Methodology Of Shop Fabrication Of Towers

Scope

Following are the Shop fabrication procedures of a Microwave tower, which may highlight the required material specifications and the working pattern of tower making leading us to provide better quality production in any project.

Applicable Codes & Standards

ASME Section II Part A, Part C
ASME Section V
AWS D 1.1
AISC Codes

Material for Fabrication

Locally available ASTM A-36 material of angles and plates shall be procured for fabrication.
Visual inspection shall be carried out of the material for corrosion, pitting and lamination. Mill test if required shall be performed to demonstrate material conformance to ASTM specifications in accordance with the contract requirement.

Welding Materials

The electrodes to be used shall be in compliance with the classification stated by ASME Sec. II Part C. After the electrodes have been removed from their sealed package, they shall be conditioned according to the supplier specifications. Wet electrodes or those with damaged coating shall be rejected.

Straightening

Before marking-off, steel angles, plates shall be cranked for conformity with the standards. Any damaged or distorted material shall be replaced. Steel plates may be repaired or corrected by the use of controlled heating and mechanical straightening, subject to the limitation of the AISC specifications. If special requirements demand tolerances more restrictive than allowed by ASTM A-6 or A-20, such requirements should be defined in the contract document.

Marking Of Angles

With the help of cutting plan/shop drawing all the dimensions shall be cranked. Marking of the location of holes shall be done manually according to the shop drawing. Center punch marks for the drilling shall be cranked. Material number and heat number shall be punched on each piece so that material can be traced after cutting. Flame cut holes or burn-enlarge holes shall not be acceptable.

Cutting of Angles

Cutting of angles shall be conducted by machine cutting, flame cutting or with the help of grinder surfaces shall be smooth uniform and free form tares, cracks and other discontinuities.

Drilling / Punching

Holes shall be drilled or punched. There should be no cracks around the holes and holes should be free from burrs.

Welding Of Fillet Joints (If Required)
Fillet welding shall be performed in accordance with the approved WPS. At the end of each pass for all weld types, visual inspection of the weld will be required. Hammering or penning of the welds is not allowed on the first and last passes.

Dimensional Inspection

Dimensions of a structural component shall be inspected. Actual dimensions of a structural component shall be recorded.

Identification Marks

The correct identification of each completed structural component shall be marked as per shop drawings.

Trail Assembly

After complete fabrication one face of tower shall be trail assembled. Dimensions shall be cranked with the help of shop drawing. Incase of any non-conformance the same shall be rectified before dispatching it for erection.