Engineering, manufacturing, construction and maintenance services provider Steinmüller Africa will showcase two header models at this year’s Power-Gen Africa event, which will be held at the Sandton Convention Centre from July 19 to 21.
Steinmüller Africa mechanical engineer Annelise Muller and piping divisional manager Lee Chapman explain that utility boilers have thousands of tubes performing different roles, depending on their location.
Headers are pipes that are used to interconnect many smaller tubes or, depending on the direction of flow in the pipe, distribute flow to smaller tubes. Headers are typically larger in diameter than the pipes they connect to and have thicker walls, and they enable the flow of steam and water into and out of the tubes they connect.
Steinmüller Africa specialises in designing and fabricating headers that are used in high- temperature and high-pressure applications. Chapman describes these headers as being relatively large-bore and thick-walled, and manufactured from alloy steels specifically suited to these applications.
Muller further notes that Steinmüller Africa’s headers are designed in accordance with commonly accepted design codes, including those of the American Society of Mechanical Engineers and the European Committee for Standardisation. She adds that Steinmüller Africa is also experienced in meeting additional constraints imposed by client specifications and quality-control measures.
Steinmüller Africa quality control and nondestructive testing (NDT) manager Carel van Aswegen notes that all the company’s headers are manufactured at its facility in Pretoria, adding that each header takes about three to four weeks to manufacture. He says the company’s automated drilling and welding process provides it with a competitive edge in the manufacture of headers, which are supplied to power utilities locally and overseas, and petrochemicals boiler plants as part of new builds or routine maintenance.
The workshop process involves a preparation phase in which the material for the header is procured and inspected, and the Guratu computer numerically controlled machine is programmed to the drawing dimensions for drilling and weld preparation, he explains. The pipe is then cut according to specification, and special weld preparations are performed, which help with the flow restrictions during the operation of the component.
The header is then manufactured through a series of welds, followed by NDT. The header can be pressure-tested for leaks either at the workshop or in situ with the system after installation.
The headers to be showcased at Power-Gen Africa have an outside diameter of 324 mm and a wall thickness of 38 mm, with nipple welds to a few of the connection tubes.
Further, Steinmüller Africa senior process engineer Shaun Titus and boiler process group leader Warwick Ham will discuss the merits of the coal combustion modelling of a utility boiler firing system using computational fluid dynamic (CFD) models to better understand efficient combustion.
The presenters explain that the future of electricity generation in South Africa is at the fore of discussions in the energy sector, owing to ageing power plants, adding that many life-extension studies have been initiated to determine the feasibility of performing life extensions at the plants. Tools, such as thermal calculations and CFD models, are being widely used to determine the impact of boiler operations under varying conditions, such as the fluctuating quality of coal being used at the stations.
Steinmüller Africa performed one such feasibility study at the Hendrina power station, in Mpumalanga, investigating the necessary modifications to extend the plant’s life to 2035 using CFD The presenters will outline how CFD capabilities have been developed to assist existing plants, operating under various changing inputs, to improve operation.
They will also present their findings regarding the various modifications that can be implemented across the station’s boiler areas that show high erosion, which could result in reduction of unit downtime.