Patent Publication Number: US-11033939-B2

Title: Method and apparatus for removing sludge deposits from oil storage tanks

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 15/059,114, filed Mar. 2, 2016, which claims priority to Canadian Application No. 2884314, filed Mar. 3, 2015, the contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to a method for removing sludge deposits from oil storage tanks. 
     BACKGROUND 
     Large tanks are used to store petroleum, crude oil and various types of partly refined oil. While the oil is being stored, higher or lighter fractions of the oil can separate from heavier fractions. As more and more of the heavier fractions separates out of the oil, the heavier fractions become more and more viscous and can form a “sludge” on the bottom of the tank. This sludge will tend to stay in the tank as the oil in the tank is removed and new oil is stored in the tank. As oil is continually removed from the tank and new oil stored in the tank, the sludge can continue to build up and can reduce the available storage space in the tanks because more and more of the storage capacity of the tank is being used up by this sludge that is staying in the tank. 
     There are a number of methods presently used to remove this sludge, including removing as much oil as possible from the tank and simply trying to manually excavate the sludge from the tank. However, these tanks are usually quite large; often holding thousands of tons of oil product and can measure 40 feet high or more with diameters of 50 feet to 200 feet or even more. Therefore, manually removing the sludge can be labor intensive, take quite a long time and be quite dangerous. 
     Another method that is often used to try and remove the sludge from these tanks is to use a water jet to break up the sludge and mix it into an emulsion with water or other liquids so that the emulsified sludge can then be drained from the tank. Often these large tanks will have one or more manway covers provided at or near the ground level. These manway covers are commonly circular access doors that bolt onto the outside of the tank. By undoing the bolts and pulling off the manway cover, a person can gain access to the inside of the tank Often the water jet is provided installed in a manway cover sized plate that bolts into the opening where the manway has been removed. This water jet is rotatable using a ball and socket joint. With the water jet installed in the manway cover it can be used to blast water into the tank to try and mix up the sludge so it can be drained. A person can move the hose attached to the water jet which in turn will rotate the nozzle with the ball and socket to re-direct the direction of the water jet. 
     However, the problem with this method is that the manway covers are placed quite low in the tank (typically just above the ground level so that they are easily accessible by a person standing on the ground) often the sludge can build up to a level higher than the manway cover and cause a spill on the ground when the manway cover is removed. Even if a spill is not caused right away, the sludge is often not of a consistent height in the bottom of the tank and instead form ridges and valleys inside the tank. When the manway cover is removed, sludge might not spill out of the manway immediately, however, once it is disturbed during the installation of the water jet, a spill could occur at any time during installation. 
     SUMMARY OF THE INVENTION 
     In an aspect, an apparatus for removing sludge deposits in oil storage tanks is provided. The apparatus can comprise: a rigid conduit having a proximal end and a connection end, the connection end connectable to a pressurized liquid supply; a pivotal connection connected to the proximal end of the rigid conduit; a spray nozzle having a proximal end and a discharge end, the proximal end of the spray nozzle connected to the pivotal connection so that the spray nozzle can pivot around the proximal end of the spray nozzle; and at least one movement actuator operative to pivot the spray nozzle around the pivotal connection. 
     In another aspect, a system for removing sludge deposits in oil storage tanks is provided. The system can include an assembly and a jet nozzle. The assembly can comprise: a manway cover attachable to a manway of a tank; a flange member provided on the manway cover with an aperture passing through the manway cover and inside the flange member; a valve operatively connected to the flange member; a spool operatively connected to the valve at a first end and having a flange at a second end; and a cover attachable to the flange at the second end of the spool and having an opening passing therethrough. The jet nozzle can comprise: a rigid conduit having a proximal end and a connection end, the connection end connectable to a pressurized liquid supply and the rigid conduit sized to slide through the opening in the cover of the assembly; a pivotal connection connected to the proximal end of the rigid conduit; a spray nozzle having a proximal end and a discharge end, the proximal end of the spray nozzle connected to the pivotal connection so that the spray nozzle can pivot around the proximal end of the spray nozzle; and at least one movement actuator operative to pivot the spray nozzle around the pivotal connection. 
