Section 7 Piping

7.1.1 The design and construction of piping shall be in accordance with Rules for Ships, Pt 5, Ch 12 Piping Design Requirements, Rules for Carriage of Liquid Chemicals in Bulk, Ch 5 Process Pressure Vessels and Liquid, Vapour and Pressure Piping Systems as applicable and these Rules. Piping material selection shall consider the system design pressure and temperature.

7.1.2 A Fatigue analysis shall be conducted for all pressurised piping arrangements subject to vibration or pulsating pressure, where failure of the pipe or its connection or a component could result in a safety hazard, e.g. fire. The analysis shall recognise the pressures and fluctuating stresses that the piping system may be subject to in normal service.

7.2.1 Piping connections shall be reduced to the minimum required for installation and machinery maintenance. All piping shall be suitably and adequately supported so as to avoid, as far as is practicable, vibration that could lead to fatigue failure.

7.2.2 All valves and expansion joints used in pressurised fuel piping shall be of an approved type and suitable for the intended service.

7.2.3 Joints on the entire length of the fuel piping shall be butt-welded with full penetration and a minimum of 10 per cent of the piping system shall be fully radiographed, except where alternative means of NDE are approved by LR. Radiography of the piping shall be extended to 100 per cent where defects are detected.

7.2.4 Fuel pipe joints other than welded joints at the locations approved by LR shall comply with an appropriate standard recognised by LR, or with those joints whose structural strength has been verified through tests and analysis to the satisfactory requirements of LR.

7.2.5 Welding procedures shall be established for welding of pressurised fuel piping and submitted to LR for approval as detailed in the LR Rules for Materials. Suitable post-weld heat treatment shall be performed where indicated in the approval.

7.2.6 Fuel piping shall be clearly identifiable by means of a suitable colour code based on a recognised Standard, e.g. EN ISO 14726:2008 Ships and marine technology - Identification colours for the content of piping systems.

7.2.7 Piping installed shall be suitably located and protected from corrosion and from impact, such as from collision, grounding and dropped objects.

7.2.8 The wall thickness of fuel piping is not to be less than that given by the requirements of the LR Rules for Carriage of Liquid Chemicals in Bulk Ch 1, 5.1 Piping scantlings.

7.2.9 The design pressure for any section of the fuel piping system is the maximum gauge pressure to which the system may be subjected in service, taking into account the highest set pressure on any relief valve on the system.

7.2.10 Fuel piping systems shall have sufficient strength to accommodate stresses due to the weight of the piping system, acceleration loads (if significant), and internal pressure and loads induced by hog and sag of the ship, see Rules for Ships,Pt 3, Ch 4 Longitudinal Strength.

7.2.11 All piping and components containing fuel that may be isolated shall be provided with relief valves.

7.2.12 Piping into the fuel storage tank, fittings, flanges, valves or other equipment in the tank space shall be minimised."

7.2.13 Fuel piping is not to be located less than 800 mm from the ship’s side.

7.2.14 Fuel piping shall be entirely separate from other piping systems and is not to pass through accommodation, service spaces and control stations.

7.2.15 Fuel piping within a machinery space shall comply with the applicable requirements in Ch 1, 7.2 Piping design 7.2.16. Alternative arrangements to those stated in Ch 1, 7.2 Piping design 7.2.17 and Ch 1, 7.2 Piping design 7.2.18 will be considered where an equivalent level of safety for personnel, equipment and the ship can be demonstrated.

7.2.16 All fuel supply piping within enclosed spaces, including machinery spaces, shall be enclosed in a secondary gastight and liquid-tight enclosure of the following type:

1. double-walled piping or ventilated ducting provided with forced draught ventilation, see Ch 1, 7.2 Piping design 7.2.18;

2. double-walled piping with the annular space between pipes pressurised with inert gas, see Ch 1, 7.2 Piping design 7.2.17; or

3. cofferdam, see Ch 1, 6.4 Cofferdams .

7.2.17 Where fuel piping is a double-walled piping system with the fuel contained in the inner pipe, and the annular space between pipes is pressurised with inert gas, the following requirements shall be satisfied:"

1. "the annular space between pipes shall be pressurised with inert gas to a pressure greater than the fuel pressure;"

2. alarms shall be provided to indicate loss of pressure between the pipes;

3. the pressure in the annular space shall be monitored continuously and, before the pressure falls below the inner pipe pressure, the master fuel valve specified in Ch 1, 6.5 Methanol supply system 6.5.1 shall be arranged to close;

4. construction and strength of the outer pipes shall be based on the design pressure of the inert gas or the most onerous inner pipe leakage whichever is higher.

