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Plastic Hoses and Spirals – Material Selection, Designs, Application Limits

Plastic hoses and spirals provide precise conveying and protective functions in industrial processes. The crucial factor is the appropriate combination of material, wall structure, reinforcement, and sealing to safely meet pressure, temperature, and chemical requirements. Commonly used materials include polyurethane (PU), polyamide (PA), polyvinyl chloride (PVC), polyethylene (PE) including cross-linked variants (XLPE), and fluoropolymers such as PFA. Each material possesses defined properties: PU offers high abrasion resistance and flexibility, PA (polyamide) provides high pressure resistance and good chemical resistance, PVC is economical and can be made flame-retardant, PE is resistant to moisture and many chemicals, PFA offers the highest resistance to aggressive media and high temperatures.

Material-Related Characteristics and Selection Criteria

When selecting, mechanical load capacity, bending radius, temperature range, resistance to media, and electrical conductivity are paramount. PU hoses are suitable for finely dosed conveying systems and tool connections, typically temperature-resistant from -40 °C to +80 °C, and in special mixtures up to +100 °C. PA hoses typically cover -30 °C to +120 °C and are suitable for compressed air, vacuum, and near-hydraulic applications. PVC variants offer wide availability and cost-effective solutions, often with plasticizer content, temperature limits up to approximately +60 °C; flame-retardant or welding-spark-resistant mixtures are available. PE and cross-linked PE are chemical and UV resistant, often used for outdoor lines and abrasive media. PFA and PTFE are suitable when aggressive acids, solvents, or high temperatures occur.

Designs: Straight Hoses, Spirals, Multi-Layer Systems

Straight hoses come in smooth, reinforced, and fabric-braided versions. Fabric inserts (textile fabric, metal spirals) increase the maximum operating pressure and limit expansion under vacuum. Spiral hoses reduce restoring forces, minimize space requirements, and are ideal for hand tools, compressed air lines, and robot connections, as they retract compactly when not in use. Multi-layer hoses with inner and outer jackets allow the combination of different properties, e.g., a chemical-resistant inner layer with an abrasion-resistant outer jacket. Pressure and vacuum specifications vary depending on the design: softer PU hoses have lower maximum pressures, while reinforced PA or PVC hoses achieve higher operating pressures and vacuum resistance.

Connections, Seals, and Quick-Connect Technologies

The selection of the hose connection is crucial in practice. Common connection systems include cone, clamp, hose clamp, and quick-connect variants such as Legris quick couplings. Suitable sealing materials (NBR, FKM/Viton, EPDM, PTFE) are chosen according to the medium: NBR for oil and air applications, EPDM for water and steam applications, FKM for aggressive fuels and higher temperatures, PTFE for maximum chemical resistance. Quick-connect hoses simplify assembly and maintenance but increase the demands on O-ring selection and installation environment. For connections subject to rotation or vibration, form-fitting union nuts or clamping systems with inserted seals are preferable to prevent leaks.

Application Areas and Standards

Plastic hoses and spirals are used in compressed air networks, water and coolant lines, oil and fuel supply, chemical transfer, food and pharmaceutical applications, as well as in protection and cable management. Industry-relevant requirements include purity (food conformity according to EU regulations), conductivity (antistatic for flammable media), flame retardancy, and welding spark resistance in environments with spark formation. Standards and test procedures that should be considered include DIN/ISO norms for pressure tests, food contact, temperature classes, and electrical resistance. Technical documentation such as pressure loss curves, bending radius specifications, and service life estimates are part of standard-compliant selection.

Practical Examples – Structured Use Cases

1) Assembly of a compressed air tool station: A welding-spark-resistant PU spiral hose with antistatic design is installed on a Legris quick coupling, in combination with an NBR O-ring for oil compatibility. The semi-automatic assembly reduces the bending radius and prevents kinks during tool changes, while simultaneously ensuring strain relief through an attached union nut. Test protocol: 10,000 cycles, pressure 6 bar, leakage rate <0.1 L/min.

