1. PRESSURE CONTROL CARTRIDGE VALVES
Product Overview
© 2008 Sun Hydraulics Corporation

2. Pressure Controls Relief Sequence Reducing Reducing/Relieving
© 2008 Sun Hydraulics Corporation

3. Pressure Controls - Relief
Normally closed devices used to limit or regulate pressure
Many variations to meet application requirements
Available in 2, 3, and 4 port configurations
Used to protect pumps or actuators, or maintain constant system pressure
All hydraulic systems feature at least one relief valve
© 2008 Sun Hydraulics Corporation

4. Relief Valve – Technical Overview
RP*C, Pilot Operated, Balanced Piston Relief
Accurate pressure control
Low pressure rise with flow
Smooth and quiet
Moderately fast response time
Viscosity sensitive
Susceptible to silting
© 2008 Sun Hydraulics Corporation

5. Relief Valve – Technical Overview
RD*A, Direct Acting Relief
Differential area design
Typically smooth and quiet performance
Essentially zero leak (suitable for load holding)
Dirt tolerant
Very fast response
Difficult to adjust under pressure
Higher pressure rise with flow
© 2008 Sun Hydraulics Corporation

6. Relief Valve – Technical Overview
Advantages
Relief Valve Comparison
Direct Acting
Relief Valves
Pilot Operated
Relief Valves
(Sliding Spool)
Fast response
Low leakage
Dirt tolerant
Capable of operating over a wide temperature range
Low over/undershoot
Common flow path with P/O design
Wide pressure range
Low hysteresis
Easier to adjust when operating at high pressures
Low override curve
Screened orifice
Common flow path with direct acting 2 1
Port 1 - Inlet
Port 2 - Outlet 2 1
Port 1 - Inlet
Port 2 - Outlet
© 2008 Sun Hydraulics Corporation

7. Relief Valve – Technical Overview
Disadvantages
Relief Valve Comparison
Direct Acting
Relief Valves
Pilot Operated
Relief Valves
(Sliding Spool)
Moderate hysteresis levels (not equivalent to P/O versions)
Moderate pressure override
Multiple spring ranges required to optimize performance
Difficult to adjust when operating at high pressures
Higher overshoot/undershoot potential
Internal leakage when closed
Temperature limitation
Contaminant sensitive in dirty systems 2 1
Port 1 - Inlet
Port 2 - Outlet 2 1
Port 1 - Inlet
Port 2 - Outlet
© 2008 Sun Hydraulics Corporation

8. Relief Valve – Technical Overview
RP*S, Pilot Operated, Balanced Poppet Relief
Combines features of pilot operated and direct acting relief valves
Smooth and quiet pressure regulation
Very low leakage
Dirt tolerant
Adjustable under pressure
Very fast response
Eliminates erosion cavity damage
© 2008 Sun Hydraulics Corporation

9. Relief Valve – Technical Overview
RBA*, Direct Acting, Pilot Stage Relief
Remotely controls pressure setting of other pilot operated valves
Capacity limited to pilot flow—should only be used with valves with comparable pilot flows
Fast response
© 2008 Sun Hydraulics Corporation

10. Relief Valve – Technical Overview
RPGT, Pilot Operated, Balanced Poppet, Soft Relief
Pilot-operated relief that limits maximum system pressure and also the rate of pressure rise
Adjust screw determines the maximum setting and an initial (threshold) setting
Valve opens at threshold and ramps closed (or to maximum setting) at a constant rate in about 250 ms
Controlled rate of rise results in less dynamic stress in a system and no pressure spikes
© 2008 Sun Hydraulics Corporation

11. Relief Valve – Technical Overview
Soft Relief Function
© 2008 Sun Hydraulics Corporation

12. Relief Valve – Technical Overview
Relief Valve Response Comparison
Ultimate Pressure
System Designed Maximum Pressure
System Designed Maximum Pressure and Ultimate Pressure
Threshold Pressure
© 2008 Sun Hydraulics Corporation

