1. Classification of fire fighting pipes connection
With the development of the times, social public welfare undertakings develop rapidly. In order to ensure the stable development of the society, the people’s lives have been guaranteed, fire cause came into being. In recent years, the rapid development of the cause of fire protection, fire fighting pipeline connection also constantly updated development, some of the previous connection gradually exposed many shortcomings, gradually began to withdraw from the stage of history. There are four main ways of connection of fire-fighting pipe: clamp connection, thread connection, welding and flange connection.
1.1 thread connection Thread connection is a removable connection, because this connection has a simple structure, easy assembly and disassembly and other characteristics, so it has been widely used. Thread connection is also in the fire pipe connection in the use of the earliest connection.
Thread is mainly divided into: triangle thread, cylindrical pipe thread, hold thread. There are four basic types of threaded connections:
1.1.1 Bolt connection
Bolt connection, convenient assembly and disassembly. The common bolt connection, the bolt and the connection hole have certain clearance, because the processing is very simple, the cost is relatively low, so the application is very extensive. The reaming hole is connected by bolts, and the transition fit between the bolt rod and the connecting hole is adopted. Mainly used in some specific occasions, such as the need for bolts to bear a certain lateral load, or need to rely on the screw to accurately fix the relative position of the coupling.
1.1.2 Double-headed stud connection
This is a stud with threads on both ends. One end is rotated into and clamped into the threaded hole of the thicker coupling, and the other end is pushed through the through hole of a relatively thin coupling. This kind of connection is suitable for the situation where the jointed parts are very thick and require very compact structure but need to be disassembled and assembled frequently.
1.1.3 Screw joints
The screw connection is very simple compared to the previous ones. The screw is directly transferred into the threaded hole of the connecting part. The utility model is suitable for a device with a thick coupling part at one end and a nut can not be installed at the other end. But the shortcomings of this connection is also very obvious, if often disassembled, it will cause serious wear thread hole, shorten its life.
1.1.4 Set screw coupling
This set screw connection is often used to fix the relative position of the two parts. This is done by screwing a tight screw into the threaded hole of one of the parts and pushing the end against the surface of another part or into a pre-set pit.
1.2 Welding and welding flanges
Welding technology is produced with the use of copper, iron and other metals and various heat sources. Welding has a long history, even today, welding is still in various industrial production has a wide range of applications. When the diameter of the pipe is greater than DN150, welded steel pipe can be used. Now welding technology in the fire fighting pipeline connection is mainly used with the welding flange to use.
Welding flanges can be classified as: flat welding flange, welding flange and screw flange according to their different connection forms. Selection of the flange must be selected in line with the need for welding steel pipe flange, only the same standard flange corresponding to its need to be welded pipe fittings, to weld the perfect effect.
If hot dip galvanized steel pipe needs to use some flange connection, then should choose to use threaded flange. In addition, the system can be directly welded if the inner wall of the pipeline is not anticorrosive. When using the internal and external wall hot-dip galvanized steel pipe fire protection, should not be welded to connect.
When welding pipes, attention must be paid to the following problems. When welding pipe hole should try to avoid in the weld, welding cracks must be cleaned up, in particular, there can be no oil, and can not have cracks, layers and other defects. Also to avoid forced group of welding, welding need to protect the welding area from external adverse weather factors, such as not to take wind, rain, snow, cold “four prevention” measures. Welding environment is also very important, the wind speed, humidity have certain special requirements. It is strictly prohibited to strike an arc on the surface of the welded pipe or test current or to weld some temporary supports at random. When welding, should pay special attention to the problem is the arc, the arc of the quality to pass, multi-layer welding should be staggered between the level of joints.
1.3 Clamp connection
Clamp connection is also called grooved pipe connection technology. At present, it has become the preferred technology of pipeline connection for conveying liquids and gases. The domestic research and development of this technology do not foreign relatively late, from 1998 began to develop clamps technology to now, only a short period of ten years. But because of its simple, fast, convenient features, technology is very advanced, so soon by the domestic market recognition, and has been widely promoted. Up to now, the clamp technology has gradually replaced the flange and welding of these two more traditional pipe connection. Nowadays, the clamp technology is not only more mature in technology, but also because of its long-term, stable and reliable characteristics, it has been actively guided by national laws and regulations, and has a high credit in the market.
