Why do wire fragments appear downstream of my filter?

The symptom

Fine wires or mesh fragments appear in downstream strainers and product samples. They may also reach pumps and nozzles. Filtration can appear to work while the damaged area allows increasing quantities of particles through.

Root causes

1. 01 Unsupported fine cloth flexes under pulsating pressure. Wires can work-harden at the crossings and eventually break. This is a mechanical form of media migration.
2. 02 An incorrect or missing support layer leaves the fine cloth spanning gaps that are too large. The fine wires then carry the structural load as well.
3. 03 Vibration from pumps or valves can load the element if its mounting was designed only for static conditions.
4. 04 Aggressive manual cleaning or excessive backflush pressure can deform the weave locally. These damaged areas may subsequently fail.

Suitable filter media

• ▸ Consider a sintered laminate. Bonded wire crossings limit wires working loose. The lay-up must suit the pressure cycles and cleaning conditions.
• ▸ If single cloth is required, size a welded or coarse woven backing for the permissible span of the fine layer.
• ▸ Composite screens mechanically bond fine cloth to a welded grid. The combination can support the fine layer under pulsating loads.
• ▸ Review the cleaning procedure together with the medium. Include retention rating, backflush pressure and cleaning method in the same specification.

Prevention

• ⊕ Investigate any wire fragments found downstream. Further damage can increase migration.
• ⊕ Include pulsation and vibration in the enquiry alongside the required retention rating.
• ⊕ Inspect elements after every cleaning cycle, especially at clamped edges and weld seams where damage may start.