Description
1" Pilot Pressure Limiting Valve 3–200 Bar – RSG 785-P
The RSG Type 785-P is an externally controlled pressure limiting valve designed to provide reliable overpressure protection in high-pressure liquid systems using manual stepless adjustment via a pilot valve.
The valve operates on a pressure-balanced principle and is installed in a bypass circuit. This allows the process-media pressure to be several times higher than the pneumatic control pressure, with configurations covering operating pressures up to 200 Bar.
When system pressure reaches the selected limit, the pilot-controlled valve opens the bypass path to relieve excess flow. This helps protect pumps, pipelines and high-pressure process equipment against excessive system pressure.
Pilot Operated Pressure Control
The RSG 785-P uses a pilot valve for manual stepless pressure regulation.
Control: Pilot Valve
Adjustment: Manual Stepless
Control Air: Maximum 8 Bar
Control Air Filtration: 40 Microns
Pressure Range: Up to 200 Bar
Unlike the 785-E electronically controlled 0–10V version, the 785-P uses its electrically operated pilot valve for the closing function while the required pressure is adjusted manually. The manufacturer's ordering code specifically identifies P as “pilot valve for closing function.”
Pressure-Balanced Bypass Design
The 785-P is designed specifically for bypass pressure limiting rather than conventional inline pressure reduction.
The pressure-balanced construction allows process-media pressure to be substantially higher than the pneumatic control pressure.
As system pressure reaches the adjusted limit, the valve controls bypass flow to prevent pressure continuing to rise.
This makes the 785-P particularly suitable for:
✓ Pump Protection
✓ Pipeline Protection
✓ High-Pressure Systems
✓ Bypass Pressure Limiting
✓ Industrial Process Systems
Pressure, Orifice & Flow Options
The RSG 785-P is available in four nominal diameters with AG1 and AG2 actuator configurations.
DN10 – 10mm
Pressure: 12–160 Bar
Maximum Flow: 3.0 m³/h
Actuator: AG1
DN12 – 12mm
AG1 Pressure: 10–120 Bar
AG2 Pressure: 10–200 Bar
Maximum Flow: 6.0 m³/h
DN15 – 15mm
AG1 Pressure: 5–64 Bar
AG2 Pressure: 5–140 Bar
Maximum Flow: 8.3 m³/h
DN20 – 20mm
AG1 Pressure: 3–40 Bar
AG2 Pressure: 3–80 Bar
Maximum Flow: 14.1 m³/h
All versions use a G1 BSP process connection.
AG1 & AG2 Actuator Options
Two actuator arrangements provide different pressure capabilities.
AG1 – Single Piston
Available for DN10, DN12, DN15 and DN20.
AG2 – Double Piston
Available for DN12, DN15 and DN20 where greater actuation force is required.
DN10 is not available with the AG2 actuator, as confirmed by the manufacturer's control-pressure diagrams on page 4.
The exact pressure range therefore depends upon both the valve orifice and selected actuator.
High Flow Capacity
Maximum flow according to nominal diameter:
DN10: 3.0 m³/h
DN12: 6.0 m³/h
DN15: 8.3 m³/h
DN20: 14.1 m³/h
This allows the valve to be selected around both the required system pressure and the amount of bypass flow that must be relieved.
Stainless Steel Construction
Body: AISI 303 Stainless Steel
Seals: FKM
Connection: G1 BSP
Nominal Sizes: DN10–DN20
The stainless steel body provides robust construction for demanding industrial liquid applications.
Compatibility of the process liquid with AISI 303 stainless steel and FKM should be confirmed before selection.
Liquid Media & Filtration
Media: Compatible Liquids
Maximum Contamination: 50 Microns
The 785-P is designed to operate with process liquids containing contamination up to 50µ.
The pneumatic control circuit requires:
Control Air: Maximum 8 Bar
Filtration: 40 Microns
This distinction is important: 50µ refers to the process liquid, while 40µ refers to the control-air filtration requirement.
Temperature
Media Temperature: 0°C to +60°C
Ambient Temperature: 0°C to +50°C
These limits apply to the standard AISI 303 stainless steel and FKM configuration.
Pilot Valve & Electrical Specification
The 785-P incorporates an electrically operated pilot valve as part of its control system.
Standard Voltages:
✓ 24V DC
✓ 230V AC 50Hz
✓ Special Voltages On Request
Voltage Tolerance: ±10%
24V DC Power: 6 Watts
230V AC Power: 9.2VA
Duty Cycle: 100% ED
Protection: IP65 with Connector
Electrical Connection: Industrial Form B
AC versions incorporate an integrated rectifier.
Manual Stepless Adjustment
The pressure setting itself is manually adjustable, allowing the required limiting pressure to be selected without a PLC or analogue set-point signal.
This distinguishes the 785-P from the 785-E:
785-P → Manual pressure setting with electrically operated pilot valve
785-E → Electronic 0–10V pressure setting
The 785-P is therefore particularly useful where electrical ON/OFF pilot control is required but remote proportional pressure adjustment is not necessary.
Pressure Control Characteristics
The manufacturer provides individual control-pressure diagrams for each nominal diameter and actuator configuration.
These show how the required pneumatic control pressure relates to the controlled media pressure.
For example, the AG2 configuration allows the DN12 version to operate at media pressures up to 200 Bar, despite control-air pressure remaining below 8 Bar.
Installation Requirements
Correct bypass pipework is important for stable pressure control.
The manufacturer specifies minimum straight flow-calming sections of:
✓ 3 × Pipe Diameter Upstream
✓ 5 × Pipe Diameter Downstream
The T-side must provide free discharge without dynamic back pressure and with minimum possible flow resistance.
Excessive downstream restriction can adversely affect the valve's pressure-limiting performance.
Mounting Position
The manufacturer recommends installing the valve with the:
Manometer preferably upright
This provides the preferred orientation for pressure monitoring and adjustment.
Typical Applications
✓ Pump Overpressure Protection
✓ High-Pressure Process Lines
✓ Bypass Pressure Limiting
✓ Industrial Fluid Control
✓ Hydraulic Test Systems
✓ High-Pressure Test Rigs
✓ Pump Circulation Systems
✓ Process Machinery
✓ Pipeline Protection
✓ Process Skids
✓ OEM Equipment
✓ Industrial Pump Systems
Why Choose the RSG 785-P?
The RSG 785-P combines manual stepless pressure adjustment with an electrically operated pilot valve, providing a useful intermediate solution between the manually controlled 785-H and electronically proportional 785-E.
Its pressure-balanced bypass design allows process pressures substantially higher than the pneumatic control pressure, with versions covering 3 to 200 Bar and maximum flow capacities from 3 to 14.1 m³/h.
With a G1 BSP connection, AISI 303 stainless steel body, FKM seals, AG1 or AG2 actuator configurations and 24V DC or 230V AC pilot control, the 785-P provides a robust solution for high-pressure pump and pipeline protection.
Available Versions
DN10 AG1 – 12–160 Bar – 3.0 m³/h
DN12 AG1 – 10–120 Bar – 6.0 m³/h
DN12 AG2 – 10–200 Bar – 6.0 m³/h
DN15 AG1 – 5–64 Bar – 8.3 m³/h
DN15 AG2 – 5–140 Bar – 8.3 m³/h
DN20 AG1 – 3–40 Bar – 14.1 m³/h
DN20 AG2 – 3–80 Bar – 14.1 m³/h
The manufacturer's type coding confirms AISI 303 construction, FKM sealing, G1 connection, 24V DC or 230V AC operation and AG1/AG2 actuator configurations.
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