BP_GS146-1_Column Internals.pdf

GS 146-1 COLUMN INTERNALS September 1995

Copyright © The British Petroleum Company p.l.c.

Copyright © The British Petroleum Company p.l.c. All rights reserved. The information contained in this document is subject to the terms and conditions of the agreement or contract under which the document was supplied to the recipient's organisation. None of the information contained in this document shall be disclosed outside the recipient's own organisation without the prior written permission of Manager, Standards, BP International Limited, unless the terms of such agreement or contract expressly allow.

BP GROUP RECOMMENDED PRACTICES AND SPECIFICATIONS FOR ENGINEERING

Issue Date Doc. No.

GS 146-1

September 1995

Latest Amendment Date

Document Title

COLUMN INTERNALS

(Replaces BP Engineering Standard 168)

APPLICABILITY

Regional Applicability:

International

SCOPE AND PURPOSE

This document covers general requirements for the design, fabrication, supply, testing and installation of trays, packings and other column internals.

AMENDMENTS Amd Date Page(s) Description _______________________ ___________________________________ _______________________ _______________________ _____________________ _________

CUSTODIAN (See Quarterly Status List for Contact)

Fluid Separation Issued by:-

Engineering Practices Group, BP International Internationa l Limited, Research & Engineering Centre Chertsey Road, Sunbury-on-Thames, Middlesex, TW16 7LN, UNITED KINGDOM Tel: +44 1932 76 4067

Fax: +44 1932 76 4077

Telex: 296041

CONTENTS

Section

Page

FOREWORD FOREWORD ................................ ................................................. .................................. .................................. .................................. ............................ ........... iii 1. INTRODU INTRODUCTIO CTION N ................................. .................................................. .................................. ................................... ................................ .............. 1

1.1 Scope 1 1.2 Applicat Application ion of this Specifi Specificat cation.... ion..................... .................................. .................................. .................................. .................... ... 1 1.3 Quality Quality Assuranc Assurance........................... e............................................ ................................... ................................... .................................. ................. 1 2. COLUMN COLUMN TRAYS........................ TRAYS......................................... .................................. .................................. .................................. ....................... ...... 1

2.1 General General Arrangemen Arrangementt and Size Require Requiremen ments............................. ts.............................................. .......................... ......... 1 2.2 Fraction Fractionator ator Tray Tray Design Design Details Details ................................. .................................................. .................................. ....................... ...... 2 2.3 Material Materialss and Thickn Thickness.................. ess................................... ................................... ................................... .................................. ................. 4 2.4 Structural Structural Details........................................ Details......................................................... .................................. .................................. ....................... ...... 5 2.5 Clampin Clamping g and Boltin Bolting g Arrang Arrangemen ements............................ ts............................................. .................................. ....................... ...... 7 2.6 Seal Seal Weldin Welding g .................................. ................................................... ................................... ................................... .................................. ................. 8 2.7 Manway Manwayss and Access Access................. .................................. .................................. .................................. .................................. ....................... ...... 8 2.8 Gasketting Gasketting ................................. .................................................. .................................. .................................. .................................. ....................... ...... 8 2.9 Drainag Drainagee ................................. .................................................. .................................. .................................. .................................. .......................... ......... 9 2.10 Toleran Tolerances ces for for Fabrica Fabricatio tion n and Assemb Assembly ly ................................ ................................................. .......................... ......... 9 2.11 Vortex Breakers Breakers ................................ ................................................. .................................. .................................. ........................... .......... 10 2.12 Blankin Blanking g on Sieve Sieve or Valv Valvee Trays Trays ................................... .................................................... ................................ ............... 11 2.13 Tray Installat Installation.......... ion........................... .................................. ................................... ................................... ................................ ............... 11 2.14 Reflux Reflux Inlets Inlets ................................ ................................................. ................................... ................................... ................................ ............... 11 2.15 Feed Inlets Inlets ................................. .................................................. .................................. .................................. .................................. ................... 12 3. PACKED PACKED COLUMNS....... COLUMNS........................ .................................. ................................... ................................... ................................ ............... 13

3.1 General General Arrangem Arrangement................. ent.................................. .................................. .................................. .................................. ..................... .... 13 3.2 Material Materialss and Thickness.................. Thickness................................... ................................... ................................... ................................ ............... 13 3.3 Structural Structural Detail Detail ................................ ................................................. .................................. ................................... .............................. ............ 14 3.4 Packing Packing............... ................................ .................................. .................................. .................................. .................................. ........................... .......... 14 3.5 Distribu Distributors tors - Gravity.............. Gravity............................... .................................. .................................. .................................. ........................ ....... 14 3.6 Distributo Distributors rs - Pressure Pressure ................................... .................................................... .................................. .................................. ................... 16 3.7 Ancill Ancillary ary Equipm Equipment ent ................................ ................................................. .................................. .................................. ........................ ....... 16 3.8 Tolerance Tolerancess ................................. .................................................. .................................. .................................. .................................. ..................... .... 17 4. ACCUMU ACCUMULAT LATOR OR TRAYS TRAYS ......... ............. ......... .......... ......... ......... .......... ......... ......... ......... ......... .......... ......... ......... ......... ......... ......... .... 17

4.1 General General Arrangem Arrangement................. ent.................................. .................................. .................................. .................................. ..................... .... 17 4.2 Manway Manwayss and Access Access................. .................................. .................................. .................................. .................................. ..................... .... 17 4.3 Structural Structural Requireme Requirements nts .................................. .................................................... ................................... ................................ ............... 18 4.4 Seal Seal Weldin Welding g .................................. ................................................... ................................... ................................... ................................ ............... 19

GS 146-1 Column Internals

PAGE i

5. VESSEL VESSEL FEATURES FEATURES ................................. .................................................. .................................. .................................. ........................ ....... 19

5.1 Internal Internal Pipes............................. Pipes.............................................. .................................. .................................. .................................. ..................... .... 19 6. DESIGN, DESIGN, DELIVERY DELIVERY AND INSTALLA INSTALLATION........................... TION............................................ ........................ ....... 20

6.1 Design Design calculat calculation ionss .................................. ................................................... .................................. .................................. ........................ ....... 20 6.2 Drawing Drawingss ................................... .................................................... .................................. .................................. .................................. ..................... .... 20 6.3 Finish Finishing ing,, Handli Handling ng and Storag Storage....................... e......................................... ................................... ................................ ............... 21 6.4 Testing Testing and Inspectio Inspection n before Installat Installation ion .................................. ................................................... ........................ ....... 22 6.5 Testing Testing and Inspection Inspection after Installatio Installation. n. ................................. .................................................. ........................... .......... 23 7. GUARANTE GUARANTEES............................. ES.............................................. .................................. .................................. .................................. ..................... .... 23

7.1 Mechan Mechanica icall ................................... .................................................... .................................. .................................. .................................. ................... 23 7.2 Process.......................... Process........................................... .................................. ................................... ................................... ................................ ............... 24 8. REGIONAL REGIONAL ANNEX ANNEX .................................. ................................................... .................................. .................................. ........................ ....... 24

8.1 USA USA

......... .............. ......... ......... .......... ......... ......... ......... ......... .......... ......... ......... .......... ......... ......... ......... ......... .......... ......... ......... ......... ......... ......... .... 24

APPENDI APPENDIX X A........................................... A............................................................ ................................... ................................... ................................ ............... 25

DEFINITIO DEFINITIONS NS AND ABBREVIATION ABBREVIATIONS S ................................ .................................................. .............................. ............ 25 APPENDIX APPENDIX B ................................ ................................................. .................................. .................................. .................................. ........................... .......... 26

LIST OF REFERENC REFERENCED ED DOCUMENTS................ DOCUMENTS................................. ................................... .............................. ............ 26


PAGE ii

FOREWORD Introduction to BP Group Recommended Practices and Specifications for Engineering

