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The transmission system of an oil drilling rig is a device that transfers the energy from the power source to various working machines, enabling the hoisting, rotation, circulation and other systems of the drilling rig to work in coordination. The following is a detailed introduction to its composition and characteristics: Ⅰ. Components Gearbox: It is used to reduce the rotational speed and increase the torque to meet the rotational speed and torque requirements of different working machines. For example, the drawworks requires a large torque to hoist and lower the drilling tools. Through the gearbox, the high rotational speed and low torque of the power source can be converted into the low rotational speed and high torque required by the drawworks. Clutch: It is a component in the transmission system used to connect and cut off the power transmission. It allows the working machine to engage with the power source when needed to obtain power for operation, and can also cut off the power when not needed to achieve the independent operation or stop of the working machine. Common types include jaw clutches and friction clutches. Coupling: It is used to connect the shafts of different components, transmit torque and rotational motion, and at the same time compensate for the installation errors and relative displacements between the shafts. For example, when connecting the shafts of the power source and the gearbox, and the gearbox and the working machine, the coupling can ensure the effective transmission of power and adapt to the slight deformation and displacement of the shafts during the operation of the equipment. Drive shaft: It is an important component for power transmission, usually made of high-strength steel, and is used to transmit torque and rotational motion between different components. The drive shaft needs to have sufficient strength and stiffness to withstand the huge torque and bending moment during the transmission process. Chain and sprocket for workover rig: In the transmission system of some oil drilling rigs, chains and sprockets are used to transmit power. The chain is put on the sprocket, and the rotation of the sprocket drives the chain to move, thus transmitting power from one component to another. Chain drive has the advantages of high transmission efficiency and can adapt to a relatively large center distance. Belt drive device: Generally composed of banded V belts and pulleys, it transmits power through the frictional force between the belt and the pulleys. Belt drive has the characteristics of smooth transmission, buffering and vibration absorption, and overload protection. It is often used in parts where the requirements for transmission accuracy are not high and a certain degree of flexible transmission is needed. Ⅱ. Transmission ModesIn actual oil drilling rigs, a composite transmission system that combines multiple transmission modes is usually adopted according to factors such as the type of the drilling rig, working conditions, and performance requirements, so as to give full play to the advantages of various transmission modes and meet the complex requirements of oil drilling operations. Mechanical Transmission System Composition and Functions of Components Gear transmission: Composed of meshing gears, it transmits power and motion through the meshing of the teeth of the gears. It can achieve a large transmission ratio, has high transmission efficiency, a compact structure, and reliable operation. It is often used in components such as gearboxes and transfer cases to meet the rotational speed and torque requirements of different working machines. Chain transmission: Composed of a chain and sprockets, the chain is put on the sprockets, and the rotation of the sprockets drives the chain to move, thereby transmitting power to other components. It is suitable for the transmission between two shafts with a relatively large center distance, can adapt to harsh working environments, and has a relatively high transmission efficiency. For example, the winch drive part of the drilling rig may use chain transmission. Belt drive: Generally composed of a belt and pulleys, it relies on the frictional force between the belt and the pulleys to transmit power. It has the advantages of smooth transmission, buffering and vibration absorption, and the belt will slip on the pulley to play a protective role when overloaded. It is often used in the transmission of auxiliary equipment of the drilling rig where the requirements for transmission accuracy are not high and a certain degree of flexible transmission is needed. Characteristics: The mechanical transmission system has high transmission efficiency, reliable operation, can transmit large torque and power, has a relatively simple structure, and low maintenance cost. However, the transmission ratio is fixed, the flexibility is poor, there are many components, and the requirements for installation and debugging are relatively high. Hydraulic Transmission System Composition and Functions of Components Torque converter: It is the core component of the hydraulic transmission system, mainly composed of a centrifugal pump impeller, a turbine, and a guide wheel. The pump impeller is connected to the power source and converts mechanical energy into the kinetic energy of the liquid; the turbine is connected to the working machine and converts the kinetic energy of the liquid into mechanical energy for output; the