7.2.18 Where the fuel piping is installed within a gastight double-walled pipe or ventilated gastight ducting with forced draught ventilation, the following requirements shall be satisfied:

1. the air space between the fuel piping and the duct inner wall shall be provided with mechanical ventilation having a capacity that takes into account the construction and arrangement of protective pipes or ducts and shall ensure at least 30 air changes per hour;

2. ventilation shall maintain a pressure less than the atmospheric pressure. The fan motors shall be placed outside the ventilated pipe or duct;

3. ventilation outlets shall be located to discharge at least 3 m above deck and 3 m away from the nearest air intakes or openings to accommodation and enclosed working spaces, and from possible sources of ignition;

4. ventilation intakes shall be located in non-hazardous area and be provided with automatic non-return devices that prevent the escape of methanol or alternatively, a vapour detector shall be fitted at each air intake;

5. ventilation shall be arranged to be in operation whenever there is fuel in the piping;

6. continuous vapour detection shall be arranged in the ventilation system to provide an indication at the machinery control station of leaks and to shut down the fuel supply to the machinery space in accordance with Ch 1, 8.4 Methanol vapour detection 8.4.12;

7. the master fuel valve required by Ch 1, 6.5 Methanol supply system 6.5.1 shall be arranged to close automatically if the required airflow is not established and maintained by the exhaust ventilation system;

8. the materials, construction and strength of outer protection pipes or ducts and the mechanical ventilation systems shall be capable of withstanding the sudden emission and expansion of pressurised methanol in the event of failure of an inner methanol pipe;

9. the number of flange joints of outer protective pipes or ducts shall be minimised;

10. the outer protection piping or ducting shall be pressure-tested to the maximum working pressure of the inner pipe;

11. ventilation performance required by this Section shall be maintained at all expected temperatures and environmental conditions as defined in the Design Statement, see Ch 1, 2.1 Documentation required for design review 2.1.1.

7.2.19 Where fuel is contained in double-walled piping or piping within ducting, the outer barrier shall remain gas- and liquid-tight in the event of leakage of the primary pipe taking into consideration the impingement force and the effects of pressurised expansion.

7.2.20 The annular space of double-walled piping or piping within ducting shall be fitted with a means of providing liquid leak detection from the inner pipe. This may comprise drainage to a tank that is fitted with liquid level detection, see Ch 1, 8 Control, alert and safety systems . This tank shall be separate from the bilge holding tanks referred to in Ch 1, 7.3 Drainage arrangements and the space in which it is located shall be considered hazardous, see also Ch 1, 7.3 Drainage arrangements 7.3.5.

7.2.21 The annular space of double-walled piping or piping within ducting shall be fitted with drains leading to the bilge holding tanks referred to in Ch 1, 7.3 Drainage arrangements. These drains shall be fitted with valves that open automatically on detection of leakage, see Ch 1, 7.2 Piping design 7.2.20 and Table 1.8.1 Methanol fuel supply and storage: Alarms, monitoring and safeguards.

7.2.22 The slope of pipes and the number and position of drain points shall be such that fuel can be efficiently drained from any portion of the piping system, taking into consideration the requirements of the Rules for Ships, Pt 5, Ch 1, 3.6 Ambient operating conditions and Ch 1, 3.7 Bunkering safety study.

7.3.1 Drip trays shall be provided to manage leakages and spills of fuel.

7.3.2 Each drip tray that is located in an enclosed space shall be fitted with a drain valve to enable drainage to a dedicated bilge holding tank.

7.3.3 One or more bilge holding tanks for collecting drainage and any possible leakage of fuel from pumps, valves and from double-walled pipes and ducts located in enclosed spaces shall be provided.

7.3.4 Bilge holding tanks shall meet the relevant requirements of Ch 1, 6.3 Fuel storage tanks.

7.3.5 The area in which the bilge holding tank(s) is located shall be considered hazardous. Alternative arrangements (e.g. dilution of the methanol to maintain the solution below its lower flammable limit) may be accepted where supported in the risk-based studies, see Ch 1, 3 Risk-based studies.

7.3.6 The bilge system serving the fuel pump room shall be operable from outside the fuel pump room.

7.3.7 Drip trays and coamings shall have sufficient capacity to accommodate the maximum credible spill of fuel identified by the risk-based studies. The maximum credible spill scenario is to be determined and agreed with LR.

7.3.8 Bilge holding tanks shall have sufficient capacity to accommodate the maximum credible leakage of fuel identified by the risk-based studies. The maximum credible leakage scenario is to be determined and agreed with LR.

7.3.9 A shore connection with a standard coupling or other facilities shall be provided for transferring contaminated fuel to onshore reception facilities.

7.3.10 Bilge holding tanks shall be provided with inerting arrangements as detailed in Ch 1, 6.8 Inert gas system.

7.3.11 Arrangements for managing leakages shall be capable of fulfilling their function under the operating conditions defined in Rules for Ships,Pt 5, Ch 1, 3 Operating conditions.