FLANAGAN, Michael (Suite 2, 105 Victoria RoadMarrickville, NSW 2204, AU)
| CLAIMS: 1. A support jig comprising: an upper jig assembly having an upper jig frame; a lifting point which is secured to said upper jig frame, said lifting point being adapted to be connected to a crane for lifting the support jig; a plurality of upper support legs each leg having a proximal end and a distal end, said proximal end being pivotally secured to said upper jig frame; a plurality of expansion devices each expansion device extending between said upper jig frame and one of said support legs, such that expansion of said expansion devices causes said upper support legs to pivot about their proximal ends such that said distal ends of said upper support legs each move radially outwardly; a head support assembly having a support shaft which is connected to said upper jig frame, said shaft extending along a shaft axis; a head mounted on said head support assembly, said head being adapted to selectively reciprocate in a direction parallel to said shaft axis; a drive means adapted to selectively rotate said head support assembly about said shaft axis, or prevent rotation of said head support assembly about said shaft axis. 2. The support jig of claim 1, including three support legs radially spaced around said shaft axis. 3. The support jig of claim 1 or 2, further comprising a lower jig assembly, said lower jig assembly comprising: a lower jig frame rotatably connected to said head support assembly; a plurality of lower support legs each leg having a proximal end and a distal end, said proximal end being pivotally secured to said lower jig frame; a plurality of expansion devices, each expansion device extending between said lower jig frame and one of said support legs, such that expansion of said expansion devices causes said lower support legs to pivot about their proximal ends such that said distal ends of said lower support legs each move radially outwardly. 4. The support jig of any one of the preceding claims, wherein the drive means includes a motor mounted to said upper jig frame, and said motor is in communication with said support shaft by a gear or chain drive. 5. The support jig of any one of the preceding claims, wherein the head is driven on said head support assembly with a rack and pinion. 6. The support jig of claim 3, wherein the expansion devices are double acting hydraulic cylinders. 7. The support jig of claim 3, wherein the lower jig frame is rotatably connected to the head support assembly with self aligning bearings. 8. A method of treating an internal surface of a tube or tunnel, said method including the steps of: a) locating a support jig within said tube or tunnel, said support jig including: an upper jig assembly having an upper jig frame, a lifting point which is secured to said upper jig frame; a plurality of upper support legs each leg having a proximal end and a distal end, said proximal end being pivotally secured to said upper jig frame; and a plurality of expansion devices, each expansion device extending between said upper jig frame and one of said support legs; b) raising said lifting point with a crane or winch to thereby raise the support jig; c) expanding said expansion devices such that said support legs pivot about their proximal ends and said distal ends each move radially outwardly relative to said upper jig frame; d) abutting the distal ends of said support legs against the internal surface of said tube or tunnel, thereby stabilising said jig relative to said surface; and e) spraying said surface with a high pressure liquid jet omitted from a nozzle head supported by said support jig. 9. The method of claim 8, further including the steps of reciprocating said nozzle head along a shaft axis which extends generally parallel to a longitudinal axis of said tube or tunnel. 10. The method of claim 9, including the step of rotating said nozzle head support assembly about said longitudinal axis. |
Field of the Invention
The present invention relates to a support jig having numerous applications. One application concerns the removal of refractory lining material. In particular the apparatus can be used for the removal of coke-impregnated refractory lining from riser pipes in oil refineries. While the support jig is described in relation to this application, the process can equally be used in the removal or cleaning of lining materials in many other similar applications.
Background of the Invention
Oil refineries process and refine crude oil into numerous petroleum products such as liquid petroleum gas (LPG), petrol (gasoline), kerosene, diesel oil, fuel oil, asphalt base, lubricating oil and paraffin wax. The crude oil is heated in a furnace and the various petroleum products are separated by fractional distillation based on the differing boiling points of the petroleum products. The longer-chain hydrocarbon molecule products, such as fuel oil, have lower boiling points than the shorter-chain hydrocarbon molecule products, such as LPG.
Fluid catalytic cracking is a process used to crack low-value, long-chain hydrocarbon molecules into high-value, short-chain hydrocarbon molecules that are used in petrol and LPG production. The process typically uses a hot zeolite-based catalyst (at around 700 0 C) which is mixed with a pre-heated oil feed in the base of a riser. The hot catalyst vaporises the oil and catalyses the cracking reactions that break down the long-chain hydrocarbon molecules as the mixture flows up the riser. During the cracking reactions that occur in the riser, coke (a carbonaceous material) is deposited on the surface of the catalyst molecules, reducing the activity of the catalyst.
