DNV-OS-A101 Safety Principles and Arrangements

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A: Categorisation

App.A A
101 Note that the categorisation may require adjustment based on the actual design of the component or frequency of use.

App.A A
201 Typical continuous sources of release:

—	internals of pressure vessels or storage tanks for flammable gas or vapours
—	process apparatus developing flammable gas or vapours
—	surface of flammable liquid
—	vent pipes which discharge continuously, for long periods or frequently
—	internals of pits containing active mud.

App.A A
301 Typical primary sources of release:

—	instrument and process vent pipes
—	relief valves outlets
—	pig receivers or launchers
—	pump and compressor seals (depending on design)
—	packed gland or seal of control valve
—	sample points
—	regularly used process drains (to open drain tundish)
—	flexible pipes and hoses (depending on materials and design)
—	ventilation openings from a Zone 1 area
—	active mud in open gutters before final degassing
—	shale shaker
—	vent from drilling mud degasser system.

App.A A
401 Typical secondary sources of release:

—	standard flanges, connections and valves
—	pumps and compressors (depending on design)
—	areas outside of Zone 0 or 1 if release point has varying rates and frequency of release
—	ventilation openings from a Zone 2 area
—	bell nipple (drilling nipple)
—	wireline stuffing box
—	set-back drill pipe if coated with drilling mud
—	gas vents from kill and choke manifold
—	diverter vents from drilling BOP.

Guidance note:
Welded piping systems without flanges or other leak sources are not regarded as sources of release.

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