管道的连接方式有哪些？What are the types of pipe connections?

1.法兰连接

法兰连接就是把两个管道、管件或器材，先各自固定在一个法兰盘上，然后在两个法兰盘之间加上法兰垫，最后用螺栓将两个法兰盘拉紧使其紧密结合起来的一种可拆卸的接头。

法兰连接的主要特点是拆卸方便、强度高、密封性能好。安装法兰时要求两个法兰保持平行，法兰的密封面不能碰伤，并且要清理干净。法兰垫片，要根据设计规定选用。

直径较大的管道常常会使用到法兰连接，法兰连接一般用在主干道连接阀门、止回阀、水表、水泵等处，以及需要经常拆卸、检修的管段上。

2.焊接

金属管道常常会用到焊接的方式连接。焊接是一种以加热、高温或者高压的方式接合金属的制造工艺及技术，通常有以下几种方式：

熔焊——加热欲接合工件使局部熔化形成熔池，必要时可加入熔填物辅助，熔池冷却凝固后便接合。

压焊——焊接过程必须对焊件施加压力。

钎焊——采用比母材熔点低的金属材料做钎料，利用液态钎料润湿母材，填充接头间隙，并与母材互相扩散实现链接焊件。

焊接适用于金属管道，多用于暗装管道和直径较大的管道。当管径小于22mm时宜采用承插或套管焊接，承口应迎介质流向安装，当管径大于或等于22mm时宜采用对口焊接。

焊接最大的问题是有造成腐蚀的风险，焊接口在长期使用情况下容易生锈。焊接质量对焊接技术依赖性比较大，管道连接质量难以稳定控制。

3.卡压式连接

卡压式连接常见于薄壁管道的链接。其采用径向收缩外力（液压钳）将管件卡紧在管子上，并通过O型密封圈止水，达到连接效果。类似原理还有环压式连接。

卡压式连接安装简便，但其对于冷水系统、直饮水系统的明装管道较为适用。因为当管内的密封圈老化时需要更换会比较麻烦。热水系统要尽量避免使用，因为密封圈和金属材料的热胀冷缩性质不一样，且密封圈经冷热循环更容易老化。因此暗装管道和热水系统一般不推荐使用这种连接方式的管道。

4.螺纹连接

螺纹连接采用将带有圆锥管螺纹内、外接口的两个连接件旋紧的方式连接，通过连接口螺纹的压力密封，达到连接效果。在传统的镀锌钢管中被广泛使用。

螺纹连接适用于管径小于或等于100mm的镀锌钢管，多用于明装管道。由于螺纹连接的丝扣常常会破坏镀锌层表面，极易造成管道的腐蚀。

5.承插连接

承插连接主要用于带承插接头的铸铁管、混凝土管、陶瓷管、塑料管等，有柔性连接和刚性连接两类。

刚性承插连接是用管道的插口插入管道的承口内，对位后先用嵌缝材料嵌缝，然后用密封材料密封，刚性连接采用石棉水泥或膨胀性填料密封，重要场合可用铅密封，使之成为一个牢固的封闭的整体。柔性承插连接接头在管道承插口的止封口上放入富有弹性的橡胶圈，然后施力将管子插端插入，形成一个能适应一定范围内的位移和振动的封闭管。

6.沟槽连接

沟槽式连接又称卡箍连接，可用于消防水、空调冷热水、给水、雨水等系统直径大于或等于100mm的镀锌钢管连接。具有操作简单、不影响管道的原有特性、施工安全、系统稳定性好，维修方便、省工省时等特点。

7.热熔粘接

热熔连接时PPR管道所采用的管道连接方式，它是使用加热的方式，使得PPR连接部位达到熔点产生融化，在使用承插的方式让管材和管件融合在一起。

热熔连接是一种可靠性强的永久连接，一旦完成热熔之后，几乎不会发生漏水事故。PPR管道正是因为这种可靠的连接，取得了广泛的应用。

8.电熔连接

电熔连接一般是熔接PE管所用到的一种连接方式。通过给嵌于管件内壁的铜丝通电加热，使熔合区部位塑料树脂发生相变，高分子链段在一定压力下互相渗透，交强，通过冷却材料重新结晶排列，使熔合部位结合成一个整体。

1.Flange connection

Flange connection is the two pipelines, pipe fittings or equipment, each fixed in a flange, and then between the two flanges plus flange gasket, and finally bolted to the two flanges tighten the two flanges to make it closely combined with a removable joint.

