Air Starting System

1. Air Starting System Design & operation details of various parts of the system may differ according to engine manufacturer. But basic function within the system is essentially same in all makes of engine. Main Components • Air receiver • Automatic valve • Starting air distributor • Starting air valves

2. Leak test valve Main Components of Air Starting System

3. Air Starting System Air Receiver At least two air receivers with air pressure 25 – 30 bar and sufficient capacity without replenishment will able to provide: • 6 starts for non reversible engine • 12 starts for reversible engine

4. Automatic Valve • To supply air automatically for starting engine • Quickly shut off starting air when engine is running on fuel • For safe running & conserve starting air • Normally hand wheel is set to automatic position • In emergency, automatic valve can be operated manually • Must be locked shut during maintenance & prior engaging turning gear

5. Starting Air Distributor To ensure opening of starting air valves on cylinders in correct sequence according to firing order. Types of distributors: • Circular disc with suitable ports • Spool type valve radially around central cam • Spool type valves laterally above sliding camshaft Distributor cam is negative type cam.

6. Starting Air Valve • Fitted in each cylinder cover • Timing of opening & closingis controlled by cam • Balance piston & valve head are of same nominal dia. In order to hold the valve in balance when main air is open • Spring holds the valve closed • Guide ensures correct alignment of valve • Periodical routine check is necessary for any leakage

8. Air Starting System Pilot Valve • Operation of the v/v vents compressed air from actuating piston in automatic v/v & causing it to open • Action of pilot v/v also controls air supply to distributor • Controlled directly by starting lever or indirectly by solenoid control

9. Air Starting System Non Return Valve • Located between engine and automatic starting air valve • Robust in construction • Prevents air starting line explosion getting back to air receiver • Contains explosion in short length of pipe as it is fitted close to engine

10. Air Starting System Relief Devices It is located on the starting air manifold, between non return valve & cylinder air starting valve. • Spring loaded relief valve • to guard against overpressure • resets automatically • but open to tampering • Bursting disc • relatively tamper proof • unlike relief v/v doesn’t reset – needs blanking off for restarting

11. Air Starting System Problems • Sluggish operation of starting air and distributor valves due to dryness and rust • Leaky valves Cause Moisture contained in air carries away the lubricant and causing sticky / frozen valve. Effect on engine • Engine cannot start and wastage of starting air • Gas leakage may cause explosion hazard

12. Leak Test of Air Starting Valve • Ensure turning gear is disengaged • No one is working in crankcase or on the engine • Obtain propeller clearance from bridge • Close shut off v/v for the distributor • Keep indicator cocks open • Open main air stop v/v & automatic v/v • Put maneuvering handle to start position • Leaky v/v will be indicated from indicator cock

13. Engine fails to start on air • Turning gear engaged • Water collected on top of piston • No & bar control air, 30 bar starting air • No electrical power supply to remote control unit • Solenoid operated valve problem • Distributor, reversing mechanism, pilot valve stuck