DESC:“METHOD OF PREPARATION OF METALLIC LINER SEGMENTS INSIDE PROCESS EQUIPMENT FOR IN-SITU REPLACEMENT”

Field of the invention

The present invention relates to a method of replacing old or damaged liner segments inside a process plant equipment and more specifically, to a method of using a customized modular unrolling machine for in-situ preparation of new cylindrical radius liner segments of required dimensions and shape inside a constrained space of the process plant equipment.

Background of the invention

Equipment used in petrochemical and fertilizer plants handle process solutions like ammonium carbamate, urea in aqueous solutions, etc. At extreme operating temperatures and pressures, these fluids are extremely aggressive on carbon steel and low alloy steel. To overcome this problem these equipments are lined with a good corrosion resistant material. The external pressure resistant vessel is made of carbon or low alloy steel while the lining in contact with a process solution is made of urea grade stainless steel, zirconium, titanium and the like. A lining is defined as ‘loose’ as it is secured to an inner surface of an external reactor body only by welding at the edges of the liner segments and not so intimately connected to it as in case of cladding or weld overlay.

After many years of continuous operation, lined equipment develops leaks from its loose lining due to combined action of erosion and corrosion. Attack mainly occurs at the welds, the point of chemical and metallurgical discontinuity, and a small hole in the lining can quickly lead to perforation in the external carbon steel/ alloy steel pressure vessel. This can have potentially serious consequences for the future operation of the plant and to the safety of the plant personnel. The normal way to detect leaks in the equipment lining is to monitor a network of small weep holes drilled through the pressure resistant body of the vessel. Leaks in loose liner segments are difficult to repair. Welding of these liners requires highly skilled specialists under carefully controlled conditions and is not easy to done inside the equipment during a short shutdown of the process plant.

When leaks continue to appear, the most effective option is to replace the whole equipment. These equipments have a typical life of 10-20 years depending on how well the plant is operated and maintained. Shorter lives are not uncommon.

An alternative option to replacement of whole equipment is to repair or replace the liner segments only. Repair is done by local weld build up or local patch piece welding.

Replacement of liner is conventionally done in two ways:
i) Large sized liner segments, which are in the range of 1500 mm to 2000 mm, cannot be taken inside equipment through small manhole of 500 mm diameter. Hence, the liner segments are made in smaller pieces that can be taken inside through manhole and welded inside the equipment. This method has certain drawbacks like longer lead time, additional non-destructive testing of weld joints and more importantly a compromise on the liner configuration. Single piece liner segment is always better than multiple smaller welded liner segments.
ii) External carbon or low alloy steel pressure vessel is cut and separated to facilitate replacement of large original sized liner segments inside a shell assembly. After relining of the equipment, the pressure vessel is rejoined by welding a new seam followed by stress relieving and non-destructive testing. Once again the drawback of this method is a large lead time and mobilizing of resources at site for this mammoth task.

Accordingly, there exists a need to provide a method for preparation of metallic liner segments in a single piece inside a process equipment for replacing the old or damaged liners, which would be alternate to above two options and overcome the above-mentioned drawbacks.

Objects of the invention

An object of the present invention is to provide a method of preparation of new metallic liner segments in a single piece of original size for replacing old or damaged liner segments inside a process equipment in service, during shutdown without disturbing an external pressure vessel boundary of the process equipment and without cutting, welding and non-destructive testing (NDT).

Another object of the present invention is to provide a customized modular unrolling machine which can be transferred inside the process equipment through a small manhole having a minimum diameter of 500 mm which can do preparation of liner segments for replacement.

Summary of the invention

Accordingly, the present invention provides a method of preparation of metallic liner segments inside a process equipment for in-situ replacement. The method comprises transferring and assembling a modular unrolling machine inside the process equipment. The modular unrolling machine is transferred inside the process equipment through a manhole using any one of a crane and a hoist. The modular unrolling machine is mounted along with a motor and a gear box on a platform constructed inside the process equipment. Thereafter, electrical connections and testing operations of the modular unrolling machine are checked. Further, the liner segment rolled to a smaller radius is transferred into the process equipment. The liner segment rolled to the smaller radius is unrolled to a final required radius using the modular unrolling machine inside the process equipment. After completion of the unrolling, the prepared liner segment unrolled to the final required radius is removed from the modular unrolling machine. The modular unrolling machine and the platform are then removed from the process equipment. The liner segment unrolled to the final required radius is fixed with the process equipment by welding.

Brief description of the drawings

Figure 1 shows a flowchart of method of preparation of metallic liner segments inside a process equipment for in-situ replacement, in accordance with the present invention;

Figure 2 shows a cross-sectional view of the process equipment showing a modular unrolling machine being transferred inside the process equipment, in accordance with the present invention;

Figure 3 shows a cross-sectional view of the process equipment showing the modular unrolling machine being fixed on a platform along with a motor and a gear box, in accordance with the present invention;

Figure 4 shows transferring of a liner segment rolled to a smaller radius to facilitate entry into the process equipment through a manhole, in accordance with the present invention;
Figure 5 and 6 shows the smaller radius liner being unrolled using the modular unrolling machine to a required dimension, in accordance with the present invention; and

Figure 7 shows the modular unrolling machine being removed from the process equipment, in accordance with the present invention.

Detailed description of the invention

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.

