Chp 23 Design Criteria

Chapter 23

DESIGN CRITERIA: THE FORMAL BASIS OF DESIGN

JOHN W. SCOTT

WRIGHT ENGINEERS LTD. VANCOUVER, CANADA

INTRODUCTION

The design cr i ter ia for a particular concentration and dewatering project will provide t he formal basis for design of the process, equipment and facilities. These cr i ter ia will specify t h e required capacities and operating schedules for t he equipment, a s well a s t h e quantity and quality of t he feed t o be processed and products obtained. The general climatic and geographical conditions a t t he site, specific information on soil o r rock conditions; and applicable design standards and codes will also be included.

The design cr i ter ia will generally be based on an interpretation of testwork carried out on the particular ore and site, and will thus parallel in detail and completeness this testwork. As the project moves from the early conceptual phases through t o final detailed design, the design cr i ter ia will be developed and become more detailed as information is generated and made available for use. The design cr i ter ia a r e critical t o t he design e f for t a s t h e formal specification to t he designer of what and how much is t o be processed, what and how much is t o be produced, and where and under what conditions.

The actual design cr i ter ia will be a formal tabulation of the design basis information developed for t he project in question. For a preliminary study, this may consist of a single page of data; fo r a feasibility study several pages and for a detailed design up t o several hundred pages and multiple volumes. Depending on t h e complexity of t h e process and t h e level of detail included, each project will be unique t o some degree.

The design process for a project normally progresses from preliminary conceptual phases through t o a final detailed design. The cr i ter ia used for t he initial concepts a r e generally developed from rough data and preliminary testwork on t he ore in question. Regardless, t he plant throughput and products a r e defined, thus giving a scope and definition t o the study phase. In some studies a range of throughputs may be analyzed in order t o arr ive a t t he most economically a t t rac t ive size for t he proposed operation. This optimum size is then used as the design throughput for t he more detailed design phases. Similarly as more testwork results a r e available and the ore characteristics and process become more well defined a continuous updating of the design cr i ter ia is undertaken.

CONCENTRATION AND DEW ATERING CIRCUITS

At the completion of the preliminary design phase or basic engineering, sufficient information will be available to prepare a formal design cr i ter ia document which will form the basis for detailed design work. It is important tha t a t each phase of the development of the project when cost est imates or studies a re prepared, the design cr i ter ia used to form the basis of design and estimation for this phase are carefully and fully documented. DEVELOPMENT OF DESIGN CRITERIA

Conceptual Designs

At the outset of ' the conceptual design phase for a concentration and dewatering plant there will normally be little information available. The f i rs t task of the conceptual design group is t o gather what information is available and then develop tes t programs to provide t he essential da ta tha t is missing. During this phase, the metallurgical response of t he ore is the most important a s i t will define the flowsheet and equipment requirements. The ore will be characterized mineralogically and a bench scale test program will be developed and carried out on the available samples (normally split drill cores) to provide basic information for flowsheet development. If the ore is widely variable, the flowsheet will be designed accordingly and a further more detailed metallurgical t es t program planned.

The basic document produced will be a metallurgical and material balance t o provide flows and tonnages for equipment sizing and selection. If sufficient material is available, batch thickening and filtering tests will be run t o give preliminary unit area requirements, however these may be adjusted by experience factors a t this s tage if abnormal a reas or sizes a re indicated. Further testing would be planned and carried out for the next s tage of project development.

The design criteria for the other

disciplines required a t this phase are minimal, with the cr i ter ia used general in nature and based on similar projects in similar climatic areas to give a reasonable and sound basis to the preliminary estimate.

Feasibility Studies

A feasibility study is normally undertaken a f te r an order of magnitude or preliminary est imate has indicated tha t the project (or expansion or renovation) is financially at t ract ive enough t o merit fur ther work. During the preliminary study scoping tes t s would have been completed on the metallurgical response of the ore and a generally suitable flowsheet selected. Any problem areas requiring resolution with further testwork would have been identified and suitable laboratory and pilot plant programs initiated. The pilot work, in particular, would be aimed a t verifying the flowsheet and also providing a n opportunity for thickening, filtration, drying and other ancillary tes t s on samples produced from more or less continous operation on representative bulk samples. The e f fec t s of recycle water s t reams on the metallurgy will have been noted, with provision made for water t reatment or possibly even a once-through system. For physical separations, unwanted slimes buildups, the need for settling ponds o r unusual drying requirements, etc. will have been noted. Unusually abrasive or slimy characteristics will have been observed and noted. The small flows typical in pilot plants exaggerate the rheological problems encountered in certain ores and these also will be studied a t this phase; particulary for extremely fine grinds and high pulp densities -characteristics perhaps more common in present day ores. The feasibility study will have considered any alternative processing schemes in depth and rejected all except the most logical and profitable via a series of technical- economic studies. Metallurgically, the ore will have been studied thoroughly on the basis of pilot plant t es t s on

DESIGN CRITERIA: FORMAL BASIS OF DESIGN

representative bulk samples, thus providing a valid design basis.

