BS 1873 Globe Valve

1. Scope & Valve Types

• Valve Types:
  • Straight-Pattern Globe Valves: Standard design for general flow control.
  • Angle-Pattern Globe Valves: Redirects flow direction by 90°, reducing pipe fittings.
  • Y-Pattern Globe Valves: Low-resistance design for high-pressure systems.
• Application: Designed for throttling, regulating, or isolating fluid flow in pipelines carrying liquids, gases, or steam.

2. Size & Pressure Ratings

• Size Range: Typically DN 15 (½") to DN 300 (12"), though larger sizes may be custom-manufactured.
• Pressure Classes:
  • ASME B16.34 Classes: 150, 300, 600, 900, 1500, 2500.
  • PN Ratings: PN10 to PN400 (depending on design).

3. Materials

• Body/Bonnet: Carbon steel (e.g., ASTM A216 WCB), stainless steel (e.g., A351 CF8M), alloy steels (e.g., WC6, WC9).
• Trim Components:
  • Disc/Seat: Hardened stainless steel, Stellite, or other wear-resistant alloys.
  • Stem: Stainless steel (e.g., SS304/316) with anti-galling properties.
• Gaskets: Graphite, PTFE, or spiral-wound metal for high-temperature/pressure sealing.

4. Design Features

• Body-Bonnet Connection: Bolted bonnet (standard for high-pressure applications) or pressure-seal bonnet (for Class 600+).
• Stem Design: Rising stem (visible indicator of valve position) or non-rising stem (compact design).
• ‌Disc & Seat‌:
  • ‌Disc Types‌: Plug, needle, or composition disc for throttling/shutoff.
  • ‌Seat Design‌: Integral, replaceable, or welded-in seats for tight shutoff (metal-to-metal or soft-seated).
• Sealing: Metal-to-metal or soft-seated (for bubble-tight shutoff).
• ‌Flow Direction‌: Typically ‌flow-under-the-seat‌ to reduce operating torque.

5. Testing & Certification

• Shell Test: 1.5x rated pressure to verify body integrity.

• Seat Test: 1.1x rated pressure to ensure leak-tight closure (leakage rates per ISO 5208, e.g., Class B or D).

• ‌Hydrostatic Shell Test‌: 1.5x rated pressure (ASME B16.34).

• ‌Seat Leakage Test‌: 1.1x rated pressure to ensure leak-tight closure (leakage rates per ISO 5208, e.g., Class B or D).

• ‌Backseat Test‌: 1.1x rated pressure to validates stem sealing under pressure.

• Functional Test: Verification of smooth operation under specified pressure.

• Certification: Manufacturers provide test certificates (e.g., EN 10204 3.1) confirming compliance.

6. Pressure-Temperature Ratings

• Rated using ASME B16.34 or ISO 7005 tables, depending on material and class.
• Example: Carbon steel (WCB) at Class 150 has a max working pressure of ~19 bar at 100°C.

7. Marking & Identification

• Mandatory Markings:
  • BS 1873 standard number.
  • Size (DN), pressure class (e.g., Class 300), and material grade.
  • Manufacturer’s name/trademark, flow direction arrow, and heat number for traceability.

8. Applications

• Typical Uses:
  • Steam systems (power plants, boilers).
  • High-pressure oil/gas pipelines.
  • Chemical processing with corrosive media.

9. Referenced Standards

• Flanges: BS 4504 (PN) or ASME B16.5 (Class).
• Materials: ASTM/EN standards for steel grades.
• Testing: ISO 5208 for seat leakage.