Environmental and Safety Systems/Devices Flashcards
State the safety checks needed before using EACH of the following lifting gear:
a) Wire strops,
b) chain blocks,
c) eye bolts,
d) shackles. (4 each)
Safe and successful lifting operations depend, in large part, on the continued safety of the lifting equipment and accessories that are used. Failures in this kind of equipment can result in significant or even fatal injuries. Health and safety law therefore places a number of specific obligations on those providing, controlling, and using lifting equipment to properly manage these risks. All lifting equipment comes under Lifting Operation & Lifting Equipment Regulations 1998 (LOLER). All equipment should be inspected before use.
a.) a) That the appliance has been tested, no visible signs of damage and is correctly rated. Visual inspection for damage, SWL stamp, broken wires/crushed wires & damage to any fitted eyelets.
b.) Tested, operates in both directions, does not slip, no visible damage and is correct size.
Visual Examination for damage to casing, ensure chain block is free to move, check SWL, inspect both lifting hooks for condition and function of hook safety latch.
Additionally make the following checks:
Check neck for twisting.
Check for wear and cracks.
Check throat opening is greater than 15%
Check tip for twisting (greater than 10deg)
Check pin for bending.
Ensure pin is seated and check opening width.
c.) Tested, threads not damaged and correct size, correct weight rating, no visible damage.
Inspection of threads for damage, lifting eyelet for cracks and damage, landing face for damage and SW stamp. Also make the following checks:
Check for markings.
Check for deformation.
Check inside of eye for wear.
Check for cracking.
Check thread centre is in line with centre of eye
Check thread for corrosion.
d.) Tested, of correct load rating, no visible damage. Inspection of thread/locking device if fitted. Ensure pin is free in shackle, inspection of crown/pin for wear/cracks/distortion. Ensure pin is correct and there isn’t too much material reduction. Ensure its not bent, twisted, or stretched and there isn’t excessive amount of corrosion.
Describe the routine checking of a compressed air breathing apparatus (CABA) set.
The facemask and seal should be checked to ensure in good condition. The supply pipe should be in good condition. The pressure gauge lens must be clear and easy to read and indicate correct reading. The whistle should be attached. Check the certification on the back plate. The bottle should be working at correct pressure, shouldn’t fall to 0 within 30 seconds. Ensure no leaks by sound. Do pressure down test and ensure whistle sounds. All straps are secure and in good condition. Check transparent window, belts, sealing parts, inhalation valves and exhalation valves of full face mask and check the connections of supply valves and face mask . Every part must be clean without dirt or polluted by acid, alkali, oil or any harmful material, and transparent window must be clean. check pressure reducer is working and its tight to reduce air from around 300bar to 5-11bar. all these tests should be made regularly even when equipment is on standby
list the 3 main types of breathing apparatus and briefly describe one of them.
There are 3 main types of
Breathing Apparatus –
Escape,
Self-Contained,
Airline.
Emergency Escape Breathing Apparatus (EEBD)
A self-contained compressed air apparatus for escape from a contaminated environment. It consists of a compressed air cylinder with air capacity of 600 litres (15 minutes duration). Within accommodation areas all ships are to carry at least two EEBD. The quantity of EEBD within machinery spaces is dependent on the layout of the space and the number of persons normally working there. There are many different types, but all are to be used for escape purposes only!
With reference to main engine crankcase explosions:
a) state TWO causes (8)
b) explain how the effects are minimised. (8)
a.) hot spots provide the necessary heat for ignition of vapour, and then a primary explosion can occur.
The primary explosion causes a shock wave to propagate inside the crankcase.
This shock wave has a breaking effect on the size of oil droplets, producing more fuel for ignition. the pressure on front is followed by a low pressure area which tries to suck in more air from outside.
Air would be able to enter in the scavenge space through leaky relief valves. The new air and new supply of fuel produced after first explosion comes in contact with hot spot, which causes secondary explosion, which is extremely severe as the amount of fuel has increased . This explosion then causes severe damage to engine plating.
b.) How to prevent the crankcase explosion ?
