Client: Mpact Operations (Ltd)
• LNW Consulting Engineers & Project Managers (Pty) Ltd
• MSJ Geotechnical Consulting Services (Pty) Ltd
• GES Consult GmbH
• Crossfire (Pty) Ltd
• Leomat Construction (Pty) Ltd
• Franki Africa
• Terex MHPS (Pty) Ltd
• Raumaster Paper OY
Construction of the first automated paper mill and storage handling facility in the southern hemisphere in South Africa.
The project comprised of the design, engineering and construction of the fully automated paper reel storage facility, roll transportation system, inbound and outbound traffic logistics, vehicle weighing stations and all related mill services such as power, water, air, steam, etc. to accommodate the project.
The paper reel storage facility further included the following:
• A reel handling system from the paper machine
• A fully automated electric overhead crane handling system
• A logistics load out system
• A fire prevention water sprinkler system
• A truck parking facility entrance and internal roads
• A weigh bridge facility
1. Project Background
2. Requirements of the Paper Roll Storage Facility
3. Engineering and Engineering Challenges regarding the Design and Construction of the Paper Reel Storage Facility
3.1 Engineering Challenges
6. Completion of the Project
7. Project Footnotes
Phase 2 of Project Khulisa 2.15 mill expansion project at MPACT’s Felixton Mill in Empangeni could be described as an “open heart surgery” upgrade project to an existing industrial paper mill facility which required the rebuild and conversion of the process facility to produce paper from recycled paper material instead of bagasse previously supplied to Mpact from the neighbouring sugar mill.
The R 765 million expansion project to MPACT’s Felixton Mill was planned for execution in two phases with the first phase successfully completed in June 2015. Phase two required approximately two thirds of the funding and was scheduled for completion in December 2017. At which time the mill would produce paper from 100% recycled fibre instead of bagasse, increasing its current capacity by 60 000t/annum to 215 000t/annum.
As with any Brownfield Project within an existing operational industrial facility, the project had to be executed within a specific limited duration time frame which meant that almost all of the required rebuild construction activities had to be executed simultaneously, requiring in depth upfront engineering and comprehensive detailed planning of all construction and installation activities to ensure successful implementation.
The work required in Phase 2 of the project was split into three portions which represented the three plant areas requiring upgrade and rebuild:
Mpact Operations (Ltd) appointed LNW Consulting Engineers and Project Managers (Pty) Ltd as civil and structural engineers in September 2016 to assist with the design and implementation of Phase 2 of Project Khulisa 2.15, which also included the design and construction of a fully automated paper reel storage facility which was required to accommodate the storage and handling of product in a fully automated manner.
The fully automated paper reel storage facility being the first to be constructed in the Southern Hemisphere required a building approximately 25 meters high at the roof apex, covering an area of 3000 square meters with an under-cover truck loading bay of 1800 square meters which could accommodate 15 000 tonnes of paper or approximately 11 250 paper reels at 1.3m diameter being vertically stacked and retrieved onto each other up to a height of 15 meters by two fully automated overhead cranes each weighing approximately 40 tonnes fitted with a vacuum lifting device with a lifting capacity of 3.3 tonnes and an automated reel handling system transporting paper reels from the paper machine to the facility as well as from the storage facility to an out loading area also forming part of the requirement as well as the necessary MCC rooms, electrical and fire protection installations, roads, truck parking and load bridge installations.
3.1 Engineering Challenges
One of the first engineering challenges which was identified was that the area allocated for the paper reel storage facility previously accommodated the old bagasse yard which was originally constructed on an old waste disposal site situated on the edge of the uMhlathuze river flood plain which is known for its very poor founding abilities. This was confirmed in the geotechnical investigation report executed by MSJ Geotechnical Consulting Services (Pty) Ltd.
The next major challenge was to design a building of such magnitude with very little tolerance for settlement of its foundations and a floor slab which could adversely impact on the stacking of the paper reels as well as the operations of the fully automated overhead cranes. Sensitivity surrounding the accuracy of the stacking and retrieval of the paper reels further meant that the construction of the storage facility’s floor as well as the structural steel building frame and crane gantry installation had to be of extreme accuracy which in itself demanded a high level of quality control which was part of LNW’s responsibility.
The OEM of the cranes required two key tolerances to be achieved for the storage facility floor and the crane gantry beam and rail installations.
Construction of the storage facility floor had to conform to the tolerances specified in DIN 18202 and the flatness of the floor in accordance with Group H, Column 3 of DIN 18202 which equates to a deviance in flatness tolerance of a maximum of 3mm per square meter.
The accuracy of the installation of the crane gantry beams and rails had to conform to DIN 4132 and VDI 3576 Rev. 2008, Class 1 and 2 which proved to be challenging to achieve.
A further challenge presented itself in the demolition of the overhead bagasse handling system which was made up from an overhead (±16m above NGL) launder system supported on a lattice gantry frame and large pylon type concrete columns as well as portions of the bagasse yard concrete floor slab which was constructed to accommodate the drainage of process and dirty stormwater into a dedicated process water recycling dam. So apart from the fact that the LNW engineering team had to reconsider and re-engineer the stormwater drainage of the large redundant bagasse yard (which can be seen on the photos) in conjunction with the required roadworks to accommodate the heavy vehicle logistics to both the new starch plant and the paper reel storage facility, the team further sat with the problem of the demolition of steel and concrete structures and the disposal thereof which included large volumes of reinforced concrete.
The capacity increase of the plant further increased the logistical requirements of the vehicles entering the plant to deliver waste paper to the new waste paper yard as well as vehicles collecting paper reels from the paper reel storage facility. As the existing internal roads proved to be narrow with overhead limitations, a new entrance/exit with weighbridge facilities and access road were required.
