I had a new 75,000 dwt Panamax bulk carrier at a shipyard that is a national production patent machine MAN B & W 6S60MC. After embarking on the boat, he started a one-year round robin of global routes. In the first few months, the host operation of the round was relatively smooth. However, about three thousand hours after the operation, a mechanical accident took place. At that time, the ship was loaded with nearly 70,000 tons of iron ore on its way to Peru from Peru. Suddenly, the host in operation suddenly and repeatedly gave a heavy and sonorous percussion. Engineers on duty immediately notify the bridge deceleration, listening and found the percussion sound from the host of the fourth cylinder, but to view the thermal parameters of the cylinder did not change significantly. Afterwards, stop for further double-check. When we open the host cylinder 4 camshaft box car inspection found: the cylinder head high pressure pump head uneven distribution of about 1.5 square centimeter pit 5, the fuel cam surface near the left part of about 2 square centimeters A pit. Due to the tight schedule, we had to take temporary measures to seal the cylinder to maintain half-speed battery life. During the voyage, the structure is as shown in the following figure by referring to the related drawings and materials: This type of main high-pressure pump heart-to-heart single cam commutation is through the fuel roller guide cavity indoor thrust block left and right swing to be achieved, the wheel is equipped with a roller pin D4, the free end of the pin is fixed with a set screw D12 It prevents axial movement of the pin shaft during operation. As the roller device in the host operation by the frequent impact and vibration and is not easy to check the particularity of the installation of the installation of the screws in the device to be given special attention, not only to tighten but also to do some insurance measures , Such as locking fuse, fastening agent, screw riveting Department through the above means to prevent the fastening screw due to the possibility of loosening to ensure long-term safe and effective operation of the device, careful analysis of the failure is not difficult It is found that the root cause of knocking of the periphery of the roller and the fuel cam is that the pin of the roller device pin is loosened under impact and vibration load by itself and withdraws from the pin hole of the pin so that the pin axis is free So as to tilt the roller guide device in the direction of è‰ è‰‰ so that the original surface contact between the roller and the cam becomes a line contact and the area of ​​its force is significantly reduced and the material reaches fatigue under a strong impact load Limits and fragmentation. Arrived in the host after the fourth cylinder high-pressure pump roller gear unit inspection, the results confirmed our analysis is correct. The pin of the roller pin has been loosened by about 1/3 of the screw thread. When the roller device is lifted out of the lead, the pin shaft slides out of the free end of the pin hole. Thus, the other of the host cylinder may also be late or sooner or later a similar failure, so we will be the remaining five high-pressure pump cylinder wheel guide unit removed to check and found that the pin wheel pinch screw tight After the corresponding anti-loose insurance are not done, using a hexagonal wrench a little effort can be released. In the absence of screw fastening agent on board, we take the method of tightening the stop screw and riveting the bolt with 2 to 3 points around the screw as a safety measure to ensure that the stop screw is easily released to prevent Similar incidents happen again. Later, MAN-B & W company maintenance engineer in Brazil came to help crew change the host cylinder 4 fuel cam. In the meantime, the engineer verified our inspection of the roller guide device of the high-pressure oil pump of the remaining cylinders of the main engine and the measures taken and confirmed that the measures we adopted were completely correct. This is a mechanical accident that I experienced in my work practice. On the one hand, the device is not a wearing part of regular maintenance and repair, and is seldom disassembled under normal circumstances. On the other hand, because of its strong concealment, The screw has been loose and out of the pin stop hole, once the device is disassembled pin axis automatically fall, otherwise it is difficult to consider to check this only deep within the hole within the hexagonal screw. More importantly, according to the norms of safe navigation of ships, there is no mandatory requirement that spare parts such as roller guides or cams must be provided. In the event of such an accident, the vessel in navigation is extremely difficult to handle and poses a serious threat to the safety of the ship. Therefore, to remind colleagues here, I hope to give everyone help and reference. | |
I had a new 75,000 dwt Panamax bulk carrier at a shipyard that is a national production patent machine MAN B & W 6S60MC. After embarking on the boat, he started a one-year round robin of global routes. In the first few months, the host operation of the round was relatively smooth. However, about three thousand hours after the operation, a mechanical accident took place.
