Что означает def над знаком равно
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Что означает def над знаком равно

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What Is DEF? (Diesel Exhaust Fluid)

DEF, an acronym for Diesel Exhaust Fluid, is the trucking industry’s response to U.S. Environmental Protection Agency standards requiring all medium and heavy-duty diesel vehicles to significantly reduce engine emissions, particularly nitrous oxide as well as particulate matter. It was mandated to come into use beginning with 2010-manufactured engines.

DEF is a clear, colorless, non-hazardous liquid looking exactly like water but that has a slight odor of ammonia. It is composed of urea and deionized water. The urea component is an organic compound made up of nitrogen, hydrogen, carbon and oxygen.

How DEF Works

DEF is not a fuel additive, and has no influence on the tuning and efficiency of diesel engines. The way it works is that the fluid, an organic compound comprising urea and deionized water, is mixed with the hot gases that follow diesel combustion, breaking DEF down into ammonia and carbon dioxide. These two gases meet with the diesel exhaust and chemically bond with the nitrogen oxides, thus resulting in nitrogen and water exiting the tailpipe. The end result is a much cleaner diesel exhaust.

Video: How DEF Works

Do Not Pee In In Your DEF Tank!

Video: The Chemistry Of DEF

In the early days of DEF use there was talk that because DEF contains urea, and because urine contains urea it was only logical that DEF was made up of horse urine … or cat urine, or pig urine, you get the picture. Some even took it to the «logical» extreme of suggesting that all an enterprising truck driver had to do was pee into his DEF tank. Problem solved, and cheaper.

While urea definitely is a component of both urine and DEF, the manufacture of DEF is done under exacting conditions making sure the urea is pure and free of contamination, and of the right ratio to the deionized water. The water also must be of an exact quality.

«Human urine is an aqueous solution of greater than 95 percent water, with the remaining constituents, in order of decreasing concentration urea 9.3 grams/L, chloride 1.87 grams/L, sodium 1.17 grams/L, potassium 0.750 grams/L, creatinine 0.670 grams/L and other dissolved ions, inorganic and organic compounds.»

On the other hand, «Diesel Exhaust Fluid uses automotive grade urea, at 32.5 percent concentration. This urea contains , 0.3 percent Biuret maximum, 0.5 jpercent magnesium max , 0.5 percent calcium max, 0.5 percent phosphate max, 0.5 percent iron max, and 0.5 percent potassium maximum.»

That should settle that; don’t pee into your DEF tank unless you would like to expend several thousand dollars in repairs to your vehicle.

How Is DEF Implemented in Diesel Engines?

The trucking industry, particularly the manufacturers of heavy-duty diesel engines, began to meet EPA standards by redesigning engines with a selective catalytic reduction technology. The DEF is sprayed into the exhaust as an after-treatment process; which means that it destroys harmful emissions after combustion, thus giving manufacturers the ability to tune engines to improve fuel efficiency and increase power.

It is said that owners of SCR vehicles experience greater reliability, longer oil change intervals, and cheaper operating costs over the life of the vehicle.

Who Regulates DEF?

The production, handling and transportation of DEF are governed by the Environmental Protection Agency through its ISO 22241 standard. The urea concentration of DEF must by 32.5 percent by weight; which was mandated because that concentration has the lowest freezing temperature of 12 degrees Fahrenheit.

Can DEF Harm Your Engine?

The only harm to an engine would be to the SCR system’s injectors and catalysts if the fluid is contaminated. That’s why there are maximum levels of impurities permitted in DEF.

Is DEF a Hazardous Material?

No. It is not necessary to wear protective clothing when handling DEF. The only concern from getting on clothing, for example, is that DEF might leave a stain. Simply rinse it off with water as soon as possible. If you spill a small amount of DEF, it can be washed away with water or wiped up. If you leave it to dry it will turn into white crystals. These can be washed away with water.

That being said, DEF should not be swallowed. If ingested, a physician should be consulted immediately.

