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Brand: Biffi
Biffi RPHS Spring-Return Hydraulic Rack and Pinion Actuator
Description
Overview
The Biffi RPHS is a spring-return (single-acting) hydraulic quarter-turn actuator of rack and pinion design. It belongs to the same series as the double-acting Biffi RPHD. The manufacturer describes both as high-pressure hydraulic actuators for on-off and modulating control of valves in heavy duty service, suitable for any low-torque quarter-turn application such as ball, plug and butterfly valves or dampers. The series has models for output torques up to 2600 Nm.
The RPHS is driven in one direction by pressurized fluid from an external hydraulic supply and in the other direction by a mechanical spring. It is not a self-contained electro-hydraulic unit and it has no built-in motor, pump or reservoir. The supply medium is hydraulic oil or fire-resistant fluid, at a supply pressure of 220 barg maximum. Seven Star LLC supplies the Biffi RPHS on request to buyers in Oman and the GCC, with lead time confirmed at quotation.
Operating Principle of the Biffi RPHS
The RPHS has a central housing that contains a rack and a pinion on the output shaft. A hydraulic cylinder is mounted on one side of the housing and a spring module on the other. Pressurizing the cylinder pushes the rack, turns the pinion and the valve stem through a quarter turn, and compresses the spring. When the hydraulic pressure is released, whether by a control command or by loss of supply, the spring pushes the rack back and returns the valve to its fail position. The model code ends in CL for spring to close or OP for spring to open.
The datasheet gives four torque values for each model: break and end torque for the spring stroke, and break and end torque for the hydraulic stroke at each supply pressure from 60 to 220 barg. Each model has its own maximum operating pressure (MOP), between 120 and 220 barg.
Engineering Design of the Biffi RPHS
The housing is totally enclosed and weatherproof, made of high-strength nodular cast iron, and a cast steel option is available. An integral vent valve prevents accidental pressurization of the housing. The rack and pinion are alloy steel and run in sintered bronze bushings charged with PTFE. The cylinder tube is carbon steel with an electroless nickel-plated, polished bore. The spring is alloy steel and sits in a carbon steel spring cartridge tube. The manufacturer states that the fully encapsulated spring module ensures personnel safety and simplifies assembly.
Angular stroke adjustment is possible between 80° and 100°. The RPHS uses the same actuator models and cylinder sizes as the RPHD (10-032, 20-040, 20-050, 40-045, 40-055, 40-065, 80-055 and 80-065), combined with spring types SS1, SS2, SS4 and SS5 and their E and I variants, so that the spring torque can be matched to the valve. The valve mounting flange has the standard ISO 5211 hole position, and accessories mount on an interface according to VDI/VDE 3845.
Key Features
The following features are stated by the manufacturer for the RPHD and RPHS series.
- Fully encapsulated RPHS spring module for personnel safety and simpler assembly.
- Spring to close or spring to open versions.
- Totally enclosed, weatherproof housing in high-strength nodular cast iron, suitable for hostile environments.
- Integral vent valve that prevents accidental pressurization.
- Compact rack and pinion design with simple construction.
- Angular stroke adjustment between 80° and 100°.
- Electroless nickel-plated and polished cylinder, with piston seals of low hysteresis and high sensitivity.
- Bushings in sintered bronze charged with PTFE for minimal friction and long life, and a cast steel housing option.
Industrial Applications
The Biffi RPHS is used where a small or medium quarter-turn valve or damper must move to a defined position when hydraulic pressure or the control signal is lost, and where a high-pressure hydraulic supply is available, for example from a hydraulic power unit or a hydraulic control panel. Typical duties are fail-close or fail-open isolation valves and modulating control valves of ball, plug or butterfly type.
For safety-related and hazardous-area service, the datasheet lists safety integrity level SIL 3 to IEC 61508, ATEX area classification II 2GD, and enclosure rating IP67M to IEC 60529 and NEMA 4, 4X and 6. Where no spring-driven fail action is needed, the double-acting Biffi RPHD is the corresponding model.
Technical Specifications
The table below summarizes the main data for the Biffi RPHS, taken from Biffi product data sheet VCTDS-02814-EN Rev. 0 (January 2022).
| Parameter | Specification |
|---|---|
| Model | Biffi RPHS (spring-return hydraulic) |
| Actuator Type | Hydraulic rack and pinion, quarter-turn, single-acting |
| Fail Action | Spring to close (CL) or spring to open (OP) |
| Supply Medium | Hydraulic oil or fire-resistant fluid |
| Supply Pressure | 220 barg maximum |
| Maximum Operating Pressure | 120 to 220 barg, depending on model |
| Output Torque | Up to 2600 Nm (series) |
| Standard Ambient Temperature | −20°C to +100°C |
| Extended Ambient Temperature | −60°C to +135°C |
| Stroke Adjustment | Between 80° and 100° |
| Spring Types | SS1, SS2, SS4, SS5 with E and I variants |
| Mounting Interface | ISO 5211 hole position; accessories to VDI/VDE 3845 |
| Hydraulic Connection | 1/4 inch NPT |
| Enclosure Protection | IP67M; NEMA 4, 4X, 6 |
| Approvals | ATEX II 2GD; SIL 3 (IEC 61508); PED 2014/68/EU; Machinery Directive 2006/42/EC |
| Valve Compatibility | Ball, plug and butterfly valves, dampers |
Request a Quote for Biffi RPHS Spring-Return Hydraulic Rack and Pinion Actuator
To request a quote for the Biffi RPHS, send Seven Star LLC the valve type and size, the required break and end torques with safety factor, the fail action (spring to close or spring to open), the hydraulic supply pressure and fluid, the ambient temperature range and any accessories needed. The actuator is supplied on request, with lead time confirmed at quotation.
