By Anthony Martiniello
The Matala Dam in the province of Huila, Angola, was built in 1954 on the Cunene River to serve two objectives: generate power from a 40 MW hydroelectric station for use in southern Angola and to store water for irrigation in adjacent farmland. The project’s remote location confronted SNC-Lavalin’s engineering team with three primary obstacles: the selection of design standards, adherence to design requirements and supplier interfacing.
The owner of the dam, Empresa Publica de Producao de Electricidade (PRODEL), contracted SNC-Lavalin Inc. (SNCL) to execute an engineering, procurement and construction (EPC) mandate for the rehabilitation of Matala Dam.
Due to the severity of the alkali-aggregate reaction (AAR) in the concrete, which caused considerable swelling to occur, it rendered the existing flap gates jammed and non- operational, further increasing the risk to the stability of the structures.
“The rehabilitation of the Matala Dam was primarily necessary to ensure the stability and the structural safety of the dam, which was under risk of collapsing,” PRODEL Project Manager Celso Pontes said. “The rehabilitation was also required to ensure the operation of the powerhouse generating capacity and the spillway control systems in order to improve the hydraulic discharge capacity.”
The principal works performed by SNCL included:
- Construction of a new spillway equipped with eight radial gates;
- Rehabilitation of the concrete structure affected by AAR;
- Evaluation (capacity and structural integrity) of the concrete bridge structure;
- Rehabilitation of the road bridge including resurfacing of the deck and bearing rehabilitation; and
- Grouting works.
Selecting design standards
Amongst SNCL’s concerns was determining the applicable civil, electrical and mechanical design standards to be used for different facets of the project. Determining such a standard is traditionally done with respect to the project country’s established codes. In the case of the Matala project, PRODEL allowed for the implementation of North American or international standards based on the requirements of the specific design.
Consequently, SNCL proposed from the onset to proceed predominantly with the application of North American standards, and so the design began and evolved on the basis of these standards.
However, given the project location and considering the frequent use of European standards in the local and regional market, the engineering team afforded all suppliers the opportunity to propose an equivalent standard with respect to the North American one specified.
Adhering to design requirements
The ability to implement North American and international standards afforded the SNCL engineering team certain latitude in being able to rapidly advance the engineering design phase of the works without having to continually request change notice approvals from PRODEL for standard substitutions. The flexibility to use either North American or international standards was a clear and accepted understanding by both parties.
As the design phase progressed, constraints arose due to the use of North American standards, which forced the design team to seek equivalent international standards. The constraints in question relate to adherence to design requirements and supplier interfacing.
The team subsequently needed to engage the services of suppliers found in the local Angolan market or nearby countries within the South African region. The need to adhere to a tight project schedule of 44 months and the EPC nature of the contract required various suppliers from around the world to supply equipment in parallel. A consequence of engaging these local and international suppliers was that many clarification requests were raised that required subsequent confirmation.
Local market supplier interfacing
Dealing with local Angolan suppliers presented various complex situations, ranging from difficulty in obtaining materials, challenges related to ensuring qualified resources were available at the suppliers’ facilities, and interfacing with the local suppliers.
Obstacles included:
- Identifying local suppliers that can execute intricate fabrication of components that respect the engineering criteria. Local suppliers encountered had no internal design nor engineering teams at their facilities, which resulted in SNCL Engineering producing detailed fabrication drawings. As a result, many design constraints relevant to fabrication were not identified until the manufacturing phase, forcing SNCL’s team to review and revise drawings within 24 hours to prevent schedule delays.
- Receiving engineering deliverables and documentation from suppliers. Many documents were produced jointly by the supplier and SNCL. However, the negative drawback of providing such detailed support was that at times, SNCL did not have a clear indication of the supplier’s full understanding.
- Interactions with suppliers’ quality control departments, which were often not set up to handle large or complex orders. As such, SNCL deployed its own third-party quality control inspectors to supplier facilities to ensure follow-up and to provide support.
- Language barriers and differences in operating practices. Often, SNCL circumvented such issues by using third-party quality control inspectors who were required to be fluent in Portuguese, the primary language spoken in Angola. Quality control was a success because these inspectors demonstrated specific requirements to the supplier, while also providing support and physically verifying works as they progressed.
- Coordinating suppliers’ on-site support to the SNCL Engineering team. This coordination effort was often difficult given that many vendors were simultaneously involved with a number of other projects. SNCL ended up bringing various suppliers’ personnel to the site on different dates and planned the works accordingly to ensure that they could assist and support SNCL at the correct times. The end result was that the installation, testing and commissioning works were often performed in separate phases to allow for the correct supplier personnel to be present.
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| Each of the eight radial gates installed as part of the Matala Dam rehabilitation was designed while considering the safety of future operations and maintenance personnel for routine work. |
Overcoming obstacles faced with Matala’s radial gates
Although the successful execution of a number of Matala’s components required significant collaboration between SNCL and its suppliers, the supply of the dam’s radial gates formed part of the largest and principal package SNCL was to deliver.
The supply consisted of eight radial gates and associated components including hydraulic power units that actuate the hydraulic cylinders for gate operation. The gates are 15-meters wide by 9.5-meters high. The gate design considered the safety of future operations and maintenance personnel that perform routine inspections or maintenance work.
Selecting a standard
The initial design criteria and fabrication requirements for this equipment were specified per North American standards. However, following discussions with the Chinese supplier, a request to use German Institute for Standardization (DIN) standards was instead proposed as the supplier was more familiar with DIN design standards.
In addition, the supplier did not have welders qualified per American Welding Society (AWS) or Canadian Standards Association (CSA) standards. Instead, the supplier’s proposed welders were qualified per the Chinese GB (Guobiao) welding standard.
