Pressure Unloading Valve, Size 4
Qmax = 30 l/min, pmax = 250 bar
Two-stage, various on-off pressure differentials, with manual adjustment
Series DWPB-4N…
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

2

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 to DIN 50 979 and are thus suitable
for use in the harshest operating environments. If you intend
to manufacture your own cavities or are designing a linemounting installation, please refer to the section “Related
data sheets”.

Symbol
3

2

1

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

Reference: 400-P-379101-EN-01
Issue: 08.2014

1/7