2) Conveying line for cooling lubricants in a CNC machine: A fabric-reinforced PA hose with a smooth inner surface minimizes deposits and ensures constant flow rates. Connections with a conical screw-in system and FKM seal ensure resistance to oil additives and elevated temperatures. Maintenance interval: Visual inspection and replacement of seals every 12 months, pressure test before re-commissioning.

3) Production cycle in food packaging: A PFA inner hose in combination with a PE outer jacket is used to tolerate aggressive cleaning agents and hot water. The use of food-grade seals and documented residue analyses enables compliance with hygiene requirements. Assembly is carried out with stainless steel couplings; surface roughness of the contacts is monitored to prevent germ formation. Cleaning protocol according to CIP routine.

Installation Recommendations and Maintenance

Before installation, the hose inner diameter, bending radius, and the piston diameters of connections must be checked. Long, tight bending radii reduce service life and increase the risk of leaks. When using quick-connect systems, the O-ring shape and material must be matched to the medium and documented with the manufacturer's approval. For conductive applications, grounding measures and resistance measurements are required after installation. Regular visual inspections for cracks, deformations, swelling, or discoloration are mandatory, as are pressure and leak tests at planned intervals. Replacement criteria include permanent cracking, material embrittlement, recurring leaks despite tightening, and temperature exceedance.

Best Practices for Storage

Hoses should be stored protected from UV radiation, ozone, and direct heat. Spiral forms must not be deformed or permanently stretched during storage. When storing below temperature or humidity limits, the declared shelf life of the material must be observed to avoid plasticizer loss or embrittlement.

Special Variants and Individual Solutions

For special requirements, we offer antistatic, flame-retardant, welding-spark-resistant, and highly flexible high-performance compounds. Customer-specific solutions include multi-layer hoses with a barrier layer for aggressive media, shielded spirals for ESD applications, and reinforced hose lines with a metal spiral for vacuum cells. Customizations include customer-specific lengths, quick couplings mounted on one side, color-coded outer layers for media identification, or laser markings for traceability. Further technical information and configuration options can be found on our technology page https://maku-industrie.de/technik and specific application examples under https://maku-industrie.de/anwendungsbeispiele.

Performance Data, Tests, and Documentation

For each hose variant, technical data sheets should be available, containing information on temperature range, operating pressure, maximum pressure, bending radius, Shore hardness, tensile strength, and media resistance. Test protocols include pressure tests, temperature cycles, abrasion tests, and electrical resistance tests for antistatic variants. When used in food processing industries, conformity certificates (EU regulations) and cleaning protocols are part of the delivery documentation.

List of Critical Test Parameters

• Pressure resistance, vacuum resistance, temperature limits, bending radius, media compatibility, electrical conductivity/ESD, abrasion resistance, certificates (food, flame class)

Procurement and Customization

When purchasing, length tolerance, inner diameter tolerances, material certificates, and the desired customization (connections, sleeves, protective spirals, hose clamps) must be specified. Cutting patterns and project drawings enable quick quotes and manufacturing. For standard items, stock and fast customization are available; for special hoses and multi-layer versions, we offer tailor-made production runs including material approval.

FAQs

Which materials are suitable for oil applications?

NBR and FKM (Viton) are the primary choice for seals; for the hose itself, PA-braided or special oil-resistant PU compounds are suitable. Selection is based on temperature, additives in the oil, and required operating pressure.

What is the service life of a PU spiral hose under workshop conditions?

Typical service life depends on load, temperature, and abrasion; with normal handling and operating pressure of 6–8 bar, 1–3 years are realistic, shorter with high stress and intensive UV/ozone exposure. Regular inspection extends practical service life.

When is an antistatic version necessary?

Antistatic hoses are required when flammable gases, vapors, or finely dispersed particles are conveyed or in explosion-hazardous areas. Plant operator specifications or risk assessments define limit values for specific resistance and grounding requirements.