Heating systems (including civil heating, industrial heating, new energy heating, etc.) have core requirements for pipelines, such as high temperature resistance, thermal fatigue resistance, reliable sealing, adaptability to thermal expansion and contraction, and medium compatibility. Traditional metal pipes (such as galvanized steel pipes) are prone to cracking due to thermal stress, while plastic pipes are limited by the upper temperature limit. However, stainless steel bellows, with their unique material and structural design, can effectively solve these problems and become an ideal pipeline solution for heating systems. The following elaborates on specific application solutions from multiple dimensions.​
In-depth Adaptation of Core Performance Advantages to Heating System Requirements​
The operating environment of heating systems is characterized by large temperature fluctuations (-10℃ to 300℃), diverse media (hot water, steam, heat-conducting oil, etc.), and the existence of thermal stress and vibration. The performance of stainless steel bellows can accurately meet these requirements:​
Excellent High Temperature Resistance and Thermal Stability: 304 stainless steel can withstand medium-temperature environments below 200℃ (such as civil hot water heating), 316 stainless steel can adapt to high-temperature scenarios of 200-400℃ (such as industrial steam pipelines), and special grades (such as 310S) can even work stably in open-fire heating systems above 600℃. The material will not age or have strength attenuation due to long-term high temperatures.​
Thermal Fatigue Resistance and Expansion Compensation Capability: The annular corrugated structure of the bellows endows it with good axial extensibility. During the cycle of heating system startup (temperature rise) and shutdown (temperature drop), it can absorb the length change of the pipeline caused by thermal expansion and contraction (the compensation amount can reach 5%-10% of its own length), reducing interface loosening or pipeline cracking caused by rigid connections. It is especially suitable for connecting boilers, heat exchangers and other equipment with main pipelines.​
Medium Compatibility and Corrosion Resistance: It has tolerance to common heating media such as hot water, steam, and heat-conducting oil. 304 stainless steel can resist scaling of calcium and magnesium ions in water and oxygen corrosion. 316 stainless steel can withstand erosion from sulfur-containing steam and weakly acidic heat-conducting media, avoiding medium leakage caused by corrosion and perforation of the inner wall of the pipeline.​
Sealing Reliability and Pressure-bearing Capacity: Through precision-machined flange, thread and other connection structures, combined with high-temperature resistant sealing gaskets (such as graphite gaskets, metal-clad gaskets), zero-leakage sealing under long-term high temperatures can be achieved. The working pressure can reach 1.6-10MPa, meeting the pressure requirements of low-pressure civil heating (below 0.6MPa) and high-pressure industrial steam systems (above 4.0MPa).​
Heat Conduction Efficiency and Energy Saving: The thermal conductivity of stainless steel (about 16-21 W/(m·K)) is higher than that of plastic pipes, and the annular structure of the bellows can increase the contact area between the medium and the pipeline, accelerating heat transfer. At the same time, the outer wall of the pipeline can be conveniently equipped with an insulation layer to reduce heat loss and improve the energy-saving performance of the system.​
Typical Application Scenarios​
Stainless steel bellows can specifically solve the application pain points of traditional pipelines in different types of heating systems:​
Civil Heating and Hot Water Systems​
Connecting branch pipes between radiators and main pipes: Using the flexibility of bellows, they can easily bypass obstacles such as walls and furniture, reduce the use of elbows, and lower water flow resistance; at the same time, they absorb pipeline expansion and contraction during heating and non-heating seasons to avoid interface leakage.​
Connection between wall-hung boilers and hot water pipelines: They can withstand the 80-95℃ hot water temperature during the operation of wall-hung boilers, resist thermal fatigue caused by frequent startup and shutdown, and are more durable than rubber hoses (easy to age) and copper pipes (strong rigidity), with a service life of more than 15 years.​
Connection of manifolds in low-temperature floor radiant heating (water floor heating): Small-caliber (DN15-DN25) bellows can adapt to the multi-branch layout of floor heating pipes, reduce water flow resistance, and improve heat dissipation uniformity.​
Industrial Heating Systems​
Connection between boilers and steam pipelines: At the outlet of coal-fired/gas-fired boilers, bellows can absorb the severe thermal expansion during boiler startup, protect valves and pipeline interfaces, and avoid steam leakage (steam temperature is usually 150-300℃, pressure 1.0-4.0MPa).​
Heat-conducting oil heating systems: Used for connecting heat-conducting oil furnaces with reactors, dryers and other equipment. 316 stainless steel can withstand long-term erosion of heat-conducting oil (temperature 200-300℃), and its vibration resistance (generated by pump operation) prevents loosening of pipeline joints.​
Pipeline connection of electric heating equipment: Such as the inlet and outlet pipelines of electric heating reactors, bellows can adapt to the local high temperature of electric heating elements, and there is no problem of odor emission from plastic pipes.​
New Energy Heating Systems​
Circulation pipelines of solar thermal collection systems: Connecting solar collectors and hot water storage tanks, 304 stainless steel can resist high temperatures (70-100℃) under direct sunlight and rain corrosion, and the flexible structure adapts to the slight displacement of collectors due to installation angles.​
Water circulation pipelines of air-source heat pumps: In the temperature fluctuation range of -10℃ to 55℃, bellows can compensate for the expansion and contraction of pipelines caused by environmental temperature changes, avoiding low-temperature embrittlement or high-temperature deformation of plastic pipes.​
Special Heating Scenarios​
Steam disinfection pipelines in the food processing industry: The inner wall of stainless steel bellows is smooth and easy to clean, meeting food hygiene standards (such as 3A certification), withstanding 121℃ high-temperature steam disinfection, and having no risk of rust pollution.​
Pipeline connection of laboratory heating equipment (such as oil baths, constant temperature tanks): Small-caliber bellows (DN6-DN15) can accurately adapt to precision equipment, and their vibration resistance ensures stable medium transmission during experiments.
