Fluid Control Mechanisms: Hydraulic Valves & Filters

Understanding Hydraulic Valves

A hydraulic valve is a mechanism that serves to regulate fluid flow. While a special case of industrial valves, hydraulic valves possess unique characteristics that warrant separate consideration.

Hydraulic Valve Classification

The classification of valves used in hydraulic systems can be done according to the type of hydraulic work or application.

Classification by Hydraulic Work Type

• Discharge Valves: Such as Howell-Bunger valves, used for controlling outflow from reservoirs or dams.
• Energy Dissipating Valves: Designed to regulate flow into an outlet while dissipating excess energy.
• Turbine Inlet Valves: Valves specifically used to regulate the entry of water into a turbine section.

Common Hydraulic Valve Types

• Needle Valves: For precise flow control.
• Ball Valves: For quick shut-off and on-off control.
• Butterfly Valves: Lightweight and compact, used for isolation or regulation.
• Gate-Type Valves: For full flow or complete shut-off.
• Check Valves: Including ball type, foot valves, and disc check valves, which prevent backflow.

Valves in Specific Systems

• Aqueduct Valves: Used in water conveyance systems.
• Hydrant Valves: Employed in watering and fire suppression systems.

Hydraulic Filtration Systems

A hydraulic filter is a primary component of a hydraulic or lubricating oil filtration system. These systems are crucial for controlling pollution from solid particles, whether from external sources or internally generated by processes like wear or erosion of machine surfaces. Effective filtration preserves the lifespan of both machine components and the hydraulic fluid itself.

Types of Hydraulic Filters

Depending on the machine's structural complexity, its operating environment, and its importance within the production process, hydraulic filtration systems can incorporate filters of various designs and materials, strategically located at specific points within the machine.

Pressure Line Filters

Located in the high-pressure line, typically after the impeller or pump, these filters protect sensitive components like valves or actuators.

Return Filters

In a closed hydraulic circuit, return filters are situated in the fluid return line to the tank, operating at low pressure. They can be semi-submerged or fully submerged within the tank. These filters also help control dust generated by the friction of moving machinery parts.

Vent or Air Breathing Filters

Positioned at the equipment's vents, these filters limit the entry of airborne pollutants into the hydraulic system.

Recirculation Line Filters

Located off-line, often on the cooling line feeding the heat exchanger, these filters effectively remove accumulated solids from the hydraulic reservoir.

Suction Line Filters (Strainers)

Also known as strainers, these are placed immediately before the pump's impeller to protect the pump body from particle entry.

Filling Line Filters

Installed similarly to vent filters, at the tank's fluid entry point, these filters ensure that replacement hydraulic fluid is filtered, removing contaminants accumulated in the container or from a centralized filling system.