IMO has adopted Resolution MSC.188(79) revising the performance standards for water level detectors

The International Maritime Organization has adopted Resolution MSC.188(79)/Rev.2: Revised Performance Standards for Water Level Detectors on Ships Subject to SOLAS Regulations II-1/25, II-1/25-1 and XII/12.

This resolution will enter into force on 1 January 2024.

The Maritime Safety Committee, recalling Article 28(b) of the Convention on the International Maritime Organization concerning the functions of the Committee, also recalling resolution MSC.134(76), by which it, at its seventy-sixth session, adopted amendments to chapter XII of the International Convention for the Safety of Life at Sea (SOLAS), 1974, inter alia introducing new regulation 12 requiring the installation of water level detectors for hold, ballast, and dry spaces,

Further recalling resolution MSC.194(80), by which it, at its eightieth session, adopted amendments to chapter II-1 of the 1974 SOLAS Convention, introducing new regulation 23-3 requiring the installation of water level detectors on single hold cargo ships other than bulk carriers,

Additionally, recalling resolution MSC.482(103), by which it, at its 103rd session, adopted amendments to chapter II-1 of the 1974 SOLAS Convention, introducing new regulation 25-1 requiring the installation of water level detectors on multiple hold cargo ships other than bulk carriers and tankers, which is expected to enter into force on 1 January 2024,

Recognizing that performance standards against which the operation and efficiency of water level detectors can be measured should be made available in good time before the above entry-into-force date,

Also recognizing the need to ensure that the required water level detectors operate reliably and that, to that extent, they are appropriately tested and installed,

Having considered, at its 105th session, the recommendations made by the Sub-Committee on Ship Design and Construction, at its eighth session,

Having also considered, at its 107th session, the recommendations made by the Sub-Committee on Ship Design and Construction, at its ninth session,

Adopts the Revised performance standards for water level detectors on ships subject to SOLAS regulations II-1/25, II-1/25-1, and XII/12 and the appended Guidelines on installation and testing of water level detection systems for ships subject to SOLAS regulations II-1/25, II-1/25-1, and XII/12, as set out in the annex to the present resolution;

Urges Governments to ensure that the annexed Revised performance standards and appended Guidelines are applied when water level detectors are installed on ships flying their flags, in compliance with SOLAS regulations II-1/25, II-1/25-1, and XII/12, as appropriate.

Recommendation

Governments should ensure that water level detectors meet the performance standards specified in the annex to this resolution.

This applies to the detectors installed on the following:

• (a) New ships, where the building contract is placed on or after 1 January 2024, or if there's no contract, the keel is laid, or the ships are at a similar stage of construction on or after 1 January 2024.
• (b) Ships other than those mentioned in (a), with a contractual delivery date for the equipment to the ship on or after 1 January 2024, or if there's no contractual delivery date, the equipment should be actually delivered to the ship on or after 1 January 2024.

If the detectors are installed on ships other than those specified above, they should still conform to performance standards not inferior to those specified in the annex to resolution MSC.188(79).

Annex: Performance standards

PURPOSE

1.1 These standards provide technical functional requirements for water level detection and alarm arrangements installed in:

• .1 bulk carriers for compliance with SOLAS regulation XII/12;
• .2 single hold cargo ships other than bulk carriers for compliance with SOLAS regulation II-1/25; and
• .3 multiple hold cargo ships other than bulk carriers and tankers for compliance with SOLAS regulation II-1/25-1.

1.2 They also provide technical functional requirements for bilge alarms used as water level detectors in multiple hold cargo ships for compliance with SOLAS regulation II-1/25-1.

DEFINITIONS

2.1 Water level detector means a system comprising sensors and alarms that detect and warn of water ingress in cargo holds and other spaces as required in SOLAS regulations II-1/25, II-1/25-1, or XII/12.1.

2.2 Sensor means a unit fitted at the location being monitored that activates a signal to identify the presence of water at the location.

