Personal Protective Equipment (PPE)

Essential PPE for High Voltage Work:

• Electrically insulating safety helmet
• Insulating rubber gloves (must meet IEC standards)
• Insulating boots
• Insulation mat
• Face shield, safety glasses, or arc protective hood

Glove Testing:

• Use a pneumatic glove tester to check for damage

High Voltage Operation Procedure

Pre-Work Steps:

1. Obtain electrical permit to work
2. Follow the DIE principle: Disconnect, Isolate, Earth
3. Perform earthing down, circuit earthing, and bus bar earthing

Earthing Process:

• Connect earth to all three conductors at the circuit breaker
• Use a key system to prevent circuit breaker activation until earth is removed
• For bus bar work, isolate from all electrical sources and use portable leads for earthing

Permit to Work:

1. Issue before starting work
2. Include work description and isolation details
3. Declare earthing down and safety measures
4. Authorize work commencement
5. Cancel permit after job completion

Safety Measures

Workspace Setup:

• Place danger signs at the front door
• Display single line diagram
• Cover entire switchboard length with rubber mat
• Provide fire extinguisher (Class C)
• Display first aid chart
• Ensure electrical installation license is visible
• Maintain a key box and logbook

Work Procedure:

1. Wear correct PPE
2. Isolate work area from power supply
3. Implement lockout and tagout procedures
4. Verify absence of voltage using appropriate detectors
5. Apply short circuit and earth systems
6. Mark work area and warn others
7. Issue permit to work
8. For external high voltage work, obtain certification from supply controller

Transformer Isolation

1. Obtain necessary approvals
2. Open circuit breaker in high voltage system (HVS)
3. Set HVS circuit breaker to isolated position
4. Use earth switch in HVS to ground cable
5. Retrieve key from ground switch panel
6. Place warning signs on HVS front
7. Use HVS key to access transformer room
8. Verify transformer is not energized
9. Apply mobile grounding device to each transformer phase

.hv safety

.hv

.high voltage safety

Personnel who are required to routinely test and maintain HV equipment should be trained in the necessary practical safety procedures and certified as qualified for this duty.

• Approved safety clothing,
• Highly insulating safety gloves
• footwear,
• eye protection and
• hard hat should be used where danger may arise from arcs, hot surfaces and high voltage etc.

Safety equipment should be used by electrical workers includes insulated rubber gloves and mats.

Safety equipment is tested regularly to ensure it is still protecting the user.

 A insulated material or rubber mat can be used as a dead front of all electrical installations and equipment.

The access to HV switchboards and equipment must be strictly controlled by using a permit-to-work scheme and isolation procedures together with live-line tests and earthing-down before any work is started. The electrical permit requirements and procedures are similar to permits used to control access in any hot-work situation, e.g. welding, cutting, burning etc. in a potentially hazardous area.

What Are The Additional Safeties On High Voltage System?

> HV circuit breakers either air, gas or vacuum breakers.

> To minimize the size of earth fault current, neutral earthing resistor is using in HV system. Better insulating material like Micalastic is used.

> HV equipment are well designed to have an insulation life of 20 years

> Special relays are provided for overall circuit protection of HV circuit

> Earthing down is essential for HV maintenance which should be declared in Electrical Permit to Work.

.switchboard safety device .switch board safety device .msb

The main switchboard (MSB) on a ship is a critical component of the electrical power distribution system. To ensure safe and reliable operation, various safety devices and measures are implemented. Here are the key switchboard safeties and their functions:

Electrical Safety Devices

Circuit Breakers
Circuit breakers are automatic shutdown devices that activate during electrical abnormalities. They protect the system by opening the circuit during overloads or short circuits, isolating the fault from the rest of the network.

Fuses
Fuses provide short circuit protection and come in various ratings. When current exceeds the safe value, the fuse material melts, isolating the faulty system from the MSB. Typically, fuses are rated at 1.5 times the full load current.

Over Current Relay (OCR)
OCRs protect against high currents on local panels and the MSB. They are set to trip at full load current with a time delay, providing protection where low power signals are used as controllers.

Earth Fault Indicators
These devices detect and indicate any ground faults in the electrical system, helping to prevent potential hazards.

Under Voltage Relay
This relay protects equipment from damage due to low voltage conditions.

Reverse Power Trip
This safety feature prevents power from flowing back into the generator, which can cause damage.

Preferential Trip
This system automatically sheds non-essential loads during power shortages to maintain critical systems.

Short Circuit Trip
This protection activates during short circuit conditions to prevent damage to the electrical system.

Physical Safety Measures

Dead Front Panel
This safety feature prevents access to live parts from the front of the switchboard. The panel cannot be opened until the power is switched off.

Insulated Rubber Mats
Anti-skid, insulated rubber mats with a minimum thickness of 15 mm are placed in front of and behind the MSB to provide electrical insulation for operators.

Interlocked Door Mechanism
The door opening mechanism is interlocked with the power supply, preventing access to live components.

Proper Earthing
The MSB and its components must be properly earthed to prevent electrical shock hazards.

Ebonite Rod
This non-conductive rod is used to remove static charges from the switchboard.

Additional Safety Measures

Proper Ventilation and Illumination
The MSB location should have good ventilation and lighting to ensure safe operation and maintenance.

No Water or Oil Pipes Nearby
Water, steam, or oil pipelines should not pass in the vicinity of the switchboard to prevent potential hazards.

Safety Charts and Signage
Charts indicating procedures for electric shock treatment and danger signs should be prominently displayed near the MSB. By implementing these safety devices and measures, ship operators can significantly reduce the risk of electrical accidents and ensure the reliable operation of the ship’s power distribution system.

.cold ironing

Alternate Maritime Power or AMP is an anti-pollution measure which helps in reducing air pollution generated from diesel generators by using shore electric power as a substitute.