Key Selection Points and Installation Specifications​
1. Scientific Selection​
Material Matching: 304 stainless steel is selected for medium-temperature systems (≤200℃); 316 stainless steel is selected for high-temperature systems (200-400℃) or corrosive media (such as sulfur-containing steam); 310S stainless steel is selected for ultra-high temperature systems (>400℃).​
Caliber and Pressure Rating: Select DN10-DN300 calibers according to the flow rate of heating medium (DN15-DN50 is commonly used for civil purposes, DN50-DN200 for industrial purposes); the working pressure must be ≥1.25 times the system design pressure (for example, if the design pressure of a steam system is 1.6MPa, select bellows with a rating of ≥2.0MPa).​
Connection Method: Threaded connection (with high-temperature resistant raw material tape) is commonly used in civil systems; flange connection (with metal wound gaskets) is mostly used in industrial systems; ferrule joints can be selected for precision equipment connection (to ensure cleanability without dead corners).​
Expansion Compensation Amount: Calculate the thermal expansion amount according to the pipeline length and temperature difference (formula: ΔL=α×L×ΔT, where α is the linear expansion coefficient of stainless steel), ensuring that the compensation amount of the bellows is ≥ the calculated value to avoid excessive stretching or compression.​
2. Installation Specifications​
Pretreatment and Cleaning: Before installation, remove oxide scale and oil stains in the pipeline. High-temperature systems need to be degreased (such as cleaning with trichloroethylene); when connecting with food and pharmaceutical equipment, bellows with electrolytically polished inner walls must be selected to avoid microbial growth.​
Bending and Fixing: The bending radius is ≥ the radius specified by the product (usually 6-10 times the pipe diameter). It is forbidden to apply excessive force during cold bending to cause corrugation deformation; sliding supports are set every 2-3 meters in the straight section (allowing axial expansion), and fixed supports are set at both ends of the compensation section to limit lateral displacement.​
Sealing and Insulation: When flange connection is used, tighten the bolts evenly (step by step diagonally) to avoid seal failure caused by eccentric load; high-temperature pipelines need to be wrapped with insulation layers (such as rock wool, aluminum silicate) outside the bellows, but expansion space must be reserved to prevent the insulation layer from hindering the compensation of the bellows.​
Trial Operation and Testing: After installation, conduct a water pressure test (the test pressure is 1.5 times the working pressure, and the pressure is maintained for 30 minutes without leakage); high-temperature systems need to conduct hot commissioning to monitor whether the bellows expand and contract smoothly and whether there is leakage at the interface.​
Application Benefits​
Prolong System Service Life: The thermal fatigue resistance of stainless steel bellows can extend the trouble-free operation cycle of the heating system to more than 10 years, far exceeding that of galvanized steel pipes (5-8 years) and plastic pipes (3-5 years), reducing replacement costs.​
Reduce Maintenance Costs: Corrosion resistance and high-temperature resistance reduce shutdown maintenance caused by pipeline corrosion and rupture, and annual maintenance costs can be reduced by 40%-60%; especially in industrial heating systems, production losses caused by medium leakage can be avoided.​
Improve Operational Safety: Zero-leakage sealing and anti-thermal stress design reduce the risk of scalds and fires caused by leakage of high-temperature media (such as steam and heat-conducting oil), and can reduce property losses caused by household water leakage in civil heating.​
Enhance System Adaptability: The flexible compensation capability makes pipeline installation not limited by building structures (such as walls and floors), especially suitable for the transformation of heating systems in old buildings, reducing wall excavation and structural damage.​
Summary​
Through the dual advantages of material and structure, stainless steel bellows achieve comprehensive performance of "high temperature resistance, anti-expansion, stable sealing, and long service life" in heating systems. Whether it is the comfort requirements of civil heating or the harsh working conditions of industrial heating, they can provide reliable pipeline solutions, laying a solid foundation for the efficient and safe operation of heating systems.​