Over-center valves type LHT
with oscillation damping
D 7918
Over-center valve type LHT
March 2004-12© 1999 by HAWE Hydraulik
HAWE HYDRAULIK SE
STREITFELDSTR. 25 • 81673 MÜNCHEN
2.3
1. General information
Flow rate Q
max
= 250 lpm
Operation pressure p
max
= 450 bar
See also:
o Over-center valve type LHK acc. to D 7100
o Over-center valve type LHDV acc. to D 7770
These over-center valves are throttle valves which are commonly used for a well controlled movement of loads connected to
double acting hydraulic consumers (lifting and swivel cylinders). They prevent a collapse or eventual rupture of the fluid column. The
velocity is determined by the flow to the consumer.
With dragging loads the flow out of the consumer is throttled in such a way that the pump, feeding the contrary side, always has to
overcome a slight back pressure.
This back pressure is caused by a spring which usually is set about 15% higher than the respective maximum load induced pressure
for the device enabling compensation of dynamic forces.
These valves can be customized to suit most applications by employing orifices of various diameter at the in- and outflow of the
control line that influence the release ratio as well as the dampening characteristic. Special dampening elements like with type LHDV
(D 7770) are only used at type LHTZ. Their use is most advantageous at applications where the dampening characteristic of type
LHK (D 7100) is not sufficient, i.e. applications, which are less prone to low frequent oscillations like nodding etc.
The valve is zero leakage in unoperated state. All of these valves, beside valves with geometric release ratio 1 : ), perform also
as a safety valve. At valves with release ratio 1 : ) (line rupture safety valves), the control pressure is independent of the load
pressure. Therefore a shock valve installed as option in the valve body is necessary to safe guard eventual pressure surges or
creeping pressure rise on the consumer side.
When the load is dropped via pressure at the opposing side this pressure will also enter the control line and open-up the outflow
side i.e. only the design related back pressure valve will be effective.
o Design versions:
- Pipe connection (tapped ports or SAE-flange)
- for manifold mounting
- as banjo bolt
- for screwing-in
o Versions:
- double acting cylinders with control line (coding 11)
- double acting cylinders, ports of the opposite side in the block, minimized piping effort (coding 14)
- with additional shock valve enabling quick removal of pressure peaks (coding 15)
- with additional port enabling connection of a second, double acting consumer being operated in parallel (making a second
over-center valve superfluous; coding 18)
- Circuitry for winches with integrated loose rope prevention (coding 17)
- Circuitry for double acting cylinders and alternating load directions (coding 21, 23, 25)
Version for
screwing-in
Version for direct pipe
connection
Version for manifold
mounting
Banjo bolt version
D 7918 page 2
Geometric release ratio
n
geo
. 1 : )
Geometric release ratio
n
geo
= 1 : )
2
)
Effective
load
pressure
Without
influence
of the load
pressure
Footnotes
1
)
2
)
3
) see page 3!
Table 1:
Connection manner:
E = Cartridge valve (The inflow and the optional outflow orifice
must be integrated somewhere else in the manifold!)
