The collapse of reverse osmosis water filter cartridges in a security filter (cartridge filter) is essentially caused by the differential pressure exceeding the structural strength of the cartridge.
Under normal operation, as long as the internal and external pressure difference remains within the design limit, the cartridge is safely supported by its inner core. Once this balance is broken, collapse (“crushing”) will occur.
Severe Fouling – Compression-Induced Collapse
When reverse osmosis water filter cartridges are rapidly clogged by large amounts of suspended solids, colloids, microorganisms, or broken filter media:
- Flow resistance increases sharply
- The inlet pressure outside the cartridge (e.g., 3 bar from the feed pump) remains nearly unchanged
- The internal pressure drops significantly due to high-pressure pump suction or restricted flow
This creates a pressure difference that may instantly exceed the cartridge’s tolerance (typically 2–2.5 bar for high-quality cartridges).
Deterioration of pretreatment will accelerate this process, such as: - Sand leakage from multimedia filters
- Activated carbon fines carryover
- Sudden turbidity spikes in feed water
- Overdosing of PAC/PAM causing floc formation
These conditions can quickly foul the cartridges and lead to external pressure crushing them.
Vacuum Formation – Suction-Induced Collapse
This is one of the most overlooked causes, and it is unrelated to clogging.
It usually happens due to incorrect system operation:
- The feed pump stops suddenly or the inlet valve closes
- The high-pressure pump does not stop in time
The high-pressure pump continues to draw water from the cartridge filter: - No incoming water supply
- Check valves may isolate the system, creating a closed space
This causes a vacuum (negative pressure) inside the filter. - Inside of the cartridge → vacuum
- Outside → near atmospheric pressure
The resulting pressure difference causes the cartridge to deform inward rapidly, often severely and instantly.
Insufficient Structural Strength of the Cartridge
Some reverse osmosis water filter cartridges, especially:
- PP melt-blown cartridges
- String wound cartridges
may have: - Weak inner cores
- Thin wall thickness
Typical pressure resistance may only be 1–1.5 bar.
Other contributing factors: - Using low-pressure cartridges in high-pressure systems
- Elevated water temperature reducing PP material strength
- Long-term operation under high differential pressure
This leads to material creep, fatigue, and eventual sudden collapse.
Water Hammer and Improper Operation
When pumps start or stop suddenly:
- Rapid changes in flow velocity
- Pressure spikes far exceeding normal operating pressure
These shock waves can instantly: - Crush
- Or even rupture the cartridges
Similarly: - Fast manual valve operation
- Sudden opening/closing
can cause pressure imbalance and structural failure.
Insufficient Design Margin
Poor system design can also lead to collapse:
- Flow rate exceeds total cartridge capacity
- Even clean cartridges start with high differential pressure (e.g., ~0.1 MPa)
- Slight fouling quickly pushes pressure beyond limits
Additionally: - Poor flow distribution design
- Uneven loading among cartridges
Some cartridges bear excessive load and fail first.
Summary
The collapse of reverse osmosis water filter cartridges is fundamentally caused by:
Excessive differential pressure (positive or negative)
Main triggers include:
- Severe fouling
- Vacuum conditions
- Weak cartridge structure
- Water hammer
- Poor system design