Circle Seal K520T1-xM Relief Valve
500 Series: Adjustable Popoff & Inline Relief Valves, 0.5 to 150 psig
Features:
- Popoff, Popoff with Deflector Cap, or Inline configurations
- Adjustable, factory preset cracking pressure
- Zero leakage
- Accurate set pressure
- Wide range of cracking pressure
- Tamper-proof adjustment
- 100% seat leakage tested
- PED certifications and CE marking available for most models (add “PED” prefix to the valve part number if required)
Applications:
- System overpressure protection
- Storage tanks
- Freon recovery systems
- Medical equipment
- Refrigeration and heating equipment
- Measuring & dispensing pumps
- Communications equipment
- Process control instruments
- R&D pilot plants
- Vacuum pump safety

Circle Seal K520T1-xM Relief Valve Technical Data:
- Description: Popoff Relief Valve, 1/8″ to 1″ MNPT connections, constructed in 316SS with Polished PTFE seal, cracking pressures between 0.5 to 150 psig
- Configuration: Popoff
- Pressure Rating: 150 psig
- Body Material: 316SS
- Seal Material: Polished PTFE
- Cracking Pressure: 0.5 to 150 psig (REQUIRED SET PRESSURE MUST BE SPECIFIED)
- Flow at Cracking Pressure:
- Elastomeric seals: 5 cc/min
- PTFE seals: 0.02 SCFM
- Leakage, Ascending Pressure:
- Standard seals: 0 to 95% of cracking pressure
- Silicon & EPR seals: 0 to 80% of cracking pressure
- PTFE seals:
- Cracking pressures up to 2.4 psi: 4cc/min at 0 to 50% of cracking pressure
- Cracking pressures 2.5 psi and higher: 1 cc/min at 0 to reseat pressure, 10cc/min from reseat to 90% of cracking pressure
- Leakage at Reseat Pressure:
- All elastomeric seals: Zero
- PTFE seals: 1cc/min for cracking pressures 2.5 psi and higher
- Temperature: -320F to +165F
Cracking / Reseal Pressure Graphs:
Flow Rate Tables:
Dimensional Information:

Notes:
- Model K520 valves include Polished PTFE seal for cryogenic applications with cryogenic testing and serialization.
- Proper filtration is recommended to prevent damage to sealing surfaces.
- Cracking pressure tolerance is ±5% (may be greater than ±5% if set pressure is ≤ 1 psi); cracking pressure on initial crack may be higher than cracking pressure tolerance due to inherent characteristics of seals.
Please contact our Sales Department for assistance in selecting the right products for your application.
Product Catalog: Circle Seal Relief Valves
Service Information Sheet: Circle Seal 500-Series Relief Valves






