There are several ways to control frazil ice build up. They include suppression, mechanical control, thermal control, vibration, materials selection and damage mitigation.
Suppression Frazil ice forms in supercooled water which occurs because the surface water loses heat to cooler air above. Suppression is the idea of insulating the surface water with an intact, stable ice cover. The ice cover will prevent heat loss and warm the supercooled water that might have already formed. Sufficient area needs to be covered in order for this method to work, but it is still unknown what is meant by "sufficient". The
St. Lawrence River is explicitly managed to create "flow conditions that help form a stable ice cover" to prevent frazil ice and subsequent
ice jams.
Mechanical control These methods include stabilizing freeze without restricting water flow, such as implementing
weirs and ice booms, installing
water jets to break up any accumulation that might occur, and using manual labour to rake away the accumulation. This final method is often not preferred because of high labour costs, cold, wet and late night working conditions. Back flushing is another technology that uses the idea of cancelling out the differential pressure caused by the frazil ice accumulation. This technology creates a high pressure on the downstream side of objects to reverse the differential pressure.
Thermal control These methods either heat the structures in the water to prevent frazil ice adhesion or heat the water to prevent frazil ice from forming in the first place. When heating the structure, it must be heated to a temperature above freezing. Electrical
resistance heaters have been found to work well, but these have potential safety problems. Installing hollow tubes in the structures through which steam or warm water is pumped also works, but this method has been judged as uneconomical to operate.
Vibration Although still in the experimental stages, blasting with
dynamite is one form of vibrational control that will break loose any frazil ice accumulation. The charge must be precise such that the ice breaks, but surrounding structures and environment are not harmed. Safety of the blasting also is important and nearby residents might complain about sound pollution. For all these reasons, this method is not often used, except as an emergency last resort.
Materials selection Man-made structures are often the objects to which frazil ice adheres. As such, the choice of materials for these structures should include consideration of ice
adhesion.
Steel structures, for example will
rust, and rust-to-ice adhesion is very strong. Choosing a material with lower adhesion such as
plastic,
fiberglass,
graphite or even an
epoxy paint coating on the steel will reduce the adhesion probability. Although adhesion will still occur, using such materials makes other methods, such as raking, easier.
Damage mitigation Damage could be reduced by protecting designated flood regions with mechanical structures. ==See also==