Parker Legris ferrules made of brass or stainless steel

Parker Legris Support Sleeves in Brass or Stainless Steel

Parker Legris support sleeves secure hose connections under elevated temperature and pressure conditions. The sleeves prevent constrictions, ensure dimensionally stable transitions in compression fittings, and improve sealing performance in thermoplastic tubing. Available in brass for corrosion-resistant general applications and in stainless steel for aggressive media, high temperatures, and hygienic requirements.

Material Properties and Operating Limits

Brass support sleeves are corrosion-resistant to water, compressed air, and non-aggressive hydraulic fluids; typical operating temperatures range from -40 °C to +120 °C. For higher temperatures, abrasive media, or corrosive environments, stainless steel support sleeves (AISI 304/316) are suitable, allowing continuous use up to +300 °C and short-term peaks beyond. Mechanically, stainless steel sleeves offer higher fatigue strength and less plastic deformation under pressure, while brass offers better formability and lower manufacturing costs.

Geometry, Tolerances, and Interfaces

Parker Legris support sleeves are dimensioned to be compatible with Legris compression fittings and thermoplastic tubing (e.g., PA, PU, PE, PTFE-lined hoses). Essential dimensions include outer diameter, inner diameter, insertion depth, and chamfer angle. Inner diameters are matched to nominal diameters from 4 mm to 25 mm, with insertion depth typically 1–1.5× tube Ø to fully support the compression ring position. Tolerances are generally ±0.05 mm for tight fits, minimizing the risk of leakage and grooving.

Connections, Seals, and Compression Ring Compatibility

Support sleeves work with compression rings and conical fittings: the sleeve evenly distributes clamping forces and prevents the compression ring from penetrating thermoplastic walls. In systems with O-ring or sealing ring connections, the sleeve ensures a constant cross-section and prevents channel formation that could lead to mixing or leakage. For metallic hoses or reinforced PTFE lines, support sleeves also transmit force into the union nut. Crucial for sealing performance is the correct combination of sleeve, compression ring, and sealing material (NBR, FKM, EPDM) according to medium and temperature.

Designs, Surfaces, and Special Machining

Support sleeves are available bare, nickel-plated, or passivated. A nickel-plated brass sleeve increases wear resistance and corrosion protection in humid environments, while passivated stainless steel stabilizes the surface against organic deposits and pitting corrosion. Special designs with targeted longitudinal grooves improve penetration into soft hoses and increase clamping force distribution. Inner chamfers are standardly angled at 15°–30° to prevent damage to the hose wall during insertion. For high-precision applications, ends are deburred and ground to a roughness of Ra ≤ 0.8 µm.

Practical Examples: Application Scenarios

1) Cooling Circuit of a Production Plant (Thermoplastic Hoses, 10 bar, 90 °C)
An automated welding system uses thermoplastic hoses (PA) for water supply. Without a support sleeve, the hoses bulge under pressure at the fitting, and the compression ring cuts in. By inserting a brass support sleeve with appropriate insertion depth, the compression ring is guided on the sleeve, the hose wall is stabilized, and the connection remains tight even at 8–10 bar and 90 °C. Assembly tip: Deburr hose end, push in sleeve until stop, place compression ring, and tighten fitting to specified torque.

2) Pneumatics in Shift Operation (PU Hose, 16 bar, -30 °C to +60 °C)
In conveyor systems, frequently moving pneumatic circuits often lead to tube deformations at connection points. Stainless steel support sleeves prevent the hose from collapsing under vacuum and increase the lifespan of the compression fitting. The smooth outer surface reduces friction on guide tubes. Installation routine: appropriately sized sleeve, slight preload when inserting the hose, checking hose pull-out under load.

3) Chemical Supply in Paint Booths (PTFE Hose, Aggressive Medium, 6 bar, +120 °C)
PTFE hoses require pressure-distributing support sleeves to prevent seals from being stressed at specific points. Stainless steel 316 offers resistance to solvents and weak acids. Specification: Sleeve with polished inner surface to prevent material deposits and chemically resistant FKM seal in the fitting.

Selection Criteria and Dimensioning

When selecting a support sleeve, the following points are crucial:

• Medium, temperature range, and pressure; material choice (brass vs. stainless steel) according to corrosion and temperature requirements
• Hose material and wall thickness; inner diameter of the sleeve must ensure close contact without expansion
• Compatibility with the compression fitting (brand and standard comparison) and required insertion depth
• Surface treatment and, if necessary, geometric optimization (grooves, chamfer, deburring)
• Assembly access and possibility for non-destructive inspection or interchangeability

Assembly Instructions and Quality Assurance

Before assembly, the hose end must be cleaned and checked for damage. The sleeve must be inserted flush and without twisting until it stops. For thermoplastic hoses, slight heating (max. +40 °C) is permissible to facilitate insertion, but not beyond the material limit. When tightening the fitting, the manufacturer's recommended torques must be observed to avoid over-compression and material damage. After assembly, leak tests and pull tests (pull-out force) must be performed. Series productions benefit from random sample inspections of insertion depth, surface roughness, and material analyses (spectral analysis for stainless steel).

Cost-effectiveness and Inventory Management

Brass sleeves are cost-effective for standard applications; stainless steel variants justify their price for increased demands on resistance and lifespan. To increase service life and reduce downtime costs, a rationalized inventory spectrum based on common nominal sizes is recommended. For quick maintenance, pre-assembled mounting kits with suitable compression rings and seals can be stocked.

Further technical data and specific application examples can be found on our technical page: maku-industrie.de/technik and in our documented case studies: maku-industrie.de/anwendungsbeispiele.

Conformity, Standards, and Traceability

Parker Legris support sleeves comply with industry standards for connection technology. Material certificates (EN-, ISO-conformities) are available for stainless steel deliveries. For food-grade or pharmaceutical applications, materials and surface treatment must be specified accordingly. For critical applications, batch labeling and traceability of raw materials are recommended.

Maintenance, Replacement Cycles, and Waste Management

Regular visual inspection for grooves, corrosion, or deformation is mandatory. Replacement intervals depend on operating conditions: in normal operation after 2–5 years, significantly earlier with aggressive media or high thermal loads. Material residues and replaced sleeves must be recycled according to local disposal regulations; brass and stainless steel are fully recyclable and economically valuable.

FAQs

1. Which support sleeve is suitable for my thermoplastic tube?
Choose brass for temperatures up to ~120 °C and non-aggressive media; choose stainless steel (AISI 304/316) for temperatures above 120 °C, aggressive media, or increased mechanical stress. Check the nominal diameter and wall thickness of your tube and observe the required insertion depth (typically 1–1.5× tube Ø).

2. How do I correctly assemble a support sleeve?
Deburr, clean the hose end, insert the sleeve until it stops, slide on the compression ring, and tighten the fitting according to the manufacturer's torque. For thermoplastics, moderate heating can facilitate insertion. Finally, perform leak and pull tests.

3. Which seals are compatible?
Depending on the medium: NBR for mineral oils and air, EPDM for water and alkaline media, FKM for high temperatures and aggressive chemicals. The choice of seal must consider temperature and chemical resistance and be coordinated with the sleeve and compression ring.