The Introductory Volume contains a series of documents that provide an introduction to the BP Group Recommended Practices and Specifications Specificati ons for Engineering (RPSEs). (RPSEs) . In particular, the 'General Foreword' sets out the philosophy of the RPSEs. Other documents in the Introductory Volume provide general guidance on using the RPSEs and background information to Engineering Engineering Standards in BP. There are also recommendations for specific definitions and requirements. Value of this Guidance for Specification

This document covers the major requirements of column internals appropriate to all BP Businesses. Adherence to the procedures will ensure that the equipment is fit for purpose whilst being cost effective Application

This Guidance for Specification is intended to guide the purchaser in the use or creation of a fit-for-purpose specification for enquiry or purchasing activity. Text in italics is Commentary. Commentary provides background information which supports the requirements of the Specification, and may discuss alternative options. This document may refer to certain local, national or international regulations but the responsibility to ensure compliance with legislation and any other statutory requirements lies with the user. The user should adapt adapt or supplement supplement this document to ensure ensure compliance for the specific application. Principal Changes from Previous Edition

This is a new BP Guidance for Specification which incorporates the substance of three previous standards standards listed below: below: BP (America) Refining Practice RP 7-2-2 (Fractionating Trays and Column Column Packing) - April 1992. BP Chemicals Engineering Standard ES/ENG/520/01 (Column Internals) - April 1987 BP Engineering Standard No 168 (Distillation, Absorption and Extraction Column Internals) April 1987.


iii PAGE iii

Specification Ready for Application

A Specification (BP Spec 146-1) is available which may be suitable for enquiry or purchasing without modification. It is derived from this BP Group Guidance Guidance for Specification Specificati on by retaining the technical body unaltered but omitting all commentary, omitting the data page and inserting a modified Foreword. Feedback and Further Information

Users are invited to feed back any comments and to detail experiences in the application of BP RPSE's, to assist in the process of their continuous improvement. For feedback and further information, please contact Standards Group, BP International or the Custodian. See Quarterly Status List for contacts.


PAGE iv

1.

INTRODUCTION 1.1

Scope

This Specification covers general requirements for the design, fabrication supply, testing and installation of trays, packings and other column internals. 1.2

Application of this Specification

This Specification shall be applied as the sole means of specifying column internals to a manufacturer, and forms a working document which shall be transmitted directly to manufacturers' without being rewritten as a project or contractor document. 1 .3

Quality Assurance Verification of the vendor's quality system is normally part of the pre-qualification procedure, and is therefore not specified in the core text of this specification. If this is not the case, clauses should be inserted to require the vendor to operate and be prepared to demonstrate the quality system to the purchaser. The quality system should ensure that t hat the technical and QA requirement s specified specif ied in the t he enquiry en quiry and purchase documents are applied to all materials, equipment and services provided p rovided by sub-contractors and to any free issue materials. Further suggestions may be found in the BP Group RPSEs Introductory Vol ume.

2.

COLUMN TRAYS 2.1

General Arrangement and Size Requirements

2 . 1 .1

For vessel of 840 mm (33") diameter and larger, tray panels, downcomer sections and other tray components shall be of sectional construction with sections removable through the vessel manways.

2.1.2

When a lifting beam is not available within the column, formed deck sections shall have a maximum component weight of 50 kg and a maximum length of 3000 mm (118"). A minimum number of plate sections shall be used in the floors of downcomers and accumulator trays.

2.1. 2.1.3 3

When a lifti fting bea beam m fac faciility ca can be be pr provided wit with hin a column, th the le length and weight restrictions shall be governed by the ability to install sectional components with the vessel in both the horizontal and vertical. The factors which govern the maximum weight/length are those necessary to ensure safe working in a confined space.


PAGE 1

2.1. 2.1.4 4

All tray ray components ents shal shalll be desig esign ned to permi rmit inst instal alllatio ation n and and removal from the top side. To design the internals to be installed from both sides is an expensive addition that should be avoid ed unless absolutel y necessary.

2.1. 2.1.5 5

For vessel sels smaller ler tha than 840 mm diamete meterr, car cartri tridge tra tray y assem ssemb blie lies shall be provided and the vessel shall be flanged to permit installation and withdrawal of the cartridge. Cartridge trays are invariably assembled in the fabrication shop.

2.2

Fractionator Tray Design Details

2.2. 2.2.1 1

Sieve tray deck eck hole size sizess should normal rmally ly be selec electted betw etween 4 mm and 12 mm (5/32 - 1/2") diameter. Larger hole sizes shall be used when the specification sheet specifies a fouling or corrosive service. The ratio of the hole pitch to hole diameter shall be a minimum of 2.0. Hole sizes larger than 25 mm (1") are more likely to weep, will restrict capacity and cause a lower efficiency. They are not normally used.

2 . 2 .2

Holes in in sieve trays sh shall be formed with the pu punch exit on the upperside of the tray. The manufacturer manufacture r shall ensure through fabrication and installation that this requirement is met for all deck sections. Burrs on the sieve tray holes which would cause injury to personnel, should be removed. removed.

2.2. 2.2.3 3

On si sieve eve an and val valv ve tra tray ys th the ho hole are areaa sh shall be un uniformly di distributed in in the contacting area approximating equilateral triangular pitch. Hole area per tray shall be within ±1% of the area specified.

2.2. 2.2.4 4

In th the cl closed sed po positi sitio on th the va valve lve sh shall all no not mak makee fu full perip eriph hera eral co contact act with the tray deck. Valve caps should be provided with an indentation which prevents such peripheral contact and thus helps to prevent the valve from sticking closed.

2 . 2 .5

Trays ha having more th than two passes sh should be de designed for eq equal bubbling bubbling area per pass rather than equal flow path length per pass subject to a minimum flowpath length of 450 mm (18"). In some multi pass designs this may cause problems with meeting minimum manway dimensions. In such cases this should be discussed discussed with the owner..

2 . 2 .6

Trays wi with three or or mo more pa passes sh shall be be pr provided wi with vapour an and liquid balance ducts.


PAGE 2

These are tubes or ducts that connect the different vapour flow areas such that pressures over the columns are equalised. The design should be discussed with BP.

2.2. 2.2.7 7

Trays sh shall be des desiigned to to han hand dle th the va vapour an and liq liqu uid loads ads gi given on the tray data data sheets. Standard sieve tray performance performance data data shall be specified on an FRI basis. It is recognised th at proprietary proprieta ry trays using sieve decks will be designed according to the manufacturer's own procedures and in this case the basis used for calculating jet flood, entrainment, maximum sustainable loading and downcomer backup shall be provided to the purchaser.

2 . 2 .8

Where the column is to be used offshore it may be subject to sway. In such cases the trays should be designed such that they operate satisfactorily within the sway tolerances approved by BP. In the absence of stated tolerances, a sway of ±0.5 degree may be assumed in addition to the conventional fabrication tolerances used although it will be necessary to consider motion in all six axes and, to some extent, the accelerations and periods of motion. It is the responsibility of the manufacturer to ensure that the hydraulic design meets these criteria.

2.2. 2.2.9 9

No sieve eve tray ray sha shall be desig signed for for more tha than 80% (FR (FRI basis asis)) of jet jet flood. Where sieve trays are used for vacuum service a maximum of 75% (FRI basis) of jet flood shall be used. No valve tray shall be designed for more than 85% of jet flood. Where valve trays are used for vacuum service a maximum of 77% of jet flood shall be used.

2.2. 2.2.10 10

Down Downco come merr clea clearr liqu liquid id back back-u -up p shal shalll be limi limite ted d to a max maxim imu um perc percen entt of tray spacing plus weir height as listed below: Downcomer Backup Criteria System Pr P ressure barg < 2.0 2.0 to < 5.5 5.5 to < 10 10 to 14 > 14 barg

2.2. 2.2.11 11

psig < 30 30 to < 80 80 to < 150 150 to 200 > 200

Maximum % Liquid Backup

60 55 50 45 40

Wher Wheree the the des desig ign n liq liquid uid load loadin ing g on a str strai aigh ghtt segm segmen enta tall ove overf rflo low w weir weir would be less than 0.9 litre/min. cm (0.6 USGPM/inch), 'picket fence' type overflow weirs shall be provided. The minimum horizontal distance between pickets shall be 50 mm (2"). The minimum vertical height of picket above the weir shall be 150 mm (6"). The effective weir rate at normal design flows shall be no less than 0.9 litre/min. cm (0.6 USGPM/inch). USGPM/inch).


