Order Ermeto tube fittings made of galvanized steel

Ermeto Tube Fittings in Galvanized Steel – Technical Properties and Application Areas

Ermeto tube fittings in galvanized steel are connecting elements for metallic lines that combine mechanical strength, leak-tightness, and corrosion protection. They typically consist of cold-formed or turned steel, which is galvanically zinc-plated to protect the surface against atmospheric corrosion. Compared to bare steel fittings, galvanized variants offer a longer service life in moderately corrosive environments and simplify warehousing, as they are often available as a standard design.

Materials, Surfaces, and Material Properties

The base materials are usually quenched and tempered steels or unalloyed steels with controlled strength values, matched to the mechanical requirements of Ermeto systems (EO/EO2). Galvanic zinc plating is carried out according to DIN standards and achieves typical layer thicknesses between 5 and 15 µm; for specific needs, denser layers or passivating post-treatments are possible. Important material properties include tensile strength, yield strength, and hardness, which influence the tightening torques and setting behavior of the fittings. For high-pressure applications, the compatibility of steel strength and tube wall thickness is crucial; manufacturer specifications for maximum operating pressures must be strictly observed.

Constructive Designs and Connection Variants

Ermeto fittings are available in several designs: union nuts with screw-in or cutting cones, double-cone systems (EO), and advanced double-plate systems (EO2). The designs differ in sealing principle and suitability for soft or hard tubes. In EO systems, sealing is generally achieved by a conical seat in combination with a cutting or pressing point, while EO2 offers higher leak safety and improved assembly control through optimized pressing geometries. Connections are available as straight, elbow, or T-pieces, as well as reducers; thread variants include metric threads, BSP/G, and UNF depending on export requirements.

Seals, Sealing Principles, and Assembly Behavior

Sealing in Ermeto variants is mostly metallic by form fit and elastic by additional sealing elements, such as O-rings or disc seals made of NBR, FKM, or PTFE. The choice of seal depends on the medium temperature, chemical resistance, and permissible pressure. Galvanized steel influences the friction behavior during assembly; appropriate tightening torques prevent material deformation and ensure uniform clamping. For connections with cutting rings, the correct seating of the cutting ring and a form-fitting reception in the tube end are prerequisites to avoid crevice corrosion and leaks.

Corrosion Behavior and Suitability for Industries

Galvanically galvanized Ermeto fittings are suitable for industrial environments with moderate chemical exposure, such as in production plants, hydraulic units, refrigeration technology with non-aggressive refrigerants, and compressed air systems. In more aggressive environments, with seawater contact, or with constant moisture cycles, alternative surfaces (e.g., nickel, zinc-nickel coatings) or stainless steel versions are preferable. The choice is based on a risk assessment of material pairing, medium chemistry, and maintenance intervals.

Application Examples – Structured Practical Cases

Practical Example 1: Assembly of a hydraulic control line in a forming press. Tube material: quenched and tempered steel, outer diameter 12 mm, wall thickness 1.5 mm. Used Ermeto EO fitting in galvanized steel with cutting ring. Before starting assembly, deburr the tube end and check for axial play. Screw in the fitting until the thread seat, then hand-tighten the union nut and tighten with a defined torque. The galvanized surface reduces susceptibility to corrosion in semi-protected halls and allows for documented assembly through groove marking on the union nut.

Practical Example 2: Compressed air distribution in a paint shop. Piping made of low-carbon steel, diameter 25 mm, several T-pieces and elbow connections. Use of EO2 fittings in galvanized steel for increased leak tolerance under cyclic loading. Use of NBR O-rings due to the operating temperature of 5–50 °C. Advantages: easy disassembly for maintenance, reduced downtime due to standardized spare parts.

Practical Example 3: Constructive use in a coolant supply to machining centers. Medium: emulsion mixture, max. temperature 60 °C. Tube fittings in galvanized steel with PTFE disc seal for improved resistance to lubricant components. Tube connections with reducers and elbow connections enable short, defined pipe routing and minimize dead spaces.

Planning, Selection Criteria, and Assembly Instructions

When selecting, operating pressure, medium composition, temperature range, tube material, and required thread types must be primarily checked. EO and EO2 systems differ in assembly behavior: EO2 offers better repeatability due to changed ring geometry and is therefore preferable for frequent assembly cycles. Assembly note: Cut tubes to size, remove longitudinal burrs, prepare tube ends at right angles and burr-free. First, hand-tighten the fittings, then tighten with a defined torque according to manufacturer data. If the surface is re-worked (e.g., re-galvanizing), the function of the sealing surfaces must be checked.

Compatibility, Spare Parts, and Standards

Ermeto systems comply with DIN and ISO requirements for threads, pressure ratings, and material properties. Spare parts such as cutting rings, union nuts, sealing washers, and O-rings are available in standardized dimensions. When replacing, pay attention to dimensional accuracy and material compatibility to avoid galvanic potentials and thus corrosive interactions. For documentation and purchasing, use the catalog specifications with type designations EO/EO2 and exact tube dimensions.

Availability, Logistics, and Economy

Galvanized steel remains economical compared to stainless steel, but offers short delivery times and easy warehousing due to standardized manufacturing. For large quantities, the choice of material pays off through lower acquisition costs. For projects with higher demands on corrosion protection, costly post-treatments or alternative materials must be calculated. Use existing technical data sheets and application notes from the manufacturer for precise cost-benefit analysis; additional information can be found at Technik and under Anwendungsbeispiele.

Product Variants and Classification

The common variants on offer can be distinguished according to the following criteria:

• System type: EO vs. EO2
• Thread and connection form: straight, elbow, T-piece, reducer
• Seal type: metallic, O-ring (NBR/FKM/PTFE), sealing washer
• Surface: galvanically zinc-plated, passivated, alternative coatings

For precise selection, use diameter, pressure, and material tables stored in our product descriptions.

FAQs

1. Are Ermeto tube fittings made of galvanized steel suitable for hydraulic applications?

Yes, if operating pressure, temperature, and medium are within the specifications of the respective EO or EO2 type. For aggressive hydraulic fluids or increased temperature requirements, material-adapted seals (e.g., FKM) and, if necessary, stainless steel versions should be chosen.

2. How does EO differ from EO2 in practice?

EO2 offers improved pressing and sealing geometries, higher repeatability in assembly cycles, and lower leakage rates under dynamic loads. EO is established and cost-effective for static applications. The choice depends on maintenance intervals and pressure changes.

3. Which assembly errors most frequently lead to leaks?

Common errors include unburred tube ends, incorrect cutting ring or seal selection, uneven tightening of the union nut, and exceeding the recommended tightening torques. Consistent preparation of the tube end and adherence to the manufacturer's tightening specifications prevent most leaks.