PartsTable TECHNICAL DATA SHEET
JULY 2026Technical Data Sheet

D559A-6D-50Valve,safety Relief

Circor Aerospace, Inc. Dba Circor Aerospace Inc · NSN 4820-01-051-8215 · FSC 4820 · No Item Name Available
Verified by PartsTable
NSN 4820-01-051-8215 — this item is cataloged by the U.S. Government under National Stock Number 4820-01-051-8215. Primary manufacturer part number: D559A-6D-50.
Features
  • Valve,safety Relief — FSC 4820
  • Media for Which Designed: FUEL/OIL, HYDROCARBON FOURTH RESPONSE
  • Disk Loading Method: SPRING
  • Material: RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR SEAT
  • Style Designator: STRAIGHT THRU W/BAFFLE
  • Connection Type: THREADED EXTERNAL TUBE FIRST END
  • Flow Control Device: POPPET
  • Maximum Operating Temp: 250.0 FAHRENHEIT SINGLE RESPONSE DEGF
Applications
  • Flow control in piping systems
  • Pressure regulation
  • Steam and fluid isolation
  • Applications requiring Rubber Butadiene-Acrylonitrile Class Nbr Seat construction
General Description

The Valve,safety Relief, cataloged under National Stock Number 4820-01-051-8215, is classified within Federal Supply Class 4820 (No Item Name Available) of the Valves group. The primary manufacturer of record is Circor Aerospace, Inc. Dba Circor Aerospace Inc. Government technical data includes 25 verified specifications, sourced from the Federal Logistics Information System (FLIS). This item has 3 commercial cross-references from 2 manufacturers, enabling identification through both NSN and commercial part number lookups. 7 verified substitutes exist in the FLIS interchangeability database. Current acquisition status: Active.

Technical Specifications
ParameterValue
NSN4820-01-051-8215
Primary Part NumberD559A-6D-50
Item NameValve,safety Relief
FSC / FSG4820 / 48 — No Item Name Available
ManufacturerCircor Aerospace, Inc. Dba Circor Aerospace Inc
StatusACTIVE
Media for Which DesignedFUEL/OIL, HYDROCARBON FOURTH RESPONSE
Disk Loading MethodSPRING
MaterialRUBBER BUTADIENE-ACRYLONITRILE CLASS NBR SEAT
Style DesignatorSTRAIGHT THRU W/BAFFLE
Connection TypeTHREADED EXTERNAL TUBE FIRST END
Flow Control DevicePOPPET
Maximum Operating Temp250.0 FAHRENHEIT SINGLE RESPONSE DEGF
Media for Which DesignedAIR FIRST RESPONSE
Valve Operation MethodAUTOMATIC
Adjustable Pressure Range+25.0 TO 75.0 POUNDS PER SQUARE INCH LBS
MaterialALUMINUM ALLOY 2024 BODY
Thread Class3A FIRST END A
Media for Which DesignedACETYLENE SECOND RESPONSE
Material Document and ClassificationQQ-A-225/6 FED SPEC SINGLE MATERIAL RESPONSE BODY
Operating Pressure200.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS
Surface Treatment Document and ClassificationMIL-A-8625A TYPE I MIL SPEC SINGLE TREATMENT RESPONSE LOCATION NOT OTHERWISE SPECIFIED A
Furnished Items and Quantity1 DEFLECTOR CAP
Media for Which DesignedHELIUM FIFTH RESPONSE
Thread Series DesignatorUNIFIED NATIONAL JOINT FINE (UNJF) FIRST END
Opening Pressure Setting50.0 POUNDS PER SQUARE INCH LBS
Nominal Thread Size0.563 INCHES FIRST END IN
Media for Which DesignedAMMONIA, GASEOUS THIRD RESPONSE
Connection StylePLAIN (TUBE) FIRST END
Thread DirectionRIGHT-HAND FIRST END
Surface TreatmentANODIZE LOCATION NOT OTHERWISE SPECIFIED
Lifecycle & Compliance
Acquisition StatusACTIVE
HAZMATNo
Verified Substitutes 7
6210-00-243-00663850GREEN INTERCHANGEABLE
Lens,light
Bryant Electric
5950-00-802-3345B1047116 INTERCHANGEABLE
Reactor
L3harris Technologies, Inc.
6520-01-180-3242 INTERCHANGEABLE
Crown,dental,temporary
5340-01-276-2773C85-0001-100 INTERCHANGEABLE
Cap,protective,dust and Moisture
L3harris Technologies, Inc. Dba Harris Corp Div Harris Defense Communications
4720-01-505-470212469494 INTERCHANGEABLE
Hose,nonmetallic
U S Army Tank Automotive Command Amsta-Im-Mm
4820-01-524-67463978-01 INTERCHANGEABLE
Valve,safety Relief
Howell Laboratories Inc Dba Howell Laboratories Inc
5340-01-600-03793978 INTERCHANGEABLE
Handle,bow
Bmi Defense Systems, Inc
Cross-Reference Index
Part NumberManufacturer
D559A-6D-50 Circor Aerospace, Inc. Dba Circor Aerospace Inc (USA)
3978 Howell Laboratories Inc Dba Howell Laboratories Inc (USA)
3978-5-50 Howell Laboratories Inc Dba Howell Laboratories Inc (USA)
Related Parts
6210-00-243-0066INTERCHANGEABLE
LENS,LIGHT
3850GREEN
5950-00-802-3345INTERCHANGEABLE
REACTOR
B1047116
6520-01-180-3242INTERCHANGEABLE
CROWN,DENTAL,TEMPORARY
5340-01-276-2773INTERCHANGEABLE
CAP,PROTECTIVE,DUST AND MOISTURE
C85-0001-100
4720-01-505-4702INTERCHANGEABLE
HOSE,NONMETALLIC
12469494
4820-01-524-6746INTERCHANGEABLE
VALVE,SAFETY RELIEF
3978-01
5340-01-600-0379INTERCHANGEABLE
HANDLE,BOW
3978

Frequently Asked Questions

What is NSN 4820-01-051-8215?

NSN 4820-01-051-8215 is a Valve,safety Relief, manufactured by Circor Aerospace, Inc. Dba Circor Aerospace Inc, classified under FSC 4820 (No Item Name Available). Status: active.

What are the part numbers for NSN 4820-01-051-8215?

NSN 4820-01-051-8215 has 3 cross-referenced part numbers: D559A-6D-50 (Circor Aerospace, Inc. Dba Circor Aerospace Inc), 3978 (Howell Laboratories Inc Dba Howell Laboratories Inc), 3978-5-50 (Howell Laboratories Inc Dba Howell Laboratories Inc).

What NSN replaces 4820-01-051-8215?

There are 7 known substitutes for 4820-01-051-8215: 6210-00-243-0066, 5950-00-802-3345, 6520-01-180-3242 and 4 more. Verify interchangeability with system specifications before substitution.

What are the specifications of D559A-6D-50?

Key specifications for D559A-6D-50: Media for Which Designed: FUEL/OIL, HYDROCARBON FOURTH RESPONSE; Disk Loading Method: SPRING; Material: RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR SEAT; Style Designator: STRAIGHT THRU W/BAFFLE. 25 total characteristics are documented in the Federal Logistics Information System.

Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com