AMP is used when the ship is stay at port, required to stop idling the engines (low load operation) and transfer the power source to a land base. This allows the ship to switch-off its generators. It helps in significant reduction in noise and air pollution.

• AMP done with the help of supply cables that are plugged into an electricity supply board in the port on one end and to the ship’s power supply board on the other. The process is called cold ironing.
• At present, there are four different variations in the AMP that is provided from the port to a ship.
• 11000 Volts of AC (Alternate Current)
• 6600 Volts of AC
• 660 Volts of AC
• 440 Volts of AC

The AMP system comprises major components such as – Cable Reel, Reel Control Centre & Pendant, Amp Connection Box, 6600v Shore Panel, Transformer, Main Switch Board, Amp Control Panel.

.motor running hot

1. Electrical overload caused by excessive voltage supply or overwork by drawing more current will lead to overheating issues. As the motor works harder or under unusual load, heat will be the chief byproduct, leading to failure.

2. Low resistance is the most common reason behind electric motor failure. Degradation of motor windings by heat will pave the way for short-circuits and leakages, which leave the motor at risk for failure.

3. Contamination of dust and debris will raise the internal temperature of a motor and keep it from cooling, which leads to excessive heat over a longer period of time. This generally occurs without proper maintenance or venting for particles.

• A lack of ventilation: If there is something blocking the ventilation holes for your electric motor, then hot air won’t escape and will build up within the system, causing damage. Scheduling regular maintenance on your motor can help reduce this risk.

4. Start-stop frequency plays a big role in heat damage. Excessively starting, stopping, and starting the motor again won’t allow it to cool properly. The result is a high-heat environment that wears on the integrity of components.

5. Vibration from a condition like soft foot leads to excessive heat. If vibrations are severe enough, they’ll raise temperatures to unsafe levels and stress components beyond their capacity for heat.

6. High ambient temperatures

If a motor is running in a much warmer environment than it was designed for, it can overheat because the ambient temperatures will make it more difficult for the motor to cool down properly. Check the insulation class of your motor (found on the motor’s nameplate).

7. High or low voltage supply

Power supply may be insufficient due to amp draw. In order to overcome load or inertia at a stand-still, the motor’s running current will be too much high under load. Incorrect voltage supply will make the motor work harder and could cause it to overheat.

.PREFERENTIAL TRIP .pref

Preferential tripping in a Marine electrical distribution system are designed to disconnect non-essential circuits (e.g. Breakers controlling air conditioning, galley power, blowers, refrigeration etc.) in the event of partial overload or partial failure of the supply with the aim of preventing operation of the main breaker trip and loss of power on essential services.

A method for operating all the overall type trips from one load current carrying coil uses to instantaneous trip levers.

• The top Lever is arranged as an instantaneous short circuit trip and opens the breaker directly through mechanical linkages.

• The bottom lever process instantly at the lower overload current setting and by doing so, complete the circuit through two or more non essential circuit trips and a main breaker trip all incorporating dashpot time delay.

• These relays will trip out non essentials at 5 and 10 second intervals based on their priority and finally if the overload persists the main breaker after 15 seconds.

• Warning of overload is given by the alarm overload protection is provided on both poles

• The current passes through the electromagnetic coil and the linkage are kept from contacting using a spring arrangement. As soon as the current value increases the limit the electromagnetic coil pulls the linkage up against the spring force and operates the instantaneous circuit and the alarm system. The lower linkage complete the circuit for the preferential trip circuit

• The current passes through the coil in the preferential trip circuit which pulls the Piston in the dashpot arrangement. The movement of this piston is governed by the diameter of the orifice and the time delay made by the same.

• The preferential trip operates at 5,10 and 15 seconds and the load is removed accordingly if the overload Steel pursuits then an audible & visual alarm is sounded.

.reverse power relay .rpr

The Reverse Power Trip Relay is a crucial protective device used in electrical systems, particularly for generators. It operates based on the principles of Faraday’s law of induction and Lenz’s law.

Working Principle

• Eddy Currents: Loops of electrical current induced within a conductor due to Faraday’s law of induction.
• Lenz’s Law: An eddy current creates a magnetic field that opposes the magnetic field that created it.

Components and Structure

• Aluminum Disc: A lightweight, non-magnetic disc mounted on a spindle with low-friction bearings.
• Magnetic Field Coils: Both voltage and current coils produce magnetic fields that pass through the disc.
• Trip Contacts: Located on the spindle.
• Stopper: The disc rests against this under normal power flow conditions.

Operation

Normal Power Flow:

• The disc bears against the stopper.
• Trip contacts on the spindle remain open.

Reverse Power Condition:

1. Eddy Current Generation: Magnetic fields from the coils pass through the disc, causing eddy currents.
2. Torque Production: The interaction between the eddy currents and magnetic fields produces a torque effect on the disc.
3. Disc Rotation: When power reverses, the disc rotates away from the stopper.
4. Contact Closure: As the disc rotates, the contacts close, triggering the circuit breaker to trip.

Safety Feature: To prevent unnecessary tripping due to power surges during synchronization, the relay incorporates a time delay of 5 seconds.

Reverse Power Relay (RPR) detailed Operation:

Basic Principle

A reverse power relay detects when power flows in the reverse direction from the load back to the generator, which can damage the generator. It protects the system by disconnecting the generator when reverse power is detected.

Components

• Voltage coil (connected in parallel)
• Current coil (connected in series)
• Aluminum disc
• Trip contacts

Magnetic Field Generation

1. Voltage coil:
   • More turns, higher inductance
   • Induced current lags by ~90°
   • Produces weaker magnetic field
2. Current coil:
   • Fewer turns, lower inductance
   • Induced current lags less
   • Produces stronger magnetic field

The magnetic fields from both coils are approximately 90° out of phase.

