DATA PD , DR3... Product PD Unloader Valves. Function. Technical Features DR3510 DR3575

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1 Commercial Vehicle Systems Product Doc. No. Y2042 DATA (EN - Rev. 000) PD PD Function The Unloader Valve is used to control the maximum pressure of the compressed air delivered from the air compressor to the brake system of the vehicle. When the pressure in the system downstream of the Unloader Valve reaches the setting pressure (cut-out pressure) of the valve it operates to discharge to atmosphere any further air delivered from the compressor whilst maintaining the pressure in the brake system by means of an internal check valve. The Unloader Valve monitors the downstream pressure in the brake system and when the pressure falls to the DR50 cut-in pressure of the valve it operates to direct the air from the compressor back into the brake system to recharge it until the cut-out pressure is again reached. The difference between the cut-out and cut-in pressures is called the range. The Knorr-Bremse range of incorporate a safety valve so that, should the supply pressure exceed the setting of the safety valve, it will open automatically to exhaust the supply pressure to atmosphere. Some incorporate other ports to provide compressed air for tyre inflation or a signal pressure to operate other devices, such as air dryers, alcohol injectors or shut-off valves. Other valves are designed with a control port and the operation of the valve is controlled by an external device such as an air dryer with integral unloader. Standard Symbol as DIN ISO DR28 22 DR50 DR Technical Features Operating pressure: see table Ambient operating temperature range: -40 C to +80 C Air input temperature range: -40 C to +50 C Weight: see table DR DR50 DR575 2

2 PD Product Data Range Overview Part No. Type No. Cut-out Pressure [bar] Range [bar] Safety Valve Pressure [bar] Weight approx. [kg] DR DR DR DR Other versions are available. Pneumatic Connections Port Application Supply from air compressor -2 For tyre inflation or use as an auxiliary charging point (with test point fitted) 2 Delivery to brake system 22 Signal to control an alcohol injector 2 Signal to control an air dryer or shut-off valve Exhaust to atmosphere 4 Control port (signal from air dryer) Part No. Type No. Port M22x.5 - M22x.5 M2x.0 M2x.0 Ø2.5 ) DR28 M22x.5 - M22x.5 - Ø6 Ø5 ) DR50 M22x.5 M6x.5 M22x.5 M2x.0 M2x.0 Ø20 ) M2x DR50 M22x.5 - M22x ) DR575 M22x.5 - M22x ) - ) Hose connection 2) Integral silencer Servicing The operation of unloader valves should be checked regularly. For details of the correct service parts use the Product Search link on the website Knorr-BremseCVS.com. 2

3 Commercial Vehicle Systems PD Dimensions

4 PD Product Data DR28 4

5 Commercial Vehicle Systems PD DR50 5

6 PD Product Data DR50 DR575 Revision Details Rev. 000 New document. 6