Pressure Unloading Valve, Size 10
Q
max
= 60l/min,p
max
= 315bar
Two-stage, various on-off pressure differentials, optional soft-switching version
Series DWPA…,DWPBU…
1/6
Reference: 400-P-380101-EN-02
Issue: 01.2021
S Compact construction for
cavity type DD – M24x1,5
S Choice of 5 on-off differentials
S 3 pressure ranges available
S With integral pressure-relief function
S Optional soft-switching model is available
S All exposed parts with zinc-nickel plating
S Can be fitted in a line-mounting body
1 Description
Series DWPA… and DWPBU… cartridges are size 10, two
stage, high performance pressure-unloading valves with an
M24x1.5 mounting thread. They consist of a spool-type
main stage and a leak-free, ball-type pilot stage. Unloading
valves are used wherever a pump has to be disconnected
from and re-connected to a pressure circuit. For this pur
pose, either the 'Off' pressure or the 'On' pressure of the car
tridge can be set. When the 'Off' pressure is set, the 'On'
point will depend on the selected percentage on-off differen
tial, or the other way round. To disconnect the pump, the
cartridge responds to rising pressures at ports A and X by
opening the connection from A→B. This connection is then
kept open until the selected percentage on-off differential is
reached (falling pressure at port X) and the connection
A→B closes again (the 'On' point). The changeover to un
loaded bypass can be made less harsh (soft switching) by
using the DWPBU… model with damped switching charac
teristics, which is available as an alternative. These unloa
ding valves are predominantly used in accumulator-char
ging 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 operat
ing environments. If you intend to manufacture your own ca
vities or are designing a line-mounting installation, please
refer to the section “Related data sheets”.
2 Symbol
X
A
B
3 Technical data
General characteristics Description, value, unit
Designation pressure unloading cartridge valve
Design two-stage, with manual adjustment,
various on-off pressure differentials,
optional soft-switching version
Mounting method screw-in cartridge M24x1.5
Tightening torque Can be fitted in steel 65Nm ± 10%
Can be fitted in aluminium 50Nm ± 10%
Size nominal size 10, cavity type DD
400-P-380101-EN-02/01.2021
DWPA…,DWPBU…
2/6
Description, value, unitGeneral characteristics
Weight 0.48 kg
Mounting attitude unrestricted
Ambient temperature range -25°C … +80°C
Hydraulic characteristics Description, value, unit
Maximum operating pressure 315bar
Maximum flow rate 60l/min
Nominal pressure ranges L = (40…110bar), M = (80…210bar), N = (180…315bar)
On-off differentials
1)
(on-off differential from 'Off' (unload) pressure)
8 … 12% (pressure ranges M and N only)
13 … 17%
17 … 23%
27 … 33%
37 … 43 %
Flow direction A → B, 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…650mm
2
/s (cSt), recommended 15...250mm
2
/s (cSt)
Minimum fluid cleanliness
Cleanliness class to ISO 4406:1999
class 20/18/15
ATTENTION!
1)
Any back-pressure in port B (tank) directly redu
ces the on-off pressure differential.
Recommended back-pressure 3 1bar.
4 Performance graphs measured with oil viscosity 33mm
2
/s (cSt)
Δp = f (Q) Pressure drop - Flow rate characteristic
(for unloaded bypass, valve open)
P0200.ai
0
1
2
3
4
5
6
7
8
Q [l/min]40 50 603020100
p [bar]
Δp = f (Q) Pressure drop - Flow rate characteristic
(pressure-relief function)
P0201.ai
0
40
80
120
160
200
240
280
320
Q [l/min]40 50 603020100
p [bar]
400-P-380101-EN-02/01.2021
DWPA…,DWPBU…
3/6
p = f (Q) Performance limits
On-off differential 8 … 12%
P0202.ai
0
40
80
120
160
200
240
280
320
Q [l/min]40 50 603020100
p [bar]
p = f (Q) Performance limits
On-off differential 13… 17% / 17… 23%
P0203.ai
0
40
80
120
160
200
240
280
320
Q [l/min]40 50 603020100
p [bar]
p = f (Q) Performance limits
On-off differential 27 … 33% / 37… 43%
P0204.ai
0
40
80
120
160
200
240
280
320
Q [l/min]40 50 603020100
p [bar]
5 Dimensions & sectional view
Standard model: DWPA… Model: DWPBU… (soft switching)
14...21
47.5
126...133
64.5
78.5...85,5
2
1
M24x1.5
s32
27
Ma =8 Nm ±1 0 %
13
13
A
B
X
s
1
A
B
X
Steel: M
A
=65 Nm ±10 %
Alu: M
A
=50 Nm ±10 %
400-P-380101-EN-02/01.2021
DWPA…,DWPBU…
4/6
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
). Either set the
'Off' pressure, in which case the 'On' pressure will
depend on the selected percentage on-off differ
ential, or the other way around. After you have set
the valve, lock the adjusting screw with the lock
nut.
