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Pressure Relief Valves

281 PRI® Pressure Relief Valve

This direct-acting valve is ideally suited for hydraulic applications where a fast-opening safety relief valve is needed to prevent system damage from pressure spikes. Minimum cracking pressures are available from 80-3600 psid. An integral safety screen is available for added protection.

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Key Product Facts
  • Safety Relief Valve
  • Diameter:0.281 inches
  • Full Open Lohm Rate:350 Lohms max
  • Nominal System Pressure:Up to 3000 psi
  • Cracking Pressure Range:80 to 3600 psi
For More Information

Product Information

General Performance
Characteristic Specification
Leakage at Minimum Cracking Pressure 1 Drop / Minute Maximum
Leakage at Shutoff 20 Drops / Minute Maximum
Restriction at Minimum Recommended Valve Lift 1500 Lohms Maximum
Nominal System Pressure up to 3000 psi
System Peak Pressure 5000 psi Maximum
Screen Hole Size (Screened Version Only) 0.008 inches Nominal
Nominal Weight Unscreened: 4.5 grams
Screened: 6 grams
Test Fluid MIL-PRF-83282 at 85°F
Materials
PART MATERIAL SPECIFICATON
Body 303 CRES QQ-S-763C
Pin 303 CRES QQ-S-763C
Tube 304 CRES AMS 5639
Spring 17-7PH CRES AMS 5678
Ball 440C CRES AMS 5630
Ball Follower 303 CRES QQ-S-763C
Spring Seat 303 CRES QQ-S-763C
Screen (Screened Version Only) 304L CRES ASTM A 666
Braze (Screened Version Only) - AMS 4774
Finish: All CRES parts passivated.
Pins are prewaxed. Do not degrease. Do not lubricate.
Flow Curve
Cross Section Views
Screened Relief Flow Forward Configuration
Dimensional Views
Unscreened Configurations
This image is for reference only. All dimensions are in inches.
Installation Hole Details
Unscreened Configurations
This image is for reference only. All dimensions are in inches.

Part Numbers & Specifications

This table below contains the part numbers and technical specifications for this product. If you have specific questions, need a quote, or would like to request a handbook or drawing, click the red request button in the column on the far right.