To minimize the formation of explosive breather pipe to vent crankcase pressure out of the engine or exhaust fan is fitted on crankcase.
To prevent the formation of hot spot in the crankcase, the bearings should be in correct running clearance, lubricating oil should be adequately supplied to bearings and other running parts. The piston with rings and cylinders should be in safe working limits. There should be adequate cooling of the engine.
there should be Proper purification and analysis of lube oil and Lube oil filters to be changed over & cleaned as per schedule.
Ensure proper cylinder lubrication by checking the condition of piston, piston rings and liner through scavenge ports.
Clean scavenge space as per schedule & drain scavenge space regularly. All running gears maintenance & checks to be carried out as per PMS.
Be alert and rectify any abnormal noise in crankcase. All safety trips & alarms fitted on M/E to be tested
With reference to conditions which may cause an explosion in the crankcase of a large marine diesel engine:
a) state FOUR possible sources of ignition (8)
b) state TWO methods which can be used to detect a potentially dangerous
situation within the crankcase (4)
c) state TWO other indications which could signify a possible dangerous
situation within the crankcase. (4)
a.) 1. Hot spots on bearing surfaces.
Hots spots occur at 280 to 400deg Celsius above the LO flash point. Hots spots will provide the necessary heat for
ratio of vapour to air reach the range of flammability followed by a potential explosion.
- stuffing box and or Insufficient lube oil flow to bearings which then causes sparks from metal-to-metal contact
- Hot gases blowing past broken pistons can provide heat sufficient enough to cause an explosion in the trunk type piston engines.
- scavenge space fire if reaches large enough level can cause crankcase explosion followed by fuel contamination of the Lub Oil.
b.) - irregular running of engine and or abnormal noise in crankcase and bearing LO temperature increase which can be spotted when carrying out engine room safety rounds during watch.
OMD Alarm will activate when oil mist concentration reaches LEL levels of 2.5 – 5%.
c.) 1. High exhaust gas bearing temperatures and Crankcase pressure increase
- smell and appearance of dense oil mist when u open crankcase breather pipe and drain cock or by noticing a temperature increase by hand feel of crankcase doors
a) State the name of the equipment used to give a warning of the presence of conditions that could lead to an explosion in the crankcase of a diesel engine. (2)
b) Sketch and describe the device used to relieve any excess pressure that might develop as a result of a crankcase explosion in a diesel engine. (14)
a.) OMD will sample the atmosphere within the crankcase to give a warning for when a crankcase explosion could occur. it uses a light source and a photo electric cell (PEC) to measure the atmosphere for the amount of oil droplets present. when amount has reached sufficient conditions it will trigger an alarm and then automatic shut down will occur for a four stroke engine or a automatic slow down for a 2 stroke engine.
b.) crankcase explosion relief valve
SEE ORAL/IAMI Sketch Pack for drawing
During normal conditions the spring seals the valve. In the event of an excess of pressure caused by an explosion due to a large fire the spring operated valve gets pushed down and overcomes the spring force for a brief period to relive the pressure from the fire and escape by the deflector and then deflector is resealed. the deflector has to be resealed because otherwise outside air would feed the fire and cause a secondary explosion. Oil wetted gauze fitted stops the flame being expelled from open valve, the guide fitted safely allow the high force from fire downwards to the deck plates.
a.) what are quick closing valves?
b.) outline how to test quick closing valves
c.) provide examples on ship of where quick closing valves are fitted?
a.) Quick Closing Valves are shut off valves that are designed to isolate oil tanks in the event of a fire and also to prevent fuelling of a fire in case of a piping system and its components failure. These valves are designed to be remotely operated from a designated place on-board vessel (Fire Control Station) and they must be kept in good working order and ready to use at all times with no exception. All the outlet valves from the fuel oil and lubricating oil tanks, from which oil could flow to feed a fire, are equipped with hydraulically or pneumatically operated quick closing valves. The quick-closing valves are closed by pulling on a handle which operates a piston in a hydraulic or pneumatic cylinder. The action of the piston is transmitted to the collapsing mechanism of the associated valve or valves, causing the valve to move to the closed position under the force of a spring. After a valve has been tripped by means of the quick-closing device it must be reset locally. This is done by turning the hand wheel to close the valve, then turning the hand wheel in the opposite direction to reopen the valve. Before reopening the valve, the air supply line to the tripping mechanism must be vented and a check must be made to ensure that the collapsing mechanism is correctly repositioned.
b.) Quick closing valve test.