ATTENTION!
Type DWPBU-2… (soft switching) pressure-un
loading cartridges are not suitable for use in ap
plications with 2-pump systems or circuits for fast-
advance → feed changeover.
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-216-N
2)
Item Qty. Description
1 1 Seal ring ∅22,10/ 16,50 x2,50
2 2 O-ring no.020 ∅21,95x 1,78 N90
IMPORTANT!
2)
Seal kit with FKM (Viton) seals, no. DS-216-V
7 Application examples
M
B
P
T
A
AB
X
TÜV
DWPA... / BU
RV
P1
p2
p1
p1 = 'On' pressure
p2 = 'Off' pressure
Accumulator-charging circuit
In this application, the DWPA-2... unloading cartridge per
forms an automatic accumulator-charging function in re
sponse to the pressures at ports A and X. 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 A→ B 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 A→ B and the pump supplies oil to the accumulator
circuit until the 'Off' pressure p2 is reached and another 'un
load' occurs.
IMPORTANT!
The changeover to unloaded bypass can be
made less harsh (soft switching) by using the op
tional DWPBU-2... model.
400-P-380101-EN-02/01.2021
DWPA…,DWPBU…
5/6
M
B
P
T
A
A
B
AB
X
DBV
RV2
P1
RV1
R
EG
AG
DWPA...
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 DWPA-2…
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 A and X
rises above the setting, the unloading cartridge opens the
connection A→ B 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 primary
side. When the directional valve (WV) is in its crossed-ar
rows position, the unloading cartridge is closed and the cy
linder can be in-stroked again.
ATTENTION!
DWPBU-2… cartridges are not suitable for auto
matic fast-advance → feed changeover circuits.
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%.
M
B
P T
A
A
B
AB
X
DBV
RV
HD ND
R
EG
AG
DWPA...
WV
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 DWPA-2... 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.
ATTENTION!
DWPBU-2… cartridges are not suitable for use in
2-pump systems.
IMPORTANT!
We strongly recommend that unloading cartrid
ges with an on-off differential of 30%…40% be
used in all applications of this type
.
400-P-380101-EN-02/01.2021
DWPA…,DWPBU…
6/6
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
BU = soft switching, damped switching characteristics (optional)
2 = pressure function 2 (internal pilot-oil drain to B,
with external remote-control port X)
10 = nominal size 10
S = screw adjuster
N = pressure range 180…315 bar (Normal)
M = pressure range 80…210 bar (Medium)
L = pressure range 40…110 bar (Light)
(blank) = NBR (Nitrile) seals (standard)
V = FKM (Viton) seals
(special seals - please contact BUCHER)
On-off differential as % of Off (unload) pressure:
10 = 8…12% (pressure ranges M and N only)
15 = 13…17%
20 = 17…23%
30 = 27…33%
40 = 37…43%
1 ... 9 = design stage (omit when ordering new units)
-1
_
Ex.
402 --D NWP 10A S-
9 Related data sheets
Reference (Old no.) Description
400-P-040011 (i-32) The form-tool hire programme
400-P-060121 (i-45.2) Cavity type DD
400-P-740111 (G-24.21) Line- and manifold-mounting body, type DD-12 (G1/2”)
E 2021 by Bucher Hydraulics AG Frutigen, CH-3714 Frutigen
www.bucherhydraulics.cominfo.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: 430.305.315.305.320.355