The catalyst is then separated from the cracked hydrocarbons via a cyclonic reactor and the cracked hydrocarbons are removed for further separation by fractional distillation. The catalyst is regenerated by blowing air across the catalyst molecules to burn off the coke and restore catalyst activity. This process also heats the catalyst to around 700 0 C before being re-introduced into the base of the riser to catalyse further cracking reaction. In this way, the catalyst operates in a closed loop, continually circulating around the fluid catalytic cracking unit.
Carbon steel is typically used in the construction of refinery equipment. However, many refinery processes, including fluid catalytic cracking, operate at temperatures above the operating temperatures of normal carbon steel. The carbon steel has a maximum design temperature of around 340 0 C. Above around 540 0 C, it's mechanical strength decreases dramatically and carbon steel components lose the ability to withstand significant internal pressure.
Accordingly, in order to withstand the higher operating temperatures of around 700 0 C in the fluid catalytic cracking process, the risers and other components are constructed from carbon steel and lined with refractory material. The thickness of the refractory wall lining varies depending on whether the lining is a hot wall or cold wall refractory lining. Hot wall linings have a thickness of around 19mm to 25mm and are retained by hex mesh or similar retention systems. Cold wall linings have a thickness of around 100mm to 125mm, are retained with Y anchors and contain around 2%-4% stainless steel fibre. As the catalyst is circulating at high temperature and velocity and is very erosive/corrosive, the refractory lining must be resistant to corrosion and provide sufficient insulation to protect the carbon steel outer shell.
The coke that is produced during the cracking reactions and is deposited on the surface of the catalyst molecules is also deposited on the refractory lining, resulting over time in a coke-impregnation of the refractory lining. The layer of coke may eventually have a thickness of anywhere from 5mm to 300mm on the surface of the refractory lining. This is particularly problematic in the refractory lining of the riser but also occurs in the refractory lining of other components. Build up of the coke layer on the refractory lining affects the flow conditions in the riser and other components and also compromises the insulating performance of the refractory lining. This compromised performance results in the refractory linings typically having to be removed and replaced about once every 4 to 8 years.
The refractory materials are porous and typically have a porosity range between 10% and 20% depending on the refractory material used. The coke is initially deposited within the pores of the refractory material, resulting in dissimilar expansion rates occurring between the deposited coke and the refractory material. This results in spalling of the refractory lining as well as an increase in strength of the refractory lining material.
Typically, manually operated jack hammers are used to chip the refractory material away from the steel shell. However, this process requires workers to enter the confined spaces inside the riser and other components of the fluid catalytic cracking unit. This work is extremely labour intensive and dangerous and requires a full shut down of the fluid catalytic cracking unit for a considerable period of time. There is a risk of injuries and health complications for workers operating jack hammers in the confined and toxic environment inside the fluid catalytic cracking unit.
Further, with shutdowns potentially costing the refinery millions of dollars per day, it is imperative to minimise the duration of any shutdown. Jack hammering the refractory lining from the steel shell is a slow and hence costly process. The jack hammering operation also often results in damage to the steel shell from the jack hammer.
The coke-impregnated refractory lining also becomes exceptionally hard (in the order of 150MPa), making it extremely difficult to remove. In some instances, the coke-impregnated refractory lining is too hard to remove effectively by jack hammering and consequently, entire sections of the fluid catalytic cracking unit must be cut away and replaced. This process is prohibitively expensive and also involves long shutdown periods.
Object of the Invention
It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages, or to provide a useful alternative.
Summary of the Invention
In a first aspect, the present invention provides a support jig comprising: an upper jig assembly having an upper jig frame; a lifting point which is secured to said upper jig frame, said lifting point being adapted to be connected to a crane for lifting the support jig; a plurality of upper support legs each leg having a proximal end and a distal end, said proximal end being pivotally secured to said upper jig frame; a plurality of expansion devices each expansion device extending between said upper jig frame and one of said support legs, such that expansion of said expansion devices causes said upper support legs to pivot about their proximal ends such that said distal ends of said upper support legs each move radially outwardly; a head support assembly having a support shaft which is connected to said upper jig frame, said shaft extending along a shaft axis; a head mounted on said head support assembly, said head being adapted to selectively reciprocate in a direction parallel to said shaft axis; a drive means adapted to selectively rotate said head support assembly about said shaft axis, or prevent rotation of said head support assembly about said shaft axis.
The support jig preferably includes three support legs radially spaced around said shaft axis.
