Advantages and disadvantages of various valve connection methods.
In industrial pipeline systems and various civil pipeline facilities, valves play a vital role. They can control the flow, pressure and flow direction of fluids. The choice of valve connection method is directly related to the performance, reliability, installation convenience and subsequent maintenance cost of the entire pipeline system. The appropriate connection method can ensure the close fit between the valve and the pipeline, so that the system can operate stably and avoid safety hazards such as leakage;
On the contrary, if the connection method is not selected properly, it may lead to frequent failures, maintenance difficulties and high costs. Therefore, in-depth understanding of valve connection methods and making wise choices are extremely critical to the successful implementation of pipeline projects.
1. Threaded valve
Threaded connection is a common valve connection method, which usually processes the inlet and outlet ends of the valve into tapered pipes or straight pipe threads. This connection method is generally suitable for valves with a nominal diameter of less than 50mm.
Advantages:
Easy installation:
Its structure is relatively simple, and the installation process does not require complex tools and professional techniques. Ordinary workers can operate it after simple training, which can greatly shorten the installation time and improve the progress of the project. For example, in the installation of some small household plumbing systems, if threaded valves are used, installers can quickly connect the valves to the pipes, reducing the construction period.
Economical:
Since the process of threaded connection is relatively simple, the manufacturing cost of the valve itself and the cost of the matching pipe connection components are relatively low. It is an economical choice for some small projects with limited budgets or local small-diameter pipe connections in large-scale projects that are more sensitive to cost.
Flexibility:
In some occasions where valves need to be replaced or adjusted frequently, threaded connection is easy to disassemble and reinstall, and can quickly meet the needs of system changes. For example, in some small fluid test devices in laboratories, valves may be frequently replaced according to different experimental requirements, and threaded connections can well meet the needs of such flexibility.
Disadvantages:
Sealing limitations:
When the diameter of the valve is too large, the sealing performance of the threaded connection will decrease significantly, and it is difficult to ensure complete leakage. Because as the diameter increases, the processing accuracy of the thread and the difficulty of processing the sealing surface will increase, even if sealing materials are used for auxiliary sealing, it is difficult to achieve the ideal effect. For example, in some large industrial water supply pipelines, if large-diameter valves with threaded connections are used, serious water leakage may occur, affecting the normal operation of the system.
Leakage hazards:
During long-term use, threaded connections may loosen threads due to factors such as pipeline vibration, temperature changes, and fluid impact, resulting in leakage channels. Once a leak occurs, it will not only cause waste of fluid, but also damage the surrounding environment and equipment, increase maintenance costs and downtime. For example, in the pipeline system of a chemical production workshop, if a threaded valve leaks, it may cause chemical leakage, causing safety accidents and environmental pollution.
2. Flange-connected valves
Flange connection is a way to connect the valve to the pipeline system through a pair of flanges and bolts.
Advantages:
Convenience of installation and disassembly:
The structural design of the flange connection makes the installation and disassembly process of the valve relatively simple. Just align the flange with the flange of the pipeline, insert the bolts and tighten the nuts to complete the installation; when disassembly is required, just reverse the operation. This convenience is particularly important in the maintenance and overhaul of large-scale pipeline systems. For example, in a large pump station of an urban water supply system, if a valve needs to be repaired or replaced, the flange connection can quickly separate the valve from the pipeline system, reducing the impact time on the entire water supply system.
Strong versatility:
Flange connection is suitable for pipeline systems of various diameters and pressure levels. Whether it is a small-diameter low-pressure pipeline or a large-diameter high-pressure pipeline, flanges and valves of corresponding specifications can be found for matching connection. This makes flange connection widely used in the industrial field. For example, in the complex pipeline network of petrochemical, electric power, metallurgy and other industries, valves of different specifications and pressure requirements can be integrated into the system through flange connection.
High stability:
Flange connection can provide relatively stable connection performance during normal operation and can withstand large external forces and vibrations. In some occasions with large mechanical vibration or strong fluid impact, such as the steam pipeline system of an industrial boiler room, flange-connected valves can maintain a good connection state and reduce the risk of failure caused by loose connections.
Disadvantages:
Weight and space requirements: Due to the presence of flanges and bolts, flange-connected valves are relatively bulky and require more installation space. In some pipeline layouts with limited space, it may bring certain difficulties to design and installation. For example, in the engine room of a ship, the pipeline system is dense and the space is small. Too many flange-connected valves may cause crowded layout, increase the difficulty and cost of pipeline installation.
