SAFITIES OF MACHINERIES

MAIN SWITCH BOARD (MSB) SAFETIES:
Electrical safeties:
Dead front type switchboard,
Fuses, Relays, Circuit breakers, Earth fault indicators, Under voltage relay,
Reverse power trip, Preferential trip, Over current trip, Short circuit trip, Arc chute,
Ebonite Rod ( to remove static charge).

General safeties:
  Insulated  hand  gloves,  dry  boiler  suits,  shoes  without  metallic  part, 
Rubber  pad  in  front  of  switchboard,  0.6m  gap  behind  switchboard, 
Panel  doors  to  be  earthed,  interlocked  handles  for opening doors.
  No water, oil, or steam pipeline in its vicinity.

Overhead crane safeties:
1)  The most important safety feature of the crane is the electromagnetic fail safe
brakes which do not 
allow the crane to fall with the load even when there is failure of power. For this:
  Normally centrifugal brakes are used which are fitted inside the rotating
drum.
  The brake pads are always in applied state and pushed by magnetic springs
when not in operation or when there is a power failure.
  As the crane is operated or the power is supplied, the spring gets pulled
inward or compressed due to the electromagnetic effect of the current. This
allows the crane to be operated normally.
2) Emergency stop is provided in the remote so that the operator can stop the crane
at any time.
3) The motor is fitted with distance limit switch in both transverse and longitudinal
direction
4) Mechanical stoppers are provided for both directions in case the electrical
distance limit trips fail.
5) The up and down travel of the hook is also attaches with automatic stopper to
avoid overloading of the motor.
6)  The motor is fitted with thermal protection trip. When the motor windings get
overheated, trip will activate saving the motor winding from burning.
7)  Load limit switch is also fitted which will trip the motor if the load to be lifted
is above the crane capacity.
8) It’s the responsibility of senior officers to operate the crane and to make sure all
the personnel involve in any lifting operation are at a safe distance during
operation of the crane.
9) Additional tools like i-bolts, shackle, wire sling, belts etc. used for lifting must
be checked before use. 
10) It should be noted that no one walks or stand below the crane when it is in the
loaded condition.

MOTOR SAFETIES
Motor protection and safeties:
1.  Overcurrent and single phasing protection relays
2.  under voltage relay
3.  Short circuit relay (Trigger fuses for HV systems)
4.  Temperature sensor for motor insulation

Safety device on life boat
Mechanical brake (to prevent accident falling) 
Centrifugal brake (to control life boat falling speed between 20 to 40 m/min) 
Limit switch (to prevent over tightening of rope) (it is fitted arm of davit just
before in limit) 
Harbour safety pin (for davit)

Safety devices for steering system
@Hunting gear 
@Buffer spring 
@ Angle adjusting stop (Hand over position limit switch) 
@ Double shock valve 
@Relief valve 
@ Tank level alarm (oil) 
@ Over load alarm

STEERING GEAR SAFETIES
Hydraulic safeties:
  Level switch, low level, low low level alarm for hydraulic oil tank.
  Relief valve.
  Manual bypass valve.
  Low pressure valve.
  High lub oil temp. Cut out.
  Low level cut out
Electrical safeties:
  Electrical and mechanical stopper for rudder.
  Electrical motor overload alarm.
  Power failure alarm.
  High temp. Alarm.
  Self starting after power failure.
  Short-circuit trip.
  Phase failure alarm.
  200% insulation in motor

Windless safety device
  Cable stopper (chain stopper, bow stopper) 
  Overload trip 
  Overspeed trip
  Hand brake 
  Slipping clutch for overload prevents any undesirable damage such hull
damage due to anchor and rope broke out.

Scavenge Space Protection Devices
1) Electrical temperature sensing device fitted within the trunking, which
will automatically sound an alarm the event of an excessive rise in local
temperature (above 200°C) 
2) Pressure relief valves consisting of self-closing spring loaded valves are
fitted and should be examined and tested periodically.
3)  Fixed fire extinguishing system may be CO2, Dry Powder or Steam.

crankcase safety devices
1. Breather pipe with flame trap
2. Crankcase exhaust fan
3. Oil mist detector
4. Crankcase relief doors
5. Bearing temperature sensor
6. L.O return temperature sensor

Battery room safety arrangement

Safety is provided by 
1)  Proper ventilation 
2)  Prevention of heat source for ignition

Ventilation
  Independent exhaust fan provided 
  Inlet duct should be below battery level, and outlet at top of the
compartment

Prevention of heat source for ignition
  No naked light and no smoking 
  Uses of externally fitted light or flameproof light 
  Cables of adequate size and they are well connected 
  Never placed Emergency Switchboard in this room 
  Use insulated spanner and plastic jug for distilled water, to prevent short
circuit 
  Room temperature, maintained at 15 ~ 25°C

Generator safety devices
  Over speed trip 
  L.O low pressure trip @ alarm
  Low level sump trip 
  F.O low pressure alarm 
  Jacket water high temperature alarm 
  Thermometer 
  Pressure gauge 
  L.O high temperature alarm 
  Dip stick 
  Crankcase relief valve