Disc Movement

• Eddy currents are induced in the aluminum disc by the magnetic fields
• Torque is generated on the disc (Lorentz force)
• Under normal power flow, disc rotation is restricted by stoppers
• During reverse power, disc rotates in opposite direction

Trip Mechanism

• Disc rotation closes trip contacts when reverse power occurs
• This activates the protection system to disconnect the generator

Setting the Reverse Power Relay

• Typically set to 20-50% of the prime mover’s motoring power
• Motoring power: Power required to drive the prime mover at rated RPM
• Setting obtained from prime mover manufacturer specifications

Considerations for Ships

• Marine applications require careful calibration
• Settings may vary based on ship type and operating conditions
• Regular testing and maintenance are crucial for reliability

Reverse Power in Electrical Systems

Reverse power is a condition in which power flows from the bus bar into the generator, contrary to the normal power flow direction. This phenomenon can occur due to various reasons and has significant implications for electrical system operation and safety.

Primary Causes of Reverse Power

1. Prime Mover Failure

• Occurs when the engine or turbine driving the generator fails
• Common causes include:
  • Fuel starvation in the prime mover
  • Speed controller malfunction
  • Mechanical breakdown of the prime mover

2. Motoring Condition

• Happens when a generator in a synchronized system experiences prime mover failure
• The generator draws power from the bus bar and runs as a motor, driving the failed prime mover
• Occurs because all synchronized generators maintain the same frequency
• Any drop in frequency in one generator causes other power sources to pump power into it

3. Synchronization Issues

• Can happen during the process of connecting a generator to the bus bar
• If the incoming machine’s frequency is slightly lower than the bus bar frequency when the breaker closes, power will flow from the bus bar to the machine

Mechanism of Reverse Power

In a synchronized condition, all generators operate at the same frequency. If one generator’s frequency drops due to prime mover failure, other power sources on the bus bar will automatically supply power to maintain system stability. This reverse flow of power is detected by the reverse power relay.

Prevention and Best Practices

To prevent reverse power during synchronization:

• The incoming machine’s frequency should be kept slightly higher than the bus bar frequency
• This is often referred to as running in the “too fast” direction
• Ensures the machine takes on load as soon as the breaker closes

Importance of Reverse Power Protection

Reverse power protection is crucial because:

• It prevents damage to the prime mover (engine or turbine)
• It avoids unnecessary power consumption by a non-producing generator
• It helps maintain overall system stability and efficiency

Detection and Protection

Reverse power is typically detected and protected against using:

• Reverse power relays
• Advanced generator protection systems
• Continuous monitoring of power flow direction

.avr

The key components in this AVR circuit are:

• Alternator (generator)
• Automatic Voltage Regulator (AVR) unit
• Exciter
• Main transformer

Voltage Generation

1. The alternator, which is typically star-connected, generates AC voltage through electromagnetic induction as it rotates.
2. The generated voltage is fed to the main transformer, which steps up or steps down the voltage to the desired level for distribution.

Voltage Regulation

1. The AVR unit continuously monitors the output voltage of the alternator.
2. If the output voltage deviates from the desired setpoint, the AVR adjusts the excitation current supplied to the exciter.
   • If the output voltage is too low, the AVR increases the excitation current.
   • If the output voltage is too high, the AVR decreases the excitation current.
3. The exciter, which is essentially a smaller generator, provides the magnetic field for the alternator rotor.
4. By adjusting the excitation current, the AVR effectively controls the strength of the rotor’s magnetic field, which in turn regulates the output voltage of the alternator.

Output

1. The regulated voltage from the alternator is fed to the main transformer.
2. The transformer steps the voltage up or down as needed for distribution to the switchboard and connected loads.

By continuously monitoring and adjusting the excitation current, the AVR maintains a stable output voltage from the alternator despite variations in load or other factors. This ensures a reliable and consistent power supply to the connected equipment.

Smoothing Capacitor

Smoothing capacitors are commonly used in power supply circuits to reduce voltage ripple and provide a more stable DC output.

Function of a Smoothing Capacitor

The main functions of a smoothing capacitor are:

1. Ripple Reduction: It reduces the voltage fluctuations (ripple) in the rectified DC output.
2. Voltage Stabilization: It helps maintain a more consistent voltage level by storing and releasing charge.
3. Current Smoothing: It smooths out the pulsating DC current, making it more suitable for electronic circuits.

How It Works

1. Charging: The capacitor charges when the rectified voltage rises above the capacitor’s stored voltage.
2. Discharging: It discharges when the rectified voltage falls, providing current to the load.
3. Continuous Cycle: This charge-discharge cycle happens rapidly, effectively filling in the gaps in the rectified waveform.

Based on the circuit diagram and the query, I’ll explain the voltage comparator in the context of the Automatic Voltage Regulator (AVR) circuit:

Voltage Comparator in AVR

Its function is to compare the actual output voltage of the alternator with a reference voltage.

How It Works

1. Voltage Sensing: The comparator continuously monitors the alternator’s output voltage.
2. Reference Voltage: It compares this sensed voltage against a preset reference voltage, which represents the desired output voltage level.
3. Comparison: The comparator determines whether the actual voltage is higher or lower than the reference voltage.
4. Output Signal: Based on this comparison, it generates an error signal.
5. Control Action: This error signal is used to adjust the excitation current supplied to the exciter.

Function in the AVR System

1. Voltage Regulation: The comparator’s output helps maintain a constant voltage output from the alternator
2. Error Detection: It quickly detects any deviation from the desired voltage level.
3. Feedback Control: The comparator’s output initiates the feedback loop that adjusts the excitation current.

