Eurobalt manufactures custom hydraulic cylinders of any complexity — from compact plunger units to large-bore, long-stroke assemblies — based on customer drawings or technical specifications. This particular unit is a double-acting cylinder with 200 mm stroke and flange mounting on both ends, rated at 160 bar working pressure. Unit weight approximately 176 kg. The full production cycle was handled in-house: material procurement with mill certificates, CNC machining, welding, hard chrome plating, multi-layer surface coating, seal assembly, and hydraulic pressure testing at 240 bar.
Material
| Standard | Grade |
|---|---|
| EN 10297-1 | E355 (≈ DIN St52) |
| EN 10083-2 | C45 / 1.0503 (AISI 1045) |
The cylinder tube and structural components (flanges, endcaps, piston) are manufactured from E355 seamless steel — a medium-carbon, low-alloy structural steel with a minimum yield strength of 355 MPa and tensile strength in the range of 490–630 MPa. This grade offers an excellent combination of strength, weldability, and machinability, making it a standard choice for hydraulic cylinder bodies operating at pressures up to 250 bar.
The piston rod is manufactured from C45 medium-carbon steel (EN 10083-2 / AISI 1045), subsequently hard chrome plated to provide a wear-resistant, corrosion-resistant bearing surface.
Cylinder tube chemical composition (heat analysis, EN 10297-1 E355):
C ≤ 0.22 %, Si ≤ 0.55 %, Mn ≤ 1.60 %, P ≤ 0.025 %, S ≤ 0.025 %
Dimensions
| Parameter | Value |
|---|---|
| Bore diameter | 180 mm |
| Rod diameter | 125 mm |
| Stroke | 200 mm |
| Overall length (retracted) | 682 mm |
| Front flange OD | 388 mm |
| Bolt hole PCD | 330 mm |
| Bolt holes | 8 × ø38 mm |
| Port connections | BSP |
Hydraulic Parameters
| Parameter | Value |
|---|---|
| Working pressure | 160 bar |
| Test pressure | 240 bar |
| Operating temperature | −30 °C to +80 °C |
| Cylinder type | Double-acting |
| Mounting | Front and rear flange |
The cylinder is designed for a 1.5× safety factor between working and test pressure, consistent with standard hydraulic cylinder design practice per ISO 10100.
Sealing System
The sealing arrangement includes a high-performance polyurethane piston seal set, rod seal, wiper ring, guide rings, O-rings, and back-up rings. All seals are rated for the operating pressure and temperature range. The thread connections between the cylinder head and tube are secured with anaerobic thread-locking adhesive to prevent loosening under hydraulic pulsation.
Hard Chrome Plating
| Parameter | Value |
|---|---|
| Rod material | C45 (EN 10083-2) |
| Chrome layer thickness | ≥ 30 μm |
| Surface hardness (rod) | HRC 28–33 (base) |
| Chrome hardness | ≈ HV 850–1050 |
The piston rod receives hard chrome plating after final machining. The chrome layer provides a low-friction, corrosion-resistant surface for the rod seal interface. The minimum coating thickness of 30 μm ensures adequate service life in industrial hydraulic applications.
Surface Coating
| Layer | Minimum thickness | Standard |
|---|---|---|
| Primer | 40 μm | — |
| Intermediate coat | 40 μm | — |
| Topcoat (RAL 7035) | 20 μm | RAL 7035 |
| Total | 100 μm | — |
The cylinder body is coated with a three-layer acrylic polyurethane paint system in RAL 7035 (light grey, high-gloss finish). The multi-layer approach provides corrosion protection and UV resistance suitable for both indoor and outdoor installations. Mounting flanges, rod surface, and port threads are masked during painting.
Production Process
The manufacturing cycle included 8 main stages:
Stage 1
Material Procurement and Incoming Inspection
Raw materials were procured with EN 10204 Type 3.1 mill test certificates. Incoming inspection verified chemical composition, mechanical properties (yield strength, tensile strength, elongation, impact toughness), and dimensional compliance of the seamless tube blanks and round bar stock.
Stage 2
CNC Machining
All cylinder components were machined on CNC lathes and machining centres:
- Cylinder tube: boring, honing to H8 tolerance on the bore surface
- Front flange: turning, drilling of 8 × ø38 bolt holes on ø330 PCD
- Rear endcap: turning, internal threading (metric fine thread)
- Cylinder head (gland): turning with precision bore for rod seal housing
- Piston: turning with seal grooves to specified dimensions
- Piston rod: turning to f7 tolerance, threading
Stage 2
Stage 3
Welding
The front flange and rear endcap mounting ring were welded to the cylinder tube. Weld quality was inspected visually and by dimensional verification of the completed weldments.
Stage 4
Hard Chrome Plating
The piston rod was hard chrome plated with a minimum coating thickness of 30 μm. After plating, the rod surface was ground and polished to achieve the required surface finish for reliable seal performance.
Stage 4
Stage 5
Surface Treatment
The cylinder body, flanges, and endcaps were sandblasted to Sa 2.5 and coated with a three-layer paint system: primer (40+ μm), intermediate coat (40+ μm), and acrylic polyurethane topcoat in RAL 7035 (20+ μm). Total dry film thickness exceeds 100 μm.
Stage 6
Assembly
All components were assembled with the specified sealing elements. Thread-locking adhesive was applied to the gland and endcap threads. The piston rod, piston, seals, guide rings, and wiper were installed in sequence. Port fittings and dust plugs were fitted.
Stage 6
Stage 7
Pressure Testing
Each assembled cylinder was pressure-tested at 240 bar (1.5× working pressure) and held under pressure for a minimum duration. The test verified zero external leakage, stable pressure holding, and smooth rod extension/retraction. Test results were documented per unit.
Stage 8
Marking, Final Inspection, and Packaging
Each cylinder was engraved with a unique serial number, week, and year of manufacture. Final dimensional and visual inspection was completed. Cylinders were wrapped in protective film and packed into wooden crates with internal padding, with spare seal kits included in each shipment.
Stage 8
Quality Control
- EN 10204 Type 3.1 mill test certificates for all raw materials
- Incoming dimensional inspection of tube blanks and bar stock
- In-process dimensional checks at each machining stage (process routing cards)
- Weld visual inspection
- Chrome plating thickness verification (≥ 30 μm)
- Coating thickness measurement (total ≥ 100 μm, DFT gauge)
- Hydraulic pressure test at 240 bar with documented results
- Final dimensional inspection and visual check
- Serial number traceability per unit
Standards Reference
| Domain | Standard |
|---|---|
| Cylinder tube material | EN 10297-1: E355 |
| Piston rod material | EN 10083-2: C45 / 1.0503 |
| Material certificates | EN 10204 Type 3.1 |
| General tolerances | ISO 2768-mK |
| Hydraulic cylinder testing | ISO 10100 |
| Surface preparation | ISO 8501-1 Sa 2.5 |
| Colour | RAL 7035 |
| Completed | 2026 |
