The Valve,safety Relief, cataloged under National Stock Number 4820-01-121-8903, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. Government technical data includes 19 specifications, cited from the U.S. Government catalog. 1 additional reference document (drawings, advisory and superseded references) is recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 4820-01-121-8903 |
| Item Name | Valve,safety Relief |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Status | ACTIVE |
| Flow Control Device | POPPET |
| Connection Style | GASKET SEAL(BOSS) SECOND END |
| Connection Style | FLARED (TUBE) FIRST END |
| Connection Type | THREADED EXTERNAL TUBE FIRST END |
| Connection Type | THREADED INTERNAL TUBE SECOND END |
| Style Designator | STRAIGHT THRU |
| Nominal Outside Diameter Tube Accommodated | 0.250 INCHES SECOND END IN |
| Operating Pressure | 3000.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS |
| Thread Direction | RIGHT-HAND ALL ENDS |
| Nominal Thread Size | 0.438 INCHES ALL ENDS IN |
| Seat Angle | 90.0 DEGREES FIRST END |
| Maximum Operating Temp | 400.0 FAHRENHEIT SINGLE RESPONSE DEGF |
| Thread Class | 3A FIRST END A |
| Thread Class | 3B SECOND END |
| Thread Quantity Per Inch | 20 FIRST END |
| Material | STEEL COMP 303 BODY |
| Thread Series Designator | UNIFIED NATIONAL JOINT (UNJ) FIRST END |
| Thread Series Designator | UNF SECOND END |
| Valve Operation Method | AUTOMATIC |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL A — No Demilitarization Required |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Reference | Meaning |
|---|---|
| 220T4TB | 3/2 Design control — primary reference U.S. Government activity |
NSN 4820-01-121-8903 is a Valve,safety Relief, classified under FSC 4820, Valves, Nonpowered. Status: active.
Key specifications for 4820-01-121-8903: Flow Control Device: POPPET; Connection Style: GASKET SEAL(BOSS) SECOND END; Connection Style: FLARED (TUBE) FIRST END; Connection Type: THREADED EXTERNAL TUBE FIRST END. 19 specifications are documented in the U.S. Government catalog.
No hazard code in the DLA record (HMIC N). Hazard information on this page is shown exactly as it appears in the DLA record.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-16.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.