High cost:
The manufacturing cost of flange-connected valves themselves is high, because the processing and manufacturing of flanges require certain process and material costs. At the same time, matching bolts, nuts, and sealing gaskets and other components also increase the overall cost. Moreover, during the installation process, the installation cost will also increase due to the need for more manpower and time to tighten the bolts. For example, in the pipeline installation of large chemical projects, the procurement and installation costs of flange-connected valves account for a considerable proportion of the cost of the entire pipeline system.
High temperature sealing problem:
In high temperature environments, the sealing performance of flange connections may be affected. Due to the different thermal expansion coefficients of metal materials, as the temperature rises, the tightening force between the flange and the bolts may change, resulting in a decrease in the sealing effect of the sealing gasket, resulting in leakage. For example, in the high-temperature steam pipeline system of a thermal power plant, special high-temperature sealing gaskets and strict bolt preload control measures are required to ensure the sealing reliability of flange-connected valves at high temperatures.
3. Welded connection valves
Welding connection is a connection method in which the valve is directly welded to the pipeline.
Advantages:
High strength and sealing:
Welding connection can make the valve and the pipeline form a whole, with extremely high connection strength and sealing performance. This connection method can effectively withstand fluid pressure and temperature changes under high pressure and high temperature environments, and there is almost no risk of leakage.
In some occasions with extremely high requirements for safety and reliability, such as the cooling pipeline system of nuclear energy projects and the high-pressure natural gas transmission pipeline system, welded valves are the first choice. For example, in a high-pressure natural gas long-distance pipeline, welded valves can ensure the stable transmission of natural gas under high pressure and avoid serious safety accidents such as explosions caused by leakage.
Suitable for extreme working conditions:
Whether it is a pipeline system with high temperature, high pressure, low temperature or corrosive media, welding connections are competent. On the feed and discharge pipes of some high-temperature and high-pressure reactors in the petrochemical industry, the valves connected by welding can operate stably for a long time in harsh chemical environments and high-temperature and high-pressure conditions, ensuring the continuity and safety of the production process.
Beauty and compactness:
The appearance of the pipeline system connected by welding is simple and beautiful, without the exposed bolts and nuts like flange connections, which reduces the space occupation of the pipeline system and makes the entire pipeline layout more compact. In some occasions with high requirements for space utilization, such as the fire protection pipeline system of high-rise buildings and the ventilation pipeline system of underground parking lots, the valves connected by welding help optimize the pipeline design and space layout.
Disadvantages:
Non-removability:
Once the welding connection is completed, the valve and the pipeline form a fixed whole, which is difficult to disassemble. If the valve fails during operation and needs to be replaced, it is often necessary to cut the pipeline, which not only increases the maintenance cost and time, but also may cause damage to the surrounding pipelines and equipment.
For example, in a large industrial pipeline system, if a welded valve is damaged, it may be necessary to stop production and carry out large-scale pipeline cutting and re-welding work, resulting in huge economic losses.
High welding process requirements:
Welding connections require professional welding technicians and equipment, and strict control of welding process parameters. If the welding quality is not up to standard, welding defects such as pores, slag inclusions, and incomplete penetration may occur, which will affect the connection strength and sealing performance of the valve and the pipeline.
In some large-scale engineering projects, in order to ensure the welding quality, strict quality inspection and control of the welding process are required, which increases the difficulty and cost of engineering management.
Difficulty in maintenance and transformation:
Due to the non-detachable nature of the welded connection, the welded valve will become an obstacle when the pipeline system needs to be transformed or upgraded. For example, when the factory expands the production line or technical transformation, if the original welded valve position is unreasonable, it is very difficult to adjust or replace the valve, and the entire pipeline system may need to be redesigned and transformed.
4. Wafer connection valve
The wafer connection is a connection method that clamps the valve between two pipe flanges by bolts.
Advantages:
Compact structure:
The structure of the wafer connection valve is relatively simple, without complex connection parts, and the overall compactness can be installed in a limited space. In some narrow space pipeline systems, such as air conditioning and ventilation duct systems in buildings or cooling duct systems of small industrial equipment, the wafer connection valve can save valuable space and facilitate pipeline layout and equipment installation.
