The Civil Engineering Contractor May 2018 | Page 42

SUPPLY CHAIN NEWS
Sizing transformers
higher current,” he says. “Users can achieve a more cost-
effective solution in many cases by considering a step-up,
step-down configuration, where the voltage is increased to
facilitate longer distances, then reduced to the requirement of
the equipment at its point of location.”
A range of factors need to be considered when correctly sizing
a transformer for optimal performance in any application,
according to Ronaldo Bertoldi, engineering manager at WEG
Transformers Africa (WTA).
“Sizing a transformer for a particular application can be done
using a simple equation, but the selection process requires
many other factors to be taken into account,” says Bertoldi.
“Determining the right transformer for the job requires
an in-depth assessment of the conditions under which the
transformer will operate.”
He emphasises the difference between the full load current
required by an application, and the start-up current if there is
a direct online starting process. If the motor is initiated by a
direct online start, this part of the operation could require a
much higher current than when it is running.
Bertoldi also points out the significance of the distance
between the source of the power and the equipment consuming
the electricity, as will be a voltage drop that will affect the
sizing of the transformer.
“Transmitting low voltage over long distances can also be
more expensive due to the thicker cables required by the
The WTA mini substation production line.
Liners designed to last
40 - CEC May 2018
supply structures. CPF liners also minimise the penetration of
graffiti media, making it easy to remove from a surface.
Formtex is designed for tensioned, glued, or self-adhesive
mounting to vertical or inclined surfaces. Once Formtex
is attached, concrete casting is performed as usual. These
liners can easily be removed from the concrete during
formwork striking.
Fibertex Controlled Permeability Formwork (CPF) liners are
designed and manufactured for concrete surface enhancement
in diverse applications, including highly aggressive
environments.
Typical applications of Fibertex Formtex® CPF liners are
in drinking water tanks, sewage and water treatment plants,
settlement tanks, container terminals, bridges and tunnels,
marine structures, as well as dams and sluices.
Formtex is a two-layer CPF liner, consisting of a drainage
layer that allows water and air to escape and a filter layer with
a pore size designed to retain cement particles. When surplus
water and air is drained from the surface of the freshly poured
concrete during compaction, the water/cement (w/c) ratio
in the concrete cover is reduced. This results in a denser and
stronger concrete, with a blemish-free surface.
Formtex also reduces the formation of blowholes and other
blemishes on the concrete surface that normally require
extensive deburring after the formwork is removed. The
smooth, dense, and strong concrete cover is dust-free and
because there are no release agents, it is an ideal prepared base
for further surface treatment or coatings.
“The main functions of these robust geosynthetic materials
are to improve the durability of a concrete structure, to
extend its service life, and reduce maintenance costs,” explains
Clive Hitchcock, CEO of Fibertex SA.
Formtex CPF liners, which reduce micro-bacterial growth,
are a highly efficient alternative to slip agents for freshwater
Formtex CPF liners reduce micro-bacterial
growth and are an efficient alternative to slip
agents for freshwater supply structures.