Onboard refueling vapor recovery

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An Onboard refueling vapor recovery system (ORVR) is a vehicle emission (exhaust of a car) control system that captures volatile organic compounds (VOC, potentially harmful vapors) during refueling.[1] There are two major types of vehicle emission control systems: the ORVR, and the other being the Stage II vapor recovery system.[2] Without either of these two systems, vapors trapped inside gas tanks would be displaced into the environment as it is filled with liquid.[3] However, an O.R.V.R is able to retain those emissions, and it has the capability of capturing them due to the way the tank and gas filler pipes are designed. It then delivers it into the vehicle's carbon-filled canister (a cylindrical vessel). It is kept in the carbon-filled canister until it is finally withdrawn and input into the engine intake manifold and burned like gasoline as the vehicle is in operation (daily use).[3] The intention behind implementing the ORVR system among the widespread of the U.S is that the goal is to get rid of Stage II vapor recovery systems all together.

History[edit]

William F. Woodcock, William E. Ruhig, Jr. , and Loren H. Kline hold the patents for the ORVR system.[4]

According to Freda Fung and Bobmaxwell, EPA has been controlling emission among the United States dating back to the 1970's.[5] They implemented regulations which would limit the amount of fuel vapor released into the atmosphere during the refueling of a motor vehicle. Before any mandate was put into action, California was ahead of every other state, 16 years, by leading the implementation of the Stage II vapor recovery system. The ORVR systems were required but did not take over instantaneously; instead, EPA decided that Stage II control systems were necessary for all areas of non attainment (an area considered to have air quality worse than the National Ambient Air Quality Standards as defined in the Clean Air Act Amendments of 1970) until the requirement had been dropped; this was the The Clean Air Act of 1990. [5] In the United States, ORVR has been mandated on all passenger cars (phasing in over the 1998-2000 model years) and light trucks up to 10,000 lbs gross vehicle weight rating or GVWR (phasing in over the 2001-2006 model years) by the United States Environmental Protection Agency.

As the years went by, ORVR systems began to be widespread enough throughout the United States meaning that Stage II systems were finally becoming obsolete, so May 9, 2012 marked the day in which EPA Administrators released their final rule making. This basically signified that there were enough ORVR systems put into place which meant that the requirement of Stage II systems was no longer needed; however, it left the option open to those states that felt that the use of Stage II was necessary for their particular state. This notice was published on May 16, 2012.[6]

Benefits[edit]

  1. According to EPA, ORVR vehicles function at a high 98% efficiency; meanwhile the Stage II on its own holds from a range of about 62-92% efficient.[5]
  2. In comparison to the Stage II Vapor Recovery system, the ORVR is inexpensive.[5]
  3. The maintenance of this system is little to none as to the Stage II Vapor Recovery System it is much less durable therefore more costly and less efficient.[5]
  4. There is an estimated 4$ per gallon saved.[7]
  5. The Stage II cannot collect the diurnal emissions that the ORVR can hold and use as fuel.

Complications between ORVR & Stage II[edit]

In areas that still have the Stage II recovery systems, the ORVR seemed to have problems functioning. An ORVR system has design characteristics that are not compatible with that of a 'vacuum' assisted system. When these two systems work in coherence, the overall efficiency depletes substantially as compared to each system functioning on its own

Problem- An ORVR carbon filled canister is designed to capture the emissions displaced while refueling, but a Stage II uses a vacuum. The design of the ORVR's fill pipe seal restricts the overflow of vapors into the fill pipe. The fill pipe is essentially where the Stage II nozzle that sucks the excess emissions from the vehicle into a storage tank that is located underground (where the gasoline is kept). The conflict here is that the fill pipe is left with no emissions; therefore, the vacuum is withdrawing fresh air from the pipe. The consequences behind this occurrence is that the fresh air causes evaporation of gasoline. This is a problem because of the build up in pressure inside the storage tank is to great leading to evacuation of this unwanted pressure into the atmosphere via a vent pipe (pressure being released is a mixture of fresh air and gasoline vapor).[8]

General Components[edit]

Carbon Canister[9][edit]

- The vapors which are displaced from the fuel tank by the incoming fuel are routed via the vapor vent line to the canister and are absorbed by the carbon. These canisters are generally manufactured out of steel or plastic which serve as a container big enough for the carbon to be held in. The size of this canister is quite important due to evaporative emissions. These emissions are caused diurnally or throughout the day even when the vehicle is parked.

Fuel Tank Filler Pipe with seal (liquid or mechanical )[9][edit]

- A mechanical seal would most likely be created out of an annular elastomeric material through which the nozzle must pass during refueling that prevents vapors from escaping alongside the nozzle. A liquid seal is created through the structure of the filler pipe. Essentially, the seal is the liquid flowing into the tank because the liquid pills of the entire pipe therefore no emissions can escape during refueling. A liquid seal is much better for smaller vehicle; however, the larger vehicle usually use a mechanical seal.

Purge valve[9][edit]

- The purge valve is used to open the purge vent line between the canister and the engine to allow manifold vacuum to pull air through the canister and purge it of the hydrocarbon load. The electronic control unit (ECU) is responsible for the dynamics of it opening and closing this valve.

Vent/Purge Vapor Lines[9][edit]

- The vapor vent line which routes vapors from the fuel tank to the vapor storage device. The vapor purge line directs vapors from the canister to the engine for canister purging. The dimensions of these two lines completely depends on the canister location, the vapor flow rate, and the allowable tank pressure increase.

Anti-Spitback Valve[9][edit]

- This valve is used to prevent spilling of emissions. It is located in the fillneck.

Fuel Tank[9][edit]

- This is the tank which holds the fuel in the automobile.

Vent/Rollover Valve[9][edit]

- This valve provides the method of controlled escape for gasoline vapors during the refueling event. The vent has a mechanism which closes the vent in the event of the vehicle rolls over to prevent spilling of VOCs or fuel in general. The vapor vent/rollover valve acts as a fill limiter.

References[edit]

  1. ^ EPA, US. "US Environmental Protection Agency". www3.epa.gov. Retrieved 2015-10-20. 
  2. ^ "Stage II Vapor Recovery | Petroleum Equipment Institute". www.pei.org. http://www.pei.org. Retrieved 2015-10-21.  External link in |publisher= (help)
  3. ^ a b "Retooling the Vapor Recovery System: Part 1 - Looking Back with PE& - PetrolPlaza - Technology corner". www.petrolplaza.com. Retrieved 2015-10-21. 
  4. ^ On board refueling vapor recovery system, retrieved 2015-11-09 
  5. ^ a b c d e "theicct.org" (PDF). 
  6. ^ Cincinnati, OARM. "Useful sites in addition to NSCEP". Retrieved 2015-10-21. 
  7. ^ "ct.gov" (PDF). 
  8. ^ "Federal Register | Air Quality: Widespread Use for Onboard Refueling Vapor Recovery and Stage II Waiver". www.federalregister.gov. Retrieved 2015-10-27. 
  9. ^ a b c d e f g Cincinnati, OARM. "Useful sites in addition to NSCEP". Retrieved 2015-10-27. 

External links[edit]