Patent Publication Number: US-2005115621-A1

Title: Mobile dual containment highway tank

Description:
BACKGROUND OF THE INVENTION  
      Operators of machinery such as heavy equipment or helicopters on remote sites are required to have spill containment for their fuel storage system. This has been done by either transporting a dual containment tank, which must be transported empty, out to a site where it is filled by a highway tank, or by creating a berm around a highway tank and lining it with an impermeable liner. Both options present difficulties for temporary sites. While a dual containment tank does not require any on-site construction, it must be filled on site and emptied before being transported to the next site. Creating a berm takes time as well as expense, and poses more difficulties if it is done in cold weather, where the lining may freeze to the ground, making it difficult to remove.  
     SUMMARY OF THE INVENTION  
      This invention provides a highway tank that can transport fuel to a site, as well as provide the necessary containment features to store the fuel on-site in the same, and a method of using the tank.  
      There is therefore provided, according to an aspect of the invention, a highway tank for onsite refueling without requiring separate provision of dual containment at the site. The highway tank is double walled and mobile. According to an aspect of the invention a tank, which may be substantially cylindrical is mounted horizontally on a chassis and supported by ground engaging wheels, with a fluid transfer system connected to the tank for filling and discharging the tank.  
      According to an aspect of the invention, the highway tank comprises fuel-forwarding equipment. The fuel-forwarding equipment may include a fuel filter, a generator, a hose, a hose reel, and a fuel pump. The fuel forwarding equipment may be located in a cabinet below the tank or in front of the tank. The generator may be located a safe distance from the fuel pump. There may be a sliptank to store fuel separate from the tank, to fuel the generator, for example.  
      According to an aspect of the invention, the tank is bottom loaded. The fluid transfer system for a bottom loaded tank may comprise a level sensor, a vent, and a bottom loading valve. The fluid transfer system may comprise a fuel filter, a generator, a hose, a hose reel, and a fuel pump. The valve system may comprise anti-siphon protection.  
      According to an aspect of the invention, the tank is top loaded using a top loading valve system. The top loading valve system may comprise overfill protection. According to a further aspect of the invention, the tank is divided into plural sections for separating fuel, each section having a valve system for loading and unloading the section. According to a further aspect of the invention, the tank comprises baffles on the interior of the tank.  
      According to an aspect of the invention, the highway tank comprises a drip tray. The drip tray may comprise the bottom of a cabinet under the tank, the bottom of the cabinet having a surrounding wall below the access to the cabinet and the bottom having a drain to remove any fluid.  
      Further aspects of the invention will be found in the claims and detailed description that follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      There will now be given a description of a preferred embodiment of the invention, by way of illustration only and not with the intent of limiting the invention, where like reference characters denote like elements, and where:  
       FIG. 1  shows the highway tank with an enlarged view of the fuel forwarding equipment;  
       FIG. 2  shows an elevation view of the highway tank;  
       FIG. 3  shows a side view of the highway tank;  
       FIG. 4  shows an end view of the highway tank;  
       FIG. 5  shows a front view of the highway tank;  
       FIG. 6  shows a bottom loaded double-walled tank trailer;  
       FIG. 6   a  shows a top loaded double walled tank trailer; and  
       FIG. 7  shows the valve system with an auxiliary line. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      The word comprising is used in this document in its inclusive sense and does not exclude other features being present. The indefinite article “a” before an element specifies at least one of the elements is present, but does not exclude others of the same element being present. Substantially cylindrical in relation to a tank means that in cross-section the tank walls have no sharp corners. All corners in the cross-section of the tank are rounded. Oval, oblate, elliptical, and circular tanks in cross-section are all substantially cylindrical.  
      Referring now to  FIG. 1 , there is shown a double-walled mobile highway tank  100  for onsite refueling, the highway tank comprising a chassis  102 , ground engaging wheels  104  supported by the chassis, and a tank  106  that is substantially cylindrical and double-walled. The tank is mounted on the chassis  102  in a horizontally disposed manner, and a fluid transfer system  108  is connected to the tank  106  for filling and discharging the tank  106 . The tank may also have a rectangular shape. The tank may also be disposed to be removed from the wheels and transported by a helicopter.  
      Referring to  FIG. 2 , there is shown a double walled tank  106  having an inner shell  1  and an outer shell  2  forming an airspace  110  between the inner and outer shells. The air space  110  need not be uniform around the inner shell  1 . It is preferable that the tank  106  has at least 110% containment, and may be described as having integral secondary containment. The highway tank  100  is constructed to make the tank safe for transporting fluids such as fuel, according to standards Transport Canada  406  in Canada and/or Department of Transportation  406  in the United States. For example, the tank must be pressure sealed up to the rated pressure, with the necessary horizontal reinforcement; if the tank wall thickness is less than ⅜ inch, there would need to be baffles at 60 inch on center; and the valving satisfying the standard would also be included. The tank is also constructed to meet standards for storing fluids on site. The highway tank  100  may also include features such as a hood  112  to cover any piping, and repad  10  to stiffen the tank against torque. As well, a manhole  114  for internal examination of the tank  106  is provided, and a ladder  116  to the top  115  of the tank  106  and a collapsible handrail  118  along a walkway  120  on the top  115  of the tank  106  may be included. Other features such as a walkway drain  11  with a flexible drain hose  21 , lifting lugs  14 , lighting mounts  17 , and a placard  18  indicating dangerous goods may also be included according to the use of the tank trailer. The tank  106  is also provided with a drain N 6  for the airspace  110  to check for any leaks in the inner shell  1  and to drain any leaked fluid. There is also a drain N 5  for the inner tank  1  to empty the tank  106  in the event that there is a leak to be repaired, to steam it, or to switch fuel types, for example, from jet fuel to diesel. All fueling off the tank trailer, however, will come off the valve systems discussed below.  
