Pressure Unloading Valve - Series DWPA... and DWPBU...

Oct 22, 2026

Series DWPA... and DWPBU... cartridges are size 10, two-stage, high-performance pressure-unloading valves with an M24x1.5 mounting thread. The design combines a spool main stage and a leak-free ball-type pilot stage to switch from pump connection A→B opening to a bypass unloading state based on a selectable on-off pressure differential. When configured, changeover provides optional soft switching for less harsh transitions and includes integral pressure-relief function for accumulator charging and fast advance-to-feed changeover circuits. Typical limits: 315 bar max pressure and 60 I/min max flow, with defined pressure ranges and differential options.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages6

Reading Time15 min

AccessFree to download

1 Description

2 Symbol

3 Technical data

4 Performance graphs

5 Dimensions & sectional view

6 Installation information

7 Application examples

Pressure Unloading Valve,Size 10 Qmax=60 I/min,Pmax=315 bar Two-stage,various on-off pressure differentials,optional soft-switching versionSeries DWPA…,DWPBU... # 1 Description Series DWPA...and DWPBU...cartridges are size 10,twostage,high performance pressure-unloading valves with anM24x1.5 mounting thread.They consist of a spool-typemain stage and a leak-free,ball-type pilot stage.Unloadingvalves are used wherever a pump has to be disconnectedfrom 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,thecartridge responds to rising pressures at ports A andXbyopening the connection from A→B.This connection is thenkept open until the selected percentage on-off differential isreached (falling pressure at port X)and the connection # 2 Symbol 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 M24×1.5 | | Tightening torque | 65 Nm±10%
Can be fitted in steel
Can be fited in aluminium 50 Nm±10% | | Size | nominal size 10,cavity type DD | ·Compact construction forcavity type DD-M24×1,5 ·Choice of 5 on-off differentials ·3 pressure ranges available ·With integral pressure-relief function ·Optional soft-switching model is available ·All exposed parts with zinc-nickel plating ·Can be fitted in a line-mounting body A→B closes again(the 'On'point).The changeover to un-loaded bypass can be made less harsh (soft switching)byusing 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 cartridgesalso provide a pressure-relief function e.g.for protecting thepump (see the application examples).All external parts ofthe cartridge are zinc-nickel plated according to DIN EN ISO19598 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,pleaserefer to the section “Related data sheets”. Reference:400-P-380101-EN-02 ATTENTION!1) Any back-pressure in port B(tank)directly redu-ces the on-off pressure differential.Recommended back-pressures1 bar. # 4 Performance graphs measured with oilviscosity 33mm²/s(CSt) △p=f (Q)Pressure drop-Flow rate characteristic(for unloaded bypass,valve open) △p [bar] | General characteristics | Description,value,unit | | --- | --- | | Weight | 0.48 kg | | Mounting attitude | unrestricted | | Ambient temperature range | -25℃..+80℃ | | Hydraulic characteristics | Description,value,unit | | --- | --- | | Maximum operating pressure | 315 bar | | Maximum flow rate | 60 I/min | | Nominal pressure ranges | L=(40...110 bar),M=(80..210 bar),N=(180...315 bar) | | On-off differentials 1)
(on-off differential from 'Off(unload)pressure) | 8…12%(pressure ranges M and Nonly)
13 ...17%
17...23%
27...33%
37 ...43% | | Flow drection | A→B,see symbols | | Hydraulic fluid | HL and HLP mineral oil to DIN 51524;
for other fluids,please contact BUCHER | | Hydraulic fluid temperature range | -25℃...+80℃ | | Viscosity range | 10…650 mm²/s(CSt),recommended 15..250 mm²/s(cSt) | | Minimum fluid cleanliness
Cleanliness class to ISO 4406:1999 | class 20/18/15 | △p=f (Q)Pressure drop-Flow rate characteristic (pressure-relief function) p=f (Q)Performance limits On-off differential 8...12% △p [bar] p=f (Q)P

FAQs

What are the main components and operating stages of the DWPA... and DWPBU... cartridges?

They are size 10 two-stage cartridges with a spool-type main stage and a leak-free ball-type pilot stage.

How does the valve switch when configured using on-off pressure settings?

On set-off, the cartridge opens the connection from A→B in response to rising pressures at ports A and X, and keeps it open until the selected on-off differential threshold is reached, then closes again at the corresponding on point.

What is the purpose of the DWPBU.. soft-switching model, and what limits apply to it?

DWPBU.. uses damped switching characteristics to make changeover less harsh. DWPBU-2 soft-switching cartridges are not suitable for applications using 2-pump systems or fast-advance→feed changeover circuits.

Oct 22, 2026

Upload by Malam Tenang