Metric Equivalents for Vessels & Trays

1. Table of Contents

1. Table of Contents 1

2. Purpose 1

3. General 1

4. General Applications 1

4.1 Dual Dimensioning 1

4.2 Pipe, Nozzles and Manway Sizes 1

4.3 Typical Dimensions 2

5. Vessel Diameters 2

6. Vessel Dimensions Other Than Diameter 3

6.1 Vessel Length 3

6.2 Corrosion Allowance 3

6.3 Tray Dimensions 3

Attachment 1 – 301 Sample 4

Attachment 2 – 307 Item List 5

Attachment 3 – 307 Loading Page 6

2. Purpose

This procedure describes the Inflection Point Engineering dimensioning practice for vessels and trays for projects specified in metric units.

3. General

Generally, English units are used for process design calculations but frequently the customer requires the Schedule A to be specified in metric units.

The Vessel Section of the Basic Engineering Design Questionnaire (BEDQ) gives the customer the opportunity to provide dimensioning instructions to Inflection Point Engineering.

4. General Applications

Clearly identify English units when used (e.g., 18" OD).

4.1 Dual Dimensioning

Dual dimensioning is not a Inflection Point Engineering practice. However, if dual dimensioning is specifically required by the customer, list metric units as primary and English units as secondary contained in parenthesis (i.e., 300 mm (12 inches)).

4.2 Pipe, Nozzles and Manway Sizes

Use English units only without dual dimensioning for specifying pipe, nozzle and manway sizes. However, if the customer specifically requires metric dimensions for pipe and/or manways, use mm. Always specify holes and slots in pipes and distributors in mm regardless of the units chosen for the pipe sizes.

4.3 Typical Dimensions

Use mm for all dimensions with a note on each drawing and specification; i.e., "All dimensions are in mm unless specifically noted otherwise". Do not indicate the abbreviation as “mm” on drawings and/or specifications (e.g., specify 300; not 300 mm). The General Notes sheets of Project Specifications 301 and 307, and the Legend Note of the Piping & Instrument Diagram fulfill this requirement for most situations. Do not use centimeter or meter units.

For dimensions under one inch, round off to the closest mm except for 1/16 of an inch. Above one inch, round off to the closest 5 mm increment and for 12 inches and above, to the closest 10 mm. A few common equivalents are presented below:

* Use closer equivalents when dimensions are critical. Note that chordal dimensions in trayed columns are excluded from these rounding rules.

5. Vessel Diameters

Use the practices described below for specifying the diameters of vessels when metric dimensions are required. Continuous Catalyst Regenerator (CCR) units are excluded from these rules.

• Specify vessels with an inside diameter (ID) equal to or greater than 750 mm with an ID. Vessels requiring an ID greater than 750 mm are specified with an ID in 100 mm increments (e.g. 800 mm, 900 mm, etc.). Note that some companies use 200 mm increments for diameters above 2000 mm.

• In general, vessels with an ID less than 750 mm are expected to be made from standard wall pipe. Specify these vessels with a nominal pipe size (e.g. 20" OD or 12" nom).

• Do not specify 22" and 28" pipe sizes, as these are not normally available.

6. Vessel Dimensions Other Than Diameter

6.1 Vessel Length

Round up overall tangent lengths of vessels and vessel skirt heights to the next higher 100 mm increment.

6.2 Corrosion Allowance

Specify corrosion allowance in mm as indicated in Section 4.3.

6.3 Tray Dimensions

Apply the following guidelines to metric tray dimensions.

• Specify the tray spacing in 50 millimeter increments.

• For sieve trays, generally specify 13 mm for the hole size.

• Specify the downcomer clearances and weir heights in 5 millimeter increments.

• For any English tray report of these numbers, show the exact conversions of the metric numbers rounded to a reasonable number of decimal places. Report the diameter in feet rounded to two decimal places. Report tray spacing, weir height, downcomer clearance, chordal dimensions and hole diameters in inches rounded to two decimal places. The number of holes is the same regardless of whether it is a metric or English report. In general do not produce an English version of a tray summary report for a metric job.

Attachment 1 – 301 Sample

Attachment 2 – 307 Item List

Tray sections shall pass through a 24” ID vessel manway.

Attachment 3 – 307 Loading Page

Project