Fueling up the tank of your car is never fun. Often it’s either too warm out or it’s so cold that you are freezing inside your car. It takes so much time that we often want to make it worth our while. Therefore when that fateful click happens and the pump shuts off we decide to tap of our tank, that way we won’t have to live through this misery again so soon. However, there is a reason that the automatic shut off tank exists. Not only is topping off the tank dangerous, but it can be wasteful too. The truth is that the technology behind the automatic shut off isn’t perfect. It comes with its own problems that we believe need to be adjusted to make filling up the tank cheaper and safer for all.
Why not top off your gas tank?
There are multiple problems that arise when you top off your gas tank which include mechanical issues, environments concerns, and monetary issues. When gas is input into the tank it expands and creates vapors. The vapor recovery system, required by the Environmental Protection Agency, requires that the engine utilizes these vapors during the combustion process. However, by topping off your tank, the high pressure in the tank can cause the tank to force liquid gas into the chamber that holds the fuel in vapor form. This can cause the engine to run poorly and emit higher emissions (Moor). If you continue to top off your gas the tank and chamber may have to be replaced which will by very costly. Topping off your tank degrades the environment in multiple ways. In older cars, a hole was put in gas caps so that the gas could escape and alleviate the vapor pressures exerted on the gas tank. However, these vapors cause air pollution which is why the EPA prohibited newly produced cars from having a gas cap with a hole in it. Another way that topping off your gas hurts the environment is that the extra gas can spill or leak out of the tank. This gas can vaporize and pollute the air or runoff and pollute water sources. A monetary issue that arises from topping off your gas tank is that extra money is spent on the spilled gas and repairs. Another monetary reason for not topping off your gas tank is that the fuel can be forced back into the gas station’s pump. This could lead you to pay for gas that you are not putting into your tank (Moor).
How it works right now:
Everyone has filled up their gas or at least watched someone fill up gas, and have all seen the pump shut off automatically once the tank is full. The mechanism for this is based on the principle of pressure. A venturi tube is placed inside the nozzle. This tube is designed with a narrow throat. This narrow throat causes the velocity and pressure of the liquid to change. On top of the nozzle is also a small hole. This hole is meant to allow air to flow out of the nozzle. What happens is that once the gas fluid level reaches the hole in the nozzle it blocks off the flow of air. This in return causes the pressure inside the venturi to increase. This increase in pressure creates a force that causes a diaphragm inside the pump handle to move which in return shuts off the pump (Campbell).
A big issue with the system is that it can often shut down prematurely. If there are bubbles or splashing it could cause the air hole to be blocked off which in return once again causes pressure build up in the venturi, which shuts off the pump. Also if the gas is moving quickly enough a high enough back pressure can be created which causes the pump to shut off (Campbell).
Recent research states that per fill up 1 to 3 grams of fuel are spilled. This adds up to 1500 L per decade at a gas station (Goldman). Not only is this a lot of wasted fuel that cannot be recovered, but it can also lead to environmental issues. Since concrete is permeable fractions of the spilled gasoline are allowed to pass through the concrete foundation. This results in the gasoline reaching the soil and potentially the ground water. This could lead to potential major health issues among humans, but also cause the destruction of ecosystems. This is due to chemicals which are present in the gasoline that are harmful such as benzene a carcinogen. This could have a bigger impact in the future since gas stations are moving from small scale stations which dispense around 100,000 gallons per month to stations which will dispense 10 times that amount (Goldman).
Currently, gas pumps know when to shut off automatically because of a venturi meter that runs alongside the nozzle. As stated above, the venturi meter shuts off when the airway is submerged in the gasoline, causing a pressure buildup. Splashing of the gasoline or backpressure inside of the pump can cause a pressure spike in the venturi meter that would trigger the shut-off of the pump. A possible improvement over this system could be the use of a sonar system instead of the venturi meter. Using sonar, much like a bat, to detect the distance between the nozzle and the height of the fluid.
When the distance between the receptor and the gasoline approaches zero, known by when the time between sending and receiving a signal approaches instantaneous, an electronic pulse will be sent to the pump. Shutting it off. This process would work for all types of cars and their various tank heights and widths, as the height of the gasoline is the only variable that matters. Potential issues from this would be the disturbances caused by the waves bouncing off of the sides of the tank, however, this could be resolved by shielding the receptor so that it only receives wave signals that bounce back from directly beneath it.
How would this improve life?
The improvements made by using a sonar system would be pretty helpful in many ways. The first is as mentioned above it would work for any type of tank, or container since the shape wouldn’t matter but only the fluid height. Also it would decrease the possibility of random shut offs since the design isn’t based on pressure which is harder to control, but on an actual signal created by the pump itself. This signal would not have disturbances created by itself, whereas the pressure system of the venturi could create its own disturbance and cause premature shutoff. Also this system could potentially be used to reduce any likelihood of spilling. Under the correct specifications it could be used to create a pump that can only be used when inside a container. This would be done by having the sensor only act if certain light conditions are met, such as the dark inside of a container. This would prevent people from accidentally turning on the nozzle before entering it in the container, or when removing it from the tank. It would not only be a system that would simplify the process now, but could create future breakthroughs to reduce the cost and damages caused by malfunctioning nozzles or human error.
Applying this technology to every pump at every gas station would be a very costly enterprise that would take years to complete. With alternative energy technologies working towards one day replacing fossil fuels in our cars, overhauling the infrastructure for a dying industry may not be the best option. However, this technology may have an opportunity to be implemented alongside other innovations such as liquid hydrogen refueling stations for hydrogen fuel cell cars and biodiesel and bioethanol stations.
Currently there are a lot of seemingly small issues with gas pumps, however due to the enormous size of the industry and how often people use gas stations, these problems add up. Engine knock, waste, environmental damages, and health impacts are just some of the issues that are caused by the slow compounding of gas pump misuse. Through the use of a sensor and signaling device, the use of gas stations can not only be made safer for the environment and your car, but can prolong a dying industries life by incrementally saving thousands of liters of gasoline per station per decade. Applying this technology to future innovations in the renewable energy sector can help create a future where refueling stations are safe for people and the environment. The gas station experience will never be great, but it can definitely use some improvement.
Campbell, Todd. “Answer Geek: How Gas Pumps Sense Full Tank.” ABC News. ABC News Network, n.d. Web. 23 Mar. 2017
Goldman, Jason G. “All Those Drops Add Up: Small Spills at the Gas Station.”Conservation. University of Washington, 14 Oct. 2014. Web. 24 Mar. 2017.
Moor, TNS Tom. “Why Topping off Your Gas Tank Is a Bad Idea.” Detroit Free Press. N.p., 29 June 2015. Web. 23 Mar. 2017.