Siemens 257-02000B Powermite 599 MT Series 2-Way Pneumatic Valve & Actuator Assembly 1/2" NC 0.4 Cv 3-8 PSI Brass

The Siemens 257-02000B is a complete Powermite 599 MT Series 2-Way Normally Closed (NC) valve and pneumatic actuator assembly designed for terminal unit hydronic and steam control applications. This assembly pairs a 1/2-inch brass-trimmed globe valve body with a 2-inch spring-return pneumatic actuator (599-01088), configured for a 3–8 psi (21–55 kPa) alternate spring range — indicated by the "B" suffix in the part number.

The valve features internal thread NPT (female x female) end connections, a flow coefficient of 0.4 Cv (0.34 Kvs), and a modified equal percentage flow characteristic. In its normally closed configuration, the valve remains shut at zero actuator pressure and opens as pneumatic pressure is applied within the 3–8 psi range. The 2-inch pneumatic actuator delivers a minimum of 67 lb (300 N) of force with a 7/32-inch (5.5 mm) stroke, and freely rotates to simplify pneumatic tubing installation.

Key Features:

• Assembly type: 2-Way, Normally Closed (NC), complete valve and actuator assembly
• Valve size: 1/2 inch with internal thread (female x female) NPT connections
• Flow coefficient: 0.4 Cv (0.34 Kvs)
• Flow characteristic: Modified equal percentage
• Trim material: Brass
• Actuator type: 2-inch pneumatic, spring-return (fail-safe)
• Spring range: 3–8 psi (21–55 kPa) — alternate range ("B" suffix)
• Actuator stroke: 7/32 inch (5.5 mm)
• Actuator force: Minimum 67 lb (300 N)
• Service: Liquid and steam applications
• Standard: ANSI Class 250

The Powermite 599 MT Series valve and actuator assemblies are a proven choice for HVAC terminal unit control in commercial building automation systems. The spring-return actuator ensures fail-safe operation, returning the valve to its normally closed position upon loss of pneumatic pressure. This assembly is part of the broader 257-series family compatible with Siemens building controls infrastructure.