We usually start thinking about freeze protection measures as the cold temperatures of winter get closer. However, others don’t worry this until it’s too late, and they have to cope with a frozen or damaged water line. People that work in regions where extreme weather conditions are the norm, can’t leave proper preparation up to chance. They make sure that their personnel and equipment is protected at all times and year-round.
In recent years, (sub-)arctic activities have increased substantially in oil and gas, marine transport, fishing, science and research and tourism industries. Due to their geographic location, these activities hold a high risk while they cope with extreme conditions, such as sub-zero temperatures, limited amounts of daylight and their remote operating environment. As a consequence, the demand for winterized vessels with a minimum of ice reinforcement is increasing.
International standards provide guidance to manufacturers and operators of this type of equipment. Recent updates of these standards provide design principles for mobile units and offshore installations intended for cold-climate conditions. DNVGL-OS-A201 is one of the most comprehensive and followed set of principles in the world and helps guide the rationale and intent for various aspects of winterization.
Winterization requirements can be broken into two classes:
- Anti-icing is the prevention of ice formation. Anti-icing requirements are generally related to personnel safety. They include emergency passageways, helidecks, and emergency doorways. These areas must be kept free of ice for a possible evacuation during the worst expected conditions.
- De-icing is the removal of ice from an area. De-icing requirements aim to prevent excessive ice loading on frequently used access ways, such as the lower deck, stairs, handrails or walkways.
Since anti-icing and de-icing measures can vary greatly with environmental conditions, it is important to define specific winterization temperature conditions.
There are active and passive methods for anti-icing and de-icing, including: steam, electric heat tracing, hot water, infrared radiation, chemical freezing point depressants, ice-phobic coatings and mechanical methods.
Mechanical methods require steam hoses, shovels, hammers and elbow grease to remove ice. While this approach can be effective, it is not practical when ice needs to be removed from a large area of a vessel. Furthermore, such manual methods put personnel at risk, exposing them to hypothermia.
Electric heat tracing has been used for both anti-icing and de-icing for many years. It has proven to be effective and reliable for a wide range of applications including walkways, handrails, stairs, helidecks, and many more.