B&W Fuel cam... is it negative cam
No. it is an inverse cam with a cam dwell of 330degrees, which means follower is top for 330degrees and bottom for only 30degrees. It has been shaped so to reduce the angular shift reqd to reverse, making it possible to install a simple reversing mechanism for shifting the roller.
A cam is called negative cam when it performs the action of opening sth by moving downwards like in air starting valve. The air pilot vv rollers are lifted clear of the cam except during starting.
REVERSING
START IN AHEAD DIR
when the engine has reached to a certain rpm, START and STOP solenoid valves has to be released. First, the stop valves relevant pneumatic valves will be dearated which will allow the puncture vv to deactivate and fuel pass and the starting air distributor timing will change.
1 second later, delayed by 32, air supply will be closed to starting air distributor and close the MAIN STARTING VV.
6sec later, the AHEAD solenoid vv will be released deaerating the reversing cylinders.
Block valves(55,56) are present on the starting air distributor which doesnt allow control air to pass to START solenoid vv unless the reversing is executed. The micro switch(7,8) are present on either side of the fuel reversing cylinders.
INTERLOCKS
Running direction interlock
turning gear interlock
control should be only from one of the control rooms
emcy manoeuvring (remote/local) interlock.
No. it is an inverse cam with a cam dwell of 330degrees, which means follower is top for 330degrees and bottom for only 30degrees. It has been shaped so to reduce the angular shift reqd to reverse, making it possible to install a simple reversing mechanism for shifting the roller.
A cam is called negative cam when it performs the action of opening sth by moving downwards like in air starting valve. The air pilot vv rollers are lifted clear of the cam except during starting.
REVERSING
START IN AHEAD DIR
when the engine has reached to a certain rpm, START and STOP solenoid valves has to be released. First, the stop valves relevant pneumatic valves will be dearated which will allow the puncture vv to deactivate and fuel pass and the starting air distributor timing will change.
1 second later, delayed by 32, air supply will be closed to starting air distributor and close the MAIN STARTING VV.
6sec later, the AHEAD solenoid vv will be released deaerating the reversing cylinders.
Block valves(55,56) are present on the starting air distributor which doesnt allow control air to pass to START solenoid vv unless the reversing is executed. The micro switch(7,8) are present on either side of the fuel reversing cylinders.
INTERLOCKS
Running direction interlock
turning gear interlock
control should be only from one of the control rooms
emcy manoeuvring (remote/local) interlock.
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