The Seat,valve, cataloged under National Stock Number 4820-01-440-4521, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. Government technical data includes 10 specifications, cited from the U.S. Government catalog. 3 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. 4 items share a part number with this NSN in the catalog (possible match — not a government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 | 4820-01-440-4521 |
| Item Name | Seat,valve |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Status | ACTIVE |
| Body Outside Diameter | 23.625 INCHES NOMINAL IN |
| Thread Length | 0.685 INCHES NOMINAL SINGLE THREADED PORTION IN |
| Style Designator | PLAIN |
| Body Inside Diameter | 21.630 INCHES NOMINAL IN |
| Nominal Thread Size | 23.625 INCHES SINGLE THREADED PORTION IN |
| Thread Class | 2A SINGLE THREADED PORTION A |
| Thread Quantity Per Inch | 12 SINGLE THREADED PORTION |
| Material | NICKEL ALLOY OVERALL |
| Thread Series Designator | UN SINGLE THREADED PORTION |
| Seating Surface Shape | O-RING |
| 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 |
|---|---|
| TDCV-016095-24-03 | 3/9 Design control — primary reference C M Industries Inc Dba Custom Marine Sales |
| TDCV-016095 | D/9 Drawing number reference only C M Industries Inc Dba Custom Marine Sales |
| TDCV-016095-24 PIECE 3 | 5/9 Secondary reference C M Industries Inc Dba Custom Marine Sales |
NSN 4820-01-440-4521 is a Seat,valve, classified under FSC 4820, Valves, Nonpowered. Status: active.
4 possible matches (shared part number, not a government interchangeability claim): 4820-01-440-4548, 4820-01-440-4605, 4820-01-440-4832. Verify interchangeability with system specifications before substitution.
Key specifications for 4820-01-440-4521: Overall Height: 0.875 INCHES NOMINAL IN; Body Outside Diameter: 23.625 INCHES NOMINAL IN; Thread Length: 0.685 INCHES NOMINAL SINGLE THREADED PORTION IN; Style Designator: PLAIN. 10 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.