.star delta

Direct-on-line starters is the most commonly used, the most usual consideration being whether the generator and the distribution system can withstand the starting current. In the case of loads with high inertia (e.g. oil separators) the starting time may also be a factor.

 The starting current is 5 – 8 times the full load current and the heating of windings is 25 – 64 times normal due to I²R effect. Furthermore, at the instant of starting, there is not windage and radiation. A long starting period may result in overheating. Representative starting periods may be 15 seconds for a 1.5 kW motor and 25 seconds for a 30 kW motor with an initial starting current of not more than 6 times full load current.

 For these reasons, it is desirable not to make repeated successive starts without intervening periods of cooling.

In the starting position, the voltage across each phase windings is 58% of the line voltage as it is star connected, i.e. with consequent reduction in starting current.  It is 1/3 the starting than delta.

Operation of Star-Delta Starter

1. At starting contactor L ₂ closes and time delay (not shown) is energized.
2. Line contactor L₁ closes next. 
3. Motor starts on reduced voltage due to star connection of motor windings. 
4. At the end of time delay period, star contactor L₂ opens.
5. Immediately afterwards, contactor L₃ closes.
6. Motor now runs on full voltage and on delta connections.

Principle of Operation

operation of the star-delta starter is explained below: 

a) When the circuit breaker 52 is switched on, electrical power will be supplied to the transformer and the WL lamp will be lighted up.

b) To start the motor, push-button 3C is depressed and contactor coil 4X is energized. This will close normally-open contact 4X in the transformer primary circuit and energizing contactor coil 6.  In the meantime, normally open contact 4X in the transformer secondary circuit will also close thus energizing time-delay contactor coil 19T.

c) When contactor coil 6 is energized:

 Main contacts 6 in the main motor circuit will close to form the star connection.

1. Normally open auxiliary contact 6 will also close thus energizing contactor coil 88.
2. Normally closed contact 6 will open to act as an electrical interlock preventing contactor coil 88-1 from being energized.

d) When contactor coil 88 is energized:

i. Main contacts 88 in the main motor circuit will close and the motor begins to run in star connection.

ii. Normally-open auxiliary contact 88 will also close acting as a holding contact.

e) After the pre-set time delay:

1. Normally-closed contact 19T will open thus de-energizing contactor coil 6. This causes the star-connection to open and the normally-closed contact 6 to close back.

f) When contactor coil 88-1 is energized:

i. It will close the main motor circuit contacts 88-1; thus, the motor now runs in the delta connection.

ii. Holding contact 88-1 will also close.             

iii. Normally-open auxiliary contact 88-1 closes to light up the GL lamp.

iv. Normally-closed contact 88-1 will open to prevent contactor coil 6 from energizing thus acting as an electrical interlock.

 To stop the motor, depress push-button 3-0.

g) Protective devices installed in the circuit are thermal overload relay 51 and fuses.

Effect of Full Voltage Starting and Reduced Voltage Starting

1. With full voltage starting, as used in direct-on-line starters, very large current surges of 6 – 8 times full load current occurs.
2. With starting of large motors using direct-on-line starters, large voltage dip takes place. This voltage disturbance may result in malfunction of other electrical equipment connected to the supply.
3. Reduced-voltage starters, such as the star-delta starter or the autotransformer starter, are used to start large motors, e.g. cargo pumps and bow thrusters.                                                                                                               
4. With star-delta starters, the applied voltage is reduced to of the line voltage at start. If this is done, both starting torque and starting current are reduced to 1/3 of what they would have been had the motor been switched direct-on-line from the main.                                             

6. For example, suppose a squirrel cage motor is such that if switched on to the mains it develops 90% of its normal full load torque and takes 6 times its normal full load current from the mains. On star-delta starting, it would develop 90/3 i.e. 30% of its normal full load torque and takes 6/3 times its normal full load current.

Arc Chute:

Link: https://www.electricalclassroom.com/what-is-an-arc-chute/

Arc chute is a set of metal plates that are arranged in parallel and mutually insulated from each other, which can divide, cool and safely extinguish an electric arc. They are also known as arc splitters and arc dividers. Arc chutes can be found inside circuit breakers, contactors, isolators and other high current interruption devices.

On the basis of their operation, marine scrubbers can be classified into Wet and Dry scrubbers. Dry scrubbers employ solid lime as the alkaline scrubbing material which removes sulphur dioxide from exhaust gasses. Wet scrubbers use water which is sprayed into the exhaust gas for the same purpose.

Wet scrubbers are further classified into closed-loop or open loop scrubbers. In close looped scrubbers, fresh water or sea water can be used as the scrubbing liquid. When Fresh water is used in closed loop scrubbers, the quality of water surrounding the ship has no effect on the performance and the effluent emissions of the scrubber. Open-loop scrubbers consume sea water in the scrubbing process.

Hybrid scrubbers can utilise both closed and open running modes either at the same time or by switching between the two. Seawater hybrid scrubbers can be operated both in closed or open mode with seawater used as the scrubbing medium.

Wet Scrubbers 

Inside a wet scrubber, the scrubbing liquid used may be sea water or fresh water with chemical additives. The most commonly used additives used are caustic soda (NaOH) and Limestone (CaCO3). Scrubbing liquid is sprayed into the exhaust gas stream through nozzles to distribute it effectively. In most scrubbers the design is such that the scrubbing liquid moves downstream, however, scrubbers with an upstream movement of scrubbing liquids are

The exhaust inlet of the scrubber can be made in the form of a venturi, as shown in Figure 2.1, in which the gas enters at the top and water is sprayed in the high exhaust gas speed areas at the neck or above the neck in the form of a spray. An inline scrubber is shown in figure 2.2.

