Fabrication

CUTTING PLAN

The cutting plan shall be prepared for individual AFC piping isometric drawings by the piping engineer. Wherever field-welded joints are shown in the piping isometric drawings, a minimum of 200 mm extra length needs to be considered while making the cutting plan.

Cutting and beveling of pipes may be done by flame cutting, plasma cutting and machining by using CNC machine. The following shall be considered during cutting and beveling:

a) Carbon steel

Heat numbers shall be transferred by hard stamping or tagging or by any suitable method prior to blasting and primer application. CS pipe shall be blasted and primed prior to cutting. The cutting and beveling of CS will be done by the flame (oxyacetylene) torch or by CNC machine, and the oxides shall be removed from the surfaces by grinding to bright metal and paint. Grease and rust shall be removed nearer to the bevel ends, if there is any.

b) Low-alloy steel

The cutting and beveling of low-alloy steel shall be done by the flame (oxy/acetylene) torch, and after the flame cutting, a minimum of 2 mm of material shall be removed from the cut surface by grinding.

Fabrication 17

c) Stainless steel

The cutting and beveling of stainless steel shall be done by mechanical means using the cutting discs or by plasma cutting (for big size and thick wall) or by CNC machine, and then the surface shall be ground to the bright metal. All the grinding discs to be used for the stainless steel shall be iron free.

d) Galvanized materials

Galvanized material shall be cut using cold cutting methods.

The following shall be ensured during cutting and beveling activity:

DOs

• Pipes for socket weld joints shall be cut to square.
• Use SS wire brush for the cleaning of SS materials.
• Weld bevels for butt welds of pipes and fittings shall be as per ASME B16.25.

DON’Ts

• Don’t use CS stands/brackets/supports for cutting SS pipes.
• Don’t receive any unauthorized drawings/sketches that are not issued through DCC.

PCR shall establish the following reference documents in more detail: