Compact sludge dewatering bag for existing boxes and baskets: WINKLER F-BAG Classic

A compact sludge dewatering bag for boxes, baskets and frames you already own

F-BAG is our name for the sludge dewatering bags and filter bags we make in Werther, Germany. The Classic is the flat, compact member of that family: a light disposable filter bag made from thermally bonded polypropylene nonwoven. It weighs around 0.17 kg, measures 1.19 by 0.55 metres and opens to roughly 0.53 metres across.

That makes it a different product from the free-standing, volume-rated bags in sizes M to XXL. The Classic does not stand up on its own, it carries no stated working load, and it is not a cheaper substitute for a bag rated at 400 or 900 kg. What it does instead is sit inside a dewatering box, a basket, a mesh frame or any similar holder you already have on site, and take the sludge that would otherwise go into the holder directly.

When a compact sludge filter bag is the right choice

The Classic earns its place when three conditions come together. Sludge arrives in manageable quantities rather than by the cubic metre. There is a holder that supports the bag. And the changeover needs to be quick, without building up a new free-standing bag every time.

That describes a workshop with a fixed cleaning station, a sink with a sludge trap, a small treatment skid, or any bench where a box or basket takes the bag. If you need the bag itself to stand on a yard or a building site, the free-standing 0.125 m³ size is the smallest one that will do it. It stands unsupported, has lifting loops and is rated to 400 kg.

Nominal 100 µm: what the figure actually tells you

A nominal filtration rating of 100 µm is documented for the Classic. Nominal means the figure describes how the nonwoven was designed, not a sharp cut-off. Finer particles can pass at the start and are often retained only once a first layer of solids has formed inside the bag.

If you are working with a sludge you have not handled before, running a few bags from the pack is the fastest way to answer the question of whether the fineness suits you. The process behind it, from filling to filter cake to removal, is described in the process guide.

The documented air permeability of 500 l/dm²/min at 200 Pa describes flat material on a test rig. It is a material figure that lets you compare one nonwoven with another. It does not tell you how quickly a filled bag will shed water, because that depends on solids content, particle shape and how the cake builds.

A disposable sludge filter bag supplied in packs of 25

The Classic is a consumable. Disposable sludge filter bags of this kind are bought by the pack, and one pack contains 25. That quantity is deliberate: in most operations it covers several weeks, which turns a bag change into a two-minute job rather than a purchase order. After dewatering, bag and contents are disposed of together according to how your sludge is classified. The material is not designed to be washed out and used again.

Technical data, F-BAG Classic

Classic or the 0.125 m³ bag? The decision in one sentence

If you have a holder and the bag only needs to hang inside it, take the Classic. If the bag has to stand up, be filled where it stands and then be lifted by its loops, you need size M or larger. Which size suits which batch quantity is covered in the size guide.

Questions we are asked about the compact filter bag

Almost every question about the Classic comes back to the same point: how it differs from the free-standing bags.

Can I stand the Classic up and fill it from above?

No. The bag is made flat and has no base construction that would carry a filling load while standing. It belongs in a box, basket or frame. For free-standing dewatering, size M is the smallest suitable version.

Does the Classic fit the WINKLER dewatering box?

The dewatering box has internal dimensions of 57 × 37 × 30.5 cm and is designed around the two PP spunbond nonwovens for paint sludge. Whether the Classic fits your particular holder depends on the internal dimensions and on the rim it rests over. Send us the measurements and we will tell you what fits.

How many bags will one batch use?

That depends on solids content, so there is no general answer. A workable approach: dewater one batch in one bag, weigh the result, scale up. A pack of 25 makes that test inexpensive.

Is the nonwoven resistant to acids and alkalis?

Polypropylene is used in a wide range of aqueous process media. Whether your specific medium is suitable, at your concentration, temperature and contact time, is something we check before you order. Tell us the medium, the concentration, the temperature and the contact time and we will assess it for your case.

Can I wash the bag out and use it again?

No. The Classic is a single-use product. After use the solids sit inside the nonwoven structure, and the material cannot be cleaned back to its original condition.

Not sure which version you need?

If you are unsure whether bag size, fineness and holder fit together, we will work through it with you before you order. It helps to have the type of sludge, the quantity per batch, the holder you are using and its internal dimensions to hand.