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Testing of weather tight integrity of mechanical steel hatch covers

Types of hatch covers will vary depending upon the construction of the vessels, and they form a major part of the vessel's watertight integrity and therefore, require a lot of attention. Steel hatch covers should be:

Drainage channels: Should always be cleaned before hatches are closed, and kept free from rust scale and cargo debris. Damaged channels should Be repaired immediately and then painted to prevent corrosion. Drainage channels are located along the cross-joint and on the coaming between the compression bar and the inner coaming.

Fig: Damaged rubber packing

Fig: Damaged rubber packing

Testing of weather tight integrity of hatch covers

Different testing methods available and they can be used individually or in combination with other testing methods to get the best results.
  1. Leakage traces on inner hatch coaming plating
  2. Light infiltration test
  3. Chalk test
  4. Putty test
  5. Hose test (Seaworthiness & cargo worthiness)
  6. Ultrasonic test
  7. Smoke test
  8. Air test

Fig: Light Infiltration Test

Chalk Testing

When performing a chalk test, the top edge of every compression bar is covered with chalk. Hatches are then fully closed and reopened. The rubber packing is examined for a chalk mark, which should run continuously along the packing’s center. Gaps in the chalk mark indicate lack of compression. Chalk testing merely indicates if hatch panels are aligned and compression achieved. It will not show whether compression is adequate and therefore it is not a test for weather tightness.

Fig: Hose Testing

Hose Testing

The general procedure for hose testing is to apply a powerful jet of water from a 20-50mm diameter hose fitted with a 12mm diameter nozzle held at a distance of 1-1.5 metres from a hatch joint, moving along the joint at a speed of 1 meter every 2 seconds

Fig: Leakage traces on hatch coaming

Ultrasonic testing

The test involves placing (with hatches closed and secure) an electronic signal generator inside the cargo hold. A sensor is then passed around the outside of all compression joints. Readings taken by the sensor indicate points of low compression or potential points of leakage. Ultrasonic testing overcomes the majority of limitations associated with hose testing and can be carried out when holds are loaded

Best practices

  1. carry out regular examination of the hatch covers, hatch beams and coamings to identify:
    – General levels of corrosion (check with your classification society for corrosion allowances);
    – localized corrosion at welded connections (grooving);
    – Cracks in joints and weld metal;
    – Permanent distortion of plating and stiffeners;
  2. call a Class Surveyor and carry out repairs as soon as possible when there are:
    – Indications of excessive corrosion e.g. holes or local buckling of the top plate;
    – Cracks in main structural joints;
    – Areas of significant indentation, other than localized mechanical damage;
  3. be particularly vigilant after heavy weather;
  4. rectify any steel-to-steel fault before renewal of rubber packing.
  5. replace missing or damaged hatch gaskets (rubber packing) immediately. The minimum length of replaced gasket should be one metre;
  6. keep hatch coaming tops clean and the double drainage channels free of obstructions. (Open hatch covers to clean coaming tops and the double drainage channels after loading bulk cargo through grain or cement ports);
  7. keep cleats and wedges in serviceable condition and correctly adjusted;
  8. keep hauling wires and chains adjusted correctly;
  9. attach locking pins and chains to open doors and hatches;
  10. keep wheels, cleats, hinge pins, haul wires, and chain tension equipment well-greased;
  11. test hydraulic oil regularly for contamination and deterioration;
  12. keep hydraulic systems oil tight;

Related information

Steel hatch cover maintaining watertightness - Classification society guideline

Cargo holds readinesss, maintenance requirement, preventing stevedore damages & safety aspects

Watertight integrity for cargo holds & hatch cover strength requirements for bulk carriers

High rate of corrosion for bulk carriers and preventing methods

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