Ease of installation:
When installing a wafer-connected valve, simply place the valve between two pipe flanges, align the bolt holes, insert the bolts and tighten the nuts. This installation method does not require precise welding or processing of the flanges as with flange connections, which greatly shortens the installation time. For example, in the installation of water supply and drainage pipeline systems in some small commercial buildings, if a wafer-connected valve is used, the valve installation work can be completed quickly, improving construction efficiency.
Cost-effectiveness:
The manufacturing cost of the wafer-connected valve is relatively low because of its simple structure and the relatively few materials and processing techniques required. At the same time, due to its easy installation, it also reduces the labor cost and time cost during the installation process. In some small projects with strict cost control or auxiliary pipeline systems in large-scale projects, the wafer-connected valve is a very cost-effective choice.
Disadvantages:
High alignment requirements:
The wafer-connected valve requires precise alignment during installation. If the alignment between the valve and the pipeline flange is inaccurate, it may cause poor sealing and leakage. In the actual installation process, due to factors such as pipeline processing errors and installation site conditions, it may be difficult to achieve precise centering, and the installer needs to have a high level of technical skills and experience.
For example, in some industrial pipeline system renovation projects, due to the deformation or deviation of the original pipeline, it may be difficult to center the clamp-connected valve, increasing the installation risk.
Applicable diameter restrictions:
Clamp-connected valves are generally suitable for small and medium-sized pipeline systems. For large-diameter pipelines, the stability and reliability of the clamp connection will be affected due to the large size and weight of the valve. In large-diameter water supply and drainage pipeline projects, large-diameter valves usually do not use clamp connections, but choose flange connections or welding connections to ensure the safe and stable operation of the pipeline system.
Sealing durability:
The sealing of the clamp connection mainly relies on the sealing gasket between the valve and the flange. During long-term operation, due to factors such as fluid scouring and temperature changes, the sealing gasket may age and deform, resulting in a decrease in sealing performance. The sealing gasket needs to be checked and replaced regularly, which increases maintenance costs and workload. For example, in some hot water supply pipeline systems, the sealing gasket of the clamp-connected valve may age rapidly due to long-term heat exposure and need to be replaced frequently.
5. Clamp-connected valves
Clamp connection is a method of quickly connecting the valve to the pipeline through a metal ring or plastic clamp.
Advantages:
Quick installation:
Clamp connection is the fastest installation method among all valve connection methods. Simply insert the connecting part of the valve and the pipeline into the clamp, and then tighten the bolts or nuts on the clamp to complete the connection. This quick installation feature makes the clamp connection have obvious advantages in some emergency repairs or temporary pipeline systems. For example, after natural disasters such as earthquakes and floods, the rapid construction of temporary water supply and power supply pipeline systems can use clamp connection valves to quickly restore basic life support facilities.
Strong adaptability:
Clamp connection is suitable for pipes of various materials, whether metal pipes or non-metallic pipes, such as steel pipes, copper pipes, plastic pipes, etc., can be connected to valves using clamp connection. At the same time, clamp connection is also suitable for pipes of different shapes, such as circular pipes, rectangular pipes, etc.
In some complex piping systems, there may be pipes of various materials and shapes at the same time. Clamp connections can easily connect valves to these pipes. For example, in building decoration projects, metal water pipes, plastic drain pipes, and rectangular ventilation pipes may be connected to valves. Clamp connections can meet such diverse needs well.
Adjustability:
The clamp connection has a certain degree of adjustability and can adapt to the axial displacement and angular deviation of the pipe within a certain range. When the pipe is deformed due to thermal expansion and contraction or foundation settlement, the clamp connection can automatically adjust to maintain the sealing of the connection. In some long-distance outdoor piping systems, due to the large changes in ambient temperature, the pipe is prone to thermal expansion and contraction. The clamp connection valve can effectively deal with this situation and reduce the risk of leakage caused by pipe deformation.
Disadvantages:
Limited connection strength:
Compared with welding connection and flange connection, the strength of the clamp connection is relatively low. In high-pressure and high-stress piping systems, the clamp connection may not meet the strength requirements, and the clamp is prone to loosening and breaking, leading to leakage accidents.
For example, in high-pressure steam pipeline systems or large industrial pressure pipeline systems, clamp connection valves are generally not used, but more reliable welding connections or flange connections are selected.
