Description
1" Manual Pressure Limiting Valve 3–200 Bar – RSG 785-H
The RSG Type 785-H is a manually adjustable pressure limiting valve designed for stepless overpressure control in high-pressure liquid systems.
The valve operates on a pressure-balanced principle and is installed in a bypass circuit, allowing the process-media pressure to be several times higher than the pneumatic control pressure. The manufacturer specifies DN10, DN12, DN15 and DN20 versions with pressure ranges extending up to 200 Bar.
Unlike the electronically controlled 785-E, the 785-H uses manual stepless pressure adjustment, making it particularly suitable where a fixed pressure limit is required without PLC, electrical or analogue control.
Manual Stepless Pressure Regulation
The RSG 785-H provides continuously adjustable manual pressure control.
Design: Manual Stepless Regulation
Pressure Range: 3 to 200 Bar
Installation: Bypass
Control: Pneumatic Pressure Balanced
The required pressure limit is set manually, allowing the valve to protect a system against excessive pressure without requiring an electrical supply or electronic controller.
Pressure Limiting Bypass Operation
The 785-H is specifically designed for bypass pressure limiting.
Rather than being installed inline as a conventional pressure reducing regulator, the valve is connected between the pressurised system and a return or discharge line.
As the system pressure reaches the selected limit, the valve opens the bypass path to relieve excess flow and limit further pressure increase.
The pressure-balanced construction allows the process pressure to be several times greater than the pneumatic control pressure.
This makes the 785-H particularly suitable for:
✓ Pump Protection
✓ Pipeline Protection
✓ High-Pressure Systems
✓ Bypass Pressure Limiting
✓ Hydraulic Test Systems
Pressure, Orifice & Flow Options
The 785-H is available in four nominal diameters with AG1 or 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 sizes provide different pressure-control capabilities.
AG1 – Single Piston
Available for DN10, DN12, DN15 and DN20.
AG2 – Double Piston
Available for DN12, DN15 and DN20 where increased pressure capability is required.
DN10 is not available with the AG2 double-piston 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 according to both the required pressure range and the amount of bypass flow that must be relieved.
Stainless Steel Construction
Body: AISI 303 Stainless Steel
Seals: FKM
Connection: G1 BSP
The robust stainless steel construction is suitable for demanding high-pressure industrial liquid-control applications.
Media compatibility should be confirmed against AISI 303 stainless steel and FKM for the actual process liquid.
Liquid Media & Filtration
Media: Compatible Liquids
Maximum Media Contamination: 50 Microns
The Type 785-H can handle process liquids with contamination up to 50µ.
The pneumatic control-air supply requires finer filtration:
Control Air: Maximum 8 Bar
Control Air Filtration: 40 Microns
The manufacturer specifies both the 50µ process-media contamination limit and 40µ filtered control-air requirement.
Temperature
Media Temperature: 0°C to +60°C
Ambient Temperature: 0°C to +50°C
These temperature limits apply to the standard AISI 303 stainless steel and FKM configuration.
Manual Pressure Adjustment
The 785-H provides a straightforward solution where the required pressure limit does not need to be changed electronically.
Once the desired pressure setting has been established, the valve provides continuous mechanical/pneumatic pressure limiting without:
✓ Electrical Power
✓ PLC Analogue Output
✓ 0–10V Control Signal
✓ Electronic Controller
This differentiates the 785-H manual version from the 785-E electronically controlled 0–10V version.
Pressure-Balanced Control
The pressure-balanced construction enables relatively low pneumatic control pressure to regulate considerably higher liquid pressure.
The control-pressure graphs supplied by RSG show different pressure relationships according to nominal diameter and whether the AG1 or AG2 actuator is fitted.
This allows configurations such as the DN12 AG2 version to control media pressures up to 200 Bar while the pneumatic control supply remains at a maximum of 8 Bar.
Installation Requirements
Correct bypass pipework is important for stable pressure regulation.
Minimum straight pipe lengths:
✓ 3 × Pipe Diameter Before Valve
✓ 5 × Pipe Diameter After Valve
The manufacturer also requires the T-side outlet to have free discharge without dynamic back pressure and with minimum possible flow resistance.
Restricting the return or discharge pipe can interfere with the valve's pressure-limiting performance.
Mounting Position
The manufacturer recommends:
Manometer preferably upright
This orientation assists practical installation and pressure-setting adjustment.
No Electrical Supply Required
A major advantage of the 785-H is that the pressure limiting function does not depend upon an electrical supply.
This makes it particularly useful for:
✓ Standalone Pump Systems
✓ Remote Installations
✓ Mechanical Process Systems
✓ Test Equipment
✓ Industrial Machinery
✓ Fixed Pressure Protection
For applications requiring pressure adjustment directly from a PLC or control system, the RSG 785-E 0–10V version is the more appropriate alternative.
Typical Applications
✓ Pump Overpressure Protection
✓ High-Pressure Process Lines
✓ Bypass Pressure Limiting
✓ Hydraulic Test Systems
✓ Industrial Fluid Control
✓ High-Pressure Test Rigs
✓ Pump Circulation Systems
✓ Process Machinery
✓ Process Skids
✓ OEM Equipment
✓ Pipeline Protection
✓ Fixed Pressure Protection
Why Choose the RSG 785-H?
The RSG 785-H provides manual stepless pressure limitation from 3 to 200 Bar without requiring an electrical supply or electronic control system.
Its pressure-balanced bypass design allows process pressures substantially higher than the pneumatic control pressure, while four nominal diameters provide maximum flow capacities from 3 to 14.1 m³/h.
With a G1 BSP connection, AISI 303 stainless steel body, FKM seals and AG1 or AG2 actuator options, the 785-H provides a robust solution for pump protection, high-pressure process systems and industrial bypass pressure-limiting applications.
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
Connection: G1 BSP
Body: AISI 303 Stainless Steel
Seals: FKM
Control: Manual Stepless Adjustment
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