The Valve,safety Relief, cataloged under National Stock Number 4820-01-420-8501, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. The manufacturer of record is The Boeing Company Div Defense. Government technical data includes 20 specifications, cited from the U.S. Government catalog. The record lists 1 manufacturer part number for this item, enabling identification through both NSN and commercial part number lookups. 3 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 4820-01-420-8501 |
| Primary Part Number | 7M666D2-30 |
| Item Name | Valve,safety Relief |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Manufacturer | The Boeing Company Div Defense |
| Status | ACTIVE |
| Flow Control Device | POPPET |
| Connection Style | PLAIN,OPTIONAL END(PIPE) SECOND END |
| Connection Style | PLAIN (PIPE) FIRST END |
| Minimum Operating Temp | -40.0 FAHRENHEIT DEGF |
| Connection Type | THREADED INTERNAL PIPE SECOND END |
| Connection Type | THREADED EXTERNAL PIPE FIRST END |
| Style Designator | STRAIGHT THRU NOTE: TO BE USED FOR VALVE BODIES OF ONE SECTION ONLY. |
| Operating Pressure | 200.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS |
| Thread Direction | RIGHT-HAND ALL ENDS |
| Nominal Thread Size | 0.250 INCHES ALL ENDS IN |
| Maximum Operating Temp | 250.0 FAHRENHEIT SINGLE RESPONSE DEGF |
| Disk Loading Method | SPRING |
| Media for Which Designed | AIR SECOND RESPONSE |
| Media for Which Designed | HYDROGEN FOURTH RESPONSE |
| Media for Which Designed | AMMONIA, GASEOUS THIRD RESPONSE |
| Media for Which Designed | ACETYLENE FIRST RESPONSE |
| Material | ALUMINUM BODY |
| Thread Series Designator | NPT ALL ENDS |
| Opening Pressure Setting | 30.0 POUNDS PER SQUARE INCH LBS |
| 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 |
| Part Number | Manufacturer |
|---|---|
| 7M666D2-30 | The Boeing Company Div Defense (USA) |
| Reference | Meaning |
|---|---|
| 559A-4DB-30 | 3/2 Design control — primary reference U.S. Government activity |
| 559A-4MP-30 | 5/9 Secondary reference U.S. Government activity |
| 559A-2MP-30 | 5/9 Secondary reference U.S. Government activity |
NSN 4820-01-420-8501 is a Valve,safety Relief, manufactured by The Boeing Company Div Defense, classified under FSC 4820, Valves, Nonpowered. Status: active.
NSN 4820-01-420-8501 has 1 manufacturer part number on file: 7M666D2-30 (The Boeing Company Div Defense).
Key specifications for 7M666D2-30: Flow Control Device: POPPET; Connection Style: PLAIN,OPTIONAL END(PIPE) SECOND END; Connection Style: PLAIN (PIPE) FIRST END; Minimum Operating Temp: -40.0 FAHRENHEIT DEGF. 20 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.