This page provides a comprehensive analysis of the core elements of flexible metal hoses, covering material characteristics, structural design, diverse application scenarios in industrial, construction, and HVAC sectors, precise selection logic, various connection methods, size specifications, installation and maintenance guidelines, and quality certification systems. Featuring a stainless steel corrugated inner core, this product offers vibration absorption, thermal expansion compensation, and resistance to high temperatures, high pressures, and corrosive media. It is widely used in demanding applications such as steam pipelines, chemical reactors, ship exhaust systems, and semiconductor vacuum systems, serving as a critical flexible component for ensuring the safe and stable operation of these systems.
What Is a Flexible Metal Hose?
Bellows absorb axial, lateral, and angular displacements through the compression/stretching of their own folds, and the braided layer balances system pressure, achieving vibration isolation and displacement compensation. In steam/gas/liquid transportation, they reduce stress concentration in pipelines, prevent flange leakage and excessive equipment vibration, and extend system lifespan.
SS321 2 Inch Corrugated Welding-neck Flange Flexible Metal Bellow Hose
Our flanged flexible metal bellow hose is mainly used for pipe connection where there's high temperature and pressure in pipeline system.
Compensates for thermal expansion displacement of floor slabs in commercial complex air conditioning water pipes, preventing tile detachment; reduces circulating pump vibration noise by 10-15dB in hospital heating networks, improving patient comfort; adapts to precision air conditioning pipelines in data center cooling systems, ensuring a constant temperature and humidity environment.
Gas & Steam Transport
Gas & Steam Transport
Suitable for urban natural gas main pipelines, withstands PN100 high pressure to prevent leaks; absorbs 550℃ thermal expansion in power plant main steam lines, working with guide supports to control displacement direction, extending pipeline life by more than 30%.
High Pressure & High Temperature Systems
High Pressure & High Temperature Systems
In chemical high-pressure reactors, a double-layer corrugated pipe + double braided layer structure is used, withstanding 600℃ high temperature and 100MPa pressure, and verified by FEA simulation to have a fatigue life of ≥10000 cycles; transports high-temperature heat transfer oil in molten salt solar thermal power generation systems, resistant to corrosion and high-temperature oxidation.
Vacuum Applications
Vacuum Applications
Braided-free vacuum hoses use 0.1mm wall thickness 316L stainless steel corrugated pipes, achieving a vacuum degree of 10⁻⁶Pa, used for connecting vacuum chambers of semiconductor lithography machines, preventing gas penetration from affecting chip yield; maintains a high vacuum environment in vacuum coating equipment, ensuring coating uniformity.
Material Types of Flexible Metal Hose
Machine Flexible Metal Hose: Used in CNC machine tool hydraulic pipelines, absorbing cutting vibrations and protecting precision servo valves; Exhaust Flexible Metal Hose: Withstands 1200℃ ship engine exhaust, suitable for boiler flues, reducing noise emissions; Compressor/Air Dryer Hose: Reduces pulsating pressure at the compressor outlet, preventing fatigue fracture of air pipelines; Steam/Gas/Oil Hoses: Transports 550℃ high-temperature steam to nuclear power equipment, withstands 100MPa pressure for natural gas transport, and resists H₂S corrosion for oil transport.
304 Stainless Steel: General purpose, containing 18% chromium and 8% nickel, resistant to corrosion from water, air, and oil media, suitable for normal temperature and low-pressure applications; 316 Stainless Steel: Contains 2% molybdenum, resistant to seawater chloride ion corrosion, suitable for ship pipelines and coastal chemical plants; 321 Stainless Steel: Stabilized with titanium, resistant to high-temperature oxidation, suitable for steam pipelines and high-temperature gas systems.
Carbon Steel Flexible Metal Hose
Suitable for low-pressure and normal temperature applications such as fire sprinkler systems, low cost but requires epoxy coating to prevent rust, pressure rating PN1.6.
Galvanized Flexible Metal Hose
Hot-dip galvanizing treatment enhances weather resistance, suitable for outdoor rainwater pipes and fire hydrant connections, preventing corrosion caused by rainwater.
PTFE Lined Flexible Metal Hose
Lined with polytetrafluoroethylene (PTFE) coating, resistant to strong acids and bases (such as 98% concentrated sulfuric acid and 20% hydrochloric acid), suitable for chemical pickling pipelines and electroplating tank connections, ensuring media purity and preventing contamination.
Plastic-coated / Special Surface Treatment
Outer coating of polyurethane elastomer, improving wear resistance and UV resistance, suitable for outdoor exposed natural gas pipelines; special surface treatments such as anodizing enhance the corrosion resistance of aluminum alloy hoses.
Structure & Manufacturing Types
Corrugated (Bellows) Hose
Single-layer corrugated hose:Wall thickness 0.2-0.5mm, suitable for low-pressure applications such as air conditioning water pipes, low cost but with average fatigue resistance; Double-layer corrugated hose:Wall thickness 0.8-1.2mm, 50% higher pressure resistance, suitable for high-pressure applications such as hydraulic systems; Welded vs. Seamless:Welded corrugated hoses use plasma welding technology, resulting in lower cost; seamless corrugated hoses use cold rolling technology, offering superior fatigue resistance and suitable for high-frequency vibration applications.
Braided Flexible Metal Hose
The braided layer uses 304 stainless steel wire with a braiding density of ≥80%, enhancing radial pressure resistance, suitable for applications with severe vibrations such as compressor outlets and hydraulic hammers.
