Fouling
- Also known as
- biofouling, deposit fouling
Fouling is the unwanted buildup of deposits on surfaces in contact with water or process fluids, such as heat exchangers, pipes, membranes and cooling towers. Deposits can be mineral scale, suspended solids, corrosion products, organic material or biological growth.
What is fouling?
Fouling is the accumulation of material on a surface where it does not belong. It is one of the most common and costly problems in industrial water and process systems, affecting cooling towers, boilers, heat exchangers, reverse osmosis membranes, pipelines and oilfield equipment.
Types of fouling
| Type | What deposits |
|---|---|
| Scaling | Mineral scale that crystallizes from the water, such as calcium carbonate |
| Particulate fouling | Silt, clay, corrosion products and other suspended solids that settle out |
| Corrosion fouling | Oxides and other products of metal corrosion |
| Biofouling | Biofilms of bacteria, algae and fungi, and the slime they produce |
| Organic and oil fouling | Oils, greases, paraffins and other organic material |
Different types often occur together. Biofilms trap particles, deposits shelter corrosion, and scale builds on rough, fouled surfaces.
Effects of fouling
- Lost heat transfer. Deposits insulate heat exchange surfaces, reducing efficiency and raising energy use.
- Higher pressure drop and lower flow in pipes, exchangers and membranes.
- Corrosion under deposits, where conditions beneath the fouling layer attack metal.
- Downtime and cleaning costs.
How fouling is controlled
- Chemical treatment: scale inhibitors, dispersants that keep particles suspended, corrosion inhibitors and biocides.
- Water management: pretreatment, filtration and controlling how concentrated the water becomes, as in cooling tower blowdown.
- Design and operation: flow velocities and temperatures that discourage deposition.
- Cleaning: mechanical, chemical or high-pressure cleaning when deposits build up.
Fouling and Locus biosurfactants
Locus supplies its Amphi biosurfactants to water treatment formulators as components of deposit control and dispersion packages for industrial water systems.
Frequently asked questions
Scaling is one type of fouling, caused by minerals crystallizing from the water. Fouling is the broader term for any unwanted deposit, including solids, corrosion products, organic material and biological growth.
Biofouling is the buildup of microorganisms and the slimy biofilm they produce on surfaces. It reduces heat transfer and flow, and can drive corrosion.
Sources
- Cooling water and heat exchanger fouling references, AMPP (Association for Materials Protection and Performance)
- Industrial water treatment guidance, U.S. Department of Energy, Federal Energy Management Program