As to inhaling DEF, under normal conditions of use, inhalation is not expected. However, when pumping DEF in a closed area it is possible that inhalation of a small quantity of ammonia fumes from DEF might occur. If you do inhale these fumes from DEF, move to an area of fresh air. A physician should be consulted if you experience any continued symptoms, such as irritation to nose or throat. DEF does sometimes have a slight ammonia smell (similar to home cleaning agents), but these are not harmful.

How Do I Store DEF?

DEF requires care in storage. For example, DEF is corrosive to many materials, including carbon steel, copper, nickel, epoxy resins and aluminum. The main issue with incorrect storage is that the DEF may become contaminated by leaching from the materials and cause failure with the SCR system, meaning the whole batch of improperly stored DEF would be useless.

Temperature is also a concern with storage of DEF; which has a limited shelf life depending on the temperature. Storing DEF at 80 degrees will reduce its shelf life to just 12 months while keeping it at 60 degrees can extend its usability to 36 months!

Recommended handling and storage containers for DEF include titanium, rubber, plastic, and stainless steel. It is recommended to only use chemical equipment when handling DEF, as petroleum equipment can contain unknown residue. Also, DEF requires dedicated equipment. A tank that has previously held any other product will contaminate DEF.

How Will I Know If DEF Has Gone Bad?

Since DEF should always remain the same color, basically like clear water, any change from this should alert a driver that the fluid in his DEF tank has become contaminated. And, once contaminated, the DEF cannot be restored or reconstituted. Importantly, DEF is not susceptible to freezing and thawing. Within the parameters of the temperature ranges for storage longevity, freezing DEF does no harm to it.

What Does DEF Cost?

Like most truck expenses, the price of DEF depends on location, time of year, and availability. At the truck center fuel island, DEF will run cheaper than the diesel fuel price. As of this writing, October 2018, DEF is running about $2.799 to $2.859 per gallon, compared to diesel fuel’s $3.459 to $3.899 price.

Truck terminals can purchase their DEF in bulk volume in drums or totes and save about 30 percent over the truck center prices.

How Much DEF Will a Truck Consume?

DEF consumption is expected to be approximately 2 percent of fuel consumption, depending on vehicle operation, duty cycle, geography, load ratings, etc. Since DEF consumption is directly related to fuel consumption, a truck averaging 6 MPG can expect to go approximately 300 miles on one gallon of DEF.

DEF weighs about 9 pounds per gallon.

Can I Make My Own DEF?

It is not recommend that drivers make DEF themselves. DEF has strict requirements for maintaining concentration and purity of ingredients that is critical to the proper functioning and longevity of the SCR system.

Cummins and other OEMs require that DEF used with their SCR systems meet all ISO22241 specifications as well as API certification requirements. It is recommended that end users purchase certified DEF and avoid blending it themselves.

For more information about the quality standards, refer to ISO 22241 which details specifications for DEF quality, handling, testing, transportation storage, and refilling.

What If My Truck Runs Out Of DEF?

The EPA has taken into consideration the possibility that a driver of a DEF-equipped truck might choose to run without having to be encumbered by the extra expense and trouble of having to keep his DEF tank filled. Vehicle manufactures have built-in DEF level warnings with the added incentive that the vehicle will fail to operate properly without DEF.

Basically, before a truck’s DEF tank runs empty drivers are given a series of alerts on their dashboard displays (much the same way as if they were running low on diesel). Generally speaking, when the DEF tank level drops below 10 percent an amber warning lamp will come on, at 5 percent this lamp starts flashing and below 2.5 percent a solid amber warning light is displayed.

If the truck is allowed to run out of DEF the engine’s power is reduced, a solid red warning will be displayed and the vehicle speed will be limited to 5 mph until the DEF tank is refilled.

Are There Any Other Dangers Associated With DEF?

One concern expressed by some is the possibility of inadvertently putting DEF into the diesel tank, or vice versa. A number of safeguards are in place to prevent that happening.

