Cartridge tray installation failures
A study of the root causes for failed cartridge tray installations on-site, along with an alternative approach to mitigate the risk and optimise installation time
Urmilesh Tiwari Engineers India Limited
T he distillation or fractionation towers in petroleum refineries or petrochemical complexes are critical equipment due to their role in converting crude oil or feed into various usable petroleum products, employing mass transfer devices, such as trays and tower internals. This mass transfer equipment consists of trays and pack- ing (random and structured) along with associated inter- nals inside the column or tower, which are required for mass transfer operations, such as extraction, separation, distillation, and absorption. These trays and tower internals are installed inside the column through the provided manholes on tray support rings and bolting bars (TSRBB), which are welded to the column wall. The trays, packing, feed distributors, seal pans, and other column internals are all installed by the installation team entering the manholes. However, for small diameter trayed columns, manholes are not feasible. So, column body flanges are provided for the installation of these trays in the form of a bundle called ‘cartridge trays’. However, the installation of cartridge trays frequently fails on-site. This leads to increased costs and extended project timelines, as well as heightened health, safety and environmental (HSE) risks due to the major modification work required for the cartridge trays or col - umns, involving hot work at the site. Failed modifications sometimes result in material rejection and, in rare cases, a reorder as well. The following discussion
examines the root causes for failed cartridge tray installa - tions on-site, along with an alternative approach to mitigate the risk, optimise installation time, and enhance HSE, which ultimately contributes to successful project execution. Cartridge trays configuration, procurement, and installation philosophy For trayed columns with a diameter of less than 900 mm, a set of tray bundles comprising approximately 10 to 15 trays, connected or bolted by tie rods, is inserted through the column body flanges after the column is erected in a vertical position on-site. Sealing arrangements are provided to prevent the bypass of liquid or vapour through the gap between the trays and the column wall. There are two common types of sealing configurations: metallic sealing foil and gasket sealing. Both the column and cartridge trays are fabricated inde- pendently at their respective works and are shipped to the construction site separately. The column fabricator is responsible for the column, along with the body flange, while the cartridge trays are the responsibility of the tray manufacturer. Cartridge trays are inserted on-site using a crane through the column body flanges after the column is erected verti - cally. The cartridge tray procurement cycle, from initial con- cept, through design and engineering phases to installation on-site, is illustrated in Figure 1 .
YES
NO COMMENTS
Prepare mechanical design datasheet
PDS/HDS received for comments to tray designer
Providing comments by tray designer (if any)
START
Prepare and release of tray MR
Preparation and release of attachment drg. to column vendor
END
Installation
Fabrication of column by column vendor with input provided by tray designer
Erection of column at site
Supply at site by column vendor
Prepare and release PR
Corrective measures
Initiate installation
YES
Checking I.D. of column by tray vendor
Supply at site by tray vendor
Fabrication by tray vendor
Installation activities at hold
Column within tolerance range
NO
Problem area
Figure 1 Cartridge tray procurement cycle
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