Control valve STEVI Smart - 425/426 | ARI

ARI STEVI Smart 425/426 – Control Valve DN300–DN500

The ARI STEVI Smart 425/426 is a linear control valve designed for high flow rates in water, steam, gas, and thermal fluid networks. The series covers DN300–DN500, with PN16 in EN-JS1049 for DN300 and PN25/PN40 in 1.0619+N for DN300–DN500. Final selection should consider medium, temperature, pressure, and material strength.

Versions 425 and 426

• STEVI 425: Version with shaft packing. Standard PTFE packing from -10°C to 250°C, with EPDM option for -10°C to 150°C or graphite up to 450°C.
• STEVI 426: Version with stainless steel bellows. Available with graphite gasket from -60°C to 450°C or EPDM for lower temperatures. Used when external shaft leakage must be minimized.

Trim and Control Characteristics

Standard configuration is V-port plug with metal seat, equal percentage or linear characteristic, and rangeability 30:1. Tightness is Class IV according to DIN EN 60534-4. For lower seat leakage, PTFE soft seal up to 200°C with Class VI is available.

For high Δp or large DN, a pressure-balanced plug can be selected to reduce actuator force requirements. Perforated plug is used in steam and gases to limit noise, as well as in liquids under cavitation or flashing conditions.

Actuators

The valve is combined with pneumatic ARI-DP34/35, maximum air pressure 6 bar, or electric AUMA SAR 07.6–16.2 with IP67, handwheel, torque/travel switches, and overheating protection. Explosion-proof version available.

Typical Applications

Main uses include central steam lines, district heating networks, large heat exchangers, pump bypasses, cooling circuits, and industrial processes requiring stable proportional control in high flow rates.

FAQ

When to choose 426?
When the application requires bellows for emission limitation or high operating temperature.

What data is needed for sizing?
Medium, flow rate, P1/P2, temperature, Kvs, allowable leakage, Δp, noise, fail-safe position, and actuator type.