The Valve,safety Relief, cataloged under National Stock Number 4820-01-025-6844, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. The manufacturer of record is Howell Laboratories Inc Dba Howell Laboratories Inc. Government technical data includes 18 specifications, cited from the U.S. Government catalog. The record lists 2 manufacturer part numbers for this item, enabling identification through both NSN and commercial part number lookups. 4 items share a part number with this NSN in the catalog (possible match — not a government interchangeability claim). Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 4820-01-025-6844 |
| Primary Part Number | 3978-4SET20 |
| Item Name | Valve,safety Relief |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Manufacturer | Howell Laboratories Inc Dba Howell Laboratories Inc |
| Status | ACTIVE |
| Flow Control Device | DISK |
| Connection Style | PLAIN (TUBE) ALL ENDS |
| Connection Type | THREADED EXTERNAL TUBE ALL ENDS |
| Style Designator | STRAIGHT THRU |
| Operating Pressure | 150.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS |
| Adjustable Pressure Range | +0.5 TO 2.4 POUNDS PER SQUARE INCH LBS |
| Thread Direction | RIGHT-HAND ALL ENDS |
| Nominal Thread Size | 0.562 INCHES ALL ENDS IN |
| Maximum Operating Temp | 280.0 FAHRENHEIT SINGLE RESPONSE DEGF |
| Surface Treatment | ANODIZE LOCATION NOT OTHERWISE SPECIFIED |
| Media for Which Designed | REFRIGERANT 12 SECOND RESPONSE |
| Media for Which Designed | AIR FIRST RESPONSE |
| Thread Class | 3A ALL ENDS A |
| Thread Quantity Per Inch | 18 ALL ENDS |
| Material | RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR PACKING |
| Material | ALUMINUM BODY |
| Thread Series Designator | UNIFIED NATIONAL JOINT (UNJ) ALL ENDS |
| 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 |
|---|---|
| 3978-4 | Howell Laboratories Inc Dba Howell Laboratories Inc (USA) |
| 3978-4SET20 PRIMARY | Howell Laboratories Inc Dba Howell Laboratories Inc (USA) |
NSN 4820-01-025-6844 is a Valve,safety Relief, manufactured by Howell Laboratories Inc Dba Howell Laboratories Inc, classified under FSC 4820, Valves, Nonpowered. Status: active.
NSN 4820-01-025-6844 has 2 manufacturer part numbers on file: 3978-4 (Howell Laboratories Inc Dba Howell Laboratories Inc), 3978-4SET20 (Howell Laboratories Inc Dba Howell Laboratories Inc).
4 possible matches (shared part number, not a government interchangeability claim): 5310-01-441-5192, 5305-01-471-3206, 5930-01-500-9919. Verify interchangeability with system specifications before substitution.
Key specifications for 3978-4SET20: Flow Control Device: DISK; Connection Style: PLAIN (TUBE) ALL ENDS; Connection Type: THREADED EXTERNAL TUBE ALL ENDS; Style Designator: STRAIGHT THRU. 18 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.