Section 4 Gas detection
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Naval Ships, January 2023 - Volume 2 Machinery and Engineering Systems - Part 9 Electrotechnical Systems - Chapter 11 Gas detection - Section 4 Gas detection

Section 4 Gas detection

Parent topic: Chapter 11 Gas detection

4.1 General

4.1.1 An efficient gas detection system, suitable for the gases and/or vapours anticipated, is to be provided for all spaces which are identified as potentially containing flammable, poisonous, toxic/corrosive, asphyxiant or irritant gases in concentrations which may exceed a predetermined hazardous limit during normal operation or in the event of a reasonably foreseeable failure. Where the potential for oxygen depletion is also identified, the measurement of oxygen levels in the spaces may also be required.

4.1.2 Spaces where a gas detection system may be required include but are not limited to:
  1. low flashpoint fuel storage and handling spaces;
  2. waste oil and oily water handling areas;
  3. spaces containing emissions abatement equipment;
  4. refrigeration plant rooms;
  5. sewage treatment plant rooms;
  6. waste treatment and storage rooms;
  7. chemical storage areas;
  8. compressed gas storage areas;
  9. energy storage system compartments.

4.2 Design and construction

4.2.1 Gas detection equipment is to be designed, installed and tested in accordance with a relevant International or National Standard acceptable to Lloyd’s Register (hereinafter referred to as ‘LR’).

4.2.2 Gas detection equipment is to consist of a permanently fixed installation and at least two sets of portable equipment suitable for the chemical compositions anticipated.

4.2.3 Fixed gas detection systems are to comply with Vol 2, Pt 9, Ch 7, 4.3 Alarm systems, general requirements, general requirements and where they are also capable of automatically activating safety shutdown functions are to comply with Vol 2, Pt 9, Ch 8 Programmable Electronic Systems.

4.2.4 The position and number of sampling points is to be determined with due regard to the density of the gases and/or vapours of the substances anticipated, and the dilution resulting from compartment ventilation. In each case, a sufficient number of sampling points is to be provided to give efficient sampling to maintain a safe environment. Common sampling lines to the detection equipment are not to be fitted.

4.2.5 Gas analysing units may be located outside the spaces served provided that:
  1. sampling lines do not pass through ‘gas-safe’ spaces, except where permitted by Vol 2, Pt 9, Ch 11, 4.2 Design and construction 4.2.5.(f);
  2. the gas sampling pipes serving spaces potentially containing flammable gasses are to be fitted with flame arresters.
  3. sample gas is to be led to the atmosphere with outlets arranged in a safe location, in the open atmosphere;
  4. bulkhead penetrations of sample pipes between safe and dangerous areas are of an approved type. A manual isolating valve is to be fitted in each of the sampling lines at the bulkhead in the safe area;
  5. the gas detection equipment including sampling piping, sampling pumps, solenoid valves and analyzing units, are located in a fully enclosed steel cabinet, with a gasketed door, monitored by its own sampling point. At gas concentrations above a predetermined limit inside the steel cabinet, the entire gas-analyzing unit is to be automatically shut-down; and
  6. sample pipes passing through gas safe spaces are to be of steel or other equivalent material and without detachable piping connections, except for the connection points for isolating valves at the bulkhead and analyzing units. The sample pipes are to be led by their shortest route.

4.2.6 Where continuous sampling is not required, the gas detection equipment is to be capable of sampling and analysing from each sampling point within a single space at agreed intervals, which are in no case to exceed 30 minutes.

4.2.7 Fixed gas detection systems are to provide indication of gas concentration levels and give audible and visible alarms when these exceed a predetermined limit, both at a continually attended control station and within the space, or adjacent to the access for normally unoccupied spaces.

4.2.8 Gas concentration alarm limits are to be selected in accordance with an appropriate national or international standard.

4.2.9 The gas detection equipment is to be designed so that it may be readily and regularly tested and calibrated. Suitable equipment and span gas is to be provided for this purpose. In addition, regular checking procedures with portable equipment are to be provided, particularly for closed or unmanned spaces. Permanent connections for such test equipment shall be fitted.

4.2.10 Where fixed equipment for detecting the specific flammable, poisonous, toxic/corrosive, asphyxiant or irritant gases which may be present in the space cannot be provided, full details of alternative arrangements and an engineering safety and justification report in accordance with Vol 2, Pt 9, Ch 11, 3.1 General are to be submitted.

4.3 Installation

4.3.1 The gas detection system is to be examined and tested to ensure that it has been installed in compliance with its certification, and that the integrity of boundaries has been maintained.

4.3.2 Alerts and indicators associated with the gas detection system are to be tested for correct operation.

4.3.3 Spaces which are identified as potentially containing flammable, poisonous, toxic/corrosive, asphyxiant or irritant gases shall be marked to alert those entering to the nature of the potential hazards. Where applicable, the equipment which will potentially release such gasses is also to be marked.

Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.