PAGE 3

2.2. 2.2.12 12

If the the met meth hod of wei weirr atta attach chme men nt is such such that that gaps aps co could be lef leftt between the weir plate and the shell wall and/or between the weir plate and the tray weir edge, slide plates shall be provided to seal these gaps.

2.2. 2.2.13 13

For For slop sloped ed or step steppe ped d down owncome comers rs,, the the bott botto om downco wncome merr are areaa mu must not be less than 50% of the top downcomer area. In many cases the difference will be 20-40%.

2.2.14

Side downcomers shall be no less than 150 mm (6") in horizontal distances from the column shell. This distance to be measured at the centre line of the downcomer perpendicular to the inside face of the downcomer. Capsulated downcomers are exempted from this specification. specification. The spacing between interior downcomers on proprietary multi-pass trays is often small, but these are acceptable.

2.3

Materials and Thickness

2.3. 2.3.1 1

The mi minimu imum de desig sign th thickn ckness of of tr tray components sh shall be as as fo follow lows:-

Material

Thickness nearest mm

Material

Thickness nearest mm

gauge

Carbon steel Stainless steel Monel Copper

3 mm 2 mm 2 mm 2 mm

10 14 14 14

gauge

Aluminium Nickel Alloys Hastelloy Zirconium

2 mm 2 mm 1.5 mm 1.5 mm

14 14 16 16

2.3. 2.3.2 2

The th thick ickness ess of of pre press ssed ed allo alloy y st steel eel bu bubble caps aps an and th the ris riser er thickn ckness ess shall not be less than 1.5 mm (0.059") and 2.0 mm (0.079") respectively.

2.3. 2.3.3 3

The th thickn ckness ess of of pr proprieta ietary ry valv alve un units shall all be be set set by th the man manu ufactu acturrer based on process requirements requirements for the tray.

2.3. 2.3.4 4

More th than one we weigh ight of of pr propriet rietar ary y valv alves sha shall norma rmally lly be ac achieved by using thicker gauge material. The spot welding of a single weight on a standard valve is an alternative but in cases where severe corrosion is anticipated any weights shall be fully seal welded.

2.3. 2.3.5 5

In all all cases ases propriet rietar ary y valv alve units shal shalll be manu anufactu acture red d from rom corrosion resistant material for the intended duty and stainless steel is a minimum requirement. Carbon steel valve units should never be used.


PAGE 4

2.3. 2.3.6 6

Tray ring ings and downcom comer bolti lting bar barss sh shall be be in in the the sa same mat mater eriial as the vessel. Tray rings and downcomer bolting bars for clad or lined vessels shall be in the same material as the vessel cladding or lining, subject to thermal stress limitations.

2.3. 2.3.7 7

The dimen mensio sions of the tra tray support ring ings and and downcom comer boltin lting g bars ars shall be provided by the manufacturer. The following minimum and maximum dimensions shall be used:-

Column ID

Ring Width

mm

mm

less than 900 901-1800 1801 - 3500 3501 - 6000 above 6001

40 50 65 75 100

Minimum excluding thickness corrosion allowance Corrosion Other resistant material material mm ins. mm ins. 6 0.24 6 0.24 6 0.24 6 0.24 6 0.24 6 0.24 6 0.24 10 0.39 6 0.24 10 0.39

Maximum Thickness

mm 15 15 15 20 20

ins. 0.59 0.59 0.59 0.79 0.79

2.3. 2.3.8 8

Vessel ssel Corrosi rosio on allo llowance shall all apply to all surf surfac aces es of weld elded-o ed-on n items in contact with the process fluids.

2.3. 2.3.9 9

Vessel ssel Corrosi rosio on allo llowanc ance shall all apply to one side of all all rem removable able support beams. Vessel Corrosion Corrosion allowance allowance does not have have to be applied to replaceable/removable tray parts.

2.3. 2.3.10 10

For For tra tray ys of of cor corro rosi sio on res resis ista tant nt mate materi rial alss all all bolt boltin ing g sha shall ll be of of the the same same material as the removable internals with which it is connected .

2.3.11

Monel valve trays are prohibited.

2.4

Structural Details

2 . 4 .1

Loose be beams un unsupported by shell brackets are no not acceptable. In the context of deck support beams, a loose beam is defined as a completely separate member whose position posi tion is i s maintained only by tray to support ring rin g clamps and tray to beam clamps.

2.4. 2.4.2 2

Certai tain lar larger diam iameter ter columns will ill req require uire sup support ort beams eams that that are are distinct members separate from the stiffened tray sections. These


PAGE 5

separate beams, whether rolled joists or channels, shall be securely restrained against vertical and horizontal movement. 2 . 4 .3

At le least 36 360 mm (1 (14") cl clearance sh shall be be ma maintained be between th the bottom of the beams and the tray deck below when the main beams are located at right angles to the liquid flow direction on the tray below. This applies to both integral stiffeners and separate beams. Beams running parallel to the liquid flow on the tray below are not subject to the clearance requirement.

2.4. 2.4.4 4

The de desig sign lo load sh shall include th the we weight of of th the in inter ternal el eleme ement (w (with its corrosion allowance) plus the following uniform downward loads at design temperatures. (a) (a)

Frac Fracti tion onat atio ion n tray trays. s. The The grea greate terr of 1470 1470 N/m N/m2 (150 kg/m 2, 30 psi) or the weight of water 50 mm (2") over the highest weir setting.

(b) (b)

Area Areass unde underr down downco come mers rs.. The The grea greate terr of 2940 2940 N/m N/m2 (300 kg/m2, 61 psi) or a head of water one half the height of the downcomer.

(c) (c)

Drawraw-o off pans. ans. The great reater er of 6865 N/m2 (700 kg/m2, 143 psi) or a head of water to the top of the pan.

(d) (d)

Tota Totall draw draw-o -off ff tray trays. s. The The grea greate terr of 6865 6865 N/m N/m2 (700 kg/m2, 143 psi) or a head of water to the top of the vapour riser or the overflow weir.

(e) (e)

Baff Baffle le tray tray with with a weir weir.. The The gre great ater er of 6865 6865 N/m N/m2 (700 kg/m2, 143 psi) on the projected area or the weight of water 50 mm (2") over the weir height.

(f) (f)

Vacu Vacuum um resi residu duee stri stripp ppin ing g tra trays ys whe where re ste steam am str strip ippi ping ng is use used. d. 2 3 An upward force of 49 N/m (5 kg/m , 1.0 psi) shall be used.

Calculations shall exclude the corrosion allowance. 2.4. 2.4.5 5

Stiffen ffeneers or a retai etain ning devic evicee shall all be prov rovided on dow downcom ncomer erss to limit the horizontal movement of the bottom edge of the downcomer when the bottom section of the downcomer exceeds both 250 mm (10") in depth and 600 mm (24") in length.

2.4. 2.4.6 6

Stru tructu ctural ral sha shapes pes or clip clipss shal shalll be prov rovided alo along the botto ttom edg edge of the downcomer to ensure proper clearance between the bottom of the downcomer and the tray deck. The design and installation of these shapes or clips shall be such as to not interfere with the liquid flow


PAGE 6

exiting from under the downcomer. These clips may also be designed to satisfy 2.4.5. 2.4. 2.4.7 7

Adjust justaable wei weirs rs are not ac accep ceptable un unless ess sp specif ecifiicall cally y re required ired by th the project. The specification of adjustable weirs is now an uncommon practice due to the ease with which these can be incorrectly installed or otherwise maladjusted during operations. The levelness of the tray therefore depends on the levelness of the tray support ring and this requires an appropriate approp riate check.