H = With banjo bolt
G = For pipe connection conf. ISO 228/1 (BSPP)
P = For manifold mounting (only port V is housed in the manifold)
SAE = For SAE connection flange
OMT = For direct mounting onto motors type OMT (Co. DANFOSS)
OMP = For direct mounting onto motors type OMP or OMR
(Co. DANFOSS)
Symbol
2. Available versions, main data
Order examples:
LHT 50 G -15-8- A 6-300/280
LHT 50 SAE -11-6- C 6-80
LHT 3 E B 7-400
LHT 21 H -14 B 4-350
LHT 33 OMP -21 A 7-250 -B 7-250
Individual valve for pipe connection
Individual valve with SAE connection flange
Cartridge valve
Version for banjo bolt mounting
Double valve for sub-plate mounting
Shock pressure (bar)
(only at symbol -15, -23, -25)
Load pressure (bar)
(or release pressure with n
geo
= 1 : ))
Outflow
orifice D2
see table 2,
page 3
4
8
1 : 4
1 : 8
20 ... 60
61 ... 250
251 ... 400
D2 = 0
9 ... 14
15 ... 25
26 ... 40
41 ... 65
66 ... 90
D2 = 6
24 ... 43
46 ... 123
250 ... 310
Basic type, size, connec-
tion manner and symbols
Size 2 28 14 10 6 3 --
Size 3 130 85 55 35 20 10
Size 5 250 200 150 100 50 25250 200 150 100 50 25250 200 150 100 50 25
130 85 55 35 20 10
130 85 55 -- -- --
Flow coding
A B C D E F
LHT 21 G -11
LHT 21 P -11
LHT 21 P -14
LHT 21 UNF P -14
LHT 21 H -14
LHT 22 G -11
LHT 22 P -11
LHT 23 SAE -25W
20 ... 49
50 ... 199
200 ... 319(400)
3
)
from 320
LHT 33 G -11
LHT 33 P -11
LHT 33 P -15
LHT 33 OMT -17E
LHT 33 SAE -18
3
)
LHT 33 OMP -21
LHT 34 G -15
LHTZ 30 P -23
LHTZ 33 P -15
LHT 3 E
1
)
20 ... 89
90 ... 259
260 ... 450(400)
3
)
Geometric release ratio n
geo
7 1 : 7
1 : )
2
)
4
7
10
1 : 4
1 : 7
1 : 10
0
D2 = 0
15 ... 30
31 ... 70
71 ... 100
D2 = 6
46 ... 90
95 ... 215
216 ... 305
6 1 : 6 0
1 : )
2
)
Pressure ranges shock valves:
Basic type Pressure
range (bar)
LHT 23 SAE-25W 90 ... 160
161 ... 220
221 ... 340
LHT 33 P-15
LHTZ 33 P-15
LHTZ 30 P-23
LHT 34 G-15 150 ... 250
251 ... 340
LHT 50 ...-15 20 ... 160
161 ... 450
20 ... 160
161 ... 400
Flow rating (lpm)
with |p
VdF
of approx. 40 bar
Also avail. coding AB, flow rating = 20 lpm
(see |p-Q-curve in sect. 3)
Flow rating (lpm)
with |p
VdF
of approx. 40 bar
Flow rating (lpm)
with |p
VdF
of approx. 40 bar
Flow rating (lpm)
with |p
VdF
of approx. 40 bar
Pressure range (bar)
1
)
Pressure range (bar)
1
)
Pressure range (bar)
1
) 20 ... 200
201 ... 400
Release pressure
Pressure range (bar) Release pressure
LHT 50 G -11
LHT 50 SAE -11
3
)
LHT 50 SAE -14
3
)
LHT 50 G -15
LHT 50 SAE -15
3
)
D 7918 page 3
1
)
Symbols
Basic valve (illustrated for geom. release ratio n
geo
. 1 : ))
1
) Type LHT 2..., LHT 33 OMT(OMP) and LHT 3E only with geom. release ratio n
geo
(no outflow orifice D2)
2
) Notes regarding geom. release ratio n
geo
= 1 : )
- This valve version does not show a safety valve function, as the load pressure is not applied (see symbol)
- The set release pressure p
contr
directly corresponds to the necessary pressure at port S to open the valve.
- The functionality is like with a line rupture safety valve.
- Attention: The use of an outflow orifice D2 (acc. to table 2) will dampen oscillations but will raise the required pressure
at port S (see the various pressure ranges at table 1)
3
) p
max
is restricted for version with SAE hole pattern
4
) Prepared, the outflow port of the control line is plugged, corresponds to the geom. release ratio n
geo
5
) Set at 30 bar by HAWE (adjustable range 10 ... 50 bar)
Cartridge valve
LHT 3E
Valve
Manifold
LHT ...-11
LHTZ ...-15
LHT ...-18LHT ...-14
LHT 50 ...-15LHT 34 G ...-15
LHT ...-17E
LHT 23 SAE -25W LHTZ 30 P-23
Table 2: Effective release ratio n
real
, outflow orifice D2
Type LHT 2..., LHT 33 OMT(OMP) and LHT 3 E only with geom. release ratio n
geo
(no outflow orifice D2); With all other versions the effective release ratio n
real
i.e. the necessary
release pressure is determined by the orifice combination D1/D2
Examples: LHT 33 P11 - 6 - A7 - 200
n
geo
= 1: 7, n
real
= 1 : 2.28
LHT 33 P11 - 0 - A7 - 200
n
geo
= n
real
= 1 : 7
A release pressure p
contr
of approx. 90 bar is necessary
(without effective load pressure)
A release pressure p
contr
of approx. 30 bar is necessary
Coding
Orifice-# (mm)
Actual
(dynamic)
release ratio
with type
Note: Inflow orifice D1 #0.5 mm (standard, no coding).
