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
< ;= ; <=