guide wheel plays the role of changing the flow direction of the liquid and increasing the torque. The torque converter can automatically change the output torque and rotational speed under different working conditions, enabling the drilling rig to have good adaptability. Hydraulic pump: It converts mechanical energy into hydraulic energy, provides high-pressure oil for the hydraulic transmission system, and drives the execution components such as the torque converter and the hydraulic motor to work. Hydraulic motor: It converts hydraulic energy into mechanical energy and is used to drive the working machines of the drilling rig, such as the drawworks and the oil drilling rotary table. The hydraulic motor has good speed regulation performance and a large torque output capacity. Characteristics: The hydraulic transmission system has good overload protection performance. When the working machine encounters an overload, the torque converter will automatically slip to protect the equipment from damage. At the same time, it has stepless speed regulation performance, can smoothly adjust the rotational speed and torque according to the work requirements, and has strong buffering and vibration absorption capabilities, which can make the start and operation of the drilling rig more stable. However, the transmission efficiency of the hydraulic transmission system is relatively low, especially at low loads, and the system structure is complex, with high maintenance costs. Electric Transmission System Composition and Functions of Components Generator: It converts mechanical energy into electrical energy and provides a power source for the electric transmission system. It is usually driven by a diesel engine or other power sources to generate three-phase alternating current. Electric motor: It converts electrical energy into mechanical energy and drives each working machine of the drilling rig. According to different working requirements, different types and powers of electric motors can be selected. For example, DC motors have good speed regulation performance, and AC variable frequency motors have the advantages of high efficiency, energy conservation, and a wide speed regulation range. Frequency converter: It is used to adjust the power frequency of the AC motor, thereby achieving stepless speed regulation of the motor. By changing the output frequency of the frequency converter, the rotational speed of the motor can be precisely controlled to meet the requirements of different working conditions during the drilling process. Control system: It includes various electrical components, controllers, and sensors, etc., and is used to monitor, control, and protect the electric transmission system. It can realize operations such as starting, stopping, speed regulation, and forward and reverse rotation of the motor, and at the same time monitor parameters such as the voltage, current, and temperature of the system. When an abnormal situation occurs, it will take timely protective measures to ensure the safe operation of the system. Characteristics: The electric transmission system has high transmission efficiency, good speed regulation performance, can achieve precise speed control and torque control, is easy to realize automation and intelligent control, and can improve the efficiency and quality of drilling operations. In addition, the electric transmission system operates stably, has low noise, and causes little pollution to the environment. However, the electric transmission system requires a reliable power supply, has high requirements for the stability of the power grid, and the equipment investment cost is relatively large. Composite Transmission System Composition and Forms: The composite transmission system is a transmission system that combines multiple transmission modes such as mechanical transmission, hydraulic transmission, and electric transmission. Common composite transmission forms include mechanical-hydraulic composite transmission, mechanical-electric composite transmission, and hydraulic-electric composite transmission, etc. For example, in some large oil drilling rigs, the mechanical-hydraulic composite transmission mode of diesel engine-torque converter-gearbox may be adopted to drive the winch, taking advantage of the good adaptability of the torque converter and the high efficiency of gear transmission to meet the working requirements of the winch; at the same time, the electric transmission mode is adopted to drive the rotary table to achieve precise speed regulation and control of the rotary table. Characteristics: The composite transmission system can give full play to the advantages of various transmission modes, select appropriate transmission modes according to the characteristics and working condition requirements of different working machines of the drilling rig, thereby improving the overall performance and adaptability of the drilling rig. It can ensure the reliability and transmission efficiency of the drilling rig while achieving better speed regulation performance and automation control level. However, the system structure is complex, and the design, installation, and maintenance are more difficult.    

