ChiefEngineer’sLog

Fuel oil properties and effects explained - Part III https://chief engineer log.com/2022/02/05/fuel-oil-properties-and-effects-part-iii/

Fuel oil properties and effects explained - Part II https://chief engineer log.com/2022/02/03/fuel-oil-properties-and-effects-part-ii/

Fuel oil properties and effects explained - Part I https://chief engineer log.com/2022/02/03/fuel-oil-properties-and-effects

This piece of metal was found inside scavenging space, under one of the units, at the last scavenge space inspection. This piece is from one of the auxiliary blower’s impeller. The reason behind it is material fatigue due mechanical stress as a result of continuous start and stop of auxiliary blowers during maneuvering and vessel slow steaming. Needless to say that this must be avoided as much as possible and engine should run either with auxiliary blowers off or on lower rpm with auxiliary blowers on Manual mode. During Manual mode constant care must be kept with respect to blower’s electrical motors load in order to prevent overloading and damage the motors. However, in this case the impeller has been replaced, as because of this damage it will be dynamically unbalanced and will lead to bearings failure and implicitly to electrical motor failure. #chief_engineer_log #chiefengineer #lifeofmarineengineer #marineengineering #mechanicalengineer #mechanicalengineering #seafarerslife💯⚓️🚢 #seafarer #seamanlife

Checking fuel oil pump suction, delivery and spill valves on RTA 96. The reason behind this is that we noticed a low Pmax on this unit, especially when engine is running on low rpm (it looks like there is no firing at all). All fuel injector valves have been changed, fuel pump relief valve replaced but still no positive outcome. Troubleshooting still in progress. Any ideas…? #chief_engineer_log #chiefengineer #lifeofmarineengineer #marineengineering #mechanicalengineer #mechanicalengineering #seafarerslife💯⚓️🚢 #seafarer #seamanlife #seamen #engineersatsea #electricalengineer #solas #ladyengineer #ship #ocean #sea #seamen_life #seamans #womanatsea #humansatsea #mechanicaleducation #navalarchitectureandmarineengineering #mechanicalengineeringstudent

One of those days when you get a call from your team to let you know that something bad just happened. This is an air cooled type starting air compressor who collapsed due piston seizure inside cylinder. The connecting rod broke and damaged the compressor block and crankcase. Fortunately no one was around at that time and nobody was injured. #chief_engineer_log #chiefengineer #lifeofmarineengineer #marineengineering #mechanicalengineer #mechanicalengineering #seafarerslife💯⚓️🚢 #seafarer #seamanlife #seamen #engineersatsea #electricalenginee

During pressure test of cargo hold bilge system found a leaking non-return flap. The flap loses its seal due hard deposit accumulated on its seat surrounding. This is a good sign that the system has never been properly tested. I have discovered that the crew was not even aware on how to perform the test, but the job has been cleared up into PMS system and checklist completed. This shows poor seamanship, lack of knowledge and responsibility. 🤦‍♂️🤦‍♂️🤦‍♂️

We have just replaced the governor on one of our generators due several black out. It seems that the due of a fault into the governor the quality of control deteriorates and become unstable. The speed governor comprises the following components: speed governor, actuator, governor linkage with transmission levers and teletransmitter. Most of the operating faults result from: dirty injection pump fuel linkage, excessive play in the bearings of the fuel control shaft, sluggish fuel control shaft, worn ball joint heads, excessive play between governor output shaft and the fuel control shaft, failure to comply with the intervals for changing the governor oil, failure to comply with the required intervals for maintaining the governor, faulty connectors and cables.

What do you think about this? 🤔 How would you react if you would see something like this? Honestly…what kind of engineers are these type of persons? What kind of personal standards these guys have? I mean…for real?

During annual bunker line pressure test we found one of the deck bunker line section leaking. This emphasizes the importance of bunker line pressure testing, a process that is ignored and avoided by many. On the annual bunker line pressure test each transfer pipe onboard a vessel must be tested under static liquid pressure, at least 1.5 times the maximum allowable working pressure (MAWP). Special attention should be paid to flange joints, valve gland packing, pump seals etc. MAWP is considered to be the design relief valve pressure setting of the relief valve on the bunker transfer pump. In the absence of the relief valve the MAWP should be taken to be 5.0 kg/cm2. The test should be conducted while underway at sea at least 200nm from shore during day light. Bunker transfer pump may be employed for this test. After the test, the date and test pressure should be stenciled on the pipe lines and deck at prominent locations. The stencil should be:”Hydro Test Date: xx/xx/xxxx Pressure: xx kg/cm2.

The self cleaning process takes place with either partial or total discharge of the bowl. For this purpose, the bowl must be first filled with displacement water following closure of the dirty oil inlet. Depending on the discharging process the bowl will be partially or completely filled with displacement water. Control water is introduced into the opening chamber of the bowl to open it, thus the pressure exerted by the control water moves the piston valve which opens the sludge discharging ports. The content of the bowl will be discharged totally or partially depending on the process. Due high centrifugal forces and liquid velocity generated within the bowl expels almost all the sludge. Damaged seal o-rings or scratched/damaged surfaces of the sludge chamber and disks make the self-cleaning process more difficult and sometimes impossible this being signaled through a machine malfunction alarm. Control water flows out of the bowl during sludge discharge and the bowl is closed again.

