WO2007015201A1

WO2007015201A1 - Transport and erection of very large vessels

Info

Publication number: WO2007015201A1
Application number: PCT/IB2006/052604
Authority: WO
Inventors: Edward Ludovicus Koper; Zbigniew Franciszek Matyja
Original assignee: Sasol Technology Pty Ltd
Current assignee: Sasol Technology Pty Ltd
Priority date: 2005-08-03
Filing date: 2006-07-31
Publication date: 2007-02-08
Anticipated expiration: 2008-02-03
Also published as: ITMI20061535A1; GB2444661A; JP2009502680A; DE112006002050T5; CN101237923A; AU2006274587A1; NL1032262C2; NL1032262A1; BE1017241A3; GB0803567D0; CN101237923B; KR20080046649A; ZA200801409B; BRPI0614189A2; ES2332695B1; ES2332695A1

Abstract

A method of preparing a very large vessel for transportation and/or erection includes at least partially filling the vessel with a flowable filler material which is, or which can be made to be, substantially solid, in order to stiffen the vessel for purposes of transportation and/or erection.

Description

TRANSPORT AND ERECTION OF VERY LARGE VESSELS

THIS INVENTION relates to the transport and erection of very large vessels.

In particular, it relates to a method of preparing a very large vessel for transportation and/or erection, to a method of transporting a very large vessel, and to a method of erecting a very large vessel.

Often, vessels required in chemical processing installations are large in diameter, long from end-to-end, and require internals e.g. heat transfer tubes. Typically, these vessels are pressure vessels, operating at sub-atmospheric or super-atmospheric pressures and also under other harsh conditions, e.g. very high temperatures. When such vessels are designed, all of the process conditions must be taken into account in addition to factors such as cost and ease of fabrication, transportation and erection.

One of the design specifications that must be determined when designing a vessel, and in particular when designing a very large vessel, is the vessel wall thickness. A minimum wall thickness can be determined, using a suitable formula or algorithm known to those skilled in the art, and taking into account factors such as operating pressures and temperatures, material of construction, the presence and location of nozzles and other vessel internals that must be attached to the vessel wall, and static and dynamic loads. Conventionally, allowances are then made to account for other forces to which the vessel may be subjected, e.g. during fabrication, transportation and erection, thus increasing the design thickness of the vessel wall. As will be appreciated, for some vessels, e.g. very large or very long vessels, the design vessel wall thickness using the above approach may be very thick as a result of allowances made for transportation and erection, making the manufacturing (e.g. welding and heat treatment) very difficult and expensive. This problem can be alleviated to a limited extent by making use of limited wall thickness allowances, internal braces, internal and/or external support rings and stiffeners, and the like, at the disadvantage of increased vessel mass, increased fabrication effort and costs, and transport and erection complications. According to a first aspect of the invention, there is provided a method of preparing a very large vessel for transportation and/or erection, the method including at least partially filling the vessel with a flowable filler material which is, or which can be made to be, substantially solid, in order to stiffen the vessel for purposes of transportation and/or erection.

In this specification, the term "very large vessel" is intended to refer to a vessel which has a length to diameter ratio of at least 5 and a diameter of at least 2 m. Also, a filler material which is "substantially solid", is meant to include gels, jelly-like substances, semi-solid substances and the like which are solid enough to stiffen a vessel to such an extent that a reduced design wall thickness can be used, compared to a case where the method of the invention is not employed. A flowable material which is solid, includes particulate materials and powders which, when compacted under its own weight in bulk, acts as a solid body.

Preferably, the entire vessel is filled with the flowable material. The entire vessel is thus preferably filled with a solid material thereby to stiffen the vessel for purposes of transportation and/or erection.

The vessel may include internals. The method may include immobilising the internals of the vessel with the filler material by submerging the internals in, or surrounding the internals with, the filler material.

The flowable filler material may be a fluid which can be solidified. The method may thus include solidifying, or allowing solidification, of the flowable filler material in the vessel.

In one embodiment of the invention, the flowable filler material is a material which is normally solid at ambient conditions, but which is flowable at elevated temperatures, e.g. a hydrocarbon such as a Fischer-Tropsch derived wax. The method may thus include filling the vessel with a hydrocarbon which is at a temperature which allows it to flow, and then solidifying, or allowing solidification, of the hydrocarbon, e.g. by removing heat from the hydrocarbon. The flowable filler material, e.g. the hydrocarbon, may include a catalyst for a process in which the vessel is to be used. Thus, advantageously, for some process vessels and processes, the vessel may be preloaded with a filler material which is to be used in the process, and which may even include a catalyst, the preloading of the vessel also serving to stiffen the vessel for transportation and/or erection purposes. In order to put the vessel, after erection, into operation, the solid filler material, e.g. the wax, can be converted to a fluid again, e.g. by melting the wax by means of the addition of heat.

