IBP1038_09

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______________________________1 General Manager, BRASS Chile S.A.2 Ph.D., Chemical Engineer BRASS Chile S.A.

IBP1038_09

AN INTEGRATED APPROACH TO ROUTE SELECTION INSLURRY PIPELINE DESIGN

ROY G. BETINOL, P.E.1DR. NARA ALTMANN2

Copyright 2009, Brazilian Petroleum, Gas and Biofuels Institute - IBPThis Technical Paper was prepared for presentation at the Rio Pipeline Conference and Exposition 2009, held between September,22-24, 2009, in Rio de Janeiro. This Technical Paper was selected for presentation by the Technical Committee of the eventaccording to the information contained in the abstract submitted by the author(s). The contents of the Technical Paper, as presented,were not reviewed by IBP. The organizers are not supposed to translate or correct the submitted papers. The material as it ispresented, does not necessarily represent Brazilian Petroleum, Gas and Biofuels Institute opinion, or that of its Members orRepresentatives. Authors consent to the publication of this Technical Paper in theRio Pipeline Conference Proceedings.

Abstract

The pressure to get engineering projects done and constructed as fast as possible in order to take advantage ofthe high prices in metals and petrochemicals has been driving companies to skip the conceptual phase and go straightinto basic engineering with cost estimates in the level of 15% accuracy. By-passing early engineering and demandinghigher cost estimating accuracy is a contradiction. In most cases, savings made on capital investment is much higherhad money been spent in conceptual studies which allow for the optimal solution to be found. This paper reviews oneof the key aspects in conceptual engineering of slurry pipeline designs: route selection. This activity is oftenoverlooked, causing capital cost and operating difficulties to rise unnecessarily. This paper describes and givesexample on how an integrated client/engineering companys approach to route selection can produce significantsavings in pipeline construction and operating costs.

1. Introduction

In not too distant past, mine development relies on the old mentality that mine process plants must be locatedas close as possible to the mineral ore deposit. After the process plant is designed, mine developers then considers howto transport the product to the market or nearest port of export. This is true when it was a common belief that the onlyway to bring the ore concentrates to the nearest port is by trucking or by rails. Up until some 30 years ago, where longdistance pipeline transport for commercial use is a relatively new concept, mining operators tend to stay away from itfor fear of pipeline plugging leading to loss of production. However, this concept has since changed when numerouslong distance slurry pipelines has been designed and successfully put into operation with proven high availability andreliability. With this as a viable option, most mine development now considers mine product transport as one of the key

parameters in mine planning and design.

Evaluation of the long distance slurry pipeline takes into account two major important factors: 1) the pipeline route and,

2) slurry properties. Route selection is the most critical aspect in the design of the long distance slurry pipeline as it hasthe highest cost impact on capital investment. This paper will focus on the first aspect, with discussion on the differentkey issues that must be addressed.

In a long distance pipeline system, the impact of by the pipeline material and construction cost can reach up to 60% ofthe capital expenditure (CAPEX). Therefore, for each kilometer length of pipeline saved, impact in cost savings issignificant.

2. Route Selection Considerations

Route selection is an iterative process that goes through at least 3 cycles during the project development.During the early phases of the design as in Pre-Conceptual studies pipeline route evaluation normally involves the

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review of two or more alternative routes and concluding with a selected route. During the succeeding phase of theproject, which is usually referred to as the Feasibility Study phase, the selected route is refined with more detailedmapping where environmental permitting and land right-of-way acquisition is secured. During pre-construction orDetailed Engineering phase, a more precise pipeline alignment sheet is developed with a narrower corridor sufficientfor construction.

Each of the progressive stage is designed to eliminate construction difficulties and optimize ease of operationand maintenance. This is a collaborative process between the hydraulic design engineer, construction specialist and thegeohazard specialist. The specialists should unanimously agree to produce an economical and efficient route. Thefollowing considerations must be addressed:

1. Optimized hydraulic engineering considerations. The objective is to attain the lowest possible pumping headand the shortest possible route for a more economic operation. A low head translates to low energy use for thepump motors reducing operating expenditures. The typical route must be as direct as possible and preferablyon a continuous downward grade with no high points along the route.

2. Slope Restriction. This is an important factor to consider for slurry pipeline. It determines the ease ofshutdown and restart operation in order to avoid pipeline plugging.

3. Geotechnical evaluation. This activity identifies any geo-hazard such as rock falls, landslides, seismic faults,etc, that may be showstoppers during pipeline construction. If is important to identify these hazards and

avoid them if possible. If, however, it is not feasible or economically convenient to re-route the pipeline, thenspecial design considerations shall be taken to mitigate possible damage to the pipeline.