Unbraided Flexible Metal Hose
The unbraided structure is lightweight and has a small bending radius, suitable for low-pressure vacuum applications such as vacuum pump connections and semiconductor equipment.
Reinforced / High Strength Structure
Uses reinforced corrugated hose + multi-layer braiding, with a pressure rating of up to PN100, suitable for extreme conditions such as nuclear power plant main steam pipelines and deep-sea oil and gas transportation.
Performance Characteristics
High Temperature Resistant Flexible Metal Hose
Withstands a wide temperature range of -196℃ to 1200℃, made of 321 stainless steel or Inconel alloy, suitable for rocket engine fuel lines and nuclear reactor cooling systems.
Corrosion Resistant / Chemical Resistant Hose
Resistant to acid, alkali, and salt corrosion, uses a PTFE liner or Hastelloy bellows, suitable for chemical pickling, electroplating, and wastewater treatment systems.
High Pressure Flexible Metal Hose
Withstands high pressure of 0-100MPa, features a double-layer bellows + double braided layer structure, and its pressure resistance is verified through hydrostatic testing. Suitable for high-pressure reactors and oil and gas pipelines.
Vacuum Flexible Metal Hose
Achieves a vacuum level of 10⁻⁶Pa, features a thin-walled structure without a braided layer, and its sealing performance is verified using a helium mass spectrometer leak detector. Suitable for semiconductor equipment and vacuum coating systems.
Anti-Vibration / Flexible Hose
Reduces mechanical vibration noise by 10-15dB, uses rubber damping pads in conjunction with a braided layer to protect equipment supports and extend the lifespan of pump sets and compressors.
Connection Types
Flanged Flexible Metal Hose
Supports DIN PN10/PN16, ANSI Class150/Class300, and JIS 10K/20K standard flanges, compatible with piping systems in different countries, and uses metal spiral wound gaskets to ensure sealing.
Threaded Flexible Metal Hose
Uses NPT 1/2"-4" or BSP 1/4"-2" threaded connections, suitable for small-diameter pipes such as laboratory equipment, offering easy installation and reliable sealing.
Welded End Metal Hose
Butt welding uses TIG welding process, and socket welding uses automatic welding machine, suitable for high-pressure and high-temperature applications such as boiler main steam lines, ensuring no leakage at the connection.
6.4 Quick Coupling Metal Hose
Uses stainless steel quick-release couplings, suitable for applications requiring frequent disassembly, such as laboratory gas lines and temporary pipe connections, offering simple operation and reliable sealing.
Size & Specification Guide
Definition
An expansion joint is a flexible connecting device installed in a structure or piping system that allows for axial, lateral, and angular displacement caused by thermal expansion, seismic loads, wind loads, or mechanical vibrations, preventing engineering accidents such as cracking, leakage, and fatigue failure due to stress concentration.
Working Principle
Using a metal bellows as the core elastic element, displacement compensation is achieved through the compression or stretching of its folds. Combined with connecting components (welded/flanged/sleeved) at both ends and guiding structures, it balances thermal stress and mechanical vibrations in the system, maintaining pipeline straightness and equipment operational stability.
Quality Grades & Certifications
The product utilizes the ISO9001 quality management system, is CE certified, and complies with the ASME B31.3 standard. Third-party inspections, such as those conducted by SGS, include pressure testing, leak testing, and vibration testing to ensure product reliability.
OEM & Custom Services
We support OEM customization of flexible metal hoses, offering options for material selection (304/316/321), length customization (0.5m-20m), connector type customization (flange/threaded/welded), and pressure rating customization (PN0.6-PN100). We also provide drawing review, welding method selection (TIG/MIG), and corrosion resistance optimization solutions (PTFE lining/Hastelloy). Our mass production capabilities meet the needs of large projects, ensuring short delivery times.
A comprehensive assessment is required, considering factors such as media type (gas/liquid/steam), operating temperature/peak temperature, static pressure/pulsating pressure, displacement (axial/lateral/angular), installation length, end connector type, and safety factor (service life and fatigue cycles). Calculate the thermal expansion using ΔL = α·L·ΔT, and ensure the compensation capacity is at least 1.2 times the calculated displacement. Select a safety factor of 1.5-2.0 to ensure the selected hose meets the operating conditions
Installation and Maintenance Guide
The correct installation direction must match the media flow direction indicated by the arrow to avoid stress concentration caused by reverse installation; avoid twisting or overstretching during installation, and ensure the bending radius is ≥3 times the pipe diameter; set up supports, guides, and fixing points to control the direction of pipe displacement; vacuum hoses require leak testing using a helium mass spectrometer; regularly check for wear on the braided layer, weld cracks, corrosion, and signs of leakage; lubricate connectors quarterly and conduct a comprehensive inspection annually, promptly repairing or replacing defective parts
It can withstand a wide temperature range of -196℃ to 1200℃, depending on the material: 304 withstands -50~600℃, 316 withstands -50~800℃, PTFE withstands -200~260℃, and Inconel withstands -253~1093℃.
316 stainless steel is more resistant to chloride ion corrosion and is more suitable for wet steam systems; 304 stainless steel is suitable for dry steam applications.
The braided layer enhances radial pressure resistance and is suitable for high-pressure applications; the unbraided structure is lighter and suitable for vacuum/low-pressure applications.
A flexible metal hose is a flexible piping component composed of a corrugated tube, a braided layer, and end fittings. It absorbs vibration and displacement through the elastic deformation of the corrugated tube, and is used to transport gas, liquid, or steam media.
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