2.3 Pre-alarm level means the lower level at which the sensor(s) in the cargo hold space will operate.

2.4 Main alarm level means the higher level at which the sensor(s) in the cargo hold space will operate or the sole level in spaces other than cargo holds.

2.5 Visual indication means indication by activation of a light or another device that is visible to the human eye in all levels of light or dark at the location where it is situated.

2.6 Audible indication means an audible signal that is detectable at the location where it is signaled.

FUNCTIONAL REQUIREMENTS

3.1 Means of detecting the water level

3.1.1 The method of detecting the water level may be by direct or indirect means as defined below:

• .1 A direct means of detection determines the presence of water by physical contact with the water with the detection device.
• .2 Indirect means of detection includes devices without physical contact with the water.

3.1.2 The sensors must be positionable either in the aft section of the cargo hold or above its lowest point in ships with an inner bottom not parallel to the designed waterline. Alternatively, in the case of bulk carriers complying with SOLAS regulation XII/12, the sensors can be placed in the aft part of each cargo hold or in the lowest part of other spaces to which the regulation applies.

3.1.3 The water level detection systems must be operational continuously while the ship is at sea.

3.2 Detector system requirements:

3.2.1 The detector systems should provide a dependable indication when the water reaches a predetermined level.

3.2.2 The system must offer the following features:

For cargo holds:

• .1 When the water depth in the monitored space reaches the pre-alarm level, an audible and visual alarm should activate, identifying the specific space.
• .2 An audible and visual alarm should activate when the water depth in a cargo hold reaches the main alarm level, indicating an increasing water level. The alarm should identify the space and have distinct characteristics from the pre-alarm level.

For compartments other than cargo holds:

• .3 An audible and visual alarm should activate when the water is present in a compartment other than a cargo hold, and the water level in the monitored space reaches the sensor. The alarm characteristics should match those of the main alarm level in a hold space.

3.2.3 The detection equipment must have suitable corrosion resistance for all intended cargoes.

3.2.4 The water level detector should be capable of activating with an accuracy of ±100 mm.

3.2.5 The detection equipment must be of a certified safe type suitable for the intended cargoes. The section of the system containing circuitry in the cargo area should be intrinsically safe or explosion-proof, with appropriate apparatus group and temperature class, determined based on the carried cargo.

3.3 Alarm system requirements:

3.3.1 The visual and audible alarms should be suitable for installation on the navigation bridge.*

*Reference is made to the requirements of SOLAS regulations V/17 and V/18.

3.3.2 The visual and audible alarms must comply with the Code on Alerts and Indicators, 2009, as applicable to a primary alarm for the ship's preservation or safety, subject to amendments.

3.3.3 The visual and audible alarms should be capable of the following:

• .1 Visual indication using a light of a distinct color or digital display that is clearly visible in all expected light levels, which does not seriously interfere with other activities necessary for the safe operation of the ship. The visual indication should be capable of remaining visible until the condition activating it has returned below the level of the relevant sensor. The visual indication should not be capable of being extinguished by the operator.
• .2 In conjunction with the visual indication for the same sensor, the system should be capable of providing audible indication and alarms in the space in which the indicator is situated. The audible indication should be capable of being muted by the operator.

3.3.4 Time delays may be incorporated into the alarm system to prevent spurious alarms due to sloshing effects associated with ship motions.

3.3.5 An alarm overriding device may be installed for water level detectors in cargo holds or tanks which can be used for water ballast (SOLAS regulations II-1/25-1 and XII/12.1). An override visual indication capability should be provided throughout the deactivation of the water level detector for such holds or tanks. Where such an override capability is provided, cancellation of the override condition and reactivation of the alarm should automatically occur after the hold or tank has been de-ballasted to a level below the lowest alarm indicator level.

3.3.6 Requirements for malfunctions, alarms, and indications should include a facility for continuous monitoring of the system which, on detecting a fault, activates a visual and audible alarm. The audible alarm should be capable of being muted, but the visual indication should remain active until the malfunction is cleared.

3.3.7 The water level detector system should be capable of being supplied with electrical power from two independent electrical supplies. Failure of any of the two electrical power supplies should be indicated by an alarm.

