A failed screen is a piece of diagnostic evidence, and it is usually thrown away before anyone reads it. Where it broke, and how, points at a specific cause – and the causes need very different responses.
Torn mesh in the middle
A hole or tear in the body of the mesh points at either a pressure event or mechanical damage. A sudden differential spike – a valve opening, a pump start, a blockage clearing – can exceed what the mesh can take. So can a foreign object arriving with the flow.
Look at the edges of the tear. A ragged, stretched tear suggests overload. A clean cut suggests something sharp passed through. If the mesh is otherwise clean, the failure was an event rather than a slow process.
Deformation without tearing
A screen that is dished in the direction of flow but intact has been loaded beyond its stiffness, not its strength. The usual causes are insufficient support spacing, higher differential than the screen was specified for, or temperature high enough that the material softened and crept.
This is the failure that says “the specification was wrong” rather than “something happened”. The fix is more support or a heavier gauge, and adding a support rib is almost always cheaper than upgrading the mesh.
Failure at the frame
Separation at the edge, or cracking where the mesh meets the frame, points at the joint. Causes include differential expansion between frame and mesh, fatigue from cyclic loading, a weld or bond that was never adequate, or handling damage during installation.
Because the frame carries load into a small area, this is where most screens fail even though attention is always on the mesh. If you see a pattern of frame failures, the joint design is the problem rather than the mesh.
Blinding rather than breaking
A screen that is intact but will not pass flow has not failed structurally – it has fouled. This is covered in our article on blinding and clogging, and it needs a different response again: change the load, the velocity or the cleaning method rather than the screen’s strength.
Corrosion, swelling or discolouration
A screen that has changed colour, swelled, softened or become brittle has been attacked chemically. The pattern often starts where the material is stressed – at the frame, at wire crossings, at the clamp line – because chemical attack and stress interact.
The two questions to ask: what is in the stream, and at what temperature. Temperature multiplies attack, and cleaning agents count as part of the exposure. A screen that fails in months rather than years usually has a chemistry problem rather than a mechanical one.
Failure right at change-out
A screen that tears as it is removed or as a new one is installed has not failed in service. It was damaged by handling, usually because it was already embrittled by age or chemistry, or because it was levered out rather than lifted.
This is worth separating from service failure, because it inflates the apparent failure rate and hides the real cause. Record it separately.
Recording it properly
Four data points per failure, and after twenty you will know your system:
- Where it failed – body, edge, frame, seal
- How – torn, dished, cracked, fouled, discoloured
- Service life – hours or volume since installation
- Conditions at failure – differential, temperature, and anything unusual that day
A photograph attached to the record is worth more than a description. After a few months, patterns appear that no single failure reveals.
What we can do
We supply PP filter screens and will read a failure for you – send us the screen as it came out and a photograph of the housing, and we can usually tell you whether the cause is strength, chemistry, support or handling. If it is a specification problem we will say so rather than sell you a heavier screen that does not address it.