Marine low-speed diesel engine and safety protection device for breakage of cylinder cover bolt of marine low-speed diesel engine

Abstract

The utility model discloses a marine low-speed diesel engine and a safety protection device for breakage of a cylinder cover bolt of the marine low-speed diesel engine. The device is mainly composed of a two-half type conical lining and a locking hose clamp, the lining is made of 25CrMoA alloy steel, the inner wall of the lining is matched with a bolt, and the outer wall of the lining is in a cone shape of 5-15 degrees; and the hose clamp is arranged in a groove at the lower part of the bushing. During installation, a 10mm gap is kept between the lining and a cylinder body installation hole, when the bolt is broken, the lining moves upwards along with the bolt and forms friction braking with the installation hole, and the displacement is limited within 200mm. The utility model has the characteristics of immediate braking, reliable structure, strong adaptability and the like, solves the potential safety hazard of flying after the traditional bolt is broken, and does not influence the normal maintenance. By optimizing the taper of the lining and the anti-loosening design of the hose clamp, the long-term effectiveness of the device under the working conditions of high temperature and high pressure is ensured, the device is particularly suitable for various types of MAN-ES series, and the operation safety of a diesel engine is remarkably improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of marine low-speed diesel engine safety protection, in particular to a marine low-speed diesel engine and a safety protection device and anti-fracture method for cylinder cover bolt fracture thereof. BACKGROUND

[0002] The cylinder cover stud of the marine low-speed engine is an important component of the diesel engine combustion part, the stud connects the cylinder cover, the cylinder liner and the cylinder body into a whole, and then forms a closed combustion chamber space through the cylinder gasket and the piston assembly. Taking the S60ME-C8.5 main engine as an example, the burst pressure of the combustion chamber of the marine low-speed engine is 170 bar. This burst pressure is very high, in order to ensure the sealing of the combustion chamber, the cylinder cover stud needs to use a hydraulic stretcher and a hydraulic nut to tighten under the pressure of 1500 bar. The burst pressure and the tightening hydraulic pressure of the cylinder cover stud will be different according to different engine models, and the burst pressure and the tightening torque of the high version main engine will be higher. Therefore, the requirement for the cylinder cover stud is very high, and the cylinder cover stud is generally made of high-quality chromium-nickel-molybdenum alloy steel. However, during the operation of the diesel engine, the cylinder cover stud is subjected to high pressure pulse pressure for a long time, and the high position of combustion will also be radiated to the surrounding of the cylinder cover stud, which is in a long-term harsh working condition. In actual operation, there are cases of thread fracture between the cylinder cover stud and the cylinder body. According to the current design of the connection mode, the thread of the cylinder cover stud at the bottom of the cylinder body is broken, and since the cylinder stud is in a high-pressure tension state before the fracture, the cylinder stud will be launched upward from the original position when it suddenly breaks. This situation will pose a potential risk to other equipment and even personnel on the main engine, and in severe cases, it may cause personal injury or fatal accidents.

[0003] Therefore, in order to avoid personal injury in case of accident, a friction brake safety device is needed to limit the movement of the stud and reduce the distance of the stud when the lower thread breaks, thereby reducing the risk. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the utility model provides a safety protection device and anti-fracture method for cylinder cover bolt fracture of marine low-speed diesel engine, which forms friction brake and limits the flying distance of the bolt when the bolt is broken through the cooperation of the two half conical bushings and the locking ferrule, thereby avoiding equipment damage and personal injury.

[0005] The technical solution of the utility model is as follows:

[0006] A safety protection device for cylinder cover bolt fracture of marine low-speed engine, characterized in that it comprises:

[0007] Two half cone bushings, composed of two symmetrical half structures, are sleeved on the cylinder head bolt, the inner wall of which matches the outer diameter of the cylinder head bolt, and the outer wall is in a conical structure, used to form friction braking with the cylinder mounting hole when the bolt breaks;

[0008] Locking collars are arranged at the grooves of the lower part of the two half cone bushings, used to fasten the two half cone bushings on the bolt;

[0009] A predetermined gap is arranged between the two half cone bushings and the cylinder mounting hole, forming progressive friction braking when the bolt breaks.

