Globe Valves for Oil & Gas

API 623 (Steel Globe Valves: Flanged and Butt-welding Ends, Bolted Bonnets) is the American Petroleum Institute standard for globe valves in oil refinery and petrochemical service. BS 1873 is the British Standard equivalent, widely used in the UK, India, and other international oil & gas markets. The main differences: API 623 is limited to bolted bonnet designs, addresses face-to-face dimensions per ASME B16.10, and requires API 598 pressure testing. BS 1873 covers both bolted and pressure-seal bonnets, and is referenced in UK and Indian oil & gas specifications (along with API standards). For export projects to the Middle East, Southeast Asia, and India, both API 623 and BS 1873 are accepted — the purchaser specification will state which standard governs. Vajra supplies globe valves to both standards with full material traceability.

Pressure-seal bonnets are required when the combination of high pressure and high temperature makes conventional bolted bonnet joints unreliable. ASME B16.34 and API engineering practice typically specifies pressure-seal bonnets for Class 900 and above (approximately 150 bar at 500°C with WC9). The pressure-seal principle: instead of bolts compressing a flat ring gasket, the pressure-seal ring (a truncated cone made of a soft material — carbon graphite for high temperature, PTFE for moderate temperature) is forced by internal pressure to seal harder against the body ID taper. As pressure increases, the seal force increases proportionally — the opposite of a bolted bonnet where bolts resist pressure and the gasket compression remains constant. Pressure-seal bonnets are standard for main steam isolation globe valves, HP steam injection throttle valves, and high-pressure wellhead globe valves at Class 1500–2500.

NACE MR0175 / ISO 15156 establishes the materials, hardness, and heat treatment requirements for equipment exposed to wet H₂S in oil & gas production. 'Wet H₂S' triggers sour service requirements when the pH of the water phase is ≤7 and H₂S is present, or when H₂S partial pressure exceeds thresholds defined in NACE MR0175 Part 1. For globe valves in sour service: (1) Body must be in NACE-compliant carbon steel with hardness ≤HRC 22 (250 HBW) — normalised and tempered WCB; (2) Trim (disc, seat ring, stem) must meet material and hardness requirements for the applicable NACE MR0175 table — SS 316L or Duplex 2205 trim is common; (3) Bolting must be NACE-compliant (B7M/2HM for carbon steel bolts/nuts); (4) Packing must be graphite or PTFE — asbestos is prohibited. Full NACE MR0175 compliance documentation including heat treatment records and hardness testing results is required with the EN 10204 3.1 MTC.