Ferrules for fixing hose and plug

Crimp Sleeves for Attaching Hoses and Connectors

Crimp sleeves are mechanical connecting elements that permanently and pressure-tightly join hoses with connectors, couplings, or fittings. The typical material is galvanized steel, optionally a corrosion-resistant stainless steel version for corrosive environments. Unlike clamps or compression fittings, crimp sleeves are plastically deformed with a press, thereby creating a uniform, form-fitting connection along the hose end. The design is optimized for industrial media supply systems with hydraulic, pneumatic, and vacuum technology requirements.

Materials and Coatings

Crimp sleeves are standardly manufactured from nickel-plated or galvanized steel because this combination of strength and corrosion protection provides an economical profile. For acidic or chloride-containing environments, as well as for food applications, stainless steels (e.g., 1.4301 / 304, 1.4404 / 316L) are used. Further surface options include passivated or electropolished finishes to reduce germ formation and improve corrosion resistance. Plastic-coated sleeves are used when metallic contact must be avoided and additional electrical insulation is required.

Designs and Geometries

Crimp sleeves are available in various geometries: cylindrical, conical, with an integrated collar, or with a flange for precise installation. The internal geometry can be designed as a smooth bore, with internal ribs for improved strain relief, or with special profiling for higher medium pressure. The choice of shape depends on the hose material (e.g., NBR, EPDM, PTFE, HNBR), wall thickness, and the type of connector or coupling used. For multi-hose systems and thermal lines, special sleeves with larger jacket thicknesses or thermal protection coatings exist.

Connections, Seals, and Compatibility

Crimp sleeves are compatible with a wide range of industrial connectors and couplings. The sleeve primarily serves as a mechanical connection; systems achieve tightness through a combination with suitable seals or by form-fitting crimping on the hose material. For applications with critical leakage rates, the use of additional O-ring seals at the connection or internal sealing washers is recommended. Selection criteria here include media compatibility, temperature range, and fatigue strength. For high-pressure applications, internal linings made of metal or PTFE are used to prevent flow movements of the hose material and pressure pockets.

Manufacturing and Crimping Processes

The connection is made with hydraulic or mechanical presses that provide defined force-displacement curves. Precision tools (dies) shape the sleeve so that it uniformly compresses the hose without damaging it. For reproducible results, tools with defined target contours and force value monitoring are required. In series production, multi-stage presses are often used, combining pre-forming, final pressing, and, if necessary, subsequent cold hardening in one process step. Quality assurance is carried out via force measurement, visual final inspections, and optionally X-ray or ultrasonic testing.

Selection Criteria: Technical Parameters

When selecting the crimp sleeve, the following parameters are decisive:

• Hose inner and outer diameter, material, and wall thickness
• Operating pressure and maximum pressure surges or impulses
• Operating temperature range and type of medium (hydraulic oil, air, water, chemicals)
• Corrosion protection requirements and environmental class
• Compatibility with connectors/couplings and required sealing solutions

Information in technical data sheets regarding pull-off forces, tensile strengths, and permissible bending cylinders must be checked bindingly. For safety relevance, a safety factor against the calculated stress must be integrated.

Practical Examples

Example 1 – Hydraulic Hose in Manufacturing Automation: A 3/8" hydraulic hose (NBR) with a standard connector is connected in a press line with a galvanized crimp sleeve. The sleeve used has internal ribs to improve strain relief and is crimped with a 60 kN press. After the crimping process, a tensile test (factor 2 compared to operating pressure) and a leak test with test air at 6 bar are performed. Result: a permanent, pressure-tight connection without hose damage.

Example 2 – Chemical Dosing in Laboratory Systems: PTFE-lined hoses are connected with stainless steel crimp sleeves to avoid metallic contamination. The sleeve is internally fitted with a PTFE inlay, which forms the sealing plane during deformation. Assembly is carried out with a fine pressing station at reduced force to avoid perforating the inlay. Subsequently, a pressure test with corrosive medium is simulated in a short-term exposure test.

Example 3 – Pneumatic Distribution Network in Paint Shop: Polyurethane hoses are assembled with coated crimp sleeves. The surface is electrically insulating and protects against paint adhesion. Pressing with defined displacement prevents pinching; the sleeve has a flange that serves as a mounting stop and ensures a reproducible insertion depth.

Assembly Instructions and Test Procedures

Before assembly, the hose end and sleeve must be deburred and checked for damage. The hose should be vented before pushing it on and, if necessary, slightly warmed to achieve a better fit. The sleeve may only be crimped with certified dies of the appropriate size. After pressing, tensile and leak tests must be carried out. Documentation of the test parameters (pressing force, die identification number, test pressure, test duration) is required to ensure traceability and quality.

Standards and Certificates

Relevant standards for industrial applications include DIN EN ISO 12100 (Safety of machinery), DIN EN 853/854/855 (hydraulic hoses), and industry-specific requirements (e.g., DIN, ISO, SAE). Material certificates (EN 10204) and manufacturer declarations on corrosion resistance are to be provided upon request. Special attention should be paid to approvals for food contact or ATEX conformity if the system is operated in potentially explosive atmospheres.

Service Life, Maintenance, and Causes of Failure

Service life depends on pressure cycles, temperature changes, and chemical stress. Typical causes of failure include incorrect die selection, over-crimping, under-crimping, poor surface quality at the hose end, and unsuitable sealing solutions. Regular visual inspections, recurring leak and tensile tests, and documentation of operating loads prevent unexpected failures. In maintenance, a replacement interval is often defined based on the number of cycles and operating conditions.

Product Range and Custom Solutions

The available product range includes standard sizes for LINE DIAMETERS from small pneumatic lines to large hydraulic hoses, special lengths, flanged versions, and custom-machined die shapes. For series projects, customized test plans and batch certificates are possible. Further technical information and application examples can be found under Technology and Application Examples.

FAQs

1. Which sleeve is suitable for high-pressure hydraulics?

For high-pressure hydraulics, hardened steel sleeves with suitable internal profiling and, if necessary, metal inlays should be chosen; stainless steel 1.4404 material for corrosive media; pressing tools must deliver the specified force curve and be documented.

2. Are crimp sleeves suitable for all hose materials?

Crimp sleeves work for many elastomer and PTFE hoses, but the sleeve and crimping process must be designed for the material, wall thickness, and temperature; for sensitive or thin-walled hoses, internal inlays or special dies are required.

3. What tests must be performed after assembly?

Tensile tests, leak tests at operating and test pressure, and visual inspections are absolutely necessary; in series production, measuring the pressing force and documenting the die identification for traceability is also recommended.