nbr 10728 boat davits

ABNT STANDARD NBR 10728

LIFEBOATS DAVIT AND WINCH Specification

1. Objective

This standard specifies the requirements and conditions for the acceptance and/or receipt of gravity type davits and winches for lifeboats.

This standard complies with SOLAS 1974 Amendments 83

2. Complementary standard

The following complementary documents shall be consulted:

NBR 6890 – Galvanized wire ropes for marine use – Specification

3. Definitions.

The definitions on items 3.1 to 3.13 shall be adopted in this standard.

3.1 Storage

Action to be performed by the winch with the lifeboat, retrieving it to the position where it will be stored for the journey.

3.2 Release

Action of releasing and lowering the lifeboat.

3.3 Lifting

Action of lifting the lifeboat up.

3.4 Weight of manned lifeboat

Sum of the light weight of the lifeboat, equipment weight (including consumable, water, lubricating oil, fuel oil and accessories) and crew weight.

Note: Crew weight is calculated by the multiplication of the number of crew members for which the boat is designed by the average weight of each crew member, considered as 735 N.

3.5 Weight of loaded lifeboat

Sum of the light weight of the lifeboat, equipment weight (including consumables, water, lubricating oil, fuel oil and accessories) and weight of maximum number of passengers and crew for which the boat is designed or specified.

Note: The average weight of each passenger or crew member shall be considered as 735 N.

3.6 Davit working load

Load resultant of the sum of loaded lifeboat weight and weight of chain blocks, chains and wire ropes.

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3.7 Winch working load

Calculated by dividing the maximum load applied to the winch during release, lifting or storage operations, including weight of chain blocks, chains and wire ropes, whichever is greater, by the effective reduction rate applied by the sheave system.

3.8 Lifting load

It is the sum of manned lifeboat and chain blocks, chains and wire ropes during the retrieving operation or storage, respectively.

3.9 Test load

Load to be used during the performance of tests on davits, winches and accessories, respectively.

3.10 Rope angle

Angle between the drum centerline and the line where the wire rope leaves the drum or the pulley (or similar). See illustration.

Illustration

Rope Angle

3.11 Retention hook

Devices installed on the upper part of the davit that, along with the chains, avoid the wire ropes of being under tension when not in operation.

3.12 Swing davit

Davit that swings overboard to release the boat, turning around an axle.

3.13 Rolling davit

Davit that rolls overboard in a rolling track to release the boat.

4. General provisions

4.1 Construction

4.1.1 The minimum steel plate thickness to be used on structural components shall be 6 mm.

4.1.2 All material used to hold the boat shall have a certificate warranting their resistance.

Note: fragile materials are not allowed.



4.1.3 The minimum safety factor to be applied for the rupture load calculation for release, lifting and storage of the lifeboats shall be as follows:

a) 4.5 for structural elements, winches and parts not directly related to the support of the lifeboat;

b) 6.0 for chains, slings, wire ropes and all parts directly related to the support of the lifeboat.

Note: other safety factors may be accepted at the competent Authority’s discretion.

4.1.4 The davit shall be designed to safely drop the lifeboat with all equipment and with or without crew, even with the ship under the following conditions:

a) 20 deg. list and 10 deg. trim;

b) 20 deg. list and no trim;

c) no list and 10 deg. trim.

Note: On tanker vessels, chemical vessels or gas carriers the davits shall be capable of operating with a list angle as defined by the Stability Under Distress calculation if this is greater than 20 deg., in relation to the closest side to the water.

4.1.5 The minimum distance between the lifeboat and the ship hull shall be 300 mm in the following conditions:

a) davit completely extended overboard;

b) ship without list or trim;

c) accessories excluded.

4.1.6 The available force to extend the davit shall exceed the sum of the inertial forces on the winch, wire rope system, pulleys and sheaves, to avoid the need to push the davit out.

4.1.7 On rolling type davits, the roller track beams or guides shall be inclined at least 30 deg. related to the horizontal line, with the vessel without list or with such a list that the davit arm is able to roll over them even with an opposite list.

4.1.8 For design purposes, the friction losses shall be as follows:

a) for pulleys:

- bronze bearing or similar: 5%

- ball bearing or similar: 2%

b) for rolling wheels:

- bronze bearing or similar: 5%

- ball bearing or similar: 3%

Note: rolling or sliding parts shall be provided with suitable lubricating means. Self-lubricating materials are also accepted.