4 5 6 (series) 7 8 0
4
)
0.4 0.5 0.6 0.7 0.8 --
LHT 3..-..4-... 1 : 2.84 1 : 2 1 : 1.30 1 : 0.83 1 : 0.53 1 : 4
LHT 3..-..7-... 1 : 4.96 1 : 3.5 1 : 2.28 1 : 1.45 1 : 0.93 1 : 7
LHT 5..-..6-... 1 : 4.26 1 : 3 1 : 1.95 1 : 1.24 1 : 0.79 1 : 6
Pre-load valve
type VR 3.C
(see also
page 9)
LHT 33 OMP-21
5
)
5
)
not apparent with size 2
D 7918 page 4
3. Additional parameters
Nomenclature Over-center valve with hydraulic release and bypass check valve
Design Over-center valve: cone seated valve
Bypass check valve: plate seated valve
Installed position Any
Ports F, V, V1, V2, A, B and R Main ports
M, S and Z Control and pick-up ports dep. on type
Mass (weight)
approx. kg
Flow direction Operation direction (load holding function) V d F, V1 d F or V2 d F
Free flow F d V, F d V1, F d V2
Release ratio Blocked valve approx. 1 : 4, 1 : 7, 1 : 8, 1 : 6 dep. on basic type
Opened (released) valve approx. 1 : 1 to 1 : 5 dep. on orifice-#-ratio and basic type see sect. 2
Pressure adjustment A pressure gauge should be used whenever the pressure setting is adjusted or altered! The given figures
for pressure alternation per rotation and per mm adjustment travel of the perforated disc (within the
connector F) or of the set screw (at the spring housing) are only a rough guide line for approximately
achieving the desired setting (start of operation). The setting should be at least 15% above the max.
expected load pressure.
Over-center valve function (n
geo
= 1 : 4; 1 : 8; 1 : 7; 1 : 6)
Line rupture safety valve function (n
geo
= 1 : ))
; Slacken the Both grub screw
or SEAL-LOCK nut which serve
for locking < and must be
slackened prior to any pressure
adjustment
< The perforated disc can be
rotated with an allan key a/f 6
(mm), the set screw with a screw
driver
= pressure increases
= pressure decreases
= Retighten the grub screw /
SEAL-LOCK nut ; after per-
formed adjustment.
This bypass-throttle valve is a must with test rigs using a motor pump!
The pump should be circulating via opened throttle valve, then close the
throttle valve slowly until LHT starts barely responding (avoid larger flow
since the valve might squeal).
Attention: The pump has to be connected to port S with geom. release
ratio n
geo
= 1 : ) !
LHT 33 G(P) -11 = 1.3
LHT(Z) 33 P -15 = 1.7
LHT 33 SAE -18 = 2.4
LHT 33 OMT -17E = 2.4
LHT 33 OMP -21 = 2.8
LHT 34 G -15 = 2.2
LHTZ 30 P -23 = 5.0
LHT 50 G -11 = 2.4
LHT 50 SAE -11 = 3.0
LHT 50 G -15 = 3.2
LHT 50 SAE -14(15) = 3.9
LHT 21 H -14 = 0.6
LHT 21(22) G(P) -11 = 0.8
LHT 21 (UNF)P -14 = 1.0
LHT 23 SAE -25W = 3.2
LHT 3 E = 0.6
Test bench
with hand
pump
Type
LHT 50..