At that time, the ship was loaded with nearly 70,000 tons of iron ore on its way to Peru from Peru. Suddenly, the host in operation suddenly and repeatedly gave a heavy and sonorous percussion. Engineers on duty immediately notify the bridge deceleration, listening and found the percussion sound from the host of the fourth cylinder, but to view the thermal parameters of the cylinder did not change significantly. Afterwards, stop for further double-check. When we open the host cylinder 4 camshaft box car inspection found: the cylinder head high pressure pump head uneven distribution of about 1.5 square centimeter pit 5, the fuel cam surface near the left part of about 2 square centimeters A pit. Due to the tight schedule, we had to take temporary measures to seal the cylinder to maintain half-speed battery life.
During the voyage, the structure is as shown in the following figure by referring to the related drawings and materials:
This type of main high-pressure pump heart-to-heart single cam commutation is through the fuel roller guide cavity indoor thrust block left and right swing to be achieved, the wheel is equipped with a roller pin D4, the free end of the pin is fixed with a set screw D12 It prevents axial movement of the pin shaft during operation. As the roller device in the host operation by the frequent impact and vibration and is not easy to check the particularity of the installation of the installation of the screws in the device to be given special attention, not only to tighten but also to do some insurance measures , Such as locking fuse, fastening agent, screw riveting Department through the above means to prevent the fastening screw due to the possibility of loosening to ensure long-term safe and effective operation of the device, careful analysis of the failure is not difficult It is found that the root cause of knocking of the periphery of the roller and the fuel cam is that the pin of the roller device pin is loosened under impact and vibration load by itself and withdraws from the pin hole of the pin so that the pin axis is free So as to tilt the roller guide device in the direction of è‰ è‰‰ so that the original surface contact between the roller and the cam becomes a line contact and the area of ​​its force is significantly reduced and the material reaches fatigue under a strong impact load Limits and fragmentation.
Arrived in the host after the fourth cylinder high-pressure pump roller gear unit inspection, the results confirmed our analysis is correct. The pin of the roller pin has been loosened by about 1/3 of the screw thread. When the roller device is lifted out of the lead, the pin shaft slides out of the free end of the pin hole. Thus, the other of the host cylinder may also be late or sooner or later a similar failure, so we will be the remaining five high-pressure pump cylinder wheel guide unit removed to check and found that the pin wheel pinch screw tight After the corresponding anti-loose insurance are not done, using a hexagonal wrench a little effort can be released. In the absence of screw fastening agent on board, we take the method of tightening the stop screw and riveting the bolt with 2 to 3 points around the screw as a safety measure to ensure that the stop screw is easily released to prevent Similar incidents happen again. Later, MAN-B & W company maintenance engineer in Brazil came to help crew change the host cylinder 4 fuel cam. In the meantime, the engineer verified our inspection of the roller guide device of the high-pressure oil pump of the remaining cylinders of the main engine and the measures taken and confirmed that the measures we adopted were completely correct.
This is a mechanical accident that I experienced in my work practice. On the one hand, the device is not a wearing part of regular maintenance and repair, and is seldom disassembled under normal circumstances. On the other hand, because of its strong concealment, The screw has been loose and out of the pin stop hole, once the device is disassembled pin axis automatically fall, otherwise it is difficult to consider to check this only deep within the hole within the hexagonal screw. More importantly, according to the norms of safe navigation of ships, there is no mandatory requirement that spare parts such as roller guides or cams must be provided. In the event of such an accident, the vessel in navigation is extremely difficult to handle and poses a serious threat to the safety of the ship. Therefore, to remind colleagues here, I hope to give everyone help and reference.
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