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What is a metal hose connection?

author:Omega hose | Release time:2018-08-31
A: What is a metal hose connection? What is stainless steel hose and what is stainless steel flexible hose? Metal flexible connector is also called metal soft hose, stainless steel hose, stainless steel hose, metal flexible joint has superior flexibility, temperature resistance, pressure resistance, corrosion resistance, suitable for steam, water, oil and various industrial gases, drugs and media.


The difference between rubber hose and metal hose


1、 Rubber hose ball is composed of inner rubber layer, reinforcing layer, multi-layer scraping cotton cord fabric and outer rubber layer. According to different media, different rubber materials are used, including natural rubber, styrene butadiene rubber, butyl rubber, nitrile rubber, ethylene propylene diene monomer, chloroprene rubber, silicone rubber, fluorine rubber, etc. It has the functions of heat resistance, acid resistance, alkali resistance, corrosion resistance, wear resistance and oil resistance.


The application limitation of rubber hose: because the flexible rubber joint has superior comprehensive function, it should be used for the lifting and transportation of raw water and sewage, the water supply and cooling circulating water of thermal power plant, the pipeline transportation of chemical substances in metallurgical industry, condensate water and chemical industry, the cooling and dilution of petrochemical industry and the flexible connection between long and short interval pipelines in other industries. Due to its high wear resistance, rubber is also suitable for all industries of granular and powdery and low-temperature gas delivery.


2、 Flexible metal hose plays an important role in the activities, thermal expansion and vibration reception of the pipeline system.


The type, length and connection method of metal hose can be according to user's requirements.


Soft metal joint for pump;


In the project, the pumps and tightening machines and other equipment will produce vibration and noise under the task mode, which will endanger the engineering quality and human health.


The metal soft joint has superior vibration isolation and noise reduction effect. The metal soft joint of certain length is installed at the inlet and outlet of pump and tightening machine, which can reduce vibration and noise, improve engineering quality and service life.


Metal flexible hose and rubber flexible hose have their own uses, correctly distinguish their differences, reasonable application of them, make the equipment play a greater role.


Since the German Weizmann invented and produced a flexible metal joint in the world in 1885, after more than 100 years of development, the metal flexible joint has become an indispensable component in modern pipeline system with its reliable sealing, pressure resistance, high and low temperature resistance, corrosion resistance and flexibility and many other properties.


The metal soft joint can be used in the piping system of chemical industry, superheated steam pipe, low temperature pipeline, high pressure pipeline of hydraulic and pneumatic equipment, and pipeline transmitting toxic and explosive medium. Its function is to absorb reciprocating motion, absorb thermal expansion, absorb vibration and compensate the deviation of pipeline installation. It is because of the use of metal flexible joint, the complex pipeline system becomes simple, and the impossible pipeline system becomes possible. The application of metal flexible joint has covered many different fields of industry and household. It is no exaggeration to say that as long as there is pipeline, the metal flexible joint can be used. However, in the practical application of metal flexible joint, it must be selected according to its own points and rules. If these rules are violated, the metal flexible joint will not play its due role, but will affect the operation of the whole pipeline system and even cause serious events, thus causing unnecessary property and personnel losses.


Therefore, it is necessary to understand the basic knowledge of the soft metal joint and grasp the usage law of the soft metal joint before selecting the flexible metal joint, so that it can be used in engineering practice flexibly.


The metal flexible joint is mainly composed of three parts: bellows, steel wire mesh sleeve and joint. Corrugated pipe is the main body of metal flexible joint, which plays the role of bending. The steel mesh sleeve plays the role of pressure bearing and protection, and the joint plays the role of connection. Through the different combination of these three parts, various types of metal soft joints are formed, which play their respective roles in the pipeline system.

1. bellows


Bellows is a cylindrical thin-walled shell with transverse ripple, which can be extended or shortened under axial tension or pressure. If a transverse force is applied to it to produce bending moment, corresponding displacement can be obtained along the axial plane.


Corrugated pipe is a thin-walled pipe welded by seamless or longitudinal joint, which is formed by mechanical rolling or hydraulic expansion. The whole process shall be a continuous process. According to its shape, corrugated pipe can be divided into spiral or ring corrugated. Spiral bellows is that the corrugated pipe is made of continuous spiral with constant pitch according to the right-hand thread. The circular corrugated pipe is composed of many single corrugated with equal spacing.