The plant s i te will now have been selected and the buildings and facilities laid out. The s i te will have been drilled for geotechnical information and carefully surveyed to provide surface contours and an es t imate of cu t and fill quantities. An effort will have been made to find local materials suitable for compacted fill, and for concrete aggregate in t he case of remote locations. The bearing strength of the soil and underlying bedrock will be tested and cr i ter ia for foundation design prepared. Architecturally t he climatic conditions will be carefully noted, and a program to develop wind and snow loadings under taken if necessary, otherwise local/regional records will be used. Prevailing winds and severe cl imatic conditions will be considered t o ensure the best orientation of buildings and openings in the buildings, subject to s i te constraints.

Power supply will have been studied, with power factor correction allowed for. If there a r e high energy costs self- generated power or high efficiency motors (with accompanying higher capital costs) will be considered.

Water supply and tailings disposal will have been carefully studied, with hydrological and geotechnical studies commissioned a s required.

At the end of the feasibility study, the metallurgical response of t he ore, general s i te conditions, climatic constraints and power, water and waste disposal systems will have been identified, studied and resolved.

Basic Engineering and Detailed Design

Following a positive feasibility study, the next phase of a project involves basic engineering followed by detailed design. The basic engineering for a project involves developing the

feasibility study t o a point where t he major equipment has been tendered, a supplier recommended and design advanced to a point where detailed engineering can commence. The end product is the detailed design cr i ter ia document, serving a s a specification t o the detailing engineer and a basis for t he project budget estimate.

At the commencement of the basic engineering, a draf t design cr i ter ia document will be prepared, based on a format used by the particular engineering company doing t he design work. The preparation of this draf t will normally bring t o light a number of areas where specific design criteria a re missing, so tha t relevant test work can be carried out or the necessary information obtained. As the engineering progresses and major pieces of equipment a r e committed t o purchase, actual weights and dimensions of the equipment in question will be available for inclusion in t he appropriate sections of the criteria. At the same time, t he flowsheets and general arrangement drawings will be updated t o show the recommended equipment. The mechanical, structural and civil groups will work very closely with each other during this period t o ensure tha t t he basic cr i ter ia a re available for such problem areas in the design a s large rotating equipment or severe vibration.

At the completion of the basic engineering, the formal design cr i ter ia will be issued t o serve a s the basic document for detailed engineering

Use of Cri ter ia during Design

The design cr i ter ia are used throughout all s tages of a design a s the primary wri t ten source of information for the engineers carrying out t he design work, and the source document for further work.

Conceptual desiqn. In the in i t ia l conceptual stage, the general criteria wi th respect to plant capacity, ore characteristics and preliminary metallurgical results are used t o develop a flowsheet and preliminary plant layout. The metallurgical and mechanical engineer wi l l rely on the criteria to prepare the flowsheet and size and select the major process equipment. Based on this work and any site constraints a plant layout w i l l be developed to form a basis for cost estimation. The areas where the criteria are poorly defined or missing wi l l be covered by past experience at this stage, and testwork or site investigations planned to obtain the missing information. The cr i ter ia used, including the assumptions made wi l l be formalized i n a short summary and included i n the study report. (See Table 1).

TABLE 1. CONCEPTUAL DESIGN - OUTLINE OF DESIGN CRITERIA

1. GENERAL CRITERIA 2. METALLURGICAL BALANCE 3. OPERATING SCHEDULE AND

THROUGHPUT 4. PROCESS CRITERIA 5. ASSUMPTIONS 6. RECOMMENDED TESTWORK

Detailed feasibility Study. For the detailed feasibility study phase of a project, the general operating and metallurgical design cr i ter ia w i l l have been refined and augmented by further laboratory and pilot plant testing.