Quick closing valves are activated by turning the three-way valve in the line to the valve actuators. This sends compressed air to the quick closing valve actuators which trips the valve causing it to close under the force of the spring. The quick closing air reservoir is supplied with the compressed air from the control air system and the inlet valve to the reservoir should, under normal operating conditions, be locked in the open position. There is a drain valve on the air reservoir and this should be opened at regular intervals to remove any water which may be present. Operation of the quick-closing valve system should be tested at monthly intervals or in accordance with the company’s operating procedures to ensure that the valves function correctly. Operation of the quick-closing valves is essential to the safety of the vessel. Testing of the quick-closing valves should be carried out when the closing of the valves will not impede the operation of the vessel. In addition to operating the quick closing valves, the air system also supplies the pneumatic cylinders which keep the engine room fan dampers in open position.
c.) In most cases a single hydraulic cylinder or pneumatic valve lever will operate a group of valves either on the same tank or on tanks which are located close together. Diesel generator engines and sometimes main engine have their own quick-closing valve handles allowing individual diesel generator or main engines to be shut down, by closing the fuel inlet valve to the engine, should that be necessary. The emergency generator has a quick-closing valve on its fuel tank and this is closed by means of hydraulic cylinder handle, pneumatic valve or a wire link located outside the emergency generator room. There are some tanks, such as some LO tanks, which are not equipped with quick closing valves as their valves are assumed to remain closed when the tank is not in use.
what is the purpose of fire dampers?
Fire dampers are fitted for air discharge from the engine room and they need to close the ventilation openings in the event of a fire in the engine room spaces. The dampers are kept open by air pressure supplied from the control air system. The dampers either have a counterweight attached to the damper linkage which ensures that the dampers close when the air pressure acting on the pneumatic cylinder is released, or are of the multi-blade type, whereby the dampers are linked and thus all close the damper when the air is vented from the cylinder. In the case of the large fire flaps being fitted, the weight of the fire flap alone is sufficient to ensure closure and there is no need for additional counterweight.
how to test and operate fire dampers.
All fire flaps may be closed locally by operation of a three-way vent valve to vent the pneumatic cylinder. If this vent valve is used to close the fire flap, the fire flap may be opened again by turning the valve back to the open position which allows an air supply to the operating cylinder. Vent valves are located, usually, at the port and starboard sides of the accommodation block on deck. They can also be operated through wire links and in this case the flap will close under its own weight once the wire has been unleashed from its normal resting position. Fire dampers should be tested at weekly intervals or in accordance with the company’s operating procedures to ensure that the dampers function and close correctly. Operation of the fire dampers is essential to the safety of the vessel and testing of should be carried out diligently and carefully independent of the vessel being at sea or in port. Fire flaps can also be operated remotely by means of pushbuttons, levers or wire handles located in the fire control station (inside accommodation) and at the operating board situated outside the accommodation on deck.
what’s the purpose of emergency stops?
Emergency stops are available in order to stop the equipment, pumps and fans and to close valves in an emergency and they are provided in the fire station, on deck or at the engine room entrance. They must not be confused with the remote stops which are available for stopping some pumps when carrying out normal ship duties. For example, emergency stop push-buttons are provided at the bunker stations for stopping the MDO and HFO transfer pumps or sludge pump, when using these pumps to pump oil or sludge ashore. The emergency stop switches are located under a cover or inside a locked box in order to prevent accidental operation. Usually, the emergency stops should be tested at 3 monthly interval or in accordance with the company’s operating procedures to ensure that the emergency stops work correctly. Operation of the emergency stops is essential to the safety of the vessel and testing of should be carried out diligently and carefully without impeding with vessel normal operations (emergency stops should not be tested during manoeuvrings as this can lead to vessel black out and accidents) .