Image Specifications
Flow Curve
Part Numbers & Specifications
Filter Part Numbers
FLOW DIRECTION
SCREEN
PART NUMBER
FLOW DIRECTION
SCREEN
MINIMUM CRACKING PRESSURE (psid) FLOW POINT LOHM RATE FLOW POINT MINIMUM FLOW (gpm) FLOW POINT AT (psid) MINIMUM SHUT-OFF PRESSURE (psid) MINIMUM RECCOMENDED VALVE LIFT (LOHMS MAXIMUM) MINIMUM RECCOMENDED VALVE LIFT (gpm MINIMUM) Request Information
PRFA2812080L Forward Unscreened 80 220 0.9 100 68 1500 0.2 Request
PRFA2812120L Forward Unscreened 120 220 1.1 150 100 1500 0.2 Request
PRFA2812200L Forward Unscreened 200 220 1.5 250 170 1500 0.3 Request
PRFA2812300L Forward Unscreened 300 220 1.8 375 255 1500 0.3 Request
PRFA2812400L Forward Unscreened 400 220 2.1 500 340 1500 0.4 Request
PRFA2812500L Forward Unscreened 500 220 2.4 625 425 1500 0.4 Request
PRFA2812600L Forward Unscreened 600 220 2.6 750 510 1500 0.4 Request
PRFA2812700L Forward Unscreened 700 220 2.8 875 595 1500 0.5 Request
PRFA2812800L Forward Unscreened 800 220 3 1000 680 1500 0.5 Request
PRFA2812900L Forward Unscreened 900 220 3.2 1125 765 1500 0.5 Request
PRFA2812100D Forward Unscreened 1000 220 3.4 1250 850 1500 0.5 Request
PRFA2812110D Forward Unscreened 1100 220 3.5 1375 935 1500 0.6 Request
PRFA2812120D Forward Unscreened 1200 220 3.7 1500 1020 1500 0.6 Request
PRFA2812140D Forward Unscreened 1400 220 4 1750 1190 1500 0.6 Request
PRFA2812160D Forward Unscreened 1600 220 4.3 2000 1360 1500 0.7 Request
PRFA2812180D Forward Unscreened 1800 220 4.5 2250 1530 1500 0.7 Request
PRFA2812200D Forward Unscreened 2000 220 4.8 2500 1700 1500 0.8 Request
PRFA2812220D Forward Unscreened 2200 220 5 2750 1870 1500 0.8 Request
PRFA2812240D Forward Unscreened 2400 220 5.2 3000 2040 1500 0.8 Request
PRFA2812250D Forward Unscreened 2500 220 5.4 3125 2125 1500 0.8 Request
PRFA2812260D Forward Unscreened 2600 220 5.5 3250 2210 1500 0.9 Request
PRFA2812280D Forward Unscreened 2800 220 5.7 3500 2380 1500 0.9 Request
PRFA2812300D Forward Unscreened 3000 220 5.9 3750 2550 1500 0.9 Request
PRFA2812310D Forward Unscreened 3100 280 4.7 3875 2635 1500 0.9 Request
PRFA2812320D Forward Unscreened 3200 280 4.8 4000 2720 1500 0.9 Request
PRFA2812330D Forward Unscreened 3300 280 4.9 4125 2805 1500 1 Request
PRFA2812340D Forward Unscreened 3400 280 5 4250 2890 1500 1 Request
PRFA2812350D Forward Unscreened 3500 280 5 4375 2975 1500 1 Request
PRFA2812360D Forward Unscreened 3600 280 5.1 4500 3060 1500 1 Request
PRRA2812080L Reverse Unscreened 80 220 0.9 100 68 1500 0.2 Request
PRRA2812120L Reverse Unscreened 120 220 1.1 150 100 1500 0.2 Request
PRRA2812200L Reverse Unscreened 200 220 1.5 250 170 1500 0.3 Request
PRRA2812300L Reverse Unscreened 300 220 1.8 375 255 1500 0.3 Request
PRRA2812400L Reverse Unscreened 400 220 2.1 500 340 1500 0.4 Request
PRRA2812500L Reverse Unscreened 500 220 2.4 625 425 1500 0.4 Request
PRRA2812600L Reverse Unscreened 600 220 2.6 750 510 1500 0.4 Request
PRRA2812700L Reverse Unscreened 700 220 2.8 875 595 1500 0.5 Request
PRRA2812800L Reverse Unscreened 800 220 3 1000 680 1500 0.5 Request
PRRA2812900L Reverse Unscreened 900 220 3.2 1125 765 1500 0.5 Request
PRRA2812100D Reverse Unscreened 1000 220 3.4 1250 850 1500 0.5 Request
PRRA2812110D Reverse Unscreened 1100 220 3.5 1375 935 1500 0.6 Request
PRRA2812120D Reverse Unscreened 1200 220 3.7 1500 1020 1500 0.6 Request
PRRA2812140D Reverse Unscreened 1400 220 4 1750 1190 1500 0.6 Request
PRRA2812160D Reverse Unscreened 1600 220 4.3 2000 1360 1500 0.7 Request
PRRA2812180D Reverse Unscreened 1800 220 4.5 2250 1530 1500 0.7 Request
PRRA2812200D Reverse Unscreened 2000 220 4.8 2500 1700 1500 0.8 Request
PRRA2812220D Reverse Unscreened 2200 220 5 2750 1870 1500 0.8 Request
PRRA2812240D Reverse Unscreened 2400 220 5.2 3000 2040 1500 0.8 Request
PRRA2812250D Reverse Unscreened 2500 220 5.4 3125 2125 1500 0.8 Request
PRRA2812260D Reverse Unscreened 2600 220 5.5 3250 2210 1500 0.9 Request
PRRA2812280D Reverse Unscreened 2800 220 5.7 3500 2380 1500 0.9 Request
PRRA2812300D Reverse Unscreened 3000 220 5.9 3750 2550 1500 0.9 Request
PRRA2812310D Reverse Unscreened 3100 280 4.7 3875 2635 1500 0.9 Request
PRFA2812320D Reverse Unscreened 3200 280 4.8 4000 2720 1500 0.9 Request
PRFA2812330D Reverse Unscreened 3300 280 4.9 4125 2805 1500 1 Request
PRFA2812340D Reverse Unscreened 3400 280 5 4250 2890 1500 1 Request
PRFA2812350D Reverse Unscreened 3500 280 5 4375 2975 1500 1 Request
PRFA2812360D Reverse Unscreened 3600 280 5.1 4500 3060 1500 1 Request
