Description
Spiral, helical and U-shaped quartz tubes are hot-formed from straight fused quartz tube stock into a defined coil or bend geometry. The product is specified primarily by the formed shape — coil diameter, pitch, bend radius and connection layout — rather than by the base tube dimensions alone.
Tube OD, ID, wall thickness, cutting, end finishing and welding follow the general Fused Quartz Tubes capability range. This page focuses on the geometry and forming requirements that determine whether a straight tube can be produced as a repeatable coil, helix or U-shaped flow path.
Coil Geometry
| Parameter | Specification Basis | Notes |
|---|---|---|
| Tube OD | Selected from straight quartz tube stock | Base tube OD, ID and wall determine forming behavior |
| Coil Diameter | Drawing-defined | No common standard range is published across suppliers |
| Pitch | Drawing-defined | Can be held constant or programmed to change along the coil |
| Coil Length / Turns | Specified by assembly and flow-path requirement | Defined together with pitch and overall formed length |
| Progressive Radius | Available with CNC-guided forming | Coil radius can change progressively along the formed section |
CNC-guided coil forming allows programmed pitch and radius control, including tapered or progressively changing coil geometry where a constant-radius helix is not suitable.
Bend Design
Process — Straight quartz tubing is locally heated by flame or another controlled hot-forming method and shaped while the glass is in a workable state.
U-Shape Bending — Used for point-to-point flow routing between two parallel or near-parallel connections where a continuous quartz flow path is preferred over a welded elbow assembly.
Bend Radius — The achievable radius depends on tube OD, wall thickness, bore size and the forming setup. There is no single published minimum-bend-radius formula that applies across fused quartz tube suppliers, so the radius is confirmed against the requested tube geometry.
Flow Path
| Feature | Design Requirement |
|---|---|
| Internal Bore | Continuous through the spiral, helix or U-bend on the same OD / ID / wall basis as the starting tube |
| Connection Ends | Normally retained as straight sections for connection to fittings, ports or welded assemblies |
| End Processing | Cut, ground, fire-polished, sealed or welded according to the connection design |
| Branch / Port Addition | Can be combined with quartz welding where a formed tube requires auxiliary ports or branches |
Forming Limits
Achievable coil diameter, pitch and bend radius depend on the ratio between tube OD and wall thickness together with mandrel, roll or guided-forming tooling. Thin-wall large-OD tubes and tight-radius bends place different forming demands on the tube than small-OD thick-wall tubing.
Post-forming annealing is used to relieve thermal and mechanical stress introduced during bending and to stabilize the finished geometry before subsequent cutting, welding or assembly.
Material Options
| Material | Formed-Tube Use | Typical Driver |
|---|---|---|
| Clear Fused Quartz | Spiral coils, U-bends, laboratory flow paths and furnace assemblies | Optical clarity, chemical resistance and high-temperature service |
| Opaque / Milky Quartz | Spiral heaters and thermal exchange components | Diffuse thermal radiation where transparency is not required |
Applications by Geometry
| Geometry | Typical Applications | Primary Design Inputs |
|---|---|---|
| Spiral Coil | Heat-exchange coils, cooling loops, distillation condensers, thermal process tubing | Tube OD / coil diameter / pitch / turns / connection-end length |
| Opaque Spiral Coil | Far-infrared heaters and thermal exchange components | Coil geometry plus opaque-quartz material requirement |
| Helical Tube | Long continuous flow paths in compact cylindrical assemblies | Helix diameter / pitch / overall length / end orientation |
| U-Shaped Tube | Point-to-point flow connections and laboratory furnace inserts | Leg spacing / bend radius / leg length / end orientation |
What to Specify
| Required Input | Why It Matters |
|---|---|
| Tube OD / ID / Wall | Defines the starting tube and strongly affects forming limits |
| Coil Diameter | Sets the main spiral or helix envelope |
| Pitch | Controls spacing between adjacent turns |
| Bend Radius | Defines U-bend or transition curvature |
| Number of Turns / Formed Length | Determines total flow-path length and component envelope |
| Straight-End Length & Orientation | Controls how the formed tube interfaces with fittings or surrounding hardware |
| Clear or Opaque Quartz | Separates transparent process tubing from diffuse-radiation thermal tubing |