2/2 DIRECT. CONTR. FITTED SEAT VALVE
FOR WATER AND OIL HYDRAULICS

DN16 TO 200, OPERATING PRESSURES UP TO 320 BAR

 

  • Pilot-controlled seat valves
  • Pilot-control by means of own medium
  • Leakage-free sealing on valve seat
  • Force-controlled working piston
  • Smooth switching, no pressure shocks
  • Piston is extended to the outside, there fore visible piston position
  • Hydraulic or pneumatic operation possible
  • Hydraulic remote control possible
  • Actuation magnet protected against dirt and humidity
  • Wear parts are easy to access and fast to replace
  • Manual emergency operation
  • Stroke limitation possible to save separate throttle valves
  • Protection against accidental operation

The 2/2 directional control fitted seat valves are particularly suitble for HFA liquids and clear water up to operating pressures of 320 bar maximum.

The valves can be equipped with positive or negative pilot-conrol valves. In a de-energized condition, this results the main valve setting "valve closed" or "valve open". The valve switching periods can be influenced by fitted filter diaphragms or intermediate plate valves with fitted fine throttles located between pilotcontrol and main valve. In case of valves with larger nominal widths, valve switching periods can be significantly reduced by a double pilot-control system, e.g. pilot-control valve DN 6 with intermediate plate valve DN 9, DN 12, or DN 16.

Special features

Due to the hydraulic force-control by means of the different size control surfaces of the piston rods, the piston rods cannot flutter. Closing springs are not required, thus there can be no uncontrolled piston position in the event of any spring fracture. 

The valves are insensitive against vibrations and pressure surges in the hydraulic system.

Due to the extended piston guides, the pistons cannot be tilted by crossflow action. Depending on the version, the valves are kept closed by the applied system pressure. If the pilot-control medium or the electrical power fails, the valves will close. Therefore, uncontrolled load movements cannot occur.

The individual valve pistons are always extended to the outside; this causes the open or closed valve positions to be visible from the outside. There is the possibility for mounting limit switches onto the piston position indicator. Valves with stroke limitation feature appropriate bores for controlling the piston position within the stroke limitation housing.

All wear parts are easy to access and fast to replace.

 

For a flow direction from A to B, due to the special purpose design of the valve seats and the throttle cones on the pistons, the metallic sealing surfaces are largely insensitive against dirt. This also prevents the feared switching surges.

 

All valve components coming into contact with one another due to their movement are made of corrosion resistant materials. For aggressive media, the complete valve can be manufactured from appropriately selected special steels.

 

The pilot-control valves are made completely of stainless materials. The emergency manual controls fitted as standard can be arrested and are protected against accidental activation.

Building type
Fitted seat valve

Pilot-control pressure
=System pressure, min. 25 bar

Control medium
Own medium

Pressure liquid
HFA acc. to CETOP or VDMA standard sheet 24320 with 95% water and 5% additives. Non-lubricated water (clear water) Mineral oil acc. to DIN 51524 and 51525 phosphoric ester.

Pilot-control systems
see special brochures

Max. operating pressures
320 bar

Control medium return
Separate without pressure into tank

Flow
See table 1

Flow direction
To both sides from "A" to "B" and "B" to "A"

Liquid temperature
Main valve: coarse filtering
Pilot-control valve: 25-40µm

Self-closing 2/2 directional control fitted seat valve, force-controlled by internally supplied own medium

Valve de-energized=rest position (closed)
The control surface 6 of piston 5 is relieved as the control hamber 7 is relieved via pilot-control valve 1 and port "L". The working medium, applied at port "A", acts on control surface 9 of piston 5. At the same time, the working medium is applied to control chamber 3, via channel 7, and to the input of the closed pilotcontrol valve 1 and acts on the control surface 4 of piston 5. Due to the force difference occurring on control surfaces 4 and 9 (control surface 4 > control surface 9), piston 5 is pressed into valve seat 8 so that infeed "A" is blocked.

Valve de-energized=work position (open)
When pilot-control valve 1 is operated the passage to the control medium return line "L" is blocked, and the path from control chamber 3 to control chamber 7, via pilot-control valve 1, is released. The pressure of the control medium now acts additionally on the control surface 6 of piston 5. Due to the force difference occurring on the control surfaces 9, 6, and 4 (control surfaces 9 and 6 > control surface 4), piston 5 is lifted from valve seat 8 so that the path from infeed "A" to port "B" is now free. Every fitted valve can optionally be provided with a stroke limitation. Using adjuster screw 2, the stroke of piston 5 can be limited. Thus, there is the possibility to adapt the flow rate to the respective application situation. In the event of de-energization, the valve will close.