PRFA2815080L Forward Screened 80 300 0.7 100 68 1500 0.2 Request
PRFA2815120L Forward Screened 120 300 0.8 150 100 1500 0.2 Request
PRFA2815200L Forward Screened 200 300 1.1 250 170 1500 0.3 Request
PRFA2815300L Forward Screened 300 300 1.3 375 255 1500 0.3 Request
PRFA2815400L Forward Screened 400 300 1.6 500 340 1500 0.4 Request
PRFA2815500L Forward Screened 500 300 1.7 625 425 1500 0.4 Request
PRFA2815600L Forward Screened 600 300 1.9 750 510 1500 0.4 Request
PRFA2815700L Forward Screened 700 300 2.1 875 595 1500 0.5 Request
PRFA2815800L Forward Screened 800 300 2.2 1000 680 1500 0.5 Request
PRFA2815900L Forward Screened 900 300 2.4 1125 765 1500 0.5 Request
PRFA2815100D Forward Screened 1000 300 2.5 1250 850 1500 0.5 Request
PRFA2815110D Forward Screened 1100 300 2.6 1375 935 1500 0.6 Request
PRFA2815120D Forward Screened 1200 300 2.7 1500 1020 1500 0.6 Request
PRFA2815140D Forward Screened 1400 300 2.9 1750 1190 1500 0.6 Request
PRFA2815160D Forward Screened 1600 300 3.2 2000 1360 1500 0.7 Request
PRFA2815180D Forward Screened 1800 300 3.4 2250 1530 1500 0.7 Request
PRFA2815200D Forward Screened 2000 300 3.5 2500 1700 1500 0.8 Request
PRFA2815220D Forward Screened 2200 300 3.7 2750 1870 1500 0.8 Request
PRFA2815240D Forward Screened 2400 300 3.9 3000 2040 1500 0.8 Request
PRFA2815250D Forward Screened 2500 300 4 3125 2125 1500 0.8 Request
PRFA2815260D Forward Screened 2600 300 4 3250 2210 1500 0.9 Request
PRFA2815280D Forward Screened 2800 300 4.2 3500 2380 1500 0.9 Request
PRFA2815300D Forward Screened 3000 300 4.3 3750 2550 1500 0.9 Request
PRFA2815310D Forward Screened 3100 350 3.8 3875 2635 1500 0.9 Request
PRFA2815320D Forward Screened 3200 350 3.8 4000 2720 1500 0.9 Request
PRFA2815330D Forward Screened 3300 350 3.9 4125 2805 1500 1 Request
PRFA2815340D Forward Screened 3400 350 4 4250 2890 1500 1 Request
PRFA2815350D Forward Screened 3500 350 4 4375 2975 1500 1 Request
PRFA2815360D Forward Screened 3600 350 4.1 4500 3060 1500 1 Request
PRRA2815080L Reverse Screened 80 300 0.7 100 68 1500 0.2 Request
PRRA2815120L Reverse Screened 120 300 0.8 150 100 1500 0.2 Request
PRRA2815200L Reverse Screened 200 300 1.1 250 170 1500 0.3 Request
PRRA2815300L Reverse Screened 300 300 1.3 375 255 1500 0.3 Request
PRRA2815400L Reverse Screened 400 300 1.6 500 340 1500 0.4 Request
PRRA2815500L Reverse Screened 500 300 1.7 625 425 1500 0.4 Request
PRRA2815600L Reverse Screened 600 300 1.9 750 510 1500 0.4 Request
PRRA2815700L Reverse Screened 700 300 2.1 875 595 1500 0.5 Request
PRRA2815800L Reverse Screened 800 300 2.2 1000 680 1500 0.5 Request
PRRA2815900L Reverse Screened 900 300 2.4 1125 765 1500 0.5 Request
PRRA2815100D Reverse Screened 1000 300 2.5 1250 850 1500 0.5 Request
PRRA2815110D Reverse Screened 1100 300 2.6 1375 935 1500 0.6 Request
PRRA2815120D Reverse Screened 1200 300 2.7 1500 1020 1500 0.6 Request
PRRA2815140D Reverse Screened 1400 300 2.9 1750 1190 1500 0.6 Request
PRRA2815160D Reverse Screened 1600 300 3.2 2000 1360 1500 0.7 Request
PRRA2815180D Reverse Screened 1800 300 3.4 2250 1530 1500 0.7 Request
PRRA2815200D Reverse Screened 2000 300 3.5 2500 1700 1500 0.8 Request
PRRA2815220D Reverse Screened 2200 300 3.7 2750 1870 1500 0.8 Request
PRRA2815240D Reverse Screened 2400 300 3.9 3000 2040 1500 0.8 Request
PRRA2815250D Reverse Screened 2500 300 4 3125 2125 1500 0.8 Request
PRRA2815260D Reverse Screened 2600 300 4 3250 2210 1500 0.9 Request
PRRA2815280D Reverse Screened 2800 300 4.2 3500 2380 1500 0.9 Request
PRRA2815300D Reverse Screened 3000 300 4.3 3750 2550 1500 0.9 Request
PRRA2815310D Reverse Screened 3100 350 3.8 3875 2635 1500 0.9 Request
PRRA2815320D Reverse Screened 3200 350 3.8 4000 2720 1500 0.9 Request
PRRA2815330D Reverse Screened 3300 350 3.9 4125 2805 1500 1 Request
PRRA2815340D Reverse Screened 3400 350 4 4250 2890 1500 1 Request
PRRA2815350D Reverse Screened 3500 350 4 4375 2975 1500 1 Request
PRRA2815360D Reverse Screened 3600 350 4.1 4500 3060 1500 1 Request
Clear Filters
Performance on MIL-PRF-83282 at 85°F

Installation & Accessories

Replacement Parts & Accessories
PART NUMBER DESCRIPTION
CUTA2810114C Installation / Extraction Tool Set
PRFA2810003A Replacement Pin

CAD Envelopes

Resources

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The Lee Company has developed the Lohm Laws for defining and measuring resistance to fluid flow. The Lohm is defined such that 1 Lohm will flow 100 GPM of water with a pressure drop of 25 psi at a temperature of 80°F.

Lohms for Liquids Lohms for Gases