The sealing performance is relatively weak:
the sealing of the clamp connection mainly relies on the friction between the clamp and the pipeline and the role of the sealing gasket. In the long-term operation process, especially under high pressure, high temperature or corrosive fluid media, the sealing performance may gradually decrease.
It is necessary to check and maintain the sealing status regularly, and replace the sealing gasket or clamp when necessary. For example, in some corrosive liquid transportation pipeline systems in chemical production, the sealing parts of the clamp connection valve may fail due to corrosion and need to be frequently maintained and replaced.
Limitation of scope of application:
Although the clamp connection has certain adaptability, the reliability and durability of the clamp connection are difficult to guarantee in some extreme working conditions, such as ultra-high pressure, extremely low temperature or pipeline systems with highly corrosive media. In pipeline systems in special fields such as nuclear power engineering and deep-sea oil extraction, clamp connection valves are rarely used, but more professional and reliable connection methods are used.
6. Internal self-tightening connection valve
Internal self-tightening connection is a way of self-tightening connection using medium pressure.
Advantages:
High-pressure adaptability:
Internal self-tightening connection valves are particularly suitable for high-pressure pipeline systems. Under high-pressure conditions, the medium pressure will act on the sealing structure of the valve, causing it to automatically tighten, thereby improving the sealing performance. This self-tightening characteristic gives internal self-tightening connection valves unique advantages in the field of high-pressure fluid transportation, such as high-pressure hydrogenation units in the petrochemical industry, high-pressure natural gas storage and transportation systems, etc. It is widely used.
For example, in the pipeline system of a high-pressure natural gas compressor station, the internal self-tightening connection valve can operate stably under pressures of up to hundreds of atmospheres to ensure the safe transportation of natural gas.
Save materials and manpower:
Since the internal self-tightening connection uses medium pressure to achieve sealing, it does not require a large number of fastening parts such as bolts and nuts like flange connections, nor does it require complex welding processes like welding connections. Therefore, a large amount of metal materials and labor costs can be saved. In the construction of large-scale high-pressure pipeline projects, the use of internal self-tightening valves can effectively reduce project costs and construction difficulties.
For example, in the construction of high-pressure pipeline systems in large oil refineries, the use of internal self-tightening valves can reduce a large amount of flange and bolt procurement, installation and subsequent maintenance costs.
Good sealing reliability:
The sealing performance of the internal self-tightening connection increases with the increase of medium pressure, and it can maintain a good sealing state during normal operation. Even in the case of large pressure fluctuations, it can effectively prevent leakage. In some pipeline systems with extremely high sealing requirements and unstable pressure, such as high-pressure reaction pipeline systems in chemical production, internal self-tightening valves can provide reliable sealing guarantees to avoid safety accidents and production interruptions caused by leakage.
Disadvantages:
Pre-tightening force requirements:
When installing the internal self-tightening valve, a certain pre-tightening force needs to be applied to ensure the initial sealing. If the pre-tightening force is insufficient, leakage may occur at the initial start-up of the system; if the pre-tightening force is too large, the sealing structure of the valve may be damaged or the valve may be difficult to open. In the actual installation process, the pre-tightening force needs to be accurately calculated and controlled, which requires a high level of technical level and experience of the installer.
For example, when installing an internal self-tightening valve in a high-pressure steam pipeline system, if the pre-tightening force is not properly controlled, the valve may fail during operation, affecting the normal operation of the entire steam supply system.
Structural complexity:
The structure of the internal self-tightening valve is relatively complex, and it is difficult to design and manufacture. Its internal self-tightening sealing mechanism needs to be precisely designed and processed to ensure that it can work normally under various pressure and temperature conditions. This makes the manufacturing cost of the internal self-tightening valve relatively high, and professional technicians and equipment are also required for repair and maintenance. For example, the internal self-tightening valve used in some high-end industrial fields needs to be repaired by technicians from professional manufacturers once a failure occurs, and the repair cycle is long and the cost is high.
Applicable medium restrictions: The internal self-tightening valve is not suitable for all media. For some media containing solid particles, high viscosity or strong corrosiveness, it may affect the self-tightening sealing performance of the valve and even damage the sealing structure. In chemical production, if the medium contains a large amount of solid impurities, it is not suitable to use the internal self-tightening valve, and other more suitable connection methods and valve types need to be selected.
