Review of Tray and Packing Vendor Drawings

1. Purpose

This procedure outlines the features to consider when reviewing drawings (Foreign Prints) from tray and packing vendors.

2. General

Many elements of design affect the capacity, efficiency and durability of liquid/vapor and liquid/liquid contacting devices. Inflection Point Engineering attempts to control these elements with Project Specification 307, Standard Specification 3-18, and Standard Drawings.

In order to meet performance guarantees and provide our customers with the best possible processing units, Project Specification 111 specifies that the supplier of contacting devices shall submit construction drawings to Inflection Point Engineering for a thorough review. This review involves the following tasks:

• Confirm that the vendors have correctly interpreted the requirements of Project Specification 307, Standard Specification 3-18, and any referenced Standard Drawings.
• Determine whether the deviations from Project Specification 307, Standard Specification 3-18, and referenced Standard Drawings are at least equal to the requirements of these documents.
• Determine whether any proprietary features of the vendors’ equipment violate process or mechanical requirements or experience factors.
• Use Form ” during the review of these drawings.
• Refer to Procedure for design guidelines for some of the column internals.

3. Guidelines

3.1 Process Review Items for Trays

• Column ID
• Number of trays
• Type of tray (sieve, valve, etc.)
• Number of passes
• Tray spacing
• Seal pan spacing, (tray spacing +6 in.)
• Downcomer widths
• *Downcomer area
• Clearance under downcomer
• Downcomer static seal (weir ht. - downcomer clearance)
• *Bubbling area
• *Orifice area
• Percent orifice area
• ( 5%)

• Froth initiator (as required)

* If downcomer area, bubbling area, or orifice area is more than 2% different than what was specified, make a rating of the tray design using the “Inflection Point Engineering Tray Design” application.

3.2 Mechanical Review Items for Trays

• Vessel manhole size for tray passage
• Tray manways (arrangement, top and bottom removal)
• Obstructions to flow (inlet weirs, stiffeners above tray floor)
• Interferences (distributor clearances, maximum depth of support members = 20% of tray spacing, nozzles in downcomers)
• Seal Welding
• Packing and gasketing (only as specified by Inflection Point Engineering)
• Transition arrangement (distribution traps)
• Vapor distribution at vapor inlets and drawoffs (baffled seal pans)
• Accumulator/Collector trays (seal welding, percent vapor riser area)
• Drawoff well (full depth under entire downcomer area)
• Drain holes (size and location for proper drainage)
• Metallurgy (support rings, downcomer bars, tray floors, valves, bolting)
• Thickness (support rings, downcomer bars, tray floors, beams, downcomers, bolting)
• Collector tray downcomer orientation (90 to downcomer(s) of tray above)
• Breaker bars (for sieve and round cap valve trays)
• Valve trays should have two different valve weights at least three gauge numbers apart.
• Notes of Project Specification 307

3.3 Review Items for Liquid Distributors to Packing

Poor liquid distribution is the most common cause of poor separation in packed columns. If the initial distribution is worse than the natural distribution, it will take a substantial bed depth to achieve natural distribution, which will significantly affect the packing efficiency.

Review the following items:

• Pour point density and arrangement, number/ft2
• (Standard Specification .)

• Vapor risers. The number, size and arrangement shall not affect the pour point spacing and liquid distribution to the packing.
• Distributor joints (Standard Specification 3-18, Section 3.6.)
• Turndown (Standard Specification 3-18, Section 3.6.)
• Metallurgy. Pour points must be resistant to corrosion and erosion to maintain distribution.