Full Bore vs Reduced Bore Ball Valves: FB and RB on the BOQ
Technical guide · Supreme Valves India · Updated 2026-10-28
Direct answer: On ball valve BOQs, FB means full bore (full port) and RB means reduced bore. LO means lever operated. Full bore is required for pigging and when the datasheet demands minimum pressure drop; reduced bore is common and cheaper for ordinary isolation. Never assume — read the abbreviation on the line.
Typical archive lines look like: 2" BALL VALVE CL150 RF - ASTM A216 GR. WCB, TRIM RPTFE, FB, LO.
BOQ abbreviation cheat sheet
| Code | Meaning |
|---|---|
| FB / FP | Full bore / full port |
| RB / RP | Reduced bore / reduced port |
| LO | Lever operated |
| GO / Gear | Gear operated |
| FS | Fire safe (often API 607) |
| RF | Raised face flanges |
When full bore is mandatory
- Pigging or sphere passage
- Owner spec states full port
- Metering runs or low allowable ΔP
- Some slurry services where port reduction plugs
When reduced bore is fine
- Utility isolation, instrument root valves (often Class 800 screwed)
- Cost-sensitive Class 150 process on/off without pigging
- Floating ball valves in smaller sizes where RB is catalogue standard
Floating vs trunnion still matters
Bore choice is independent of floating vs trunnion mounting. Large Class 300/600 balls are often trunnion + full bore on pipeline RFQs. Small Class 150 WCB balls are usually floating; FB or RB must still be stated.
RFQ checklist
- FB or RB explicitly
- Seat (RPTFE / PTFE / metal)
- Fire-safe yes/no
- Lever, gear or actuator
Use the WCB Class 150 ball RFQ pattern for the most common carbon-steel lines.
Frequently asked questions
What does FB mean on a ball valve BOQ?
Full bore (full port): the ball hole matches the pipe inside diameter closely so pigs can pass and pressure drop is minimised. Reduced bore (RB) uses a smaller ball port and is common on utility and instrument isolation.
What does LO mean?
Lever operated. LC often means locking clip/lever. Gear operated is written separately as GO or GEAR OP.
Is reduced bore acceptable for Class 150 process balls?
Often yes for on/off isolation without pigging. If the spec says full bore or FB, do not substitute reduced bore without approval.