By Dusan Stefanov (ODA Design and Drafting) and Levi Bands (Service First GP)
A complete new section of this site and HVAC plant (Phase 2) was required to accommodate an increased demand in production.
The cooling towers (back view) as seen from the street. Image credit: © RACA Journal | Benjamin Brits
This project, comprising a location for the manufacturing of bumpers and associated products for a large global vehicle manufacturer, is located at the Tshwane automotive special economic zone in Rosslyn, Pretoria.
The same team was involved in Phase 1 of this manufacturing plant, that took place back in 2011, and then 10 years later were fortunate enough to again be a part of the expansion and major plant upgrade.
The project conception and planning started in early 2019. Breaking ground took place in March of 2021 and the project was completed in January 2022 for wet trials. It was expected at the time of publishing that the project would be handed over fully to the customer by July 2022.
“It was decided that dual cooling circuits would be implemented.”
Design specifications/client brief of the project
The design called for a water-cooled chilled water plant to supply the paint shop air handling unit (AHU) and moulding machine section – also known as the Chilled Circulating water (CCW) network and integrated moulding mechine (IMM) network. The large custom AHU was not part of the scope of the HVAC plant installation and was provided by another international partner.
The CCW is the chilled-water supply to the AHU section and moulding machine cooling requirement. The IMM network feeds the section of the plant that uses chill water from the CCW network as well as the cooling tower water network.
The HVAC system and installation
After analysing the type of moulding presses and their cooling requirements, as well as their respective placement within the production facility, it was decided that dual cooling circuits would be implemented.
Two-of water cooled chillers and primary pumps would provide 7°C/12°C water direct to the paint shop AHU, while temperature requirements (14°C/19°C) for the primary side of the moulding machines would be taken care of via a dedicated heat exchanger and secondary pumps. All of the moulding presses have two independent circuits (for the hydraulics and moulding) on them. These circuits needed to be cooled down with the different temperature regimes in accordance with specifications from the machines manufacturers.
Two-of closed-circuit cooling towers are utilised at the site to cool the chillers and secondary side of the moulding machines. Two separate sets of condenser water pumps were used for these circuits.
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Difficulty in meeting specification/Solving the challenges
The client’s brief was to provide equipment that was efficient not only under full load conditions but also in a partial load operation. This was due to the fact that the plant’s internal and external loads vary significantly throughout the year. Therefore, it was important to select the correct equipment which would be able to accommodate multiple conditions while maintaining optimum efficiency.
Implementation wise, the single biggest challenge was to fit the chillers and pumps within the pre-determined, and very limited size of an enclosed plantroom. This is where the design advantages from ODA Design and Drafting (ODA) came to the fore. This was successfully navigated by using Revit modelling, investigating various scenarios, and finally optimising the position of each and every pipe in order to accommodate the required equipment into the confined space.
“The detailed BoQ eliminated most of the ordering and claiming headaches.”
After completing the overall system Revit model, ODA also provided all the parties with a complete bill of quantity (BoQ). This was one of the sites used in the implementation of their extensive custom-development of this software platform and their achievement of very high accuracy outcomes for BoQ generation (97%).
With plan views, sections and details derived from the Revit model that was provided to the pipe installers, it helped shorten the installation time by an estimated 30%. Also the detailed BoQ eliminated most of the ordering and claiming headaches typical of projects. Each project element had a monetary value and an attribute called “Claim No” assigned to it. That enabled the team to do the “filtering” of elements according to the claim number. Monetary value of the claim would also be calculated automatically.
Project products and selection criteria
The revit model of the MSSL HVAC plant room – front view. Image credit: ODA Design and Drafting
The revit model of the MSSL HVAC plant room – rear view. Image credit: ODA Design and Drafting
A revit model of the MSSL pumps – 3D view. Image credit: ODA Design and Drafting
The below products listed formed part of this project. These items were selected by consultations with the Service First GP and MSSL teams. MSSL is an international project management company that was contracted to deliver the “turn-key” manufacturing facilities for the vehicle manufacturer.
- 2 x 2000kW Trane water-cooled chillers
- 2 x 5000kW Evapco closed-circuit cooling towers
- 10 x Armstrong circulating pumps
- 4 x InfinityFlo make up water pumps
- 1 x Fiorini brazed plate heat exchanger
After the consultation with the client, two different types of chillers were determined to best suit the requirements. One screw type chiller was selected in order to cater for low-to-mid load conditions due to its high efficiency during partial cooling loads. The other selection was a centrifugal-type chiller which will operate when the load requirement is 80% and higher. This choice formed part of the proposal due to this chiller’s high full-load efficiency.
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Overall the system would be well suited to all levels of production capacity as manufacturing was ramped up over time.
The high efficiency requirements imposed by client also stood behind the selection of Armstrong circulating pumps. The fundamental difference in the Armstrong Design Envelop Pumps when used in an HVAC systems is the unique controller which incorporates embedded intelligence – thus eliminating the requirement for adding any variable speed drives (VSDs).
The pump requires no external input from a pressure differential sensor or a flow meter and completely does away with this requirement for the entire system, resulting in additional savings. The pump has its multi-speed curve and efficiencies pre-programmed into the controller and the embedded intelligence allows the pump to run sensorless, reacting to changes in the system instantaneously.
Furthermore, the pump displays pressure and flow rates on the controller and can feed this information directly through to the building management system (BMS) via BACnet without any other interface. The pump can also be connected directly to the chiller via BACnet.
Impact of the system on electrical usage
The impact on electricity demand is minimal due to the design of the major HVAC equipment. All chillers, pumps and cooling towers were selected at the best coefficient of performance (COP) and “VSD operation” is already incorporated with the pump equipment to achieve high part load operation.
Elements that make this project special/unique
The chillers use natural HFO refrigerant thus reducing the global warming potential of the plant. The refrigerant used is R514A which has an ODP of 2 which is among the lowest in the industry. The use of the intelligent Armstrong circulating pumps in addition increases operational efficiency. These pumps can be easily incorporated into the cooling system, as they come with their own additive control logic. This software predicts the plant’s requirements at any given time, resulting in saving energy and running costs.
“The impact on electricity demand is minimal due to the design of the major HVAC equipment.”
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