Claims:WE CLAIM:

1. A dry slot cutting machine (100) for making slots on the skirt (4) of the coke drum, the machine (100) comprising:
a slide assembly (101) having,
a first slide mechanism operably coupled with a linear guide rail and a linear guide rail block, the first slide mechanism having a guide way slide base, a carriage, a bearing house, a programmable motor, a mounting plate, at least two bellows at both ends and a switch, wherein the first slide mechanism is secured on the horizontal axis, and
a second slide mechanism secured diagonally to the first slide mechanism, the second slide mechanism having a lead screw-nut assembly;
a slide feed assembly, the slide feed assembly having a nut holding bracket, a graduation collar, a screw rod mounting bracket, a spacer and a screw rod, wherein the control panel (104) is adapted to control the movement of the slide assembly (101); and
an air-cooling system configured to keep the machine (100) cool from the hot surface of the skirt (4);
a spindle assembly (102) having,
a spindle head mounted on a cross head mounting bracket by means of the linear guide rail block of the first slide mechanism, the spindle head is adapted to hold a cutting tool, and
a drive mechanism having a shaft (106) with an AC motor, the drive mechanism sweeps the spindle head in predetermined directions;
a clamping assembly (103), the clamping assembly (103) is adapted to hold the spindle head on the front facing exterior surface of the skirt (4) and provides a mounting provision for the first slide assembly, the clamping assembly (103) having a plate assembly, a block assembly, a plurality of guide shafts (113), a plurality of pillow blocks (114), a plurality of pillow block base (123), a connecting plate (115), a leveling stud-nut assembly, a spherical washer (118), a top plate (119) and a clench assembly (103a); wherein,
the plate assembly having a front plate (107) and a rear plate (108);
the block assembly having a left-front block (109), a right-front block (110), a left-rear block (111) and a right-rear block (112); and
the clench assembly (103a) having a plurality of bush (120) and a plurality of locking studs (121) with adjacent locking nuts (122);
an operating unit (105) with a control panel (104) operably connected to the spindle assembly (102) and the slide assembly (101);
whereby, when the control panel (104) allows the slide assembly (101) to move in predetermined direction by means of the slide feed assembly, the spindle assembly (102) travels along with the slide assembly (101) to the preferred slot making location, and then the cutting tool makes slots of preferred depth on the exterior surface of the skirt (4) by means of the drive mechanism.
2. The machine (100) claimed in claim 1, wherein the spindle head is a right angle miniature spindle crosshead.
3. The machine (100) claimed in claim 1, wherein the clamping assembly (103) is a square tubular structured ?xture assembly.
4. The machine (100) claimed in claim 1, wherein the programmable motor in the first slide mechanism is a stepper motor.
5. The machine (100) claimed in claim 1, wherein the guide way slide base is an aluminum guide way slide base.
6. The machine (100) claimed in claim 1, wherein the control panel (104) is configured with a programmable logic control (PLC) IC.
7. The machine (100) claimed in claim 1, wherein the clamping assembly (103) along with the slide feed assembly allows the spindle head to apply at least three slots per machine per shift with precise depth cut.
Dated this on 20th day of April 2021
Prafulla Wange
(Agent for the applicant)
(IN/PA-2058)
, Description:DRY SLOT CUTTING MACHINE FOR MAKING SLOTS ON COKE DRUM SKIRT
FIELD OF THE INVENTION:
The present invention relates to the field of the oil refinery processing unit and, more particularly, the present invention relates to the dry slot cutting machine for making slots on the skirt of the coke drum of the refinery coker unit.
BACKGROUND OF THE INVENTION:
Delayed coking is one of the unit processes used in many oil refineries. Coke drum is an integral part of coker units and serves as the final step in the cracking process. The coke drum typically consist of a top head, a cylindrical drum, a conical bottom, and skirt support as shown in Fig. 1. The inner surface of the top head, the cylindrical drum and the conical bottom is directly subjected to varying pressures and temperatures, as well as steam, oil vapors, hot oil, petroleum coke and water. Thus, these components are commonly referred to as pressure components. The skirt support is used to support the vessel on a raised platform to allow the petroleum coke to exit through the conical bottom head at the end of each process cycle.
Presently, the most conventional type of the skirt for the coke drums is an insulated cylindrical shell joined tangentially with the vertical portion of the vessel by a continuous fillet weld. The continuous fillet weld on the coke drums is susceptible to the fatigue failure due to the severe thermal cyclic stresses. There is a known method to decrease the junction stress is to add a plurality of slots near the top of the skirt, thereby reducing the local stiffness close to the weld. The common skirt slot design is thin relative to its circumferential spacing which is normally designed by a process licenser.