13. Relief Valve – Technical Overview
RV*A, Ventable, Pilot Operated, Balanced Piston Relief
Essentially a pilot-operated relief valve with a vent port that connects between the main piston and pilot stage
Vent provides for remote control with other pilot or two-way valves by short circuiting the pilot stage
If port 3 is blocked – valve operates as a standard relief If port 3 is open to tank – main section is wide open
Same general characteristics as a pilot-operated relief valve
© 2008 Sun Hydraulics Corporation

14. Relief Valve – Technical Overview
RV*D, Ventable, Pilot Operated, Balanced Piston Relief with External Drain
Same as the RV*A valve except with a separate drain for the pilot stage
Valve is insensitive to back pressure at port 2
Can be thought of as a ventable sequence valve
Same general characteristics as a pilot-operated relief valve
© 2008 Sun Hydraulics Corporation

15. Relief Valve – Technical Overview
RQ*B, Pilot Operated, Kick-down Relief
Act similar to a circuit breaker in an electrical system
When pressure at the inlet reaches the valve setting, valve kicks completely open
Valve remains open as long as pressure at port 1 exceeds pressure at port 2
To reset valve flow must cease
Same general characteristics as a pilot operated relief valve
© 2008 Sun Hydraulics Corporation

16. Pressure Controls - Sequence
Normally closed devices used to control a sequence of actions (similar to a relief valve with separate drain line)
Supplies flow to a secondary circuit once the pressure at port 1 exceeds the setting of the valve
Can be used as a relief if back pressure is present in system
Assures that a priority function is completed before a secondary function begins
Insures a part is clamped before machining can begin
Insures a clam shell bucket is closed before it can be lifted
© 2008 Sun Hydraulics Corporation

17. Sequence Valve – Technical Overview
SX*A, Direct Acting Sequence
Similar construction to the RD relief valve
Setting of valve controls the pressure at port 1 relative to drain pressure at port 3
Extremely low leakage – suitable for load holding
© 2008 Sun Hydraulics Corporation

18. Sequence Valve – Technical Overview
SC*A, Direct Acting with Reverse Flow Check Sequence
Similar construction to the RD relief valve
Setting of valve controls the pressure at port 1 relative to drain pressure at port 3
Extremely low leakage – suitable for load holding
Incorporates an integral check valve to provide reverse flow from port 2 (sequence) to port 1 (inlet).
© 2008 Sun Hydraulics Corporation

19. Sequence Valve – Technical Overview
RS*C, Pilot Operated, Balanced Piston Sequence
Similar construction to the RP relief valve
Setting of valve controls the pressure at port 1 relative to drain pressure at port 3
Insensitive to back pressure at port 2 – can be used to regulate pressure in place of a two port relief valve if there is pressure in the return line
© 2008 Sun Hydraulics Corporation

20. Sequence Valve – Technical Overview
RS*E, Air Controlled, Pilot Operated,
Balanced Piston Sequence
Similar to the RS*C expect this version uses compressed air over a diaphragm instead of an adjustable spring to control the pressure setting
Air supplied in hex end of cartridge
Hydraulic setting is directly proportional to air pressure at ratio of 20:1 (hydraulic:air)
Maximum air pilot pressure should not exceed 150 psi
© 2008 Sun Hydraulics Corporation

21. Sequence Valve – Technical Overview
SQ*B, Kick-down Sequence
Two
One
Note:
Pressure to
cylinder 1 drops
to a low pressure
after valve shifts
Similar to the RQ*B in construction and function
When pressure at the inlet reaches the valve setting, valve kicks completely open
Valve remains open as long as pressure at port 1 exceeds pressure at port 2
To reset valve flow must cease
Valve setting is insensitive to back pressure at port 2
© 2008 Sun Hydraulics Corporation

22. Pressure Controls – Reducing
Normally open, modulating device used to control the pressure of a secondary circuit to a pressure below the main system pressure
Different variations to meet application requirements
Used in many industrial applications
Maintain a lower constant clamping pressure on a part when a higher pressure is needed for other functions in the circuit
© 2008 Sun Hydraulics Corporation

