Product Overview and Safety Certifications

ROSS Controls has engineered the PO Check Series to address the most demanding safety applications where trapped pressure and load holding are critical to protecting personnel and equipment. The valves feature poppet construction that achieves near-zero leakage while maintaining high dirt tolerance—essential characteristics for reliable operation in harsh manufacturing environments. 

Functional Safety Compliance

Every PO Check Series valve carries Category 1 PL c certification with SIL 2 safety integrity level, making them suitable for safety-related applications up to Performance Level c. For applications requiring higher safety integrity, the SV27 Series offers Category 3 PL e capability with external monitoring via safety-rated DPST switches providing up to 90% diagnostic coverage.  

19 Series Right-Angle Pilot Operated Check Valves

The 19 Series distinguishes itself through innovative right-angle port configurations that simplify piping installation and optimize space utilization in compact machinery designs. These valves are available in both threaded banjo and push-to-connect fitting options, accommodating diverse installation requirements across automotive, metal forming, and packaging applications. 

Flow Characteristics and Specifications

The 19 Series delivers flow capacities ranging from 0.4 Cv (400 Nl/min) for G1/8 and 1/8 NPT models to 2.3 Cv (2300 Nl/min) for G1/2 and 1/2 NPT configurations. Air flows freely from port 1 to port 2, while reverse flow from port 2 to port 1 requires a pilot signal at port 12. Minimum pilot pressure requirements vary proportionally with port 2 pressure, with detailed performance curves provided for each model to ensure proper system design. 

Construction Materials and Operating Conditions

Valve bodies utilize nickel-plated brass and anodized aluminum construction, with poppets manufactured from acetal and stainless steel. Buna-N seals provide reliable sealing across the operating temperature range of -10°C to 70°C (15°F to 160°F). The valves accommodate filtered air media at operating pressures from 5 to 150 psig (0.3 to 10 bar), with minimum operation frequency of once per month to ensure proper function. 

27 Series Inline Pilot Operated Check Valves

The 27 Series offers inline mounting configurations for direct cylinder port installation, providing robust load holding without complex manifold designs. Available in single and dual valve configurations with manual or remote trapped pressure relief options, these valves deliver exceptional versatility for circuit designers.  

Advanced Pressure Relief Options

A defining feature of the 27 Series is the trapped pressure relief capability, offered in three configurations:

• No Relief: Basic load holding without pressure release function
• Remote Relief: Pressure exhausted through blowdown signal port when supply pressure is removed
• Manual Relief: Push-button pressure release for maintenance and emergency situations 

High-Flow Capacity Models

The 27 Series achieves flow rates from 1.8 Cv (1800 Nl/min) in compact 1/4 NPT models to 21 Cv (2100 Nl/min) in 1-1/4 NPT configurations. Dual valve arrangements provide redundant load holding for Category 3 applications, with remote trapped pressure relief ensuring safe cylinder movement during controlled startup and shutdown sequences. 

Safety Circuit Applications and OSHA Compliance

ROSS PO Check valves are engineered for critical safety functions where OSHA compliance and ANSI standards mandate reliable load holding. The valves integrate seamlessly into safety circuits for vertical loads, pinch points, tooling protection, and counterbalance applications.  

Load Holding in Vertical Cylinder Applications

In vertical cylinder applications, pilot-operated check valves prevent hazardous load drop upon loss of electrical or pneumatic power. The trapped pressure between the check valve and cylinder maintains position until intentionally released through the blowdown signal port. This function is essential for OSHA-compliant lockout/tagout procedures where stored energy must be isolated and dissipated before maintenance access.  

Integration with Control-Reliable Safety Systems

For safety applications requiring control reliability, dual PO check valves provide redundant load holding. When integrated with external monitoring systems, these configurations achieve Category 3 PL e performance. The valves work in conjunction with safe exhaust valves, L-O-X energy isolation devices, and cross-mirror double valves to create comprehensive safety systems that comply with ANSI B11.TR3 and ISO 13849 requirements.  

Technical Specifications and Ordering Information

19 Series Model Numbers and Dimensions

The 19 Series includes twelve primary configurations covering NPT and G thread options from 1/8 to 1/2 inch port sizes. Right-angle valves with threaded banjo connectors feature compact dimensions ranging from 0.5 to 1.1 inches in width and 1.7 to 2.6 inches in height. Push-to-connect models accommodate tubing sizes from 5/32 inch to 10 mm, with dimensions optimized for tight installation spaces. 

27 Series Configuration Matrix

The 27 Series offers extensive configuration options organized by function:

• Single PO Check Valves: Models 2751Axxxx for basic load holding
• Dual PO Check Valves: Models 2768xxxx for redundant applications
• Pressure Controlled Valves: Models with pneumatic pilot control
• Solenoid Pilot Controlled Valves: Models 2778xxxx with 24V DC, 110-120V AC, and 230V AC options 

Each model specifies port sizes, flow coefficients, weight, pressure release type, and safety ratings. CAD models are downloadable for all configurations, enabling precise system integration.  

Industry Applications and Performance Benefits

Automotive Manufacturing

In automotive press lines and assembly operations, PO Check valves hold vertical tooling and workpieces during power loss events. The valves' rapid response and near-zero leakage prevent part damage and personnel hazards. Integration with ROSS CrossMirror double valves provides safe return functions while maintaining productivity targets.  

Metal Forming and Stamping

ROSS PO Check valves excel in metal forming applications where heavy dies and slides require reliable position holding. The poppet construction tolerates contaminated air common in stamping environments, while trapped pressure relief options enable controlled de-energization during die changes. Applications include press clutch/brake control, counterbalance systems, and monitored power systems.  

Packaging and Material Handling

For packaging machinery and automated material handling systems, the 19 Series right-angle design simplifies pneumatic routing around conveyor structures. The valves' compact footprint and push-to-connect options accelerate installation and maintenance, reducing downtime in high-speed production environments. 

Quality Assurance and Global Support

ROSS Controls manufactures PO Check Series valves in ISO 9001 certified facilities, with materials traceability and lot tracking for regulated industries. Every valve undergoes functional testing to ensure compliance with published specifications. The company's global network of 100 distributors provides local inventory, technical support, and rapid response for critical applications.  

Technical Documentation and Training

Comprehensive installation manuals, service guides, and troubleshooting documentation accompany each valve series. ROSS offers Total Machine Safety training programs, including Certified Functional Safety Expert (CFSE) certification for electrical and fluid power systems. Application engineering support is available to assist with system design, safety validation, and OSHA compliance verification.  

The ROSS PO Check Series Catalog provides engineers, safety managers, and procurement professionals with complete technical specifications for implementing safe load holding solutions in pneumatic systems. With Category 1 PL c and SIL 2 certification, robust construction, and versatile configuration options, these pilot-operated check valves represent the proven choice for critical safety applications across automotive, metal forming, and industrial manufacturing sectors.  

Download the complete catalog to access detailed performance curves, dimensional drawings, CAD files, and application circuit examples that demonstrate how ROSS PO Check valves integrate into compliant safety systems protecting workers and equipment worldwide.