[0010] Further, the two half cone bushings are made of 25CrMoA alloy steel, and the taper angle is 5°-15°.

[0011] Further, the locking collar comprises an annular collar belt and an adjustable bolt fastening mechanism, the head of which is arranged outwardly, facilitating fastening by using an internal hexagonal wrench.

[0012] Further, the conical outer wall of the bushing and the inner wall of the cylinder mounting hole maintain a 10mm spacing under normal working conditions.

[0013] Further, when the bolt breaks, the bushing and the locking collar jointly limit the upward movement of the bolt to not more than 200mm.

[0014] On the other hand, the utility model provides a kind of anti-fracture method of marine low-speed diesel engine cylinder head bolt, which is characterized by comprising the following steps:

[0015] Step 1. The two half cone bushings are sleeved on the cylinder head bolt and pushed up to contact the lower edge of the cylinder mounting hole;

[0016] Step 2. The two half cone bushings are moved down by 8-12mm to ensure that they are not in contact with the inner wall of the mounting hole;

[0017] Step 3. The locking collar is installed at the groove of the two half cone bushings and fastened to form an integral body with the bushing and the bolt;

[0018] Step 4. Repeat the above steps until all the cylinder head bolts are installed with the safety device.

[0019] Further, in step (3), the locking collar is fastened to a preset torque value using a torque wrench.

[0020] Third, the utility model provides a kind of marine low-speed diesel engine, which is characterized by that the cylinder head bolt is installed with the above safety protection device.

[0021] Further, the safety protection device is suitable for different cylinder diameter models, and only the size of the bushing and the locking collar needs to be adjusted.

[0022] Compared with the prior art, the safety protection device has the following beneficial effects:

[0023] 1) Instant braking, preventing flying: when the bolt breaks at the thread root, the bushing moves up with the bolt, its conical outer wall contacts the inner wall of the cylinder body mounting hole, and the bolt displacement is strictly limited within 200mm through progressive friction braking, completely avoiding the risk of high-speed flying.

[0024] 2) Reliable structure, simple installation: the 25CrMoA alloy steel bushing can withstand high temperature (≤400℃) and high pressure working conditions of the diesel engine. The locking thimble ensures that the device does not loosen under long-term vibration and moves synchronously with the bolt. When operating normally, the bushing maintains a 10mm gap with the mounting hole, completely unaffected by the bolt stress state; only when it breaks, the braking function is triggered, realizing the "fail-safe" mode.

[0025] 3) Strong adaptability, convenient maintenance: by adjusting the inner diameter, taper and thimble size of the bushing, it can be adapted to different cylinder diameters of the MAN-ES series, such as S60ME-C8.5 to G95ME-C10.5 models. The split bushing design facilitates disassembly and does not affect the daily maintenance of the bolt or the use of the hydraulic stretcher. The thimble design with external bolt head makes the inspection and re-tightening operation simple and efficient. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Cylinder head stud installation schematic

[0027] Figure 2 Cylinder head stud fracture position schematic

[0028] Figure 3 Two-piece conical bushing

[0029] Figure 4 Locking thimble

[0030] Figure 5 Friction brake safety device installation schematic DETAILED DESCRIPTION

[0031] The technical solutions of the utility model will be described in detail below in combination with the drawings and examples, but should not limit the protection scope of the utility model.

[0032] As shown in Figure 3 and 4 , a safety protection device for cylinder head bolt fracture of a marine low-speed diesel engine, comprising:

[0033] Two-piece conical bushing: made of 25CrMoA alloy steel, with high mechanical strength and high temperature resistance. The bushing is designed as a symmetrical two-piece structure, easy to install, the inner wall matches the outer diameter of the bolt, and the outer wall is conical, which can form friction contact with the cylinder body mounting hole.