Pressure
gauge
Type
Spring (pressure p
max
bar)
Pressure alternation (bar/rev.)
Pressure alternation (bar/mm)
LHT 23..-25..
340 220 160
-- -- --
40 27 17
LHT 33 P-15..
400 160
100 19
-- --
LHT 34 G-15..
340 250
-- --
66 40
LHT 5..-15..
450 160
80 17.5
-- --
TypePressure alterations
(over-center valve)
Pressure alterations
(shock valve)
LHT 2
1 : 4
1 : 8
1 : 4
1 : 7
LHT 3
1 : 7
1 : )
1 : 6
1 : )
LHT 3 E
LHT 5
Pressure variation per mm
according to pressure range |p
Spring
(bar/mm)
0 ... 60 bar 61 ... 250 bar 251 ... 400 bar
24 41 124
49 85 255
--- 0 ... 200 bar 201 ... 400 bar
--- 16 30
--- 30 40
20 ... 42 bar 50 ... 199 bar 200 ... 318 bar
18 30 40
9 ... 14 bar 26 ... 40 bar 41 ... 65 bar
1 3 13
20 ... 89 bar 90 ... 259 bar 260 ... 450 bar
14 27 29
15 ... 30 bar 31 ... 70 bar 71 ... 100 bar
3 5 6
Pressure variation per turn
|p
set
(bar/U) = k · |p
Spring
n
geo
k = 1.34
k = 1.25 (only LHT 21 (UNF) P 14)
k = 1.81
k = 1.25 (only LHTZ 30 P 23)
k = 1.25
< ;= ; <=
D 7918 page 5
|p-Q-curves Operation direction V d F (depending on the flow size, acc. to table 1 in sect. 2)
Free flow F d V (characteristic back pressure)
Fluid viscosity during tests approx. 50 mm
2
/s
Back pressure |p (bar)Back pressure |p (bar)Back pressure |p (bar)
Flow rate Q (lpm)
Flow rate Q (lpm)
Type LHT 2..
Type LHT 3..
Type LHT 50..
Flow rate Q (lpm)
Functional restriction The use of these is restricted when combined with directional valves enabling
differential circuitry during any switching position e.g. coding C of D 5700.
Valves intended for one load direction only (symbols 11 to 18) must not be
connected to the rod side of hydraulic cylinders.
Hydraulic fluid Fluids acc. to DIN 51524 table 1 to 3; ISO VG 10 to 68 acc. to DIN 51519
Viscosity range: min. approx. 4; max. approx. 1500 mm
2
/s
Optimal operation range: approx. 10...500 mm
2
/s
Also suitable are biologically degradable pressure fluids of the type HEPG (Polyalkylenglycol) and
HEES (synth. Ester) at operation temperatures up to approx. +70°C.
Temperature Ambient: approx. -40...+80°C
Fluid: -25...+80°C, pay attention to the viscosity range!
Start temperature down to -40°C are allowable (Pay attention to the viscosity range during
start!), as long as the operation temperature during subsequent running is at least 20K higher.
Biological degradable pressure fluids: Pay attention to manufacturer‘s information. With regard to the
compatibility with sealing materials do not exceed +70°C.
Continuation: Additional parameters
D 7918 page 6
4. Unit dimensions All dimensions in mm, subject to change without notice!
4.1 Basic valves
Type LHT 21 H-14
Type LHT 21 P-11
LHT 22 P-11
Type LHT 21 G-11
LHT 22 G-11
Type LHT 21 P-14
LHT 21 UNF P-14
Ports conforming ISO 228/1 (BSPP):
A, B, F, V = G 1/4
2
) Both, the seal ring and the spot
face show the same diameter.
Ports conforming
ISO 228/1 (BSPP):
LHT 21 V, F = G 1/4; S = G 1/4
LHT 22 V, F = G 3/8; S = G 1/4
2
)
Seal ring
KDS-1/4 A3C
a/f 5
a/f 22
Torque 30 Nm
O-rings
4.47x1.78 NBR 90 Sh
Hole pattern of the manifold
(top view)
Hole pattern of the manifold
(top view)
1
)
1
)
1
)
M6, 10 deep
M6, 10 deep
M6, 10 deep
Skt.-head screw
ISO 4762-M6x40-8.8-A2K
Skt.-head screw
ISO 4762-M6x40-8.8-A2K
a/f 10
a/f 10
1
) Attention:
The hexagonal spring housing must be
countered while installing the pipe fitting !
