High-pressure Self-sealing Flanged Globe Valves

2" - 12" (DN50 - DN300)

Class 600 - 2500 / PN 100-420

ASME B16.34, API 602 (forged), manufacturer-specific for pressure-seal flanged globe valves

A182 F22, A182 F91, A182 F316, A182 F304 — forged for zero-porosity integrity

Stellite overlay on seat ring and disc face — standard for high-pressure throttling

Plug disc with Stellite overlay on seating face

Pressure-seal (self-sealing) — line pressure compresses seal ring. No bonnet bolts under operating pressure.

OS&Y rising stem with handwheel

T-pattern (Z-body) with pressure-seal bonnet and flanged ends. Forged body.

Why T-Pattern When You Could Pick Y-Pattern

Three reasons — all practical.

Space. Y-pattern offsets inlet-to-outlet at 45°, taking more plan area. T-pattern with straight alignment fits easier in crowded pipe racks and tight equipment layouts.

Maintenance familiarity. Plant crews have worked T-pattern globe valves for decades. Disc, seat, stem, bonnet disassembly — identical to the standard valves they service every shutdown. Y-pattern extraction through the angled bonnet takes a different sequence. Familiarity reduces errors.

Throttling authority. T-pattern's higher drop gives more disc-position sensitivity across the full range — dropping flow from 100% to near-zero with one valve. Y-pattern's lower drop means less authority at low-flow positions. When range matters more than efficiency, T-pattern wins.

Pressure-Seal Bonnet — Same Mechanism

Identical to the Y-pattern self-sealing globe. Line pressure compresses the seal ring between bonnet and body. Higher pressure = tighter seal. No bonnet bolts carrying load under operating conditions — retention hardware only functions during assembly and zero-pressure states.

At Class 600-2500, bolted bonnets need bolts that are large, expensive, and a leak-path risk under thermal cycling. Pressure-seal eliminates that — the valve seals itself.

Forged Body — Mandatory

A182 F22, F91, F316, F304 — same forged lineup as the Y globe. Cast porosity at Class 600+ creates crack initiation risk. Forged bodies: zero porosity, homogeneous grain.

F22 for steam below 565°C. F91 for higher service with improved creep resistance. F316 for corrosive petrochemical. F304 for stainless resistance at lower temperatures.

Stellite Overlay — Standard

Disc face and seat ring both carry Stellite. Same reasoning as the Y globe — high-velocity flow at Class 600+ erodes bare metal. Cobalt-chromium survives closing impact and partial-open throttling erosion.

Disc guides inside the body bore for centered seating at high differential pressure.

Flanged Ends — Practical for Maintenance

Flanged connections allow bolted removal at Class 600-2500 — unlike butt weld, which requires cutting and re-welding. Throttling valves get serviced regularly. Flanged gives practical access without hot work.

Both end types acceptable at these pressures. Flanged is the choice when you need to pull the valve.

Tight pipe rack space, maintenance teams preferring familiar T-pattern procedure, and throttling where maximum regulation authority matters more than minimizing drop. Pressure-seal and forged body are identical.

T-pattern: straight vertical bonnet pull, disc comes out vertically. Y-pattern: extraction through angled bonnet, different sequence.

Flanged gives bolted removal without cutting pipe. Throttling valves see regular service. Flanged access saves time and eliminates hot work.

Yes — higher drop than Y-pattern at full open. Tradeoff: more throttling authority. If reduction range matters, the cost is acceptable. If efficiency matters, go Y-pattern.

Ask, but shouldn't. Bare metal erodes and galls at Class 600+ throttling pressures. Stellite is standard because field experience shows unacceptable disc and seat life without it.