Design and installation of crankshaft connecting r

Design and installation of crankshaft connecting rod bearing of mud pump Abstract: with the continuous deepening of market economy, the rapid development of infrastructure, the rapid development of mechanical and electrical engineering construction, and the debugging of mechanical equipment installation has also attracted much attention. According to the construction of mechanical equipment installation engineering, this paper focuses on the debugging of mechanical equipment installation process

during the installation of mechanical equipment, single machine commissioning and linkage commissioning are usually carried out to verify the reliability of the normal operation of the equipment. However, in practical work, many unexpected abnormal phenomena are often faced. Only by effectively analyzing and dealing with these "abnormal phenomena" in actual work can the mechanical equipment installation work normally

I. Introduction to mechanical equipment installation

mechanical equipment installation means that the equipment is transported from the manufacturer to the construction site, with the help of some tools and instruments, after necessary construction, the equipment is correctly installed at the predetermined position, and the use conditions are achieved through commissioning and operation. Whether a mechanical equipment can be put into production smoothly, whether it can give full play to its performance, extend the service life of the equipment and improve the quality of the products depends largely on the quality of the installation of mechanical equipment

1. The general process of mechanical equipment installation

the installation process of various mechanical equipment generally must go through: hoisting and transportation, equipment unpacking inspection, setting out in place, equipment fixation, cleaning, parts assembly and component assembly adjustment, test run, project acceptance, etc. The difference is that in these processes, different methods are adopted for different mechanical equipment. For example, in the installation process, the split installation method is adopted for large equipment, while the integral installation method is adopted for small equipment

2. The construction content of mechanical equipment installation

mainly includes the lifting and transportation of equipment, the assembly of mechanical equipment as a whole and parts, the installation of pipe fittings, cutting and welding, the assembly of internal parts of various containers, the installation of motors, the installation, commissioning, pressure test and test run of instruments and automatic control devices

3. Mechanical equipment installation and construction requirements

first, strictly ensure the quality of equipment installation, and carry out correct construction according to the design drawings, equipment structure drawings, installation instructions and construction acceptance specifications, quality inspection and evaluation standards and operating procedures. Second, adopt scientific but practical construction methods to speed up the project progress and ensure that it is put into production on schedule

II. Debugging during mechanical equipment installation

1 The bearing temperature is too high

there are three reasons for the abnormal increase of fan bearing temperature: poor lubrication, insufficient cooling, and abnormal bearing. The bearing of the centrifugal fan is placed outside the fan. If it is contrary to the short-term development of the vehicle, the temperature rise caused by peeling, pitting and clearance increase due to bearing fatigue wear. Generally, it can be judged by listening to the sound of the bearing and measuring the vibration. In case of poor lubrication and insufficient cooling, it can be judged by visual methods such as visual inspection and hand mold. The bearing of axial flow fan is concentrated in the bearing box and placed below the air inlet chamber. When the bearing temperature is high, it is difficult to judge whether there is a problem with the bearing or lubrication and cooling because the fan is running. In the actual commissioning and operation, the problems should be solved from the following aspects

first, whether the refueling is appropriate, the bearing housing should be refueled according to the requirements of the manufacturer's instructions. Sometimes the temperature of the bearing will be high after oiling, mainly due to excessive oiling. At this time, the phenomenon is that the temperature continues to rise. After reaching a certain point (generally 10-15 ℃ higher than the normal operating temperature), it will remain unchanged, and then gradually decline

second, the cooling fan is small and the cooling air volume is insufficient. The smoke temperature at the induced draft fan is 120-140 ℃, if there is no effective cooling of the bearing housing. The bearing temperature will rise. The relatively simple and power-saving solution is to set compressed air cooling in the hub side bearing. When the temperature is low, the compressed air cooling can not be turned on, and when the temperature is high, the compressed air cooling can be turned on. Check the bearing housing after confirming that the above problems do not exist

2. Bearing vibration

fan bearing vibration is a common fault in operation. The vibration of the fan will cause faults such as bearing and blade damage, bolt looseness, casing and air duct damage, which seriously endangers the safe operation of the fan

the fan itself causes vibration. Generally speaking, its vibration source comes from itself. Such as the non-uniformity of materials of rotating parts; Rotor mass imbalance caused by manufacturing error; Poor installation and maintenance quality; Poor adjustment of fan operation when load changes; The rotor is worn or damaged, and the front and rear guide vanes are worn and deformed; The opening of inlet and outlet baffles is not adjusted in place; Bearing and bearing seat failure, etc. Can make the fan vibrate under the action of small interference force. In this regard, during the operation of the fan. A series of corresponding treatment measures must be taken to reduce or eliminate the vibration, such as the anti-wear treatment of fan impeller and rear guide vane, the use of imported high-quality products for bearings, the anti loosening measures for the high-strength bolts connecting the bearing housing and the end plate of the core barrel, the improvement of the support and fixation of the core barrel, and the addition of tie bars; Strictly maintain the process quality, and increase the fan operation vibration monitoring device, etc

the vibration of the fan is caused by the vibration of the air duct system. The vibration of the flue and air duct usually causes the forced vibration of the fan. This is a situation that is easy to appear and easy to ignore in production. The diffuser at the outlet of the fan increases with the load. The inlet and outlet air volume increases. The vibration will also change with it. Generally, the lower part of the diffusion cylinder has only four fulcrums, and the joint asbestos canvas on the other side is a soft joint. In this way, 60% of the weight of the whole diffusion cylinder is suspended. In view of this situation, a movable fulcrum is added under the outlet end of the diffuser, which can be raised, lowered and moved. When the load of the unit changes, just fine tune the fulcrum to eliminate the vibration