In another embodiment of the invention, the flowable filler material is a material which is normally a liquid at ambient conditions, but which solidifies at sub- ambient conditions, e.g. water or chilled water. The method may thus include cooling the flowable filler material in the vessel to a sub-ambient temperature at which the filler material is a solid, and maintaining the filler material at said temperature during transportation and/or erection.

Removal or addition of heat to the filler material can be effected through the wall of the vessel. Instead, or in addition, when the vessel includes internals suitable for such purposes, such as heat transfer tubes or coils, these can be employed.

In a further embodiment of the invention, the flowable filler material is a particulate material. Examples of such particulate materials include mineral or ore particles, sand, sawdust and particles of a natural or synthetic plastics or polymeric material, such as rubber, polystyrene, polypropylene, polyethylene or ABS beads. Advantageously, when a particulate material is used, it is unnecessary to change the state of the material in order to stiffen the vessel or for purposes of removal of the filler material from the vessel.

In yet another embodiment of the invention, the flowable filler material is a foam-producing fluid, which foam can be solidified. The method may thus include filling the vessel with a foam and solidifying the foam. The method may also in this case include coating surfaces inside the vessel with a foam-release assisting compound. In order to remove the solid foam from the vessel, the foam may be chemically dissolved using a suitable solvent or reagent, or mechanically or physically broken down, e.g. by sandblasting, shot-blasting or the use of ultrasound.

The method may include treating surfaces inside the vessel to protect the surfaces against the filler material, e.g. to protect the vessel interior surfaces and exterior surfaces of vessel internals against corrosion and/or erosion. Treating the surfaces may include coating the surfaces with a protective coating.

The method may include treating the filler material to reduce or eliminate possible harmful effects of the filler material on the materials of construction of the vessel and/or its internals, when present. For example, the filler material may be admixed with a corrosion inhibitor.

According to a second aspect of the invention, there is provided a method of transporting a very large vessel, the method including preparing the vessel for transportation by at least partially filling the vessel with a flowable filler material which is, or which can be made to be, substantially solid, in order to stiffen the vessel; and transporting the vessel in a thus stiffened state to a desired location.

The vessel may be prepared in accordance with the method as hereinbefore described.

The method according to the second aspect of the invention may include loading the vessel, in its stiffened state, onto a vehicle in order to transport the vessel. The method may also include offloading the vessel, in its stiffened state, from the vehicle, once transported to the desired location.

According to a third aspect of the invention, there is provided a method of erecting a very large vessel, the method including preparing the vessel for erection by at least partially filling the vessel with a flowable filler material which is, or which can be made to be, substantially solid, in order to stiffen the vessel; and erecting the vessel in a thus stiffened state. Erecting the vessel may include turning the vessel from a manufacturing or transport orientation, through an angle in a vertical plane, to an operative orientation. Typically, the vessel is turned through a 90 ° angle, about an axis transverse to the vessel.

The method according to the third aspect of the invention, may include removing the filler material from the vessel, once erected. Removing the filler material from the vessel may include treating the filler material, if necessary, to make the filler material again flowable. Treating the filler material may include heating the filler material, e.g. to melt the filler material.

The method according to the third aspect of the invention may also include treating the filler material and/or the vessel, to facilitate removal of the filler material from the vessel. Treating the filler material and/or the vessel to facilitate removal of the filler material from the vessel may include applying vibratory forces to the filler material and/or the vessel, and/or mechanically working the filler material, e.g. with chains, pokers, stirrers, shavers, augers or the like.

Instead of removing the filler material from the vessel once the vessel is erected, the method according to the third aspect of the invention may include treating the filler material to make it suitable for use in the vessel in a process in which the vessel is to be employed. Thus, the filler material may be a reagent, product, catalyst or inert component normally present in the vessel in a process in which the vessel is to be employed, such as a Fischer-Tropsch synthesis process.

The invention will now be described, in more detail, with reference to the following example.

EXAMPLE

A very large circular cylindrical vessel with a diameter of about 10 m and a length of about 60 m and which includes internals like steam coils was designed to be transported as one complete piece of process equipment. As will be appreciated, this means that the pressure vessel would have all point loads present during transportation and erection.

Using a conventional pressure vessel design code for the design operating temperature and pressure of the very large vessel, the wall thickness of the pressure vessel was calculated to be between 66 and 76 mm. For fabrication, transport, mass and cost reasons it is preferred to select the lower thickness of 66 mm. To allow for the thinner wall thickness, a special constructions material was selected which is approximately 20 % stronger per mass unit than the carbon steel which would normally be used for the process conditions under which the very large vessel would be used. One of the conditions for the selection of the thinner wall thickness and the special construction material is that the shape of the vessel must stay as close as is possible to the original design shape, i.e. that the vessel must remain circular cylindrical.

