Ask a plant how many different filter screens it holds and the answer is usually a surprise. Each one was specified for a reason at the time, and over years the catalogue grows until the stores hold dozens of variants that differ marginally and are indistinguishable on a shelf.
What the sprawl costs
- Wrong-part fitting. A slightly coarser screen in the wrong housing passes material for weeks before anyone notices. This is the expensive one.
- Spares holding. More variants means more stock of each, or a stockout on the one you need.
- Worse buying position. Small quantities across many specifications cost more per unit than a consolidated order.
- Unclear responsibility. With dozens of variants, nobody can hold the whole picture.
- Slower change-outs. Finding the right screen takes longer than fitting it.
Building the catalogue
The method is straightforward, though it takes a few weeks.
Survey every housing. Record the seat dimensions, the retention method, the seal type, the flow direction and the current screen aperture. Photograph each one.
Group them. Most plants find that the housings fall into a small number of families – often three or four – within which the screens are interchangeable.
Challenge each aperture. For each, ask what the screen is protecting and what it is actually removing. A significant number will turn out to be at an aperture that nobody chose deliberately – it was what was available or what the last supplier offered.
Consolidate. Within each family, reduce to the smallest set of apertures that satisfies the duties. Where two duties are close, pick the finer and accept the shorter interval – or the coarser, if the finer is not actually needed.
Code them. Give each remaining variant a clear code that includes the family and the aperture, and mark it permanently on the frame. A screen with no marking is a screen that will be misfiled.
What the consolidation gives up
Be honest about this, because it is where standardisation projects fail. A housing that gets a slightly finer aperture than ideal will need changing more often. One that gets slightly coarser may allow marginally more material through.
In most processes both effects are small and the reduction in misfitting more than compensates. In a process where the separation is genuinely critical, that housing keeps its own specification and is worth documenting as an exception.
Making it stick
- A single owner for the screen specification list.
- Shelf labelling by code, not by description.
- A rule that a new variant needs a reason recorded. This is the part that stops the catalogue growing back.
- Permanent marking on the frame, so a screen found loose can be identified.
Where the saving actually is
Not in the purchase price – screens are a small line item. The saving is in misfits, in stockouts, in change-out time and in the engineering attention that goes into managing a long list. Those are larger than they look, and they are the reason to do it. It is the same argument that applies to verifying whether a screen is clean: the value is in the interval and the misfits, not in the unit price.
What we can do
We supply PP filter screens with permanent aperture and family marking on the frame, and we can work from a survey of your housings to propose a consolidated range. Send us the measurements and photographs and we will tell you how few variants would cover your plant.