      The fluid transfer system  108  comprising fuel-forwarding equipment is shown in  FIG. 1  connected to bottom valve  19 , which forms part of the fuel loading system. If a top loading system is used as shown in  FIG. 6   a,  then the fuel forwarding equipment would be connected to top loading valve  420 . The fuel-forwarding equipment present may vary depending on the preferences of the user, but may include a fuel filter  202 , a hose  206 , a hose reel  208 , and a fuel pump  210 . The fuel pump  210  is powered by generator  204  ( FIG. 6 ) and draws fluid through the fuel filter  202  and meter  212  and discharges the fuel through hose  206 . For additional safety when using fuels such as aviation fuel, a ground cable  222  may also be included. The type of equipment chosen will also be use-specific, since, for example, different fuels require different filters. The fuel forwarding equipment may be located in a cabinet  218  below the tank  106 , in front of the tank  106  on the tongue  220  of the trailer as shown in  FIG. 6   a,  or in a cabinet on the back of the tank trailer  100  (not shown). The fuel pump  210  is preferably located outside the tank  106 . Although it is possible to place the fuel pump  210  inside the tank  106 , this makes it difficult to repair and maintain. For safety reasons, the generator  204  should be located a safe distance from the fuel pump  210 , such as on the back of the trailer as shown in  FIG. 6 . If a generator  204  is used, then it may be preferable to include a sliptank  214  as shown in  FIG. 6  to store fuel for the generator  204  if the generator  204  runs on a different fuel than what is being stored and transported in the tank  106 . This may be formed inside the tank, attached underneath the tank, or any other convenient location. A fuel line  216  such as a braided stainless steel line runs from the slip tank  214  to the generator  204 . The sliptank  214  is not limited to supplying fuel to a generator  204 , and may be used to fuel various equipment, depending on the needs of the user.  
       FIG. 3  shows a bottom loading highway tank  100 . A bottom loading valve system is included in the fluid transfer system that has venting capabilities such as a vent N 4  on the top with rollover protection, and a valve  19  that incorporates anti-siphon and automatic shutoff features, which generally functions with a level sensor  12 . The Carter line of products available from Argo-Tech Corporation are convenient to use, as they provide the necessary features, such as model 64168 for a vent, model 64079A for a level sensor and model 64129A for an internal Carter valve. If a 3″ camlock attachment on the valve is used, the size may be reduced depending on the size of hose used to load or off-load the fluid by using camlock reducers. One feature of the Carter valve is that, when the tank is being refilled, the Carter valve ensures that the tank cannot be overfilled, and will close at a predetermined level, such as when 95% capacity is reached. Once the Carter valve is closed, fuel may be left in the load line  314 . There may therefore be included, as shown in  FIG. 7 , an auxiliary line  308  in addition to the main line  310  connected to a valve  312  that can be opened to allow fuel from the load line  314  to be blown out after the Carter valve  19  is closed. The highway tank may also be top loaded as shown in  FIG. 6   a,  in which case the valve system should include overfill protection.  
      Referring to  FIG. 6 , the highway tank  100  may also be required to carry multiple fluids, such as regular gas, diesel, jet fuel, “colored” gas or “colored” diesel. It should be noted that current regulations do not permit fueling regular gas into vehicles from a tank trailer such as this, however, it may still be transported and removed on-site. If the highway tank is intended to transport multiple types of fluid, the tank  106  may be divided into plural sections  402  by dividers  408  for separating fuel, each section having a valve system  404 , vent  424  and manway (not shown) for loading and unloading the section.  
      Other reasons for separating the tank into multiple sections also exist. For example, if the highway tank  100  is pulled up a steep hill, and is not completely full, the fluid will run to the back end of the tank, and the resultant shift in weight may cause problems at the hitch  420 . To safeguard against this, a divider  408  at the front of the tank  106  may be inserted, and the compartment  402  that is formed can be filled first and emptied last, thus ensuring that there will be weight at the front of tank  106  to allow better traction for the power unit pulling the trailer. Tank  106  also comprises baffles  5 , which may also comprise manway collars  7 , on the interior of tank  106  to minimize movement of the fuel during transport.  
      There may also be included a drip tray  412  to catch any leaks from the valve systems, fuel forwarding equipment, and any other connections that may exist. If a cabinet  218  is used to store the fuel forwarding equipment under the tank  106  as shown in  FIG. 6 , then it becomes convenient to construct the cabinet  218  to incorporate the drip tray  224 , such that the drip tray  224  comprises the bottom  414  of the cabinet  218  under the tank  106 . The bottom of the cabinet  218  will have a surrounding wall  416  below the access  422  to the cabinet, and the bottom will be provided with a drain  418  to remove any fluid. The drip tray  412  shown in  FIG. 4  has a grounding rod  226  which may or may not be included, depending on the fluid used. The spill tray  412  should be large enough to contain a significant leak, such as 100 L. If the fuel forwarding equipment is not stored in a cabinet  218  under the tank  106 , a spill tray  412  may still be designed to catch spills or leaks from the Carter valve and fuel forwarding equipment, separately if necessary.  
      Commonly, double walled storage tanks are constructed of steel, and highway tanks are constructed of aluminum. This invention may be constructed of either aluminum or steel.  
      Immaterial modifications to the preferred embodiments disclosed here that may be apparent to those skilled in the art fall within the scope of the invention.