The Seat,valve, cataloged under National Stock Number 4820-01-442-0439, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. The manufacturer of record is Naval Sea Systems Command. Government technical data includes 11 specifications, cited from the U.S. Government catalog. The record lists 3 manufacturer part numbers 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through both NSN and commercial part number lookups. 3 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. 2 items share a part number with this NSN in the catalog (possible match — not a government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 | 4820-01-442-0439 |
| Primary Part Number | 218020209 |
| Item Name | Seat,valve |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Manufacturer | Naval Sea Systems Command |
| Status | ACTIVE |
| Body Outside Diameter | 5.140 INCHES NOMINAL IN |
| Thread Length | 0.752 INCHES NOMINAL SINGLE THREADED PORTION IN |
| Hardness Rating | 115.0 ROCKWELL R NOMINAL SEAT |
| Style Designator | PLAIN |
| Body Inside Diameter | 4.625 INCHES NOMINAL IN |
| Nominal Thread Size | 5.250 INCHES SINGLE THREADED PORTION IN |
| Thread Class | 3A SINGLE THREADED PORTION A |
| Thread Quantity Per Inch | 12 SINGLE THREADED PORTION |
| Material | PLASTIC POLYTETRAFLUOROETHYLENE SEAT |
| Thread Series Designator | UN SINGLE THREADED PORTION |
| Seating Surface Shape | FLAT |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL Q — CCL Item — Commerce Control List |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Part Number | Manufacturer |
|---|---|
| 801-6556655 FIND A6 | Naval Sea Systems Command (USA) |
| 218020209 PRIMARY | Naval Sea Systems Command (USA) |
| 801-6556655-A6 | Naval Sea Systems Command (USA) |
| Reference | Meaning |
|---|---|
| 2643-1002-63 FN A6 | 5/2 Secondary reference U.S. Government activity |
| 2643-1002-63 | D/9 Drawing number reference only U.S. Government activity |
| 6556655 | D/9 Drawing number reference only Naval Sea Systems Command |
NSN 4820-01-442-0439 is a Seat,valve, manufactured by Naval Sea Systems Command, classified under FSC 4820, Valves, Nonpowered. Status: active.
NSN 4820-01-442-0439 has 3 manufacturer part numbers on file: 801-6556655 FIND A6 (Naval Sea Systems Command), 218020209 (Naval Sea Systems Command), 801-6556655-A6 (Naval Sea Systems Command).
2 possible matches (shared part number, not a government interchangeability claim): 4820-01-442-0749, 4820-01-442-0793. Verify interchangeability with system specifications before substitution.
Key specifications for 218020209: Overall Height: 1.375 INCHES NOMINAL IN; Body Outside Diameter: 5.140 INCHES NOMINAL IN; Thread Length: 0.752 INCHES NOMINAL SINGLE THREADED PORTION IN; Hardness Rating: 115.0 ROCKWELL R NOMINAL SEAT. 11 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.
NSN 4820-01-442-0439 has DEMIL Code Q. Demilitarization may be required before disposal or transfer to non-military entities.
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.