A series o f alternative flowsheets may be developed a t this stage, w i th the technically and economically "best" one selected for further development. Once again, the criteria available w i l l be checked with the selected flowsheet and any deficiencies covered by further testwork. A t this stage the plant site w i l l have been carefully surveyed and soils investigations carried out t o provide site specific design criteria t o the structural and civ i l engineering groups. The information developed wi l l

again be collected and included i n the feasibility report as a separate 'IDesign Criteria" section (See Table 2). Based on the design criteria an d the selected flowsheet, the mechanical equipment w i l l have been specified and quotations solicited from suppliers to obtain sufficiently accurate cost data for the report. The plant layout w i l l have been refined and developed to provide a good basis for c iv i l and structural takeoffs and preliminary design work. The power supply and electrical requirements w i l l be defined by the equipment selection, and yard and building lighting, heating requirements, etc. The architectural finishes w i l l be selected on the basis of the duty, weather and plant areas. The cr i ter ia used for this selection wi l l be experience i n similar installations and any specific chemical resistance required.

TABLE 2. FEASIBILITY STUDY - OUTLINE OF DESIGN CRITERIA

SECTION I 1.- INTRODUCTION 2.- GENERAL CRITERIA 3.- OPERATING

SCHEDULE AND CAPACITY

4.- METALLURGICAL BALANCE

SECTION I1 PROCESS DESCRIPTION EQUIPMENT DESCRIPTION . FLOTATION /

MAGNETICSEPN/ ETC.

. THICKENING AND FILTERING

. DRYING AND PACKING

3.- FACILITIES DESCRIPTION . BUILDINGS . SERVICES . SITE AND ACCESS

4.- REQUIRED TESTWORK


Detailed desiqn. Detailed engineering w i l l be crit ical ly dependent on design criteria, and i n fact the f irst phase of detailed design or basic engineering is carried out to provide a detailed design criteria to be used as the basis for f inal detailing.

During the basic engineering the equipment tendered on wi l l be selected, and the flowsheet, equipment l is t and general arrangement drawings up dated to their f inal form. The design criteria developed for the detailed feasibility study wi l l also be updated, and any further information included as i t is made available. A t this stage, actual equipment loads w i l l be available so structural and foundation design may be advanced. Normally, the f i rst detailed process and instrumentation diagrams are developed and w i l l form the basis for piping design i n conjunction wi th the flowsheet. Final selection of such equipment as filters, dryers and thickeners wi l l enable a detailed water balance to be prepared, providing the flows o f fresh and reclaim water as the design cr i ter ia for the water system. The heating and ventilation requiremerts w i l l have been defined by the cl imatic conditions and by any local codes and ordinances. Similarly codes governing noise levels and personnel protection wi l l be incorporated into the criteria to ensure compliance.

As the basic engineering proceeds, areas wi l l turn up which require further specific tests for design to proceed. These would be carried out and the criteria updated i n those areas. The f inal document produced a t this stage is known by various names: design criteria, design basis memorandum, etc. However i t w i l l consist o f a formal document including al l design criteria used, a description o f the process and the set o f basic engineering drawings. These documents then form the basis for the detailed engineering design. A generalized table o f contents for such a document is given i n Table 3.

TABLE 3. INDEX FOR A DESIGN CRITERIA

I.- General Criteria

1.0 Introduction

2.0 Scope of Work

3.0Criteria Summary

4.0 Mechanical Design Cri ter ia

4.1 Conveyors 4.2. Chutes 4.3 Fabricated Items 4.4 Process Pumps 4.5 Piping 4.6 Linings 4.7. Codes and Standards

5.0 Electrical Design Criteria

5.1 General 5.2 Codes and Standards 5.3 PowerSupplySystem 5.4 Main Substation 5.5 System Voltages 5.6 Emergency Power 5.7 Metering 5.8 Distribution Switchgear 5.9 600 Volt Power 5.10 Motors 5.11 Power Factor Correction 5.12 Motor Controllers 5.13 Controls and Pilot Devices 5.14 Lightning and Surge

Protection 5.15 Grounding 5.16 Overhead Transmission

Line 5.17 Lightning and Receptacles 5.18 Wiring Methods 5.17 Wire and Cable 5.20 Conduit 5.21 Enclosures 5.22 Cable Tray 5.23 Special Equipment 5.24 Communications

