This is a stainless corrugated hose with a PTFE lining inside it. The pressure boundary is still steel — the liner is there to keep the medium off it. We build it when the chemistry beats the metal.
When to specify it
Hydrochloric acid, wet chlorine, strong halide solutions and a range of process chemicals will pit or crack 316L regardless of how well the assembly is made. Upgrading the alloy is one answer and is sometimes right. Lining with PTFE is usually cheaper and, for many media, more certain.
It is also the standard construction for high-purity and hygienic duty, where the requirement is not corrosion resistance but a smooth, inert, non-shedding bore.
Construction
| Element | Detail |
|---|---|
| Liner | PTFE, smooth or convoluted, covering the full bore and flared over the sealing faces |
| Outer hose | Annular corrugated SS 316L, providing pressure containment and flexibility |
| Braid | SS 304 or 316L |
| Temperature | −40 °C to +230 °C — the PTFE governs, not the steel |
| Ends | Flanged, tri-clover or threaded, with the liner flared to the face |
Two engineering cautions we will always raise with you.
Static charge. Fluid moving over PTFE generates an electrostatic charge. In a flammable atmosphere that charge can find a spark path. Where the medium is flammable, specify the conductive (anti-static) PTFE grade and earth the assembly properly — we will build it that way but we need to know the duty.
Vibration. A PTFE-lined metal hose is not suitable for absorbing large vibration amplitudes. The liner does not tolerate the repeated flexing that the corrugated wall handles comfortably. If the job is decoupling a pump, use an unlined assembly and solve the corrosion problem with alloy selection instead.
Static charge. Fluid moving over PTFE generates an electrostatic charge. In a flammable atmosphere that charge can find a spark path. Where the medium is flammable, specify the conductive (anti-static) PTFE grade and earth the assembly properly — we will build it that way but we need to know the duty.
Vibration. A PTFE-lined metal hose is not suitable for absorbing large vibration amplitudes. The liner does not tolerate the repeated flexing that the corrugated wall handles comfortably. If the job is decoupling a pump, use an unlined assembly and solve the corrosion problem with alloy selection instead.
Smooth bore or convoluted
| Smooth bore | Convoluted | |
|---|---|---|
| Flow resistance | Lowest | Higher |
| Flexibility | Lower | Higher |
| Cleanability | Best — preferred for hygienic duty | Good |
| Typical use | Transfer lines, CIP/SIP circuits | Tighter routing, more movement |
