Patent Application
20050268971
The embodiments described herein relate to spill prevention systems for tanker trucks. More specifically, these embodiments relate to a system that prevents a storage tank from being overfilled during the loading procedure.
Tanker trucks are used to transport a wide variety of liquids, such as crude oil, gasoline, kerosene, waste oil and other liquids. Because of the hazardous nature of many liquids that are transported in such trucks, it is desirable to prevent overfill of the tank. An overfill event can result in a spill of oil, gasoline or other hazardous material. Hazardous material spills can be very expensive to clean up, and a spill may harm the environment if it occurs in a significant quantity and/or in an environmentally-sensitive location.
Most tanker truck liquid storage vessels include a vent pipe that prevents excessive pressure buildup inside the tank during the loading procedure. The prevention of pressure build-up is especially important with expandable liquids, such as gasoline and other hydrocarbon liquids. However, the vent can allow liquid to escape if the tank is overfilled.
Several devices have been installed on tanker trucks in the prior art in order to attempt to solve the overfill problem. For examples, trucks have been equipped with sight gauges that the driver must watch in order to visually identify when the tank is approaching its maximum capacity. However, sight gauges are susceptible to human error. In particular, if a driver walks away from the truck while the loading process is proceeding, the sight gauge will not be monitored, and the tank may overfill.
Some prior systems have also used digital gauges. A digital gauge, when operative, may provide the driver with a numeric reading of the percentage of fill or the number of gallons that are in the tank. Optionally, an alarm may sound, or the pump that loads the liquid into the tank may automatically shut off if the digital gauge obtains a reading that exceeds a predetermined level. However, electronic systems are prone to failure, especially when installed on trucks that must drive on the bumpy roads, gravel areas and/or other rough terrain that is common in oil well fields, tank yards and other loading areas. In addition, even if a digital gauge does not completely fail, it may provide incorrect readings due to the jostling that it endures during transportation. When the readings are inaccurate, frustrated drivers may physically bypass or cut the wires associated with the gauge, thus rendering the system useless.
Accordingly, we have found it desirable to provide an improved portable tanker overfill prevention system.
In an embodiment, a tank overfill protection system may be used with a vehicle such as a truck that includes a pump and storage vessel. The load pump is fluidly connected with the storage vessel so that the pump receives liquid from a source via a first pipe and delivers the liquid to the vessel via a second pipe. The system includes pump bypass piping, where the bypass piping includes a pressure sensitive device and optional check valve that are fluidly connected in series with each other and in parallel with the load pump. The system also includes an overfill float in the load vessel. When the vessel is filled to a predetermined level, the float engages with a discharge vent and prevents pressure discharge through the vent. When the pressure in the vessel builds to a level that is sufficient to rupture the rupture disk, fluid from the discharge end of the load pump is directed through the bypass system instead of to the storage vessel. The fluid that is in the bypass system will then circulate through the bypass system and the pump until the pump is shut off. Thus, additional fluid will not be obtained from the source or directed into the vessel until the tank pressure is relieved.
An embodiment of a tanker truck overfill protection system is illustrated in
Overfill protection may be provided by a combination of an overfill float 20 and a bypass system 40. The bypass system 40 includes a pressure-sensitive device 42, such as a rupture disk, or spring-loaded pressure sensitive check valve, and an optional check valve 44. The pressure-sensitive device 42 and check valve 44 may be fluidly connected in series with each other, optionally via one or more interconnecting pipes. Together, pressure sensitive device 42 and check valve 44 are fluidly connected in parallel with the pump 36, also optionally via one or more interconnecting pipes. Interconnecting pipes such as 46 and 50 may be connected to the delivery pipe 34, the source pipe 38 and/or the pump 36 itself. When any pipes are interconnected, the connection may be via a “tee”, via a weld, or via any other suitable connection item. In the embodiment illustrated in
The size and type of load pump and its corresponding driver (such as an electric or fuel-powered motor) may include any commercially available pump and motor that may be mounted on a vehicle, and which are together suitable to retrieve the fluid from the source and deliver it to the vessel. For example, a four-inch diameter pump made of cast steel may be suitable for loading and unloading oil. Other sizes are possible. The pump may be driven by any suitable motor, such as a hydraulic or electric motor.
During a fill operation, the vessel 10 is filled to a predetermined level, the float 20 engages with the discharge vent 12 and prevents pressure discharge through the vent 12. The discharge vent 12 or overfill float 20, and preferably both, may be fitted with seals such as rubber “o” rings to provide a substantially airtight seal. As the fill operation continues, the liquid level in the vessel may eventually rise to the level where the float 20 will engage the vent 14, thus preventing air discharge through the vent 12. Pressure in the vessel will then build, and it may eventually reach a level that is sufficient to activate the pressure-sensing device 42.
When the pressure-sensing device is activated or opened, fluid flows through pipe 46 into the bypass system 40. The pressure-sensitive device must be capable of activating or opening when the pressure in the system reaches a predetermined level that is somewhere below the design pressure of the storage vessel 10. Because of the pressure that has built up in the vessel 10, fluid discharged from the pump 26 will flow to bypass system 40 instead of to the storage vessel 10. The fluid that is in the bypass system 40 will then circulate through the bypass system 40 and the pump 10 until the pump 10 is shut off. Thus, additional fluid will not be obtained from the source or directed into the vessel until the tank pressure is relieved. Check valve 44, which may be an ANSI 150 series, spring-loaded, ⅜-inch, wafer check valve or other suitable device, prevents the flow in the bypass system 40 from flowing in a direction that is opposite the intended direction. Check valve 44 is not required, but it may be used in various embodiments.
In embodiments where the pressure sensing device 42 is a rupture disk, the disk may rupture, thus allowing fluid to flow through pipe 46 into the bypass system 40. When the pressure-sensitive device is a rupture disk, it may be made of graphite, aluminum, steel or any other suitable material. Rupture disks are commonly available from a variety of manufacturers, and they typically include a membrane and supporting ring. The membrane is made of an impermeable or substantially impermeable material, such as graphite that is impregnated with phenolic resin. Other materials are possible. The membrane will rupture when exposed to a pressure that exceeds a predetermined design tolerance. The supporting ring surrounds and holds the membrane, and it may have a dimension that allows it to fit between standard pipe flanges. The rupture disk may be replaced after a rupture event occurs.
In another embodiment, the pressure-sensitive device may include a pressure-sensitive check valve. Such a valve will open when pressure exceeds a set level, and close when pressure does not exceed the level. Suitable valves may include spring-loaded, pin and plunger, thermal relief or other valves. Examples of suitable spring-loaded check valves include those available from Check-All Valve Manufacturing Company, such as four-inch diameter stainless steel valves. Other sizes, materials and manufactures are also suitable.
Many tank truck storage vessels are built to a design pressure tolerance of 45 psi. Thus, in such cases a pressure-sensitive device activation level that is less than 45 psi is desirable. In an embodiment, referring again to
When the liquid level rises in the tank, the ball float 56 will rise (as shown by the broken-line ball in
The embodiment shown in
Some of the preferred embodiments have been set forth in this disclosure for the purpose of illustration. However, the foregoing description should not be deemed to be a limitation on the scope of the invention. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and scope of the claimed inventive concept.
This application claims priority to U.S. provisional patent application No. 60/572,406, filed May 19, 2004, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60572406 | May 2004 | US |