3. Surge

during the operation of the fan, when the flow continuously decreases to the qmin value, the air flow entering the cascade separates, and moves along the rotation direction of the impeller in the separation area at a speed smaller than the rotation angle speed of the impeller, which is rotation disengagement. When the rotation disengages and spreads to the whole channel, the outlet pressure of the fan will suddenly decrease significantly, and the pressure in the pipe will not decrease immediately, so the gas pressure in the pipe is greater than the pressure at the outlet of the fan, and the gas in the pipe flows back to the fan until the pressure in the pipe drops below the outlet pressure of the fan. Then, the blower starts to supply air to the pipe again to press the backflow gas out, which reduces the flow in the machine, the pressure drops suddenly again, and the gas in the pipe flows back to the fan again. In this cycle, periodic low-frequency and high amplitude pressure pulsation and air flow oscillation occur in the whole system, and make a big sound, and the machine vibrates violently, so that it cannot work, which is surge. Whether to enter the surge condition can be judged according to the different conditions of fan operation

first, listen to the air flow noise of the fan outlet pipe. When approaching the surge condition, the noise emitted by the air flow in the outlet pipe is high and low, resulting in periodic changes. When entering the surge condition, the noise immediately increases sharply, and even bursts appear

second, observe the changes of fan outlet pressure and inlet flow. During normal operation, the outlet pressure and inlet flow change little. When entering the surge zone, both change greatly

third, observe the vibration of the body. When entering the surge zone, the machine body and bearings will vibrate strongly. The main method to prevent surge is to use the air outlet pipe to vent. A bypass pipe is set on the air outlet pipe. Once the air volume decreases to the qmin value, the valve on the bypass pipe will automatically open to vent. At this time, the inlet flow will increase, and the working point can be moved from the surge area to the stable working area, thus eliminating the possibility of stall and surge caused by small inlet flow and too large angle of attack. When the inlet guide vane is used to adjust the air volume, with the change of working conditions, the guide vane rotates to change the channel area to meet the requirements of new working conditions, so as to avoid air flow stall and effectively prevent fan surge

4. The movable blade of axial flow fan is adjusted by driving the slide valve by the transmission mechanism to change the oil pressure difference on both sides of the hydraulic cylinder. In the operation of axial flow fan, sometimes it is difficult or completely impossible to adjust the moving blades. This phenomenon is usually considered to be caused by the failure of the fan regulating oil system and the damage of the internal regulating mechanism of the hub. However, in practice, there is usually another reason. There is a certain gap between the moving blade and the hub of the fan to adjust the angle of the moving blade, but incomplete combustion causes carbon scale or dust to block the gap, which makes it difficult to adjust the moving blade. The phenomenon of jamming of moving blades is common in oil fired boilers and boilers using water film dust removal. The main measures to solve it are:

first, during commissioning and operation, try to make the fuel oil or coal burn fully, reduce carbon black, appropriately increase the exhaust gas temperature and inlet air temperature, and avoid the condensation of sulfur in the flue gas in the air preheater

second, set a steam purging pipe at the inlet of the impeller. When the fan stops, clean the impeller to keep it clean. The steam pressure is ≤ 0.2MPa and the temperature is ≤ 200 ℃

with the rapid development of modern industry, there are more and more special working conditions and special structures. Restricted by special circumstances, various non-standard bearings need to be selected. The bearing designed by our company for the crankshaft connecting rod of a mud pump belongs to a special structure. When the mud pump works, it drives the crankshaft to rotate through gear transmission, and drives the piston to do reciprocating motion through the connecting rod connected to the crankshaft and the piston to realize the work of the pump

1 crankshaft bearing

it can be seen that there is a large radial impact load when the piston is reciprocating, so cylindrical roller bearings that can withstand a large radial impact load are used on the crankshaft. Due to the limitation of crankshaft structure, the integral bearing cannot be installed, and the bearing with split structure or tight sleeve structure needs to be used. It can be seen from Figure 1 that there is no positioning device at the bearing fitting, so it is impossible to position the bearing and fasten the bearing. Therefore, four row cylindrical roller bearings are used. Increase the inner diameter of the bearing and design it into a tapered hole structure to facilitate installation. The set sleeve is a two-part structure. After the other parts of the bearing group are successively installed into the crankshaft mating surface to assemble the bearing, the two halves of the set sleeve are matched with the conical surface of the crankshaft bearing inner diameter, and locked with a locknut to fix the bearing on the crankshaft. The installation is simple and convenient

after the mud pump works for a period of time, the tightening sleeve will mesh with the inner diameter surface of the bearing. When the equipment establishing the information service platform is repaired or the bearing is replaced, it is difficult to disassemble the bearing. Therefore, when designing the tightening sleeve, add an oil circuit in the tightening sleeve (see Figure 2), and the high-pressure oil is pressed in from the oil inlet, forming a hydraulic oil film on the mating surface with the bearing through the oil circuit, so that the friction resistance of the contact surface is reduced and the bearing is easy to disassemble, Therefore, the tightening sleeve can also be used for removing the sleeve

2 bearing for piston

at the connection between piston and connecting rod, the radial section is small, which not only requires that the bearing can bear large radial load, but also requires simple and compact structure and convenient disassembly and assembly. Therefore, four row cylindrical roller bearings are used. It can be seen from Figure 3 that the outer ring and roller are used as outer components. As the inner ring of the bearing, the cylindrical pin can save space, increase the diameter of the rolling element and improve the bearing capacity. At the same time, the friction coefficient of cylindrical roller bearings is low