Deicing fluid

src: i.ytimg.com

Deicing of landline aircraft is commonly performed on commercial and public flights. The fluid used in this operation is called deicing fluid or anti-icing . Abbreviations ADF (Aircraft Deicing Fluid) or AAF (Aircraft Anti-icing Fluid) are usually used.

Video Deicing fluid

Jenis

Deicing fluids come in different types, and usually consist of ethylene glycol (EG) or propylene glycol (PG), along with other ingredients such as thickening agents, surfactants (wetting agents), corrosion inhibitors, and colored, UV-sensitive dyes. The propylene glycol based fluid is more common due to the fact that it is less toxic than ethylene glycol.

SAE International (formerly known as the Society of Automotive Engineers) issues standards (SAE AMS 1428 and AMS 1424) for four different types of fluid flights:

1. Type I liquid has a low viscosity, and is considered "not thickened". They only provide short-term protection because they quickly flow from the surface after use. They are usually sprayed hot (130-180 Â ° F, 55-80 Â ° C) at high pressure to remove snow, ice, and ice. Usually they are dyed orange to help with identification and application.
2. The type II liquid is pseudoplastic, which means a polymer thickening agent to prevent the direct flow of the plane surface. Usually the liquid film will remain in place until the aircraft reaches 100 knots (190 km/h) or more, at which point the viscosity is damaged by shear stress. The high speed required for viscosity disruption means that this type of liquid is only useful for larger planes. The use of Type II fluid decreases in favor of Type IV. Type II fluids are generally yellow.
3. Fluid type III can be considered as a compromise between Type I and Type II fluids. They are intended for use on slower planes, with rotation speeds of less than 100 knots. Type III fluids are generally yellow.
4. The IV liquid type meets the same AMS standards as the Type II fluid, but they provide longer hold time. They are usually dyed green to assist in the application of a consistent fluid layer.

The International Organization for Standardization issues an equivalent standard (ISO 11074 and ISO 11078), defining the same four types.

Deicing fluids containing thickener (Type II, III, and IV) are also known as anti-icing fluids, as they are used primarily to prevent icing from recurring after initial deicing with Type I fluids.

Maps Deicing fluid

Chemical composition

The main component of the deicing fluid is the freezing depressant (FPD), usually propylene glycol or ethylene glycol. Other materials vary depending on the manufacturer, but the exact composition of a particular liquid brand is generally stored as confidential confidential information.

Based on chemical analysis, the US Environmental Protection Agency has identified five main classes of additives that are widely used among manufacturers:

1. Benzotriazole and substituted benzotriazole, used as a corrosion/retardant fire inhibitor to reduce the combustion capability resulting from the corrosion of metal components carrying direct current.
2. Alkylphenols and alkylphenol ethoxylates, nonionic surfactants used to reduce surface tension.
3. Triethanolamine, used as a pH buffer.
4. High molecular weight, nonlinear polymers, used to enhance viscoelasticity.
5. Color dyes, such as azo, xanthene, triphenyl methane, and antrroquinone, are used to aid identification.

src: r3.aviationpros.com

Usage statistics

The amount of fluid needed to draw an airplane depends on various factors. Deicing of large commercial aircraft typically consumes between 500 US gallons (1,900 L) and 1,000 US gallons (3,800 L) of dilute liquid.

The cost of fluids varies greatly due to market conditions. The number of deicing service firms imposes end users generally in the range of US $ 8 to US $ 12 per gallon diluted (US $ 2.10 to US $ 3.20 per liter).

The total annual use of deicing fluid in the US is estimated at about 25 million US gallons (95,000,000 L), described as follows (figures from 2008, adjusted for total show for non-diluted liquids):

src: c8.alamy.com

Performance measurement

Deicing fluid performance is mainly measured by Holdover Time (HOT), and Lowest Operating Temperature (LOUT).

