Chapter 2 – Piping System

 For the application of these Guidelines, flammable oil systems are classified as follows:

• .1 high pressure oil system:

  • – a piping system which services or transfers flammable oils having pressures of 10.0 N/mm² or above; and

• .2 low pressure oil system:

  • – a piping system which services or transfers flammable oils having pressures between 0.18 N/mm² and 10.0 N/mm^2.

 If oil fuel lines fail, spray patterns may occur. These spray patterns depend on the pressure of the system and the failure condition. Major factors of flammability are air/fuel mixture ratio, temperature of fuel and droplet size. Droplet diameter is one of the factors and is dependent on fluid pressure and size of failure. As a general rule, the smaller the droplet size the greater the fire risk when the fuel system is under high pressure and a small orifice exists, as this results in the atomization of the fuel oil. Therefore, a small crack in a high-pressure oil fuel pipe may lead to a most dangerous situation.

 Flexible pipes, hoses and hose assemblies – which are flexible hoses with end fittings attached – should be in as short lengths as practicable, but should not, in general, exceed 1.5 m in length, and only be used where necessary to accommodate relative movement between fixed piping and machinery parts.

 Hoses should be constructed to a recognized standard and be approved as suitable for the intended service, taking into account fire resistance, pressure, temperature, fluid compatibility and mechanical loading including impulse where applicable. Each type of hose assembly should be provided with a certificate of hydrostatic pressure testing and conformity of production.

 Hoses should be installed in accordance with the manufacturers’ instructions, having regard to: minimum bend radius, twist angle and orientation, and support where necessary. In locations where hoses could possibly suffer external damage, adequate protection should be provided. After installation, the system should be operated at maximum pressure and checked for possible malfunctions and leakages.

 Flexible hoses should:

• .1 avoid sharp bends;

• .2 have end fittings torqued in accordance with manufacturer’s specifications;

• .3 consider fluid flow; and

• .4 consider movement of attached bodies.

  2.5.1 Hose assemblies should be inspected frequently and maintained in good order or replaced when there is evidence of distress likely to lead to failure. Any of the following conditions may require replacement of the hose assembly:

• .1 leaks at fitting or in flexible hose;

• .2 damaged, cut or abraded cover;

• .3 kinked, crushed, flattened or twisted flexible hose;

• .4 hard, stiff, heat cracked or charred flexible hose;

• .5 blistered, soft, degraded or loose cover;

• .6 cracked, damaged or badly corroded fittings; and

• .7 fitting slippage on flexible hose.

  2.5.2 It is expected that hose assemblies may need to be replaced several times in the life of the ship. Manufacturer’s recommendations should be followed in this respect. However, hoses should be replaced as soon as possible whenever there is doubt as to their suitability to continue in service. Test reports of flexible hoses should be kept on board to ensure that correct replacement hoses are used when making repairs.

 Expansion joints are designed to accommodate axial and lateral movement. Expansion joints should not be used to compensate for pipe misalignment. Design may be based on an acceptable code or on testing of expansion joints of similar construction, type, size and use. Thermal expansion, contraction and the fatigue life due to vibration are also important points to consider. Where external mechanical damage is possible, the bellows are to be suitably protected. Each bellows expansion joint should be provided with a certificate of hydrostatic pressure testing and conformity of production.

 The bellows expansion joints should be installed in accordance with the manufacturer’s instructions and examined under working conditions.

 Bellows expansion joints should be inspected regularly and be replaced whenever there is doubt as to their suitability to continue in service.

  4.1.1 Housings and bodies of filters and strainers used in oil fuel, lubricating oil or other flammable oil systems should be made of steel or other equivalent material with a melting point above 930°C and with an elongation above 12%. Other housing and body materials may be utilized provided their use is specially considered on a case-by-case basis in relation to the risk of fire.

  4.1.2 All pressure-retaining parts should be suitable for the design temperature and pressures. The filter or strainer design and construction should facilitate cleaning and prevent or minimize spillage during maintenance.

  4.1.3 Plug type air vents are not permitted. Air vent cocks or valves should be clearly marked with open/closed positions and the discharge should be led to a safe position.

