Шланг из PTFE-композита

Why a Polypropylene Liner Fails First

Polypropylene is a good liner for dilute acids, alkalis and alcohols, and it is the cheaper build. It fails on three medium families, and it fails from the inside where nobody sees it.

• Aromatics — toluene, xylene and benzene penetrate the polymer, the liner swells, and the bore narrows before any leak appears.
• Chlorinated solvents — methylene chloride and perchloroethylene soften the film and the ply bond weakens under pressure cycling.
• Concentrated oxidising acids — sulphuric, nitric and chromic at strength attack the polymer chain rather than dissolving it, so the failure is embrittlement, not swelling.

PTFE is inert to all three. That is the whole reason this category exists as a separate build rather than an option on the chemical page.

How the PTFE Build Is Put Together

The liner is the difference; the rest of the architecture follows the same logic as every composite hose.

The PTFE here is a film stack, not an extruded tube. That matters in one practical way: a film liner can be built in large diameters without the wall becoming stiff, which is why a 10 inch PTFE hose still has a bend radius of 1,200 mm rather than the multiple-metre radius of a lined rubber hose.

Specification

Size Table

The step from 20 bar to 15 bar happens at 4 inch, not because the liner changes but because the ply stack is sized against hoop stress. A 4 inch bore carries roughly twice the hoop load of a 3 inch at the same pressure, so the pressure class drops instead of the ply count rising without limit. If you need 20 bar above 3 inch, say so at enquiry and the build is engineered rather than taken from the table.

PTFE or Polypropylene: The Cost Question

PTFE typically costs two to three times the polypropylene build for the same bore and length. That premium buys chemical range, not pressure or life. Two situations pay for it immediately: a medium that attacks polypropylene at all, and a duty with an emission or odour limit where permeation through the wall is the problem rather than a leak. A third case is a cleaning cycle with a hot solvent that would swell a PP liner over a few hundred cycles.

Where polypropylene survives, it is the correct answer and we will say so. Specifying PTFE as a default is the most common way buyers overspend on this product.

Static, Conductivity and the Anti-Static Build

PTFE is an insulator. On solvent duty where static can accumulate — transfer through a non-conductive line, dry product, high flow velocity — the assembly needs a conductive path from the bore to the fittings. Our build does that by bonding the helix to the end fittings and checking continuity end to end at 1 ohm/m below 100 mm bore and 2 ohm/m at 100 mm and above. State the earthing requirement at enquiry; a standard PTFE build is not the same product as an anti-static one.

Приложения

• Chemical processing — solvent lines, reactor charging, filtration and centrifuge feed
• Oil and gas — aromatic and chlorinated service where PP has failed before
• Surface finishing — pickling, plating and etching baths
• Pharmaceutical — solvent transfer and cleaning circuits where residue matters
• Paint and coatings manufacture — xylene, toluene and MEK handling
• Waste treatment — mixed acid and solvent waste collection

Installation, Inspection and Service Life

Installation

Keep the bend radius at the bore centreline under pressure: the film stack is strong in tension and weak in kink. Support long runs every 1.5 to 2 m, and use a swivel or elbow at the equipment rather than pulling the hose into alignment. On hot solvent duty, allow the assembly to reach operating temperature before the final alignment check — a PTFE build grows slightly with heat and a cold-set bend can tighten when warm.

Inspection

Look for a bore that has narrowed, a cover with blisters or exposed fabric, and a flattened outer helix. On PTFE duty the first sign of a wrong liner choice is usually a soft or blistered cover with a solvent smell, not a visible leak. Check continuity after any fitting work, and pressure test annually or per local regulation.

Service life

Three to five years is typical in solvent transfer with correct handling. A hose running constantly at 110 to 120 °C is shorter, because the polypropylene backing plies age faster than the PTFE facing even when the product is fully compatible.

Customization, MOQ and Price

• Length — 20 m standard, cut lengths to order with ±1 % tolerance
• Bore — non-standard bores and derated pressure builds on request
• Ends — threaded and unthreaded swage nipples, flanges to EN 1092 or ANSI B16.5, camlock, quick couplings
• Marking — cover colour, printed brand, batch code, medium and temperature text
• MOQ — standard sizes from 100 m; OEM marking and non-standard bore from 500 m per size
• Lead time — 7 to 15 days after order confirmation for standard builds

Made in our own plant in Hengshui: film lay-up, helix forming, assembly and test in one 18,000 m² site across 12 production lines, supplying 70 countries since 2010. A PTFE liner is only as good as the film lot and the ply bond, which is why both are recorded on the assembly record.

Where This Category Stops

• Above +120 °C continuous, use the high temperature composite hose, which is rated to +177 °C.
• Fuel, diesel and biofuel duty belongs to the petroleum category, where the liner and vapour barrier are chosen for hydrocarbons.
• Above 40 bar a composite hose of any liner is the wrong product; specify a wire spiral hose.

Product in This Category

• PTFE composite hose, 20 bar to 3 inch, 25 to 254 mm

Part of the composite hose range, which covers six families from 25 to 254 mm.

Часто задаваемые вопросы

What is the difference between a PTFE composite hose and a PTFE-lined rubber hose?

A composite hose has no rubber tube: the liner is PTFE film backed by bonded polypropylene film and fabric plies, clamped between two steel helices. A PTFE-lined rubber hose uses a vulcanized rubber body with a thin PTFE sleeve inside. The composite build is lighter, has a far smaller bend radius and does not degrade when the rubber body ages.

Can it carry 98 % sulphuric acid?

PTFE is the correct liner for concentrated sulphuric acid. The rating still depends on temperature and flow, so the recommendation is issued per duty rather than per product name.

Why does working pressure drop above 3 inch?

Hoop stress rises with diameter at the same pressure, so the ply stack would have to grow beyond a practical wall thickness. The pressure class drops to 15 bar from 4 inch instead. Higher pressure at large bore is engineered to order.

What is the maximum temperature?

+120 °C continuous, with -30 °C at the cold end. Above +120 °C the polypropylene backing plies lose strength even though the PTFE itself would survive, which is why the ceiling sits where it does.

Does it need a conductive build?

On solvent transfer with flammable vapour, yes. PTFE does not dissipate static, so the assembly must be built with a bonded helix and continuity tested. Tell us the hazard zone and the medium and the build is specified accordingly.

Can a PTFE hose be repaired if the liner is damaged?

No. The liner is bonded into the ply stack and the assembly is crimped, so a damaged liner means the hose is retired. Carry a spare assembly on critical lines rather than planning a field repair.

What are the order quantity and lead time?

20 m is the standard length and standard sizes start at 100 m. OEM marking, non-standard bore and cut lengths start at 500 m per size. Standard builds ship 7 to 15 days after order confirmation.

Send the medium list. We map it against the liner families and answer in writing through the quotation form, including where polypropylene would have been enough.