The standard nozzle diameter for DEF is 0.75 inches, compared to 0.87 inches for diesel, preventing the diesel nozzle from ever being inserted into the DEF tank. In addition, the filling cap for the DEF tank is blue and is clearly marked «Diesel Exhaust Fluid» with the accompanying ISO standard number.

However, mixups have happened. In a small number of cases diesel has been put into the DEF tank. Diesel is less dense than DEF and will float on top of the DEF in the tank. But even small amounts of diesel can damage the SCR system and it is recommended to contact your dealer immediately, and do not drive the vehicle.

If DEF is filled into the diesel tank, the engine will stop running almost immediately, and the vehicle will need to be taken to a service center for repair.


A facility where trucking companies operate out of, or their «home base» if you will. A lot of major companies have multiple terminals around the country which usually consist of the main office building, a drop lot for trailers, and sometimes a repair shop and wash facilities.


Hours Of Service

HOS refers to the logbook hours of service regulations.


When a violation by either a driver or company is confirmed, an out-of-service order removes either the driver or the vehicle from the roadway until the violation is corrected.

20 Facts You Need To Know About Diesel Exhaust Fluid (DEF)

Diesel Exhaust Fluid Information

The Environmental Protection Agency was created in the footsteps of the Clean Air Act of 1970. For 46 years the EPA has been constantly evolving and enacting laws to address the environmental needs of this country. For many years owners of three-quarter and one-ton light duty pickup trucks enjoyed no additional smog equipment on their vehicles. All of that changed in 2008 with the EPA required the use of diesel particulate filters on all three-quarter-ton and larger trucks as well as required biannual smog tests which included a visual inspection of the vehicle to make sure the DPF parts were still on the truck. In 2010 the regulations got even tighter.

Many thought that the era of big power and torque were over and vowed to never purchase a new truck ever again. However, something spectacular happened and the complete opposite thing occurred. It turns out that Americans truly do adapt and overcome. Every one of the manufacturers figured out a way to cut down on the NOx levels all the while making more horsepower and torque than ever before. Innovation is bread out of strife.

The engineering breakthrough came through the use of the selective catalytic reduction. The vast majority of these systems use diesel exhaust fluid (mixture of urea and deionized water) sprayed into the exhaust system to break down the generated NOx into harmless nitrogen and water molecules. Since the DEF (Diesel Exhaust Fluid) is introduced in the exhaust, also called after-treatment technology, the manufacturer is free to build as much power as they want. The DEF is stored in a separate tank which is insulated and heated and is marked by a blue filler cap.

Still there are two factions of diesel guys out there; those who have accepted to the EPA changes and those who are still vehemently against any regulations whatsoever despite the work around technological advancements. For those not willing to accept the changes there has been a shift to older used diesel engines or remanufactured diesel engines that have been grandfathered in. This article aims to go over the cold hard facts about DEF and educate the populace into making smarter diesel operator decisions.

1. What exactly is Diesel Exhaust Fluid (DEF)?

From a strictly chemical disposition DEF is a mixture of 67.5% deionized water and 32.5% urea. Urea is a compound in Nitrogen that turns to ammonia when heated and is used in a variety of industries. Urea is technically derived from a byproduct of urine but for mass production purposes it is synthetically made. Most DEF products are regulated by the American Petroleum Institute. Lets take a look at the science behind DEF when mixed with exhaust. Chemically, DEF is firstly comprised of (NH2)2CO; and when injected into the hot exhaust gas the water evaporates leaving ammonia and isocyanic acid.

