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MC5991 — SEAT,VALVE

✓ Government record, cited
— · GATE VALVE
PRODUCT OVERVIEW

MC5991: SEAT,VALVE.

The SEAT,VALVE is a the manufacturer industrial component. Key specifications include material: STEEL COMP 416 OVERALL, overall_height: 0.250 INCHES NOMINAL IN, hardness_rating: 80.5 ROCKWELL C MINIMUM AND 85.0 ROCKWELL C MAXIMUM OVERALL, style_designator: PLAIN, surface_treatment: PASSIVATE OVERALL, body_inside_diameter: 0.340 INCHES MINIMUM AND 0.472 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 4820-00-787-1855, indicating validated use in U.S. government and defense logistics supply chains. Available through authorized enterprise resellers and TPM (Third Party Maintenance) channels.

Verify compatibility with your specific system configuration before ordering.

WHERE IT FITS
MC5991
NSN: 4820-00-787-1855
FSC: 4820 — Valves, Nonpowered
CAGE: 62983 — EATON AEROSPACE, LLC DBA JACKSON SOUTH (USA)
SPECIFICATIONS
materialSTEEL COMP 416 OVERALL
overall_height0.250 INCHES NOMINAL IN
hardness_rating80.5 ROCKWELL C MINIMUM AND 85.0 ROCKWELL C MAXIMUM OVERALL
style_designatorPLAIN
surface_treatmentPASSIVATE OVERALL
body_inside_diameter0.340 INCHES MINIMUM AND 0.472 INCHES MAXIMUM IN
seal_accommodation_typeGROOVED
NSN4820-00-787-1855
COMPONENT DIAGRAM
GATE VALVE — FULL OPEN OR FULL CLOSE ONLY Rising STEM BONNET FLOW → → FLOW SEATS — — SIZE: — · — · — PN: MC5991 · OEM ⚠ VERIFY BEFORE ORDERING Gate valves = FULL OPEN or FULL CLOSE only — never throttle. Partial opening causes seat erosion and vibration. ✓ BROKER TIP Rising stem shows valve position visually — easier maintenance. Non-rising stem saves headroom. PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
SEAL ACCOMMODATION TYPE: GROOVED
•
HARDNESS RATING: 80.5 ROCKWELL C MINIMUM AND 85.0 ROCKWELL C MAXIMUM OVERALL
•
STYLE DESIGNATOR: PLAIN
•
BODY INSIDE DIAMETER: 0.340 INCHES MINIMUM AND 0.472 INCHES MAXIMUM IN
•
SURFACE TREATMENT: PASSIVATE OVERALL
•
MATERIAL: STEEL COMP 416 OVERALL
TECHNICAL CHARACTERISTICS
OVERALL HEIGHT0.250 INCHES NOMINAL IN
SEAL ACCOMMODATION TYPEGROOVED
HARDNESS RATING80.5 ROCKWELL C MINIMUM AND 85.0 ROCKWELL C MAXIMUM OVERALL
STYLE DESIGNATORPLAIN
BODY INSIDE DIAMETER0.340 INCHES MINIMUM AND 0.472 INCHES MAXIMUM IN
SURFACE TREATMENTPASSIVATE OVERALL
MATERIALSTEEL COMP 416 OVERALL
SUBSTITUTES & CROSS-REFERENCES 1
10109263Reference document
Same NSN cross-reference
Reference document — Informative reference only
LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Insurance item — stocked against contingency demandDemilitarization required — critical (Q)
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FREQUENTLY ASKED QUESTIONS
What is MC5991?
MC5991 is a SEAT,VALVE.
What parts can replace MC5991?
There is 1 known substitute for MC5991: 10109263. Substitute compatibility should be verified for your specific system.
What is the NSN for MC5991?
MC5991 is cataloged in the U.S. Government catalog under NSN 4820-00-787-1855. This indicates validated use in U.S. government and defense supply chains.
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✓ PartsTable — the parts reference. Every fact cited to its source.
PartsTable Design LLC · partstable.com
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.
PartsTable commercial catalog: edition Unified commercial catalog snapshot through 2026-09-28, edition date not on file, retrieved 2026-09-28.