6.0 Structural Design Criteria

6.1 General 6.2 Design Loads 6.3 Uni t Stresses andLimiting

Deflections 6.4 Load Factors 6.5 Load Combinations

7.0 Mechanical Services Criteria

7.2 Design and Drafting Standards

7.3 Materials 7.4 Design Conditions 7.5 HVAC 7.6 Building System 7.7 Plumbing 7.8 Fire Protection

8.0 Air Pollution Control Criteria

8.1 Codes and Standards 8.2 Materials 8.3 Design

9.0 Architectural Design Criteria

9.1 General 9.2 Washrooms 9.3 Change Rooms 9.4 Lunch Rooms 9.5 Offices and Labs 9.6 Building Enclosures

10.0 Instrumentation Design Criteria

10.1 Purpose 10.2 References 10.3 General 10.4 Instruments 10.5 Control Panels

11.- Process Area Cri ter ia

11.0 Operating Schedule and Capacity

11.1 General 11.2 Schedules and capacity

12.0 Process Metallurgy

12.1 Ore Characteristics 12.2 Metallurgical balance 12.3 Material balance

44.0 Water Supply 44.1 Operating Criteria 44.2 Process Description 44.3 Equipment

47.0 Tailing Disposal

47.1 Operating Criteria 47.2 Process Description 47.3 Equipment

51.0 Ancillary Buildings

51.1 Offices 51.2 Change House 51.3 Laboratory 51.4 Shop & Warehouse

92.0 Conditioning and Flotation


93.0 Reagents

93.1 Operating Data Summary 93.2 Reagent Preparation and

Equipment Description 93.3 Reagent Fume and Dust

Control

94.0 Hydrosizing & Tabling


95.0 Filtration and Drying


97.0 Concentrate Packing & Storage


REQUIREMENTS FOR DESIGN CRITERIA

The requirements for design criteria for a specific concentration and dewatering circuit are naturally dependent on the particular ore, the flowsheet chosen and the s i te constraints. Normally, the design criteria will be developed in two complementary sections; the first generally including a description of the ore, process, plant s i te and geographical location along with the general design criteria developed by each engineering discipline. The second section will present design cri ter ia for each area of t he plant and process including an

operating da ta summary and detailed process and equipment descriptions. The general arrangement drawings, flowsheets and process and instrument diagrams form an integral part of the design cr i ter ia documentation and a r e included and referenced extensively for clarity and convenience.

General

The general design cr i ter ia consist of the basic project description plus t he general cr i ter ia for each engineering discipline. The outline for a complete design cr i ter ia manual a s required for detailed design is provided by the index referenced in Table 3.

The summary of basic design cr i ter ia will include:

Description of the project Scope of work Location Meteorlogical da ta Site and soils description Utilities Transportation Applicable Laws and Codes.

Operating Schedule and Capacity

The heart of any design is the required plant capacity and t h e operating schedule. These define t h e s ize of t he equipment and t h e operating duty. The operating schedule is normally twenty-four hours per day, th ree shifts per day, 365 days per year for a typical concentrator. In some cases t he plant may be designed to operate fewer days per week but continuous twenty-four hour operation is usual. In some dewatering sections filters may be operated on a single shift basis, this will be clearly set out in t h e design cr i ter ia for t h e area. In addition t o t he operatinq - schedule and throughput, some estimation of t he availability of the

function of t he maintenance requirements of each individual piece of equipment and also the operating strategy of the plant. For instance, a weekly maintenance shift may be planned for certain areas due t o required preventive maintenance on certain critical i tems of equipment. These i tems in the design cr i ter ia a r e normally tabulated in a format a s shown in Table 4.

TABLE 4 - TYPICAL OPERATING SCHEDULE

PLANT AREA

PERIOD FLOTATION

Availability (%I) 94

Process Metallurgy

The design cr i ter ia for process metallurgy will include a description of the ore treated, the products t o be made, t he physical and chemical characteristics of t he ore which a f fec t the process, an estimated metallurgical balance, reagent additions, nominal aquipment residence t imes and product specifications. The metallurgical cr i ter ia for each a r ea of the plant o r unit process a r e normally summarized in an Operating da ta summary for these areas and a r e utilized with a n accompanying process and equipment description t o provide a complete cr i ter ia for detailed design.

plant is used for setting the actual hourly throughput. This availability is a

CONCENTRATION AND DEWATERING CIRCUITS

Typical design cr i ter ia requirements for the normal unit operations encountered in concentration and dewatering circuits a re summarized in the following tables. The testwork required t o obtain the required design cr i ter ia values is beyond the scope of this paper, and is more than adequately covered in the other chapters of this book. The process metallurgist normally requires sufficient testwork t o prepare metallurgical and material balances for a selected flowsheet and size and select the major process equipment for the flowsheet. The selected flowsheet and equipment then provide derived design cr i ter ia for laying out the plant and the subsequent detailed design in all areas.