Normally, such slots on the skirt of the coke drum are made using a flame cutting process. In the flame cutting process, the refinery plant is required to be taken under shutdown to perform the slot cutting activity. The major challenge with the flame cutting process is to maintain the required safety as many hydrocarbon particles are present in the refinery atmosphere in the form of vapor. Another challenge is to maintain the required dimensions of the slots as the flame cutting process does not give the required dimensional accuracy. Further, the inaccuracy in the slots generates a wide Heat Affected Zone (HAZ) which needs to be removed after the cutting operation by other manual processes like grinding. Additionally, the flame cutting process is not consistent as it is influenced by various parameters such as torch nozzle, plate surface conditions and the like.
Accordingly, there exists a need to provide dry cutting technology to perform the slotting on the skirt of the coke drum for hazardous refinery working environment.
OBJECTS OF THE INVENTION:
An object of the present invention is to provide a portable, light weight, compact and robust machine to perform slot cutting on the skirt component of the coke drum.
Another object of the present invention is to make slots on the front side in heavy skirt component of the coke drum.
Another object of the present invention is to cut the slots on the skirt during running equipment in the live plant of the delayed coker unit of the refinery.
Another object of the present invention is to achieve the required geometric tolerances on the slots of the coke drum skirt.
Still another object of the present invention is to design a mounting arrangement of the machine on the skirt of the coke drum to avoid any hot weld work on the pressure parts and/or the skirt support.
Yet another object of the present invention is to provide a front side quick clamping for installing a dry slot machine on the skirt of the coke drum.
SUMMARY OF THE INVENTION:
The present invention provides dry cutting technology to perform the slotting on the skirt of the coke drum for hazardous refinery working environment.
The dry slot cutting machine comprises a slide assembly, a spindle assembly, a clamping assembly, an operating unit and a control panel. The slide assembly comprises a first slide mechanism secured on the horizontal axis and a second slide mechanism secured diagonally to the first slide mechanism. The spindle assembly consists of a spindle head with a cutting tool and a drive mechanism thereof. The spindle head cutting tool makes slots on the skirt of the coke drum. The clamping assembly provides front side clamping for installing the dry slot cutting machine on the outer surface of the skirt of the coke drum.
BRIEF DESCRIPTION OF THE DRAWINGS:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows a coke drum of the coker unit, in accordance with the present invention;
Figure 2 shows an overview of a dry slot cutting machine, in accordance with the present invention;
Figure 3 shows an isometric view of the dry slot cutting machine, in accordance with the present invention;
Figure 4 shows a top view of the dry slot cutting machine, in accordance with the present invention;
Figure 5 shows clench assembly with adjacent lock nut assembly for clamping the dry slot cutting machine, in accordance with the present invention; and
Figure 6 shows a pillow block base and a leveling nut assembly for clamping the dry slot cutting machine, in accordance with the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a dry slot cutting machine for the skirt of the coke drum. The dry slot cutting machine provides slots on the circular surface of the coke drum skirt from the outside of the coker unit.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate the corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to Figures from 1-6, there is shown a typical coke drum comprises a top head (1), a cylindrical drum (2), a conical bottom (3), a skirt support (4) and an insulation layer (7). The skirt support (4) includes a skirt (5) and foundation anchoring (6). Additionally, an alternate drainpipe (8) is configured to be installed outside of the skirt support (4). In an exemplary embodiment, the gap available between the skirt (5) and an alternate drainpipe (8) is about 200 mm.
A dry slot cutting machine (hereinafter ‘the machine (100)’) is mounted on the exterior surface of the skirt (4) capable of making slots thereon. The machine (100) comprises a slide assembly (101), a spindle assembly (102), a clamping assembly (103), a control panel (104), and an operating unit (105). Further, the machine (100) has total width of 196.8 mm which can be accommodated in between the 200 mm gap from the alternate drainpipe (8) to the outside surface of the skirt (4).
The slide assembly (101) comprises a first slide mechanism, a second slide mechanism, a slide feed assembly and an air-cooling system. The first slide mechanism is secured on the horizontal axis. In an exemplary embodiment, the first slide mechanism is secured in the X-axis. Further, the first slide mechanism includes a guide way slide base, a carriage, a bearing house, a programmable motor, a mounting plate, at least two bellows at both ends and a switch. In an exemplary embodiment, the guide way slide base is an aluminum guide way slide base and the programmable motor is a stepper motor.
Additionally, the first slide mechanism is operably coupled with a linear guide rail and a linear guide rail block via the carriage for precise motion of the carriage thereof. The carriage feed is provided through the rolled ball screw and nut. In an exemplary embodiment, the least count of the screw rod is 0.02 mm/division. The second slide mechanism is secured diagonally to the first slide mechanism. In an exemplary embodiment, the second slide mechanism is secured in the Z-axis. The second slide mechanism has a lead screw-nut assembly. In another exemplary embodiment, the first slide mechanism has a long stroke of 500+ mm, and the second slide mechanism has a stroke of 70+ mm.