The clamp is a simple and convenient piping method, which is mainly connected by groove type and hole type, and is completed successfully with various accessories. Its main components are clamps, washers, fasteners three. Clamp connection can be divided into three types, one is a rigid joint, a flexible joint, there is a hole type joint. The clamp connection ensures the connection according to the requirements, the pipe can move in the axial small range, so that it can absorb part of the noise and vibration, and has the effect of noise reduction. Moreover, the clamp-type connection is tightly sealed on the opening of the pipeline, and is very suitable for the installation and use of the fire-fighting spraying pipeline in the construction industry.
In the clamps connection, it should be noted that the national technical standards are relatively backward, easy to increase the construction and supervision difficulties. At the same time, the width and depth of the groove affect the quality of the clamp connection, so in the construction of pipe openings and pipe grooves should be strictly implemented in accordance with the specifications to ensure the groove quality. The protection of zinc coating should be paid more attention to in the grooves of galvanized pipe. In addition, the inner clamp connection has a certain flexibility, sometimes due to the pipeline pressure test process caused serious displacement deformation or even interface off, so it should be added in the design and construction of fixed bracket to ensure safety.
2. Comparison and Analysis of 2 Fire Fighting Pipes Connection Ways
2.1 Advantages and disadvantages of thread connection
In the early days of pipe connection technology, thread connection technology was a highly regarded connection method. This is only for the fire industry has not developed enough to meet the requirements of the period. Overall. The thread connection is simple, easy to use, has a certain reliability, in a small range can still be used. But with the rapid development of the times, the screw thread has been unable to meet the requirements of large-scale projects, because of its use time, load capacity and so on.
2.2 Welding and welding flange advantages and disadvantages analysis
Welding and welding flanges are excellent connections for fire hose connections after screw connections, It has the advantages of safety, reliability, firmness and relatively long service time. Although it can guarantee relatively good project quality, the cost is relatively high and the time limit is very long. With the passage of time, more and more problems are exposed. For example, in the process of welding, high temperature destroyed the galvanized layer next to the fire channel pipe interface, resulting in serious electrochemical corrosion, reducing the life of the whole fire control system. The iron oxide produced by the inner wall of the pipe is easy to block the pipe and nozzle after falling off, which affects the normal operation of the whole system and seriously pollutes the water inside the pipe. In addition, welding and flange connection need welding workers for a long time in high altitude high intensity work, operation is difficult, it is easy to produce safety accidents. With the appearance of the clamp connection, and because of the high risk of welding, the national fire design code and national standard have not allowed the use of welding and flange welding in many projects.
2.3 Analysis of the advantages and disadvantages of clamp connection
In the mid-1990s, some of the more developed cities in China have hundreds of buildings, especially large and important building, began to use the clamp (groove) connector. In contrast to the clamp connection in foreign countries have more than 70 years of production history and application experience, in my clamp connection application time is relatively short. At present, clamp-type connectors are widely used in water supply system, fire control system, air conditioning system and so on. Compared to the traditional connection methods such as thread connection and welding, the advantages of the clamp connection are more obvious: the main advantage is that the installation is very simple, The installation period is short, the safety is high, and the service life can reach more than 30 years, while the clamp connection is convenient in the management and maintenance. The sealing rubber ring of the clamp type connection has the advantage of corrosion resistance, aging resistance and isolation performance.
3. Clamp connection is the best way to connect fire fighting pipes
With the passage of time and the improvement of application requirements, screw connection and welding, flange welding exposed more and more problems, due to aging problems often lead to engineering accidents. The appearance of the clamp connection has greatly improved the system stability, and solved many problems that cannot be solved by the previous connection methods. In the use of fire pipe, the clamp connection has become the mainstream today, the popularity of more and more high.
Why is the clamps connection the best way to connect fire fighting pipes? The main reason is that the clamp connection avoids the welding and the second galvanizing, solves the big specification pipeline thread connection difficulty; Good tightness of the clamp connection; The clamp connection greatly reduces the construction period and saves time. This is in the fire is an accident rescue and other aspects of play a particularly obvious role.
In summary, the clamp connection is the best way to connect the fire fighting pipeline and even many engineering pipeline.