Pressure Unloading Valve, Size 4
Q
max
= 30l/min,p
max
= 250bar
Two-stage, various on-off pressure differentials, with manual adjustment
Series DWPB-4N…
1/7
Reference: 400-P-379101-EN-01
Issue: 11.2020
S Compact construction for
cavity type AN – 3/4-16 UNF
S External pilot drain
S On-off differential independent of tank line pressure
S Choice of 5 on-off differentials
S 3 pressure ranges available
S With integral pressure-relief function
S Available with hand-knob
S All exposed parts with zinc-nickel plating
S Can be fitted in a line-mounting body
1 Description
Series DWPB-4N… cartridges are size 4, two stage, high
performance pressure-unloading valves with an 3/4-16
UNF mounting thread. They consist of a spool-type main
stage and a leak-free, ball-type pilot stage. Unloading val
ves are used wherever a pump has to be disconnected from
and re-connected to a pressure circuit. For this purpose, ei
ther the 'Off' pressure or the 'On' pressure of the cartridge
can be set. When the 'Off' pressure is set, the 'On' point will
depend on the selected percentage on-off differential, or the
other way round. To disconnect the pump, the cartridge re
sponds to rising pressures at ports 4 and 1 by opening the
connection from 4→3. This connection is then kept open
until the selected percentage on-off differential is reached
(falling pressure at port 1) and the connection 4→3 closes
again (the 'On' point). Because ports 2 and 3 are run back
to tank separately, the on-off differential (bar) is unaffected
by any back-pressure in port 3. These unloading valves are
predominantly used in accumulator-charging circuits,
2-pump systems, and circuits for fast-ad vance→feed
changeover, and in such cases the cartridges also provide
a pressure-relief function e.g. for protecting the pump (see
the application examples). All external parts of the cartridge
are zinc-nickel plated according to DIN EN ISO 19 598 and
are thus suitable for use in the harshest operating environ
ments. If you intend to manufacture your own cavities or are
designing a line-mounting installation, please refer to the
section “Related data sheets”.
2 Symbol
3
1
2
4
3 Technical data
General characteristics Description, value, unit
Designation pressure unloading cartridge valve
Design two-stage, with manual adjustment,
various on-off pressure differentials
Mounting method screw-in cartridge 3/4-16 UNF
Tightening torque 40Nm ± 10%
Size nominal size 4, cavity type AN
400-P-379101-EN-01/11.2020
DWPB-4N…
2/7
Description, value, unitGeneral characteristics
Weight 0.2 kg
Mounting attitude unrestricted
Ambient temperature range -25°C … +80°C
Hydraulic characteristics Description, value, unit
Maximum operating pressure 250bar
Maximum flow rate 30l/min
Nominal pressure ranges 04 = (10…40bar), 10 = (20…100bar), 25 = (50…250bar)
On-off differentials
1)
(on-off differential from 'Off' (unload) pressure)
8 … 12%
13 … 17%
17 … 23%
27 … 33%
37 … 43 %
Flow direction 4 → 3, see symbols
Hydraulic fluid HL and HLP mineral oil to DIN 51 524;
for other fluids, please contact BUCHER
Hydraulic fluid temperature range -25°C … +80°C
Viscosity range 10…650mm
2
/s (cSt), recommended 15...250mm
2
/s (cSt)
Minimum fluid cleanliness
Cleanliness class to ISO 4406:1999
class 20/18/15
4 Performance graphs measured with oil viscosity 33mm
2
/s (cSt)
Δp = f (Q) Pressure drop - Flow rate characteristic
(for unloaded bypass, valve open)
P0205.ai
0
1
2
3
4
5
6
7
8
Q [l/min]20 25 30151050