23. Reducing Valve – Technical Overview
PB*B, Pilot Operating Reducing
System 1
System 2
Port 2 inlet
Exceptionally flat pressure vs. flow characteristic
Reverse flow from port 1 to port 2 may cause the valve to completely shut – use a separate check for reverse free flow
If pilot flow consumption is critical, use a direct acting reducer/reliever
© 2008 Sun Hydraulics Corporation

24. Reducing Valve – Technical Overview
PR*R, Direct Acting Reducing
Available in Series 1 through 4
Port 2 inlet
Can be used as an adjustable restrictive compensator
Damped construction provides more stable operation
© 2008 Sun Hydraulics Corporation

25. Pressure Control - Reducing/Relieving
Normally open, modulating devices that incorporate the relief function with the reducing function
3 and 4 port configuration
Under a backflow condition, valve relieves pressure at port 1 through port 3 when relief setting is met (need full capacity at port 3)
Provides a controlled pressure and a constant counterbalancing force for bi-directional elements
© 2008 Sun Hydraulics Corporation

26. Reducing/Relieving Valve – Technical Overview
PP*B, Pilot Operated Reducing/Relieving
Similar to reducing valve with integral relief from port 1 to port 3
Exceptionally flat pressure vs. flow characteristic
Reverse flow from port 1 to port 2 may cause the valve to completely shut – use a separate check for reverse free flow
If pilot flow consumption is critical, use a direct acting reducer/reliever
© 2008 Sun Hydraulics Corporation

27. Reducing/Relieving Valve -- Technical Overview
PR*B, Direct Acting Reducing/Relieving
Same function as PP*B with superior dynamic response
Suitable for accumulator circuits since the absence of pilot flow results in less secondary circuit leakage
Provides highly reliable performance in contaminated systems or in dead head conditions
Exhibit a transitional step between reducing and relieving—may not be suitable for counterbalancing
© 2008 Sun Hydraulics Corporation

28. Reducing/Relieving Valve – Technical Overview
Advantages
Reducing/Relieving Valve Comparison
Direct Acting
Reducing/Relieving Valves
Pilot Operated
Reducing/Relieving Valves
(Sliding Spool)
Fast response
Low pilot flow
Dirt tolerant
Capable of operating over a wide temperature range
Low hysteresis
Common flow path with P/O design
Damped construction
Wide pressure range
Low hysteresis
Low override curve
Screened orifice
Common flow path with direct acting
Low dead-band transition between reducing and relieving
Stable performance 3 2 1
Port 1 - Reduced
Port 2 - Inlet
Port 3 - Tank 1 3 2
Port 1 - Reduced
Port 2 - Inlet
Port 3 - Tank
© 2008 Sun Hydraulics Corporation

29. Reducing/Relieving Valve – Technical Overview
Disadvantages
Reducing/Relieving Valve Comparison
Direct Acting
Reducing/Relieving Valves
Pilot Operated
Reducing/Relieving Valves
(Sliding Spool)
Steep regulation curve
High dead-band transition between reducing and relieving
Multiple spring ranges required to optimize performance
Poor response time
Constant pilot flow when operating
Contaminant sensitive in dirty systems 3 2 1
Port 1 - Reduced
Port 2 - Inlet
Port 3 - Tank 1 3 2
Port 1 - Reduced
Port 2 - Inlet
Port 3 - Tank
© 2008 Sun Hydraulics Corporation

30. Reducing/Relieving Valve - Technical Overview
PV*A, Pilot Operated Reducing/Relieving, Externally Drained
Special version of pilot-operated reducing/relieving valve that is insensitive to pressure at port 3
Pressure at port 4 is directly additive to the valve setting
By controlling pressure at port 4, the effective setting of the valve can be increased over the valve setting
© 2008 Sun Hydraulics Corporation

31. Reducing/Relieving Valve - Technical Overview
PV*B, Pilot Operated Reducing/Relieving, Ventable
Special version of pilot operated reducing/relieving valve that is ventable at port 4
Pressure at port 3 is directly additive to the valve setting
By controlling pressure at port 4, the effective setting of the valve can be controlled below the valve setting
© 2008 Sun Hydraulics Corporation