The main features of flange connection are easy disassembly, high strength and good sealing performance. When installing the flange, the two flanges should be kept parallel, and the sealing surface of the flange should not be bruised and cleaned up. Flange gasket, to be selected according to the design provisions.

Larger diameter pipeline often use to flange connection, flange connection is generally used in the main connection valve, check valve, water meter, water pumps, etc., as well as the need for frequent dismantling, maintenance of the pipe section.

2. Welding

Metal pipes are often connected by welding. Welding is a way to heat, high temperature or high pressure to join the metal manufacturing process and technology, usually the following ways:

Welding - heating the workpiece to be joined so that the local melting to form a molten pool, if necessary, can be added to the molten filler to assist, the molten pool after cooling and solidification will be joined.

Pressure welding - the welding process must apply pressure to the weldment.

Brazing - the use of lower melting point than the base material of the metal material as a brazing material, the use of liquid brazing material to wet the base material, fill the gap between the joints, and the base material and mutual diffusion to achieve the link weldment.

Welding is applicable to metal pipes, mostly used for concealed piping and larger diameter pipes. When the pipe diameter is less than 22mm suitable for socket or casing welding, socket should meet the medium flow direction installation, when the pipe diameter is greater than or equal to 22mm suitable for butt welding.

The biggest problem with welding is the risk of corrosion, and the welded joints are prone to rust under long-term use. Welding quality is more dependent on welding technology, and it is difficult to control the quality of pipe connection stably.

3. Pressure type connection

Pressure type connection is commonly used in thin-walled pipe links. The use of radial contraction of external forces (hydraulic clamp) will be fastened to the pipe fittings, and through the O-ring water stop, to achieve the effect of connection. Similar principle is also ring pressure type connection.

Pressure type connection is easy to install, but its cold water system, drinking water system is more suitable for open pipe. Because when the pipe sealing ring aging need to be replaced will be more trouble. Hot water system should try to avoid using, because the seal and the thermal expansion and contraction of the metal material is not the same nature, and the seal by the hot and cold cycle is more likely to aging. Therefore, the concealed piping and hot water system is generally not recommended to use this type of connection piping.

4. Threaded connection

Threaded connection with conical pipe threads inside and outside the interface of the two connectors screwed way to connect, through the connection port threads of the pressure sealing, to achieve the effect of connection. In the traditional galvanized steel pipe is widely used.

Threaded connections are suitable for galvanized steel pipes with a pipe diameter of less than or equal to 100mm, and are mostly used for open pipes. Because the threaded connection of the wire buckle will often damage the surface of the galvanized layer, it is very easy to cause corrosion of the pipeline.

5. Socket connection

Socket connection is mainly used for cast iron pipe with socket joints, concrete pipe, ceramic pipe, plastic pipe, etc., there are two types of flexible connection and rigid connection.

Rigid socket connection is inserted into the socket of the pipe, after the alignment of the socket material first embedded in the seam, and then sealed with sealing materials, rigid connection with asbestos cement or expansion filler sealing, important occasions can be used to seal the lead, so that it becomes a solid closed whole. Flexible socket connection joints in the pipe socket stop seal into the elastic rubber ring, and then apply force to insert the pipe plug end to form a closed pipe that can adapt to a certain range of displacement and vibration.

6. Groove connection

Groove connection, also known as clamp connection, can be used for fire water, air conditioning hot and cold water, water supply, rainwater and other systems with a diameter greater than or equal to 100mm galvanized steel pipe connection. With simple operation, does not affect the original characteristics of the pipe, construction safety, good system stability, easy maintenance, labor-saving and time-saving features.

7. Hot-melt bonding

Heat fusion connection when the PPR pipeline pipeline connection, it is the use of heating, so that the PPR connection parts to reach the melting point of melting, in the use of socket way to let the pipe and pipe fittings fused together.

Heat fusion connection is a reliable permanent connection, once the completion of the heat fusion, almost no water leakage accidents, PPR piping is precisely because of this reliable connection, has achieved a wide range of applications.

8. Electrofusion connection

Electrofusion connection is generally fused PE pipe used to a connection. Through the copper wire embedded in the inner wall of the pipe fittings electrically heated, so that the fusion area parts of the plastic resin phase change, polymer chain segments under a certain pressure to penetrate each other, cross-strength, through the cooling of the material to recrystallize the arrangement of the fusion part of the combination into a whole.