p [bar]
Δp = f (Q) Pressure drop - Flow rate characteristic
(pressure-relief function)
P0206.ai
0
50
100
150
200
250
Q [l/min]20 25 30151050
p [bar]
400-P-379101-EN-01/11.2020
DWPB-4N…
3/7
p = f (Q) Performance limits [250bar]
P0207.ai
0
50
100
150
200
250
Q [l/min]20 25 301510520
p [bar]
1)
2)
1)
On-off differential 8…12%
2)
On-off differential 13…17%
p = f (Q) Performance limits [250bar]
P0208.ai
0
50
100
150
200
250
Q [l/min]20 25 301510520
p [bar]
3)
3)
On-off differential 17…23%, 27…33% and
37…43%
p = f (Q) Performance limits [100bar]
P0209.ai
0
20
40
60
80
100
Q [l/min]20 25 301510520
p [bar]
4)
5)
4)
On-off differential 8…12%
5)
On-off differential 13…17% and 17…23%
p = f (Q) Performance limits [100bar]
P0210.ai
0
20
40
60
80
100
Q [l/min]20 25 301510520
p [bar]
6)
6)
On-off differential 27…33% and 37…43%
p = f (Q) Performance limits [40bar]
P0211.ai
0
10
20
30
40
Q [l/min]20 25 30151050
p [bar]
7)
8)
9)
7)
On-off differential 8…12%
8)
On-off differential 13…17%
9)
On-off differential 17…23%
p = f (Q) Performance limits [40bar]
P0212.ai
0
10
20
30
40
Q [l/min]20 25 30151050
p [bar]
11)
10)
10)
On-off differential 27…33%
11)
On-off differential 37…43%
400-P-379101-EN-01/11.2020
DWPB-4N…
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5 Dimensions & sectional view
With adjusting screw “S” With hand-knob adjuster “H”
27.5 ... 31
15.5...2239
54.4...61
107.5...114
53
3/4−16 UNF
4
7
6
3
2
5
1
13
24
4 s
1
Ø 23.5
4
3
1
2
6 Installation information
IMPORTANT!
When fitting the cartridges, use the specified
tightening torque. Set the switching point by
means of the adjusting screw (s
1
) or the hand
knob. Either set the 'Off' pressure, in which case
the 'On' pressure will depend on the selected per
centage on-off differential, or the other way
around. After you have set the valve, lock the ad
justing screw with the lock nut.
ATTENTION!
Only qualified personnel with mechanical skills
may carry out any maintenance work. Generally,
the only work that should ever be undertaken is to
check, and possibly replace, the seals. When
changing seals, oil or grease the new seals tho
roughly before fitting them.
Seal kit NBR no. DS-325-N
12)
Item Qty. Description
1 1 O-ring no.017 ∅17,17x 1,78 N90
2 1 O-ring no.014 ∅12,42x 1,78 N90
3 1 O-ring no.013 ∅10,82x 1,78 N90
4 1 O-ring no.012 ∅9,25x 1,78 N90
5 1 Backup ring ∅10,70x1,45x1,00 FI0751
6 1 Backup ring ∅9,40x1,45x1,00 FI0751
7 1 Backup ring ∅7,80x1,45x1,00 FI0751
IMPORTANT!
12)
Seal kit with FKM (Viton) seals, no. DS-325-V
400-P-379101-EN-01/11.2020
DWPB-4N…
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7 Application examples
M
B
P
T
A
43
2
1
TÜV
DWPB−4N...
RV
P1
p2
p1
p1 = 'On' pressure
p2 = 'Off' pressure
Accumulator-charging circuit
In this application, the DWPB-4N… unloading cartridge
performs an automatic accumulator-charging function in re
sponse to the pressures at ports 4 and 1. Here, the normal
procedure is to use the adjusting screw to set the upper, 'Off'
pressure p2, and when this pressure is reached the pump
will therefore be switched over to unloaded bypass (con
nection 4→ 3 open). The 'Off' pressure p2 and the on-off
differential (10...40%) determine the lower, 'On' pressure
p1. When demand causes the pressure in the accumulator
circuit to fall to p1, the unloading cartridge closes the con
nection 4→ 3 and the pump supplies oil to the accumulator
circuit until the 'Off' pressure p2 is reached and another 'un
load' occurs.
