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Directional Valves

Directional valves start, stop and control the direction of fluid flow.

They work to cause the reverse motion of a cylinder or hydraulic motor (4 way valve), to pressurize and exhaust an actuator port (3 way valve or 4 way with plugged actuator port). As an ON-OFF function - used as safety interlock and to isolate and connect various system parts (2 Way), to prevent reverse flow (one way valve).

By moving an internal flow control source in a particular way, a directional valve allows fluid to flow through a passage. The control source could be a poppet (either piston or ball) a rotary or sliding spool. The control source can be moved manually, mechanically, pneumatically, hydraulically, electrically or certain combinations of each.

The flow direction can be one-way (as in a check valve, using a ball to stop reverse flow), two way, three way, or four way. They are sized according to the size of the port or flange connections, rated gallons per minute or with reference to a standard mounting pattern.

Control valves are valves used to control conditions such as flow, pressure, temperature, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "set point" to a "process variable" whose value is provided by sensors that monitor changes in such conditions.[1]

The opening or closing of control valves is usually done automatically by electrical, hydraulic or pneumatic actuators. Positioners are used to control the opening or closing of the actuator based on electric or pneumatic signals. These control signals, traditionally based on 3-15psi (0.2-1.0bar), more common now are 4-20mA signals for industry, 0-10V for HVAC systems, and the introduction of "Smart" systems, HART, Fieldbus Foundation, and Profibus being the more common protocols.

Repair Procedures:

  • Replace all dry coils with new dry coils.
  • Replace spool as necessary.
  • Replace solenoid assemblies.
  • Sandblast, tumble and clean all solenoid cores.
  • Install new ends to coil wires.

Brands We Repair:

  • Bosch
  • Vickers