Delivery of 3 149 tonne ABB Transformers to Songo, Mozambique

Out of Africa

Located on the southeast coast of Africa and spanning over 300,000 square miles, Mozambique is comparable in size to Turkey. Its southern neighbours are Swaziland and South Africa while Zimbabwe lays to the west. Zambia and Malawi are to the northwest. Tanzania is to the north and the Indian Ocean to the east. A beautiful country, rich in wildlife and stunning landscapes, it was colonized by Portugal from 1505 and gained independence in 1975.

Two years after independence the country descended into a civil war which lasted until 1992. Since the 1994 elections the country has remained stable and its GDP growth is amongst the highest in the world. Large natural gas reserves were discovered in 2012 so the countries future is looking bright (experts estimate it will become the seventh largest gas producer in the world). It was the setting for the multi Oscar nominated film Blood Diamond, starring Leonardo DiCaprio and Djimon Hounsou.

The river Zambezi is the fourth-longest river in Africa. 2,574-kilometres long, the river rises in Zambia and flows through eastern Angola, along the eastern border of Namibia and the northern border of Botswana, then along the border between Zambia and Zimbabwe from where it crosses Mozambique to empty into the Indian Ocean. Its most famous feature is Victoria Falls. The river is frequently interrupted by white water rapids and so has never been an important long-distance transport route.

Many people recognized the potential of the Zambezi, including the British explorer David Livingstone. The narrow ‘white water’ filled gorge ‘Kebrabassa’ thwarted his Zambezi Expedition of 1858. Translated ‘Kebrabassa’ means “where the work cannot go on”, because of the unpassable rapids. More recently it became known as Cahora Bassa.

Travel and transport along the Zambezi is irregular and difficult. It is often easier to travel by canoe along the river instead of the bad roads which are regularly submerged in flood waters. Many villages along the Zambesi are only accessible by river.

The Zambezi provides two main sources of hydroelectric power: the Kariba Dam which is constructed on the border between Zambia and Zimbabwe; and Mozambique’s Cahora Bassa Dam, which provides power to both Mozambique and South Africa.

Starting as a joint $515 million project (USD$3.3 billion today) between the Portuguese and South African Governments in the late 1960’s, the Cahora Bassa Gorge was theoretically ideal for a hydro-electrical scheme. However, practical issues trumped theory due to endless political arguments and because the biggest hydro electrical dam in Southern Africa was built in an inaccessible site, on a river infamous for violent and unpredictable floods.

Blistering African heat, torrential rain, rampant diseases such as bilharzia, malaria and yellow fever tormented construction workers and created a continual shortage of skilled labour. In addition to nature, workers were in mortal danger as the dam site was attacked by insurgents in repeated attempts to sabotage the project.

Despite all these problems, the river was dammed in 1974 with a double curved arch wall 171 metres high by 303 metres wide. The dam is 23 metres thick at its base and 4 metres thick at the crown. It has 8 radial floodgates and a surface spillway with a total discharge capacity of 14,000 m³/s. It possesses an underground power station, on the south bank, with five generator groups, each of 415 MW, and a maximum flow through the turbines of 2,250 m³/s.

The new enclosure formed the Cahora Bassa Lake, Africa's fourth-largest artificial lake at 250 kilometres long and 38 kilometres wide flooding an area of 2,700 square kilometres with an average depth of 21 metres. The lake contains fifty two trillion cubic meters of water.

As man-made enterprises go, it was a huge undertaking and in 1974 it was the second biggest hydro electrical station in the world.

The Mozambican surface rectifier Songo station is 6 kilometres away, converting the 220kV AC to 533kV DC. The power is then transmitted to the Apollo substation near Pretoria, South Africa via two mono polar lines where it is inverted to 275kV AC and connected to the ESKOM South African grid. The power line uses 7000 towers, each 40m high and 1414km of steel core aluminium conductor. 900 km of the power lines are in Mozambique.