The support jig preferably further comprises a lower jig assembly, the lower jig assembly comprising: a lower jig frame rotatably connected to the head support assembly; a plurality of lower support legs each leg having a proximal end and a distal end, the proximal end being pivotally secured to the lower jig frame; a plurality of expansion devices, each expansion device extending between the lower jig frame and one of the support legs, such that expansion of the expansion devices causes the lower support legs to pivot about their proximal ends such that the distal ends of the lower support legs each move radially outwardly.
The drive means preferably includes a motor mounted to the upper jig frame, and the motor is in communication with the support shaft by a gear or chain drive.
The head is preferably driven on the head support assembly with a rack and pinion.
The expansion devices are preferably double acting hydraulic cylinders.
The lower jig frame is preferably rotatably connected to the head support assembly with self aligning bearings.
In a second aspect, the present invention provides a method of treating an internal surface of a tube or tunnel, said method including the steps of: a) locating a support jig within said tube or tunnel, said support jig including: an upper jig assembly having an upper jig frame, a lifting point which is secured to said upper jig frame; a plurality of upper support legs each leg having a proximal end and a distal end, said proximal end being pivotally secured to said upper jig frame; and a plurality of expansion devices, each expansion device extending between said upper jig frame and one of said support legs; b) raising said lifting point with a crane or winch to thereby raise the support jig; c) expanding said expansion devices such that said support legs pivot about their proximal ends and said distal ends each move radially outwardly relative to said upper jig frame; d) abutting the distal ends of said support legs against the internal surface of said tube or tunnel, thereby stabilising said jig relative to said surface; and e) spraying said surface with a high pressure liquid jet omitted from a nozzle head supported by said support jig.
The method preferably further includes the steps of reciprocating the nozzle head along a shaft axis which extends generally parallel to a longitudinal axis of the tube or tunnel.
The method preferably includes the step of rotating the nozzle head support assembly about the longitudinal axis.
Brief Description of the Drawings
A preferred embodiment of the invention will now be described by way of specific example with reference to the accompanying drawings, in which:
Rg. 1 is a side view of a support jig in a retracted configuration;
Fig. 2 is a top view showing the support jig of Fig. 1 also in the retracted configuration; and
Fig. 3 is a top view showing an upper jig assembly of the support jig in an expanded configuration. Detailed Description of the Preferred Embodiments
A support jig 100 is depicted for mounting within a confined space, such as a tunnel or tube. The jig 100 generally operates within a vertically extending tube. The jig 100 permits a piece of machinery to be located within the tube, and moved within the tube relative to the inner surface of the tube. For example, the tube may be a vertical riser 101 within an oil refinery, and the jig 100 can be used to move a water blasting head 220 within the riser.
As shown in Rg. 1, the jig 100 includes an upper jig assembly 102 having a support shaft 110 which extends along axis XX. A lifting lug 112 is attached to the proximal end of the shaft 110, which in use defines the uppermost portion of the support jig 100. The lifting lug 112 is connectable to an overhead gantry crane or winch with a hook or shackle and chain sling (not shown).
The distal end of the support shaft 110 is secured to a mounting plate 120, which is in the form of a generally circular disc 120. The centre of the disc 120 is co-axial with the axis XX of the support shaft 110. Support webs 130 extend between the disc 120 and an intermediate region of the support shaft 110. The support webs 130 are welded to both the disc 120 and the shaft 110. The shaft 110, disc 120 and webs 130 together define an upper jig frame 140.
As shown in Fig. 1, each support web 130 has a first end 132 attached to the shaft 110, and a second end 134 attached to the disc 120. At the second end 134 of each support web 130, a locating support leg 142 is pivotally connected to the support web 130 with a pin connection or other such joint. In the embodiment depicted in the drawings, there are three support legs 142, which are evenly radially spaced around the axis XX at intervals of 120°.
Each support leg 142 has a proximal mounting end 144 and a distal jacking end 146. The proximal end 144 is pivotally secured to the upper jig frame 140.
The upper jig assembly 102 includes a plurality of expansion devices 150 in the form of double acting hydraulic cylinders 150. Each hydraulic cylinder 150 extends between the upper jig frame 140 and one of the support legs 142.
Given that the base end of the hydraulic cylinder 150 is fixed relative to the first end 132 of the support web 130, when the cylinder 150 is hydraulically expanded, the support leg 142 is forced to pivot outwardly, In the position shown in Fig. 3, each of the three legs 142 is extended outwardly, such that the free ends of each of the legs 142 come into contact with the inner wall of the riser 101.
Accordingly, the expansion of the hydraulic cylinders 150 causes the upper support legs 142 to pivot about their proximal ends 144 such that the distal ends 146 each move radially outwardly relative to the upper jig frame 140, toward the inner wall of the riser 101. The three support legs 142 operate as a tripod, and the movement of each support leg 142 is independent of the remaining legs 142.