The exhaust intake is either on the side or the bottom of the tower. The designs ensure that the sulphur oxides present in the exhaust are passed through the scrubbing liquid; reacting with it to form sulphuric acid. When diluted with alkaline seawater, sulphuric acid which is highly corrosive in nature can be neutralised.

The wash water is discharged into the open sea after being treated in a separator to remove any sludge from it and the cleaned exhaust passes out of the system. Mist eliminators are used in scrubbing towers to remove any acid mist that forms in the chamber by separating droplets that are present in the inlet gas from the outlet gas stream.

Figure 2.2

MARPOL regulations require that the wash water used has to be monitored before being discharged to ensure that its PH value is not too low. Since the alkalinity of seawater varies due to the number of reasons such as the distance from land, volcanic activity, marine life present in it etc, wet scrubbers are divided into two types; open loop and closed loop systems. Both these systems have been combined into a hybrid system, which can employ the most suitable scrubbing action depending upon the conditions of the voyage.

Open Loop Scrubber System 

This system uses seawater as the scrubbing and neutralising medium, no other chemicals are required for desulphurization of gasses. The exhaust stream from the engine or boiler passes into the scrubber and is treated with only alkaline seawater only. The volume of this seawater depends upon the size of the engine and its power output.

Related Read: Understanding Components and Design of Exhaust Gas System of Main Engine On Ship

The system is extremely effective but requires large pumping capacity as the amount of seawater required is quite high. An open loop system works perfectly satisfactorily when the seawater used for scrubbing has sufficient alkalinity. However, sea water which is at high ambient temperature, fresh water and even brackish water, is not effective and cannot be used. An open loop scrubber for these reasons is not considered as a suitable technology for areas such as the Baltic where salinity levels are not high. 

Reactions Involved:

SO2 (gas) + H2O + ½O2 → SO4 2- + 2H+ (Sulphate ion + Hydrogen ion)
HCO3– + H+ → CO2 + H2O (Carbon-di-oxide + Water)

Advantages:

1. It has very few moving parts, the design is simple and easy to install on board.
2. Apart from de-fouling and operational checks, the system requires very less maintenance
3. This system does not require storage for waste materials

Disadvantages:

1. Cooling of the exhaust gas is a problem faced by wet scrubber systems.
2. The operation of the system depends upon the alkalinity of water available and is not suitable to be employed in all conditions.  
3. A very large volume of sea water is required to obtain efficient cleaning and hence the system consumes very high power.  
4. In ECA zones and ports, higher costing fuel has to be consumed.

Closed Loop Scrubber System 

It works on similar principals to an open loop system; it uses fresh water treated with a chemical (usually sodium hydroxide) instead of seawater as the scrubbing media. The SOx from the exhaust gas stream is converted into harmless sodium sulphate. Before being re-circulated for use, the wash water from a closed loop scrubber system is passed through a process tank where it is cleaned.

The process tank is also needed for the operation of a circulation pump that prevents pump suction pressure from sinking too low.

Ships can either carry fresh water in tanks or generate the required water from freshwater generators present on board. Small amounts of wash water are removed at regular intervals to holding tanks where fresh water can be added to avoid the build-up of sodium sulphate in the system.

A closed-loop system requires almost half the volume of wash water than that of the open loop version, however, more tanks are required. These include a process tank or buffer tank, a holding tank through which discharge to sea is prohibited and also a storage tank capable of regulating its temperature between 20º and 50ºC for the sodium hydroxide which is usually used as a 50% aqueous solution  

Dry sodium hydroxide also requires large storage space. The hybrid system is a combination of both wet types that can operate as an open loop system when water conditions and the discharge regulations allow and as a closed loop system at other times. Hybrid systems are hence proving to be the most popular because of their ability to cope with different conditions.

Reactions Involved

2NaOH + SO2 → Na2SO3 + H2O (Sodium Sulphite);
Na2SO3 +SO2 +H2O → 2NaHSO3 (Sodium Hydrogen Sulphite);
SO2 (gas) + H2O + ½O2 → SO42-  +  2H+ ;
NaOH + H2SO4 → NaHSO4 + H2O (Sodium Hydrogen Sulphate);
2NaOH + H2SO4 → Na2SO4 + 2H2O (Sodium Sulphate).

Advantages:

1. Very less maintenance is required.
2. It is independent of the operating environment of the vessel.
3. Cooling of exhaust gas is a problem with wet scrubbing systems.

Disadvantages

1. It requires storage space (buffer tank) to hold waste water until it can be discharged
2. Selective catalytic reduction systems must operate before wet scrubbers.
3. Fitting the system together, especially for dual-fuel engines can be quite complex.

Hybrid Scrubber System

These systems offer a simple solution for retrofitting vessels with scrubbers that are capable of operation on both open loop and closed loop configurations. These systems run on open loop mode at sea and closed loop mode in ECA zones and ports and their use can be switched with ease. As the system can run on lower costing fuels for longer periods of time and around the world, they can overcome their high initial costs in order to economically meet with the international regulations.

Advantages:

1. Suitable for long and short voyages around the world
2. Ships with Hybrid scrubbing systems can spend more time in ECA zones and on port than those with open loop systems
   3. Can use lower costing HFO (Heavy Fuel Oil) all of the time.
   
   

Disadvantages

1. More structural modifications are needed to employ this system.
2. Requires large storage space for chemicals and additives.
3. The system has a high installation time and cost.

Dry Scrubbers

In these types of scrubbers, water is not used as a scrubbing material, instead, pellets of hydrated lime are used to remove sulphur.

The scrubbers are at a high temperature than their wet counterparts and this has a benefit that the scrubber burns off any soot and oily residues in the system. The calcium present in caustic lime granulates reacts with the sulphur dioxide in the exhaust gas to form calcium sulphite.

