Intelligent Cylinder Lubrication for Modern Marine Engines

The main reason for developing hi tech cylinder lubrication system is to reduce the operational costs of the engine. Moreover, the most expensive lubricating oil is generally used for the engine’s combustion chamber as cylinder lube oil. 
– MAN Diesel and Wartsila have introduced a remarkable technology for modern electronically controlled marine engines

In this article we will understand what does pulse lubrication means and how it helps to reduce the cylinder oil feed rate and eventually the operating costs of the ship.

Wartsila- A major player in the marine engine manufacturing industry has introduced an intelligent cylinder lubrication system in its electronically controlled engine

Construction and Working of Pulse Lubrication System

• There are normally eight quills attached to the cylinder liner in a single row, which gets the oil supply from the electronically controlled dosage pump

• The oil is supplied to the dosage pump from daily tank via fine filter of 40 microns

• The quills consist of a duct passage to store metered quantity of oil. The area of this duct passage and the quantity of oil can be altered by changing the position of the central piston

• There are crank angle sensors attached to the engine which give signals to the control unit in order to  inject oil at the correct position of piston movement

• 200 bar high pressure servo oil reduced to 50 bars are supplied to the lubricator unit, which pressurises the centre piston in the quills. This injects oil inside the liner at adequate pressure for even distribution

• WECS (Wartsila Engine Control System) which is the master controller of the Pulse lubrication system controls the solenoid valve opening and the oil injection

Each unit is provided with 8 lubricating quills, 2 piping systems of Cylinder oil and servo oil, and A 4/2 solenoid valve to servo oil flow.

After receiving signal from the crank angle sensor, at the correct position i.e. between the pack of piston rings, WECS allows the solenoid valve to open and pass the servo oil. This in turn presses the central piston and delivers the oil stored in the duct passage of the quills.

As soon as the injection is over, there is a small orifice which fills the duct passage again with the cylinder oil as the central piston moves backward. This ensures that the oil is always present in the chamber in metered quantity as decided by the WECS after calculating load and sulphur content of the fuel.

Benefits of Pulse Lubrication System:

1.Reduction in Cylinder oil Feed rate –up to 0.7 gm/kwh and thus reduction in operating cost

2.Well précised delivery of metered cylinder oil giving better lubrication to piston ring and liner

3.Better distribution of oil within the liner

4.Less fouling of combustion space

5.Less fouling of scavenge space

Fuel Polishing

Fuel Polishing:

Fuel polishing is the process of removing contamination such as water and particles from fuel to ensure that it remains in line with fuel specifications. Ideally, fuel should have an ISO particle code of 18/16/13 and a dissolved water content no greater than 200 parts per million. There should be no free or emulsified water present. 

Fuel polishing will ensure that the fuel is 'clean and dry' meaning free from water and dirt thereby reducing the possibility of engine or fuel system damage

Diesel fuel can become contaminated not only in your fuel tank but on its way from the refinery. Impurities, rust, and even tar build up can cause a wide range of issues with marine engine injection systems. Even "pure" diesel fuel in a clean tank can become contaminated as it oxidizes, resulting in paraffin and asphalt.

There are many companies who can pump your fuel out, polish and pump the diesel back into your tank. This can be time consuming and worst of all, expensive


On board fuel polishing systems are one of the easiest ways to save money.  Keeping fuel clean will result in better combustion, reduced maintenance costs, and less waste.  Together these help us to a greener earth.  There are several models of onboard fuel polishing/transfer systems to choose from.

Now we will see the line diagram of a typical fuel polishing system:

Day Tanks:

It is important to remember that the clean and dry fuel in the day tank will be exposed to the same conditions that cause the fuel in the main storage tank to become bad. Given enough time, the fuel in the day tank will get to the same condition as the fuel in the main tank. A filter and a water separator are still required on the outlet of the day tank.

To provide the desired results, this tank must, in fact, be a "Day Tank." That is, the fuel in this tank must remain there for only a short time. All the problems of long-time fuel storage in the main tank will be present in the day tank if fuel remains in it for long periods of time. Once it ceases to be a "Day Tank" it must be treated just like any other tank.

Fuel Filters:

It's important when considering fuel filters that you choose the correct micron rating. The smaller the micron rating, the more filtration you can expect. You will have to frequently check and or replace a low micron filter; however, you will also filter more of the impurities out of your diesel fuel. Or, for a more advanced system, use a two-stage filter system, with the first filter being a larger micron rating.

Fuel Pump Selection:

 Walbro pump is used,It's a Holley universal EFI in-line electric fuel pump.

http://www.youtube.com/watch?v=nzlb3Jp46NU

Utilizing the System:

How often should you use the fuel polishing system? During the warmer months it's advised to cycle your fuel through the filtration system at least twice a week

What is Power Balancing of Marine Engines?

