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Disposable Hydraulic Filter Element – 190 L/min Flow, 21 MPa Collapse Pressure, Filtration Ratio = 75 at 7 μm
This specification sheet, part of SAE J2321, defines a high-collapse-pressure disposable hydraulic filter element for systems requiring a filtration ratio of at least 75 for particles larger than 7 µm. With a rated flow of 190 L/min and a collapse pressure of 21 MPa, it is designed for rigorous hydraulic applications. The standard also includes requirements for dimensions, O-ring seals, flow fatigue, and media migration.
Key Specifications and Performance Metrics
| Parameter | Requirement |
|---|---|
| Rated Flow | 190 L/min (50 gpm) at 68 mm²/s |
| Filtration Ratio | β75 at 7 μm (minimum) |
| Collapse Pressure | 21 MPa (3045 psi) minimum |
| Dirt Holding Capacity | 50 g minimum with ISO 12103-1 A3 dust |
| Clean Element Pressure Drop | 200 kPa (29 psi) maximum at rated flow |
| Reverse Flow Pressure | 140 kPa (20 psi) minimum |
| Flow Fatigue Cycles | 45,000 at 700 kPa + 5,000 at 2.0 MPa |
| Media Migration | < 5.0 mg |
| Magnetic Permeability | < 2.0 relative permeability |
Part Number System: Filter elements are ordered as J2321/2-7-X. The dash number -7 indicates the filtration rating (β75 at 7 μm). X denotes O-ring material: F for fluorocarbon, N for nitrile, X for purchaser-specified. Omission means no O-ring supplied.
Engineering Design Insights 🛠️
The element must be designed to endure a collapse pressure of 21 MPa without structural failure. The O-ring gland must conform to SAE AS4716 for an AS568-224 O-ring with no backup ring. Dimensional tolerances per Figure 1 and Tables 1A/1B are critical for proper fitment.
Testing requirements are extensive: the filtration ratio is verified via multi-pass testing with ISO 12103-1 A3 dust at an ingression rate of 3 mg/L. Flow fatigue testing subjects the element to 45,000 cycles at 700 kPa followed by 5,000 cycles at 2.0 MPa. Media migration must not exceed 5 mg, and magnetic permeability should be less than 2.0 unless otherwise waived.
The clean element pressure drop is limited to 200 kPa at rated flow with 68 mm²/s fluid. Reverse flow pressure capability is 140 kPa, ensuring the element can withstand occasional backflow conditions.
Common Pitfalls When Using SAE J2321-2 ⚠️
Interchangeability: This element is not a direct replacement for military part M24402/4 Size B. The military version has a higher collapse pressure (27.6 MPa) and lower filtration efficiency. Always verify system requirements before substitution.
- Incorrect test dust: Dirt holding capacity tests must use ISO 12103-1 A3 Medium Test Dust. Using other grades invalidates results.
- Wrong O-ring material: Ensure compatibility with system fluid. Fluorocarbon (F) is typical for petroleum fluids; nitrile (N) is also available.
- Misinterpreting β ratio: A β75 at 7 μm means the element removes at least 98.7% of particles ≥7 μm (β = upstream/downstream; efficiency = (β-1)/β × 100%).
- Neglecting geometry: Dimensions per Tables 1A/1B must be strictly observed to maintain sealing and performance.
Frequently Asked Questions
What are the exact dimensions of the filter element?
Refer to Tables 1A and 1B in SAE J2321-2. Key dimensions include an overall length (A) of 312.83 mm reference, a minimum inner diameter (D) of 50.50 mm, and an O-ring groove width (G) of 16.41–16.91 mm. The O-ring is size AS568-224.
What O-ring materials are acceptable?
Per section 1.1.2, designated factors: F = Fluorocarbon rubber per SAE AS3209-224, N = Nitrile rubber per AMS-P-83461/1-224, X = as specified by purchaser. If no letter, the element is supplied without an O-ring.
How is the filtration ratio verified?
The element is multi-pass tested per SAE J2321 using ISO 12103-1 A3 dust at 3 mg/L ingression rate. The terminal differential pressure can reach 1600 kPa. A minimum β75 at 7 μm must be maintained.
What is the allowed reverse flow pressure?
Section 3.9 requires the element to withstand a minimum differential pressure of 140 kPa (20 psi) in the reverse flow direction without collapse or damage.