Basic Metallurqical Cri ter ia

Ore mineralogy Metallurgical balance Material balance Feed r a t e (and variations) Particle Size Distributions (Feed and Products) Specific gravity (Feed and Products)

Supplementary Criteria

Froth Flotation: Flotation r a t e da ta

Air requirements Conditioning t ime Reagent additions

Gravity Separation: Heavy liquid separation

tes t results Laboratory and/or pilot plant results for: Jigging, Tabling, Spirals or Cones. Extended Mineralogical Analysis. Classification characteristics

Magnetic Separation: Magnetic susceptibilities

Laboratory tes t results Magnetic field strength required

Electrostatic Separation:

Electrical properties Laboratory tes t results Field strength Dryness and temperature requirements

Thickening: Unit a rea requirements (Laboratory o r pilot plant) Flocculant mixing requirements Flocculant ra tes Underflow densities Overflow clarities Slurry rheology (if underflow is non newtonian)

Filtering: Unit a rea requirements Cloth permeability Vacuum requirements Form t ime Dry t ime Cake thickness Slurry rheology Filter Aid requirements Cloth washing requirements Air blow requirements Altitude e f fec t s

Drying: Feed moisture Product moisture Dusting characteristics Off gas volumes and dust loadings Operatings schedule Heat capaclty of solids Relative humidity

Engineering Disciplines

The engineering disciplines involved in a concentrator design will include:

Metallurgical Mechanical Electrical Civil / Structural Mechanical Services Architectural Instrumentation and Control

The design cr i ter ia required by each of these disciplines is outlined in t he typical index given in Table 3. As can be seen each discipline requires a general compilation of design codes and standards as well a s specific cr i ter ia for the various a reas covered by the discipline. The full details of the general cr i ter ia would require more space than is available in this book, however a typical excerpt from the general design cr i ter ia for each discipline is presented in Appendix I. The references t o codes and standards normally refer t o Canadian Standards, fo r plants built in other countries the applicable national, s t a t e and local codes would apply.

For each discipline involved in t he detailed design there a r e a number of basic cr i ter ia based on fundamental design pract ice for tha t discipline and other points which a re specifically related t o concentrator design. These have been developed through experience and a r e particularly required when the detailed design is being carried ou t by a firm less involved in the mineral industry, perhaps off-shore in an under developed country or in a country with few mineral resources.

Metallurgical. The metallurgical cr i ter ia normally required for each of the unit processes a r e listed in a previous section. In addition t o t he process criteria, an operating philosophy for the plant is normally developed which ref lects the plant location and t he human resources available t o operate it. This operating cr i ter ia should be carefully thought out and wri t ten down in order t o be of use t o the design t e am and for the training of operating personnel.

Mechanical. The mechanical engineering for a concentrator, once t h e major equipment has been selected, is mostly involved with material handling, pumping and design for minimum spillage and easy maintenance of the eqipment.

In this respect, t h e design cr i ter ia a r e particularly specific t o concentrator, with such points a s launder slopes, pipe connection details, wear liners, conveyor skirting and pump selection being critically important. With the use of finer grinds in some flotation plants, t he behavior of thickened slurries and other pulp s t reams has become Less predictable, therefore slurry viscosity testwork for pump and piping selection has become more common.

Electrical. The electrical design criteria for a plant normally involve an extremely wide scope possibly from s i te power generation t o wiring details. Particular emphasis must be given t o energy conservation through such methods as power fac tor correction, high efficiency motors and lights and correct cable sizing.

Civil / Structural. The structural design requires particular emphasis on rotating equipment, vibration analysis, and recognition of plug loads in such vessels as flotation tanks and conditioners. In addition, careful investigations of t h e underlying soil or rock characteristics a r e required for successful foundation design. Care should be taken a t the earliest opportunity t o obtain a s much information a s possible over t he ent ire mill site, a s buildings may be relocated several t imes during the progress of the design.

Mechanical Services. The services required in a modern concentrator complex for heating, ventilation, fire protection, plumbing, sewer and water supply, etc . can be a major design area. It is essential t o develop the design cr i ter ia for these a reas in accordance with local codes and regulations and also bearing in mind the number of workers in the plant. Sanitary services must also consider the provision of separate facilities for men and women as well a s for supervision and labour. This s e t of cr i ter ia must be carefully discussed with the operations personnel who are involved a t t he design stage.

CONCENTRATION AND DEWATERING CIRCUITS

Architectural. The architectural cr i ter ia generally ref lect the style of building exterior and interior finishes desired for t he plant. In addition, the provision of specific cr i ter ia for heavy use areas, particular chemical resistance requirements, and climatic considerations a re important. The development of cr i ter ia for offices, washrooms, drys and laboratories requires a detailed description of the proposed work force and operating schedules for the various areas.

