A blocked screen gets cleaned, and the cleaning method is chosen for how well it removes the deposit. It should also be chosen for what it does to the screen, because a screen can survive a great deal of process fluid and then be destroyed by its own cleaning.
Methods, from gentle to aggressive
Rinsing or backwashing. Reverse flow through the mesh. Gentle, effective for loose cake, and harmless to PP. This should always be the first thing tried, and in many processes it is the only thing needed.
Soaking in a compatible solvent or detergent. Effective for greasy and adsorptive deposits. The risk is chemical rather than mechanical – check the agent against PP, and check the temperature.
Ultrasonic cleaning. Very effective and generally safe for PP at moderate power and temperature. Watch for local heating and for damage at the wire crossings if the mesh is already embrittled.
Mechanical scrubbing or brushing. Removes stubborn deposits and abrades the wire surface. Repeated brushing roughens PP, and a roughened surface holds deposit better, so scrubbing can make the next cycle worse.
High-pressure jetting. Fast and effective, and capable of deforming fine mesh outright. If you use it, keep the pressure moderate and the nozzle moving.
Burn-off or thermal cleaning. Not appropriate for PP. It melts.
What damages PP specifically
- Heat. Hot cleaning solutions accelerate oxidation and embrittlement. A screen cleaned at 80 C every cycle ages far faster than the same screen in service.
- Oxidising cleaners. Hypochlorite and similar agents attack PP progressively.
- Solvents that swell it. Some effective degreasers will swell PP and change the aperture.
- Abrasion that roughens the surface and promotes re-fouling.
- Bending. An embrittled screen that is flexed during handling cracks at the crossings.
How to tell when cleaning is doing the damage
Track the number of cycles a screen survives, not just whether it comes clean. If a change in cleaning method restores flow better but halves the cycle count, it is not an improvement. The metric to watch is flow restored per cycle divided by cycles achieved.
Practical suggestions
- Clean before the deposit sets. Frequent gentle cleaning beats infrequent aggressive cleaning, both for flow and for screen life.
- Keep a spare set rotating so screens are cleaned in batches rather than in a hurry.
- Match the agent to the deposit, not to what is on the shelf.
- Rinse thoroughly after cleaning so residues do not go back into the process.
- Handle cleaned screens gently – this is when they are most likely to be brittle.
Deciding between cleaning and replacing
At some point cleaning stops being worth it. The test is not whether the screen can be restored, but how much of its original flow returns and how long that lasts.
Track the clean differential after each cleaning cycle. When a cleaned screen no longer returns to a reasonable fraction of its original clean reading, the deposit is permanent and the screen is finished, however good it looks. Continuing to clean it costs labour and chemicals and delivers a screen that fouls faster each time.
For low-value screens in a high-fouling service, a policy of replacement rather than cleaning is often correct. It feels wasteful and frequently costs less once labour is counted.
What we supply
Our PP filter screens come with welded frames that tolerate normal backwashing and soaking. Tell us your cleaning method and temperature as well as your process conditions, because the cleaning is very often the harsher environment.