The hoisting sheaves are an important part of the hoisting system of oil drilling rigs. The sheaves of crown block and traveling block jointly form a sheave block, which is connected to the drawworks through wire ropes. By utilizing the principles of the sheave block to save force and change the direction of the force, the hoisting and lowering of the drilling tools are achieved to meet the needs of oil drilling operations. The following is the relevant introduction: Ⅰ. Structure and Principle Structure: The hoisting sheave is usually composed of parts such as the sheave body, bearings, sheave shaft, and rope groove. The sheave body is generally made of high-strength alloy steel or cast steel to withstand huge loads. The bearings are installed on the shaft to enable the sheave to rotate flexibly. The rope groove is used to accommodate the wire rope, and its shape and size are matched with the wire rope to ensure that the wire rope will not jump out of the groove during operation. Principle: The sheaves of the crown block and the traveling block form a sheave block, which is connected to the drawworks through wire ropes. When hoisting, the drum of the drawworks winds the wire rope, and through the action of the sheave block, the drilling rig hook and the drilling tools are lifted. When lowering, the drilling tools descend under their own weight, and the lowering speed of the hook is controlled by the braking mechanism and auxiliary brakes of the drawworks. Ⅱ. Functions Saving Force: Through the combination of the sheave block, the amplification of force can be achieved, enabling the drawworks to hoist or lower heavier drilling tools with less force, reducing the requirements for the power and driving force of the drawworks. Changing the Direction of Force: It changes the pulling force direction of the wire rope from the horizontal direction of the drawworks to the vertical direction, adapting to the hoisting and lowering requirements of the drilling tools, and can transmit the force to the required position. Improving Hoisting Efficiency: The coordinated operation of multiple sheaves increases the number of winding turns of the wire rope, reduces the wear of the wire rope, and also improves the stability and reliability of the hoisting system, thus improving the efficiency of drilling operations. Ⅲ. Crown Block Sheaves Location and Function: Installed at the top of the derrick, it is a set of fixed sheaves and is the highest point of the entire hoisting system. Its main function is to change the direction of the wire rope and transmit the pulling force of the drawworks to the traveling block and the drilling tools to achieve the hoisting and lowering of the drilling tools. There are usually a large number of crown block sheaves, and the number and size of the sheaves vary according to the model of the drilling rig and the hoisting capacity. Structural Features: The crown block sheaves are usually composed of multiple sheaves, which are installed on a common frame or wheel shaft. The number of sheaves is determined according to the drilling depth, hoisting weight, and system design requirements. Common configurations include 3 wheels, 4 wheels, 5 wheels, etc. The sheaves are generally made of high-strength alloy steel to withstand huge pulling forces and wear. Their surfaces are specially treated, such as quenching and chrome plating, to improve hardness and wear resistance and reduce the wear of the wire rope. The bearings of the sheaves are high-performance rolling bearings, which can withstand large radial and axial loads, ensure the flexible rotation of the sheaves, and reduce the frictional resistance. Working Principle: When the drawworks pulls the crown block sheave through the wire rope, the sheave rotates around the shaft. Due to its fixed position at the top of the derrick, the direction of the wire rope is changed, allowing the wire rope to be vertically connected to the traveling block downward, converting the horizontal pulling force of the drawworks into the vertical pulling force for hoisting the drilling tools. Ⅳ. Traveling Block Sheaves Location and Function: The traveling block sheaves are located below the crown block, and they are movable sheaves. They are connected to the crown block through wire ropes and are also connected to the hook, which in turn suspends the drilling tools. The function of the traveling block sheaves is to cooperate with the crown block sheaves to jointly complete the hoisting, lowering, and suspension operations of the drilling tools. At the same time, during the hoisting process, they share the pulling force of the wire rope, reducing the load borne by a single sheave. Structural Features: The structure of the traveling block sheaves is similar to that of the crown block sheaves, and they are also a sheave block composed of multiple sheaves. The material, manufacturing process, and surface treatment method of its sheaves are basically the same as those of the crown block sheaves to meet the same strength and wear resistance requirements. The frame structure design of the traveling block needs to consider the connection with the hook and the overall stability to ensure smooth operation during the hoisting and lowering of the drilling tools and reduce shaking and swinging. Working Principle: In the drilling operation, the wire rope passes around the crown block sheave and the traveling block sheave to form a closed system. When the drawworks pulls the wire rope, the crown block sheave and the traveling block sheave rotate simultaneously. Since the traveling block can move up and down along the derrick guide rails, it can drive the hook and the drilling tools to move in the vertical direction. During the hoisting process, multiple rope strands are formed between the crown block and