The diesel engine coupled to a fire-fighting push unit must be able to operate continuously at full load with power compliant with precise standards (ISO 3046) even in unfavourable environmental conditions (the standard also provides for a temperature of 5°C in the engine room). For this to happen not only must the motor be appropriately designed and installed but it must also undergo punctual and professional maintenance.
The UNI EN 12845 standard distinguishes the maintenance activities to be carried out by the operator of the fire prevention system from those to be entrusted to competent and qualified technicians. Among the latter, a prominent place is undoubtedly reserved to periodic maintenance of the diesel engines associated with the pumps.
In fact the pumps must be driven by motors (electric or diesel) that are capable of supplying the pumps with the power required for the various characteristic curves.
Firstly, the technician must make sure that the engine is clean and dry (the rooms where the thrust units are housed may be underground, at risk of moisture condensation or even flooding). For a diesel engine to work, on request, this must obviously have sufficient fuel in the tank to guarantee sufficient operating time (the duration of the water supplies depends on the level of risk - light, ordinary or high risk). Fuel storage is in fact regulated both with regard to the structural characteristics - tank, pipes, etc. - and with reference to the installation conditions and the level verification instruments. Particular attention must be paid to all these aspects during maintenance.
The lubricating liquids must retain suitable quality and quantity characteristics, as must the circuits that guarantee their recirculation. Similarly the cooling circuits and liquids must be checked and guaranteed to ensure compatibility with operation of the engine. For this purpose, careful maintenance is not limited to checking that the engine is maintained but also involves the conditions of the premises in which it will operate, which may be a discriminating factor on the cooling capacity; although this characteristic is a design choice it is possible that subsequent interventions may alter the design conditions, altering the envisaged cooling capacity. In some cases, a system of forced air extraction from the engine rooms could be provided; this system therefore becomes a critical element to be placed under adequate maintenance.
The maintenance technician also checks the condition of the battery electrolyte, the charging circuit and the general correct operation.
According to a replacement program, the technician checks and replaces the oil, diesel and air filters. and inserts a new filter cartridge, if necessary. All the tests performed must be able to be recorded and compared, from year to year.
As this is a highly reliable system but in any case subject to malfunctions, a redundant logic must be provided which protects against any missed start-up of the diesel engine and therefore, as part of the maintenance program, a failure test must also be provided to verify that the alarm and back-up systems intervene correctly.
During operation the engine must be able to release the exhaust fumes; the ducts intended for this purpose must comply with precise construction and installation standards but must also maintain, over time, the characteristics of adequacy (for example, the exhaust terminals must be appropriately protected against atmospheric events and equipped with a protection grid and must comply with precise distances from the external reference plane and from windows and doors. It is not unthinkable that, especially in an industrial context in frequent plant reorganisation, the conditions around the pump rooms may change; a competent maintenance person knows how to detect these possible variations.