2.4. 2.4.8 8

Tray ray sup support rin rings sh shall all be weld elded to the the wall all of the ve vessel ssel to prov rovide ide a flat support for for the assembled tray sections. sections. The upper surface surface of the tray support ring ring shall conform conform to the stated tray elevation. elevation. The ring shall be level to within the tolerances given in 2.10.4.

2 . 4 .9

When th the da data sh sheet sp specifies a corrosive or or vi vibrating se service no no notched corners shall be provided. All corners shall be formed using a 5 mm (0.2") radius minimum; minimum bend radii shall be three plate thickness.

2.5

Clamping and Bolting Arrangements

2.5. 2.5.1 1

Downcomers ers shal shalll be desig esign ned to ensur sure that no vapo apour by-pa -pass will ill occur. Where the downcomer downcomer is assembled in sections sections the top section section shall be bolted through at least two matching holes or horizontal slots in the bolting bar and the plate. One clamp or bolt hole shall occur as close to the end of each section as possible. Bolts or clamp pitch shall be a maximum maximum of 100 mm mm (4"). All bolt holes shall shall be sealed sealed by washers.

2.5. 2.5.2 2

Where ere carb carbo on stee steell deck ecks are are spec speciified fied,, the the non-thr -threa ead ded com components ents of clamping assemblies may be fabricated from carbon steel. Threaded components shall be compatible with the process requirements and the bolting bolting material material shall shall be AISI AISI 304 stainless stainless steel steel as a minimum minimum..

2.5. 2.5.3 3

Where ere th the de decks cks ar are sp specif cified ied in in st stainl inless ess st steel, el, th the cla clam mp ass asseemblies shall be fabricated from the same material.

2.5. 2.5.4 4

The maximu imum pitch between clamp amps shall be 180 mm (7") in the the tray ray active area and 100 mm (4") on the downcomer bolting bars and, where used, on the downcomer floor. Each separate tray and downcomer section shall have a clamp located as close to each corner as possible.

2.5. 2.5.5 5

The boltin ting for atta attach chin ing g major jor beam eams shal shalll be provided with ith double nuts or equivalent device.


PAGE 7

2 . 5 .6

Fasteners must not be welded to tray components.

2.6

Seal Welding

Where seal welding is required, for various tray sections please refer to Section 4.4. 2.7

Manways and Access

2.7. 2.7.1 1

Tray manways sh shall pr provide a minimum access op openi ening size of 380 mm x 600 mm (15" x 24").

2.7. 2.7.2 2

Tray manw anways ays shal shalll be rem removable from rom both abo above and and below low the the tray tray,, unless access is only from one side. The bolting shall be designed for positive closure orientation. orientation.

2.7. 2.7.3 3

Tray manways sh shall be be ve vertically aligned to all allow maximum working access. This clause is given in order to ease maintenance. The growing legalisation to stagger manways on alternate trays so that injury due to a fall is minimised may become an important issue in some projects. Advice must be sought in cases of dispute.

2 . 7 .4

A tray manway shall be provided on each liquid pass.

2.7. 2.7.5 5

Where ere prac ractic ticable able,, acce access ss throu rough an accu accum mulato ator tray ray sha shall be via one or more risers. The cap(s) cap(s) covering the riser(s) concerned concerned shall be detachable. Where a riser is used as a manway, its width shall not be less than 450 mm (18") in the longer direction and 380 mm (15") in the shorter direction. The top of such a riser shall have a welded brim bar to prevent prevent injury to personnel. The maximum maximum width shall be governed governed by the need to provide an adequate number of risers to ensure good vapour distribution.

2 . 7 .6

Minimum inter-tray work space shall be 300 mm (12").

2.8

Gasketting

2 . 8 .1

Gaskets shall not be used to seal the tray active area.

2 . 8 .2

Gaskets sh shall no not be be us used to to se seal ho horizontal do downcomer pl plates an and bolting bolting bar junctions junctions and any baffling baffling that may be used in the base of the column.

2 . 8 .3

Gasketted jo joints fo for to total dr draw-off tr trays ar are pe permitted.


PAGE 8

Where a stringent (Cat 1) leak test is required, gaskets may not be used as it is impossible to achieve a suitably leak tight tray.

2.8. 2.8.4 4

Gaske sket mat mater eria iall sh shall all no not co contain ain any any asb asbest estos and and sha shall be an an asb asbesto estoss substitute suitable for both the process fluid and steam, up to the vessel design temperature.

2.8. 2.8.5 5

The use use of pac pack king, ce cemen ments, ts, cau caulk lkin ing g, etc. etc. to ach achieve eve liq liqu uid or vap vapo our tightness or for any other purpose is prohibited.

2 . 8 .6

Tray spacing requirements shall be as follows:Tray location Above top tray

Feed tray Shell manhole

Spacing A mi minimum of of 1. 1.5 ti times th the no normal tr tray spacing Normal tray spacing plus 150 mm (6 in) whichever is the greater. Manhole internal diameter plus 150 mm (6 in) or the design tray spacing, whichever is greater.

The feed tray spacing should not be less than 600 mm (24").

2.9

Drainage

2.9. 2.9.1 1

Tray rays sh shall all ha have dr drain ain ho holes only wh where ere it items ems, e. e.g. bu bubble caps, gi giving a positive seal are used. used.

2 . 9 .2

All seal pans and sumps shall have drain holes. Holes, where appropriate, shall be located in the pan floor closest to the column centre where appropriate to avoid vapour ingress into the downcomer liquid.

2 . 9 .3

For weir loads exceeding 1.2 m 3/h.m3 (.5 USGPM/ft2) the drain hole area should be based on 0.1% of of the area to be drained. drained. For lower weir loads the basis should be 0.01%. Hole diameter should be between 513 mm (0.2" - 0.5"), limited to a maximum of 2 holes per section.

2.9. 2.9.4 4

Drain ain holes les shal shalll not be prov rovide ided on tray rays or pans ans having ing a nozzle zle positioned so as to allow allow complete drainage.

2.10

Tolerances for Fabrication and Assembly

2.10 2.10.1 .1

The mea mean n ou outlet let wei weirr he heigh ight sh shall all be be set set withi thin ±2 ±2.5 mm mm (0 (0.1") of th the specified value. The difference difference between the maximum and minimum minimum height dimensions shall not exceed 3.0 mm (0.12").


PAGE 9

2.10 2.10.2 .2

When in inlet weirs irs ar are use used d, th the he heigh ight to tolera erance shal shalll be be ± 3.0 mm mm (0.12").

2.10 2.10.3 .3

The un under-d er-do owncomer clea learan rance shal shalll be be set set with ithin + 3. 3.0 mm mm (0 (0.12") or - 0.0 mm of the specified value.

2.10 2.10.4 .4

Tray Tray leve leveln lnes esss and and tray tray supp suppor ortt leve leveln lnes esss bet betw ween een high high and and low low poin points ts on the vessel circumference shall be:Column diameter mm ins. < 1000 41 1000 to < 1800 71 1800 to < 3500 138 +3500 138

2.10 2.10.5 .5

Maximum out of level mm ins. 3 0.12 4 0.16 5 0.20 6 0.24

The The loca locati tio on of tray tray supp suppor ortt ring ringss shal shalll be set set with within in the the foll follow owin ing g specified distances:(a)

± 6 mm mm (0. (0.24 24") ") from from the the ref refer eren ence ce plan planee wit with h the the maxi maximu mum m high to low difference not exceeding 6 mm (0.24").

(b) (b)

± 3 mm mm (0.1 (0.12" 2")) top top of of supp suppor ortt to top top of of adja adjace cent nt sup suppo port rt..

2.10 2.10.6 .6

The The max maxim imum um unco uncov vered ered join jointt open openin ing g betw betwee een n tray tray sect sectio ion ns sha shall ll be 5 mm (0.2") in the shorter direction and 25 mm (1") in the longer direction. The sum total total of the areas of of uncovered joint openings openings on any one tray shall not exceed 1% of the active hole area on that tray.

2.10 2.10.7 .7

The min miniimum ov overla rlap be betwee tween n the the su support ring ing and and the the ou outsid tsidee diameter of trays, pans and similar items shall be 20 mm (0.8").

