The WMM 6 series directional control valve is a manually operated, spool-type hydraulic valve designed for subplate mounting in accordance with ISO 4401-03-02-0-05 and DIN 24340 standards. Engineered for precise flow path control in industrial and mobile hydraulic circuits, the WMM 6 utilizes a robust mechanical lever mechanism to shift the internal spool, thereby directing fluid flow between ports P, A, B, and T. These valves are characterized by their high pressure-handling capabilities and modular versatility, making them suitable for pilot control or direct-acting applications where electrical actuation is either unavailable or unsuitable due to environmental constraints.
For complete selection guidelines and cross-reference documentation on this product line, please consult our industrial hydraulic valves catalog.
Mechanical Design and Operational Characteristics
The WMM 6 operates on the principle of a sliding spool within a precision-honed valve body. The spool geometry is engineered to minimize internal leakage through tight diametrical clearances, ensuring high volumetric efficiency. The manual lever assembly typically features a detent or spring-return mechanism, allowing for either momentary or maintained positioning of the spool.
When selecting a WMM 6 configuration, engineers must account for the pressure drop (Δp) versus flow (Q) characteristics, as the spool lands are designed to provide specific metering profiles. The valve body is constructed from high-strength cast iron, capable of withstanding system pressures up to 350 bar, provided the tank port (T) pressure remains within the limits defined by the specific seal configuration.
Technical Specifications
| Parameter | Specification |
|---|---|
| Mounting Pattern | ISO 4401-03-02-0-05 |
| Max Operating Pressure (P, A, B) | 350 bar |
| Max Tank Pressure (T) | 210 bar |
| Max Flow Rate | 60 L/min |
| Fluid Temperature Range | -30°C to +80°C |
| Viscosity Range | 10 to 800 mm²/s |
| Mounting Orientation | Optional |
Fluid Cleanliness and Filtration Requirements
The reliability of the WMM 6 is intrinsically linked to the fluid cleanliness levels maintained within the hydraulic circuit. Due to the precision fit between the spool and the valve bore, the valve is susceptible to “spool silting,” where fine particulate matter accumulates in the clearance gaps, leading to increased friction or mechanical jamming.
To ensure optimal service life, the hydraulic system must comply with ISO 4406 cleanliness class 20/18/15 or better. Filtration should be implemented at the pressure line (typically 10 µm absolute) to prevent the ingress of contaminants that could score the spool lands or compromise the integrity of the internal seals.
Seal Elastomer Compatibility
The WMM 6 is available with various seal materials to accommodate diverse operating environments and fluid types. The two primary options are Nitrile Butadiene Rubber (NBR) and Fluoroelastomer (FKM/Viton).
- NBR (Nitrile): The standard choice for mineral oil-based hydraulic fluids (HLP/HLPD). It offers excellent mechanical properties and cost-effectiveness within a temperature range of -30°C to +80°C.
- FKM (Viton): Recommended for applications involving synthetic fire-resistant fluids (e.g., HFD) or high-temperature environments. FKM provides superior chemical resistance and thermal stability, though it requires careful consideration of fluid compatibility to prevent premature hardening or swelling.
Users must ensure that the selected seal material is compatible with the specific additive package of the hydraulic fluid to prevent chemical degradation and subsequent external leakage.