API 599

Covers — metal plug valves (lubricated and non-lubricated, tapered or cylindrical plug) with flanged, threaded, and welding ends for shutoff service; design, materials, ratings, and testing.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Pipeline plug valves → API 6D.
• Ball valves for equivalent quarter-turn duty → API 608.
• Ratings basis → ASME B16.34; testing → API 598.

Plug valves excel in dirty/sticky service; ball valves (API 608) are the alternative quarter-turn choice for clean fluids.

API 599 sets minimum requirements for metal plug valves:

• Materials — steel/alloy or iron bodies rated to B16.34 with compatible plug and sealant (for lubricated types).
• Design — lubricated or non-lubricated (sleeved/lined) quarter-turn plug for tight shutoff.
• Examination & Testing — shell and seat testing per API 598.

API 599 covers metal plug valves — quarter-turn shutoff valves whose tapered or cylindrical plug rotates within the body. Lubricated designs inject sealant for tight shutoff and are well suited to dirty, sticky, or slurry-laden service where the plug wipes the seat.

Ratings follow ASME B16.34 and testing follows API 598. For clean fluids, ball valves (API 608) are a common alternative; for pipeline duty, API 6D applies.

Engineering Note: Lubricated plug valves need a sealant-maintenance program; if that maintenance is unlikely, choose a non-lubricated (sleeved) design or a ball valve instead.