Same word, different worlds
Fines
Fines turns up in 5 fields: thermal spray, powder coating, refractories, paper optics, asphalt. Here is what it means to the people in each one.
- 04TsThermal SprayFines in Thermal Spray
Powder particles smaller than the specified size range, which cause buildup, spitting and poor flow. Particles below the bottom of a powder's specified cut. Fines overheat or vaporize in the jet, stick to nozzles, injectors and barrels and break loose as spits, and they make powder clump and flow unevenly. Specs usually cap the fraction under the lower size, and powders that have been recycled, crushed in a feeder or stored damp tend to gain fines.
On the job: This lot is loaded with fines, it's coating the injector every ten minutes, send a sample out for sizing.
- 05PcPowder CoatingFines in Powder Coating
The smallest particles in a powder, roughly under 10 microns, which fluidize, charge and recycle poorly. Most powders are milled to a median size of around 30 to 45 microns. The finest fraction gets carried off by booth airflow, slips past cyclones and accumulates in reclaim, where it clogs hoppers, packs in hoses and causes spitting and impact fusion. A high fines content also hurts transfer efficiency. Shops control fines by blending reclaim with fresh powder and checking particle size when problems start.
On the job: Reclaim's all fines now, the hopper won't fluidize and the guns are spitting every few minutes.
- 07RfRefractories & Furnace LiningsFines in Refractories & Furnace Linings
Smallest particle fraction of a refractory mix, which fills the gaps between coarse grains and forms the bond. The fine end of the particle size distribution, below roughly 0.1 mm, down to micron-sized reactive alumina and microsilica. Fines fill the voids between coarse aggregate, carry most of the bond and set water demand and flow. They are also the first part of the lining slag attacks, because the matrix holds the impurities and porosity. Losing fines through segregation, rebound or careless mixing weakens the installed lining.
On the job: All the fines are sitting on top of that pour, somebody over-vibrated it and it segregated.
- 22PoPaper Optics & TestingFines in Paper Optics & Testing
Fiber fragments and small particles that pass a fine screen and have an outsized effect on sheet optics. Fines are pieces of fiber wall, ray cells and fibrils, usually defined as material passing a 200-mesh screen of about 75 micrometers. Mechanical pulp fines scatter light strongly and drive opacity, while chemical pulp fines from refining tend to bond and reduce scattering. Their retention on the wire also governs two-sidedness, because drainage pulls fines away from the wire side.
On the job: First-pass retention dropped and we lost fines, so opacity on the wire side is down.
- 24AsAsphalt PavingFines in Asphalt Paving
The dust-sized part of the aggregate passing the No. 200 sieve, which stiffens the binder into a mastic. The material finer than 75 microns, also called minus 200 or P200, coming from crushing, from natural sand and from baghouse dust returned to the mix. Fines combine with binder to form a mastic that stiffens the mix, but too many soak up binder, cut VMA and make a mix tender. Superpave controls them with the dust-to-binder ratio, the percent passing No. 200 divided by the effective binder content, usually held between 0.6 and 1.2.
On the job: Fines are up to 6.8 percent and the dust ratio's out, have the plant waste some baghouse dust before the mat starts checking.