  4.1.4 Oil residues of drain trap should lead to one of the drain tanks.

 Filters and strainers should be located as far away as practicable from hot surfaces and other sources of ignition. They should not be located in positions where spillages could fall onto the flywheel or other rotating machinery parts and be sprayed around. Suitable drip trays should be provided under filters and strainers. A vertical spray shield that will prevent a high pressure fuel or lubricating oil leak from coming into contact with a hot surface should be installed between the strainer and the hot surface. If a hot surface cannot be insulated or the oil filter cannot be located in a safe position, it should be installed in parallel with another filter. The spray shields should be installed in such a manner as to not impede the servicing of the filter or strainer.

 Filters and strainers should be inspected every time they are opened for cleaning and the cover gaskets or seals should be renewed when necessary. Satisfactory seating and tightening of the cover should be verified before the system is put back into service. The filter or strainer should also be carefully bled of air before returning the unit into service.

  5.1.1 Insulation of high temperature surfaces should be primarily provided to reduce the risk of fire by reducing the temperature of surfaces below 220°C.

  5.1.2 Insulation of hot surfaces, in addition to high temperature surfaces should be considered to reduce the potential risk of fire.

  5.1.3 The insulation should be non-combustible and so supported that it will not crack or deteriorate when subject to vibration.

 Manufacturers’ instructions should be followed, if available. Permanent insulation should be used to the greatest extent possible. Insulation should be provided with readily removable sections to allow access for normal maintenance. The surface of any oil-absorbent and oil-permeable insulation should be covered by a material which is impervious to oil or oil vapours.

 A regular check of equipment should be made to confirm that the insulation is in place. When maintenance or repair of equipment has been carried out, checks should be made to ensure that the insulation covering the high temperature or hot surfaces has been properly reinstalled or replaced; surface temperature should be measured if considered necessary.

 All pressure gauges and other similar instruments in oil systems should, wherever possible, be fitted with an isolating valve or cock at the connection to the pressure take off point. The number of pressure take off points should be kept to a minimum and gauge piping runs should be as short as practicable. Copper pipes, where permitted, may be joined by brazing but soldered connections should not be used in oil systems. Temperature gauges in oil systems should be fitted into a fixed pocket (thermo-well). Oil level gauges should be of a design which is approved for the intended service. The glass or equivalent used on oil piping systems, such as sight glasses for overflow pipes of oil tanks, should be of a heat resistant type.

 The installation of level gauges that penetrate below the top of oil tanks is prohibited under SOLAS for passenger ships, and is discouraged for cargo ships. Suitably protected gauges having heat resistant flat glass of substantial thickness and self-closing fittings at each tank connection may be fitted with the permission of the Administration to oil tanks in cargo ships. Self-closing fittings should not have locking devices fitted to keep them in the open position. Round gauge glasses are not permitted.

 Copper gauge piping is particularly sensitive to work-hardening. All gauge pipes and fittings should be regularly inspected and maintained in good working order.

  7.1.1 Materials for valves and pipe fittings should be suitable for the media and service for which the pipes are intended.

  7.1.2 All gasket and seal ring materials, and any jointing compounds used, should comply with the requirements of the manufacturer and relevant international standards.

  7.1.3 Direct connection of pipe lengths should be made by direct welding, flanges, threaded joints or mechanical joints, and should be of international standards or of a design proven to be suitable for the intended purpose.

  7.1.4 All copper and aluminium-brass piping should be heat treated (annealed) and fitted with sufficient supports to prevent damage from vibration. Replacement with steel piping should be considered.

  7.1.5 All component locking devices, such as spring and tab washers and locking wires should be present and in use. (It is recognized that it is impracticable to lock fuel pump vent screws with wire, due to their frequent use. However, wire loops containing a weight attached to each screw would prevent them unscrewing under the influence of vibration if they became slack.)

  7.1.6 Valves fitted to oil fuel tanks under static pressure should be of steel or spheroidal-graphite cast iron with an elongation of 12% or above.

  7.1.7 Ordinary cast iron valves may be used in piping systems where the design pressure is lower than 7 bar and the design temperature is below 60°C.

 Pipe fittings, including flanged connections should be carefully tightened without exceeding permissible torque. If necessary, suitable spray shields or sealing tape should be used around flange joints and screwed pipe fittings to prevent oil spraying onto hot surfaces in the event of a leakage.

 Where fitted, compression fittings should be carefully examined and, if necessary, tightened (but not over-tightened) with a torque spanner to the manufacturer’s specification. Replacement with flanged connections should be considered.