All modern shipyards across the world have identified that by adopting the concept of advance outfitting the building cycle time can be reduced and there will be substantial cost savings along with other benefits. Depending on the infrastructure available in the yards different concepts were developed for completion of outfitting in block-stage to derive the benefits.
1) UNITISATION CONCEPT
Even before the hull block is made, the outfit components (machinery/piping/seats etc) in a particular small area are made into a small unit (fully assembled) and when the hull block is made, this unit is directly installed on the block. Hence the steel structure and outfitting units are made simultaneously as parallel activities which reduce cycle time.
Block-outfitting involves the erection of the units (assembled components) described above and also other heavy machinery etc on large blocks before erection and joining of these blocks. However, consideration to be given to the limitation of the total weight that can be handled by the craneage facilities available in the yard.
By this, process the advantages of a) down hand welding, b) open-sky access for erection of machinery & c) better working conditions can be realised.
3) GROUP TECHNOLOGY/ WORK-STATIONS/PRODUCT work breakdown structure:
a) The basic principle of group technology involves identification of sub-divisions of a product, which although not necessarily identical, are produced by the same processes or operations. For example, on the ship, in the engine room area, a unit can be a machinery component along with connected piping and its seat and there can be several such units where identical work is involved. Hence group technology involves identification of interim products/units which can be handled by the same type of processes.
b) The application of group technology principle to ship-building leads to the subdivision of the ship onto rational sub-division of work so that the interim products so identified can be manufactured in groups within the facilities which are specially designed for their most effective manufacture. The subdivision of the ship in this way is known as product work breakdown structure (PWBS) and the specialised design of the workstation including appropriate tooling, easier planning of work, to maintain steady workload and increased operator performance.
There can be similar interim products, even on dissimilar vessels, and hence the advantage of repeat work can be obtained with workstation concept even with a different type of ship.
4) ZONE OUTFITTING:
Zone outfitting is a larger term used for outfitting a) on-unit b) on-block c) on board.
A zone might correspond to a component or even an integral part of a compartment such as a cargo hold or machinery space and their subdivisions. An entire super-structure or just one level of superstructure could be a zone. hence a zone is a subdivision selected for convenience of outfitting either on a unit or on a block or on board.
A) Outfitting on-unit is the assembly of an interim product of a system consisting of manufactured and purchased materials/components and does not include any hull structure. For example, a unit can be a machinery mounted on its seat along with connected piping completely assembled and can be transported and erected on the block as a single unit. (unitisation concept)..
B) Outfitting on-block is the installation of outfit components (machinery with seats, piping, electrical cables, ventilation trunks, etc.,) after hull block is completed either as separate components or after unitisation as described in 4.A above.
However, the concept of unitisation provides the advantage of fabricating hull blocks and unitisaing the outfitting components to go parallelly whereas erection of outfit components after fabrication of blocks will take a long time since they are series activities.
C) Outfitting on board is limited to the erection of heavy machinery and for connection/welding of outfitted blocks.
D) Other zones of outfitting include accommodation blocks, stern blocks etc which are separated in specialised areas of the yard and erected to the other structures as single units.