A single seat valve is a hygienic process valve with a single contact surface between the plug and the seat, used to shut off, divert, regulate or drain liquid flow in dairy, brewery, beverage, food, cosmetics and pharmaceutical process lines. It is widely used in CIP-cleanable production systems, specified wherever simultaneous flow of two products through one valve is not required and where a compact, easy-to-service design matters.

This category covers the Alfa Laval Unique SSV range supplied by Euroflow to system integrators, tank builders and end customers. Euroflow is the Alfa Laval distributor for postal codes 66–99 and 07–08 in southern Germany, covering Baden-Württemberg, Bavaria, Saarland, Rhineland-Palatinate, Hesse, Thuringia and Saxony. Built on a modular platform, the range spans pneumatic and manually operated configurations, shut-off and change-over bodies, and specialised variants for aseptic, ATEX, long-stroke, tank outlet, pressure relief, reverse acting and two-step duties.

Engineers typically specify hygienic single seat valves when they need reliable tight closure, predictable CIP behaviour and straightforward maintenance. The Unique SSV platform pairs a single plug-and-seat sealing geometry with a clamp-assembled body, defined-compression seals and few moving parts, which keeps wear predictable and total cost of ownership low. Available sizes from DN 25 to DN 100 cover most product, CIP and utility lines in hygienic plants, with documented Kv-values supporting flow sizing across that range.

For procurement teams, the modular design simplifies standardisation: one platform covers shut-off valves with two to four ports, change-over valves with up to six ports, and dedicated configurations for tank outlets or pressure relief. Seal options in EPDM, HNBR and FPM allow chemical and temperature matching to the process, while connection options in ISO, DIN, SMS male and clamp align with existing piping standards. Internal surfaces are polished to Ra < 0.8 µm to support hygienic cleanability.

The Alfa Laval Unique SSV range covers a single mechanical platform configured into distinct variants for different hygienic duties. All variants share the same plug-and-seat sealing principle and modular body construction — one, two or three valve bodies, clamp-assembled, with pneumatic or manual actuation. The configurations differ in actuator design, sealing approach, hygiene level and special function, which determines fit to a given process.

Configuration families

At a high level, the range is grouped by three axes: actuation (pneumatic or manual), hygiene level (standard, aseptic, ATEX) and special function (long-stroke, tank outlet, pressure relief, reverse acting, two-step, regulating). Bodies can be configured as shut-off valves with two to four working ports or as change-over valves with up to six ports. The valve seat between bodies in change-over versions is supplied for assembly to keep installation flexible.

Variants in detail

The standard pneumatic single seat valve is the baseline shut-off or change-over valve for product, CIP and utility lines. The aseptic variant adds a one-piece diaphragm that hermetically isolates the actuator side from the product, which is what makes it suitable for biotech and pharmaceutical duties; it is also available as a manually operated aseptic version for low-cycle sterile applications.

The ATEX variant is certified II 2 G D1 for use in explosive atmospheres and can be controlled via a ThinkTop Basic Intrinsically Safe unit. The long-stroke version provides a larger plug travel for highly viscous or particle-containing media. The manually regulating, two-step and reverse acting versions extend the platform with regulating, sequencing and fail-safe-open behaviours. Manually operated valves can later be converted to pneumatic by replacing the crank with an actuator, which protects standardisation investments as plants evolve.

Single seat valves sit at almost every branch point of a hygienic process line. They isolate sections during production, route product to the next tank or filler, divert flow between CIP supply and return, drain tanks at the bottom outlet and provide regulating or pressure relief functions where required. Because they use a single plug-and-seat seal rather than two independent seals, they are specified where simultaneous flow of two products through one valve is not needed — sequencing in time replaces simultaneous separation.

Where single seat valves fit in a hygienic process line

Upstream, a pneumatic shut-off valve typically isolates raw material tanks and feed lines. Around buffer and process tanks, change-over configurations divert flow between product, CIP supply and CIP return, while tank outlet valves drain bottoms cleanly without dead legs. Downstream, regulating and two-step versions support filling sequences, while hygienic pressure relief valves protect tanks, plates and pumps from overpressure during CIP and process upsets. Where simultaneous mixproof separation is required between product and CIP at the same valve, a double seat or mixproof valve is normally specified instead — single seat valves complement rather than replace that category.