2.11

Vortex Breakers

2.11 2.11.1 .1

Vort Vortex ex brea breake kers rs shal shalll be be fitt fitted ed in all all ves vesse sels ls at nozz nozzle less lea leadi ding ng to pump pump suctions. They are also required required at all other other pipe outlets outlets where swirl may interfere with the separating of phases, e.g. in the separation of water in oil-water separators. Vortex breakers may be of the cross type or grating type. The choice is usually made according to the space available.

2.11 2.11.2 .2

Vort Vortex ex brea breake kers rs shal shalll be be fit fitte ted d to to all all inte intern rnal al pipe pipess dis disch char argi ging ng liqu liquid id from accumulator trays.


PAGE 10

2.12

Blanking on Sieve or Valve Trays

2.12 2.12.1 .1

Blan lanking ing of of act activ ivee ho holes les sh shall all be be ach achie iev ved usin using g fla flatt pla plate te blan blank king ing strips bolted to the tray. Blanking strips shall be distributed uniformly in the active area and should be between 40 mm (1.6") to 100 mm (4") wide, so as to completely cover holes.

2.12 2.12.2 .2

Blan Blank king ing str strip ipss sha shall ll be inst instal alle led d at at rig righ ht-an t-angl gles es to liq liquid uid flo flow, w, cove coveri ring ng complete rows if practicable.

2.12 2.12.3 .3

For tr trays ays us using ing cir circu cullar valve lves, valv alves sh shall all be be re removed pri prio or to to blanking blanking..

2.12 2.12.4 .4

Blan Blank king ing sha shall ll not be used used to adju adjust st inst instal alle led d ho hole area area to the the spe speci cifi fied ed design value.

2.13

Tray Installation

2.13 2.13.1 .1

The manu manufa fact ctur urer er shal shalll sup suppl ply y an inst instal alla lati tion on proce rocedu dure re for for eac each h typ typee of of tray to be supplied to include tolerances for installation and cross referenced with drawings.

2.13 2.13.2 .2

When When tray tray inst instal alla lati tio on take takess plac placee with with the the vesse essell in the the hori horizo zont ntal al position, position, the manufacturer manufacturer shall supply an installation installation procedure which takes account of the vessel diameter and the out of roundness of the vessel in the horizontal. All sections of the trays including tray manways shall be fitted when traying takes place in the horizontal.

2.13 2.13.3 .3

The manuf anufac actu ture rerr sha shall ll supp supply ly the the fol follo lowi wing ng extr extraa mat mater eria iall to to allo allow w for for field losses during installation:(a )

Bolt, nuts and washers

10%

(b)

Tray clamps

3%

(c )

Gasketting material

20%

Operational spares are not required. 2.14

Reflux Inlets

2.14 2.14.1 .1

Refl Reflux uxes es shal shalll en enter ter an an in inacti active ve tray tray area area behi behin nd an an in inlet let wei weirr or or fal false se downcomer acting as a seal dam. The inlet pipe shall be either an open ended 'T' or a slotted branch distributor. The choice will depend on the need to maintain a certain minimum exit velocity.


PAGE 11

2.14 2.14.2 .2

The sea seall da dam hei heig ght sh shall all be be 50 50 mm mm (2 (2") gr greate eaterr th than the in inlet pipe ipe nominal diameter up to a maximum dam height of 200 mm (8").

2.14 2.14.3 .3

Bran Branch ch pip pipe vel veloc ocit itie iess sh shall all be be a maxi maximu mum m of of 1 m/s m/s (3. (3.3 3 ft/ ft/se sec) c) and and slot slot velocities a maximum of 2 m/s (6.6 ft/sec).

2.15

Feed Inlets

2.15 2.15.1 .1

Liquid feed eeds sh shall all en enter throu rough an an op open end ended bra bran nch to dis disch char arg ge vertically downward into the downcomer of the tray above the desired feed location or via a slotted branch distributor discharging onto the active side of the downcomer at the desired feed tray level. It is recognised that a number of variatio ns in design may b e used. These should be carefully reviewed.

A distributor shall be used when flashing of liquid in the downcomer could result in premature flooding. 2.15 2.15.2 .2

Two Two phas phase, e, vapo vapour ur-l -liq iqui uid, d, feed feedss shal shalll ente enterr the the tray tray zone zone via via a slot slotte ted d branch distributor distributor which discharges against a wear plate attached to the downcomer bolting bars.

2.15 2.15.3 .3

Wear ear pla plate te thic thick kness ess sh shall all be be a minim inimu um 5 mm (0.2 (0.2") ");; spa space cers rs shal shalll be provided to hold the wear plate off the downcomer.

2.15 2.15.4 .4

Vapou apourr inle inlets ts shal shalll norm ormally ally be a plain lain open pen inle inlett nozzle zzle.. The The inle inlett nozzle shall be oriented approximately at right angles to the flow of liquid on the tray above.

2.15 2.15.5 .5

For For liqu liquid id feed feed pipes ipes whic which h cros crosss the the tray tray acti active ve area area the the mini minimu mum m clearance from the bottom of the pipe to the tray below shall be 350 mm (14").

2.15 2.15.6 .6

Hig High vel veloc ocit ity y (i. (i.e. e. appr approa oach chin ing g so sonic nic vel velo ocity city)) vap vapou ourr in inlet let lin lines es shal shalll be designed to dissipate the energy. The inlet pipe shall be sized to limit the fluid velocity to a maximum of 70% sonic velocity. A minimum straight run of 2 m shall be provided to the column entry and the feed shall enter the tower tangentially. A hood shall be provided extending at least to one quarter of the column circumference from the column inlet point.

2.15 2.15.7 .7

For high igh vel velo ocity city inle inlets ts the the min minim imu um dis dista tan nce from from the the top top of the the in inlet let pipe to the seal pan of the tray above shall be the greater of one pipe diameter or 500 mm (20"). The minimum distance from the bottom of the inlet pipe to the surface of any liquid below shall be the greater of two pipe diameters or 600 mm (24").


PAGE 12

3.

PACKED COLUMNS 3.1

General Arrangement

3 . 1 .1

All no non ra random pa packing el elements, su support gr grids or or st structures, an and distributor systems and hold down grids shall be of sectional construction with sections removable through the column manways. Column manways shall be provided at the distributor system.

3.1.2

When a lifting beam is not available within the column any component section referred to in 3.1.1 shall have a maximum weight of 50 kg (110 lb.) and a maximum length of 3000 mm (118"). All other components, excluding structural beams, shall have a maximum weight of 120 kg (265 lb.) and a maximum length of 4000 mm (157"). When a lifting beam facility can be provided within a column the weight and length restrictions shall be governed by the ability to install sectional components with the vessel in the vertical. The factors which govern the maximum weight/length are those necessary to ensure safe working in a confined space.

3.1. 3.1.3 3

Gravi avity distr istrib ibu utors tors shall be pr provide ided as as st stand andard ard. Jus Justifi tifica cati tio on sh shall all be be provided provided for any alternative alternative offered. The quality of the liquid distribution is the key factor to good packing performance. More even liquid distribution can be achieved with wit h gravity distributors. Particular emphasis is necessary in distillation duties where efficiency is important.

3.2

Materials and Thickness

3 . 2 .1

The st standard ma material fo for al all it items re referred to to in in 3. 3.1.1 an and ra random packing packing elements shall shall be stainless steel. steel. The specific specific grade of stainless stainless steel or alternative material shall be suitable for the process fluid. Carbon steel may be suitable for the process fluids and carbon steel will not rust less than stainless steel. Carbon steel is not recommended because of the maintenance requirements. It is very difficult to prevent surface rust by excluding air/water in a maintenance condition when column man entry is necessary.

