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Heating, cooling, ventilation and air conditioning
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Mechanical Technology — February 2014
29
Chiller retrofits increase
capacity and efficiency
W
ith the help of Johnson Controls, Har-
mony Gold Mining Company’s Tshe-
pong mine in the Free State has retrofitted
its 25‑year old chillers with York equipment.
Tshepong is one of Harmony’s largest op-
erations; it has a single vertical shaft extending
to a depth of 2 161 metres. The mine under-
takes conventional undercut mining, where
ore is transported to the Harmony 1 plant,
23 kilometres away. The three chillers at the
Tshepong surface plant deliver 10,2 MW of
cooling each, supplying 300
ℓ
/s of water at
3,0°C to cool the underground workings of
the shaft.
Tom Smith, chief operating officer at
Harmony Gold South Africa explains, “Our
25-year old chillers were nearing end-of-life
and we faced a number of challenges. The
equipment was not functioning efficiently,
parts were hard to get, and we were experi-
encing a lot of breakdowns.”
Neil Cameron, general manager of Johnson
Controls Building Efficiency Africa explains: “It
is imperative that the mine gets the necessary
cooling capacity and that the solution selected
is reliable and well supported to minimise risk
going forward. With a well-established pres-
ence in South Africa, a good track record in the
mining industry, experienced and highly skilled
resources, and proven solutions, Johnson
Controls’ proposal to retrofit the chillers with
York equipment was selected.”
The job entailed the removal of the
existing compressor and drivetrain (speed
increaser and motor) on each chiller. These
were replaced with a new compressor with
an integral speed increaser and a two-pole
motor designed for the new R134a refriger-
ant. Refrigerant pipe work had to be altered
to accommodate the new compressor and
the system had to be cleaned to remove all
traces of mineral oil. A York K7 single-stage
centrifugal compressor that incorporates the
latest state-of-the-art technology for better
efficiency and cost savings was selected.
“The retrofit has improved cooling perfor-
mance measurably and made a major dif-
ference to the teams working underground,
improving working conditions and productivity.
In addition, with more efficient motors we
are achieving energy savings. Due to some of
the plants being switched off during winter,
the actual impact will only be realised in
summer, but calculated savings suggest that
8 884 MWh will be saved in each plant,”
predicts Smith.
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According to Eben Owen, en-
terprise and solutions manager for
South Africa at Schneider Electric,
this feature addresses environmental
concerns associated with some refrig-
erant or water-based systems. “Both
of the economiser cooling strategies
employed by EcoBreeze maximise
localised climatic conditions to en-
sure the most efficient and effective
form of cooling throughout the year,”
he says. “In certain climates, some
economiser modes can save over 70%
in annual cooling system energy costs,
corresponding to over 15% reduction
in annual power usage effectiveness
(PUE). In South Africa, EcoBreeze
has the ability to provide up to 90%
of annual cooling for free, due to the
country’s climate.”
EcoBreeze’s modular design also
allows the unit to be adapted to
any future cooling needs of the data
centre. The system is available in
individual 50 kW modules that can
be grouped in four (200 kW) or eight
(400 kW) modules of sensible cool-
ing. This modular, scalable approach
enables customers to purchase only
what they need to meet their current
cooling requirements, while giving
them the ability to increase their cool-
ing capacity at any time as their data
centre grows. Modularity also provides
redundancy at the frame level and
ensures availability of the system dur-
ing maintenance and service intervals.
Power, water, airflow distribution and
communication connections are also
centralised to the frame, simplifying
installation requirements.
Additionally, as the unit is located
outside the perimeter of the data centre
or on the roof, the EcoBreeze takes up
zero whitespace, enabling IT manag-
ers to utilise space in the data centre
to increase capacity without having
to allocate space for cooling units.
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matic conveying of bulk materials and
homogenising of cement,” he continues.
Other notable features of Aerzen
Delta Blower Generation 5 include:
considerable sound reduction; easy
operation and maintenance from the
front of the machine; and space-saving
side-by-side installation. Furthermore,
there is no absorption material in the
discharge silencer, resulting in zero
contamination of the system.
All Generation 5 blowers make use
of a mechanical fan, as opposed to an
electric fan, in order to ventilate the
acoustic hood, which ultimately ensures
further energy cost savings and Stubel
cites the patented internal pulsation
reduction as another benefit.
“Roots blowers produce sound pulsa-
tions that are carried over into the piping
system. Apart from being extremely loud,
these sound waves produce vibrations,
which can eventually lead to a dam-
aged piping system. Aerzen’s patented
integrated pulsation reduction system
reduces the pulsations produced by the
rotors because of channels cast into the
cylinder housing on the discharge side.
These channels allow for a small stream
of gas to escape back into the conveying
chamber. This effectively reduces pulsa-
tions, lowering the machine noise and
vibrations,” he explains.
Preventative maintenance measures
are becoming increasingly important:
“Breakdowns are highly damaging to
businesses, and we advise our custom-
ers to regularly perform the necessary
checks on their machines. To prevent
any breakdowns, our technicians can
perform condition audits and advise
customers on our maintenance contracts
to keep their equipment in peak running
condition. In case of breakdowns or
repairs, a rental pool of major machine
types is available.
“We have observed that purchasing
decisions are still based more on initial
cost savings and that the benefits of
new energy efficient blower and com-
pressor technologies and premium effi-
ciency motors are sacrificed. In order to
overcome this challenge, Airgas is com-
mitted to promoting energy efficiency by
educating the market on the long-term
environmental and capital savings of
new energy efficient technology, which
far outweigh the initial cost difference.
“Following success from our base
in South Africa, I am positive about
the future outlook for Airgas. Our main
industry is currently mining, milling and
wastewater treatment, however I am
confident that we can break into new
markets in Africa, particularly natural
gas and renewables such as biogas,
which holds potential for substantial
future growth,” he concludes.
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