The performance of bellows depends on the geometric parameters of the bellows. When the two bellows are of the same type and the other geometric parameters are the same except for the different wave heights, the pressure bearing capacity of the bellows with a larger wave height is smaller and the flexibility is better. When the two bellows are of the same type and the difference in the distance of wave and other geometric parameters are the same, the pressure of the bellows with a larger wave distance is less flexible. When the wave distance is different, the pressure of the bellows with a larger wave distance is less flexible. When the wave height is different, the pressure of the bellows with the larger wave distance The two bellows are of the same type and have the same geometric parameters except for the different wall thickness. The corrugated pipes with a slightly larger wall thickness have larger pressure bearing capacity and poor flexibility. Compared with the circular bellows, the spiral bellows have high pressure bearing capacity, greater rigidity and poor flexibility. )


Corrugated materials are generally austenitic stainless steel, which has the following. Point 1) can withstand the corrosion of internal and external environment, 2) can work for a long time under medium temperature and environmental temperature, 3) have good processing technology (mainly refers to weldability and formability), 4) the procurement channel is smooth. If other materials are to be selected, these four points must be considered


2. wire mesh sleeve


The steel wire mesh sleeve is made of several strands of metal wires or ingot metal belts crossed with each other in a certain order and at a specified angle. The mesh is set on the outer surface of the metal bellows. The steel wire mesh sleeve not only shares the static load of the metal soft joint in the axial and radial direction, but also ensures the safe and reliable operation of the metal soft joint under the condition of pressure generated by the flow of the fluid along the pipeline, and at the same time, it can also guarantee the safe and reliable operation of the metal soft joint The corrugated part of the hose is not directly damaged by relative friction, impact and other aspects. Therefore, corrugated metal soft joints can be made of single layer, double layer or three layer steel wire mesh sleeve according to the different service conditions. The material of wire mesh sleeve is generally the same as that of corrugated pipe, and can be made of different materials, which mainly considers corrosion protection and economy.


3. joint


The joint is a part connecting the metal soft joint with other pipe fittings and equipment. It ensures the normal operation of the medium in the pipeline system. The joint can be divided into four categories: screw connection, flange connection, quick insertion connection and welding connection.


A.


Thread connection: the metal soft joints with screw connection joints are mostly under the diameter of Ф 50mm. The sealing forms mainly include ball head seal, conical seal, tenon groove seal, flat gasket seal and thread seal. In order to ensure the correct installation and convenient disassembly of metal soft joint, at least one end thread shall be thread of flexible sleeve, and the standard can be metric or English.


B.


Flange connection: the diameter of metal soft joint with flange joint can be over Ф 15mm. The sealing forms include convex face seal, concave convex face seal, tenon groove seal and ring seal, etc. the sealing shall be kept with bolts and tight flange. In order to ensure the correct installation of metal soft joint, at least one end shall be loose sleeve flange, and flange can have many standards.


C.


Quick insertion connection: the diameter of metal soft joint with quick insertion joint is generally less than Ф 100mm. The quick insertion joint can be divided into three types: plug-in type, portable type and claw type. It is mainly applicable to occasions requiring frequent disassembly, and the "O" ring seal is used for sealing.


Welding connection: welded connection refers to the welding of metal soft joint with the required connecting pipe or equipment with straight pipe as the joint, which is generally one-time installation, without disassembly. )


The joint material can be carbon steel, stainless steel or non-ferrous metal, mainly considering its strength, corrosion resistance, weldability, and economic and material source channels and the needs of users. 8 d)


Sh/t 3412-1999 "selection, inspection and acceptance of metal soft joints for petrochemical pipeline" to calculate


Advantages and applications of metal soft joint


The metal soft joint has the advantages of compact structure, firm connection, etc. It has three-dimensional compensation function. In the pipe system, it is an effective component which can compensate temperature, eliminate mechanical displacement, absorb vibration and reduce noise. The application of metal soft joint in petrochemical plant design greatly improves the internal quality of engineering design.


2. Purpose and principle of setting up metal soft joint


2.1 purpose of setting metal soft joint


The main purpose of the metal soft joint in engineering is to compensate the relationship, eliminate mechanical displacement, absorb vibration, reduce noise and move flexibly, which can change the direction of fluid movement conveniently.


2.2 the principle of setting metal soft joint and the metal soft joint in petrochemical plant are as follows:


2.2.1 large petrochemical products and raw material storage tanks:


The metal soft joint is set on the inlet and outlet pipes of large storage tanks, which can prevent the pipeline damage caused by foundation settlement,  and the omission of stored items; avoid property loss and environmental pollution. When constructing large storage tanks in the  multiple generating area, the installation of metal soft joints should be paid more attention.

2.2.2 import and export of large machines and pumps: the pumps, compressors, centrifuges and other equipment used in the project will produce vibration and noise under working conditions, which will endanger the project quality and personal health. In particular, large pumps and centrifuges should be installed with a certain length of metal soft joints at their inlet and outlet, which can reduce vibration and noise, improve the engineering quality and prolong the service life of pumps, and bring certain convenience to the installation of pumps.


2.2.3 tank cars and oil tankers: at present, metal flexible joints are widely used for crane tubes used for loading and unloading trains, tank cars and oil tankers. The use of metal soft joint not only can achieve airtight loading and unloading, reduce oil volatilization, but also can be installed and disassembled easily, which brings a lot of convenience for operation.


