The Valve,check, cataloged under National Stock Number 4820-00-409-1435, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. The manufacturer of record is Derbyshire Machine & Tool Co. 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through both NSN and commercial part number lookups. 4 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. 1 item shares a part number with this NSN in the catalog (possible match — not a government interchangeability claim). Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 4820-00-409-1435 |
| Primary Part Number | 418420-1 |
| Item Name | Valve,check |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Manufacturer | Derbyshire Machine & Tool Co |
| Status | ACTIVE |
| Flow Control Device | POPPET |
| Connection Style | FLARELESS FIRST END |
| Mounting Position | HORIZONTAL OR VERTICAL |
| Connection Type | THREADED EXTERNAL TUBE FIRST END |
| Style Designator | STRAIGHT THRU |
| Nominal Outside Diameter Tube Accommodated | 0.625 INCHES FIRST END IN |
| Operating Pressure | 3000.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS |
| Thread Direction | RIGHT-HAND FIRST END |
| Nominal Thread Size | 0.875 INCHES FIRST END IN |
| Seat Angle | 12.0 DEGREES FIRST END |
| Disk Loading Method | SPRING |
| Thread Class | 3A FIRST END A |
| Thread Quantity Per Inch | 14 FIRST END |
| Material | COPPER ALLOY AND STEEL CORROSION RESISTING BODY |
| Material | COPPER ALLOY AND STEEL CORROSION RESISTING FLOW CONTROL DEVICE |
| Material | COPPER ALLOY AND STEEL CORROSION RESISTING SEAT |
| Thread Series Designator | UNF FIRST 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 | S |
| Part Number | Manufacturer |
|---|---|
| 418420-1 | Derbyshire Machine & Tool Co (USA) |
| 418420-1 | Essex Industries, Inc. Dba Essex Industries (USA) |
| Reference | Meaning |
|---|---|
| 418420-1 | 5/9 Secondary reference Fort Walton Machining Inc |
| 418420-1 | 5/9 Secondary reference Penn State Tool & Die Corp |
| 418420-1 | 3/2 Design control — primary reference U.S. Government activity |
| 418420-1 | 5/9 Secondary reference U.s.a. Spares Inc. |
NSN 4820-00-409-1435 is a Valve,check, manufactured by Derbyshire Machine & Tool Co, classified under FSC 4820, Valves, Nonpowered. Status: active.
NSN 4820-00-409-1435 has 2 manufacturer part numbers on file: 418420-1 (Derbyshire Machine & Tool Co), 418420-1 (Essex Industries, Inc. Dba Essex Industries).
1 possible match (shared part number, not a government interchangeability claim): 2040-01-600-8396. Verify interchangeability with system specifications before substitution.
Key specifications for 418420-1: Flow Control Device: POPPET; Connection Style: FLARELESS FIRST END; Mounting Position: HORIZONTAL OR VERTICAL; Connection Type: THREADED EXTERNAL TUBE FIRST END. 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.