Instrumentation. The instrumentation desiqn cr i ter ia a re normally developed in con jkc t i on with the -process. and mechanical engineering groups, and in accordance with the proposed operating criteria. The specific instruments chosen for each application will reflect an overall control philosophy for t he plant whether i t is computer based, distributed control o r simply local start-stop switches for simple circuits.

The particular design cr i ter ia referred t o in Appendix I refer t o a tungsten concentrator incorporating both flotation and gravity concentration. The criteria developed for a large base metals flotation concentrator or an iron ore concentrator utilizing spirals or magnetic separation would be similar in nature but ref lect the specific ore and process under consideration.

Plant/Process Area

For each a rea of the plant and stand alone unit processes, such a s flotation, the design cr i ter ia will specify the operating criteria, a process description and a detailed equipment description.

The operating cr i ter ia include the operating schedule for the particular area along with the availability predicted for the equipment, and the nominal flowsheet and design throughputs. The relationship between nominal and design flows is of ten misunderstood and should be clearly explained and specified in the design cr i ter ia , and if possible noted on the flowsheets a s well.

In t he initial operation of the plant this may not be a major point, but a t t he s tage where debottlenecking, production limiting factors and possibly expansion become a fac t of life, there is a critical need for such information t o be well defined and available.

Onceagain,spacelimitationsprevent including a complete design criteria for al l process a reas of a typical concentrator, however excerpts from a s e t of process a rea cr i ter ia developed for a tungsten concentrator a r e given in Appendix 11. The areas covered a re generally applicable t o most concentration/dewatering plants but naturally would be augmented and modified specifically for the plant and process being designed.

The equipment descriptions in this particular design cr i ter ia are not specific a s t o supplier, a s t he equipment has not yet been purchased. In a fully detailed design cr i ter ia for a project in detailed engineering, the major equipment would be committed t o and would be described specifically. As this equipment is purchased, the design cr i ter ia document will be updated t o ref lect the particular machine t o be installed.


SUMMARY AND CONCLUSIONS

The compilation and use of a formal design criteria document is essential to the engineering design of concentration and dewatering circuits. Careful preparation of this document prior to commencing detailed design along with continuous updating ensure a consistent basis for design in al l areas and for al l disciplines involved in the design.

LIST OF APPENDICES

APPENDIX I Examplesof General Design Data

APPENDIX I1 Examples of Process Area Criteria

ACKNOWLEDGEMENT

The assistance of my colleagues at Wright Engineers L td , particularly Brian Montpellier, Project Manager and management permission to prepare this paper are gratefully acknowledged.

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6.0 STRUCNWY DESIW CRITERIA

6.1.1 Lildirw Code Standards

All buildings and their structural melbffs shall be designed to r s i s t safely and effectively all lmds and all effects of loads and influences that may reasonably be expected, and shall in all cases satisfy the r w u i r m t s af Section 4.1 of the National Building Code of Canada 1960 and standards set fwth by eight Engineets Limited.

Except as set f a t h in Article 4.1.1.4 Subsectim 2.6.2. of the National kildinq Code of Canada 1WO the followin shall apply:

Fmdations, excavations, soil and rock retaining structures shall confar to Subsection 4.2.4 of the National Building Code. h twia l s to be used in fmdatiuns (Subsection 4.2.3)

kildings and their structural d w s .a& of wood shall m f w a to CSA Standard Can. 3-DEHW 'Code for Engineering Design in Ycodm.

( i i i ) hmv Structures

Buildings and their structural u*bers made of plain and reinfmed masonry shall cmfa r to CSR Standard ~-530( -H78 'ksmry Design and Cmskwtim for Buildingsn.

(iv) Concrete Structures

Wlildings and their structural &err ude of plain, reinhced and prestressed c ~ c r e t e shall cmform to CCYad23.3-Kn 'Code for the Design of C m t e Structures fw Buildings:. For establishing 'design load factas*. the tabulation in Section 6.4 of t h u criteria shall be used. I t is based on the N.B.C. 1080 factors but expanded for special loads and effects acting on rinins projects.

(vl Steel Structures

(a) hildinss and their structural &ers made of structural steel shall confag to C% Standards 516-1969 'Steel Structures fw hildings".

( b ) Buildinss and their structural &ws mde of light gauge steel &all cmfam to CSA Standards 5136-1074 "Cold Formed Steel Structural tlelrbas".

Standards

Before structural design or detailing conrences m any sectian of the woject, reference shall be made to Kisht Enginems Limited desi.gn and d-afting standards to ensure that a l l item c m l y with these standards.

6.2 Desiqn Loads

bcund snar load 2.9 Mlsq U. Snar load coefficients to be deterained frm coaentary H of the wppleeent to the NBC.