Before 2007 the dam was operated by Hidroeléctrica de Cahora Bassa (HCB) and jointly owned by Mozambique, with an 18% equity stake, and Portugal, with the remaining 82%. On November 27, 2007 Mozambique assumed control of the dam when Portugal sold most of its 82% holding. The sale had followed years of haggling between Portugal and Mozambique.

Mozambican President Armando Guebuza, speaking in Songo of the new ownership of HCB, marked the moment as "a second independence to Mozambique". He added "Mozambicans have won an important battle towards their well-being."

The Cahora Bassa hydro-electric complex is immensely important to the Mozambique economy and contributes USD$150 million per year towards the country's GDP, mainly through power sales to South Africa and Zimbabwe. It plays a major role for the development of Mozambique and the Southern African Development Community region.

Power interruptions, age and suffering degradation due to the war-induced interruptions, Hidroeléctrica de Cahora Bassa tendered a refurbishment contract for the HVDC converter station at Songo, 6 km from the dam. The remit was to enhance power availability and improve system stability.

ABB won the USD$50 million tender . As contractor they were responsible for engineering, production and installation of the HVDC unit (I.e. three transformers, DC smoothing reactors, arresters and measuring equipment). Instar Projects, the global project forwarder, were appointed project freight forwarders for the sea shipping and on-carriage and were to the site. In turn, Instar contracted specialist hauliers ALE as the heavy lift service provider and local company ARC were responsible for the route clearance and route sections in South Africa and Zimbabwe.

From the get go it was obvious to all involved that this was a challenging operation.

In 2013 an emergency heavy-lift was needed to deliver a replacement primary transformer size 7.8m x 3.45m x 4.25m and weighing 130 tonne, overland from the Apollo substation, Pretoria, RSA to Songo, Cahora Bassa. That lift was the largest since the cessation of the Mozambique civil war in 1992 and involved careful route planning, by-passes and bridge propping.

The Songo 2014 Heavy Lift took the logistics challenge to a new level of complexity.

The Instar project management team were told that the replacement transformers weighed 143 tonnes each. This immediately precluded Instar from taking the shortest route from the Mozambique port, Beira. Whilst only some 600 kilometres from port to site, it would have involved crossing too many bridges that could not support the weights involved.

The weights took the transport practicalities right to the edge of what was physically possible, given the local infrastructure availability. A very accurate and certified weight was requested.

The ABB replacement transformers weighed 149 tonnes.

The Swedish built transformers were transported by charter vessel, a multipurpose heavy lifter equipped with 2 150 tonne lift cranes, the BBC Carolina. At 9600 GVW the ship and crew were well versed in project cargo movements, transporting the outsized loads from Norrköping, Sweden to the African continent. She arrived at Richards Bay port, KawZulu-Natal, South Africa on September 16 th , 2014.

What followed next was an ‘out of gauge’ logistician’s delight.

To cross the three countries Instar needed to design and engineer specific transport combinations and make allowances for road infrastructure. The engineers developed and built a hybrid of transport and infrastructure measures including bridge propping, bridge bypasses, three different transport combinations, as well as a transport frame built out of bridge launching system components. This was a technique that had never been applied before.

The initial stage from the South African port and up into and through Zimbabwe was relatively straight forward, if ever moving a single piece weighing nearly 150,000 kilos is straightforward. The transformers were loaded on to 14 axle Goldhofer and 12 axle Cometto modular trailers and started their 1900 kilometre journey to the Mozambique border crossing at Cuchamano.

South African and Zimbabwean transport infrastructure is built according to British Standards. The bridges are able to take 20-tonne axle loads. Importantly, this was all quantifiable. Mozambique was another story.

According to its original Portuguese construction standards, Mozambique bridges could take a 12-tonne axle load. However, a 15-year long civil war meant the provenance of the infrastructure was questionable. Civil engineers simply had not been around during the fighting in order to make the necessary safety checks. Plus, the requisite documentation and certificates just did not exist. It was too much of a risk to attempt a bridge crossing in too many situations. Some estimates placed Mozambican infrastructure re-construction costs at an additional $7.2 million, to enable the ABB transformers delivery to the Songo site.