3.2. 3.2.2 2

The thi thickness ess of packing shall be spec speciified so that the maxim aximu um distortion of packing elements at the bottom of the tallest packed height shall be no more than 2% of the corresponding standard dimension. Distortion under compression will effect both the efficiency and the hydraulic capacity of a packing. The thickness of packings shall be determined by the manufacturer and shall conform to his current practice. This will depend on the grade, and therefore


PAGE 13

rigidity, of the packing grade used. It is frequently 0.15 mm (0.006") but may with some packing be as low as 0.1 mm (0.004") thick.

3.3

Structural Detail

The design load shall include the weight of the packing elements plus the weight of the process fluid when the section is operating in the fully flooded regime. The minimum process fluid at flood shall be taken as equivalent to 10% of the packing volume. 3.4

Packing

3.4. 3.4.1 1

The su supply of of ran rand dom pa packi cking sh shall be be mad madee on only on on th the ba basis sis of of fi filli lling a given column diameter to a given depth. The manufacturer shall be responsible for the supply of sufficient packing to take account of any settlement allowance or dimensional variations. Column sections are often non-circular and the packing elements per unit volume quoted by manufacturers manufacturers are averages. The supply of additional packing at the outset is more cost effective than the remedial work necessary to meet the specified height. Packing performance is almost always expressed in terms of packed height.

3.4. 3.4.2 2

The depth epth of packin cking g for for each ach bed shal shalll be stat stated ed by the manu anufact factu urer rer to provide the number of mass transfer stages required and to prevent physical physical distortion distortion of the packing packing in in service.

3.4. 3.4.3 3

The manu anufact factu urer rer of stru struccture tured d pack acking sha shall ensu ensure re that that perip riphera eral sealing is provided at each layer to minimise vapour by-pass due to column ovality, manufacturing tolerances, etc. Peripheral sealing should be provided at each layer around the complete circumference. The sealing medium should be in contact with both the column wall and the packing. Visual inspection at installation will be required to check this.

3.5

Distributors - Gravity

3.5. 3.5.1 1

The liq liquid dist istrib ributio tion to the top of the packe cked bed shall all be unifo iform over the vessel cross section for the whole design operating range. This uniformity of flow shall be maintained as the liquid impinges on to the top of the packed bed.

3.5. 3.5.2 2

The outerm ermost liqu iquid distri strib butio tion point ints shal shalll be place aced as clo close as practicable practicable to the vessel wall and the following following maximum maximum dimensions dimensions shall be used.

Random packing nominal size mm ins.

Structured packing surface area 2 m /m3 ft2/ft3


Maximum distance from vessel wall mm ins.

PAGE 14

< or = 26 < or = 1.0 27 to 61 1.0 to 2.4 > 61 > 2.4

> 261 121 to 260 < or = 120 Grid type

> 80 37 to 79 < or + 37

20 30 40 Use manufacturers limit

The area irrigated by the distributor shall be a minimum of 95% of the tower cross sectional area, as defined by a circle linking the outermost distribution points. Particular attention shall be given to ensure that flow from the outermost orifices is not blocked by the presence of any other piece of equipment in the column. 3 . 5 .3

Distributors shall be provided with means of levelling.

3.5. 3.5.4 4

The desig esign n of th the gr gravit avity y dist istrib ributor an and any any asso ssociat ciated ed parti artin ng boxes shall allow them to be levelled to within the tolerances specified in 3.8.

3.5. 3.5.5 5

Liqu iquid supply to the the parti artin ng box sha shall be so arran rrang ged that that aera aerattion ion of the liquid in the box and liquid swirl shall be minimised.

3.5. 3.5.6 6

Distrib ributor des desiign sh shall be su subject to a minimum ori oriffice diam iameter which will be a function of the process fluid characteristics. This minimum diameter shall not be less than 2 mm (0.08"). Despite best efforts to filter all liquid streams entering packed columns, industrial fluids are not sufficiently clean to operate for f or prolonged period s with orifices below 2 mm (0.08") diameter. In many cases this chosen orifice diameter will be greater than this minimum and must always be considered at the design stage, bearing in mind the nature of the fluid being distributed and the process environment.

3.5. 3.5.7 7

All or orifi ifices ces sh shall be fo formed wi with th the pu punch exit on on th the li liquid outlet sid side of the distributor. Small irregularities during manufacture are to be minimised near orifices so as to minimise differences in exit flow rates. Where orifices are laser cut this clause need not apply. Drilled holes should not be used other than in tube distributors.

3.5. 3.5.8 8

The ma manufact factu urer shal shalll pr provide ide wi within th the dis distr trib ibu ution ion sy syste stem a mean eans to minimise particulate fouling of the distributor and define the method of cleaning such systems. Even in the cleanest process duties periodic cleaning will be a requirement. External filters on all liquid feed lines should always be provided and located as close as is practicable to the feed point. The filters will extend the period between cleaning.

3 . 5 .9

Covers sh shall be be pr provided on on al all fi final di distributor ch channels.


PAGE 15

0.8 1.2 1.6

3.5. 3.5.10 10

A mi minimum li liquid de depth of of 30 30 mm sh shall all be be us used in partin rting g bo box or or distributor channels. A minimum depth is necessary to minimise variations in head along the length of the channels.

3.6

Distributors - Pressure

3.6. 3.6.1 1

Spray ray nozzle zzle dist istrib ributor tors shal shalll be desig esign ned so that the the theo theorretic eticaal coverage ratio is a minimum of 3 where the coverage ratio is defined as the ratio of the total geometrical spray footprint area to the column area. Nozzles shall be arranged so that that there are no unirrigated areas. Circular full cone spray nozzles shall be used. The exact locations of nozzles to achieve the most uniform coverage is a function of the characteristic of the particular nozzle selected. This is an area which should be discussed with the owner.

3.6. 3.6.2 2

Where ere lad ladder typ type distri strib butors tors are are sele select cteed, and and where ere plain lain holes les are are used, all internal burrs shall be removed which would otherwise affect the liquid flowrate. Any pipe system shall have a vent hole to prevent accumulation of vapour.

3.6. 3.6.3 3

Feed eed pipewo ework to the the distri strib butor shall all be sized ized to lim limit the maximu imum velocity to 1.5 m/s (4.9 ft/sec).

3.6. 3.6.4 4

For fo fouling ing se servic rvices es the mi minimum fre freee pa passag ssagee th throu rough th the sp spray nozzle zzle shall be equivalent to a diameter of 3 mm (0.12"). In many cases larger free passages will be required.

3.6. 3.6.5 5

Extern ernal fil filter ters shal shalll be provide ided to prev revent ent passa assag ge of mate ateria rial that that might otherwise block the nozzle. The mesh size should be one third of the nozzle free passage diameter.

3.7

Ancillary Equipment

3.7. 3.7.1 1

All pack acked beds shall be provide ided with ith a bed lim limiter, er, the desi esign of which will be a function of the particular packing and distributor type being used. In all cases the bed limiter design shall be such as to offer the minimum possible coverage of the packing below. In this context angle sections are not acceptable. Where structured packing is used, any bars constituting the bed limiter shall be orientated so that they do not lie along joins between adjacent blocks of packing. packing.


PAGE 16

3.7. 3.7.2 2

Support grid rids sha shall be such as to imp impose the the minimu imum resi esista stance to vapour flow.

3.8

Tolerances

The elevation difference between low and high points in the gravity liquid distributor shall not exceed 2 mm (0.08"). 4.

ACCUMULATOR TRAYS 4.1

General Arrangement

4.1. 4.1.1 1

Accum cumulat lator tray tray rise risers rs sha shall be unifo iforml rmly spa spaced ced over the the tray ray. The total riser area shall be consistent with the requirements of the column duty. Thus in vacuum operation and operations where minimum pressure drop normally is required, a maximum riser area is to be used consistent with the restraints imposed by mechanical considerations.

4.1. 4.1.2 2

Accum cumulato ator tra tray ys use used d for for al all vac vacu uum columns and and/or /or wh where ere al all liq liqu uid leakage has to be avoided, shall incorporate the following features:(a )

chimney caps ve vee sh shaped.

(b) (b)

vapo vapour ur emer emerge genc ncee area area at at the the pou pouri ring ng end, end, or end ends, s, of of the the cap cap shall be fully blanked.