Explain what are EEBDs and what maintenance is carried out for them?
Emergency Escape Breathing Devices are designed to provide a reliable source of breathable air in the event of emergencies such as fire, toxic gas release, or any other situation where the ambient air becomes hazardous. These compact, self-contained devices typically consist of a hood or mask connected to a compressed air cylinder. EEBDs include a quick and easy activation mechanism, providing a rapid supply of breathable air for a specified duration. EEBDs are designed to be user-friendly, allowing crew members to use the device swiftly and easily, even in low visibility or high-stress situations. The effectiveness of EEBDs lies in their ability to deliver a controlled flow of breathable air, enabling individuals to escape hazardous environments safely. Ensuring the reliability of EEBDs requires regular maintenance practices onboard vessels. Periodic inspections, conducted according to manufacturer guidelines and regulatory requirements, are essential to verify the integrity of each device. Common maintenance tasks include checking the pressure in the compressed air cylinders, inspecting the condition of the hoses and masks, and replacing components that have exceeded their service life. Regular drills and training sessions for crew members are crucial to familiarize them with the proper usage and maintenance procedures of EEBDs. This proactive approach contributes to a well-prepared crew, capable of responding effectively in emergency situations. The vessel crew play a role in the safe use and maintenance of EEBDs. Crew members should be well-trained in the correct procedures for donning, activating, and maintaining these devices. Regular drills and training exercises simulate real-life emergency scenarios, ensuring that the crew is adequately prepared to handle challenging situations. During emergency situations, crew members must remain calm and follow established procedures when using EEBDs. Proper communication and coordination are vital to ensure a swift and organized evacuation. Crew members should also be aware of the location of EEBDs throughout the vessel and understand the escape routes to expedite the evacuation process.
describe the working principle of a open loop, closed loop and hybrid scrubber system?
Open loop scrubber system
Working principle of an open loop scrubber system is the following.
1.Exhaust gasses enters through the bottom of the scrubber.
2.Seawater flows through the top of the scrubber and enters as a spraying mist through the nozzles this produces an equally divided spray throughout the scrubber.
3.Sulphur particles in the exhaust gas attach to the water droplets due to the temperature and process.
4.Cleaned exhaust gas leaves through the top of the scrubber.
5.The seawater then leaves through the bottom and is discharged overboard.
Closed loop scrubber system
Working principle of a closed loop scrubber system is the following.
1.Water goes through the circulation tank.
2.NaOH or CaCO3 is added to the process water to neutralize acidity.
3.Cleaned water is then pumped upwards again to the top of the scrubber.
4.Polluted water is drained and goes through the separator.
5.Solids and oil are removed from the polluted water forming sludge.
6.Sludge is pumped to the sludge storage tank on the ship.
Hybrid scrubber system
Working principle of a hybrid scrubber system is the same as the open loop and closed loop type scrubber system because it can switch between the two. The of often run on open loop operation mode at sea and closed loop operation mode in ECA zones. The system generally has high installation costs but once installed fuel that costs less can be used for a long time.
what are scrubbers?
Scrubbers are air pollution control devices that use liquid to remove particulate matter or gases from exhaust emissions. There are two types of scrubber’s wet scrubbers and dry scrubbers. In wet scrubbers’ processes, liquid or solid particles are removed from exhaust gas by transferring them to a liquid. In dry scrubbers’ water is not used as a scrubbing material instead pellets of hydrated lime are used to remove sulphur. There are two types of scrubbers wet and dry. The main working principle for both scrubbers is the same, wash the exhaust gas using a chemical before emissions are released into the atmosphere.
what are the advantages and disadvantages of scrubbers
Advantages
Scrubbers will enable the vessel to use less expensive and a higher sulphur fuel while maintaining emission standards set by IMO-2020 emissions cap.