4. Environmental Permitting. In most countries, this requirement is on top of the list as the most critical issue toaddress in order to get a go signal for the pipeline route. This involves preparation of an Environmental ImpactAssessment (EIA) study that includes studies on risk to human health, community, proximity to inhabited orprotected areas, significant alteration to touristic or scenic value, adverse effects on renewable naturalresources and alteration of monuments and sites with anthropological, archeological and historical value. (TheChilean Environmental Framework Law ("the Law") was adopted in March, 1994). The process for securingan Environmental Permit can range from a minimum of six months to 3 years.

5. Land Rights and Acquisition. If not properly managed the Land Acquisition can easily become the mostproblematic and expensive part of the project. This is especially true if the option of rerouting is noteconomically feasible. The land acquisition process involves numerous public information campaignaddressing issues such as social impact to communities, operational hazards, and rights of ingress and egressfor maintenance and operations.

3. Stages of Route Selection

Route selection is a concerted effort between a routing engineer, surveyor, environmental planner, designhydraulics engineer, right-of-way (ROW) agent, geotechnical specialist, and construction. No one entity can workindependently in the successive stages of the pipeline project to complete their particular assignments. Figure 1 shows atypical pipeline planning schedule that envelopes the different stages of route selection process engineer (in accordancewith Pipeline Route Selection for Rural and Cross-Country Pipelines, ASCE Manuals and Reports on EngineeringPractice No. 46).

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Figure 1. Sample Pipeline Project Planning Schedule from Concepcion to Construction

In practice, there are 4 commonly known stages of development of the pipeline route selection which aredescribed in the succeeding paragraphs. Each stage advances to a more definitive route reducing topographic map scaleto a more precise scale with narrower corridors.

3.1. Preliminary Route Selection

The initial or preliminary route selection normally involves the study of two or more routes to identify themost economical or operationally feasible one. An economical route is one with the shortest length with a graduallydescending slope. During this phase, the pipeline route may be defined using a map scale between 1:50,000 to1:200,000 at a corridor with between 500 m to 1 km width. A readily available military map or the use of GoogleEarth should be sufficient to make this study with no additional site surveys required. For each selected route, apreliminary hydraulic calculation shall be made to determine required pumping power and pipe sizes. These data are

tabulated for each route selected and a rough capital cost estimate is made. The best route is recommended based on themost economical and easiest to operate pipeline system.

3.2. Route Refinement

This is also known as the Conceptual Study. During this phase, a preliminary site walk down is made by agroup of specialists including the route engineer, construction engineer, geohazard specialist and a hydraulic engineer.The objective of the group is to field identify any possible show stoppers of the selected route prior to requesting forlow level aerial mapping with terrain and geohazard characterization. Topographic survey during this phase should bein the order of 1:10,000 to 1:50,000 with a corridor with between 100 to 500 m width. It is during this phase wherecritical site conditions or special crossings are identified. Also, it is at this phase that the selected route is madedefinitive. The construction CAPEX estimate accuracy during this phase is between +/- 20% and 25%.

3.3. Route DefinitionAt this level, the route is well defined. A more precise survey is made with a scale between 1:5,000 to1:10,000 and a corridor width between 50 m to 100 m. The resulting plan and alignment sheets are utilized to secure all

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necessary permits and right-of-way or land acquisition. During this phase, test pits for soil sampling are made todetermine the soil composition and mechanics, scouring depths and soil stability. Special design considerations aremade for at identified hazardous areas and special crossings. The construction CAPEX accuracy estimate during thisphase is reduced to between +/-15% and 20%.

3.4. Route Optimization

Route optimization involves a definitive marking of the centerline of the pipeline as shown in the alignmentsheets. This allows a more precise estimation by the contractors for construction bidding and installation purposes. Allconstruction details for special crossings are well defined. During this phase, construction project cost estimate isreduced to between 10% and 15%.

4. The Pipeline Project Team

A typical organization of the Pipeline Project Team is shown in Figure 1. It is important to designate aPipeline Route Engineer (PRE) who coordinates all associated work during route selection. The PRE shall reportdirectly to the Project Head or Director and coordinates permitting and clearance requirements with the client.

Figure 2. Typical Pipeline Project Organization Chart

5. Slurry Pipeline

Compared to other industrial long distance pipelines, a unique feature of the slurry pipeline is its strictcompliance to the required pipeline slope. This slope requirement is brought about by the ability to enable restart afterlong shutdown with pipeline full of slurry. The slope restriction is defined by the slurry hydraulics engineer and isdetermined based on the characteristic of the slurry that is being handled. The parameters considered includes thefollowing: slurry rheology, settling rate, angle of repose and angle of slide.

5.1. Slurry Rheology

Slurry rheology is the physical property of fluid under flow condition. Slurries are qualified as non-Newtonianfluids as its flow properties is not described by a single viscosity such that of water, oil or a similar fluid. There are twobasic slurry flow behavior patterns; i.e, homogeneous flow and the heterogeneous flow. For homogeneous flows, solidsare uniformly distributed throughout the pipeline cross-section. The particles are often very fine and the mixture at highconcentrations becomes more viscous and develops non-Newtonian properties. In the case of heterogeneous flows,solids are not uniformly throughotu the pipeline cross-section, and therefore a gradient of concentration exists in thevertical plane. Dunes or sliding beds may form at the bottom of the pip, with the heavier particles at the bottom and thelighter ones in suspension, particularly at the critical deposition velocity. This flow process is common in lowconcentration tailings lines.