3.4 Testing

3.4.1 Water level detector systems should be type-tested to demonstrate their robustness and suitability under the appropriate internationally recognized conditions and for their continued functioning under the expected service temperature.**

**With regard to testing, reference is made to IEC 60092-504 and IEC 60529. Electrical components installed in cargo holds, ballast tanks and dry spaces should satisfy the requirements of IP68 in accordance with IEC 60529.

3.4.2 Detectors serving a cargo hold should be capable of being functionally tested, in situ, when the hold is empty using either direct or indirect methods.

3.5 Manuals

Documented operating and maintenance procedures for the water level detection system should be kept on board and be readily accessible.

INSTALLATION AND TESTING

Guidelines on installation and testing of water level detection systems for ships subject to SOLAS regulations II-1/25, II-1/25-1, and XII/12 are set out in the appendix.

BILGE ALARMS USED AS WATER LEVEL DETECTORS

5.1 Bilge alarms may be used as water level detectors provided that they meet the functional requirements and installation and testing requirements set out in sections 3 and 4.

5.2 Some cargoes require the bilge pumping system to be protected to prevent the spread of contaminated or potentially dangerous fluids.

5.3 Where the cargo hold bilge well will be completely sealed when specific cargoes are carried, and the bilge well, therefore, cannot be used for the entry of ingress water to the detector(s), a suitable alternative detection point or points are to be provided.

5.4 If the bilge well is used for when specific cargoes are carried, the bilge well is not to be completely sealed in order to allow water ingress for activating the detectors.

PERIODIC TESTING

Water level detectors should be periodically tested on board to the same extent as specified in section 3.3 of the appendix, and records of the periodic testing should be retained on board.

Appendix: Guidelines on installation and testing

PURPOSE

1.1 These Guidelines provide procedures for installation and testing of water level detection and alarm systems installed in:

• .1 bulk carriers for compliance with SOLAS regulation XII/12;
• .2 single hold cargo ships other than bulk carriers for compliance with SOLAS regulation II-1/25; and
• .3 multiple hold cargo ships other than bulk carriers and tankers for compliance with SOLAS regulation II-1/25-1.

1.2 They also provide procedures for installation and testing of bilge alarms used as water level detectors in multiple hold cargo ships other than bulk carriers and tankers for compliance with SOLAS regulation II-1/25-1.

EQUIPMENT

2.1 Detector equipment type test requirements

2.1.1 Detector equipment should provide a reliable indication of water reaching a preset level and should be type tested to demonstrate their robustness and suitability under the appropriate conditions of IEC 60092-504 and the following:

• .1 Protection of the enclosures of electrical components installed in the cargo holds, ballast tanks, and dry spaces should satisfy the requirements of IP68 in accordance with IEC 60529. The water pressure testing of the enclosure should be based on a pressure head held for a period depending on the application. For detectors to be fitted in holds intended for the carriage of water ballast or ballast tanks, the application head should be the hold or tank depth, and the hold period should be 20 days. For detectors to be fitted in spaces intended to be dry, the application head should be the depth of the space, and the hold period should be 24 h.
• .2 Operation in cargo/water mixture for a selected range of cargo groups such as iron ore dust, coal dust, grains, and oils using seawater with a suspension of representative fine material for each cargo group. For type test purposes, an agitated suspension of representative fine materials in seawater, with a concentration of 50% by weight, should be used with the complete detector assembly, including any filtration fitted. The functioning of the detection assembly with any filtration arrangements should be verified in the cargo/water mixture with immersion repeated 10 times without cleaning any filtration arrangements.

2.1.2 Protection of the enclosures of electrical equipment located on the deck above ballast and cargo spaces should satisfy the requirements of IP56 in accordance with IEC 60529.

2.1.3 Equipment which is to be used in refrigerated cargo spaces should satisfy the requirements of a suitable industry standard covering the relevant service temperatures.

