What is Collapse Pressure in Filtration?
Collapse pressure is the maximum differential pressure a filter element can withstand before structural failure, measured in PSID. When pressure drop exceeds this rating, the element buckles inward, releasing trapped contaminants downstream. Cold starts and clogged elements are the most common causes of collapse failure.
Why Collapse Pressure Matters
During cold starts, high-viscosity oil creates extreme pressure drops across the filter element. If the cold-start ΔP exceeds the element’s collapse rating, the element can fail catastrophically. Similarly, a clogged element that exceeds its bypass valve setting will see increasing ΔP until it either bypasses or collapses. Collapsed elements release all captured contaminant downstream, potentially destroying pumps, valves, and actuators.
Testing Standards
Collapse pressure is tested per ISO 2941 (Hydraulic fluid power — Filter elements — Verification of collapse/burst pressure rating). The element is subjected to increasing differential pressure until structural failure occurs. The rated collapse pressure is set at a safety factor below the actual failure point.
Cross-Reference Considerations
When cross-referencing filters, always ensure the replacement element meets or exceeds the OEM collapse rating. A return-line element (25–150 PSID) substituted into a pressure-line application (3,000+ PSID) will collapse immediately. This is one of the most critical specifications to verify in any cross-reference.
Reference Table
| Collapse Rating (PSID) | Application | Typical Position |
|---|---|---|
| 25–75 | Suction/return line | Low-pressure tank return |
| 150–290 | Medium-pressure return | Return manifold, offline loop |
| 500–1,000 | Medium-pressure line | Charge pump, case drain |
| 3,000–3,600 | High-pressure line | Pressure-line filter, inline |
| 6,000+ | Ultra-high-pressure | Injection molding, press circuits |
Frequently Asked Questions
What happens when a filter element collapses?
How do I know the collapse rating I need?
Can cold starts cause filter collapse?
Related Specifications
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