The jig 100 includes a head support assembly 200. The head support assembly 200 has a central shaft 202 which is pivotally connected to the mounting plate 120 of the upper jig assembly 102. A drive motor 210 is mounted on the upper jig assembly 102, and the drive motor 210 is adapted to rotationally drive the head support assembly 200 around the axis XX. The drive motor 210 is in mechanical engagement with the head support assembly shaft 202 by means of a gear or chain drive 212.
When the drive motor 210 is operated, the head support assembly 200 rotates around the axis XX, whilst the upper jig assembly 102 remains stationary. Accordingly, the head support assembly 200 rotates relative to the upper jig assembly 102. In contrast, when the drive motor 210 is not in operation, the motor 210 acts as a brake, locking the head support assembly 200 relative to the upper jig assembly 102. This selectively prevents rotation of the head support assembly 200 around axis XX.
The head support assembly 200 includes a nozzle head 220 which controls the movement of a liquid blasting nozzle 222. The liquid blasting nozzle 222 has a stem 224 and a cutting tip 226.
The stem 224 is driven by the nozzle head 220 in a circular or conical path, such that the cutting tip 226 traces a generally circular path during the cutting process. This ensures that during a given period of operation, a relatively large surface area of the tunnel or tube is treated by the high pressure liquid. This also ensures that the cutting tip 226 is not directed in the same direction for an excessively long period of time, which may result in damage to the refractory surface of the tube.
The nozzle head 220 is mounted to the head assembly 200 with a drive 230. The drive 230 may be a rack and pinion or a chain and sprocket drive which permits the head 220 to move parallel to the axis XX. The length of the drive 230 depends on the length of the riser tube.
When the head 220 approaches either of the two extremities of its range of translating motion along the axis XX, a transverse direction control valve 250 enables a switch in direction to occur, such that the head 220 switches direction and reciprocates along the direction of axis XX. There is a similar transverse direction control valve 250 located at each end of the range of motion of the head 220.
A hydraulic line 260 provides water under high pressure to the head 220. The head support assembly 200 is typically limited to a predetermined number of revolutions about the axis XX to ensure that the hydraulic line is not severed or otherwise damaged. Accordingly, the head support assembly 200 is typically operated to rotate about axis XX in a clockwise direction, followed by a change of rotational direction to commence anti-clockwise rotation and vice versa.
The jig 100 includes a lower jig assembly 300 having a support shaft 310 which extends along axis XX. The shaft 310 is pivotally connected to the head support assembly 200 with self aligning bearings 312, which enable the head support assembly 200 to rotate independently relative to the lower jig assembly 300.
As shown in Figs. 1 and 2, the lower jig assembly 300 is operationally similar to the upper jig assembly 102, however in the initial, pre-expanded configuration, the locating legs 140 face generally opposing directions.
The operation of the support jig 100 will now be described. When an accumulated layer of coke requires removal from a riser pipe within an oil refinery, the lifting lug 112 is mounted on a chain sling to an overhead gantry crane or hoist (not shown). The crane is used to raise the jig 100 to the desired location such that the head 220 is generally adjacent to the region of the riser wall to be cleaned or descaled. The six legs 142 of both the upper and lower jig assemblies 102, 300 are expanded by actuating each of the sets of double acting hydraulic cylinders 150. Once the legs 142 are in positive contact with the wall of the riser 101, the upper and lower jig assemblies 102, 300 are prevented from rotating about the axis XX. The legs 142 provide a bracing function, and at this stage, the cutting/cleaning operation may commence. The operation and movement of the cutting head 220 is remote controlled, ensuring that a worker does not need to be present in the riser pipe.
The motion of the cutting tip 226 follows a complex, controlled path. This is governed by the movement of the stem 224 through either a circular or conical path. In addition, the head 220 and hence the cutting tip 226 is also moved by the chain drive 230. In addition, the drive motor 210 controls the rotation of the head support assembly 200 about axis XX. The combination of the axial and rotational movement permits the water blaster cutting tip 226 to treat all regions around the circumference of the wall of the riser 101.
When treatment of a portion of the riser wall has been completed, the legs 142 are retracted, and the crane may be used to raise or lower the jig 100 to a new location. A new portion of the riser can be treated by re-expanding the legs 142.
In one embodiment not shown in the drawings, the lower jig assembly 300 is not used. In contrast, the lower end of the head support assembly 200 is attached to a fixed structure such as an eyelet located at the base of the riser tube 101.
Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.