STEP 1: DEF Becomes Ammonia and Isocyanic Acid: (NH2)2CO → NH3 + HNCO

STEP 2: The Isocyanic Acid chemically breaks down with water into Carbon Dioxide and Ammonia:
HNCO + H2O → CO2 + NH3 overall which is this: (NH2)2CO + H2O → 2NH3 + CO2

STEP 3: At this point during the chemical reaction Ammonia will, in the presence of oxygen and a catalyst, will reduce nitrogen oxides:
2NO + 2NH3 + ½O2 -> 2N2 + 3H2O and 3NO2 + 4NH3 -> 7/2N2 + 6H2O

STEP 4: The overall reduction of NOx by urea is:
2(NH2)2CO + 4NO + O2 → 4N2 + 4H2O + 2CO2 and 2(NH2) 2CO + 3NO2 -> 7/2N2 + 4H2O + 2CO2

2. How Often Do You Need To Fill Up the DEF Tank?

Diesel Exhaust Fluid Information

That question specifically depends on miles per gallon and usage of the diesel truck in question. No matter how heavy the load, according to the OE manufacturer, the typical average light duty truck will consume 2-3 gallons of DEF per 800 miles. However, most new trucks with an average miles per gallon rating of 20+mpg will go roughly 8,000-10,000 miles on a tank full (10 gallons) of DPF. Each truck is different, for example on a Dodge Ram there is a gauge readout of exactly how much DEF is left in the tank, GM has a digital readout and Ford has a simple low DEF light.

Medium Duty and Heavy Duty Fuel models will vary but according to Cummins Filtration DEF consumption will be approximately 2% of the fuel consumed. For every 50 gallons of diesel fuel burned you will use 1 gallon of DEF. Here are some Medium and Heavy Duty Consumption projections by our friends over at Cummins Filtration:

Diesel Exhaust Fluid Chart

3. Where can you buy DEF?

Diesel Exhaust Fluid Information

Don’t be fooled into thinking you can buy DEF just anywhere. DEF is mostly sold at truck stops in big jugs containing multiple gallons of the stuff. Some gas stations will carry DEF but don’t count on it if you are in a pickle. It is important to understand if you don’t refill an empty DEF tank the engine will automatically shut down. You don’t want to be stranded somewhere with an empty DEF tank because it is not sold everywhere. Common places to buy DEF include TravelCenters of America, Walmart, Target, Love’s Travel Shop, SAPP Brothers, Flying J Truck Stops, Petro Stopping Centers and Pilot Travel Centers, O’Reilly’s, NAPA and Advanced Auto. We have also compiled a list of the most popular manufactures of DEF here.

4. What are the Pros and Cons of a DEF Truck?

There are very few cons with DEF as it is a fairly simple procedure to deal with. However when it comes to Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) there can be many maintenance and repair issues since they prone to clogging. These systems are complicated in design and a simple clogged filter can cause pressure and temperature differentials that can affect the whole performance of the engine.

The only cons to DEF include the additional upfront cost to the truck, added nominal weight and some additional room to store an extra gallon of the fluid. The pros are better fuel economy, increased horsepower, more optimized combustion, fewer regenerations issues, less wear on the engine and in addition it only releases nitrogen and water vapor into the air.

5. Is emissions production really an important issue?

Diesel Exhaust Fluid Information

Whether it is a big deal or not is not really not up for debate considering all 2008 light-medium diesel and up have to comply with the EPA Regulations. NOx has been blamed for smog, a rise in greenhouse gasses and acid rain. The DEF as part of the Selective Catalytic Reduction system (SCR) turns NOx into pure nitrogen and water vapor. Climate change is a heated debate but we can all agree that spewing more gasses of any kind into the environment isn’t something we need more of.