Another way of checking which unit is leaking is to run the engine on idle and dismantle the cooling line on each one of the injectors and see if any fuel comes out through the cooling ports

We have experienced a power loss due Oil mist detector high level alarm on one of our diesel generators. After machine stops, we have waited for 30 minutes and after we have checked the crankcase doors temperature just to make sure that is safe to open the crankcase. At the first check everything seems to be in order with no abnormalities noted inside crankcase. We have opened the rocker arm covers and noted some traces of water so we have decided to test the oil and found a water content of 0.6 % which is very high for these generators, as everything above 0.2 % poses a high risk of damaging the bearings. So, we have started checking from where the water ingress and found that the nozzle cooling water system for this generator is empty. In order to check from which unit the leak occurred, we have dismantled every single injector valves and pressure test them and found that on one of them the fuel comes out from cooling ports and another injection found with a crack on its body.

Through rapid rotation of separator bowl G-force is used to separate liquids from other liquids and solids efficiently with great accuracy and speed in a manner that we can easily control it. A disk stack within the bowl contributes to higher separation efficiency by substantially increasing the separation area in the separator bowl. This means that the separation task using a centrifugal separator not only takes place significantly faster, but results in higher quality and higher yield. The solids that concentrate at the outer edge of the bowl are removed either continuously, automatically or manually depending on the amount of solids involved. Source and credit: Alfa Laval

Marine purifiers use separation technology involving a disk stack separator, known as a centrifuge. This is used for centrifugation in which various phases of solids and liquids are isolated from one another based on difference of densities. Similar to a settling tank, disk stack separators use the force of gravity to separate liquid with a specific density from other liquids and solids. Unlike a settling tank which uses retention time as the main parameter for liquids of different densities to divide into layers of and solids to precipitate to the tank, centrifugal separators use mechanical force to separate liquids and solids with different densities from each other. In an essence a disk stack separator is a settling tank who’s base is wrapped around the center line of the bowl. Conical plates are stacked, one on top of the other, inside the bowl, to provide more separation area and to increase separation efficiency. These stacks dramatically speed up the precipitation of the solids from the liquids.

When air coolers become fouled, less heat will be transferred from the air to the cooling water. This is shown by changes in the air and cooling water temperatures. In the pressure drop of the air passing through the air cooler changes will also occur. The amount of change will depend on the degree and Natura of the fouling. The symptoms of air side fouling are, for examples: decrease of air temperature difference across cooler, increase of air pressure drop across cooler, rising scavenge temperature, rising exhaust temperature on all cylinders, a smaller increase in cooling water temperature across the cooler. The symptoms of water side are, for example: rising scavenge temperature, reduction in the difference of the air temperature across the cooler, rising exhaust gas temperature from all cylinders, increase in the temperature rise of the cooling water if fouling or chocking materially reduces the amount of water flow.

What causes fouling of the air side of air coolers? Fouling of the air passages in an air cooler, which is part of the engine turbocharging system is usually due to oil and oily-water films collecting on the sides of the tubes and tube fins. Lint and similar material adheres to these films of oil or emulsion. The presence of oil may be caused by faulty air filters, or by improperly placed filters which allow the air to pass by the side of the filter element. Sometimes the oil is drawn from the bearing at the blower end. The presence of moisture is usually the result of high humidity, when the engine is operating in warm air temperatures in conjunction with low sea water temperature.

One of the questions that I got it from you was about “ what do you understand by the term ‘variable injection timing’(VIT)?” Variable injection timing is a form of fuel pump control, enabling an engine to operate with the designated maximum cylinder firing or combustion pressure from approximately 75% power output to maximum power. This improves thermal efficiency and lowers fuel consumption. The fuel consumption for an engine at any load will be related to the expansion ratio of the combustion gases from their maximum pressure to the pressure at the commencement of exhaust blowdown. The maximum cylinder pressure is a factor used in the design of the crankshaft and other important engine parts. In a normal engine the maximum cylinder pressure is reached only at full power operation, whereas with VIT the maximum cylinder pressure is reached at about 75% of the full load. The expansion ratio is therefore increased when the engine is operating under light loads right up to full load.

There was a someone question about the purpose of fuel pressure regulating valve in diesel generators fuel line. Well, the main purpose of that valve is to ensure that there is always an adequately large amount of pressurized fuel available to each engine. If, for examples there is no sufficient fuel and there is an increase on engines load, then they will starve fuel and there is a high chance of tripping and subsequently loss of power. The pressure regulating valve is normally located in the supply line to the engines and it should be set to a certain pressure (6-8 bar) . In the event of low fuel oil pressure an alarm will be initiated. In the event of a malfunction of this valve, it can be by-passed, but by doing so the system pressure must be carefully monitored by the duty engineer to ensure correct operation.