2.2.4 electronic weighing equipment: batching is often encountered in chemical plant, especially in polymerization unit. Accurate proportioning depends on accurate measurement. The batching tank to be weighed is not allowed to bear axial force after installation, and all pipelines connected with it need to be connected with flexible metal joints to eliminate the influence of piping system on weighing accuracy


It is necessary to remove the equipment frequently


This kind of equipment, such as filter, filling equipment, mobile pump or compressor, and fixed equipment or pipe connection, good use of metal soft joint connection.


2.2.6 others


The pipeline crossing the expansion joint of the building should be connected with flexible metal joint to compensate for the different settlement of walls on both sides. In the case of insufficient piping space and high operating temperature, a metal soft joint is added to the equipment nozzle to absorb the expansion of the piping system and eliminate the thrust of the piping system on the equipment nozzle. In addition, the metal flexible joint is stable at low temperature and has good flexibility, which is widely used in low temperature pipeline. Because of its good airtightness, it can be used in high vacuum system.


Composition and classification of flexible metal joints


The metal soft joint is composed of pipe body, net sleeve and connector. The pipe body and mesh sleeve are made of stainless steel, and the connectors are divided into stainless steel and carbon steel according to the process requirements. According to the connection form, it can be divided into flange connection and pipe joint connection. The flange of metal soft joint can be installed with international flange, standard flange of Ministry of mechanical industry, standard flange of Ministry of chemical industry, etc. according to different requirements of users, flange combination of different standards and connection interface can also be carried out. The pipe joints of metal soft joint can be ball head outer nut, inner cone joint, taper pipe thread joint, groove joint, union joint, claw type quick joint, open type quick connector, connecting pipe, etc., and can be combined arbitrarily according to the requirements of users. It is very flexible and convenient to use, almost without any control.


Regulations in the code "selection standard for flexible metal joints and corrugated compensators for seismic storage tanks"


B: The flexible metal joint and flexible rubber joint are the same as our shower nozzle hose. They are used for absorbing displacement and multi-directional connection. They are mainly used for tank farm, tank and pump connection (to prevent tank foundation from sinking and damaging connecting pipe), tank car in and out connection, utility station connection, etc. Metal bellows, metal bellows compensator (both the same) and sliding expansion joint allow large displacement relative to metal soft joint, which are commonly used for thermal stress compensation of pipeline. It is commonly used in high temperature steam pipeline, and it should be used with caution for flammable and explosive pipeline.


The above is for discussion.


C: The metal flexible joint is a metal bellows, which has its own sealing property.


Generally, the outer wall is covered with metal mesh, and the inner is corrugated hose!


D: Metal bellows and metal flexible joints are widely used. It is not clear in a few words that there are metal bellows in the metal flexible joints. Therefore, we provide metal flexible joints for customers who need metal flexible joints, metal bellows for metal bellows and compensators for compensators. All according to customer needs to help solve the problem, can also provide the pipeline compensator design and so on. We can provide peer-to-peer consultation.


E: From the table below, we can see that among all the performance indexes, the bellows is better than the metal flexible joint in terms of air tightness.


Among all the performance indexes of flexible metal joint and bellows compensator, the air tightness is better than that of flexible metal joint. Because the bellows is made of integral material, the metal flexible joint is a flexible component made of stainless steel tape, so it is inevitable to have a slight air leakage problem. However, with the continuous progress of metal soft joint technology, its air tightness will be higher and higher.


How to connect


Both ends of the flange is the current domestic traditional connection mode, in addition to the following several ways.


1. V-clamp connection. This connection is used when the hose is long and needs to be supported in the middle of the hose.


2. Double clamp connection, this connection has many forms. The advantages of this method are that the flange, joint and welding process are omitted, and the installation is convenient, but the requirements for the connection and cooperation of the rigid pipe and the installation operation are higher.


3. Corner connection.


4. One end clamp and one end welding.


F: Please clarify the concept:


1. Bellows are flexible parts of metal flexible joints and expansion joints


2. Expansion joint refers to various devices containing one or more bellows to absorb the size changes of pipeline or container caused by thermal expansion and cold contraction.

3. The compensator is the expansion joint. The compensator was translated from the old brother of the Soviet Union. Later, the standard of EJMA expansion joint manufacturers association was gradually adopted in China. GB 12777 began to be called expansion joint. However, some manufacturers or data are still called compensators, which is one thing.


G: Can you talk about the respective uses, advantages and disadvantages of bellows, expansion joints and compensators?


Compensators and expansion joints are not the same. In fact, they are the same. The rigidity is better, and the flexibility of metal soft joints is better. In my space, there is a compensator. Expansion joint, the use of metal soft joint and other specific information.

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