【Common Issues in Haichuan Pipeline Design】The Purpose and Principles of Installing Metal Hoses

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During the design, installation, and inspection of pipelines, various minor issues that have been overlooked or not taken into consideration are often identified. These issues are compiled into a series; this list is being updated continuously. Everyone is welcome to actively participate in discussions. This is a compilation post on common problems in Haichuan pipeline design – it’s still being updated, and discussions are welcome: https://bbs.hcbbs.com/thread-5705828-1-1.html ------------------------------------------------------------------ Purposes and principles of using metal flexible hoses 1. Advantages and applications of metal flexible hoses Metal flexible hoses feature a compact structure and secure connections. Compared to hoses made of rubber, plastic, or other materials, they offer advantages such as good flexibility, light weight, small size, easy bending, convenient installation, as well as resistance to corrosion and temperature changes. They do not age, can withstand high pressures, provide good sealing, and have a long service life. It has a 3D compensation function. In piping systems, it is an extremely effective component for temperature compensation, eliminating mechanical displacement, absorbing vibrations, and reducing noise. The use of metal hoses in the design of petrochemical plants significantly improves the quality of such engineering designs. 2. Purposes and principles of installing metal hoses 2.1 Purpose of installing metal hoses The main purpose of using metal hoses in engineering is to provide thermal compensation for movements, eliminate mechanical displacement, absorb vibrations, reduce noise, allow for flexible movement, and facilitate changes in the direction of fluid flow. 2.2 Principles for installing metal hoses In petrochemical plants, metal hoses are installed based on the following principles: 2.2.1 Large storage tanks for petrochemical products and raw materials: Installing metal hoses on the inlet and outlet pipes of large storage tanks helps prevent pipe damage caused by factors such as ground settlement and earthquakes, as well as leakage of the stored materials ； Avoid **property damage and environmental pollution. When constructing large storage tanks in earthquake-prone areas, extra attention should be paid to the installation of metal hoses. 2.2.2 Inlets and outlets of mainframes and pumps: Equipment such as pumps, compressors, and centrifuges used in engineering projects generate vibration and noise during operation, which can compromise the quality of the project as well as human health. Especially for large pump and centrifuge units, metal hoses of a certain length should be installed at their inlet and outlet ports; this helps to reduce vibration and noise, improves the quality of the installation, extends the service life of the pumps, and also facilitates their installation. 2.2.3 Tank cars and oil tankers: Metal hoses are currently commonly used for loading and unloading in trains, road tank cars, and oil tankers. Using metal hoses not only enables a sealed loading and unloading process that reduces oil evaporation, but it is also easy to install and remove, allowing for mobility and thus providing considerable convenience in operation. 2.2.4 Electronic weighing equipment: Ingredient mixing is a common practice in chemical plants, especially in polymerization units. An accurate ingredient ratio can only be achieved through precise measurement. The batching tanks that are used for weighing must not be subjected to axial forces after installation; all pipelines connected to them should be flexibly connected using metal hoses, in order to avoid any impact on the accuracy of weighing. 2.2.5 Equipment that needs to be frequently disassembled or requires some degree of movement due to process requirements: For equipment such as filters, filling devices, mobile pumps, or compressors, it is advisable to use metal hoses for connecting them to fixed equipment or piping components. 2.2.6 Others: For pipelines that pass through expansion joints in buildings, it is advisable to use flexible metal hoses for connection, in order to compensate for any differences in settlement between the two walls. In situations where there is insufficient piping space and the operating temperature is high, metal hoses are installed at the equipment connections to absorb the expansion of the piping system and eliminate the thrust exerted by the piping system on those connections. Additionally, metal hoses do not deform at low temperatures and possess good flexibility, making them widely used in low-temperature pipelines. Due to its excellent airtightness, it can be used in vacuum systems with high vacuum levels. 3. Composition and classification of metal hoses: A metal hose consists of a tube body, a mesh sleeve, and connecting fittings. Both its tube body and mesh sleeve are made of stainless steel, while the connectors are available in stainless steel and carbon steel versions depending on the process requirements. The corrugations on its tube body come in spiral and ring shapes, and it can be divided into two main categories based on the connection method: flange connection and pipe fitting connection. The flanges of metal flexible hoses can be equipped with international flanges, flanges in accordance with the standards set by the Ministry of Machinery Industry, or flanges meeting the standards of the Ministry of Chemical Industry, depending on the user’s requirements; it is also possible to combine flanges that adhere to different standards and have different connection interfaces. The pipe fittings for metal flexible hoses can include ball-and-nut fittings, internal cone fittings, tapered pipe thread fittings, clevis fittings, union fittings, claw-type quick connectors, open-type quick connectors, and splices; any combination of these can also be used as per the customer’s requirements. It is very flexible and convenient to use, with almost no restrictions.