PFG Building Glass, the Springs-based float glass manufacturer, has invested R1.5 million in a 720kW uninterruptible power supply (UPS) system to ensure critical electrical loads at the factory are maintained in the event of mains power failure or voltage variances (sags or spikes).
The UPS solution, engineered to meet specific PFG requirements, was designed, installed and commissioned by Square One Power Solutions, the UPS specialist in the JSE-listed Square One Solutions Group.
Three APC Silcon Series 400V 3-phase UPS units each rated at 240kW formed the core of the engineered solution. Neill Schreiber, managing director of Square One Power Solutions, says the overriding factor that influenced the system design was PFG's need to overcome voltage variances and power supply interruptions to critical areas of the Springs plant, which processed 3 000 tons of raw materials into sheet glass every week.
"The APC units are configured in parallel redundancy to ensure that PFG's critical electrical loads are catered for under all circumstances. The configuration means that even in the highly unlikely event that one of the UPS units fails, the remaining two will comfortably take up the load."
Schreiber adds that the three battery backup installations have also been configured in parallel redundancy to offer additional security of supply under emergency conditions. If one battery pack fails, the others will share the load and the configuration also allows PFG to lengthen the battery discharge time during a power failure should circumstances - such as a delay in diesel genset backup - require it.
"The purpose-made solution was designed with the highest possible security and availability of power supply in mind, there is a 50kA distribution panel with mains and diesel power input feeders, switchgear catering for input and output for the UPS system as well as output distribution circuits for the plant's critical loads."
All of the circuit breakers are rackable and should a circuit breaker fail, it can be replaced on a pull out, push in basis without having to take the system off line.
A challenging aspect of the system installation, according to Schreiber, was that the room allocated to house the UPS units, distribution panel and battery packs was located 6m above the control room in the production area. The three units, battery packs, distribution panel and ancillary equipment had to be hoisted into place and manoeuvred into the room via a suspended walkway above the production line.
"As the room is in an area where the glassmaking process gives off heat, an air conditioning system was fitted to provide the optimum operating environment. The UPS units are intelligent and all components of the system interface by software. Bus communication provides automatic load distribution for cost-efficiency as well as battery management and operational power data can be downloaded from the units into a PC or accessed on the unit via the keypad and LCD alpha-numeric display."
PFG Building Glass control engineer Nic Carter said voltage variances and mains supply interruptions had proved costly with loss of production. "Glass making is a continuous process and it is difficult and time-consuming to make the plant ready for start-up after production has been halted. These were major considerations in our decision to install a comprehensive UPS system. We already had a UPS unit on site but it was unable to cope - the new system is four times the size."
Carter says PFG's selection criteria for the UPS system were centred around the technical competence and experience of the Square One Power Solutions team, its local support capability and the APC UPS product technology and international track record.
He adds that the UPS protects a variety of factory-critical loads, including the tin "bath" where some 140 tons of molten tin in a large container provides a platform for molten glass emerging from the furnace to float on, and the adjacent "Lehr" process line where the temperature of the cooling glass is controlled to ensure desired quality and strength properties of the finished product.
"With the new UPS system we are able to run all critical equipment for 30 minutes if there is a mains power failure. The system has been tested successfully at 120% of factory load so we have some latitude. In normal circumstances the diesel gensets will supply power to the UPS system within 20 seconds of mains failure but if there is a genset problem, battery power will give us 30 minutes to rectify it."
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Square One Power Solutions is a national UPS company, an APC High Power Partner and a member of the JSE-listed Square One Solutions Group. It provides power solutions for the SOHO, PCA and SME network environment, telecommunications, medical, security, lighting and general industry as well as major corporations and government.
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