In Control: How to Implement Distributed Control During a Plant Revamp
Go Ahead for the Project
After receipt of the management approval in April 2013, the process of indenting was initiated. A close monitoring process for timely indenting and delivery of field devices, erection hardware and DCS system was managed.
An extensive factory acceptance test (FAT) of the new DCS was carried out with active participation from the process and instrumentation side. All activities such as cable tray and junction box installation, cable laying, termination and loop testing were carried out simultaneously to expedite the work.
Only Small Space in the Control Room
There was space scarcity in the control room to accommodate four operator consoles because of the already placed operating consoles of the existing DCS through which
the hydrolyser unit was running and shut down was not possible in the running plant.
The extra margin in the length of the existingcables (communication, power and earth) helped us to lift and shift the old consoles at a closer distance in the ‘power on’ condition without interrupting the hydrolyser process operations and continued till the hydrolyser unit operation shifted from the old DCS to the new DCS system.
How to Keep Operations Running During Upgrade Processes
It was a challenging job to continue the hydrolyser unit operations parallelly from both the DCS systems while switching almost 250 inputs and 16 outputs (close loop) to the new DCS marshalling for operation/control. At first, the multi pair cables of monitoring parameters were shifted and established a new DCS system.
Sixteen closed loops were switched one by one taking the control valve operation through hand jack. It was also tuned and commissioned through the new DCS system.