SC certificate.

In brief, we can generally understand the above two signatures in this way: two signatures must be completed within the validity period of the ship's SC certificate, a total of four external inspection records of the ship bottom can be recorded in the SC certificate, and the interval between any two signatures must be within 36 months. If the certificate is extended, the 5-year period of two signatures can also be extended, but the interval between the two signatures must also be kept within 36 months.