Torque 30 Nm
d
1
= max. #5
d
2
= max. #3
d = max. #4
a/f 22
Torque 30 Nm
a/f 22
Torque 30 Nm
Ports
LHT 21P-14: A, F = G 1/4 (ISO 228/1 (BSPP))
LHT 21 UNF P-14: A, F = 9/16-18 UNF-2B (SAE J 514)
O-rings
V = 6.02x2.62 NBR 90 Sh
S = 3.7x1.78 NBR 90 Sh
D 7918 page 7
Type LHT 23 SAE-25W
Type LHT 33 G-11
O-ring 20.29x2.62
NBR 90 Sh
Skt.-head screw
DIN 912 3/8”-16x2.75”
Ports conforming
ISO 228/1 (BSPP):
F1, F2 = G 1/2
W = G 1/4
M1, M2 = G 1/4
S1, S2 = G 1/8
d
V1,
V2
= max. #17 mm
Ports conforming ISO 228/1 (BSPP):
F, V = G 1/2
S = G 1/4
a/f 30
Torque 180 Nm
1
)
1
) Attention:
The hexagonal spring housing must be
countered while installing the pipe fitting!
3/8”-16, 12 deep
Hole pattern of the manifold (top view)
D 7918 page 8
Ports conforming ISO 228/1 (BSPP):
F = G 1/2
M, S, Z = G 1/4
R = G 3/8
O-ring 12.37x2.62
NBR 90 Sh
M6, 12 deep
a/f 10Type LHT 33 P-15
Hole pattern of the
manifold (top view)
1
)
a/f 24
Torque 50 Nm
a/f 30
Torque 180 Nm
1
) Attention:
The hexagonal spring housing must be
countered while installing the pipe fitting!
Skt.-head screw
ISO 4762-M6x50-8.8-A2K
Ports conforming
ISO 228/1 (BSPP):
F = G 1/2
M, S, Z = G 1/4
M6, 12 deep
O-ring 12.37x2.62
NBR 90 Sh
a/f 10
Type LHT 33 P-11
Hole pattern of the
manifold (top view)
1
)
a/f 30
Torque 180 Nm
Skt.-head screw
ISO 4762-M6x50-8.8-A2K
D 7918 page 9
Type LHT 33 OMT-17E
Ports conforming ISO 228/1 (BSPP):
F = G 1/2
M = G 1/4
Flange for connection to motor
a/f 30
Torque 180 Nm
M10, 12 deep
1
)
Skt.-head screw
ISO 4762-M10x50-8.8-A2K
A sequence valve
type VR 33C acc. to D 7340
can be screwed into port B
Ports conforming
ISO 228/1 (BSPP):
M, S, Z = G 1/4
F, V2 = G 1/2
a/f 10
Flange enabling pipe connection at V1
SAE 1/2” (6000 psi)
M8,
Thru-hole
Type LHT 33 SAE-18
Connection side for
SAE flange 1/2” (6000 psi)
Skt.-head screw
ISO 4762-
M8x75-8.8-A2K
1
)
O-ring
12.37x2.62 NBR 90 Sh
1
) Attention:
The hexagonal spring housing must be
countered while installing the pipe fitting!
d = max. #24
O-ring 26.64x2.62
NBR 90 Sh
D 7918 page 10
Type LHT 34 G-15
1
) Attention:
The hexagonal spring housing must be countered
while installing the pipe fitting !
2
) Port T is plugged with a grub screw ISO 4027-M4x5-
45H and a ball 3 mm DIN 5401 with all standard
versions.
