1
HA 5208
7/2008
M27 x 1,5 • p
max
350 bar • Q
max
90 L/min
Overcentre Valve
Fully Balanced
SOBD5A-R4/l
q
The valve prevents runaway in the event of a nega
-
tive load
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
1
2
3
4
Replaces
HA 5208 9/2006
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 =
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.
set up pressure – load pressure
ratio of control
Functional Description
2
HA 5208
Ordering Code
Technical Data
Cavity M27 x 1,5
Maximum flow L/min 90
Max. pressure bar 270
Max. input pressure bar 350
Pressure drops bar see Dp - Q characteristics
Hydraulic fluid Hydraulic oil (HM, HV) according to DIN 51524
Fluid temperature range °C -20 ... +90
Viscosity mm
2
/s 20 ... 400
Maximum degree of fluid contamination according to ISO 4406, Class 21/18/15
Weight kg 0,29
Maximum valve tightening torque
in valve body or in control block
Nm 60
+2
Mounting position Unrestricted
Dp-Q Characteristics Measured at n = 40 mm
2
/s
2
4
6
8
10
12
14
16
0 25 50 75 100
FREE FLOW
PILOT OPEN
30
60
90
120
150
180
210
240
0
0 6.5 13 19.5 26
0
Pressure p barD []
Flow Q L/min[]
Flow Q US GPM[]
Pressure p PSID []
SOBD5A-R4/l
Overcentre valve
Fully Balanced
Preassare range
Standard 4:1
4
Seals
No designation NBR
3
HA 5208
Dimensions Measurements in millimeters
Æ
Æ
4.00 MAX
Æ
Æ
Æ
Æ
Æ
Æ
Æ
Æ
Æ
Æ
Æ
Æ
Æ
3.30
3.05
29.00
33.50
55.00
29.30
29.20
67.00
30°
Æ
31.47
31.42
30°
1.00
30°
13.00
10.00
31.00
49.00
64.00
10.00 MAX
24.55
24.50
23.05
23.00
22.00
4.00 MAX
15°
M27x1.5-6H
45°
1.6
R 0.20
0.10
0.08
B
1.6
1.6
B
A
0.05
B
B
1.6
-A-
0.05
A
R 0.1 MAX
1.6
0.05
0.08
1.6
ST .00RUŽIT MIN. DO HL. 65
6HR5
6HR32
M27 x 1.5-6g
3
2
1
4
6HR17
HEX 5
HEX 17
HEX 32
Cavity Measurements in millimeters
4
HA 5208
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.
Seal kits on request.
Spare Parts
Subject to alteration without notice!
ARGO-HYTOS s.r.o. CZ - 543 15 Vrchlabí
Tel.: +420-499-403 111
E-mail: info.cz@argo-hytos.com
www.argo-hytos.com
