The role of the Emergency generator on the ship is to provide backup power for the emergency loads in case the main generator fails or blackout condition. It is part of the larger emergency machinery and systems installed on large ships related to the engine room.
Located outside the machinery space these are much smaller in size and capacity. Although the true power and size are determined by the size of the ship and their type; container, tanker, or bulk carrier.
The construction and operational features of an emergency generator are much like that of the main generator on board. Consisting of rotor, stator bush, fan and rectifier assembly along with its housing.
The emergency generator supplies electric power to some of the most important instruments, devices, and machinery on a ship like; the emergency pumps, emergency compressors, emergency lighting, emergency alarms, navigation equipment, ventilation fans, and emergency steering motor.
An emergency generator can have an electric or crank start mechanism. In case of electric start the power source should be independent of the engine room power supply.
SOLAS Regulations For Emergency Generator On Ship
As per IMO SOLAS 74 convention each ships is required to have an emergency generator to maintain essential services. They should be self contained provided with independent fuel supply.
This emergency generator must be located at a safe place away from the main power source. Ideally above the uppermost continuous deck. This ensures there should be no further damage to the emergency generator from any major accident in the engine room.
An emergency generator is connected to its own emergency switchboard connected in parallel with the main switchboard. Both the emergency generator and its switchboard is located in the same compartment.
Further, it should be capable of providing continuous power for at least 18 hours in case of cargo ships and 36 hours in case of passenger ships. Then there is this requirement to self start within 45s of power failure.
According to SOLAS regulation an emergency generator must be fully operational for up to 10 degree of trim and 22 and a half degrees of list. Then there is the need to start anytime at 0°C temperature.
There should be at least two different methods to start. They are also required to be fitted with safety devices to restrict them from running in parallel with the main generator under any condition.
What is The Purpose of Emergency Generator?
For safe operation of the ship you need continuous power supply to emergency services and instrument on board. Thus additional generator are provided on board dedicated for emergency services to make up for the sudden demand for emergency power.
As per SOLAS regulation 19, they must include independent fuel supply and must have at least two modes of starting. Electric, pneumatic, hydraulic or manual. Further it should self start within 45 seconds of power failure.
Such generators are used on a ship in event of main generator failure, engine room flooding, and starting the ship from blackout condition.
Critical systems and instruments such as the watertight door, navigation, alarms, communication equipment, steering gear, and emergency lighting need a relatively stable and reliable source of power.
This is provided by the emergency generator that supplies both 220 and 440 V electricity to critical systems onboard via an emergency switchboard.
Where Emergency Generator Is Located?
As per IMO SOLAS 74, the emergency source of power along with all necessary equipment, fuel tank, switch board and starting power shall be kept in one dedicated space. Generally above the uppermost continuous deck not forward of the collision bulk head.
Further this dedicated compartment should have access to the open deck. The fuel tank is kept along with the generator to keep the system well isolated from the engine room system.
To ensure normal operation of the generator in extreme cold condition; antifreeze solution is added to the fuel tank. The size of this tank depends on the emergency power requirements of the ship.
Under normal conditions when the emergency generator is not operational; the emergency switchboard take powers from the main switch board using a u chord known as the inter connector.
Emergency Generator Alarms and Trips
Several alarms and trips are fitted on generators to ensure their safety and avoid any further damage or accident. On most cases it is the irregular maintenance and lack of overhauling that leads to such condition.
There are various risks involved in the safe operation of the diesel engine. Alarms and trips are one of the compulsory safety equipment installed on generators. They are installed to avoid a high risk of explosion/Fire/malfunction leading to damage to life and property.
Further, they help monitor and safeguard the normal operation of the machinery. The purpose of the safety alarms is to bring a malfunction to the attention of the watchkeeping officer on duty.
While the trips act as a safety mechanism that shuts down the machinery in case there is not much time to inform or no action has been taken and immediate safety measures needed to be taken to protect the machinery.
Reverse current, irregular frequency, over speed, low lube oil pressure, low oil sump, low bearing oil level, high bearing oil temperature, and over load are some conditions where a normal generator should trip.
Further, it should give alarms on low jacket water pressure, low bearing oil level, high bearing oil pressure, and low lube oil pressure.
But since the emergency generator is part of the critical machinery on board responsible for the safe operation of the ship. There are all alarms and just one trip in the form of over speed trip so that it should not self trip when needed; even if things are not in order.
Emergency Generator Starting Procedure
On ship it is part of the weekly routine to check and inspect emergency generator; its fuel tank, lube oil sump, battery charge level and coolant in radiators. Once done we test run the generator manually under no load.
As per SOLAS ( safety of life at sea ) regulation, an emergency generator should self start within 45 seconds of power failure. Although it should start within few seconds of the power failure.
You can test the automatic start of the generator by disengaging the breaker that connects the main switchboard to emergency switch board.
You can use the manual push start button on its control panel to start it manually on battery. To run on no-load condition just for the test press the test button while keeping it still on automatic.
In event primary starting procedure fails you need to use the hydraulic start mechanism that includes a manual reciprocating pump, spring loaded assembly and an actuator valve that needed to be opened before start.
- How To Overhaul Electrical Motors On Ship And Industries ?
- How To Successfully Parallel Generators ? | Step By Step
- Relay – Its Application, Parts And Function
- Excitation Voltage – Definition, Types & Working