The efficiency of the overall ship depends a lot on the efficiency of the engine running . One of the important factors to ensure efficiency of marine engines is to control the power produced from each of its cylinder. The process of making fine adjustments to achieve equal power from all engine cylinders is known as power balancing.

Power balancing of engines is carried out by making minor adjustment to fuel pumps of individual cylinders. The quantity of fuel injected in the cylinder plays the most important role in power balancing.

The small adjustments made to the fuel pumps should be such that the units are not overloaded and the exhaust temperature doesn’t go beyond the safe limits. It is therefore necessary to be extremely careful while carrying out adjustments for power balancing.

Important Points While Carrying out Power Balancing of marine engines:

1. Individual units are not overloaded
2. Exhaust temperature of the units do not rise above the acceptable levels

Things to check while making Adjustments for Power Balancing:

1. Fuel pump rack position
2. Exhaust and cooling water return temperatures for each cylinder of marine engine
3. Measurements from indicator diagram
4. VIT adjustment

It is to note that not all cylinder units show equal exhaust temperatures. However, for each engine the figures follow a certain path which can help in accessing a situation. Peak or maximum pressure of the cylinders should also be checked along with cylinder temperatures.

If proper care is not taken during power balancing, the marine engine can become unbalanced, leading to other serious problems.

 Unbalanced situation of the engine might lead to:

1. Overloading of bearings and running gears
2. Piston blow past
3. Overheated or piston seizure
4. Vibration followed by fatigue
5. Fatigue cracking in bearings, studs, or bolts
6. Cracking in crankshaft
7. Failure of holding down bolts

If you are the watching keeping officer, you must check the following things to ensure smooth power balancing of marine engine:

1. Check relevant temperature and pressures (exhaust and cooling return temperatures)
2. Check lubricating oil and turbo charger pressures
3. Check for any unusual noise or vibration
4. Keep an eye on the exhaust for any kind of smoke
5. Check if the turbocharger is running smoothly without surging or panting
6. Check fuel pump settings
7. Measure clearances and timings of fuel pumps when engine is not working
8. Ensure that fuel injectors are changed at regular intervals of time after cleaning and testing. A faulty injector would not only cause loss in power but would also lead to overloading of other cylinders as the governor would try to maintain the normal total power output
9. Carry out maintenance of the marine engine at regular interval of time and note down any deviation from the normal running speed
10. Any error found should be rectified at the earliest.

Do you have any more important information on power balancing of marine engines? Kindly share it with others in comments below.

What are Breaking-In and Running-In?

A two stroke or a four stroke marine engines require time-to-time maintenance for efficient and break free operation. When ever there is a change or renewal in the major combustion parts of the engine i.e. piston or liner and if the engine has gone under complete life time, then it is put back in operation under step running programmes known as “Breaking in” and “Running in”.

                                                                                 

Why Breaking in and Running in?

The newly fitted liner, piston, or piston rings are machined prepared in the workshop ashore. They have surface asperities and there is no bedding between the moving surface i.e. liner and rings.

Under such situations, if proper step running is not followed then it may lead to heavy blow past of combustion gases. The blow past can be dangerous as it can lead to scavenge fire. Hence initially a step running program is required for newly fitted piston, piston rings and line'

Breaking in:

It is a short period of running of the marine engines under no load so that the piston rings are allowed to seat and lubricated properly.Breaking in is carried out to achieve maximum wear rate. If low sulphur fuel or marine diesel oil is used, the breaking in period will increase. A low jacket water temperature is maintained to increase the rate of wear.

An average breaking-in time for a four stroke engine is 48 hours.

Running in:

Just like breaking in, the running in schedules are also provided in the engine manuals and differ for parts to parts.In two stroke engine, the cylinder lubrication is kept in higher side in terms of oil quantity for proper lubrication of piston rings and liner.For four stroke engines with common sump lubrication, low TBN lube oil is used initially and after 30 % of load, the new recommended oil is used.

If the proper Breaking In and Running In period is not followed after the maintenance, it may lead to blow past of the combustion gases, leading to scavenge fire. It can lead to heavy scuffing resulting in increase in liner wear.

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Sulzer RT Flex Marine Diesel Engine

The common rail system :

Although common-rail fuel injection is certainly not a new idea, it has only become truly practical in recent years through the use of fully-integrated electronic control based on high-performance computers which allow the best use to be made of the flexibility possible with common-rail injection. 

Sulzer low-speed engines have long had the benefits of double valve-controlled fuel injection pumps with variable injection timing (VIT), and a degree of variable exhaust valve timing being achieved hydraulically in the VEC system, the variation in timing so obtained has been very limited. 

The common-rail concept was adopted also because it has the advantage that the functions of pumping and injection control are separated.