A sealing via O-ring is not required.
a/f 30
Torque 180 Nm
1
)
Ports conforming ISO 228/1 (BSPP):
F = G 1/2
M, S, Z = G 1/4
R = G 3/8
Type LHTZ 33 P-15
O-ring 12.37x2.62
NBR 90 Sh
1
)
Hole pattern of the manifold
(top view)
a/f 30
Torque 180 Nm
a/f 24
Torque 50 Nm
M6, 12 deep
O-ring 4.47x1.78 NBR 90 Shore
(only required, if port T is not plugged)
2
)
d
1
= max. #10
d
2
= max. #4
Skt.-head screw
ISO 4762-M6x50-8.8-A2K
Ports conforming ISO 228/1 (BSPP):
F, V = G 1/2
A, B = G 3/4
M, R = G 1/4
Adjustment of the shock valve only
possible via washers (see sect. 3)
D 7918 page 11
Type LHTZ 30 P-23
Type LHT 33 OMP-21...
Hole pattern of the manifold (top view)
O-ring 12.37x2.62
NBR 90 Sh
Skt.-head screw
ISO 4762-M8x60-A2-70
Skt.-head screw
ISO 4762-M8x50-A2-70
Ports conforming
ISO 228/1 (BSPP):
S1, S2 = G 1/4
4 x
M8, 12 deep
d
F1,
F2,
V1,
V2,
R
= max. #10
Hole pattern of the manifold (top view)
4x
M8, 12 deep
d
V1,
V2
= max. #20
appox. 46.4
appox. 46.4
appox. 29
appox. 29
O-ring 23.47x2.62
NBR 80 Sh
a/f 30
Torque
180 Nm
Ports conforming
ISO 228/1 (BSPP):
F1, F2 = G 1/2
D 7918 page 12
Ports conforming
ISO 228/1 (BSPP):
F, V = G 1
M, S, Z = G 1/4
Flange enabling pipe connection at V
SAE 3/4” (6000 psi)
Type LHT 50 G-11
#8.5
Thru-hole
M10, 16
deep
Ports conforming
ISO 228/1 (BSPP):
M, S, Z = G 1/4
Type LHT 50 SAE-11
Connection side for
SAE flange 3/4”
(6000 psi)
Connection side for
SAE flange 3/4”
(6000 psi)
O-ring 25x3.53
NBR 90 Sh
Skt.-head screw
ISO 4762-
-M10x75-8.8-A2K
D 7918 page 13
Ports conforming ISO 228/1 (BSPP):
F, V = G 1
R = G 3/4
M, S, Z = G 1/4
Type LHT 50 G-15
Type LHT 50 SAE-14
#8.5
Thru-
hole
O-ring 25x3.53
NBR 90 Sh
Skt.-head screw
ISO 4762-M10x95-8.8-A2K
Ports conforming
ISO 228/1 (BSPP):
M, Z = G 1/4
Flange A, B, and F SAE 3/4” (6000 psi)
Flange enabling pipe connection at V
M10, 20 deep
appox. 81
D 7918 page 14
4.2 Cartridge valve Typ LHT 3E
Mounting hole
a/f 36
Torque 180 Nm
a/f 41
Torque 100 Nm
Port F = G 1/2 conforming ISO 228/1 (BSPP)
1
) Attention:
The hexagonal spring housing must be countered
while installing the pipe fitting !
1
)
Ports conforming
ISO 228/1 (BSPP):
M, S, Z = G 1/4
Spring housing
of the over-
center valve
Spring dome of
the shock valve
Flange enabling pipe connection at V SAE 3/4” (6000 psi)
Type LHT 50 SAE-15
O-ring 25x3.53 NBR 90 Sh
Connection
side for
SAE flange 3/4”
(6000 psi)
M10, 16 deep
Connection side for
SAE flange 3/4” (6000 psi)
Skt.-head screw
ISO 4762-
-M10x85-8.8-A2K
D 7918 page 15
5. Example circuit
Over-center valve
type LHT 33 SAE-18
Over-center valve
type LHT 33 P-15 -
- B4 - 325/300
Check valve
type RH 3
Proportional directional spool valve
type PSL 51/400 - 3 - H80/40/EA
- E4 - G 24
Proportional directional spool valve
type PSV 55S1/250 - 3 - J25/60 A100 F3 / EA
- E1 - G 24