Depending upon the type of slurry to be transported, the grade required for the slurry pipeline may becomecritical. For heterogeneous flow slurries, the heavier particles may accumulate at the low points as flow conditions may

Project

Head

Client Project

Coordinator

Project Control EngineeringRoute

EngineerProcurement

Geophysics EnvironmentalSurvey

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not be sufficient to transport these through high points. The accumulated solids could eventually cause pipelineblockage.

5.2. Solids Settling Rate

The solids settling rate is the speed at which solid particles separate from the water medium and drops to thebottom of the pipe. This property will enable hydraulic engineers to predict when solids could become compact andthus be able to predict safe shutdown duration for the pipeline.

5.3. Angle of Repose

The angle of repose is an engineering property of granular materials that enables solids to rest in an angle asdetermined by its friction among particles, cohesion and shape of particles. In short, when a slurry pipeline isshutdown, the solids will have the natural tendency to settle and not slip when resting below its angle of repose. This isan important property as it can predict allowable pipeline slopes.

54. Angle of Slide

Corresponds to the slope measured in degrees of deviation from the horizontal in which loose solids will startto slide. It is similar to the angle of repose, except that the friction is between the wall surface and solids.

Figure 3. Graphical Representation of Angle of Slide and Repose

In general, most slurry pipelines are constructed with a slope of around 6% grade. In some cases, slopes of upto 15% are made but with strict consideration that the succeeding slopes must not be made on a reverse direction. Inturn, they should present a gradual inclination towards the acceptable slope restriction.

6. Cost Impact of Route Selection

In any long distance pipeline project, the cost of the pipeline itself is the controlling cost in the project capital

expenditure (CAPEX). The pipeline commands as much as 70% of the overall CAPEX. It is therefore clear that anyreduction or increase on the pipeline length will have a considerable impact on CAPEX.

To demonstrate the importance of the route selection, an actual project in Chile is presented. Figure 4 showsthe initial route selected for a concentrate pipeline with a total length of 134 km and with a challenging profile thatpresents numerous possible problems with high grade slopes.

A route optimization review was made and an alternative route was considered, showing better constructabilitywith favorable slopes, presenting ease of operation and maintenance. This new route is shown in Figure 5, where thesecondary high point was practically eliminated. The new route has a total length of 116 km which is 18 km shorterthan the initial one. For the elimination of the secondary high point, the pumping head and amount of pump station wasreduced as well.

Angle of Slide

Angle of Repose

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Figure 4. Initially Selected Pipeline Route and Profile, 134 km

Figure 5. Finally Selected Pipeline Route and Profile, 116 km

CONCENTRADUCTO DE HIERRO ATACAMA

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PUNTO ALTO

CANDELARIA

(EST. BBAS.)

BRASS CHILE LTDA

Roger de Flor 2950, Piso 6

Las Condes, Santiago, Chile

Fono: 2-231-5521/Fax: 2-233-0392

TOTORAlILLOTOLEDO

Concentrate Pipeline Initial Profile

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Table 1 below shows the cost comparison between the two routes. As shown, the cost savings in obtaining an

optimized route is $ 23,953,000.00.

Table 1. Route Selection Comparison

Route Length (km) CAPEX (US$)

Initial 133 $ 65,953,000.00Final 116 $ 42,000,000.00

Consequentially for the project, the good integration between the client project coordinator and with the specialists ofthe engineering company specialized in slurry pipeline design and contracted, at the route definition phase to performthe basic engineering allowed the project to go back a couple of stages but resulted in substantial cost savings in theroute selection process and the route was completely redefined before and ease the process of securing environmentalpermits and land rights and acquisition process took place.

The high savings obtained in this project were a result of the shared vision of the client and engineering company thatthe preliminary route selection had to be done again and done properly. One of the most important aspects of thepreliminary route selection is to have a multidisciplinary team look at the whole landscape without pre-conceived

assumptions of where the pipeline should pass through. Route selection is a multifaceted iterative process and whatoptimizes one aspect maybe offset by another. Far too often the best route is overlooked at either because the shortestdistance between the two end points is selected without proper evaluation of the obstacles in between (be themhydraulic, geo-hazard, land rights or environmental in nature) or because the wrong pre-requisites such as closeness toexisting roads or other pipelines are used blindly without proper cost comparison.

7. References

ABULNAGA, B. E. Slurry Systems Handbook, Chapter 1, p. 1-15 to 1-16, 2002.SLATTER, P. T., et al, Yield Stress, Viscosity and Non-Newtonian Turbulent Pipe Flow, p220.ASCE, Pipeline Route Selection for Rural and Cross-Country Pipelines, Practice No. 46, 1998.

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