M
B
P
T
A
A
B
43
2
1
DBV
RV2
P1
RV1
R
EG
AG
DWPB−4N...
WV
EG = fast-advance speed
AG = feed speed
R = return stroke
Pressure-dependent fast-advance " feed changeover
with 1 pump
In this application, when the directional valve (WV) is in its
parallel-arrows position, the unloading cartridge DWPB-…
remains closed until the valve pressure setting is reached,
and oil discharging from the rod end of the cylinder is routed
to the head end, where it supplements the pump delivery
(fast-advance circuit). When the pressure at ports 4 and 1
rises above the setting, the unloading cartridge opens the
connection 4→ 3 and the oil from the rod end flows to tank
with virtually no back-pressure. This cancels the fast ad
vance, and the cylinder's potential force is automatically in
creased (feed-speed circuit). The maximum force is limited
by the pressure-relief valve (DBV) positioned on the pri
mary side. When the directional valve (WV) is in its crossed-
arrows position, the unloading cartridge is closed and the
cylinder can be in-stroked again.
IMPORTANT!
The changeover from fast to slow speed means a
reduction in flow rate, which is often accompanied
by a sharp drop in system pressure. We therefore
recommend the use of unloading cartridges with
an on-off differential of 20%…40%.
400-P-379101-EN-01/11.2020
DWPB-4N…
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M
B
P T
A
A
B
43
2
1
DBV
RV
HD ND
R
EG
AG
WV
DWPB−4N...
EG = fast-advance speed
AG = feed speed
R = return stroke
High-/Low-pressure circuit with two pumps
There are applications with one high-pressure pump and
one low-pressure pump where the load pressure is used to
automatically change the cylinder out-stroke speed from
fast to slow. The DWPB-4N... unloading cartridge is used
here to switch the low-pressure pump 'Off' i.e. to unloaded
bypass. When the cylinder is in-stroked, the low-pressure
pump is brought back on-load again, provided that the dy
namic load pressure is less than the 'Off' pressure that has
been set at the unloading cartridge.
IMPORTANT!
We strongly recommend that unloading cartrid
ges with an on-off differential of 30%…40% be
used in all applications of this type.
8 Ordering code
D = pressure-control valve
WP = two-stage unloading cartridge
A ... Q = standard model - see relevant data sheets
Z ... R = special features - please consult BUCHER
2 = pressure function 4
(pilot drain 2 and remote control port 1 external)
N = cavity type AN
4 = nominal size 4
25 = pressure range 50…250 bar
10 = pressure range 20…100 bar
04 = pressure range 10… 40 bar
S = screw adjuster (standard)
H = hand-knob adjuster
On-off differential as % of Off (unload) pressure:
10 = 8…12%
15 = 13…17%
20 = 17…23%
30 = 27…33%
40 = 37…43%
(blank) = NBR (Nitrile) seals (standard)
V = FKM (Viton) seals
(special seals - please contact BUCHER)
1 ... 9 = design stage (omit when ordering new units)
-2
_
Ex.
254 --D SWP -B N 4-40 -
400-P-379101-EN-01/11.2020
DWPB-4N…
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9 Related data sheets
Reference (Old no.) Description
400-P-040011 (i-32) The form-tool hire programme
400-P-040191 (i-33.12) Cavity type AN
400-P-720121 (G-4.30) Line-mounting body, type GANA (G 3/8”)
E 2020 by Bucher Hydraulics AG Frutigen, CH-3714 Frutigen
www.bucherhydraulics.co
m
info.ch@bucherhydraulics.com
All rights reserved.
Data is provided for the purpose of product description only, and must not be construed as warranted characteristics in the legal sense. The
information does not relieve users from the duty of conducting their own evaluations and tests. Because the products are subject to continual
improvement, we reserve the right to amend the product specifications contained in this catalogue.
Classification: 430.305.315.305.305.355