Category
Safety & Relief
Subcategory
Disposal
Applicable standards
4
Issuing bodies
2
Description
Elevated or ground flare for safe disposal of relief & blowdown hydrocarbons.
Applicable Standards (4)
API — 3 standards
API 521
Pressure-relieving and Depressuring Systems
Causes of overpressure, relief load determination, depressuring, flare/disposal system design.
Key requirements (6)
- Sizing and design of pressure relief and depressuring systems.
- Relief scenarios: blocked outlet, fire, control valve failure, tube rupture, power failure, thermal expansion, runaway reaction, abnormal heat input.
- Fire heat input: Q = 21,000·F·A^0.82 BTU/hr (vapor space < 25 ft elevation; F = environment factor 0.3–1.0).
- Depressuring: typically blowdown to 50 % of design pressure or 100 psig (whichever lower) within 15 minutes for vessels exposed to fire.
- Flare radiation: max permissible 1.58 kW/m² (continuous), 4.73 kW/m² (limited exposure), 6.31 kW/m² (emergency).
- Disposal system sizing: must handle simultaneous events — 'global event' analysis.
API 537
Flare Details for Petroleum, Petrochemical, and Natural Gas Industries
Mechanical design, operation and maintenance of elevated and ground flare systems. Identical to ISO 25457.
API 535
Burners for Fired Heaters in General Refinery Services
Burner design and selection for refinery fired heaters.
NFPA — 1 standard
NFPA 69
Standard on Explosion Prevention Systems
Inerting, oxidant concentration reduction, deflagration suppression / venting.