6. Will DEF Lower My Fuel Mileage?

It is only natural to think that any EPA induced changes to the diesel engine is necessarily a bad one however it is quite the contrary. The major diesel manufacturers discovered it can fine tune the engine anyway it deems fit then allow the SRC and DEF to remove the particulate. The engines are built with performance in mind first and then the SRC, DPF and DEF remove what is needed as an afterthought. Manufacturers have found that engines containing SCR technology oftentimes get better fuel mileage compared with other smog reduction internal systems. Fuel mixed in with the SCR finds an added source of elements to burn. Fuel mileage can be improved by as much as 5%-7%

7. Has this new DEF Technology Ever Been Used Before?

Diesel Exhaust Fluid Information

DEF technology has been used for decades in the country in agriculture, industrial and large scale power generation applications. The concept is the same across the board: the urea mixed with heat creates ammonia that causes a chemical reaction that reduces NOx by 70%-95%. In fact 90% of urea production is used as nitrogen-released fertilizer. It is important to note that automotive-grade urea is of a much higher grade purity than fertilizer urea. If a lower grade fertilizer urea is used in automotive engines you risk disintegration of the SCR and possible ruin the engine. It may even trigger ECM sensors to incorrectly prompt a DEF Tank Empty warning.

8. Does DEF Evaporate After A Period of Disuse?

The answer is yes and no. The temperature at which DEF combines with NOx exhaust right out of the cylinder head with the valves wide open is between 1400-1600 F. The chemical reaction takes place at much hotter temperatures than on a hot sunny day. For example it would take over two years a constant rate of 125 degrees F for the DPF to turn into ammonia and evaporate. However any temperature over 86 F you risk some evaporation due to DEF being almost 2/3 water. You don’t have to worry about a gallon or two of the stuff turning bad or evaporating from disuse unless exposed to consistent hot climates.

9. Is DEF a Toxic and Harmful Chemical?

The active ingredient in DEF, urea, has been chemically synthesized since 1828 first by German scientist Friedrich Wöhler after treating silver cyanate with ammonium chloride. Urea was first discovered in urine by Dutch chemist Herman Boerhaave in 1727. Urea is mostly used in fertilizer for agricultural but also found the chemical industry, explosives, lotions, skin creams, hair removers, plastics, dish soaps and power fuel cells. Urea and consequently DEF is not overly toxic to humans. Urea can be irritating to eyes, skin and the respiratory tract but not life threatening. High concentrations in the blood can be damaging to humans however ingestion of low concentrations of urea ,given an adequate water ingestion of water, are not harmful. In nature urea can cause algal booms which when decomposes above its heating or melting point can cause toxic gases. Mixed with certain oxidants, chlorides, nitrites can cause fire or even explosions.

10. What happens to the engine if the DEF Tank is empty?

Diesel Exhaust Fluid Information

All diesel engine manufacturersare now required by the EPA to integrate some tiered warning system (internal gauges on the dash) to let the driver know exactly how close to empty the DEF tank is. If you ignore the DEF warning the truck will cease to work. Some diesel engine manufacturers allow the engine to go into reduced power mode so the truck can “limp home” or limit the number of times you can turn the engine over. At some point though the diesel engine will not start. Treat the DEF tank just like you would the fuel tank; you don’t want to end up stranded somewhere because you didn’t refill the DEF tank.

11. Does DEF Have a Low Freeze Point?

The standard 32.5% solution of DEF will begin go crystallize and freeze at 12 F. The Urea and water in DEF, when mixed, will freeze at the same rate. This is beneficial to the user because when the fluid thaws the DEF solution does not become diluted or overly concentrated. Freezing and thawing cycles has no impact on the grade of the product. DEF expands when frozen as much as 6.5% — 7% by volume. The packaging allows for leeway for freezing periods.

12. What is the best method to keep DEF from freezing?

Diesel Exhaust Fluid Information

It is perfectly safe to keep a gallon or two of DEF in your vehicle however it is not advisable. DEF will start to decompose at 86 F. It is very easy to forget about the DEF sitting in the back of your truck and given an extended period of hot days the fluid can become unstable and decompose but at a very minimal rate. A diluted DEF without the mixture of 32.5% urea can be damaging to DEF and SCR but cases of that happening are rare. Consequently DEF will freeze in the DEF tank on extremely cold days below 12 F. That is perfectly normal and will not hurt the engine. The SCR systems are designed to provide heat to the DEF tank which will quickly thaw the tank and supporting supply lines.