Scrubbers are able to remove about 98% of sulphur.
little maintenance is required for a scrubber. For example, the only regular maintenance required for a wet scrubber is to change the scrubber water regularly.
Can handle flammable and explosive dusts with minimal amount of risk.
Provide gas absorption and dust collection.
Scrubbers are compact so can often be retrofitted into existing systems.
Disadvantages
Expensive to install, (a costly investment than my other options)
Can take a long time to install it can take around six weeks in dry-dock for retrofitting a scrubber system.
Scrubbers do not remove NOx, CO2
Potential disposal issues
Dry scrubbers are known to be less efficient than wet scrubbers, so they may allow more contaminants to escape into the environment.
what’s the difference between wet and dry scrubbers?
Wet scrubber
A wet scrubber use sea water or fresh water with an added chemical. This added chemical can be caustic soda (NaOH) or limestone (CaCO3). The washing liquid with an added chemical will be distributed and be able to meet the exhaust gas by nozzles. Wet scrubbers can have 3 different systems that can be used. These being closed loop, open loop and hybrid.
Dry scrubber
For dry scrubbers’ water isn’t used as washing material instead, pellets of hydrated lime are used to remove sulphur. Dry scrubber systems use less power than wet systems because they do not require circulating pumps. Their overall weight is more than wet scrubber systems
what emergency equipment is provided on a ship?
Emergency equipment is arranged to operate independently of all main power sources. It includes such items as the emergency generator and the emergency fire pump. Both items of machinery are located remote from the engine room and usually above the bulkhead deck, that is at the weather deck level or above. The emergency generator is usually on one of the accommodation decks while the emergency fire pump is often inside the forecastle. The emergency generator is a diesel-driven generator of sufficient capacity to provide essential circuits such as steering, navigation lights and communications. The diesel engine has its own supply system, usually of light diesel oil for easy starting. Batteries, compressed air or an hydraulic accumulator may be used for starting the machine. Small machines may be air cooled but larger units are arranged usually for water cooling with an air cooled radiator as heat exchanger in the system. Modern systems are arranged to start up the emergency generator automatically when the main power supply fails. The system should be checked regularly and operated to ensure its availability if required. Fuel tanks should be kept full, ample cooling water should be in the radiator cooling system, and the starting equipment should be functional. Batteries of course, should be fully charged or air receivers full. The emergency fire pump is arranged to supply the ship’s fire main when the machinery space pump is not available. . A diesel engine with its own fuel supply system, starting arrangements, etc., drives at one end a main fire pump and at the other an hydraulic oil pump. The hydraulic oil pump supplies a hydraulic motor, located low down in the ship, which in turn operates a sea water booster pump. The booster pump has its own sea suction and discharges to the main pump suction. The main pump then supplies sea water to the fire main. The booster pump arrangement is necessary because of the considerable depth of many large modern ships.
what are the mechanics of a crankcase explosion?
Mechanics of a crankcase explosion
1.A hot spot is an essential source of such explosions in crankcases as it provides the necessary ignition temperature, heat for oil vaporisation and possibly ignition spark. Normal crankcase oil spray particles are in general too large to be easily explosive (average 200 μm). Vaporised lubricating oil from the hot source occurs at 400°C, in some cases lower, with a particle size explosive with the correct air ratio (average 6 μm). Vapour can condense on colder regions, a condensed mist with fine particle size readily causes explosion in the presence of an ignition source. A lower limit of flammability of about 50 mg/l is often found in practice. Experiment indicates two separate temperature regions in which ignition can take place, that is, 270–350°C and above 400°C.
2.Initial flame speed after mist ignition is about 0.3 m/s but unless the associated pressure is relieved this will increase to about 300 m/s with corresponding pressure rise. In a long crankcase, flame speeds of 3 km/s are possible giving detonation and maximum damage. The pressure rise varies with conditions but without detonation does not normally exceed 7 bar and may often be in the range of 1–3 bar.
3.A primary explosion occurs and the resulting damage may allow air into a partial vacuum. A secondary explosion can now take place, which is often more violent than the first followed by similar sequence until equilibrium.