Calcium sulphite is then air-oxidized to form calcium sulphate dehydrate, which with water forms gypsum.  The used pellets are stored on board for discharge at ports, however, they are not considered a waste as the gypsum formed can be used as a fertiliser and as construction material.

Dry scrubber systems consume less power than wet systems as they do not require circulation pumps. However, they weigh much more than wet systems.

Reactions Involved

SO2 + Ca(OH)2 → CaSO3 + H2O (Calcium Sulphite)
CaSO3 + ½O2 → CaSO4  (Calcium Sulphate)
SO3 + Ca(OH)2 → CaSO4 + H2O (Gysum)

Advantages

1. There is efficient removal of nitrogen and sulphur oxides
2. This type of system does not result in the production of liquid effluent that must be disposed of overboard.
3. The Gypsum obtained after the exhaust gas cleaning process can be sold for use in various industrial applications

Disadvantages

They require significant onboard storage to handle the dry bulk reactants and products associated with the process.
There must be a readily available supply of the reactants.
the reactants used are costly, especially urea for NOx abatement and calcium hydroxide for SOx abatement

Classification of fire:

Lube oil sampling procedure?

• Draw samples from a connection that comes directly out of the main oil supply line to the engine.
• Always sample for the same point.
• Sample only when the oil is up to its operating temperature with the engine running.
• Depending upon the draw off point, sufficient amount of oil should be drained out of the line prior to drawing the sample.
• The sample should be filled into a chemically cleaned container after it is rinsed with sample oil and immediately closed.
• The container should be attached with a label as follows:

 Records for Sample

1. Date of sample drawn
2. Point of sample drawn
3. Temperature of sample drawn
4. Type of oil
5. Type of machinery use
6. The period of time since the last renewal of oils.

Avoid sampling from places where the oil may be stagnant or have little or no flow, such as sumps, auxiliary smaller pipelines, purifier suction or discharge lines, drain cocks of filters, coolers etc.

Also avoid sampling while engine is stopped.

Microbial Degradation of lubricating oil

.microbial degradation

Stagnant lube oil for long periods in humid conditions can result in bacterial growth due to the presence of water

Indication

• Oil appearance looks slimy and greyish and is indicated by the ‘rotten egg’ odour

Prevention

• Oil must be heated and circulated periodically especially when a ship is laid up

Lube oil properties

.aecc lo .aux eng lo .ae lo

.lo properties   .lop

1. High oxidation and thermal resistance to perform at elevated temperatures.
2. High Viscosity index so that it does not vary much with temperature.
3. Appropriate viscosity to meet liner lubrication as well as bearing lubrication 12cst at 100 degree
4. High detergency properties so that it softens and takes away all the deposits formed
5. High dispersancy properties so that it keeps all the deposits in suspension so that it can be removed easily by purification.
6. Higher flash point as it comes into contact with the combustion gases degree
7. TBN value according to sulphur content in fuel   10-30 mgKOH/g
8. Antifoam properties as the oil tends to have higher deposits
9. Extreme pressure and anti-wear additives for maintaining boundary lubrication between piston rings and liner

b) Analyze the condition of this oil

Viscosity: 

106

Viscosity can increase due to-

• High insoluble content
•  HFO contamination due to leaky injectors, worn fuel p/p plunger & barrels
• Piston blow past
• Oxidation due to ageing & high operating temp
• Water contamination (emulsification)

For information: viscosity can decrease by gas oil contamination during prolong running in ECA area.

Density: 

0.95

Density can increase due to-

• High insoluble content
•  HFO contamination due to leaky injectors, worn fuel p/p plunger & barrels
• Piston blow past
• Water contamination (emulsification)

Flash point:

240 degree C

Flashpoint can reduce, Main suspect FO contamination due to

1. leaking injectors, improper combustion, blow-past,
2. worn fuel pump plungers & barrels
3. Min. 180 deg C

Water:

Should be 0.

Presence of water with trace of chloride Due to

• Bilge leakages likely through

• Crankcase breather pipe condensation as atmosphere has saline nature
• Inefficient operation of purifier
• Possible but do not suspect leakages due to steam or engine cooling water leakage as this may increase the base number
• allowable FW content max 0.2%, for short period 0.5%

Ash: 

4 mg/kg

Can Increase due to –

•   HFO contamination due to leaky injectors, worn fuel p/p plunger & barrels
•   Blow past
•   Rust in the sump tank

Base number:

30

Can reduce due to                   

• Insufficient oil volume in circulation  
• Irregular top up of sump
• Fuel contamination and sulphur in HFO can reduce TBN
• Max +100%, min -30% of initial value.

Insoluble: 

Max 2%.

The amount of insoluble ingredients in the oil is checked as follows.

• Equal parts of oil samples are diluted with [Toluene/benzene] and [pentane / heptane].
• As oxidized oil is only soluble in benzene and not in pentane or heptane the difference in the amount of insoluble is indicatives of the degree of oxidation.

