Modular platform design for hygienic regulating valve applications

The Alfa Laval Unique RV-ST builds on a well-proven modular platform engineered for high-volume liquid processing. The valve body, stem, plug seal, actuator, and electro-pneumatic controller are engineered as discrete, interchangeable components. Process engineers can configure the valve to match exact application requirements — selecting connection standards, elastomer materials, and positioner types without changing the core valve architecture. Stem bushings thread directly onto the actuator shaft, which simplifies handling during routine service.

Available in both ISO and DIN tube sizes from 1" (DN25) through 4" (DN100), the RV-ST covers a broad installation range. While the 1" size is dedicated to regulation, every size from 1½" upward incorporates an EPDM plug seal that allows the valve to double as a shut-off valve. This dual capability allows a single unit to handle tasks that would otherwise require separate regulating and isolation valves.

How do Kv curve options improve flow regulation accuracy?

A distinguishing feature of the RV-ST is its availability with multiple Kv curve options per valve size. Rather than forcing engineers to accept a single flow characteristic, Alfa Laval provides several curve profiles — such as curve A or G — so that the selected valve matches the required flow range precisely. This vast range of Kv-values ensures the valve can be tailored to the exact hydraulic needs of the process.

Why does the 50 % stroke operating point matter?

The RV-ST is optimised for an operating point at 50 % stroke. At mid-stroke, the positioner sits in the most linear and controllable portion of the Kv curve, where signal changes produce proportional and predictable changes in flow. This positioning also preserves travel in both directions, giving the controller room to compensate for upstream pressure fluctuations or downstream demand changes without approaching the mechanical limits of the stroke.

Targeting 50 % stroke during sizing means the valve spends most of its service life in a region where control resolution is highest. Engineers who select the appropriate Kv curve profile can place normal operating conditions in this sweet spot, avoiding the reduced accuracy that comes from running a valve near its fully open or fully closed extremes. Kv values are measured with water at 20 °C, and Alfa Laval recommends a maximum flow velocity of 5 m/s in tubing and valves.

Electro-pneumatic control and plant automation integration

The RV-ST pairs with an advanced electro-pneumatic process controller available in two versions: the Type 8694 (without display) and the Type 8692 (with display). Both positioners mount directly to the actuator and provide closed-loop stroke control, converting a 4–20 mA or digital signal into precise pneumatic positioning of the valve plug. The display-equipped Type 8692 provides on-valve diagnostics and feedback for commissioning and troubleshooting.

For integration into broader plant automation, the RV-ST supports ASI and IO Link Class A connectivity. An analogue feedback option is also available for installations that rely on conventional signal architecture. These interfaces allow the valve to report position and status directly to a PLC or SCADA system.

316L construction and hygiene compliance

All product-wetted steel components are manufactured from 1.4404 (316L stainless steel), with non-wetted steel parts in 1.4301 (304). Internal surfaces are bright-polished to Ra < 0.8 µm (< 32 µ inch), supporting CIP and SIP routines. Standard elastomers are EPDM, with HNBR and FPM available as options for applications involving aggressive media.

The valve operates within a temperature range of −10 °C to +140 °C with EPDM seals and handles inlet pressures up to 10 bar (1000 kPa). Specific pressure ratings vary by size and configuration — for example, the DN50 size supports up to 9.60 bar in air-closes configuration, while the DN100 size is rated to 4.80 bar air-closes. These ratings ensure the valve maintains integrity across the dairy, food, and beverage industries.

Maintenance access and long-term serviceability

The maintainable actuator option allows technicians to rebuild the actuator components on-site. Stem bushings, plug seals, and elastomers are all replaceable without removing the valve body from the line in most configurations. This modularity keeps spare-parts inventory lean and reduces potential downtime during scheduled maintenance intervals.

External surface finish options include a blasted finish for environments where specific aesthetic or cleaning standards are required. Overall heights with positioner range from 449 mm for the RV-ST 25 with Type 8694 to 643 mm for the RV-ST DN100 with Type 8692, maintaining a compact envelope for dense piping layouts.