May 2017: Advice on acceptable freeing port covers

This safety update is issued to raise awareness of the potential serious risk to safety from blocked freeing ports. It provides examples of acceptable freeing ports and safe practice tips for how to best reduce the risks involved.

This safety update is for

  • safe ship management companies
  • ship surveyors
  • Safe Ship Management auditors
  • Maritime NZ Maritime Safety Inspectors
  • fishing vessel owners and operators.



Following the release of the safety update Freeing Port Covers on Fishing Vessels in February 2007, requests have been received from surveyors and Maritime Safety Inspectors for advice on the types of freeing port covers acceptable on fishing vessels.

This guidance note sets out Maritime Rule 40D.23 Water freeing arrangements, the details of why and how Maritime New Zealand is enforcing sliding covers on freeing ports, as well as several photographic examples of acceptable freeing ports.

The Rule

40D.23 Water freeing arrangements

  1. Where bulwarks on open weather parts of the working deck form wells, the minimum freeing port area (A) in square metres, on each side of the ship for each well on the working deck must be determined in relation to the length (l)5 and height of bulwark in the well as follows –
    1. A = K x I
      K = 0.07 for ships of 24 metres or more in length
      K = 0.035 for ships of 12 metres or less in length for ships of less than 24 metres but more than 12 metres the value of k should be obtained by linear interpolation; and
      (I need not be taken as greater than 70 per cent of the ship's length)
    2. where the bulwark is more than 1.2 metres in average height the required area must be increased by 0.004 square metres per metre of length of well for each 100 mm difference in height; and
    3. where the bulwark is less than 900 mm in average height, the required area may be decreased by 0.004 square metres per metre of length of well for each 100 mm difference in height.
  2. The freeing port area calculated according to rule 40D.23(1) must be increased where the surveyor considers that the ship's sheer is not sufficient to ensure that the deck is rapidly and effectively freed of water.
  3. The minimum freeing port area for each well on an open weather superstructure deck must be not less than one half the area (A) given in rule 40D.23(1).
  4. For any ship to which this rule applies where the sea may enter over the stern and flood the deck into a superstructure that is open at its aft end, freeing ports must be fitted in the sides of the open superstructure that are acceptable to the surveyor.
  5. Freeing ports must be so arranged along the length of bulwarks as to ensure that the deck is freed of water most rapidly and effectively. Lower edges of freeing ports must be as near to the deck as practicable.
  6. Freeing ports over 300 mm in depth must be fitted with bars spaced not more than 230 mm nor less than 150 mm apart, or with other suitable protective arrangements approved by the surveyor. If fitted, the construction of freeing port covers must be approved by the surveyor. Sliding covers must not be fitted and no locking devices must be fitted to hinged covers.
  7. The master must ensure that freeing ports are maintained and kept free of any obstruction or means of permanent closing when the ship is at sea.
  8. Where cockpits are fitted in weather decks they must comply with rules 40D.34(7) and 40D.35(7) and efficient non-return means of drainage overboard must be provided.

5 if the bulwark extends for the full length of the well, the length I is the length of the wall.

Note the areas in bold, which highlight both the requirements for minimum freeing port area, as well as the prohibition of sliding covers or lockable hinge covers.

If necessary, the freeing port area of each vessel should be recalculated when the freeing ports become compliant. Placing bars or grills over a freeing port reduces the area for the water to escape. The area should be calculated such that when all covers/grills are down there is sufficient area for the water to escape from the deck.

The rule permits freeing port covers that are approved by the surveyor, as long as they are not sliding covers. Exemptions will not be granted for sliding covers nor for any means of permanent closure of the freeing port while the vessel is at sea.

When inspecting the freeing port covers, take care that covers, such as rubber flaps, are still able to move sufficiently to allow the water to escape rapidly and effectively.

Why Maritime New Zealand is enforcing the freeing port rule

A recent review of Maritime Rule Part 40D, which was conducted to discover the level of non-compliance with the rule for existing fishing vessels, highlighted a considerable number of failures regarding blocked freeing ports through either sliding covers or some form of permanent means of closure. Blocked freeing ports, as illustrated in Freeing Port Covers on Fishing Vessels, play a part in causing free-surface effect, a reduction in freeboard, and an increase in the centre of gravity, all of which are contributory factors in the capsize of fishing vessels.

Maritime New Zealand is concerned about the level of non-compliance of freeing ports. Blocked freeing ports pose a danger to both vessels and their crews.

What now?

A letter will be sent to every SSM fishing vessel owner highlighting the risks associated with blocked freeing ports. The letter will advise that owners will have 3 months, or until the next out-of-water survey (whichever comes first) from the date of the letter to conduct modifications to their freeing ports if they do not comply with the rule requirements.

The rule regarding freeing ports may be enforced under two circumstances:

  • if a Maritime Safety Inspector visits a vessel after 3 months and the vessel is found to contravene the rule, the vessel may be detained by the MSI
  • if an SSM surveyor finds a vessel to be in contravention of the rule during its next out-of-water survey the SSM certificate may be suspended by the SSM company.

Articles in Seafood NZ and Professional Skipper will advertise Maritime New Zealand’s requirement.

Please note that although the letter will not be sent out until May, any vessel you see with sliding covers or a permanent means of closure on freeing ports is in contravention of the Maritime Rules and should be advised of the forthcoming campaign and encouraged to modify their freeing ports immediately.


Safe practice tips

Examples of acceptable freeing ports.

Freeing Port Covers

Original source content - Guidance Notice Issue 1, May 2007: Advice on acceptable freeing port covers.


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