Calculation of Air Starting Vessel

Air Starting Vessel

GENERAL
The air bottle or air receiver is a large container acting as a reservoir to store compressed air supplied by the main air compressor of the ship at high pressure. This compressed air is very important to start main engine or auxiliary engine.

Air Starting Vesel Purpose

• The high pressure is used for initial starting of the marine I.C engines present onboard vessel.

• It also supplies control air to the marine engines.

• Service air is supplied from the air bottle.

• If the quick closing valves are air operated, safety air is supplied through air bottle.

• Spring air for exhaust valve is supplied through air bottle.

The starting air supply is to be split up into not less than two starting air vessels of about the same size, which can be used independently of each other.

Diesel-mechanical main engine
For each non-reversible main engine driving a controllable pitch propeller, or where starting without counter torque is possible, the stored starting air must be sufficient for a certain number of starting manuovers, normally 6 per engine.

The exact number of required starting manoeuvres depends on the arrangement of the system and on the special requirements of the classification society.

Diesel-electric auxiliary engine
For auxiliary marine engines, separate air tanks shall only be installed if the auxiliary sets in engine-driven vessels are installed far away from the main plant.

Electric propulsion main engine
For each main engine for electrical propulsion the stored starting air must be sufficient for a certain number of starting manoeuvres, normally 6 per engine.

The exact number of required starting manoeuvres depends on the arrangement of the system and on the special requirements of the classification society.

Calculation formula for starting air vessels as follow :


 Where :
V [litre]       = Required Vessel Capacity
Vst [litre]     = Air consumption per nominal start
 fDrive         = Factor for drive type (1.0 = diesel-mechanic, 1.5 = alternator drive)
zst             = Number of starts required by the classification society
zSafe           = Number of starts as safety margin
VJet [litre]    = Assist air consumption per Jet Assist
zJet            = Number of Jet Assist procedures
tJet [sec.]     = Duration of Jet Assist procedures
Vsl ( litre)    =  Air consumption per slow turn
zsl             = Number of slow turn manoeuvres
pmax [bar]      = Maximum starting air pressure
pmin [bar]      = Minimum starting air pressure

notes :
1) The required number of jet maneuvers has to be checked with yard or ship owner.
2) If other consumers (i. e. auxiliary engines, ship air etc.) which are not listed in the formula are connected to the starting air vessel, the capacity of starting air vessel must be increased accordingly, or an additional separate air vessel has to be installed.

Example of Starting air / control air consumption 


 

Hopefully helpfully 😊
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