Pressure Relief Device – Spring Orient-F84L

Flow Safe, Inc.

Balanced Without Bellows
Uses a pressure-assisted drag seal to dampen spindle movement, ensuring smooth performance and preventing "water hammer" or chatter, especially in systems with positive displacement pumps.
Employs plastic seats (like Teflon, Kel-F, or PEEK) combined with elastomeric O-rings to achieve zero leakage up to 90–95% of the set pressure.
Capable of initial modulation at low flow rates to softly relieve small upsets, followed by a pop action for full lift during major overpressure event
Includes a static backflow seal to prevent media from the discharge side from leaking back into the inlet if discharge pressure exceeds inlet pressure.

The Flow Safe F84L and F88 Series liquid relief valves are designed to provide customers with a stable, smooth-flowing relief valve with substantial capacity. Below the set point, pressure acting upon the valve spindle/seat surface generates a lifting force, F = P x A. This opening force is opposed by the spring closing force. At set point, as the seat starts to lift off the nozzle, an additional force is created in the ‘huddling chamber’ to boost the effective force due to pressure. At approximately 7.5% above set pressure, the combined upward forces cause the spindle to pop open to full lift. The larger F84L sizes achieve stability through the use of a process-pressurized drag seal on the spin dle. This O-ring helps dampen the movement of the spindle to prevent flutter or chatter. F88’s use a spring-energized Teflon seal. In all sizes, the spindle seal diameter is the same as the seat diameter, which makes the valves balanced against backpressure without the use of bellows. After the valve fully opens, blowdown is typically a fixed 20% on the larger sizes, and 30% for the F84L-2. At very low flow rates, the F84L can modulate open to relieve the upset and softly reclose at up to the nominal blowdown value. Strong coefficients of discharge Kd allow for smaller valves to be used, lending additional value by reducing the user’s capital costs. For water service over 140 °F, a lift lever can be provided except on the F84L-2.

Use Cases

Pump Protection:
Lube & Seal Oil Systems:
Process Water
Closed-Loop Systems
Liquid hydrogen storage tank overpressure protection
Hydrogen pump discharge line relief
Cryogenic liquid hydrogen piping systems
Hydrogen liquefaction plant thermal expansion relief
Liquid hydrogen transport tanker safety
Chemical dosing pumps for hydrogen production
Hydrogen refueling station cooling systems
Liquid-filled manifolds in hydrogen processing

Capabilities

Set Pressure Range 30 to 24,277 psig (2.1 to 1,674 barg)
Temperature Range -65°F to 500°F (-54°C to 260°C)
Blowdown Fixed at approx. 20% (non-adjustable)

Flow Safe, Inc. Flow Safe is a manufacturer of high-quality pressure relief valves and accessories, crucial for safe hydrogen handling in the energy transition. It operates in New York and Texas. Flow Safe supports the hydrogen economy by ensuring safe, efficient hydrogen transport and storage.

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