Sam S.,Tata Steel |
Sen B.N.,Tata Steel |
Tzan E.P.,NatSteel Holdings Pte Ltd. |
Soon Y.L.,NatSteel Holdings Pte Ltd.
SEAISI Quarterly (South East Asia Iron and Steel Institute) | Year: 2010
In Reinforced Concrete Construction, off-site assembly of reinforcement bars that are transported for subsequent installation on site before concrete casting is gaining popularity. This not only reduces construction time but also offers other advantages like improved on-site labour productivity, avoidance of site congestion, better quality of caged reinforcement, reduced wastage etc. Many such assemblies use MIG spot welding between transverse rebars, which is superior to tying with wires in retaining the shape of the cage till fixing/casting on site. However, a problem often encountered during stacking, lifting, transportation or fixing is the sporadic failure of weld joints. The wide variation in stacking conditions as well as lifting mechanisms commonly deployed on sites does influence the nature of load on the joints. In case of such failures, rework of the assembly jeopardizes the construction schedule and adds unnecessary cost. Apparently, no known standard guideline/specification is available for welding such cages as strength of these welds is not part of the structural engineering design. A study was made to map the weld joint characteristics vis-a-vis strength from the current welding practices for cage welding at NatSteel, Singapore with various combinations of diameters of rebar welded together. In 3 combinations of diameters studied, it was observed that weld length has the most influence on the strength of the joints, and the depth of weld penetration beyond a threshold value does not offer any significant benefit. The direction of force relative to the wetd on the rebars also determines the strength of the welded joints. These findings will be used in determining the points & orientation of welds within a reinforcement cage.
Weikang C.,NatSteel Holdings Pte. Ltd.
SEAISI Quarterly (South East Asia Iron and Steel Institute) | Year: 2015
In roiling mill, oil fired reheating furnaces are used to heat up billets to suitable rolling temperature (around 1060°C) before it is being rolled into desire shapes and sizes. The furnace firing process releases heat energy in the furnace creating a radiation and convection heat transfer onto the billets. At the end of the heating process, the waste gas which contain high heat energy are being channel out to the chimney stack before releasing to the atmosphere, ranging between 300 - 425°C. In an effort to optimize usage of energy and reduce carbon footprint in NatSteel, an Organic Rankine Cycle (ORC) was integrated into the furnace system to tap the waste heat energy before it is discharged into the atmosphere. The waste heat energy is utilized to generate electrical power (Nominal Power 555kW) which is fed directly into the electric grid available for use by other electrical consumers in the rolling mill.
Wei L.T.,NatSteel Holdings Pte. Ltd. |
Yuetchuan J.T.,NatSteel Holdings Pte. Ltd.
SEAISI Quarterly (South East Asia Iron and Steel Institute) | Year: 2013
Driven by increasing operating costs resulting from the relatively high electricity prices in Singapore, NatSteel Holdings Pte Ltd has vigilantly planned out a series of electrical energy saving projects to keep operating cost low. Conventional method of energy saving usually only limits usage. But, in view of Natsteel's capacity expansion plan, energy usage will only increase accordingly. As such, a more holistic approach is used instead to seek out opportunities for energy efficiency improvement. Through plant-wide energy audits, opportunities for improvements were identified and implemented in stages, which includes Variable Speed Drives (VSD), High Efficiency Motor, Closed-loop Control, Compressed Air Centralization and Process Optimization. In this paper, we will share some of the improvement works done to achieve energy savings while maintaining or improving operation performance.
Soon C.S.,NatSteel Holdings Pte Ltd.
SEAISI Quarterly (South East Asia Iron and Steel Institute) | Year: 2011
Singapore is a small island nation with a total land area of about 650 sq km and a population around 4.8 million. Ranked as the second most populated country in the world after Monaco, Singapore is also often ranked as the cleanest country in the world. Singapore has acceded to the Kyoto Protocol of the United Nationals Framework Convention on Climate Change (UNFCCC) on 13 April 2006 in line with Singapore's intention to participate in the international arena on managing greenhouse gas emission levels in ways that would not harm economic growth. As a global logistics hub, Singapore is also a signatory to other international environmental agreements which include the Bessel Convention, the Ozone Treaties and the MARPOL Convention. This paper provides an overview of the environment issues for a steel mill operating in Singapore. In particular, the key environmental issues that will likely to be of concern will be presented and discussed.