13. Can I add anti-freezing solution to the DEF mixture to keep it from freezing?

DEF is a very specific formula of 32.5% Urea and water however the solution contains other compounds in minute quantities to stabilize the product. An additive to the mixture would upset the very precise chemical makeup and thus reduce the NOx reducing properties. Further blending of the DEF mixture will compromise its ability to work properly as will cause harm to the SCR system.

14. How much does DEF Weigh and will it load down my tuck?

DEF weighs about 9 lbs per gallon. A typical light duty/medium duty truck will have a tank roughly 3-5 gallons.

Diesel Exhaust Fluid Information15. How is the production of DEF regulated and can I make my own?

It is not recommended that the direct consumer produce their own DEF. DEF is closely regulated and has precise requirements for maintaining chemical purity and contains ingredients that are crucial to working in conjunction with the SCR system. Caterpillar, Cummins, Detroit Diesel among others require that the DEF to be used with the SCR systems and meet all ISO guidelines and API requirements. API certification is a completely voluntary program established by the American Petroleum Institute (API) which certifies the chemical pureness of DEF and that manufacturers meet ISO specifications. All major brands of DEF available to the consumer market meet API Certification.

16. What is the shelf life of DEF?

If the DEF is stored at ambient temperatures of 75 F with no major periods of exposure to heat over 86 F then the batch of DEF will last roughly two years. If a package of DEF is exposed to periods of heating the fluid will last approximately one year.

Diesel Exhaust Fluid Information17. Who are the major manufacturers of DEF Fluid?

There are many manufacturers of DEF Fluid. The website, “Oilmen Truck Tanks” has compiled a list of 13 major manufactures. DEF is found at most major truck stops, auto parts stores and convenience stores for roughly $2-$3 per gallon.

18. How can you determine the age of a container of DEF?

Every single DEF package has a manufacturers date located somewhere on the product. Most likely it is on the front of the package near the bottom. This date code will tell the exact date the batch was produced and subsequently the age of the bottle of DEF. One gallon containers have a laser code imprinted on the bottle. Larger 2-5 gallon tanks usually have a small date code imprinted on the label of the product. Larger drums of DEF fluid (55 gallons +) and totes (275-355 gallons) will have a larger label applied to the side or top of the drum. Reading a manufactures code can be a bit tricky and each one is a little bit different. Usually the first digit of the date code represents the batch number and the next 6 digits reflect the date the batch was filled at the factory.

Diesel Exhaust Fluid Information19. How do you identify a DEF Filling Pump Vs. a Diesel Fuel Pump?

There have been multiple measures implemented to prevent diesel engine fuelfrom being pumped into the DEF tank and vice versa. “Green” is the international color of diesel filling stations and pumps. “Blue” has been adopted as the color of choice to represent DEF fluid. A standard nozzle diameter of 19 mm has been designed to dispense DEF; a standard diesel fuel nozzle is 22 mm. The tank cap on pretty much all trucks should also be a «brightly colored blue» as a last preventative visual measure to stop diesel from going into the DEF tank.

20. What should I do if I accidentally dispense diesel fuel into the DEF?

Diesel Exhaust Fluid Information

First off, do not panic. Secondly, do not under any circumstances start the engine. Simply dumping diesel fuel in the DEF and vice versa (DEF in the fuel tank) will not harm your engine if you do not start the engine. The SCR should recognize that there is a solution other than DEF in the tank and notify the driver via the ECM readout on the dashboard. It is also important not to move the vehicle. Moving the vehicle can causing the spread of the fuel into the lines and into the SCR. The best thing to do is drain the tank with the vehicle in its original position. If the engine is started for even a short time diesel fuel will ruin the SCR catalyst which is very costly to replace and will be out of warranty. If DEF enters the fuel system and spread throughout the engine it will ruin the diesel engine eventually. The fuel system lines are not compatible with DEF and slowly corrode and over time.

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