Pentane /heptane Insoluble:

• Indication of oxidation & the metallic deposits/ solid contaminant present
• Max 2% 

Toluene/ benzene insoluble:

• Indication of the solid contaminants
• Max 1%

P/H –T/B insoluble:

3 –1.5 = 1.5 is the Indication of the rate of oxidation that has taken place

Limit max. 1%

Main possibility due to                     iia

• Insufficient volume
• Improper top-up
• Ageing of oil

Batch Purification

.bp   .batch purification

.batch purification

 When it is done

1.  Insoluble content is too high
2.  Recommended in Lub oil analysis report.
3.  Routinely carried out in dry Dock.

Before commencement transfer in settling tank

1.  Discusses with master and technical superintendent
2.  Job risk assessment to be carried out
3.  Work permit to be taken
4.  Immobilization permit to be taken
5.  Ensure the Lube oil settling tank is empty.
6.  Open the manhole door for setting tank.
7.  Carry out proper ventilation
8.  Follow enclosed space entry permit for settling tank.
9.  Clean the setting tank with lint-free Rags.
10.  Settling tank walls and top should be free of rust.
11.  Settling tank heating coil tried out confirm no leakage.
12.  Drain cock is functioning well

Before purification procedure

1. Use the lub oil transfer pump to transfer enter sump oil to the settling tank.
2. Take a sample at setting tank for on-board test for water, TBN and viscosity.
3. Note down the value for this test.
4. Open steam heating to the settling tank and set temperature 60 to 70 degree Celsius 
5. Allow oil to settle for at least 24 hours
6. Drain the tank frequently until water stops coming out

Purification

1. Start settling tank to settling tank purification.
2. Keep purifier feed rate at minimum on 1/3 of maximum capacity.
3. Continue purification as long as time permits.

Sump cleaning

1. Open up the void tank manhole cover 
2. Carry out ventilation for few hours.
3. Follow the enclosed space entry permit procedure for void tank.
4. Take portable oxygen gas detector, before entry into enclosed space calibrate in atmosphere condition.
5. One responsible person must standby outside enclosed space
6. Communication must be established with the person outside and the person in bridge.
7. After inspection void tank open the manhole cover for sump tank.
8. Carry out ventilation of sump tank and follow enclosed space entry procedure separately.
9. Entre the sump tank for cleaning.
10. Scoop all the sludge and use lint free rags to clean the tank with emphasis on the bottom of the tank.
11. Box up the sump tank manhole cover after cleaning.

Transfer LO to sump

1. Take a sample at settling tank and carry out on-board test. If the test is satisfactory or engine needs to be ready, start purifier from settling tank to sump tank.
2. The void tank manhole cover to be closed only after the sump tank is filled and its manhole has no leakage.
3. Mean time clean all LO filters in the system.

Onboard Lube Oil Tests

.lo test

.lube oil test

For all types of lube oils on ships, following Lube oil tests are carried out:

1. Water Content test

5 ml of sample is taken inside digital water content meter mixed with 15 ml of reagent containing paraffin or toluene. Before closing the lid of the digital meter, a sealed sachet containing calcium Hydride is kept and container closed tight. The meter is shaken by hand and the pressure rise due to the chemical reaction in the test container is shown as water percentage in the digital display.

2. pH Test

It is done by using a pH paper which changes colour once in contact with oil and it is then compared with standard values. This test determines the reserve alkalinity of the oil sample.

3. Viscosity Test

This test is performed by using a Flow stick in which two paths are provided for flow of oil side by side. In one path fresh oil is filled and in other side path used sample oil is filled. Now the flow stick is tilted allowing oil on both paths flowing in the direction of the tilt due to gravity. A finish point is provided along with reference points along the flow stick and the position of used oil is checked when fresh oil reaches the finish point.

Q. During watch main engine lube oil level go down, what are your actions?

• Check lube oil sump tank level manually, confirm actual level.
• If low, check for possible lube oil leakages
• Check lube oil purifier
• Check under piston space drain for piston cooling oil leakage.
• Check lube oil pump for possible leakages
• Stop engine if problem found in main engine component and rectify.
• If problem in LO purifier, stop purifier and clean it.

Q. Difference between Stern tube lube oil and crankcase oil

.mecc oil .stern tube oil .st oil

ME crankcase oil	Stern Tube Lube Oil
Excellent thermal and oxidation stability and detergency	Good corrosion protection
Excellent deposit control of oil-cooled piston under crown	Excellent wear protection for gears and Bearings
Excellent detergency (Clean crankcase)	Excellent viscosity temperature behaviour, high viscosity index (VI)
Excellent dispersancy -Extended oil life due to efficient water separating properties ()	Miscible with mineral oil and polyalphaolefin gear oil
Rust and corrosion properties (anti-oxidant)	Natural dissolving properties
Good wear protection	Highest shear stability
Approved by major engine manufacturers	Based on renewable resources
alkalinity is sufficient to neutralize crankcase contamination (TBN)	Rapidly biodegradable (> 60% acc. to OECD 301 B)
	High resistance to ageing
	Good air release
	Good foaming properties
	Optimally suited for high and low temperature Use

LO Emulsification:

.lo emulsification .emulsification .lubricating oil emulsification

Lube Oil Emulsification:

Definition:

– When water is dispersed/penetrated lube oil in the form of small droplets.

– Water droplets remain in an oil layer in a stable form

– Properties of emulsified oil are very different from pure oil

Indications:

1. Stable water content after purification

2. Unusual smells (Rotten eggs)

3. Sliminess of the oil, apparent in crankcase with paint discoloration/removal

4. Heat exchanger performance falling

5. More frequent filter/valve clogging

6. Pitting of tank surface (sump tank)

7. Corrosion of unprotected steelwork, journals, fuel pipes, injector (4 stroke engine)

Causes:

1. Water contamination due to leakages in:

   – Exhaust v/v

   – Liner

   – Cylinder Piston (if water cooler piston)

2. Using wrong gravity disc in L.O. purifier

   – Maintain oil-water interface too close to clean oil outlet

3. Condensation due to high humidity

4. Leakage through sump diaphragm due to over tightening or fretting

5. Leakage of bilge:

   – Through sounding gauge

   – Through expansion bellows fitted between engine & tank top

6. Leakage of L.O. cooler (Tube or gasket)

7. Purifier sealing water solenoid valve leaking

8. Mist box drain choked or Rainwater accumulation in mist box

9. Lube oil purifier steam heater leakage.

Effects:

