Weld Repairs Under Inert Conditions

Weld Repairs Under Inert Conditions

Incitec Pivot Phosphate notified us that they were having issues with their ISR Reactor and for us to prepare standby resources that could be mobilised at short notice till the scheduled shutdown in March 2014.

Incitec Pivot Phosphate
Queensland, Australia

The ISR Shift reactor is a unique design; consisting of a waste heat boiler twisted tube bank running through the Catalyst bed. The water travelling from the bottom inlet is turned to steam by the chemical reaction of the catalyst reacting with the process gas flow. This process is used to assist in the control of the chemical reaction temperature.

The tube bank had developed some leaks which was making it difficult to control the processes within the reactor.

At 7am on the 4th of July, the call came that the reactor could not continue and to implement the stand-by plan. The equipment had been shipped the week before as part of the plan and was already on site. Paul Circosta was stopped boarding a flight to Western Australia that morning to carry out a tank cleaning project, and tasked with getting the remainder of the crew of Craig Downing, Lea Waerea, Josh Dawson, Jeff Hardick, and Jamacia Mahara together and on its way as quickly as possible.

Due to the reactive nature of the catalyst, any testing and repairing of the tube bank had to be carried out from the Waste Heat Boiler drums at the top and bottom of the Reactor, under Inert Atmospheric conditions. This was made more difficult by the bottom drum not being sealed once its end cover had been removed to allow access, allowing the N2 purge to escape.

The repair process was to pressure test the tube bank from the shell side, detect the leaks in the respective drum, then plug and back weld. The decision was taken to seal the leaks in the bottom drum first.

The top (Steam) drum, whilst being easier to maintain the N2 purge, was a lot more difficult to gain access to.Once the top drum had been plugged and seal welded, the waste heat boiler was held under pressure overnight before declaring the repairs a success.

A difficult task was carried out without incident and made for an extremely appreciative client, who will be using our services during the March 2014 shutdown to unload the Reactor Catalyst and assist with a more permanent repair solution.

The full article can be found in Catalyst 18

[July 2013]