The slide feed assembly is operably mounted on the first slide mechanism and the second slide mechanism. The slide feed assembly includes a nut holding bracket, a graduation collar, a screw rod mounting bracket, a spacer and a screw rod. The air-cooling system is configured to keep the machine (100) cool from the hot surface of the skirt (4), where the temperature may be about 150 degree centigrades.
The spindle assembly (102) comprises a spindle head and a drive mechanism. The spindle head is mounted on a cross head mounting bracket by means of the linear guide rail block of the first slide mechanism. In an exemplary embodiment, the spindle head is a special right angle miniature spindle crosshead. The spindle head is adapted to hold a cutting tool. The drive mechanism sweeps the spindle head in predetermined directions. Further, the drive mechanism comprises a shaft (106) and an AC motor. The shaft (106) is a flexible shaft for operably coupling the AC induction motor to the spindle head. Further, the AC motor is operably coupled with the screw rod of the slide feed assembly.
In an exemplary embodiment, the spindle assembly is a spindle design for the collet DIN-6499 with the maximum possible spindle speed of 500 RPM. The cutting tool is a solid carbide end-mill cutter operably coupled with the spindle head for slotting operation. Further, the spindle head is made with a tool holding capacity of 1 mm to 13 mm and with gear ratio 1:1. Additionally, the spindle assembly (102) has stringent tolerance of running out in order to achieve precise tolerance on slots, for example, 30 microns +/- 0.5 mm. The maximum depth of cut given by means of the cutting tool may be 0.6 mm and feed rate of 300 mm/min. Further, the AC induction motor has a speed of 3000 RPM.
The clamping assembly (103) is configured to hold the machine (100) on the front face of the skirt drilled surface. The clamping assembly (103) is a square tubular structured ?xture assembly for clamping the machine (100) directly on the outer surface of the skirt (4). The clamping assembly (103) comprises a plate assembly, a block assembly, a plurality of guide shafts (113), a plurality of pillow blocks (114), a plurality of pillow block base (123), a connecting plate (115), a leveling stud-nut assembly, a spherical washer (118), a top plate (119) and a clench assembly (103a) as shown in Fig. 3.
The plate assembly includes a front plate (107) and a rear plate (108). The block assembly includes a left-front block (109), a right-front block (110), a left-rear block (111) and a right-rear block (112) as shown in Fig. 3. The clench assembly (103a) facilitates the initial mounting of the machine (100) on the skirt (4). Further, the clench assembly (103a) includes a plurality of bush (120) and a plurality of locking studs (121) with adjacent locking nuts (122) as shown in Fig. 5. The leveling stud-nut assembly comprises a front leveling stud-nut (116) and a rear leveling stud-nut (117) as shown in Fig. 4 and 6. The front leveling stud-nut (116) provides adjustment to the first slide mechanism and the rear leveling stud-nut (117) provides adjustment for mounting of the machine (100) to the skirt (4). The pillow blocks (114) along with the leveling stud-nut assembly and the plurality of locking studs (121) with adjacent locking nuts (122) are configured for providing linear pitch adjustment and angular adjustment of the machine (100).
The control panel (104) is mounted on the operating unit (105) as shown in Fig. 2. The control panel (104) is adapted to control the movement of the slide assembly (101). Further, the control panel is configured with a programmable logic control (PLC) IC. The operating unit (105) with a control panel (104) operably connected to the spindle assembly (102) and the slide assembly (101).
The present invention further provides a dry cutting process for making slots of the skirt of the coke drum. In the first stage, the process includes marking of the slots to be cut on the skirt (4) and then drilling holes on the skirts as per the marking. In the second stage, the machine (100) is mounted by means of the clamping assembly (103) in the holes drilled on the exterior surface of the skirt (4) for cutting slots. The dry cutting process is controlled using the control panel (104) along with the operating unit (105). In the third stage, the dry cutting process allows the slide assembly (101) to move in predetermined direction by means of the slide feed assembly along with the control panel (104) of the machine (100). Then, the spindle assembly (102) travels along with the slide assembly (101) to the preferred slot making location. After which, the cutting tool makes slots of preferred depth on the exterior surface of the skirt (4) by means of the drive mechanism. The clamping assembly along with the slide feed assembly allows the spindle head to apply at least three slots per machine per shift with precise depth cut.

Advantages of the invention:
1. The machine (100) of the present invention is a 100% dry cutting process which works on the coke drum during a running plant.
2. The machine (100) of the present invention is portable, light weight and compact, which makes it easy to install and move from one slotting location to the other.
3. The machine (100) of the present invention is a safe dry slot cutting process as it does not generate any flame or spark.
4. The machine (100) of the present invention is capable of achieving the desired dimensional tolerances required on the slot.
5. The machine (100) of the present invention is capable of providing slot cutting at a space constraint location.
6. The machine (100) of the present invention uses quick clamping capability on the job without any attachment of weld on the skirt and with quick alignment using the leveling mechanism.
7. The machine (100) of the present invention is designed for continuous working on the running and live refinery equipment with a surface temperature of 150 degree centigrades.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.