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Performance standards for the power and propulsion systems of ships

MLC Noise and Vibration

Unlike most other equipment on board vessels, as things stand there are no performance standards or guidelines for the power and propulsion systems beyond vague references to flag states’ requirements and a reference in the SOLAS regulation that calls for interim and special surveys to ensure the main machinery is in a satisfactory condition and fit for purpose.

From an operator’s point of view, engines, propulsion and steering arrangements – regardless of type – are all considered essential systems and therefore will feature in just about all approved ISM Code safety systems, adding another layer to any regulatory requirement for operation and maintenance. On the safety side, the fuel delivery to the engine may be controlled under SOLAS and, as a source for potential fire and explosions, the engine room will need fire protection and extinguishing systems.

The engine room is not a comfortable place to work but under the Maritime Labour Convention (MLC), which became effective in August 2013, noise and vibration are issues that all affected ships must take measures to control, both in accommodation and working areas. In July 2014, new SOLAS rules came into effect. These follow from the 91st meeting of IMO’s Maritime Safety Committee (MSC 91) in November 2012 when the IMO adopted a new SOLAS regulation II-1/3-12 to require new ships to be constructed to reduce on-board noise and to protect personnel from noise.

The new limits are in accordance with the revised Code on Noise Levels Onboard Ships, (RESOLUTION MSC.337(91) ) which sets out mandatory maximum noise level limits for machinery spaces, control rooms, workshops, accommodation and other spaces. The code supersedes the previous non-mandatory code, adopted in 1981 by resolution A.468(XII). It applies to all vessels of 1,600gt or more which:

  • are built under a contract signed after 1 July 2014;
  • with the keel laid after 1 January 2015;
  • have a delivery date on or after 1 July 2018.

Within the code, maximum noise levels are set for different areas of the ship and there are detailed instructions for measuring noise which include the distance at which measurements should be taken.

In machinery spaces the limit for noise levels in dB(A) is set at 110, in machinery control rooms it is 75 and for workshops and other non-specified spaces at 85.

In spaces with sound pressure levels exceeding 85 dB(A), suitable hearing protection should be used, or time limits set for exposure. ensure that an equivalent level of protection is maintained. The code also requires ship operators to include in their Safety Management System a section on the company’s policy regarding hearing protection, exposure limits and conduct training on those matters, which will be logged in their training records. It also says consideration should be given to the instruction of seafarers on these aspects.

Hearing protection should be provided by the shipowner and as well as including a policy in the company SMS, the owner is also expected to take concrete steps to ensure hearing protection is worn.

Where the noise level in machinery spaces (or other spaces) is greater than 85 dB(A), entrances to such spaces must carry a warning notice comprising symbol and supplementary

sign in the working language of the ship. If only a minor portion of the space has such noise levels the particular location(s) or equipment must be identified at eye level, visible from each direction of access.

The messages that must be displayed should (in the language of the ship) convey the following information


Vibration is also regulated in ships under the MLC but only in accommodation spaces. With regard to machinery, most class societies’ rules address this and have recommendations for methods of reducing vibration. Unusual vibrations are usually a sign of some equipment failure or a prelude to failure. Such vibrations should always be investigated and appropriate action taken.

Monitoring emissions

NOx emissions

Tier III, the last of the deadlines under the IMO NOx regulations came into effect in 2016 but new ECAs are still on the cards, extending rules to newbuildings at different rates.

The requirements of the NOx Code are the only emission regulations in which the engine itself rather than the fuel or ancillary systems can be a controlling factor. Under the code, all vessels built since 2000 must have a Technical File that identifies the engine’s components, settings or operating values that influence exhaust emissions.

The file is prepared by the engine maker and approved by the flag state. It must be retained onboard for the whole life of the engine and will be used to ensure compliance.

The engine to which the Technical File refers is to be installed in accordance with the rating (kW and speed) and duty cycle as approved, together with any limitation imposed by the Technical File. The Technical File must, at a minimum, contain the following information:

  • Identification of components, settings and operating values of the engine which influence its NOx emissions;
  • Identification of the full range of allowable adjustments or alternatives for the components of the engine;
  • A full record of the engine’s performance, including its rated speed and rated power;
  • A system of onboard NOx verification procedures to verify compliance with the NOx emission limits during onboard verification surveys;
  • A copy of the test report for an engine tested for pre-certification or a test report for an engine installed onboard ship without pre-certification;
  • If applicable, the designation and restrictions for an engine which is a member of an engine group or engine family;
  • Specifications of those spare parts and components which, when used in the engine, according to those specifications, will result in continued compliance of the engine with the NOx emission limits;
  • The Engine International Air Pollution Prevention Certificate (EIAPP).

Compliance with the NOx code can be achieved using one of three options alone or in combination. The first option is to run the engine always within the parameters as laid down in the technical file and to use only OEM spare parts when any component identified in the technical file requires replacement.

The second is to install a continuous monitoring system of the type offered by manufacturers such as Kittiwake, Martek Marine, Green Instruments and Norsk Analyse, among others. Some of these systems can measure other exhaust gases and might be able to provide evidence of compliance with other regulations such as SOx emissions limits in SECAs or in ports where low-sulphur fuel is mandated.

The third option requires the engine to be tested at regular intervals by approved service providers. All engine types and power configurations are affected by these regulations although engines running on LNG and some of the latest alternatives such as methanol or ethane do not produce SOx.

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