(c)

risers risers orient oriented ed to be paral parallel lel to the genera generall flo flow w of of liqu liquid id acros acrosss the tray.

These requirements are made to minimise the possibility of liquid re-entrainment and to minimise liquid residence time, a factor particularly required in high temperature vacuum service.

4.1. 4.1.3 3

Accu ccumulat lator tr tray cap caps sh shall be orie riented ted so tha that li liquid pourin ring fro from one cap shall not enter the vapour emergence area of an adjacent cap.

4.2

Manways and Access

4.2. 4.2.1 1

Where ere prac ractic ticable able,, acce access ss throu rough an accu accum mulato ator tray ray sha shall be via one or more risers. The cap(s) cap(s) covering the riser(s) concerned concerned shall be detachable. Where a riser is used as a manway, its width shall not be less than 450 mm (18") in the longer direction and 380 mm (15") in the shorter direction. The top of such a riser shall have a welded brim bar to prevent injury injury to personnel. personnel.


PAGE 17

The maximum riser width should be governed by the need to provide an adequate number of risers to ensure good vapour distribution.

4 . 2 .2

Where th the he height of of a riser us used as as a manway ex exceeds 45 450 mm mm (1 (18") an an internal rung ladder shall be provided as necessary, with strengthening of the riser.

4.3

Structural Requirements

4.3. 4.3.1 1

Majo ajor beam eams shal shalll be att attach ached by boltin ting to verti ertica call brack racket etss or foo foot step brackets, welded to the vessel shell. shell. Bolt holes in brackets or beams shall be slotted to allow for thermal expansion expansion of the beam. Methods of restraint which rely on indirect fastenings are not acceptable. Other methods of restraint may be used providing that both horizontal and vertical movement of the beam is limited to that strictly required to contain the effects of thermal expansion.

4.3. 4.3.2 2

The defl eflecti ectio on of asse assem mbled led deck eck sect sectio ion ns at operat eratin ing g tem temperat eratu ure shall not exceed a value of 1/900 of the column diameter. Where a corrosion allowance is used, the calculations for deflection shall be made on the corroded thickness.

4.3. 4.3.3 3

All elements shall be des desig ign ned for for a concen centrat trated ed main ainten tenance load of 150 kg (330 lb.) at any point on the installed assembly, based on the allowable stress at 40°C (104°F). Calculations shall exclude the corrosion allowance.

4.3. 4.3.4 4

The de desig sign lo load sh shall include th the we weight of of th the in inter ternal el eleme ement (w (with its corrosion allowance) plus the following uniform downward loads at design temperatures. The greater of 6865 N/m 2 (700 kg/m 2, 143 psi) or a head of water to the top of the vapour riser or the overflow overflow weir. Calculations shall shall exclude the corrosion allowance.

4.3. 4.3.5 5

Allow lowable stre stress ssees for metal tals shall all be as per the the vesse ssel cod code used sed for for the column design and construction, such as for example ASME Code or BS 5500.

4 . 3 .6

The di distance be between th the up upper ed edge of of an an ac accumulator tr tray ri riser ca cap and the underside of the tray above or packing support above, shall not be less than 300 mm (12"). When the riser is used as a manway manway the minimum distance shall be 450 mm (18").

4.3. 4.3.7 7

The manu anufact factu urer rer shal shalll ensu ensure re that that the the tru trusses sses abo above the the rise riserr cap caps of accumulator trays do not obstruct the flow of vapour from the risers.


PAGE 18

Such structural members shall be oriented so that they are parallel to, and whenever possible immediately above, the riser caps. 4.4

Seal Welding

4.4.1

All joints in seal pans and discharge pans shall be fully seal welded. The minimum design thickness of seal pans and discharge pan components shall be 3 mm (0.12"). Trays designated as total draw-off trays shall be designed to have all seams continuously welded, including seams in risers and the peripheral seal with the tray support ring. Accumulator trays with clamps and bolting have often failed in service. The presence of gasketting has often made failure more likely. Fully welded construction has proved to be the solution to minimising failures. Long experience has shown that provided the tray is designed for full seal welding, damage due to thermal stresses will not occur even though there may be some minor localised panel buckli ng.

5.

4.4.2

Seal welding shall normally be using a continuous fillet weld above the attachment and an intermittent weld below. Where the duty is specified as corrosive, continuous fillet welds should be used above and below.

4.4.3

Welding operators and procedures shall be qualified in accordance with the vessel code used for the column construction, construction, such as Section IX of the ASME Boiler and Pressure Vessel Code or Code or BS 4870/4871.

4.4.4

All welding shall conform to BS 5500 or 5500 or ASME Section VIII.

4.4.5

Accumulator trays shall be designed to be fully seal welded, including the periphery. The peripheral support shall normally utilise a conventional tray support ring welded to the vessel wall and not to any cladding which may be present.

VESSEL FEATURES 5.1

Internal Pipes

5.1.1

Internal distribution pipes shall have flanged and gasketted gaskett ed connections connect ions to facilitate installation and removal.

5.1.2

Internal piping shall be the same nominal alloy as the inside surface of the vessel. For ferric, austenitic or high alloys, such as Inconels, the minimum wall thickness shall be schedule 10 or 3/16th inch (4.7mm), whichever is less. For carbon steel or low chrome steels, the minimum wall thickness shall be schedule 80.


PAGE 19

6.

5.1.3

Internal flanges shall be ASME/ANS ASME/ANSII Class 150 weld neck or slip-on type unless otherwise approved. Internal flanges shall be of a compatible metallurgy with the material specified for the internal pipe. Internal flange bolting shall be sequentially tightened, and double nuts used to prevent loosening.

5.1.4

When an internal distributor distributo r or sparger is of the 'bayonet' type, the external flange shall be marked in such a manner that the position of the slots or holes will be known from the outside of the vessel.

DESIGN, DELIVERY AND INSTALLATION 6.1

Design calculations calculations

The results of the rating calculations and related mechanical data shall be summarised summarised on the data sheets. The information shall be furnished furnished to the owner's engineer for their review prior to commencement of fabrication. 6.2

Drawings

6.2.1

The following dimensions shall be referenced referenc ed to the tray floor and be consistent with the process and mechanical data sheets:-

6.2.2

(a)

Weir heights

(b)

Clearance under the downcomers

(c)

Splash baffles

Plan and elevation drawings shall be provided by the manufacturer for approval by the purchaser before fabrication commences, indicating materials specifications and all design and assembly dimensions. These drawings should contain the following minimum design information, where applicable, relating to every separate design section of the tower. (a)

clearance under the downcomer.

(b)

inlet and outlet downcomer area.

(c)

effective exit weir length.

(d)

exit weir height.

(e)

sieve hole diameter.

(f)

valve type (reference number).


PAGE 20

(g)

valve thickness.

(h) (h)

actu actual al numb number er of siev sievee ho holes les on on val valve ves. s.

(i)

normal tray spacing.

(j)

corr correc ectt boltin lting g torq torqu ue req requirem iremen ents ts..

(k) (k)

lev level to toler lerance ancess (d (distri strib butors tors)).

(l) (l)

flui fluid d dens densit itie iess at oper operat atin ing g con conditi dition ons. s.

(m)

maxi maximu mum m and and mini minimu mum m desig design n liqui liquid d flowrates flowrates (distributo (distributors). rs).

(n) (n)

elev elevat atio ion n and and orie orient ntat atio ion n (in (in diag diagra ram) m) of the the tra tray. y.

Note:- the above measurements shall apply to actual sizes as used for process design, and not to measurements that might be used for fabrication purposes. 6.2. 6.2.3 3

One orig riginal inal tran transsparen arency cy and and two two cop copies of each each Final inal Fabri abrica cattion ion drawing shall be supplied to the Owner.

6.2. 6.2.4 4

The or orien ientati tatio on in degre egreees, and the ele elev vatio ation n, sha shall be ma marke rked on all all drawings where appropriate.