4.The pressure generated, as considered over a short but finite time, is not too great but instantaneously is very high. The associated flame is also dangerous. The gas path cannot ordinarily be deflected quickly due to the high momentum and energy.
5.Devices of protection must allow gradual gas path deflection, give instant relief followed by non-return action to prevent air inflow and be arranged to contain flame and direct products away from personnel.
6.Delayed ignition is sometimes possible. An engine when running with a hot spot may heat up through the low-temperature ignition region without producing flame because of the length of ignition delay period at low temperatures. Vaporised mist can therefore be present at 350–400°C. If the engine is stopped the cooling may induce a dangerous state and explosion. Likewise air ingress may dilute a previously too rich mixture into one of dangerous potential.
7.Direct detection of overheating by thermometry offers the greatest protection but the difficulties of complete surveillance of all parts is prohibitive.
8.A properly designed crankcase inspection door preferably bolted in place, suitably dished and curved with say a 3-mm thickness of sheet steel construction should withstand static pressures up to 12 bar although distorted.
- There are many arguments for and against vapour extraction by exhauster fans. There is no access of free air to the crankcase and the fan tends to produce a slight vacuum in the crankcase. On balance most opinion is that the use of such fans can reduce risk of explosion. The danger of fresh air drawn into an existing over rich heated state is obvious. On the practical aspect leakage of oil is reduced.
what crankcase safety arrangements are provided?
Crankcase safety arrangements
1.Means should be adapted to prevent danger from the result of explosion in crankcases with forced lubrication systems.
2.Crankcases and inspection doors should be of robust construction. Attachment of the doors to the crankcase (or entablature) should be substantial.
3.One or more non-return pressure relief valves should be fitted to the crankcase of each cylinder and to any associated gear or chain casing.
4.Such valves should be arranged or their outlets so guarded that personnel are protected from flame discharge with the explosion.
5.The total clear area through the relief valves should not normally be less than 115 cm2/m3 of gross crankcase volume.
6.Engines not exceeding 250-mm cylinder bore but larger than 200-mm bore with strongly constructed crankcases and doors may have two valves usually fitted at the crankcase ends. Similarly constructed engines not exceeding 200-mm cylinder bore or having a crankcase volume of less than 0.6 m3 need not be fitted with relief valves.
7.Lubricating oil drain pipes from engine sump to drain tank should extend to well below the working oil level in the tank.
8.Drain or vent pipes in multiple engine installations are to be so arranged so that the flame of an explosion cannot pass from one engine to another.
9.In large engines having more than six cylinders it is recommended that a diaphragm should be fitted at near mid length to prevent the passage of flame.
10.Consideration should be given to means of detection of over-heating and injection of inert gas.
what the purpose of a flame trap?
Such devices are advisable to protect personnel. The vented gases can quickly be reduced in temperature by gauze flame traps from say 1500°C to 250°C in 0.5 m. Coating on the gauzes, greases or engine lubricating oil, greatly increases their effectiveness. The best location of the trap is inside the relief valve when it gives a more even distribution of gas flow across its area and liberal wetting with lubricating oil is easier to arrange. A separate oil supply for this action may be necessary. The explosion door in figure 11.1 has an internal mesh flame trap fitted. Flame traps effectively reduce the explosion pressure and prevent two-stage combustion. Gas-vapour release by the operation of an oil-wetted flame trap is not usually ignitable. Typical gauze mild steel wire size is 0.3 mm with 40% excess clear area over the valve area.
with the aid of a sketch explain the purpose and operation of a crankcase oil mist detector?
