Current status and prospects of hydraulic wrench industry

　　Now the scope of use of hydraulic wrenches (fàn wéi) in China is very wide. In the construction, overhaul, and emergency repairs in the ship (interpretation: general name of the ship) engineering, petrochemical, construction, electric power, mining, metallurgy and other industries, hydraulic wrenches are a kind of installation and disassembly of large-size bolts. Very important tool. It has the irreplaceability of other tools (substituting one substance for another (mostly the strong can replace the weak)). Not only is it easy to use and light, but the torque provided is huge and very accurate. The torque repeatability is about ±3%. According to relevant statistics, about 50% of equipment operation failures are caused by bolt problems (Emerson). At the same time, the number of major equipment accidents caused by bolt problems is also very staggering. Therefore, in the process of equipment installation, maintenance and gun repair, The torque for bolt tightening and disassembly is strict in most cases, and it is difficult to meet the requirements by manual methods. For bolts that provide large torques, hydraulic wrenches are the ideal choice. Hydraulic wrenches are mainly divided into two categories: hydraulic square-drive wrenches and hydraulic hollow wrenches.

　　1 Discussion on optimization methods, basic conditions and experimental methods of hydraulic wrenches

　　Because hydraulic wrenches are often used in small spaces and locations where transportation is very inconvenient during construction, the size and weight of the wrench are the most important indicators. In order to reduce the size of parts, the use of high-strength (strength) alloy materials and heat treatment are common methods. At the same time, finite element analysis is used to optimize the design to reduce the size and weight of components, which is also a very important part. This article will analyze the optimization of hydraulic wrench size from these two aspects. At the same time, how to obtain high-quality products, this article also elaborated on basic manufacturing conditions and experimental methods.

　　1.1 Very high strength (strength) alloy material and heat treatment (chǔ lǐ) method

　　For the use of high-strength (strength) alloy materials and heat treatment methods to achieve the purpose of reducing the size and weight of parts. Due to the current widespread global trade, it is not very difficult to find high-strength materials. However, in order to further increase the strength, heat treatment and surface treatment must be adopted. For the desired component strength to reach 1000MPa or more and be stable, And the uniformity of the material strength is also extremely high (mainly due to the irregularity of the internal parts of the hydraulic square drive wrench). At present, it is difficult for domestic enterprises to achieve the strength of the internal parts of the hydraulic square drive wrench above 1000 MPa, even if they can be individually It is difficult to achieve batch stability. It is also necessary to learn more from similar products abroad, and invest more manpower and funds in a relatively long period of time, and explore and experiment more in terms of materials and heat treatment.

　　1.2 finite element analysis (finite element analysis) optimization design method

　　The optimal design method based on finite element analysis is mainly to use discrete theoretical calculations to repeatedly modify the design to achieve the optimal design. The main calculation principle is:

　　After the discretization, h-elements (further subdividing the grid) and p-element (increasing the calculation order) are used to achieve calculation convergence. The FEA mechanics calculation of the internal pawl of the hydraulic square-drive wrench shows that the local stress has exceeded 1000 MPa. Due to the rapid development of computers nowadays, the huge amount of calculation caused by the refinement of the grid is no longer a problem (Emerson). From this aspect, there is no bottleneck problem for the accuracy of the calculation. However, because the internal parts of hydraulic square-drive wrenches are more complicated, and the boundary conditions are difficult to specify, and the contact surface conditions are also difficult to simulate (definition: virtual of real things or processes) and given, the calculation can only be used as a reference for design and experiment. It cannot be completely relied upon. The results should be explored and analyzed in the model of multiple boundary conditions, and reliable data should be gradually found and compared with the corresponding experimental test results.

　　1.3 Basic conditions

　　Since hydraulic wrenches involve high-strength materials (Material) and high hydraulic pressure (currently the mainstream pressure of hydraulic wrenches is 70MPa), the requirements for some basic conditions are still very high overall. Hydraulic wrench is the abbreviation of hydraulic torque wrench. It is a professional bolt tightening tool that is powered by hydraulic pressure and provides high torque output. It is used for bolt installation and disassembly. It is often used to tighten and loosen bolts larger than one inch. The hydraulic wrench is composed of a working head, a hydraulic pump and a high-pressure oil pipe.

　　At present, there are still some gaps between domestic products and similar foreign products in terms of weight, appearance, life span, and functions. In terms of manufacturing, although there is no shortage of high-quality CNC in China, it lacks some accumulation in management and technology. The currently manufactured parts still have factors of unstable quality. At the same time, high-pressure hydraulic seals, high-pressure joints and other related basic materials still rely on imports for particularly high-strength materials.

　　1.4 Experiment method

　　Regardless of domestic or international, there are currently no product and experimental standards for hydraulic wrenches. Experiments (function experiments, lifetime experiments, reliability experiments, etc.) are the basic requirements for determining product quality. It is also the basic requirement before the product is introduced to the market, although there is no special hydraulic wrench product and experimental standard. We can still find relevant technical key points from some domestic and foreign standards (such as AMSIB30.1, ANSIB107, etc.) to formulate some enterprise standards for this product. This link is also a key point of an enterprise's research and development capabilities, a prerequisite guarantee for product quality and reliability.

　　2 Conclusions and prospects

　　This article discusses the optimization method of hydraulic wrenches. Through the related discussion of the two aspects (materials, FEA) involved in this article, the preliminary analysis (Analyse) how to make hydraulic wrench the most important index (target aim) ) The size and weight achieve the desired effect. To track and analyze the most advanced hydraulic wrenches in the world, and put forward suggestions that require long-term exploration and experimentation for the current development of this technology in China.

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