African Fusion March 2015

AFRICAN FUSION

March 2015

Wind tower fabrication

rainedat theNelsonMandelaMet-

ropolitan University (NMMU) in

Port Elizabeth, Jauka joined DCD

Wind Towers in November 2013 at the

starting point of commercial production.

“I did a degree in industrial engineering

and, after working at a local Goodyear

facility for a few years, I joined DCD to

improve the production efficiency of the

wind tower fabrication process. To re-

main competitive, we need to find ways

to cut away non value adding operations

and to promote those activities that are

directly incorporated into theprice of our

product,” he tells

African Fusion.

“The core value adding activity of

this facility is welding, and we employ

mainlyGMAW, FCAWandsemi-automatic

submerged arc welding,” Jauka contin-

ues. “But my experience is production,

so I am learning about welding all the

time,” he adds.

Describing the particular require-

ments for wind tower manufacturing,

he says that the key productivity goal is

to balance each part of the production

line so that the fabrication of each wind

tower segment proceeds steadily and

efficiently through the plant, without

causing delays or inactivity further into

the process.

The plate for the first commercial

can was cut on Saturday February 15,

2014, for a Vestas V112, 3,075 kW wind

turbine destined for InnoWind’s Grass

Ridge project 25 km South of PE. DCD

Wind Towers has now completed and

delivered five three-section towers for

this project, which was commissioned

during January this year. In total, this

plant has 20 turbines capable of produc-

ing 61.5 MW which, at a capacity factor

of 25%, is equivalent to 134.7 GWh of

power per year – enough to supply the

basic annual needs of up to 40 000 South

African households.

“Our current work also involves

Vestas turbines for a secondwindproject

dubbed ‘Chaba’.” The requirement is

for seven towers split into 21 separate

sections, which will support turbines

supplying 21 MW of power to the Great

Kei municipality at Komga, up near the

Kei River north of East London. The

first turbine is due to be operational in

July 2015, with the facility reaching full

capacity in September. For this project,

DCD Wind Towers will locally build all of

the wind towers.

DCD’s fabrication process, accord-

ing to Jauka involves fabricating three

structural section for each tower, a top

section, a middle section and a base

section. Each of these is flanged so that

the 84 mtowers can be erected onsite by

bolting them together. Each individual

section is made by welding together a

series of cans, which vary in diameter

and plate thickness – 5.0 m in diameter

and 38mm for a typical base section and

3,5 to 4,0mand 16mm thickness for top

sections. “Each section consists of 9, 10

to 11 cans, most of which are tapered,

so fabrication has to be done in a strict

sequence,” he explains.

Four growing lines

The concept being employed to achieve

production and cost efficiency is ‘grow’

each tower section, can by can, on a

growing line. “We have four parallel

growing lines at this facility, which all

need to be busy and balanced for maxi-

mum output capacity and efficiency,”

says Jauka. “For each line, the idea is

that we cut, roll and seal a can, then we

join that can to the previously completed

one. So we join and grow, join and grow

until the tower is the required length.

Thenwe add the end flange. But balanc-

ing the work on the growing lines is also

important. Fabricating bottomsections,

for example, takes up 45% of the total

welding time, because of the thicker

section plate being welded particularly

on the threebottomsectionswith38mm

plate thicknesses,” he tells

AfricanFusion.

“At any one time in the plant, we aim

tohave one canbeing joined to the tower

section in one of the lines, a can-to can-

fit-up being completed on the second

line, can rolling on the third line and

plate cutting for the fourth,” he notes.

At the fabrication starting point a

plate is put through a wheel abrator to

take off the rough scale. “The abrator

blasts grit onto both sides of plate as it

enters the facility. From there, a three

headed CNC-controlled ESAB oxyfuel

cutting system cuts the plate to size,

while simultaneously bevelling the

edges for welding. Due to the different

conical shapes of each can in a segment,

each sequential can has a different size,

so automatic control of this process

is essential and each can has its own

unique identifier that is generated be-

fore the plate enters the facility,” Jauka

explains.

The cut plate is then taken toa cham-

fering table to polish and clean the bevel

and take off the dross. “At this stage we

have our first quality hold point. The

quality controller checks that the plate

is dimensionally accurate for the specific

can and tower section being fabricated,

to within around 1.0 mm of tolerance.

If okay, he places a green sticker on it,

but the plate will remain at the holding

DCD Wind Towers was set up in March 2013 and be-

gan producing tower sections later that year.

African

Fusion

visits the company’s fabrication facilities in

the Coega industrial development zone (IDZ) and

talks to productionmanager, Leonard Jauka, about

its processes and capabilities.

Wind Tower fabrication:

the DCD way

Wind Towers’ production manager, Leonard Jauka.