the traveling block sheaves, and each rope strand shares a part of the weight of the drilling tools, thus reducing the pulling force borne by each sheave and improving the safety and reliability of the entire hoisting system. Ⅴ. To select suitable crown block and traveling block sheaves for specific oil drilling operations, the following multiple factors need to be comprehensively considered: Drilling Depth: The drilling depth directly affects the required hoisting force and the length of the wire rope. Generally speaking, the greater the depth, the greater the required hoisting force, and sheaves with higher bearing capacity should be selected. At the same time, the size of the sheave may also need to be larger to accommodate a longer wire rope. For example, for ultra-deep well drilling, large-diameter and high-strength sheaves may be required to meet the hoisting requirements. Hoisting Weight: Accurately calculate the maximum hoisting weight including the drilling tools, casing pipes, drilling fluid, etc. Select sheaves that can bear the corresponding load according to this weight. Usually, the rated load of the sheave should be 1.2 to 1.5 times greater than the maximum hoisting weight to ensure a safety margin. For example, if the maximum hoisting weight is 200 tons, the rated load of the sheave should be between 240 and 300 tons. Wire Rope Specifications: Different specifications of wire ropes need to be matched with sheaves of corresponding sizes and groove shapes. The diameter of the rope groove of the sheave should be suitable for the diameter of the wire rope. Generally, the diameter of the rope groove is 1 to 2 mm larger than the diameter of the wire rope to ensure that the wire rope can be well embedded in the rope groove and reduce wear and sliding. At the same time, the rope capacity of the sheave should also meet the length requirements of the wire rope in the drilling operation. Working Environment: If the drilling operation is carried out in special working conditions such as high temperature, high humidity, corrosive environment, or offshore, sheaves with corresponding protective performance need to be selected. For example, on offshore platforms, the sheaves should have good corrosion resistance, and stainless steel materials or sheaves treated with anti-corrosion coatings can be used. In high-temperature environments, high-temperature-resistant bearings and lubricating materials should be selected to ensure the normal operation of the sheaves. Drilling Speed: A higher drilling speed will make the sheave bear greater impact and wear. Therefore, sheaves with flexible rotation and good wear resistance need to be selected. Sheaves can be manufactured using high-precision bearings and high-quality wear-resistant materials to meet the requirements of high-speed drilling. Derrick Space: The space size of the derrick limits the size of the crown block and the traveling block, and thus affects the selection of the sheaves. According to the height, width, and bearing capacity of the derrick, select sheaves of appropriate size and structure to ensure that they can be reasonably installed and operated within the derrick without causing excessive load on the derrick. Economy: On the premise of meeting the requirements of the drilling operation, consider the cost, service life, and maintenance cost of the sheaves. Select sheaves with high cost performance to reduce the overall cost of the drilling operation. For example, although some imported high-end sheaves are more expensive, they have a longer service life and better performance, and may be more economical in the long run. While some domestic sheaves have a relatively low price and can be given priority if they can meet the operation requirements. Brand and Quality: Select sheaves from well-known brands and with reliable quality to ensure their performance and safety. Sheaves of well-known brands usually go through strict quality inspection and certification, have better stability and reliability, and can reduce drilling accidents and downtime caused by sheave failures. You can refer to the usage experience and evaluations of other drilling operators to select suitable brands and models. Ⅵ. Maintenance Daily Inspection: Before and after each day's operation, check whether there are cracks, wear, and deformation on the surface of the sheave, whether it rotates flexibly, and whether the position of the wire rope in the rope groove is normal. Regular Lubrication: Select suitable lubricating grease. According to the equipment instruction manual and the actual working situation, lubricate once every 100 to 200 working hours or once a week. When injecting oil, ensure that the lubricating grease is fully filled into the bearing and journal parts. Cleaning and Maintenance: Regularly remove impurities such as oil stains, dust, and drilling fluid on the surface of the sheave. Disassemble and clean the sheave at regular intervals, clean the internal oil stains and impurities, dry it, and then reassemble it and add lubricating grease. Regular Detection and Calibration: Use professional measuring tools to regularly measure the dimensions of the sheave rope groove and hub, monitor the wear situation, and replace the sheave in time when the wear amount reaches the limit standard. Regularly calibrate the crown block and traveling block sheave block to ensure that all sheaves are in the same plane and that the levelness and perpendicularity of the sheaves meet the requirements.