7.0 tEMW SERVICES CRITERIA 7.3 kterials

7.1 k i a Codes and Standards

All desiv shall be in accordance with the following codes and regulations:

- The Ltional Wlildinq Code of Canada - latest edition - The Canadian Heating, Ventilating and Air Conditioning Code - latest editim

- Cli~tic Information for Building Design in Canada - latest edit ion

- The Federal Ministry of Energy, nines and Petroleua Reswces, ninwal Resarrces 8ranchr invirormental Reulations - latest edition

- Underuritwls Reconmendations - The lbtional Fire Code of Canada 1977 - latest edition - Ontario Plumbing Code -latest edition - Pressure Vessels and Piping Regulations as issued by the

Euvanaent of the N.W.T. - Canadian Standard Association - kplicable local Codes. HWlC systens shall be designed and constructed in accordance with established engineering principles using the publications of the following associations:

- The bride and Data Boaks of the lkrican Society of Heating, Refrigeration and Air Conditioning Enqinews (W).

- Sect lletal and Air Conditioning Contractor's National Assaiatim Inc. (SMM) Duct Constructim Standards.

7.2 Desiw and Draf tins Standards

Drafting Ball confwm to Yight Engineers Limited Drafting Standards and Syabols. Drawings shall be prepared using the Guide f m the Canadian Mining and htallur.qica1 Industries, by the nining Association of Canada. &i@t Engineers Limited's Design Standards shall be used throughout unless otherwise specifically noted.

kterials used in the MHU: pluobing and fire protection s y s t w rill ccwly with the applicable standards referenced in the National Building Code of Canada and other avplicable c&. Haterial not covered by these standards a materials f w special conditions will cmply to such other standards as are approved f a the particular ap~lication.

WCLC E w i p m t will be selected for heavy duty industrial service. Comercia1 duty w u i p m t will be restricted to use in ancillary

bui ldings.

Ventilation ductwk will c w l y to the applicable SIYWJA pressure - velocity classification except that in process buildings and elswhere exposed to possible M e the a i n i m Pressure classification will be 2' ffi.

7.4 ksiqn Conditims

The heating systeas will be k i g n e d f a an outdoor winter teweratute of -5 deg C except &en the systems are to be designed to prevent freezing only, in which case an o u t d m t w w a t u r e of -20 deq C will be used.

The ventilating and air conditioning systeK will be desiped for cutdwr s w cmditims of 35 deg C.C.D.B. and 31 deg C.W.B.

Indmr temperature and relative humidity will be as noted f a each area.

7.5 Heatinq, Ventilatinq a d Air Conditioning

8.0 AIR POULIIIW (ItNlm DESIGI( CRITERIA

8.1 Codes and Standards

Pollution control shall be provided to k e s the concentrafian of contaminants belor acceptable threshold limits nithin occupied work areas.

kight Ensines Liaited's design and draftins stanbrds +all-be used throughout un!eis otheruise ~eci i ical ly noted.

All vork shall be carried out in accordance with the Clean Air Actl and all othw acplicable Lmal. and Natianal Standards and Codes. The systems shall be designed and constructed in accordance with stablished enqinewing principles usins the foilwinq p~ublications as an accwtable standard:

industrial Veiitilation by the kerican Conference of 5overnrental Industrial Svgienistr.

Shest Hetal and Air Ibditioning Cmtractor7s Ltimal Association Inc. (SMCCW hct Construction Standards.

Plant and P~OCESS Ventilalion by Y.C.L. Heaeon.

Design Guidelines for Oust Ccntrol at Nine Shafts

and Surface Gperatians by the bt imal kthority.

Fume ductwak and equipment shall be constructed of corrosion-resistant material applicable to the fumes being handled. Oust hmds. enclosures and Qctmk shall be constructed of galvanized a black steel to Might Ensinws Linited Qsign standards.

Equipment shall be selected for heavy Ctv industrial service. Fans gmwally shall be Class I1 constructim and dust c o l l ~ t a s shall Ce constructed of relced steel plate.

8.3.1 Fume Crntrol

In working areas threshold liraits for abmphwic contaminants shall not exceed the values published in the llp~eitdix to "Industrial Vmtilatim*.

(111 horizmtal duct runs shall be slaped fat. proper lfainage and flushing. Drop-out boxes shall be incaporated at the top of verticzl risers !rm vessles, hhere

neceswy. Air ba!ancing shall be achieved bv dwws and tram air inlet s t~hs Mere necessary. Ductmk shall be flanged at strategic locatims for ease of installatim rr diwntlins *here neceswy. Fuoe collectors, Jlere rquired, shall be selected to maintain fuw emission at u below levels established by the Governrent in the Clean Air Act and kctic Hining Eaissiclns fict.

