Hansen cylinder oil injector has the advantages of fuel saving and good lubrication effect, but the frequency of oil gun and safety valve sensor failures is high. If not detected and dealt with in a timely manner, it will bring serious consequences.
This article starts with two accident cases and explores corresponding response measures by combining the structure and working principle of the oil gun and safety valve.
NSRY engine Hansen Swirl Injection Principle model: MKV I-T155-SIP III;
Manufacturer: HANS JENSEN LUBRICTORS,
Its working principle is that before the piston moves upward through the cylinder oil injection hole, almost at the same time as the exhaust valve is closed, cylinder oil begins to be injected into the cylinder, and the sweeping vortex is used to distribute oil to the inner wall of the cylinder liner until it reaches the top of the cylinder liner, where the working conditions are the most severe and where additives and lubricating oil films are most needed;
The traditional cylinder oil injector injects cylinder oil into the piston ring when the piston moves upward, relying on the piston ring for distribution, which can easily cause poor distribution of cylinder oil on the surface of the cylinder liner, and even almost no cylinder oil distribution on the upper part of the cylinder liner.
Hansen cylinder oil injector has significant characteristics in saving cylinder oil consumption and lubrication effect, but its structure is complex and the probability of failure is high, especially for the oil gun and injector safety valve sensor "relief sensor".
In February 2021, during the maiden voyage of the "NSRY" ship from China to Brazil, seven fuel injection guns in the main engine's NO.3, NO.5, and NO.7 cylinders were blocked, and a "SAFETY VALVE OPEN" was issued
Constant "fault alarm, stopped 4 times on the way for inspection and replacement of the oil gun.
After arriving in Brazil and breaking down, the large wheelset inspected a total of 56 oil injection guns in 7 cylinders of the main engine, and found that 2 oil injection guns in cylinders NO.5, 6, and 7 did not spray oil.
Further inspection revealed that the needle valve of the SIP III valve was worn and stuck. Strangely, during the operation of the main engine, the cylinder oil injector system did not issue a corresponding alarm.
Coincidentally, on March 24, 2020, during the return journey of the company's "YHH" ship from Brazil, the compression pressure, burst pressure, and indicated power of the NO.2 cylinder of the main engine were significantly low. The exhaust temperature was nearly 30 ℃ higher than the average value, and the scavenging temperature reached 58 ℃ (about 10 ℃ higher than usual).
During the parking inspection, it was found that the interface of the first piston ring was broken, the elasticity of the second piston ring was very small, the third piston ring was stuck, and there were obvious wear marks on the three piston rings. There were irregular vertical scraping marks on the inner wall of the cylinder liner.
There are 3 cylinder oil injectors (8 per cylinder in total), and the oil gun does not spray horizontally or atomize, only drops a small amount of oil downwards.
After comprehensive analysis, it is determined that the prolonged operation of the main engine without oil injection or poor working conditions is the direct cause of abnormal wear of the cylinder liner and piston.
From the above case, it can be seen that the working conditions of the oil gun and oil injector safety valve alarm device have a significant impact on the lubrication of the cylinder liner and piston. The author attempts to analyze the causes of the malfunction from three aspects: the oil gun, safety valve, and safety valve sensor, and propose management suggestions.
2, Cylinder oil injection gun
1. Poor quality of oil injection gun products
As the first ship to set sail, when the needle valve of the oil injection gun on the cylinder of the "NSRY" vessel experienced eccentric wear and jamming, and the operating time was less than 800 hours, it indicates that there are defects in the material, design, or manufacturing process of the equipment, and corresponding improvement measures need to be taken.
2. Disassembly, inspection, and assembly of the oil gun
When disassembling and inspecting the oil gun, pay attention to keeping it clean. You can use kerosene to clean each component, and use a special drill bit with a diameter of 0.3mm to clear the spray hole on the oil nozzle.
When disassembling the hexagonal positioning screw of the oil gun needle valve assembly, a hair dryer can be used to heat it up to prevent damage to the hexagonal position due to excessive resistance;
Before assembly, tighten the hexagon socket screw to the bottom and then retract it by about one thread to facilitate the next disassembly.
After blowing off residual oil or impurities with compressed air, lubricate each component with acid free lubricating oil, such as SAE15-20 hydraulic oil.
3. Oil gun function test
The function test of the oil injection gun includes valve opening pressure, valve closing pressure, and atomization test, among which the valve opening pressure is 75-80 bar and the valve closing pressure is 35-40 bar. The medium used in the test is SAE15-20 hydraulic oil, and diesel oil cannot be used, otherwise it will cause the needle valve to get stuck due to its poor lubrication performance.
4. Standardize the installation of oil injection guns
When installing the oil gun, thoroughly clean the oil gun seat hole on the cylinder liner, while paying attention to the distance between the nozzle top and the running surface of the cylinder liner.
As the cylinder liner wears out, this distance will change. Therefore, the depth of the oil gun inside the cylinder liner needs to be adjusted to ensure that the top of the nozzle is at a certain depth from the running surface of the cylinder liner. This not only ensures the lubrication effect, but also avoids being scratched by the moving piston ring, causing damage to the oil nozzle, piston ring, and cylinder liner.
5. Search for malfunctioning oil injection gun
When the spray hole of the oil gun is blocked or the needle valve is stuck, the "relief sensor" indicator light on the upper part of the cylinder oil injector will turn off, and the system will issue a safety valve opening alarm.
If the ship is equipped with specialized pressure testing tools, each oil gun can be inspected and tested on site without disassembling it.
If the ship is not equipped with specialized pressure tools, the oil supply pipe joint of a certain oil gun can be loosened while the oil injector is running. If the "relief sensor" indicator light of the safety valve sensor lights up, it can be judged that the oil gun is blocked. This method is suitable for quick troubleshooting of only one oil gun blocked out of eight oil guns per cylinder.
If there are 2 or more oil injection guns blocked in a certain cylinder, it is necessary to loosen all 8 oil injection gun oil supply pipe joints of the cylinder. At this time, the "relief sensor" indicator light of the safety valve sensor on the upper part of the oil injector should light up.
Then tighten each joint in turn, while paying attention to the "relief sensor" indicator light. If it goes off, it indicates that the oil gun is blocked and needs to be disassembled or replaced, and so on until all 8 oil guns of the cylinder have been tested.
If the inspection finds that all 8 oil injection guns of the cylinder are working normally, it indicates that a false alarm has occurred, and the safety valve or safety valve sensor "relief sensor" needs to be disassembled, inspected, and debugged.
6. Management of filters during the break in period
A diesel engine in the running in period is equipped with a 40 μ m filter on each injection gun to prevent impurities in the cylinder oil from entering the injection gun and reduce the risk of needle valve components getting stuck.
The instruction manual requires that the filter, along with the sealing ring and gasket, must be removed within 500 hours of operation. Otherwise, wax or additives in the cylinder oil may clog the filter screen, causing oil supply interruption.
In practical work, if impurities are found during the disassembly and inspection of the filter, it is recommended to clean or replace the filter before continuing to use it. After confirming that there are no impurities in the cylinder oil system, the filter can be removed because compared to the risks caused by wax or additives in the cylinder oil, impurities in the cylinder oil system have a more direct and obvious impact on the oil gun.
At present, in the design of new engines, the piston stroke is longer, the combustion pressure is higher, and at the same time, the use of inferior fuel and other adverse factors significantly increase the risks of acidic corrosion, cylinder oil degradation, abrasive wear, etc. Strengthening the maintenance of cylinder oil injectors to ensure lubrication effect is undoubtedly an important means to resolve these risks.
