Document
Overcentre Valve
Fully Balanced
SOBD5A-R4/l
HA 5208 7/2008
M27 x 1,5 • pmax 350 bar • Qmax 90 L/min
q The valve prevents runaway in the event of a nega-
tive load
Replaces HA 5208 9/2006
q Load-holding with minimal leakage
q Pressure relief function protecting the actuator
against overload and pressure peaks
q When installed into the actuator the valve can be
used as a hose burst valve
q When used as pressure relief the check valve will
act as an anti-cavitation valve
q Relief setting is unaffected by back pressure q The valve should be mounted as close as possible
to the actuator
Functional Description
The valve consists of a seat by-pass, relief valve fitted with an auxiliary control with a differential piston and by-pass single-way valve serving for reverse direction of flow. The liquid is flowing through the single-way valve from the channel (2) to the channel (1) with a small pressure drop. In the opposite direction the single-way valve on the rear side of which a gate valve seat is fitted is pressed through the action of a spring and the load pressure against the spring-loaded valve gate valve. In this way the valve is nearly closed hermetically. If the pressure in the channel (1) exceeds a set up value of the spring force the gate valve is pressed out of the seat and the overpressure in that case is relieved into channel (2). For ensuring the function of holding the load the spring force should be set up to a value by 30 % higher when compared to an expected pressure exerted by
the load. If the load has to be moved it is possible to ensure it with the help of so called auxiliary control from the channel (3)
by introducing already certain control pressure. The control pressure is calculated in the following way:
Control pressure = set up pressure – load pressure ratio of control
The ratio of control designates a ratio of surfaces of the differential slide valve cross-section area and its seat. Therefore, the necessary control pressure for opening the valve does not correspond to the difference between
the set up pressure and load pressure however; it corresponds to the ratio of this difference and the control ratio. In the formula as mentioned above it is necessary to take into consideration that in differential cylinders it is necessary to add to the control ratio also the appropriate ratio of piston surfaces in the direction of movement. As soon as the control pressure attains a necessary value the differential gate valve is moved out from the seat and then the way from the channel (1) to the channel (2) is released. If now the load tries to accelerate and be fast as for the oil supply the supply pressure decreases, therefore, also the control pressure in the channel (3) is decreased. The spring force tries to shut off the valve again, therefore, in consequence of which the flow from the consumer decreases and the inlet pressure to the consumer increases again. In this way it is ensured a constant inlet pressure by means of which the movement of the load can be controlled. Dynamic pressures in the outlet do not influence the set up value thanks to a special arrangement of the slide valve. However, it is necessary to take care of the fact the control channel is independent on the dynamic pressure.
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ATVMEONSTFÉRA
1
1
HA 5208
Ordering Code
Overcentre valve Fully Balanced
SOBD5A-R4/l
Preassare range
Standard
4:1
4
No designation
Seals NBR
Technical Data
Cavity Maximum flow Max. pressure Max. input pressure Pressure drops Hydraulic fluid Fluid temperature range Viscosity Maximum degree of fluid contamination Weight Maximum valve tightening torque in valve body or in control block Mounting position
L/min bar bar bar
°C mm2 /s
kg Nm
M27 x 1,5 90 270 350
see Dp - Q characteristics Hydraulic oil (HM, HV) according to DIN 51524
-20 ... +90 20 ... 400 according to ISO 4406 (1999), Class 21/18/15
0,29
60+2
any
Pressure Dp [bar] Pressure Dp [PSI]
Dp-Q Characteristics
Measured at n = 40 mm2/s
0 16 14
12 10
8 6 4 2 0
0
Flow Q [US GPM] 6.5 13 19.5
26 240
210
FREE FLOW
180 150 120 90
PILOT OPEN
60 30
25 50 75 Flow Q [L/min]
0 100
2
Dimensions
Measurements in millimeters
HE6XHR55 HE6XH1R717
0.08 B 1.6
Cavity
HE6XH3R232
V4ENT
M27 x 1.5-6g M27 x 1.5-6g
3 2
1
Measurements in millimeters
Æ 0.05 B Æ 0.05 B
B Æ 0.08 A
Æ 31.47 Æ 31.42 Æ 29.30 Æ 29.20
15° 30°
M27x1.5-6H
1.6
1.6
R 0.20 0.10
45° 30°
R 0.1 MAX
Æ 4.00 MAX Æ 4.00 MAX 10.00
31.00 49.00
64.00
HA 5208
67.00 65.00 MIN REAM
55.00 33.50 29.00 3.30 3.05 13.00 1.00
30° 1.6
Æ 10.00 MAX
1.6 1.6
Æ 22.00
Æ 23.05 Æ 23.00
Æ 24.55 Æ 24.50
Æ 0.05 A -A-
3
HA 5208
Spare Parts
Seal kits on request.
Caution!
The packing foil is recyclable. The technical information regarding the product presented in this catalogue is for descriptive purposes only. It should
not be construed in any case as a guaranteed representation of the product properties in the sense of the law.
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