Field vs. Shop Installation

Installing trays in a vertical standing tower vs. horizontal

A common question is whether there are any advantages to installing trays in the field, versus having them installed in the shop.

Typical supporting arguments for installing trays in the shop:

• Packaged tray installation included with vessel fabrication saves on costs for field installation crew, crane costs, and costs for safety and rescue considerations
• Shop installation saves time in the field.
• Ease of modifications to tower attachments, if required, to ensure proper tray installation (this can be done in the field, too)

What are some concerns/challenges with installing trays in the shop?

• When installers are working against gravity, trays are often installed out of square or level. This may cause tray panels to have gaps between them, and cause tray manways to not fit properly.
• Hardware is often over-torqued to compensate for parts shifting during transport – this can deform the parts and affect their ability to form a proper seal. Over-torqued hardware is often not re-usable and expensive to replace.
• Downcomer panels are usually adjustable. Working against gravity in the horizontal position makes it much more difficult to set the height of the downcomer panel to design specifications.
• Temporary bracing installed that is forgotten to be removed on occasion impacting operation.
• Repairing or re-adjusting tray parts in the field can come with a considerable cost and outweigh the benefit of installing the trays in the shop

If installing in the shop, have K&D inspect the trays in the field and re-adjust to manufacturer’s specs!

Why install trays in the field?

• Ease of installation. Installers are working with gravity, rather than against it
• Better ergonomics reduces installation time
• Tray panels are easier to center, level, and square
• Reduced risk of over-torqued hardware
• Reduced risk of deforming or damaging tray panels
• Easier to set downcomer clearances and weir heights to design specifications
• No need for temporary bracing
• Ensures trays are installed according to manufacturer’s specifications, allowing the tower to perform at optimal efficiency

Tray manufacturers recommend that trays installed in the shop be fully inspected once the tower is erected on site to verify the integrity of the installation, and that nothing shifted during transport.

If you are investing in field services for a tower inspection, and the required safety support, then why risk a deficient installation that results in poor operation that reduces profit, or damaged parts that may need repair or replacement? It is money well spent having the tower internals installed correctly the first time in the field, avoiding the need to re-inspect and re-adjust incorrectly installed internals.

Hire a specialized tower field services contractor to install the trays correctly the first time, and eliminate the need for an additional inspection.