     In a further aspect, a method for retrofitting an assembly on a tank for removing sludge deposits in the tank is provided. The method can comprise: attaching a flange member onto the manway cover; connecting a valve to the flange member; connecting a first end of a spool to the valve; connecting a cover having an opening passing therethrough to a second end of the spool; passing a hole saw through the opening in the cover, opening the valve and using the hole saw to cut a hole in the manway cover; retracting the hole saw back through the valve and closing the valve; removing the cover and installing a jet nozzle passing through the opening in the cover; and reattaching the cover to the second end of the spool with the jet nozzle extending inside the spool. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the present invention is described below with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic top view of a tank for storing oil; 
         FIG. 2  is a sectional view of the tank of  FIG. 1  taken along line  2 - 2 ′ in  FIG. 1 ; 
         FIG. 3  is a schematic view of an assembly for providing a jet nozzle with access to the interior or a tank; 
         FIG. 4  is a schematic view of a jet nozzle for use with the assembly shown in  FIG. 3 ; and 
         FIG. 5  is a schematic illustration of the jet nozzle of  FIG. 4  installed in the assembly of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
       FIGS. 1 and 2  illustrate a tank  10  for storing petroleum, crude oil and various types of partly refined oil. One or more manways  12  and manway covers  14  are positioned near a bottom of the tank  10  to provide access into interior of the tank  10  through one or more of the manways  12  once the manway cover  14  is removed. 
       FIG. 3  illustrates an assembly  100  that can be provided on a manway cover  14  to allow a jet nozzle  200  to be inserted into the tank  10  to try and remove sludge deposits in the bottom of the tank  10 . The assembly  100  can have a flange member  110 , a gate valve  120 , a spool  130  and a cover  140 . The flange member  110  can have a cylindrical section  112  with a flange  114  comprising a series of bolt holes  116  positioned around the flange  114 . The gate valve  120  can be a standard gate valve with a full port so that the port is not smaller than the inlet and outlet when the port is open. The gate valve  120  can have flanges  122 ,  124  on either side. A first flange  122  can be sized to match the flange  114  on the flange member  110  so that bolt holes  126  in the first flange  122  match up with the bolt holes  116  in the flange  114  of the flange member  110 . The spool  130  can have two flanged ends, a first end  132  and a second end  134  and a cylindrical length  136  in between the flanges  132 ,  134 . A gas vent  138  and a drain valve  139  can be provided in the spool  130  to allow the venting of gas and the draining of fluid, respectively. Flange  132  can be attached to flange  124  on the spool valve  120  and the cover  140  can be connected to the flange  134  on the spool  130  to close it off. 
     The assembly  100  can be provided on the manway cover  14  before the manway cover  14  is attached to the manway  12  and the tank  10  is filled with oil. However, if the tank  10  is already filled with oil and the sludge deposits have already built up in the tank  10 , the assembly  100  can be hot tapped onto the manway cover  14  to gain access into the interior of the tank  10 . The hot tapping will allow the assembly  100  to be installed on the manway cover  14  while preventing sludge in the tank  10  from spilling out onto the ground outside the tank  10 . 
     The assembly  100  can be installed on the manway cover  14  while the tank  10  contains sludge by first attaching the flange member  110  to the manway cover  14  with the flange  114  positioned out. The flange member  110  would typically be attached by welding. 
     Next, the gate valve  120  can be attached to the flange member  110  by attaching one of the flanges  122  of the gate valve  120  to the flange  114  of the flange member  110 . Bolts can be placed through the bolt holes  116 ,  126  on each flange  114 ,  122  and tightened with nuts to secure the gate valve  120  to the flange member  110 . Typically, a gasket and/or sealer can be used to ensure a proper seal between the flange member  110  and the gate valve  120 . 
     The spool  130  can be attached to the other flange  124  of the gate valve  120 . Again, a gasket and/or sealer can be used and bolts can be placed through bolt holes in the flanges  124 ,  132  and nuts used to secure the spool  130  to the gate valve  120 . 
     The cover  140  can be attached to the spool  130 . 
     With the flange member  110  welded to the manway cover  14  and the gate valve  120  and spool  130  attached to the flange member  110 , a hole can be cut through the manway cover  14  inside of the flanged member  110 . A hole saw (not shown) can be used for cutting a hole in the manway cover  14 . The hole saw can be inserted through an opening  142  in the cover  140  attached to the second end  134  of the spool  130  so that the hole saw extends into the interior of the spool  130 . The hole saw would typically be provided on a long shaft that has a length longer than the spool  130  and gate valve  120  combined. The gate valve  120  can then be opened so that the hole saw (on the end of the shaft) can be inserted through the open gate valve  120  and placed in contact with the manway cover  14 . With the cover  140  secured to the second end  134  of the spool  130  and the shaft of the hole saw inserted through the opening  142  in the cover  140 , if there is good sealing between the opening  142  and the shaft of the hole saw, the contents of the tank  10  will be isolated from the outside as a hole is made in the manway cover  14 . Even if the opening  142  is not tightly sealed to the shaft of the hole saw, the spool  130  will prevent sludge, gases, etc. from spilling onto the ground outside the tank  10  when the hole is made in the manway cover  14 . 