Accordingly, the present invention provides a method of preparation of metallic cylindrical radius liner segments in a single piece of original size which are required to replace damaged or old liner segments inside an industrial process equipment. The old or damaged liner segments of the industrial process equipment in service are replaced during shutdown without disturbing an external pressure vessel boundary of the equipment. The new liner segment is rolled to a cylinder of smaller radius which is transferred through a manhole having a minimum diameter of 500 mm and then unrolled to a required large radius inside the process equipment using a modular unrolling machine. The modular unrolling machine is also transferred inside the process equipment through the manhole.

This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.

These reference numbers for a method of preparation of metallic liner segments for a process equipment comprising:
Table
Part No Part Name
100 Process equipment
10 Manhole
50 Platform
150 Modular Unrolling Machine
110 Liner segment rolled to a smaller radius
120 Liner segment unrolled to a required radius/dimension

Now referring to figures 1 to 7, a method (200) of preparation of metallic liner segments inside a process equipment (100) for in-situ replacement in accordance with the present invention is shown. The old/damaged liner segments are cut and removed from the process equipment (100) before in-situ replacement.

Figure 1 shows the detailed flow chart from steps (210) to (270). At step (210), the method (200) comprises transferring and assembling of a modular unrolling machine (150) inside the process equipment (100). The modular unrolling machine (150) is transferred inside the process equipment (100) through a manhole (10) as shown in figure 2 using any one of a crane and a hoist. The modular unrolling machine (150) is mounted on to a platform (50) constructed inside the process equipment (100) as shown in figure 3. The platform (50) is constructed depending upon the size of the process equipment (100). The modular unrolling machine (150) is assembled on the platform (50) along with a motor (not shown) and a gear box (not shown).

At step (220), the method (200) comprises checking electrical connections and testing operations of the modular unrolling machine (150). The modular unrolling machine (150) is assembled on the platform (50) along with the motor and the gear box with required electrical connections set up as per the instructions. Once the electrical connections are provided, testing is done to ensure proper operation of the modular unrolling machine (150) along with the motor and the gear box.

At step (230), the method (200) comprises transferring of liner segment rolled to a smaller radius (110) into the process equipment (100) (refer figure 4). The liner segment is transferred manually inside the process equipment (100). The liner segment is rolled to a radius smaller than the manhole (10) radius. The liner segment rolled to a smaller radius (110) facilitates insertion thereof inside the process equipment (100) through the manhole (10). In an embodiment, a flat liner is rolled to a smaller radius cylinder of 450-550 mm diameter depending upon the size of the manhole (10) for insertion therethrough. However, it is understood here that the dimension and material of the liner segment is selected as per the type of the process equipment (100).

At step (240), the method (200) comprises of unrolling of the liner segment rolled to the smaller radius (110) to a final required radius (120) using the modular unrolling machine (150) inside the process equipment (100) (refer figures 5-6). The radius of the liner segment (110) is checked periodically using a template while unrolling. In an embodiment, a cylindrical template having radius as that of the process equipment (100) is used to check the radius of the liner segment. Based on a gap between a template profile and liner profile rolling is done.

At step (250), the method (200) comprises removing the prepared liner segment unrolled to the final required radius (120) from the modular unrolling machine (150) after completion of the unrolling. The liner segment is removed manually from the modular unrolling machine (150).
At step (260), the method (200) comprises repeating the steps (230 to 250) until rest of the liner segments rolled to the smaller radius (110) inserted through the man hole (10) are unrolled with the modular unrolling machine (150) to the required dimensions.

At step (270), the method (200) comprises removing the modular unrolling machine (150) from the process equipment (100) (refer figure 7). The platform (50) is also removed from the process equipment (100). The liner segment unrolled to the final required radius (120) is then fixed with the process equipment (100) by welding.

Advantages of the invention:

1. The method (200) provides a solution to replace the damaged or old liner segments of the industrial process equipment without compromising on the original configuration of the liner i.e. liner segment in a single piece instead of multiple smaller pieces welded together.

2. The method (200) provides a solution to replace the damaged or old liners of the industrial process equipment without removing or disturbing the external pressure boundary of the process equipment (100) by cutting, re-welding and non-destructive testing (NDT).

3. The method (200) allows reshaping of new liner segments to a desired shape using the modular unrolling machine (150) inside the process equipment (100).

5. The method (200) does not require use of weld build up or patch piece welding which may reduce factor of safety or even worse the acceleration of new local areas of corrosion or erosion due to the introduction of a new fluid flow path.
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, 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 omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention. ,CLAIMS:We Claim:

1. A method of preparation of metallic liner segments inside a process equipment (100) for in-situ replacement, the method comprising the steps of:
transferring and assembling a modular unrolling machine (150) inside the process equipment (100), the modular unrolling machine (150) mounted along with a motor and a gear box on a platform (50) constructed inside the process equipment (100);
checking electrical connections and testing operations of the modular unrolling machine (150);
transferring of liner segment rolled to a smaller radius (110) into the process equipment (100);
unrolling of the liner segment rolled to the smaller radius (110) to a final required radius (120) using the modular unrolling machine (150) inside the process equipment (100);
removing the prepared liner segment unrolled to the final required radius (120) from the modular unrolling machine (150) after completion of the unrolling; and
removing the modular unrolling machine (150) and the platform (50) from the process equipment (100).

2. The method as claimed in claim 1, wherein the modular unrolling machine (150) is transferred inside the process equipment (100) through a manhole (10) using any one of a crane and a hoist.

3. The method as claimed in claim 1, wherein the liner segment unrolled to the final required radius (120) is fixed with the process equipment (100) by welding.

Dated this 22nd day of November, 2018
Prafulla Wange
(Agent for Applicant)
IN-PA/2058