Industry-specific requirements

In dairy and beverage plants, the dominant requirement is reliable CIP performance with EPDM seals and 3-A-aligned hygienic geometry. Daily cleaning cycles drive seal life expectations, which is why defined-compression seals and few moving parts matter. Breweries add CO2 handling and frequent change-over duties around fermentation and bright beer tanks, where modular two- and three-body configurations reduce piping complexity.

In food production with viscous or particle-laden media — sauces, dressings, fruit preparations — the long-stroke variant provides the additional plug travel needed for smooth passage. Cosmetics manufacturers running solvents, alcohols and essential oils typically combine FPM or HNBR seals with the ATEX variant for explosive atmospheres, working within its -10 °C to +135 °C window. Pharmaceutical and biotech processes specify the aseptic variant with its one-piece PTFE/EPDM diaphragm for hermetic isolation, supported by flush sterilisation at up to 150 °C and 3.8 bar.

Euroflow supports tank builders, plant engineers, system suppliers and end customers in Baden-Württemberg, Bavaria, Saarland, Rhineland-Palatinate, Hesse, Thuringia and Saxony with selection, sizing and configuration of the Unique SSV range, including single seat control valve arrangements for regulating duties.

A single seat valve operates on a deliberately simple principle: a movable plug seals against one stationary seat to open or close the flow path. The simplicity is what gives the category its hygiene, reliability and serviceability advantages — fewer dynamic seals, fewer wear points and a predictable failure mode.

Operating principle and key components

The valve consists of one or more valve bodies, a plug carrying a defined-compression seal ring, a stationary seat, a yoke connecting the actuator, and clamp rings that hold the assembly together. In a pneumatic single seat valve, compressed air at 6–8 bar moves the actuator piston against an internal spring; spring force returns the plug to its rest position when air is released. The result is a normally closed (NC), normally open (NO) or air/air (A/A) function selected at order time. Manually operated versions replace the actuator with a crank mechanism that drives the plug to a fixed position, secured by a lock screw or optional lockable handle.

The seat seal forms a single contact surface between plug and seat. When closed, defined compression on this seal blocks flow; when open, the plug lifts clear and product passes through the body with minimal pressure drop. For sensing and CIP integration, the valve can carry an Alfa Laval ThinkTop V-series control top, or a ThinkTop Basic Intrinsically Safe unit on the ATEX variant. The aseptic version replaces the dynamic stem seal with a one-piece PTFE/EPDM diaphragm that hermetically separates product from atmosphere — the same diaphragm can be retrofitted to Standard, Tangential, Two Step, Manual and Tank Outlet bodies.

How to select the right single seat valve

Selecting a single seat valve means matching a small set of variables to your process. Working through them in order shortens the configuration cycle and avoids late-stage rework.

Start with function: shut-off, change-over, tank outlet, regulating, pressure relief, reverse acting or two-step. Then fix the size using the documented Kv-values — flow sizing assumes water-like media at 20 °C per VDI 2173, with Q = Kv × √Δp. Confirm product pressure against the rating of the chosen variant: standard, ATEX and long-stroke versions handle up to 10 bar; the aseptic variant is rated 0–8 bar.

Next, select temperature and seals. EPDM covers -10 to +140 °C and handles most CIP regimes. ATEX variants are limited to -10 to +135 °C. HNBR and FPM extend chemical compatibility for fats, oils and solvents. Aseptic flush sterilisation supports up to 150 °C at 3.8 bar for short cycles. Confirm materials — 1.4404 (316L) for product-wetted parts and 1.4301 (304) for other parts, with internal Ra < 0.8 µm polished — and choose the connection standard that matches your installed base.

Then decide on actuation and control. Pneumatic with a ThinkTop V-series gives sensor feedback and CIP integration; the two-step and reverse acting options extend the actuator behaviour for sequencing and fail-safe-open duties. Manually regulating versions cover dosing and trim-flow duties without an actuator. The semi-maintainable actuator carries a 5-year warranty, which is a meaningful input when comparing total cost of ownership across alternatives.

How single seat valves compare to alternatives

Compared with double seat or mixproof valves, single seat valves do not provide a leakage chamber and atmospheric separation between two simultaneously flowing media. They are suitable where product and CIP are sequenced in time, not run in parallel through the same valve. Against butterfly valves, the single seat geometry typically delivers tighter shut-off, easier seal access and a more predictable pressure envelope in hygienic duty. Against diaphragm valves, the single seat platform reduces wear-part count for general hygienic shut-off, while the aseptic variant covers cases where a diaphragm would otherwise be specified for hermetic isolation.