Holdover Time (HOT) is the length of time a plane can wait after being treated before takeoff. Detention time is affected by dilution fluid, ambient temperature, wind, rainfall, humidity, plane skin, airplane skin temperature, and other factors. If the Foreclosure Time is exceeded, the aircraft must be treated again before taking off.

The Lowest Operational Usage Temperature (LOUT) is the lowest temperature at which de/anti-icing fluid will flow adequately from the critical surface of the aircraft and retain freezing freezing freezing point of 7Ã, Â ° C (13Ã, Â ° F) below outside air temperature (OAT).

In the United States, the Federal Aviation Administration (FAA) issues the Official Time Holdover and the Lowest Operations Temperature table for all approved deicing liquids, and revises it annually.

For Type I fluids, the Suspension Time listed in the FAA table ranges from 1 to 22 minutes, depending on the situational factors mentioned above. For Type IV fluids, Holdover time ranges from 9 minutes to 160 minutes.

src: 50skyshades.com

Dilution

Deicing fluids work best when they are diluted with water. For example, the unfrozen Dow UCAR Deicing Fluid (Type I ethylene glycol) has a freezing point of -28 Â ° C. The water, of course, freezes at 0 Ã, Â ° C. However, 70 percent deick fluid mix and 30 percent water freezes below -55 ° C. This is known as the eutectic concentration, at which the freezing point of the mixture is at its lowest point, and lower than one of the component substances.

Depending on the manufacturer, deicing liquid may be sold in concentrated or pre-diluted formulations. Dilution, if necessary, should be conducted in accordance with weather conditions and manufacturer's instructions to minimize costs while maintaining safety.

Dilution of a particular fluid sample (and therefore freezing point) can easily be confirmed by measuring its refractive index with a refractometer, and looking for results in the deicing fluid preparator table.

src: 4.bp.blogspot.com

Compliance Standard

Manufacturers of flight deicing fluids should certify that their products conform to AMS 1424 and 1428 standards using High Speed ​​Ramp Test, Low Speed ​​Ramp Test, and Water Spray Endurance Test.

The purpose of this standard is to ensure acceptable aerodynamic characteristics of the deicing/anti-icing fluid as it flows from the lifting and control of the plane's surface during the acceleration and climbing of the takeoff soil.

With the development of non-standard de-glycol fluid it develops to overcome additional factors such as corrosion, foaming, thickening, residue formation, slippery, and mold formation.

src: c8.alamy.com

Caution

Repeated application of Type II, Type III or Type IV anti-icing fluids may cause residues to collect in areas of quiet aerodynamics, cavities and crevices. These residues can be rehydrated and freeze under certain temperature changes, in high humidity and/or rain conditions. In addition, they can block or block a critical flight control system.

Appropriate inspection and cleaning programs should be established when using this type of fluid.

src: s-media-cache-ak0.pinimg.com

Environmental impact

Ethylene glycol and propylene glycol are known to exert high levels of biochemical oxygen demand (BOD) during degradation at the water surface. A large amount of dissolved oxygen (DO) in the water column is consumed when the microbial population decomposes propylene glycol. This process can affect other aquatic life by consuming the oxygen needed for their survival.

Thickened liquids typically use alkylphenol ethoxylate (APE) surfactants, biodegradable products that have been shown to be endocrine disruptors, and thus are banned in Europe and are under EPA control in the US A number of liquids also use benzyltriazole or tolyrriazole corrosion. inhibitors, which are toxic and non-biodegradable and thus persist in the environment.

Because this environmental impact study is underway to find less problematic alternatives. This proves challenging because of many performance and security factors to consider.

At least one FAE approved the deicing fluid (Kilfrost DF Sustain) now using 1,3-propanediol (corn fermented product) as the freezing deposition instead of ethylene glycol or propylene glycol.

Other strategies may be used to minimize the environmental impact of deicing fluids such as collecting the fluid used and using maximum dilution consistent with safety.

src: c8.alamy.com

See also

• De-es (chemicals and other de-icing methods)

src: aircrafticing.grc.nasa.gov

References

Source of the article : Wikipedia