1. Deterioration in lube oil properties

2. Reduction in load carrying capacity.

3. Reduction in cooling effect.

4. Sludge formation

5. Corrosion in various parts of machinery

6. Worst of all leading to microbial degradation

Corrective/Preventive Actions:

1. Identify & rectify the actual source of leakage (root cause)

2. Centrifuge at optimal throughput and maintain temperature at about 80°C

3. Monitor through shipboard lube oil test for water

4. Batch purification at 1st opportunity

Batch Purification Procedure:

1. Discuss with master & technical manager

2. Immobilization permission

3. Risk assessment carried

4. Discussion in toolbox meeting

5. Relevant work permit to be made

6. Proper ventilation of L.O. settling TK

7. Enclosed space entry permit before entering L.O. sett TK

8. Inspect L.O. sett. TK (Top & walls should be rust free)

9. Clean with lint free rags

10. Sett TK heating coil to be pressure tested for leakage

11. Sett. TK drain cock must be functioning properly

12. Transfer all sump oil to sett. TK from sump by using L.O. transfer p/p

13. Take a sample from sett. TK for onboard lube oil test for water, TBN, Viscosity & spot test

14. Note down the values of this test

15. Steam open for sett TK heating. Maintain temp. 60-70°C

16. Allow oil to settle at least 24 hours

17. Drain the TK frequently until water stops coming

18. Clean the purifier before use & monitor

19. Start purification from sett. to settling TK

20. Keep purifier at optimal throughput and temperature at about 90°C

21. Continue purification for as long as time permits

22. If onboard test result come satisfactory, send sample for lab analysis for detailed test

Sump Cleaning:

1. Open void tank manhole cover & do proper ventilation

2. Prepare enclosed space entry permit upon satisfactory gas test

3. Enter void tank and open sump tank manhole cover

4. Again do proper ventilation & enclose space entry permit made after gas test

5. Enter lub oil sump tk for cleaning

6. Scoop off all the sludge & use lint free rags to clean tank with emphasis on the bottom and loose rust at the ceiling

7. Box up sump tk manhole door

8. Void tk manhole cover to be closed only after sump tk is filled and its manhole has no leakage

9. Take sample from L.O. sett. tk for shipboard lube oil test. If test result is satisfactory and engine needs to be ready, start purification from setting to sump tk

10. Simultaneously, clean all lube oil filter & coolers in the system

11. Update the work done on PMS. Make enough photographic evidence

12. Make a clear report & send it to office

Vessel Options:

1. Upon satisfactory test result from onboard test & shore analysis, discussing with office, vessel may use the oil from sett. TK or dispose it

   – Can add partial amount of fresh new oil upon office approval

2. Use fresh batch of new oil with complete charge in sump

Note: It is advisable to use one or more crankshaft bearings at earliest opportunity if the symptoms of emulsification are visible.

.bdn regulation

A Bunker Delivery Note (BDN) is the standard document required by Annex VI of MARPOL, which contains information on fuel oil delivery. It is the responsibility of the fuel oil suppliers to provide the bunker delivery note, which must remain on the vessel, for inspection purposes, for a period of three years after the fuel has been delivered.

BDN information

The following information must be included in the BDN to comply with global standards:

1. Name and IMO number of receiving vessel
2. Name, address and telephone number of fuel oil supplier
3. Port of bunkering
4. Date of commencement of delivery
5. Delivered product name(s)
6. Quantity in metric tons
7. Density at 15 degrees Celsius
8. Sulphur content
9. the seal number of MARPOL sample label must be included for cross-reference purposes

A declaration signed and certified by the fuel oil supplier’s representative that the fuel oil supplied is in conformity with MARPOL Annex VI

Port State Control has the authority to board the vessel to inspect and make copies of the BDN to verify that the fuel complies with global and local regulations.

Fuel Oil Change Over

Some ports have regulations of using gas oil for generators and boilers while the ship is at port (for e.g. European ports). Change over generators and boiler to diesel oil with sulphur content less than 0.1 %.

Boiler

• Shut the steam to the fuel oil heaters of the boiler
• When the temperature drops below 90 degrees, open the diesel oil service tank valve going to the boiler system
• Shut the heavy oil valve for the boiler system slowly and observe the pressure of the supply pump
• Check flame and combustion of the boiler
• Let the heavy oil outlet be kept open and diesel oil outlet is not open for some time
• This is to ensure no heavy oil goes to the diesel oil system
• When the line is flushed with Diesel Oil, open the diesel outlet valve and shut the heavy oil outlet valve

Generators/ Auxiliary Engine

Generators must be changed over from one grade to another while at load as this will help in better flushing of the system. If only one generator is being changed over, keep running another generator for emergency purposes in case something goes wrong.

• Shut the steam to the fuel oil heaters of the boiler
• When the temperature drops below 90 degrees, open the diesel oil service tank valve going to the generator system
• Open the local diesel inlet valve and shut the heavy oil inlet valve simultaneously and slowly, by keeping an eye on the fuel pressure and changing only one generator into diesel with the help of a separate diesel pump. Let the heavy oil outlet be kept open and the diesel oil outlet kept shut till the system is flushed thoroughly
• After some time open the diesel oil outlet and shut the heavy oil outlet
• If the complete system is to be changed into diesel oil, open the diesel oil inlet valve to the generator supply pump simultaneously closing the heavy oil inlet valve
• If the return line is provided to the diesel service tank, open it after some time, simultaneously closing the heavy oil return only after the system is flushed properly

The changeover procedure must include recording of every action and onboard oil quantity as proof of doing the job correctly.

Note: Once the changeover procedure is completed, remember to change the HMI setting of the Cylinder oil lubricator system (Alpha lubrication) or change over the cylinder oil daily tank suitable for low sulfur operation.