Browse the full Biffi range or see more Valve Actuator products supplied by Seven Star LLC in Oman and the GCC.
See also: Biffi EFS 3000 Fail-Safe Electric Quarter-Turn Actuator.
Datasheets & Documents
- Datasheet Biffi RPHD / RPHS Hydraulic Actuators Datasheet Download
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About brand
Biffi is an Italian maker of valve actuators for the oil and gas and petrochemical industries. Its first factory opened in 1955 in Fiorenzuola d'Arda, near Piacenza, making electric actuators for the Italian petrochemical industry; the company moved to its present site in 1969. Biffi is now part of Emerson, and its pneumatic, hydraulic and electric actuators drive pipeline, wellhead and shutdown valves.
Seven Star LLC lists Biffi actuators across these operating media and supplies them to valve automation shops and operators in Oman, sized from the valve torque data.
Biffi company profile
| Founded | 1955, Fiorenzuola d'Arda, Italy |
|---|---|
| First products | Electric valve actuators for the Italian petrochemical industry |
| Headquarters | Fiorenzuola d'Arda, Piacenza, Italy (Biffi Italia Srl) |
| Ownership | Emerson |
| Product families | ALGA pneumatic scotch-yoke actuators, ALGAS gas-over-oil actuators, F01 and ICON2000 electric actuators, electro-hydraulic and hydraulic actuators for on-off and emergency shutdown duty |
Milestones
- 1955: The first Biffi factory opens in Fiorenzuola d'Arda.
- 1969: Biffi moves to its present location.
- 1978 and 1996: The plant is expanded.
Biffi actuator series on this page
The series names follow a logic that helps when reading a tag. ALGA is the pneumatic quarter-turn actuator and ALGAS its spring-return version. OLGA-H is the hydraulic quarter-turn actuator and OLGAS-H the fail-safe hydraulic version with spring. In the compact rack-and-pinion group, RPD and RPS are the double-acting and spring-return pneumatic pair, and RPHD and RPHS are their hydraulic counterparts. The F01 and F02 are electric quarter-turn actuators, the ICON2000 and ICON3000 are electric multi-turn actuators and the EFS 3000 is a fail-safe electric quarter-turn actuator; the manufacturer now names the Bettis SCE300 as the replacement for the F02. In each pair the S marks the model that returns to a safe position by spring.
Where Biffi actuators are used
Typical duties are emergency shutdown and blowdown valves, pipeline block valves, wellhead and manifold valves, tank farm isolation and large ball valves at compressor and metering stations. Spring-return models are chosen for fail-safe service. Hydraulic and electro-hydraulic units appear where instrument air is not on hand, as on remote GCC pipeline stations.
Biffi products we list
Ordering Biffi actuators: what we need
Actuators are sized, so the valve data comes first: valve type and size, the torque curve or at least break, run and end torques, the safety factor in your specification and the stem and mounting flange dimensions. Then the supply: minimum and maximum air or oil pressure, or voltage for electric units. State the fail action, stroking time, ambient temperature and the control accessories required. For an existing actuator send the model and serial number from the nameplate.
Facts checked against Biffi's own history (Emerson), October 2026.
Browse Biffi products by category: Valve Actuator.
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Frequently Asked Questions
How does the RPHS differ from the RPHD?
Both are hydraulic rack and pinion quarter-turn actuators from the same series. The RPHD is double-acting, with a hydraulic cylinder on each side driving the rack in both directions. The RPHS has one hydraulic cylinder and a spring module, so hydraulic pressure drives one stroke and the spring drives the return stroke.
Does the RPHS need a separate hydraulic supply?
Yes. The RPHS has no built-in motor, pump or reservoir. It needs pressurized hydraulic oil or fire-resistant fluid from an external source, such as a hydraulic power unit, at a supply pressure of 220 barg maximum. Only the return stroke is independent of the supply, because it is driven by the spring.
What applications is the RPHS suited to?
The manufacturer describes the RPHS as suitable for low-torque quarter-turn applications such as ball, plug and butterfly valves or dampers, for on-off and modulating control. The series covers output torques up to 2600 Nm. It is a compact actuator for small and medium valves that need a spring-driven fail action, not a high-torque unit for large pipeline valves.
Can the RPHS be spring to close or spring to open?
Yes. The datasheet lists both arrangements, with separate torque tables and dimension drawings for spring to close and spring to open. The fail action is shown at the end of the model code, CL for spring to close and OP for spring to open. The spring module is fully encapsulated.
How does Seven Star LLC supply the Biffi RPHS?
Seven Star LLC supplies the Biffi RPHS on request to buyers in Oman and the GCC. Lead time is confirmed at quotation. To prepare a quote we need the valve type and size, the required torques, the fail action, the hydraulic supply pressure and fluid, the ambient temperature range and any accessories required.
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