Matching non-matching requirements
Over the course of the design review, the SNCL team accepted several proposed alternatives with respect to specified design standards.
For example, when considering the design of the steel structure of the radial gates, the supplier requested the option of using DIN standards. Considered in many regards to be equivalent to the CSA criteria for this design type, the standards in question were accepted with explicit conditions.
One condition, for example, related to safety factors applied to the design loading conditions. If the safety factor indicated in the DIN standard was less severe than the equivalent from the CSA, the more severe of the two was selected.
The design progressed and was verified continuously by the SNCL team, including the fabrication period when specific issues arose. In more than one instance, SNCL engineers were dispatched to the supplier’s facilities to ensure that the new design review and coordination of detailed engineering was advancing in a technically compliant manner and at an acceptable rate.
Additional change requests from the supplier came in the form of material substitution. Given the schedule constraints, obtaining ASTM- or EN- certified steel would have added considerable time to the already stringent schedule.
As such, when the supplier proposed using Chinese GB (mandatory) standard or GB/T (recommended) standard steel materials equivalent to the specified ASTM materials, the team accepted the proposed alternative. Nonetheless, the following measures were implemented to ensure the material quality obtained was equivalent to that specified by SNCL or better:
- Testing of all materials was done in-house by the supplier and by SNCL at an independent third-party facility;
- Material test results were compared against the specified ASTM material properties and not the Chinese GB equivalent properties. Even slight deviations from the ASTM specification were carefully scrutinized for acceptability. If any doubt existed, the material was rejected;
- Stainless steel components were tested in greater frequency, often per-cut plate or component, even if from the same heat number or pour.
Some clarifications and material replacements occurred over the course of fabrication, but the quality of the material was more controlled and ultimately better assured by the implementation of such controls.
The supplier’s welders were certified according to the Chinese GB standard. To bring in full-time AWS welders would have been too complicated given the time constraints, as the welders would have had to come from another division of the supplier and be recertified. Instead, SNCL opted to have one of the supplier’s welding inspectors sent for certification and training to become a fully certified AWS inspector.
The inspector was also required to be present and made responsible for qualifying the results of all GB welder testing. At the supplier’s in-house welding school, tests were performed by each welder identified to work on the Matala project.
The results were examined by the supplier’s in-house inspectors, supplier’s AWS-certified inspector and SNCL resident inspectors. The results of the testing were confirmed per the guidelines set forth by the AWS.
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| Alkali-aggregate reactions in the concrete caused considerable swelling to occur, jamming existing flap gates. |
SNCL then closely followed up the work performed by these welders. The supplier elected the AWS-certified inspector as the principal person to oversee all works performed by the welders. In parallel, the SNCL resident inspectors also reviewed all welding works performed.
Naturally, this supplier had several suppliers of its own for specialized equipment, forgings and castings. The SNCL team audited and carefully monitored these sub-suppliers.
Several times, SNCL resident inspectors made required and unannounced visits at the facilities of these sub-suppliers to ensure the works were progressing with proper quality control protocols in place.
If additional follow-up was required, one of the resident inspectors would remain at the sub-suppliers’ facilities until the issue was resolved. The foresightedness of mitigating potential issues at the sub-suppliers’ facilities allowed for the continued advancement of the works and subsequent schedule gains.
Dealing with differences
A number of challenges surfaced due to language barriers, time zone differences, cultural differences and differences related to the interpretation of design and manufacturing equivalencies. To address these, SNCL began by establishing a dedicated team in China and Montreal. In China, the team consisted of expeditors, procurement specialists and inspectors. More importantly, SNCL positioned two full-time inspectors at the supplier’s facilities for the duration of the works.
The team implemented several measures by which the follow-up and coordination of activities could occur seamlessly and allow for continued progression of the works. SNCL made the decision to hold weekly conference calls, which was increased to several times a week during peak periods, to ensure design issues were resolved, fabrication issues were addressed and mitigation measures were put in place to avoid any potential risks that could arise and affect the delivery schedule.
SNCL resident inspectors maintained punch lists during the fabrication works. These punch lists served to provide the shop floor personnel and shop supervisors with clear items to be addressed and actions to be taken.
SNCL resident inspectors and shop supervisors held daily meetings to ensure work tasks for the day were clearly established, and components requiring inspection were clearly identified for inspection-hold points.
SNCL’s resident inspectors produced corrective action requests (CARs) and non-conformity reports (NCRs) when needed. These reports were put on display boards for the supplier supervisory staff to see and consult. The CARs and NCRs were often discussed in detail with the shop supervisors, and the information was then shared amongst the workshop floor personnel to create awareness and prevent the issue from reoccurring.
Conclusion
Despite the adversities faced by the SNCL Engineering team, the works were successfully completed and accepted by PRODEL. SNCL, working together with all of its suppliers, managed to achieve an understanding with them in regard to the quality of works required to ensure successful completion. Given the experience gained from executing this EPC project, some of the principal lessons learned by SNCL include:
- Initial design concepts should have taken into consideration European standards as being predominant, instead of North American standards from the start, considering the project location and supplier capabilities.
- Allowing suppliers to propose equivalent standards to those specified, with which they are more familiar and can execute accordingly, can yield schedule gains if properly managed.
- Standards are not identical. However, similarities exist amongst some international standards for which equivalencies can be considered based on the type of equipment being manufactured.
- Inspectors should be dispatched to suppliers’ facilities for any type of equipment supply in order to ensure full oversight of the fabrication and supply process.
- The setup of face-to-face meetings with a supplier is essential to ensure there are no misunderstandings related to design and fabrication requirements.
Going forward, close follow-up will be maintained by SNCL and PRODEL to ensure the equipment at Matala Dam continues to operate properly.
Anthony Martiniello is a project manager for SNC-Lavalin Inc. in Canada.
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