CONSTRUCTION OF PIPING BULK MATERIALS

The parameters that can modify the curve of construction (feasibility) at site are availability of materials, availability of documents and areas ready for work.

The availability of materials depends on the completeness of material take offs, the purchasing requisitions issue, the preparation of purchasing orders (vendor selection, technical appraisal, negotiation), delivery time, transportation time, storage at warehouse.

The availability of construction documents is in line with the progress of the detailed engineering.

The areas ready to work are those part of plant where the facilities to erect the bulk materials have been completed (i.e. piperacks, structures, equipment, paved areas, sleepers, etc.).

The task is to guarantee the curve of construction planned (in terms of weight or manhours) in order to avoid the stand-by of the mechanical contractor.

1. Materials

Because of the delivery and transportation time the bulk materials have to be ordered before the completion of the detail engineering. For this reason we plan two material take offs in the early stage of the project that are an estimation of the whole bulk necessary. The base for the estimation are the P&ID and the plot plans, usually some preliminary layout study are performed to verify the need of the critical material (critical for cost or delivery time). The estimation can be done manually or through computer programmes like P&ID 2D and Autorouting Programmes. It is good practice to compare such estimation with the expected quantity from statistical data.

Particular attention is given in the first MTO to the material for prefabrication in shop (pipes, elbows and fittings).

2. Documents

The documents delivered at site in the early stage of project are those necessary for the preparation for piping erection: plot plans, structure drawings, sleeper plans, paved areas.

The first set of document to be issued is the underground network composed of foundation system, sewer system, closed drain system and paved areas plans.

During the erection of the structures the prefabrication of the pipe spools can start, at this stage the site needs the pipe isometrics. The piping erection begins when the structures and the equipment are installed and it is necessary to deliver at site the piping arrangement areas.

The feasibility is the activity that compare the curve of construction planned with materials and documents available. Particular computer programmes runs simulation to cross material and isometrics to evaluate how many of them can be completed. Also these programmes give the situation of the material not yet arrived at site or not yet purchased.

The reduction in plant completion time pushes the integration between mechanical completion and commissioning, so the goal is to focus the completion of full circuits instead of single lines. The simulation programmes and the piping modelling programmes have been modifying in this direction.