The common-rail concept thus provides an ideal basis for the application of a fully-integrated electronic control. The combined flexibilities of common rail and electronic control provide improved low-speed operation, engine acceleration, balance between cylinders, load control, and longer times between overhauls. They also ensure better combustion at all operating speeds and loads, giving benefits in lower fuel consumption, lower exhaust emissions in terms of both smokeless operation at all operating speeds and less NOx, emissions, and also a cleaner engine internally with less deposits of combustion residues. Engine diagnostics are built into the system, improving engine monitoring, reliability and availability.

Supply unit:

               

The supply unit is naturally at the location of the gear drive: at the driving end for five- to seven-cylinder engines, and at the mid gear drive for greater cylinder numbers. The supply unit has a rigid housing of GGG-grade nodular cast iron. The fuel supply pumps are arranged on one side of the drive gear and the hydraulic servo-oil pumps are on the other side. This pump arrangement allows a very short, compact supply unit with reasonable service access. The numbers, size and arrangement of pumps are adapted to the engine type and the number of engine cylinders. For RT Flex Sizes I and IV, the supply unit is equipped with between four and eight fuel supply pumps arranged in Vee from. The size O supply unit, however, has just two or three supply pumps in-line.The fuel supply pumps are driven through a camshaft with three-lobe cams. This camshaft cannot be compared with the traditional engine camshaft. It is very short and much smaller diameter, and is quite differently loaded. There is no sudden, jerk action as in fuel injection pumps but rather the pump plungers have a steady reciprocating motion. With tri-lobe cams and the speed-increasing gear drive, each fuel supply pump makes several strokes during each crankshaft revolution.  engines with up to eight cylinders, the rail unit is assembled as a single unit. With greater numbers of cylinders, the engines have a mid gear drive and the rail unit is in two sections according to the position of the mid gear drive in the engine he fuel common rail provides storage volume for the fuel oil, and has provision for damping pressure waves. The common rail system is designed with very high safety margins against material fatigue. The high-pressure rail is trace heated from the ship's heating system, using either steam or thermal oil. The simplification of the fuel rail for Size IV, without intermediate flanges, compared with that for Size I allowed the trace heating piping also to be simplified. The trace heating piping and the insulation are both slimmer, allowing easier service access inside the rail unit.

Marine Diesel Engine Cooling Systems

Raw Water Cooling:

A flexible impeller pump provides an efficient solution to most raw water pumping needs. The primary advantage of flexible impeller pumps is that they are self-priming, which means that when the vanes of the impeller are depressed and rebound, they create their own vacuum, drawing fluid into the pump. A dry pump can lift water up to as much as three meters. Thus a flexible impeller pump being used for engine cooling does not need to be manually primed or located below the water line. An added feature of a flexible impeller pump is that it can pass fairly large solids without clogging or damaging the pump. This reduces the need for filtration of incoming fluids.

For general or fresh water applications, a standard long lasting neoprene rubber impeller is used.

A general feature of all flexible impeller pumps is that they cannot be permitted to run dry for more than 30 seconds. Both the impeller and the seals require water for lubrication and will soon burn out if run dry. 

Fresh Water Cooling:

For circulation of the internal, closed, fresh water circuit of the cooling system it is common to use a flexible rubber pump if it is located on the cold side of the system (max. 55°C). Other types of belt-driven centrifugal pumps are also used. The closed circuit normally transfers heat from the engine to the heat exchanger. The liquid used is water and anti-freeze.

Cooling Capacity:

The required output of the cooling pump is related to engine type and size, not to the size of the heat exchanger and exhaust system. This is true for both raw water as well as fresh water handling systems


Temperature Regulators (Thermostats)

Thermostats are usually placed in the outlet at the top of the cylinder head to prevent the coolant from moving to the header tank until the marine engine has nearly reached operating temperature.

There are different types of thermostats, the most common being the wax pellet type. The capsule on the lower part of the thermostat has a mixture of wax and copper (to increase the thermal conductivity) sealed in it. As the coolant temperature increases, the wax expands and forces a rod to open the poppet valve at the top of the thermostat, which allows the coolant to circulate.

Cooling System Checks

• To test your thermostat, boil a pot of water and drop in the thermostat. (The water must be 100 degrees celcius--the thermostat usually opens at 85 degrees celcius.) If the thermostat opens it is okay. If it doesn't open, replace or clean carefully as they can become sticky with deposits. Yanmar thermostats can and should be regularly serviced. Some thermostats cannot be serviced.
• If the thermostat doesn't work, do not remove it and run the engine without it, as the engine will run cold and tight. You can drill a series of 1/4 inch? holes to give equivalent flow to an open thermostat. This will get you home, but you must then replace it. Be careful not to fit thermostat upside down.
• Thermostat housings often corrode and need to be replaced. Some can be fabricated.
• The cooling system should be checked after 100 hours running, or at least once each season, for leakage, deposits, etc.
• The thermostat can be taken out of the housing on the front of the engine.
• The heat exchanger core should be removed bi-annually for cleaning and inspection.
• Many heat exchangers are fitted with anodes to protect the expensive core. Check regularly.
• Check all hoses and clamps regularly.

