Three cost effective ways to strengthen trays against uplift
Several common operating conditions cause tray damage, including high liquid levels, free water flashing at the bottom of the column, and excessive pressure drop. The result can be an expensive shutdown causing lost production and profit. Increasing tray thickness can be a first approach for strengthening the tray, but this can increase the material cost of the trays by 50% or more. Sulzer commonly uses three simple cost effective alternatives to increase tray strength in new designs.
Alternative #1: Increase the Integral Truss Height and Width
Integral tray trusses, are formed from the tray panel and serve to support the tray decks by acting as minor beams. Maximizing the truss height and width significantly increases the strength of the tray decks while only slightly increasing the material cost of the trays. The tray trusses can interfere with the flow of the vapor/liquid mixture in the vapor space below the truss limiting capacity, so it’s important to properly orient deep trusses parallel to the froth flow to prevent this interference.
Alternative #2: Statically Fix the Truss Ends
As a standard design, integral trusses are typically unsupported at the truss ends. Fixing the ends of the trusses to a clip at the vessel shell or to another tray part will increase the mechanical load that the truss can handle. Sulzer typically utilizes a shear clip which bolts to the truss that is fixed to the vessel shell by welding. If welding to the shell is not allowed, there are alternate options such as welding to the underside of the support ring, as shown in the picture below.
Alternative #3: Strengthen Panel Connections
Although frictional connectors are used in many standard duty tray designs, upgrades in strength can be attained by using either Lip-SlotTM connections or through-bolted design. Lip-Slot tray connections use a mechanically integrated design to increase strength between panels and are used for light to heavy duty applications because of their strength and ease of installation. Through-bolted trusses with short (less than 6”) bolt spacings are extremely strong and reliable and are typically used for heavy and ultra-heavy duty designs.
Mechanical Integrity is Critical to Proper Tray Design
There are a variety of ways to safely and effectively strengthen trays to improve reliability in demanding applications. The key is to use the proper design to match the column operating requirements.
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