May-2024

Innovative vessel internals for enhanced safety when changing media beds (TiA)

In our previous article (PTQ Q1 2024), we discussed the challenges inherent in performing scheduled inspections within confined spaces of fixed-bed downflow reactors.

Kevin Chase
Johnson Screens

Article Summary

We noted that process safety managers are experts at maintaining compliance with rigorous OSHA and industry safety standards for entering ‘permit-required’ confined spaces. These safety teams are professionals who are expertly trained as to what is needed to mitigate the many significant worker safety hazards present during media bed replacements, including potential explosions, asphyxiation, continuous changes to the internal atmosphere, and much more.

Although planned maintenance is critical to keep a plant at peak productivity and operating dependably, shutting down profitable production for maintenance turnarounds is always disruptive and expensive. As a result, many process managers have been challenged by their companies to streamline and speed up the turnaround process and increase the efficiency of their teams to reduce costs.

In response, process engineers and safety managers are looking at ways to eliminate the need for workers to enter a reactor vessel for a simple media bed change. Since there are no shortcuts to maintaining worker safety and compliance with industry safety standards, the focus has shifted to analysing the maintenance process.

Eliminating manway entry
With fixed-bed reactors that utilise hold-down screens at the top of the bed, accessing the media requires the screen to first be removed from the vessel. Traditionally, this requires that a worker enter the confined space of the vessel to dismantle the manway in the centre of the screen, or for ‘floating’ screens, dismantle and remove the entire screen through the vessel manway. Senior process leaders have concluded that this initial stage can be eliminated and have started to mandate that workers will no longer be allowed to enter a vessel just to remove a screen or manway for simple media bed changes.

Johnson Screens was engaged to help address this issue by responding with the creation of two innovative hold-down screen solutions in a new StaySafe product platform. While both new products are hold-down screens with the same StaySafe ‘no-entry’ disassembly and removal concept, they have quite distinctive designs based on how they sit in a vessel.

The first new product is a ‘floating’ hold-down screen that rests directly on the top of the media bed. These screens sit on the media bed and must be removed from the vessel before media extraction and replacement can begin. Traditional designs of this type of screen are bolted together, and a worker must enter the vessel to disassemble the screen and remove it from the vessel.

This innovative design approach incorporates interlocking components assembled in the vessel without tools and secured in place with a central locking hub. This design allows for easy disassembly and removal of the screens from outside the vessel and eliminates the need for workers to enter the vessel to remove the screen. Working from outside the vessel simplifies compliance with regulatory safety protocols by eliminating the need for confined space entry permits in the initial stage of media bed replacement.

The second new StaySafe product is a ‘supported’ hold-down screen with a manway, which rests on support beams within the vessel. Although the screen follows a standard bolted design, the manway incorporates a unique design so it can be disengaged and removed from the screen from outside the vessel. An integrated manway screen seal ensures media containment with an easily released panel. This allows the turnaround team to remove the manway from the vessel or set it aside in the vessel while the media bed is replaced. The manway can then be reinstalled and locked back into position from outside the vessel.

Both new StaySafe products are already in use today and have been designed to the high-performance specifications and rigorous manufacturing standards that Johnson Screens has been delivering to the gas processing industry for decades.

StaySafe is a mark of Johnson Screens.

This short case study originally appeared in PTQ's Technology In Action Feature - Q2 2024 Issue

For more information: kevin.chase@johnsonscreens.com