The combined factors of the length to diameter ratio of the vessel, the selected wall thickness, the point loads, the installed internal equipment of the pressure vessel and the need to transport and erect the pressure vessel without buckling the shell or even distorting the shape of the shell require special measures to be taken to ensure that no damage is done or shape changes occur. The conventional engineering solution to this problem is to opt for a thicker shell which would result in an approximately 25 % thicker wall for a design in standard carbon steel. This would make the fabrication, especially the welding and heat treatment, and the handling of the pressure vessel, very difficult.

By means of the invention, the stiffness of the vessel can be increased thereby ensuring that the pressure vessel does not buckle or distort during handling, transportation and erection and allowing the pressure vessel to have a wall thickness of 66 mm only. For the particular process vessel of the Example, it is envisaged that the vessel would be filled with a liquid wax which would be allowed to solidify before the vessel is transported and erected. As will be appreciated, by using a settable liquid, such as a wax, the internals of the pressure vessel are completely immobilised. Advantageously, the wax, which is envisaged to be a Fischer-Tropsch derived wax, may include a Fischer-Tropsch catalyst as the vessel is intended for use in a Fischer- Tropsch process. Once the vessel has been erected, the Fischer-Tropsch wax can be melted by the application of heat, e.g. by circulating steam through the installed steam coils, whereafter the pressure vessel can be commissioned with the Fischer-Tropsch derived wax and the Fischer-Tropsch catalyst already present in the vessel.

Claims

CLAIMS:

1. A method of preparing a very large vessel for transportation and/or erection, the method including at least partially filling the vessel with a flowable filler material which is, or which can be made to be, substantially solid, in order to stiffen the vessel for purposes of transportation and/or erection.

2. The method as claimed in claim 1 , in which the entire vessel is filled with the flowable material.

3. The method as claimed in claim 1 or claim 2, in which the vessel includes internals, the method including immobilising the internals of the vessel with the filler material by submerging the internals in, or surrounding the internals with, the filler material.

4. The method as claimed in any one of the preceding claims, in which the flowable filler material is a fluid which can be solidified, the method thus including solidifying, or allowing solidification, of the flowable filler material in the vessel.

5. The method as claimed in any one of the preceding claims, in which the flowable filler material is a material which is normally solid at ambient conditions, but which is flowable at elevated temperatures.

6. The method as claimed in any one of the preceding claims, in which the filler material is a hydrocarbon, the method thus including filling the vessel with said hydrocarbon which is at a temperature which allows the hydrocarbon to flow, and then solidifying, or allowing solidification, of the hydrocarbon.

7. The method as claimed in any one of the preceding claims, in which the flowable filler material includes a catalyst for a process in which the vessel is to be used.

8. The method as claimed in any one of claims 1 to 4 inclusive, in which the flowable filler material is a material which is normally a liquid at ambient conditions, but which solidifies at sub-ambient temperatures, the method thus including cooling the flowable filler material in the vessel to a sub-ambient temperature at which the filler material is a solid, and maintaining the filler material at said temperature during transportation and/or erection.

9. The method as claimed in any one of claims 1 to 3, in which the flowable filler material is a particulate material.

10. The method as claimed in any one of claims 1 to 4 inclusive, in which the flowable filler material is a foam-producing fluid, which foam can be solidified, the method thus including filling the vessel with a foam and solidifying the foam.

11. A method of transporting a very large vessel, the method including preparing the vessel for transportation by at least partially filling the vessel with a flowable filler material which is, or which can be made to be, substantially solid, in order to stiffen the vessel; and transporting the vessel in a thus stiffened state to a desired location.

12. The method as claimed in claim 11 , in which the vessel is prepared in accordance with the method as claimed in any one of the claims 1 to 10 inclusive.

13. The method as claimed in claim 11 or claim 12, which includes loading the vessel, in its stiffened state, onto a vehicle in order to transfer the vessel, or unloading the vessel, in its stiffened state, from the vehicle once transported to the desired location.

14. A method of erecting a very large vessel, the method including preparing the vessel for erection by at least partially filling the vessel with a flowable filler material which is, or which can be made to be, substantially solid, in order to stiffen the vessel; and erecting the vessel in a thus stiffened state.

15. The method as claimed in claim 14, in which erecting the vessel in a thus stiffened state includes turning the vessel from a manufacturing or transport orientation, through an angle in a vertical plan, to an operative orientation.

16. The method as claimed in claim 14 or claim 15, which includes removing the filler material from the vessel, once erected.

17. The method as claimed in claim 14 or claim 15, which includes treating the filler material to make it suitable for use in a process in which the vessel is to be employed.

18. The method as claimed in any one of claims 14 to 17 inclusive, in which the vessel is prepared in accordance with the method as claimed in any one of claims 1 to 10 inclusive.