In genera11 all f w control stacks shall exhaust wtdwrs above rwf level.

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92.2.2 Upqrack Flotatim

92.0 Sulphide Cmditiminq and Flotation

92.1 Cueratins Criteria

9.1.1 Primary Flotation

- Solids F!ow 33 mtph - %lids S.6. 3.4 - hlp Censity 322 Solids nlw - Tic2 5 min.

42.1.1 S~ccindarv F!otation (U~qpqrade Plant)

- Eolids Flow Batch !4.3 tlbatchi

- Salids S.G. 5.4 - F~lp Densitv = . =QL

bl ids nlw - Tine IS

ninlstase

92.2.1 Primarv Flotation

Depmding on the Sulphide content of the ore zone being mined, rod mill screen underflow will go directlv to lar intensity net mayetic separatim or be by-passed ta sulphide flotation. Pulp will be conditioned in sulphuric acid and flotation reagents to bring the pH to 4, and floated for 5 minutes in a bank of 8 50 cu. ft. cells (Denver DR 24 or yuivaleit) to produce a

The upgrade circuit has 2 batch flotatiai systems, cne for ccarse concentrate (4 cells) and one for fine concentrat= (2 cells). Cells are al! 54 cu. f t . barse batch flotation i s sized at 4.8 tmn~slbatch for 50 minutes. Fine batch flotation i s 2.64 tonneslbatch h? 40 rinutes.Throuawav flotatim concentrate will overflu to a decision tank beiwe being vmed to the tailings thickener to ensure the sch~elite cmtent is acceptably lm.

??.:.I kcid C~ndltionw Tanks

Trc !.:a .: 2.11 hi?h riid stcei rthber line2 conditicrlin~ tank receivins slirrry from the rod nil1 scr'ew. t!uhsnical asitation is prcvided by a sos~.ntkd i.wellw nounted on an overhead frane. The agitators are driven by ar. eleitric aotm thr~uqh a V-belt &ive and rilht

an?le seat. box. Flsw thrwsh i s by gravity..

The tanks contains vertical b a f f l ~ to ninioize urirling and 0.5 in minim freeboard to prevent splashing over the sides. The tanks have XI ovwf low pipe to channel eergmcy overflor product to the floor drain and suq.

thrcw away sulphik cmentrate. Cell tailing will be neutralised with l iw and passed over LIHS befwe deslimins, hydrosizinq h tabling.

92.3.2 Lime Cmditimer Tanks

The l ire cmdi timing -1s consist of two 1.5 a did. x 2 a high tanks. The tanks are cmstructed of rubber lined mild steel. V-drives and right angles yearbaxes m t e d an werhead frsmes power the suspended impellers.

Flow t h r q h each staqe i s by gravity. The tanks cmtain vertical anti-cwirl bafiles and have a sininurn of 0.5 e Ir~ebcard.

02.3.3 Flotation Cells

l3e numbers and sizes oi the flotatian cells are tabulated be1ou:-

at Ripary circuit 8 % 50 cu f t . b) Coarse Upgrade 4 x 50 cu ft . C) Fine lbgrade 2 r 50 cu ft .

The cells are fabricated f rw aild steel plate and areas subject to abrasion are covered with rubber. 1111 cells are acid proof. Cells are single or duuble overflow froth discharge type, supplied with feed, junction and discharge bcxes. Fulp W t h level is adjusted by neir bars a t junction and discharge boxes.

The spindle bearing housing and drive notor i s tank minted. Drive i s via, vee beits and sheaves, and sized with a 1.15 ssr-vice factor.

Froth collection l a u n k are Prwirkd at each bank of cells. Construction and slope of laundrss canforn to WEL Standard 56-540.

92.4 Reaqent Preparatian

Reasent Ccnsuwt im

CWPW Sul~hate Sulphuric k i d Frothw Xanthate Lime

kqlt kqlt &It kq/t kglt

92.4.2 Reasent Re~ara t i a i and Eaui~lnent Oescri~tion

Nost reagents have a two tank rix/stwe svstm. All vessels are PVC where practical.

92.4.2.2 bppw Sulphate

This reagent i s received in bags. I t is dissolved in an agitated nix tank and stored in an agitated hcldinq tank.

42.4.2.4 Sul~huric Acid

WI1k rulphuric acid frtu a stacaqe tank is pumped to a dilutionlholdin~ tank in the s i l l .

Documents

Chp 23 Design Criteria