The modular assemblies are ANSI/ISA 76.00.02 compatible and accommodate multiple-process streams in a limited space. A double-block and bleed (DBB) module controls each stream to eliminate cross contamination and maintain sample integrity. Valves offer double-block, bleed, and actuation functions within a single, compact module. The SSV features an integrated flow loop to streamline sampling and purging and provide consistent outlet flow. Additional features include: a vented air gap to prevent mixing of pneumatic actuator supply and system fluid; visual and tactile actuation indicators that confirm system operation; 0.125-in. female NPT or MPC-compatible inlet and outlet connections; and a built-in pneumatic actuator provides repetitive shutoff with few potential leak points.