[0034] Locking collar: made of high-strength stainless steel, with adjustable bolt fastening structure, used to tightly fix the two-piece bushing on the bolt, ensuring that it moves synchronously with the bolt when the bolt breaks.

[0035] The safety steps are as follows:

[0036] Step 1. Install the two-piece conical bushing

[0037] Put the two-piece conical bushing (part 1) on the cylinder head bolt and push it upwards along the bolt until the top of the bushing touches the lower edge of the cylinder block mounting hole.

[0038] Then, back off the bushing about 10mm, ensuring that the conical outer wall of the bushing does not directly contact the inner wall of the cylinder block mounting hole, avoiding affecting the normal stress of the bolt.

[0039] Step 2: Install the locking collar

[0040] Install the locking collar (part 2) at the annular groove at the lower part of the bushing, ensuring that the collar bolt is facing outward for subsequent tightening operation.

[0041] Use an internal hex wrench to tighten the collar bolt step by step, tightly fixing the bushing with the bolt to form an integral structure.

[0042] Step 3: Repeat the installation to all bolts

[0043] Follow the same method to install the safety device on all cylinder head bolts, ensuring that each bolt has a breakage protection function.

[0044] After installation, each cylinder head stud has a bushing and a collar. Under normal operating conditions, the bolt is kept in a fastened state under the action of pre-tightening force, the bushing does not contact the cylinder block mounting hole, and the bolt stress is not affected. When the bolt breaks at the bottom thread (as shown in Figure 2 At the moment of breakage, the bolt is ejected upwards under the action of residual pre-tightening force. At this time: the bushing and the collar move upwards with the bolt, the conical outer wall of the bushing contacts the inner wall of the cylinder block mounting hole, forming a progressive friction brake. Through experimental verification, the maximum upward movement distance of the bolt is limited to about 200mm, effectively preventing it from flying out completely. When the cylinder head stud breaks, it ensures that other parts of the main machine are not damaged and does not pose a danger to personnel's personal safety.

[0045] This device is suitable for low-speed diesel engines of different cylinder diameters. Only the size of the bushing and the collar needs to be adjusted according to the bolt diameter, and the installation method remains the same.

[0046] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A safety device for a fracture of a cylinder head bolt of a marine low-speed engine, characterized in that The application relates to a safety protection device for cylinder head bolts. The safety protection device comprises: a two-halves conical bushing, which is composed of two symmetrical halves, is sleeved on a cylinder head bolt, the inner wall of the bushing matches the outer diameter of the cylinder head bolt, and the outer wall of the bushing is in a conical structure and is used for forming a friction brake with a cylinder mounting hole when the bolt is broken; a locking collar, which is arranged at a groove in the lower part of the two-halves conical bushing and is used for fastening the two-halves conical bushing on the bolt; 2. The safety guard of claim 1, wherein, a predetermined gap is arranged between the two-halves conical bushing and the cylinder mounting hole, and a progressive friction brake is formed when the bolt is broken.

3. The safety guard of claim 1, wherein, The two-halves conical bushing (1) is made of 25CrMoA alloy steel, and the taper angle is 5-15 degrees.

4. The safety guard of claim 1, wherein, The locking collar comprises an annular collar belt and an adjustable bolt fastening mechanism, and the bolt head is arranged towards the outside, so that an internal hex wrench can be used for fastening.

5. The safety guard of claim 1, wherein, The conical outer wall of the bushing (1) and the inner wall of the cylinder mounting hole keep a 10mm spacing under normal working conditions.

6. A marine low-speed diesel engine, characterized by When the bolt is broken, the bushing and the locking collar jointly limit the upward movement distance of the bolt to not more than 200mm.

7. The low-speed marine diesel engine according to claim 6, characterized in that The cylinder head bolt is provided with the safety protection device according to any one of claims 1-5. The safety protection device is suitable for different cylinder diameter models, and only the sizes of the bushing and the locking collar need to be adjusted.

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