Section 7 Oil engines in hazardous areas

7.1.1 Oil engines are not permitted in Zone 0 and Zone 1 hazardous areas on offshore installations. Oil engines which are required to operate in Zone 2 hazardous areas are to comply with the requirements of Pt 7, Ch 2, 7.1 Application 7.1.2 to Pt 7, Ch 2, 7.1 Application 7.1.23. National Standards and Government Regulations or Codes of Practice which differ from these requirements may also be accepted, provided an equivalent standard of protection is achieved.

7.1.2 The air induction system is to be provided with a shut-off valve located between the engine air inlet filter and the flame arrester. The valve is to be capable of being closed manually. The valve is also to be capable of being automatically closed by the engine overspeed device and consideration should be given to provision being made so that the induction air valve and engine fuel supply should automatically close by a signal from a local gas sensor.

7.1.3 An approved corrosion resistant flame arrester, constructed and tested to a recognised Standard, is to be provided in the induction system. The flame arrester is to be as close to the engine as possible with good access for inspection and overhaul.

7.1.4 Joints used in the induction and exhaust systems are to be designated either as ‘open joints’ or ‘closed joints’.

7.1.5 An open joint will allow the free passage of gas but will not allow the passage of flame. The dimensions of such a joint are to be determined in accordance with Pt 7, Ch 2, 7.1 Application 7.1.8. A flame arrester is a particular type of open joint considered separately by testing.

7.1.6 A closed joint will not allow the passage of either gas or flame under normal or test conditions.

7.1.7 An approved corrosion resistant flame arrester is to be provided in the exhaust system. The flame arrester is to be constructed and tested to a recognised Standard. The flame arrester is to be fitted as close to the engine as possible, with good access for inspection and replacement. The flame arrester can be omitted if the exhaust terminates in a non-hazardous area.

7.1.8 A spark arrester is to be fitted in the exhaust system downstream of the flame arrester. The spark arrester is to be constructed and tested to a recognised Standard.

Figure 2.7.1 Relationship between length and gap for flamepaths

7.1.9 Consideration should be given to a back pressure indicator being fitted to the exhaust manifold to provide prior warning of exhaust flame arrester fouling.

7.1.10 The engine crankcase breather pipe is to be fitted with a flame arrester. For engines in enclosed Zone 2 areas, the breather pipe is to be led to the open atmosphere. The breather pipe is not to be led to the engine induction system.

7.1.11 The engine crankcase is to operate at a small positive pressure.

7.1.12 With the engine at maximum continuous rating and temperatures stabilised, no surface temperature on the engine or exhaust system is to exceed 200°C.

7.1.13 Ventilation fan blades and belts are to be of the anti-static type. The combination of materials for fan impellers and the housing are to be non-sparking under both normal and fault conditions.

7.1.14 Engine starting systems are not to introduce a source of ignition external to the engine. The system is to have appropriate safe-type certification, or to be capable of being demonstrated as being of a safe-type by appropriate testing.

7.1.15 The engine is not to be capable of running in reverse.

7.1.16 Fuel supply is to be capable of being shut off manually and automatically in the event of:

Overspeeding;
High exhaust temperature, see Pt 7, Ch 2, 7.1 Application 7.1.17;
High cooling water temperature; or
Low lubricating oil pressure.

7.1.17 The high exhaust temperature sensor is to be located upstream of the exhaust flame arrester. The high exhaust temperature sensor and engine shut-down on high exhaust temperature can be omitted if the exhaust pipe terminates in a safe area.

7.1.18 Basic operating instructions should be permanently attached to the unit giving details of stop, start and emergency procedures.

7.1.19 Where an engine is fitted inside any enclosure, the following requirements are to be complied with, as applicable:

Where an engine is located inside an enclosed Zone 2 hazardous area, the space is to be independently ventilated at a recommended minimum rate of 20 air changes per hour whilst the engine is running and 12 air changes per hour when stopped.
For engines placed inside enclosures of any type, it is recommended that fire and gas sensors be provided inside the enclosure are suitably alarmed to a continuously manned control room.

7.1.20 A hydraulic proof test at a gauge pressure of 5 bar or 1,5 times the maximum pressure obtained in explosion tests in accordance with Pt 7, Ch 2, 7.1 Application 7.1.21 is to be witnessed on the induction and exhaust system components without showing signs of leakage.

7.1.21 For engines of 370 kW (500 shp) and above, the induction and exhaust systems are to be explosion tested to a recognised Standard without showing signs of damage or flame transmission to the atmosphere. The maximum explosion pressure is to be recorded and used in the hydraulic proof test in Pt 7, Ch 2, 7.1 Application 7.1.20.

7.1.22 Complete engine units and driven components are to be examined and tested at the manufacturer’s works or other suitable works before being put into service. Thereafter, the complete unit is to be examined annually and the original certificate endorsed or as otherwise agreed to ensure a permanent written record of survey. It is recommended that time clocks of the non-resetting type be fitted to the engine.

7.1.23 Where an engine manufacturer carries out satisfactory type tests on an engine or series of engines and subsequently provides conversion kits for similar engines, proof tests can be waived. However, each converted engine is to be shop tested in accordance with Pt 7, Ch 2, 7.1 Application 7.1.22.