Replacing the sea-water pump impeller

The pump impeller is made of neoprene rubber and this can be damaged in the case of water deficiency if, for example, the sea-water intake should be blocked. The  pump impeller trouble shooting guide will be helpful in identifying impeller problems. The sea water pump impeller is changed as follows:

1. Remove the cover from the sea-water pump. Note that there is the risk of water getting into the boat. With the help of two screwdrivers pull the shaft with the pump impeller out of the housing as far as necessary to reach the bolt retaining the impeller. Place some kind of protection under thescrewdrivers in order not to damage the impeller housing. Alternatively, using channel-lock pliers, slide jaws between blades of impeller, rotate and withdraw.
2. Pull the impeller off the shaft. Clean the inside of the pump housing and fit the new impeller. Always have a spare impeller on board.
3. Check that the pump coupling is not damaged, by trying to turn the pump impeller. Fit the cover with the original gasket, which has the right thickness.

Twin Spark Theory

Twin S

park Theory

Twin Spark Theory

Twin Spark :

Normal engines have one spark plug per cylinder. However, since decades ago, Alfa Romeo insisted on putting 2 spark plugs in each cylinder, firstly in its racers and now in its cars. As ignition takes place in two locations rather than one, this enable more efficient combustion and cleaner emission. However, besides Alfa, in the past 15 years only Mercedes and Porsche have ever applied Twin Spark design to their engines. This is mainly because of the complexity of cylinder head - it would be too difficult to put 4 valves and 2 plugs into the small cylinder head area. ( Mercedes' and Porsche's engines are 3 valves and 2 valves per cylinder respectively, so they have no such problem.) Only Alfa Romeo have applied it to 4-valve engines.

In its Original 2 valve twin spark engines, Alfa actually used the twin spark plugs not to create extra power but to cure rough running at low rpm and to improve fuel economy.

In its original guise when being develop Alfa could extract a creditable 148bhp from its two litre two valve engine. The problem was that it had rough low speed running and poor low speed economy and emissions. The main cause being the high degree of overlap being used in the cams to get the high power.

What Alfa found though was that whereas in a normal high overlap engine running at low speed unburnt fuel was tumbling out of the exhaust port, and the inherently diluted mixture of the EGR system which was being used to clean up the emissions, was difficult for a single plug to fire. Under normal conditions, a single plug could ignite an air/fuel ratio of 17:1, whereas twin plugs could ignite a mixture as lean as 20.8:1.

Not only could they allow lean mixtures via EGR giving good economy, but they could ignite it reliably, giving better, smoother low speed running and cleaner emissions.

As the modern engine continues to develop though we may see more of the twin spark plug the reasons for this and its lack of previous use are many.

Older engines tended to have long stroke/ small bore combinations

Modern engines have ever-increasing bore dimensions

Modern fuesl are becoming slower burning.

Engines are getting ever higher revving

The result is that the flame at the point of ignition needs to travel ever further is shorter and shorter durations. Bigger bores means more area for plugs and valves, multiple spark plugs seems an obvious and cheap solution to getting a fast burning charge.

New Engines For 2013

New Engines For 2013

• Cat C-7 - 550HP
• Cat 12.9 - 1000HP
• New Cat 3126's
• New Cummins 6.7 to 600HP
• New Duramax's to 600HP

 New Caterpillar and Cummins Engines for Marine use, Industrial use, Power Generation and Marine Propulsion. We also offer Remanufactured, Rebuilt & High Performance Diesels. We are a  Marine Diesel Specialist, providing up To 50 Knot Conversion Packages. Our custom machine work and fabrication services have been in operation since 1969.

Piston Ring Failure Analysis

A piston ring is a ring used in conjunction with a piston to seal an engine's combustion chamber and regulate oil use. Piston rings often experience wear due to a number of different factors. As such, it is important to know how to analyze piston ring failures.

Scuffing

• Scuffing of the piston ring leads to wear on the ring face. Damage to the ring face can lead to a loss of ring control. When this occurs, it usually results in high base pressure, oil over-consumption and piston scoring. This can cause the piston to seize altogether.

Causes

• Three things are the primary cause of a piston ring becoming scuffed; they result from normal engine operation. These are fuel wash-down (which occurs when abrasive fuel comes into contact with the piston ring), debris ingestion (which occurs when materials from outside get stuck in the engine) and severe overloading (which occurs when the engine is overworked).

Improper Assembly

• Piston rings are sometime assembled improperly. If the piston ring is misaligned due to improper assembly, oil may bypass the rings. This can cause carbon buildup, which can lead to a piston ring becoming scuffed.