ALTERNATOR  SAFETIES 
The three main type alternator protection are:
a. Over current protection.
b. Reverse power trip
c. Under voltage trip

PURIFIER
  Low pressure switch in the outlet of clean oil to protect the oil going out
with water
  Emergency brake to help the purifier to pass the critical speed as soon as
possible
  High pressure switch to avoid water to come with clean oil in the clean oil
outlet
  Water transducer to avoid water to come with clean oil in clean oil outlet
  High temperature alarm and shutdown
  Low seal water pressure

BOILER
ALARM AND TRIPS
The most important alarm and trip functions on marine boilers
Function  Audible and visual  Action
Low water level  Alarm   
Low Low water level *  Alarm & Trip  Burner stop
High water level  Alarm   
High High water level  Alarm
Feedwater pump stop
Low steam pressure Alarm  
High steam pressure  Alarm  Burner stop
Low feedwater pressure  Alarm Stand-by pump start
Low fuel oil pressure  Alarm & Trip Stand-by pump start
Low fuel oil temperature  Alarm & Trip   
High fuel oil temperature  Alarm & Trip   
Force draught fan  Alarm & Trip  Burner stop
Low atomizing steam
pressure
Alarm  Burner stop
Flame failure ** Alarm  (overridden during light-up)
Burner stop
Burner not in firing position Alarm  Burner stop

Boiler safety devices 
1)  Safety valve 
2)  Low / high water level alarm 
3)  Too low water level alarm and shut down 
4)  Water level indicators 
5)  Pressure gauge 
6)  Low fuel oil pressure alarm 
7)  Low / high fuel oil temperature alarm 
8)  Flame failure alarm 
9)  Smoke density alarm 
10)  Easy gear arrangement 
11)  Air vent 
12)  Force draught fan stop alarm  
13)  Low / high steam pressure alarm

COMPRESSOR
Relief valve:
Fitted after every stage to release excess pressure developed inside it. The setting
of the lifting pressure increases after every ascending stage. Normally fitted
between 1st stage and intercooler and 2nd stage – aftercooler.
Bursting disc:
A bursting disc is a copper disc provided at the air cooler of the compressor. It is a
safety disc which bursts when the pressure exceeds over the pre-determined value
due to leaky air tubes of the cooler (intercooler or aftercooler).
Fusible plug:
Generally located on the discharge side of the compressor, it fuses if the air
temperature is higher than the operational temperature. The fusible plug is made up
of material which melts at high temperature.
Lube Oil low pressure alarm and trip:
If the lube oil pressure goes lower than the normal, the alarm is sounded followed
by a cut out trip signal to avoid damage to bearings and crank shaft.
Water high temperature trip:
If the intercoolers are choked or the flow of water is less, then the air compressor
will get over heated. To avoid this situation high water temperature trip is activated
which cut offs the compressor.
Water no-flow trip:
If the attached pump is not working or the flow of water inside the intercooler is
not enough to cool the compressor then moving part inside the compressor will get
seized due to overheating. A no flow trip is provided which continuously monitor
the flow of water and trips the compressor when there is none.
Motor Overload trip:
If the current taken by motor during running or starting is very high then there is a
possibility of damage to the motor. An overload trip is thus fitted to avoid such
situation.
AUTOMATIC MOISTURE DRAIN VALVE(Unloader)
this reduced the starting torque for the machine and clear out any accumulated
moisture and oil in the system

Safety devices on refrigeration system
1) L. P cut-out on compressor suction side: Set at a pressure corresponding to 5°C
below the lowest expected evaporating gauge reading
2) H.P cut-out on compressor discharge side:Set at a pressure corresponding to 5°C
above the highest expected evaporating gauge reading
3)  Lube oil low pressure cut-out: Oil pressure usually set at 2 bar above crankcase         
pressure 
4)  Cooling water L .P cut-out in condenser side 
5)  Safety spring loaded liquid shock valve on compressor cylinder head 
6)  Bursting disc on cylinder head, between inlet and discharge manifold 
7)  Bursting disc on Condenser, [if fitted] 
8)  Relief valve on Condenser; air purging valve on condenser 
9)  Master solenoid valve: to prevent liquid being entered into Compressor, when
the plant is standstill, especially in Large Plant

Safety devices on starting air line 
1. Spring loaded safety valve or bursting cap.(if bursting cap fitted, no need
relief valve)
2. Flame trap.(At Joint where manifold to each cylinder startingline)
3. Starting air line drain valve (Inlet of automatic valve)
4. Turning gear interlock

Safety device on O.W.S 
Pressure relief valve on discharge pipe 
O.D.M system with high ppm alarm and automatic pump stopping device. 
Test cock (level), drain valve

Incinerator Safety System
1)  The safety devices shut down the unit and give out alarms: 
a.  When the pilot and main burner fail to operate 
b.  When the flue gas temperature reaches above 400’C 
c.  When the cooling fan fails to operate 
2)  Emergency fuel shutdown valve 
3)  Micro switch, fitted to hinged furnace door (Interlock)

Hai friends, these are the common safeties in the machineries, I just share what I
known if any mistakes; add some points please let me knew. I will accept my
mistakes and correct myself.
-   HELPING MIND
    {“Strong people don't put others down... They lift them up.” }