see motor sketch pack for drawing
Crankcase oil mist detector
If condensed oil mists are the sole explosive medium then photoelectric detection should give complete protection but if the crankcase spray is explosive the mist detection will only indicate a potential source of ignition. The working of one design of detector should be fairly clear from figure 11.2. The photo cells are normally in a state of electric balance, that is, measure and reference tube mist content in equilibrium. Out-of-balance current due to rise of crankcase mist density can be arranged to indicate on a galvanometer which can be connected to continuous chart recording and auto visual or audible alarms. The suction fan draws a large volume of slow moving oil–air vapour mixture in turn from various crankcase selection points. Oil mist near the lower critical density region has a very high optical density. Alarm is normally arranged to operate at 21.2% of the lower critical point, that is, assuming 50 mg/l as lower explosive limit then warning at 1.25 mg/l
Operation
The fan draws a sample of oil mist through the rotary valve from each crankcase sampling pipe in turn, then though the measuring tube and delivers it to atmosphere. An average sample is drawn from the rotary valve chamber through the reference tube and delivered to atmosphere at the same time. In the event of overheating in any part of the crankcase there will be a difference in optical density in the two tubes, hence less light will fall on the photo cell in the measuring tube. The photo cell outputs will be different and when the current difference reaches a predetermined value an alarm signal is operated and the slow turning rotary valve stops, indicating the location of the overheating. Normal oil particles as spray are precipitated in the sampling tubes and drain back into the crankcase.
explain the importance of bearing temperature detection and how it can be measured?
The principal bearings in an engine have the potential to become the cause of a crankcase explosion. If they are becoming overheated for some reason the localized ‘hot spot’ causes vaporisation of the oil to form the oil mist and thereby setting up the conditions listed in ‘The mechanics of a crankcase explosion’. The very same bearing can also act as the hot spot initiating the start of the explosion. One of the problems is that until recently it has been very difficult to measure the big end or crosshead bearing temperatures accurately. Systems in the past consisted of catching the oil that had sprayed from the big end bearing and measuring the temperature of the oil to give an indication of the temperature of the bearing. Compared to the indirect measurements of a conventional oil mist detector, direct continuous monitoring of the crankpin bearing temperature permits earlier detection of a bearing overheating. This prevents major failures of critical and highly costly engine components and protects against the direct consequences of the non-operational availability of the engine. It also avoids any extra costs related to unplanned expensive maintenance operations.
To be able to continuously detect and monitor the temperature of rotating bearings in an accurate and reliable manner, Wärtsilä has recently developed an innovative wireless temperature-sensing device
The operating principle is to directly measure the temperature of the connecting rod big end bearing using a temperature sensor fitted as close as possible (within a few millimetres) to the bearing surface. The sensor then keeps in touch with the outside world by using a patented, surface acoustic wave (SAW) radar technology, which has been proven to be the most reliable technology for real-time wireless temperature monitoring. The signal processing unit (SPU) generates a radio wave pulse, which is picked up by the stationary antenna and converted into an acoustic wave which is sent to the rotating sensor. This acoustic wave propagates along the surface of a SAW chip fitted with multiple reflectors, thus permitting the sensor to reflect back a pulse train to the stationary antenna; the time delay between echoes depends on the temperature of the SAW chip. The wireless temperature sensors are installed in the rotating connecting rod big end. The stationary antennas are screwed to a custom-designed bracket fixed inside the engine block in such a way, that the sensors and antennas pass within a fixed distance of each other at each rotation of the engine crankshaft. The resultant signal is then transmitted via a thin cable passing through the engine block, to the SPU fixed to the engine, and from there to the control room cabinet placed in the engine room.
why are marine fuel and exhaust emissions an environmental concern?
There are four main constituents of diesel engine exhaust which are of environmental concern NOx, SOx CO2 and particulates (soot). CO2 is a product of combustion and the amount will depend on the chemical composition of the fuel, natural gas having a lower value than typical liquid fuels. Poor combustion will produce soot and unburned hydrocarbons in the exhaust. NOx is a function of high-temperature combustion in the engine cylinders where the nitrogen in the air reacts with the oxygen.
Current and forthcoming legislation limits NOx emissions. Apart from controlling NOx production within the engine cylinder, the exhaust stream can be treated by selective catalytic reduction to reduce final NOx emissions to very low levels. SOx in the exhaust stream represent the sulphur that was present in the fuel. They can be removed from the exhaust by scrubbing, or by eliminating sulphur from the fuel in the refining process before it is supplied to the ship.
