Tài liệu Lesson 8-Workmanship for Hull Building(2) doc

Lesson 8-Workmanship for Hull Building(2)

4. Fabrication and Welding of Hull

When building a hull, we will normally divide the hull construction into a number

of components, which are termed as blocks or sections, assembled separately and then

fabricated into an integral hull on a berth or a slipway. This workmanship mainly

includes:

A: Part fabrication-to assemble different kinds of members into a whole part after

their processing.

B: Block or section fabricatiom-to assemble different parts into a block or section.

C: Berth or slipway fabrication-to assemble a few blocks and sections into an

integral hull.

4.1 Division of Sections

Division of sections is of great importance, for not only the strength of hull itself

but also the convenience and reasonableness of operation as well as the production

procedure, lifting capacity and arrangement of the working site have got to be taken into

our account. To make the matter worse, the aforementioned factors are frequently

contrary to one another in one way or another. Therefore, it is not rare for us to rack our

brains to find ways and means available.

4.2 Fabrication and Welding of Parts

The fabrication and welding of parts, such as frames, beams, girders and seatings,

to be performed on a platform in term of the concerned drawings.

4.3 Fabrication and Welding of Blocks and Sections

The fabrication and welding of blocks, such as side, bottom, deck and

superstructure, to be conducted on a jig. In respect to sections, two methods for their

fabrication and welding are available:

A: Pyramid Method

The practice of this method is as follows:

First, lift a bottom block onto a berth or a slipway and take it both as a base and a

jig. Then, assemble side blocks and bulkhead blocks. Still then, assemble the deck block.

By the pyramid method, all are done bit by bit through welding.

B : Converse Method

This method is good for bow section, stern section, deckhouse and superstructure,

the main characteristic of which is to regard the deck block on a berth or a slipway both

as a base and a jig. Thus framing blocks, bulkhead blocks and side girders will be erected

on the base of a deck block.

5. Tightness Test

Together with the completion of the whole integral hull construction, tightness

test is to be carried out so as to check the leakage of welding seams. In addition, water

pressure test may be executed for the hull structures that, by virtue of the technical

specification, are required to pass through strength test.

Tightness test is to be done only after the X-ray photo check of seams and the

completion of fabrication and welding in respect to pipe flanges and cable fixtures and so

on, but before the painting process for shell and compartments as well as the laying of

insulating materials. Tightness test to be subdivided into kerosene test, watertight test and

air-tight test.