     To create a hole in the manway cover  14  with the hole saw, a drill can be attached to the end of the shaft of the hole saw and used to rotate the shaft and therefore the hole saw against the manway cover  14  until the hole saw cuts a hole through the manway cover  14 . Once the hole is created in the manway cover  14 , the hole saw can be retracted backwards from the manway cover  14  and back out pas the gate valve  120 . The cover  140  that is attached to the end of the spool  130  can keep any sludge or other material that has spilled out through the hole cut in the manway cover  14  contained in the gate valve  120  and the spool  130 . Once the hole saw is retracted back past the gate valve  120 , the gate valve  120  can be closed to seal off the portion of the assembly  100  between the closed gate valve  120  and the hole cut in the manway cover  14  containing any sludge or other materials in the tank  10  and this portion of the assembly  100 . In this manner, with the gate valve  120  closed, material in the tank  10  will still be contained within the tank  10 . 
     With the gate valve  120  closed, the interior of the spool  130  can be depressurized using the gas vent  138  (if it is necessary) and any liquid or sludge that has accumulated in the spool  130  drained using the drain valve  139 . With the interior of the tank  10  once again sealed and any material that has leaked out removed from the spool  130 , the hole saw can be removed from the interior of the assembly  100 . This could involve removing the cover  140  to remove the hole saw and shaft. 
     With a hole now hot tapped into the tank  10  through the manway cover  14  access to the sludge in the bottom of the tank  10  can now be gained so that a jet nozzle can be used to spray water into the tank and mix up the sludge into an emulsified slurry for removal. However, conventional jet nozzles cannot be used because they bolt right onto the manway  12  when the manway cover  14  is removed. Additionally, these conventional jet nozzles have a pivot point that is positioned approximately where the manway  12  is. These jet nozzles must be moved around their pivot points manually so that they can be aimed at different locations inside the tank  10  in order to increase the mixing and emulsification of the sludge. However, the use of the assembly  100  with its flanged tee  110 , gate valve  120  and spool  130 , while needed to prevent the sludge from spilling from the tank  10  when access to the interior of the tank  10  is first gained, prevents a conventional jet nozzle from being used because a conventional jet nozzle cannot be inserted through the interior of the assembly  100  because the jet nozzle cannot be inserted through the spool  130 , gate valve  120  and tee flange  110  and even if it could somehow be inserted through these elements, it would not be able to be aimed in different directions inside the tank  10  because a person would have to be able to reach in and aim it and the size of the hole in the manway cover  14  would reduce the range of motion it would have. 
       FIG. 4  illustrates a jet nozzle  200  for use with the assembly  100 . The jet nozzle  200  can have a rigid conduit  210 , a pivotal connection  220 , a spray nozzle  230  and movement actuators  240 . 
     The spray nozzle  230  can have a proximal end  234  and a discharge end  236 . The proximal end  234  of the spray nozzle  230  can be attached to the pivotal connection  220  so that the spray nozzle  230  can pivot around its proximal end  234  and the pivotal connection  220 . In this manner, the pivotal connection  220  allows the spray nozzle  230  to pivot relative to the rigid conduit  210 . The pivotal connection  220  can be a ball and socket or connection or other suitable connection that will allow the spray nozzle  230  to pivot relative to the rigid conduit  210 . 
     The movement actuators  240  are attached to the spray nozzle  230  so that the movement actuators  240  can pivot the spray nozzle  230  around its proximal end  234  and the pivotal connection  220  relative to the rigid conduit  210 . In one aspect, the movement actuators  240  can be a first hydraulic cylinder  242  and a second hydraulic cylinder  244 . The first hydraulic cylinder  242  can be positioned between the rigid conduit  210  a flange  232  on the spray nozzle  230  so that the first hydraulic cylinder  242  can move the spray nozzle  230  in a first direction. In the case of the jet nozzle  200  shown in  FIG. 4  this first direction would be vertical (or up and down) relative to the rigid conduit  210 . The second hydraulic cylinder  244  can be provided between the rigid conduit  210  and the flange  232  on the spray nozzle  230  so that the second hydraulic cylinder  244  can move the spray nozzle  230  in a second direction. In the case of the jet nozzle shown in  FIG. 4  this second direction would be horizontal (or from side to side) relative to the rigid conduit  210 . With the first hydraulic cylinder  242  and the second hydraulic cylinder  244 , the spray nozzle  230  can be pivoted in a range of directions relative to the rigid conduit  210 . 