2.2 Detector equipment installation requirements

2.2.1 The sensors should be located in a protected position that is in communication with the specified part of the cargo hold (usually the aft part) such that the position of the sensor detects the level that is representative of the levels in the actual hold space. These sensors should be located:

• .1 either as close to the centerline as practicable, or
• .2 at both the port and starboard sides of the cargo hold.

2.2.2 The sensors should be located at the height specified in the regulations. These heights are to be measured from the upper surface of the inner bottom.

2.2.2.1 For bilge level sensors in SOLAS regulation II-1/25-1.3, if the bottom of the bilge well is below the upper surface of the inner bottom, the heights of those sensors are to be measured from the bottom of the bilge well.

2.2.3 When a lining or insulation is fitted, if the lining or insulation is not constructed to a watertight standard, then the height is to be measured from the upper surface of the inner bottom. If the lining or insulation is tested as watertight, then the heights may be measured from the upper surface of the lining/insulation.

2.2.4 The detector installation should not inhibit the use of any sounding pipe or other water level gauging device for cargo holds or other spaces.

2.2.5 Detectors and equipment should be installed where they are accessible for survey, maintenance, and repair.

2.2.6 Any filter element fitted to detectors should be capable of being cleaned before loading.

2.2.7 Sensors, electrical cables, and any associated equipment installed in cargo holds should be protected from damage by cargoes or mechanical handling equipment associated with bulk carrier operations, such as in tubes of robust construction or in similar protected locations.

2.2.8 Any changes/modifications to the ship's structure, electrical systems, or piping systems that involve cutting and/or welding should be approved by the classification society before work is carried out.

SYSTEMS

3.1 Alarm system requirements

3.1.1 Alarm systems should be type tested in accordance with IEC 60092-504, as appropriate.

3.1.2 A switch for testing audible and visual alarms should be provided at the alarm panel, and the switch should return to the off position when not operated.

3.2 Alarm system testing requirements

The visual and audible alarms should be tested to demonstrate the following:

• .1 The visual indication may not be extinguished by the operator;
• .2 They should be set at a level that alerts operators but does not interfere with the safe operation of the ship; and
• .3 They should be distinguishable from other alarms.

3.3 System test requirements

3.3.1 After installation, a functionality test should be carried out. The test should represent the presence of water at the detectors for every level monitored. Simulation methods may be used where the direct use of water is impracticable.

3.3.2 Each detector alarm should be tested to verify that the pre-alarm and main alarm levels operate for every space where they are installed and indicate correctly. Also, the fault monitoring arrangements should be tested as far as practicable.

3.3.3 Records of testing of alarm systems should be retained on board.

MANUALS

4.1 Manuals should be provided on board and should contain the following information and operational instructions:

• .1 A description of the equipment for detection and alarm arrangements together with a listing of procedures for checking that, as far as practicable, each item of equipment is working properly during any stage of ship operation;
• .2 Evidence that the equipment has been type tested to the requirements of 2.1 above;
• .3 Line diagrams of the detection and alarm system showing the positions of equipment;
• .4 Installation instructions for orientation, setting, securing, protecting, and testing;
• .5 List of cargo groups for which the detector is suitable for operating in a 50% seawater slurry mixture (see 2.1.1.2);
• .6 Temperature range for which the equipment is suitable;
• .7 Procedures to be followed in the event of equipment not functioning correctly; and
• .8 Maintenance requirements for equipment and system.

4.2 Manuals for bilge alarm systems used as water level detection systems are to contain the following information in addition to that in 4.1 (see paragraph 5.3 of these performance standards):

• .1 Procedure for switching to the alternative arrangements provided for occasions when the bilge alarm system cannot be used as a water level detection system; and

- .2 List of cargoes for which alternative provisions are to be used.

MSC.188(79)/Rev.2 has been adopted on 8 June 2023 and cancels resolution MSC.188(79)/Rev.1.

For more information, please see the document below (available only to subscribers):

Revised Performance Standards for Water Level Detectors on Ships Subject to SOLAS Regulations II-1/25, II-1/25-1 and XII/12