4.1.9 Davit shall be provided with retention hooks designed to allow the releasing of the main chain block with an opposite list of 20 deg.

4.1.10 Wire ropes shall be galvanized or equivalent.

Note: Quality certificates dully approved by the Government Authority or its authorized organs shall be presented to enable the material traceability.

4.1.11 The diameter of the pulley shall be at least 12 times greater than the wire rope diameter. The pulley diameter shall be measured at the bottom of the groove.

Note: The rate pulley x wire rope is based on the use of steel cables 6 x 37 + AF according to standard NBR 6890. Other types may be used provided the pulleys are suitably sized.

4.1.12 Winches shall be provided with reduction gearbox, drums, manual brake, controlled brake and, if required, mechanical actuators.

4.1.13 Winches shall be designed to handle the working load (see 3.7).

4.1.14 Winches shall be designed to allow the lifeboat to be dropped either fully loaded or unloaded, without any means other than gravity or accumulated mechanical power, independently of the ship’s power generation.

4.1.15 The diameter of the winch drum shall be at least 16 times greater than the wire rope diameter.

Note: the rate drum x wire rope is based on the use of steel cables 6 x 37 + AF according to standard NBR 6890. Other types may be used provided the drum is suitably designed.

4.1.16 Winch drum shall be provided with flanges to avoid the ropes to unreel. The distance between the last layer and the edge of the drum flange shall be at least 1.5 times greater than the diameter of the wire rope.

4.1.17 The drum shall be able to store in a maximum of 3 layers, the wire rope length required to drop the lifeboat from its storage location to the sea level, keeping 3 turns still remaining in the drum. This shall happen with the vessel under a list of 20 deg. and trim of 10 deg. to the opposite side.

4.1.18 The rope angles (see 3.10) shall be the following, according to the drum type:

a) slick drum: equal or less than 3 deg.

b) grooved drum: equal or less than 5 deg.

4.1.19 The release control brake shall automatically control the lowering speed of fully loaded boat up to it reaching the sea level (see 5).

4.1.20 The manual brake shall have a counterweight suitable to interrupt the release of the fully loaded boat without any additional effort from the operator. The system shall be designed to allow the operation by just one operator on the deck of the vessel or inside the lifeboat.

Note: The lifeboat shall be visible to the operator on the deck during the operation.



4.1.21 The brake pads shall be protected against water, oil or other substance that could affect the operation of the winch.

4.1.22 The manual lifting system shall be capable of lifting a manned lifeboat by means of a crank handle, each operator applying only 147 N each.

Notes: a) the maximum radius of the crank handle is 400 mm;

b) the manual system shall be operated with a maximum of 2 operators per crank handle.

4.1.23 The winch shall be designed to avoid the crank handle to turn during the lifting or dropping of the lifeboat, by motor or gravity respectively.

4.1.24 Motorized winch shall be design in a way that the motor will not work when releasing the lifeboat, except if it is provided with a speed correspondent to the maximum lowering speed.

4.1.25 The lifting speed of the lifeboat on motorized winches shall be 0.5 m/s minimum.

4.1.26 The lifting system on motorized winches shall have a limiting device suitable for interrupting the power supply to the winch at approximately 150 mm from the storage position.

4.2 Identification

Davits and winches shall be provided with the following identification:

a) manufacturer’s name;

b) model or type;

c) serial number;

d) working load for davit and winch;

e) test load;

f) lifting height;

g) date;

h) number of the inspection agency certificate;

i) number and year of this standard.

4.3 Information to be supplied by buyer

Buyer shall provide the following information:

a) number of crew members;

b) number of passengers;

c) breadth, distance between hooks, depth and weight of lifeboat;

d) height of installation;

e) type of actuation;

f) Boat Deck Arrangement.




5. Specific Conditions

5.1 Minimum lowering speed

The minimum lowering speed of the lifeboat shall be equal to:

S = 0.4 + (0.02 H)

Being:

S = minimum lowering speed in m/sec

H = distance between upper side of davit arm and the water line calculated with light ship, in meters.

5.2 Maximum lowering speed

The maximum lowering speed shall be 1.2 m/sec.

6. Acceptance and Rejection

Davits and winches not satisfying the requirements of this specification shall be rejected.

nbr 10728 boat davits

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