Pressure Vessel Steel Tank Fabrication Welding General Steps

Below method covers the erection of the tank by joining the top and bottom portion through the welding procedure.

Prior to the commencement of the works the lifting supervisor must ensure that all site personnel are adequately briefed on the contents of safework method statement.

This safety briefing shall take the form of a short Toolbox Talk. Lifting supervisor must liaise with the site in charge about site circumstances, required material change and methods to be employed during the fabrication and welding operation.

Other contractors/ subcontractors working on the project shall be informed about the operations taking place. The client/main contractor shall provide proper scaffoldings for working at height.

Risk assessment document which identifies any hazards (environmental or other) that may be present within the works area, will be strictly implemented on project site.

Necessary Tools & Equipment

Below is list of mandatory tools and equipment for the tank fabrication and welding works.

• Welding Machine
• Spray Painting Gun
• Air Compressor
• Forklifts
• Over head crane
• Grid blasting machine
• Scaffolding

Pre Operation Requirements

The working area must be cleared for operations in a safe manner without endangering personnel, not directly involved in the tank fabrication/welding operation.

All operations obstructing the welding operation to be stopped temporarily.

The personnel not directly concerned with this operation must be kept out of the marked area. If necessary the working area should be secured against personnel entry.

Contents of this method statement to be briefed by the site Supervisor to all personnel concerned with this operation.

No action to be taken without the consent of the site supervisor.

Site supervisor should recheck the safety measures followed in different operations.

All required PPE including safety helmet, safety gloves, safety shoes, goggles (if necessary), Welding Mask, must be worn on entering the site.

Any special requirement must be notified and complied on prior basis.

Sequence of Work for Tank Fabrication

Both the tank portions which were already delivered to the site will be moved to the marked region with the help of overhead crane.

The tank must initially be placed one meter away from the wall for the convenience of welding.

The top portion of the tank will be place over the bottom with the help of overhead crane.

Once the top portion has been positioned, in order to align them for the proper fit up “C” Shaped brackets will be welded connecting both the portions.

Areas where both the portions are not aligning; a wedge will be used to hammer into the bracket to re align the distorted region.

The regions where both the portions get aligned are tack welded.

Once this procedure has been completed all around the tank, next step is to make the complete weld.

8mm Butt welding will be done both inside and outside of the tank. The welding at height will be carried out with the help of scaffoldings which are generally provided by the main contractor. Along with which the channel frames will also be welded to these regions.

Access panels which were pre-fabricated will be welded to the respective portions where the cut outs are already available.

The baffle plates will also be welded into the tank.

Once the welding procedure is finished, the welded region is subjected to NDT.

Magnetic particle testing is carried out to 100% on site welded regions.

On successful completion of the NDT the weld regions are thoroughly cleaned and spot blasting is carried out in the welded portions.

Once the blasting procedure is completed the site welded regions will be painted.

Then the steel tank will be put to final inspection as the fabrication work on the tank is over.

When the structure is finally approved, it will be put to leak test.

Once the tank passes the leak test, the structure is said to be fit for use.

Then the tank need to be shifted to the final area/wall, for which the tank will be supported/pushed through the overhead crane through D-shackles and forklifts.

Tank structure will then be bolted to the floor and to the wall.

As the tank has been pushed near to the wall, support from overhead crane is released. Forklifts are withdrawn.