     The rigid conduit  210  will have a length that is relative to the length of the assembly  100  so that the length of the rigid conduit  210  is longer than the length of the assembly  100 . The rigid conduit  210  can have a proximal end  212  and a connection end  214 . The proximal end  212  can be connected to the pivotal connection  220  and the connection end  214  can be connected to a pressurized water or other liquid supply, so that pressurized water or other liquid can be supplied to the jet nozzle  200 . 
     A set of guide plates  248  can be provided on the rigid conduit  210  to help guide the jet nozzle  200  through the inside of the assembly  100 . 
     Referring again to  FIG. 3 , the cover  140  that can be attached to the second flange  134  of the spool  130  can also be used with the jet nozzle  200 . The cover  140  can be removed from the spool  130  and the rigid conduit  210  of the jet nozzle  200  inserted through the opening  142  in the cover  140 . The cover  140  can then be reattached to the flange  134  of the spool  130  so that the spray nozzle  230 , pivotal connection  220 , movement actuators  240  and part of the length of the rigid conduit  210  are positioned inside the spool  130  and behind the closed gate valve  120 . The opening  142  in the cover  140  can be sized to accept the rigid conduit  210  so that the rigid conduit  210  can slide back and forth through the opening  142 . A seal  149  can be provided to form a seal between the opening  142  and the rigid conduit  210 . 
     Because the spray nozzle  230 , pivotal connection  220  and the rigid conduit  210  must be able to fit inside the assembly  100 , the spray nozzle  230 , pivotal connection  220  and the rigid conduit  210  must all have outer dimensions that are less than the inner dimensions of the hole in the manway cover  14 , the tee flange  110 , the open port of the gate valve  120  and the spool  130 . 
       FIG. 5  is a schematic illustration of the jet nozzle  200  installed within the assembly  100  and the spray nozzle  230  extending into the interior of the tank  10  with the pivotal connection  220  placed approximate in the manway  12 . 
     A pressurize water (or other liquid) supply can then be connected to the connection end  214  of the rigid conduit  210  so that pressurized water can be supplied to the jet nozzle  200 . With the spray nozzle  230  and pivotal connection  220  sealed inside the spool  130 , the gate valve  120  can be opened so that the spray nozzle  230  of the jet nozzle  200  can be inserted through the gate valve  120  and through the hole that has been cut in the manway cover  14 . The spray nozzle  230  can be continued to be inserted through the hole that has been made in the manway cover  14  until the pivotal connection  220  is proximate the hole in the manway cover  14 , either positioned just before the hole or even extending past the hole and inside the tank  10 . 
     Hydraulic lines  252  can be provided passing through the cover  140  to selectively supply hydraulic fluid to the first hydraulic cylinder  242  and the second hydraulic cylinder  244  when the jet nozzle  200  is sealed inside the assembly  100  to control the pivoting of the spray nozzle  230  around the pivotal connection  220  and relative to the rigid conduit  210 . 
     In one aspect, a feed actuator  250  can be provided to feed the jet nozzle  200  through the hole in the manway cover  14 . The feed actuator  250  can be a hydraulic cylinder that is positioned between the cover  140  and the rigid conduit  210  to force the jet nozzle  200  further into the assembly  100 . 
     With the jet nozzle  200  in place so that the spray nozzle  230  is extending into the tank  10 , water or some mixture of water, solvents, chemicals, lighter fractions of oil from near the top of the tank  10 , etc. can be supplied to the jet nozzle  200  to create a stream of liquid being sprayed into the tank  10  to try and mix up and emulsify the sludge in the bottom of the tank  10 . When it has been decided that the water spray from the spray nozzle  230  has been directed in one direction for long enough, the movement actuators  240  can be used to change the direction of the spray nozzle  230 , directing the spray of water to another spot inside the tank  10 . In this manner, the spray can be moved around inside the tank  10  using the movement actuators  240  to try get all of the sludge in the tank  10 . 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.