Upon receipt of the results of the geotechnical investigation (of the site identified for the storage facility) confirming poor founding conditions compromising of thick layers of alluvial residual clays unsuitable for the reuse in roads and layer works only two founding options presented itself for consideration, the one being that the storage facility be founded on piles drilled/driven into the cretaceous bedrock and the other a basal reinforcement option which proved to be far more economical to install depending if the effects of the global settlements caused by the anticipated floor loads could somehow be countered.
LNW chose the latter and approached Franki Africa to execute an assessment of the settlement effect of the anticipated structure on a vibro-stone column densified soil improved underlying founding platform system which was recommended by Franki Africa to support the storage facility floor and through which mortar piles could be socketed into the much stiffer deeper underlying soils to support the building’s steel structure.
Although the outcome of the investigation indicated a relatively low level of expected settlement of the anticipated engineered foundation solution, the comparison of its envisaged cost with that of a complete piled support structure for the floor and the building, the decision was made by the LNW design team to pursue this foundation solution for implementation.
So to recap it meant that the actual building structure (comprising the column footings, wall foundations and the steel structure) was meant to be founded on a mortar pile, pile cap and ground beam support structure and the building floor on a vibro-stone column densified underlying soil improved founding platform designed in such a manner to distribute its floor loading without causing additional excessive settlement of the underlaying soil improved support platform.
The drawing hereunder shows the floor layout of the building and the positions of the vibro-stone columns.
Figure 1 – Pile and Vibro-stone column layout
The above soil improvement systems recommended by Franki Africa at the time was a relatively newly developed technology and only used successfully on one or two sites previously in South Africa. This reduced the risk of experimenting with unproven/untested newly developed technology on a fast track limited down time project program to the possible detriment of the Client.
Figure 2 – Settlement Analysis Model
From the above settlement analysis model based on the engineered layer of the soil improved platform, settlement between 25mm (on the centre of the floor) and 15mm (on the edges of the floor) was expected for the worst case loading conditions which would occur if the paper reel storage facility was fully laden to 100% of its design capacity which would very seldom be the case and if so only for a limited periods.
From the aforesaid information, the decision was taken to design the floor as a complete jointless post tensioned raft floor slab with an integral outer edge ring beam for post tensioning purposes.
The earthworks and foundation requirements to the lean structure differed considerably from that of the storage facility as the lean to only had to provide under roof loading of heavy vehicles and was dealt with by means of conventional road layer works as proposed in the geotechnical report.
The engineering solution to dispose of the large volumes of demolished reinforced concrete was addressed by making use of a mobile crushing plant on site which allowed the LNW team to regrade the crushed material which was in turn blended with dump rock to provide a working floor for the layer works to the waste paper yard which contributed to a considerable cost saving on the project.
The storage facility structure comprised of a structural steel frame 25m high supporting 2 fully automated paper reel handling cranes weighing 40 tonnes each with a safe working capacity of 3.3 tonnes. The structure was designed to typical high wind load coastal conditions considering the stringent crane gantry tolerances specified by Terex.
Redesign of the bagasse yard drainage in conjunction with the newly required roads and entrances meant that the old dirty stormwater and process water drainage system had to be amended to now accommodate a clean stormwater drainage system.
Poor underlying soils under the old bagasse yard slab, necessitated the use of the slab as subgrade road bed for the new truck parking facility and newly required internal road. This decision constituted the roads to be constructed by making use of some conventional road layer works and mass concrete fill to achieve the required road alignment.
The new entrance roadway was constructed to accommodate the increased heavy vehicle traffic to the waste paper yard and the paper reel storage facility.
As LNW Consulting Engineers and Project Managers (Pty) Ltd is an ISO 9001:2015 quality accredited company, all design work executed by our Randburg office was subsequently peer reviewed by our Empangeni office (and/or vice versa) as required by our in-house quality assurance procedures.
All design work was further done in 3D software to allow the easy development of rebar schedules and structural steel shop detail drawings. Steel frame analysis was done in Prokon, STAAD and ROBOT with an emphasis on the design of the building structure as economical as possible in order to optimise costs.
LNW assisted MPACT in calling on reputable construction companies to pre-qualify in order to be allowed to tender for the construction of the paper reel storage facility which all formed part of an overall risk mitigation and management plan.
All tenders were evaluated upon which time intense bid clarifications were done with all tenderers to ensure that any possible ambiguity was removed and all rate make-ups were well understood in all bids.
Upon adjudication and award of the contracts, value management sessions were held with the main contractors and their sub-contractors to further refine the scopes of work to correspond exactly with the various work method statements in line with respective pricing schedules to rule out any possible misunderstanding which could result in unnecessary frivolous claims.
In this instance a contract was concluded with Leomat Construction from Richards Bay whom in turn included Avellini Brothers (Structural Steel Sub-Contractor), Safintra (Roof Cladding Systems) and Concrete Laser Flooring (Specialist Concrete Flooring Sub-Contractor) as part of their team.
A separate contract was concluded with Franki Africa for ground improvement and piling.
Construction began in December 2016 with the paper reel storage facility which was completed and handed over to the Client in December 2017 for commissioning.
The original tender value of the successful tenderers at the time of tendering amounted to R48.9million (Excl. VAT) and was subsequently reduced to R 43.3 million after bid clarifications and value management sessions.
Upon completion the contract value with additional works amounted to R 46.2 million (Excl. VAT).
The contract was thus successfully completed within time and budget to allow the overall successful commissioning of the first automated paper mill and reel storage facility in the Southern Hemisphere in South Africa.
Numerous floor slabs had to be strengthened and penetrated to accommodate the equipment.
Structural modifications to structures to accommodate a new Starch plant and storage tank facility also formed part of the appointment.
Before Project Khulisa 2.15
After Project Khulisa 2.15