When mounting a negative pilot-control valve, the reversed main valve operating mode results. In the event of power failure the valve will open.

Valve de-energized = rest position (open)
The control chamber 3, to which pressure is applied, is connected to control chamber 7 via pilot-control valve 1. Due to the force difference occurring on the control surfaces 9, 6, and 4 of valve piston 5 (control surface 9 and 6 > control surface 4), piston 5 is lifted off valve seat 8. The path from "A" to "B" is clear.

Valve energized = working position (closed)
When operating pilot-control valve 1, control chamber 7 is vented via return line "L". The control surface 6 of piston 5 is relieved. Due to the force difference occurring on control surfaces 9 and 4 (control surface 4 > control surface 9) piston 5 is pressed into valve seat 8. Infeed "A" is blocked. In the event of power failure the valve will open.

Self-closing 2/2 directional control fitted seat valve, forcecontrolled by externally supplied own medium

In contrast to the valve construction type described at a the control medium is not removed from control chamber 3, but is fed into the pilot-control valve 1 externally, via port "Z". When operating the pilot-control valve 1, the path from port "Z" – via pilot-control valve 1 – direct into control chamber 7 is released, and the main valve opens. In the event of a power failure, or a control pressure collapse, the valve will close.

When using a negative pilot-control valve, the main valve operating mode reverses.

In the event of a power failure the valve will open, when the pilot-control pressure collapses the valve will close.

2/2 directional control fitted seat valve, closing and forcecontrolled by externally supplied own medium

Here to the operating mode of the main valve is the same as described at a. Only channel 10 in piston 5 does not exist. Therefore, control chamber 3 – like pilot-control valve 1 – is connected to the control port "Z", by means of which the control medium is externally supplied. In the event of power failure the valve closes; when the control pressure collapses, the valve opens.

When using a negative pilot-control valve, the main valve operating mode reverses.

When there is a power failure, or the control pressure collapses, the main valve opens.

Force-controlled 2/2 directional control fitted seat valve closingby means of an externally supplied own medium and a furtherexternally supplied control pressure.

The operating mode of this valve is the same as for the valve described at c. The difference between the two valves here consists in the double control pressure ports "Z" and "Z1" The pilot-control valve 1 is directly connected to the control port "Z"; control chamber 3, however, is connected to port "Z1". The control pressures on both ports are to be identical. When pilotcontrol valve 1 is operated, the path from port "Z" - via the pilotcontrol valve - directly to control chamber 7 is released, and the valve opens. For closing the valve, control pressure at port "Z1" is required.

In the event of power failure or a collapse of the control pressure at port "Z", the valve closes. When the control pressure at port "Z1" collapses, the valve opens.

When using a negative pilot-control valve, the main valve operating mode reverses. When there is a power failure, or the control pressure at port "Z1" collapses, the valve opens. If the control pressure at port "Z" collapses, the valve closes.

If the switching periods of the fitted seat valves are too short, single pilot-controls DN 6 can be selected instead of the double pilot-controls DN6/9. 

For the same reason, the double pilot-controls DN 6/16 can be constructed as DN 6/12.

for water (20°C) in 2/2 directional control fitted seat valves

Special features

Due to the hydraulic force-control by means of the different size control surfaces of the piston rods, the piston rods cannot flutter. Closing springs are not required, thus there can be no uncontrolled piston position in the event of any spring fracture. 

The valves are insensitive against vibrations and pressure surges in the hydraulic system.

Due to the extended piston guides, the pistons cannot be tilted by crossflow action. Depending on the version, the valves are kept closed by the applied system pressure. If the pilot-control medium or the electrical power fails, the valves will close. Therefore, uncontrolled load movements cannot occur.

The individual valve pistons are always extended to the outside; this causes the open or closed valve positions to be visible from the outside. There is the possibility for mounting limit switches onto the piston position indicator. Valves with stroke limitation feature appropriate bores for controlling the piston position within the stroke limitation housing.

All wear parts are easy to access and fast to replace.

For a flow direction from A to B, due to the special purpose design of the valve seats and the throttle cones on the pistons, the metallic sealing surfaces are largely insensitive against dirt. This also prevents the feared switching surges.

All valve components coming into contact with one another due to their movement are made of corrosion resistant materials. For aggressive media, the complete valve can be manufactured from appropriately selected special steels.

The pilot-control valves are made completely of stainless materials. The emergency manual controls fitted as standard can be arrested and are protected against accidental activation.