What Does a Relief Valve Do?
The evolution of the cryogenic and industrial gas industries over the last few years has led to better safety and greatly improved transportation and storage of larger amounts of liquefied gases for longer periods of time. That said, cryogenic storage tanks will eventually experience temperature fluctuations due to their surroundings, resulting in occasional temperature increases inside the tank, which causes liquid gas to evaporate back into a gas state known as “boil-off gas.” Safety relief valves handle and mitigate that pressure rise.
Cryogenic safety relief valves, such as the Generant Stainless Series CRV valves, are designed to work in extremely low operating temperatures to ensure that valves won’t freeze open in the boil-off supply.
Contamination is a key concern in cryogenic and industrial gases, as some contaminants can lead to ignition under specific conditions in an oxygen-enriched environment. Thus, it’s critical for relief valves to be cleaned and packaged for oxygen service. The Generant CRV valves also incorporate Generant’s exclusive “Dirt Guard” feature, which increases the valves’ ability to tolerate particulate contamination. CRV valves are also ideally suited for use as a “blocked line safety” in cryogenic systems.
For extra high-purity needs, stainless steel relief valves are the top choice. Air and gas compressors, stationary cryogenic storage tanks and corrosive gases are just some of the applications where stainless steel is the optimal material. Generant’s Stainless Series CRV valves feature metal-to-metal face seal connections with electro-polished inlets, and are specifically manufactured for high-purity applications. The body, poppet, seat screw, spring retainer, in-line adapter, nuts and ferrules are all made of 316 stainless steel, with an internal spring made from either 302 or 17-7 PH stainless steel.
With some variations depending on manufacturer and application, a spring-loaded valve typically consists of a valve inlet mounted onto a pressurized system, a disc that prevents flow under normal operating conditions, a spring to hold the disc closed, and a body or bonnet to contain the components. As pressure increases, the valve begins to lift, increasing the spring force. Continued pressure increase overcompensates for the spring force and the valve opens to relieve pressure. The valve won’t close until system pressure falls back below the valve’s set pressure.
Generant Stainless Series CRV valves can be ordered with set pressures ranging from 10 to 750 Psig (0.7 to 51.7 Bar) and come factory preset and permanently locked. This prevents any tampering or accidental adjustment out in the field. The seat and poppet geometry, combined with optimized spring ranges, provide high flow rates with minimum pressure accumulation. Additionally, the valves’ compact design and variety of inlet and outlet configurations reduces size and piping requirements.
- Available CE marked in accordance to the requirements of the PED
- Exclusive “Dirt Guard” poppet: incorporated a poppet screen to extend valve life and ensure reliability
- High flow capacity and excellent reseat performance
- Supplied factory preset and permanently locked for tamper-proof service
- Discharge to atmosphere or a wide variety of inlet and outlet piping configurations
- Optional deflector cap available for diverting exhausted gas
- 100% factory tested for leakage, crack and reseat performance
- Cleaned and packaged for oxygen service
- Nominal set pressure range: 10 - 750 Psig (0.7 to 51.7 Bar)
- Factory set tolerance*:
- Set Pressure ≤ 28.90 Psig, ± 5%
- Set Pressure 29.00 - 48.30 PSI, ± 1.45 Psig
- Set Pressure ≥ 48.40 Psig, ± 3%
*tolerance specifications per EN ISO 4126-1.
- Zero leakage to 95% of set pressure
- Full rated flow at 110% of set pressure
- Unaffected by up to 10% back pressure
- 90% of set pressure
- 85% for PCTFE seals set below 100 Psig (6.9 Bar)
- Temperature Rating:
- -320º to 350º F (-196º to 176º C) based on seal material
- Lubricant: Krytox®