6.3

Finishing, Handling and Storage

6.3. 6.3.1 1

With ith th the ex excep ceptio tion of of pa packings, all all item tems of of eq equipm ipment sh shall be be mar mark ked with a part number for identification and easy assembly. Like parts may bear the same number. Supporting Supporting documentation will cross reference between assembly procedures and drawings. Structured packing elements shall not be individually marked, but only the housing container. Items shall normally be marked by metal-stamping. For materials subject to stress corrosion cracking these shall be marked using an electric discharge pen (pyrograph) or equivalent.

6.3. 6.3.2 2

A list ist with the part art numbers ers of of th the item itemss wi within thin the the co contain ainer sh shall be be provided provided both inside inside and outside outside all packing packing containers. containers.

6 . 3 .3

As fa far as as po possible th the ma manufacturer sh shall pa pack co containers so so th that unpacking for installation shall be consistent with the order of installation in the column.


PAGE 21

6.3. 6.3.4 4

Stru Struct ctur ured ed pack ackings shal shalll be pack acked in weath eather er proo roof boxes. es. Consist sisten entt with standard box sizes, elements which make up complete vessel cross sections shall be packed together for large diameter vessels.

6.3. 6.3.5 5

Rand andom dumped pack acking ings shall be packaged in bags, and shall be clearly marked with the part number of the item.

6.3. 6.3.6 6

Carb arbon stee steell part partss shal shalll be prote rotect cted ed in a dry dry sto storag rage area area.. Austen stenit itic ic stainless steel components shall never be exposed to wetting by salt water or salt spray. Protective packaging or a suitable removable removable coating shall be used to prevent such exposure.

6.4

Testing and Inspection before Installation

6.4. 6.4.1 1

One tr tray per type, in inclu cluding accu ccumulato latorr tr trays, sh shall all be be ass assem emb bled in the manufacturer's shop to the extent necessary to check dimensions. Examination shall be by the purchaser or his representative.

6.4. 6.4.2 2

All accu accumu mullato ator tray trayss shal shalll be sub subject ject to a wate waterr lea leak test est at site. ite. The permitted leakage leakage shall be be as per the schedule schedule below:Leakage category

1

2 3

Typical service

vacuum towers:lowest distillate draw vacuum towers:except category 1 all other columns

Maximum acceptable rate of level drop mm/h inches/hour

10

0 .4

50

2 .0

200

8 .0

The water leak tests will be made (with drain holes plugged) at the overflow weir height or chimney height, as applicable.

6.4. 6.4.3 3

One gra grav vity ity dist istrib ributor tor per per typ type as as use used d for for fra fract ctiionatio ation n ser serv vice shall all be tested with water in the fabrication shop before dispatch. Liquid inlet means to the distributor parting box shall be the same as that to be used in the column. The tests shall be performed at design maximum and minimum flowrates as follows:(a)

Meas Measur urem emen entt of of the the uni unifo form rmit ity y of of flow flow from from the the par parti ting ng box box or or predistributor.

Samples should be taken from each part of the parting box that discharges into a separate channel.


PAGE 22

Acceptance criteria: Liquid distribution at 50% of the maximum design flowrate, or a specified minimum design flowrate, to be within + or 4% of the mean. (b) (b)

Samp Sample less tak taken en at no less less than than 10 rand random om loca locati tion onss ove overr the the cross-sectional area of the column according to the following schedule:Colu Column mn diam diamet eter er mm < 900 900 - 1800 > 1800

ins < 36 36 - 70 >70

Approximate number of holes from which liquid is collected from each location 1 5 10

Acceptance criteria. Liquid distribution at 50% of the maximum design flowrate, or a specified minimum design design flowrate, to be within ± 6% of the mean. (c)

Measurement of liquid depth at each end and at the centre of each channel.

Acceptance criteria: The distance between the liquid level and parting box/channel/p box/channel/pan an top must be a minimum of 10% of the parting box/channel/p box/channel/pan an depth. Under no conditions conditions will an overflowing overflowing system be accepted. 6.4. 6.4.4 4

When a spr spray dist istrib ributor is used sed for a VDU wash ash zone, or sim simila ilar zon zone, it shall be tested with water in the fabrication shop before dispatch. Tests shall be performed at design maximum and minimum flowrates. A nozzle inlet pressure versus flowrate relationship shall be derived. Nozzle dimensions dimensions shall shall be checked checked against against manufacturers manufacturers data. Acceptance criteria: At any pressure the flow shall be within 20% of the stated catalogue value.

6.5

Testing and Inspection after Installation.

Weld spatter on downcomer bolting bars shall be removed to ensure a flush seal. In the event that the downcomer does not form a continuous seal with the bolting bars, the downcomer shall be reassembled using a gasket.


PAGE 23

7.

8.

GUARANTEES 7.1

Mechanical

7.1. 7.1.1 1

The manufact acturer shal shalll guaran rantee tee all all items ems supplie lied by him against defective material, poor workmanship, improper design and failure within design loadings.

7.1. 7.1.2 2

The manu anufactu acturrer shall all rep repair air or repl eplace ace fre free of charg arge any any defec efecttive ive material or workmanship found within the guarantee period.

7.2

Process

7.2. 7.2.1 1

The manu anufact factu urer shal shalll gu guara arantee tee the the ab abili ility to hand andle th the vap vapo our and and liquid loads over the specified operating range whilst retaining efficiency, when hydraulic loadings are supplied by the purchaser.

7.2. 7.2.2 2

The manu anufactu acture rerr sha shall guara arantee tee the the sep separat aratio ion n and and the the hydrau raulic lic throughput when the process design and the hydraulic design is his responsibility.

7.2. 7.2.3 3

The manu anufact factu urer shal shalll rep replace lace fre free of of ch charg arge any any new ite items req requ uired red to meet the process guarantees.

7.2. 7.2.4 4

The manu anufac factur turer sha shall guaran rantee tee that that the the desig sign and fab fabricat icatiion of liquid distributors for packed columns will meet the criteria for acceptance given in section 6.4.3 and 6.4.4.

7.2. 7.2.5 5

Any mo modifica ficattion ion ne necess cessar ary y to to me meet the le leak tightness ess qu quali alifica ficati tio on given in section 6.4.2. shall be made free of charge by the manufacturer.

REGIONAL ANNEX 8.1

USA

Where tray spacing is 915 mm (36") or greater an access ladder shall be provided at each tray manway manway.. This is a requirement of BP's refineries in the USA which at the moment (Sept '95) is not strictly required elsewhere.


PAGE 24

APPENDIX A

DEFINITIONS AND ABBREVIATIONS

Definitions

Standardised definitions may be found in the BP Group RPSEs Introductory Volume. gravity distributor:

liquid distributor using only hydrostatic head

grid packings:

ordered packing manufactured from cut out metal strips

manufacturer:

manufacturer of column internals

owner:

the operator of the column

pressure distributor:

liquid distributor distributor with with pressurised pressurised head

random packing:

packing manufactured as discrete elements distributed randomly

stru struct ctu ured red pack packin ing: g:

orde rdered red pack acking manu anufact factu ured fro from press ressed ed sheet eet metal etal shee sheets ts

Abbreviations

CS FRI HF

Carbon steel Fractionation Research Incorporated Hydrofluoric acid


PAGE 25

APPENDIX B LIST OF REFERENCED DOCUMENTS

A reference invokes the latest published issue or amendment unless stated otherwise. Referenced standards may be replaced by equivalent standards that are internationally or otherwise recognised provided that it can be shown to the satisfaction of the purchaser's professional engineer engineer that they meet or exceed exceed the requirements of the the referenced standards. British Standards

BS 4870

Approval Testing of Welding Procedures

BS 4871

Approval Testing of Welders Working to Approved Welding Procedures

BS 5500

Unfired Fusion Welding Pressure Vessels

BS 5750

Quality System for design, development, production installation installati on and Part 1 servicing.

American

ASME

Section V111 Pressure vessels, Division 1 and Division 2 Section 1X Welding and Brazing Qualifications


PAGE 26

BP_GS146-1_Column Internals.pdf

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