The Seat,valve, cataloged under National Stock Number 4820-00-923-2491, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. The manufacturer of record is Rolls-Royce Corporation. Government technical data includes 7 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through both NSN and commercial part number lookups. 3 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog.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 | 4820-00-923-2491 |
| Primary Part Number | 6820556-1 |
| Item Name | Seat,valve |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Manufacturer | Rolls-Royce Corporation |
| Status | ACTIVE |
| Body Outside Diameter | 0.659 INCHES MINIMUM AND 0.660 INCHES MAXIMUM IN |
| Style Designator | PLAIN |
| Material Document and Classification | AMS4640 ASSN STD SINGLE MATERIAL RESPONSE OVERALL |
| Body Inside Diameter | 0.344 INCHES MINIMUM AND 0.346 INCHES MAXIMUM IN |
| Seat Radius | 0.218 INCHES NOMINAL IN |
| Material | COPPER ALLOY OVERALL |
| Seating Surface Shape | RADIAL |
| 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 |
|---|---|
| 6820556-1 PRIMARY | Rolls-Royce Corporation (USA) |
| Reference | Meaning |
|---|---|
| 6820556-1 | 5/9 Secondary reference Allison Transmission Inc Dba Allison Transmission, Inc |
| 6820556 | 5/9 Secondary reference Allison Transmission Inc Dba Allison Transmission, Inc |
| 6820556 | 5/9 Secondary reference Rolls-Royce Corporation |
NSN 4820-00-923-2491 is a Seat,valve, manufactured by Rolls-Royce Corporation, classified under FSC 4820, Valves, Nonpowered. Status: active.
NSN 4820-00-923-2491 has 1 manufacturer part number on file: 6820556-1 (Rolls-Royce Corporation).
Key specifications for 6820556-1: Overall Height: 0.170 INCHES MINIMUM AND 0.190 INCHES MAXIMUM IN; Body Outside Diameter: 0.659 INCHES MINIMUM AND 0.660 INCHES MAXIMUM IN; Style Designator: PLAIN; Material Document and Classification: AMS4640 ASSN STD SINGLE MATERIAL RESPONSE OVERALL. 7 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.