However, innovative Instar project-engineers designed a unique system to spread the 149 tonne load across 2 x 9 axle Cometto trailer combination, using a special frame fabricated in Germany.

The transformers stopped at Cuchamano, Mozambique, where the engineers had built a layover facility from scratch, in order to transfer the 149 tonne boxes from 14 axle Goldhofer trailers onto the specially made girder straddling the two 9 axle Comettos. Once loaded the average load per axle was 13.385 tonnes, the total load was 240.6 tonnes whilst the gross load was 349.5 tonnes. One prime mover led and two units pushed, and one transformer a time made the journey across Mozambique. The 14-axle Goldhofers’ returned to South Africa. The demanding delivery to Songo was successful, due to thorough route concept planning before the project, an in-depth analysis of the route, analyse of the potential for problems and using the right equipment.

Six bridges were propped in Mozambique and 3 by-passes constructed. Twenty nine bridges in total were thoroughly checked before the transformers crossed. The final leg was the most tortuous and slowest. One has to question the thought process of the engineers when they originally built the Cahora Bassa dam and the Songo transformer station. In an original piece of design, the latter was built on top of a mountain.

Without the latest technologies this stage could almost have been one barrier to far. From the base of the Pass to the delivery site was 9.8 kilometres. The road itself was a nightmare unless you are a hill-climb aficionado.

The gradient varied between 9% and 16%, the road was a maximum 7 metres wide and full of switchback hairpin corners. It did not take much imagination to see the myriad of cross fall cambers up to 10% causing a very expensive topple. It was a tough hike for a fit person, let alone for a 70 metre long 350 tonne GVW load. That was an impossibility. Beyond the pass was the town of Songo, with the usual roads and corners suitable for cars, vans and regular 13.8 meter truck loads. Eminently unsuited to the Instar load.

It was time for the final transport mode, the self-propelled modular transportation equipment, which is probably the tool of last resort for the ‘out of gauge’ project forwarding professionals. The 149 tonne transformer was loaded onto a 4 file, 6 axle configured SPMT. Using its tight turntable capability and load angle adjustment capability to counter the extreme cambers and gradients, the SPMT was walked through the pass, through the town and up the final mountain stages to the Cahora Bassa substation. There, the transformers were finally positioned using jacking and skidding techniques.

It took one week for each transformer to travel the 250 kilometres in Mozambique from border crossing to site. In total the transformers were transported over 2 200 km using three different transport combinations including the custom-built Instar girder transportation system and the self-propelled modular transporter. All the transformers were delivered within 62 days from arrival in South Africa.

The innovative use of well- engineered delivery solutions and forward planning, with a highly motivated team of project forwarding professionals, meant the project was completed before the rainy season and according to schedule.

Job well done

SL GIRDER “super leicht”

The custom-built SL “super leicht” girder transportation system as engineered and built by the Instar specialists really deserves closer attention. This single item was the game-changer, the single piece of innovative engineering and thought process that made the logistics route both practical and affordable.

Even government owned hydro￾electrical plants (read dams) providing power to a large part of the south African continent are run with an eye on cost, margin and return on investment.

The first transport route analysis to Songo was done on the basis that the transformer weighed 130 tonnes.

Mozambique infrastructure weaknesses led to estimates of $7.2 million on reconstruction and by-passes using a 12- 14 axle lines modular trailer. The second weight estimate of 146 tonnes meant the budget would have to be drastically increased and many more by-passes built.

In the end, ABB’s transformer weight was 150 tonnes. The resultant gross vehicle weight using a regular girder system (weighing up to 80 tonnes) would demand almost all 29 Mozambican bridges to be by-passed. A financial and technical impossibility given budget and weather restrictions.

Cash constraints aside, the tropical climate delivers an average 153mm of rain during the wet season – a 350 tonne GVW load would soon disappear up to its axles in the rich, red African mud.

Instar’s light weight construction was a paltry 29 tonnes, yet it had a load capacity of 150 tonnes. A factor of 1:5. This was unique in the industry and enabled the professionals to confidently transport over relatively weak infrastructure.