11 pumps for descaling in new Indian steel plant

Paul Boughton

Building a new steel plant from the ground up is no small task, rather one which requires extraordinary amounts of planning and careful engineering. The project by NMDC Ltd, an Indian, state-owned, public enterprise is now on target for completion by the end of 2015. 

Part of the thin slab production line incorporates a large descaling plant which is being powered by 11 S500 high-pressure pumps supplied by RMI Pressure Systems.

As part of its expansion programme, NMDC Ltd is setting up a 3 million tonne per annum capacity Integrated Steel Plant in Nagarnar, located 16km from Jagdalpur in the Chhattisgarh state of India.

The blast furnace will be designed for production of 9,900 tonnes per day, while the thin slab rolling package includes a vertical, curved slab caster which comprises two independent casting strands, which have an hourly average capacity in excess of 205 tonnes per hour each.

The thin slab rolling part of the project is being installed by Danieli, a company which aims to design and produce turnkey production plants for the steelmaking business. 

The project in Nagarnar will incorporate two descaling pump stations, producing 1,870l/min and 2,380l/min respectively at 400bar. Having been handed the design specifications RMI Pressure Systems, a leading global supplier of high-pressure and high-volume pumping stations, produced a carefully engineered solution which will be installed by Danieli.

One of the key factors in determining the quality of the final steel product is the scale removal process. Scale which is not properly removed can be combined with the steel billet as it passes through the rollers, creating imperfections in the steel, which may have to be scrapped or sold as 'imperfect' at lower cost. It can also cause increased levels of wear on the mill stand's rolls, which will increase maintenance costs. Therefore, the use of high pressure descaling units in steel strip production is very important to ensure high quality strip is produced.

De-scaling equipment basically consists of a high pressure pump, powered by an AC motor which is controlled by a variable speed drive; all of which supplies water through specifically designed headers, which are directed at the hot steel. The combined action of the water pressure and the rapid cooling of the steel results in the scale being removed from the billet.

With modern steel rolling mills producing an array of different steels, it is important that the facility has the ability to adjust any settings as easily as possible when the next product is about to be produced to make sure that the process is reliable and efficient for all steel types. These differing requirements pose potential problems for the production facility and, unless they are optimised, could lead to increased production costs and reduced margins. This places added pressure on the de-scaling equipment as, not only must it perform reliably at all times, it is also required to allow for the adjustment of pressures and water flow rates as the steel type changes to achieve the desired impact force required.

Mike Sherman, Marketing Manager for RMI, comments: "This de-scaling solution has been characterised by a combination of variable speed and fixed speed pumps with high flow rates and the application of an optimised nozzle pattern. The benefits of this de-scaling package are reduced investment costs and lower maintenance costs as well as substantial energy savings due to flexible operation according to the process requirements.

The design specification called for each pump station to have one stand-by pump in order to ensure full production could continue in the event of maintenance being carried out. This design also allows for the duty cycle to be rotated. Each pump was specified to produce a nominal output of 520l/min at 400bar, which is well within the capabilities of the S500 model, which in this case were equipped with 55mm rams. In all, 11 S500 Quinmax pumps will be installed at the new plant.

The S500 Quinmax pump features a five piston crankshaft which allows it to pump higher flow rates (340–1080Ltr/min) at greater pressure (190 – 1000Bar) with reduced loads on the shaft and bearings for greater periods before service intervals. The S500 range is driven by 300–400kW motors and feature ram diameters spanning from 50mm to 80mm.

The advanced five plunger design offers significant benefits over traditional designs in terms of reliability, maintenance requirements and noise during operation. Because the load on each plunger is reduced in comparison to three plunger pumps of similar specification there is a 40 per cent reduction in the fluid velocity per plunger which results in lower hydraulic noise. The crank is able to turn slower, which reduces mechanical wear and noise, while stroke lengths are longer, which leads to fewer reversals.

In addition, each of the pump units is equipped with the RMI pump health monitoring system, which includes water pressure switches to indicate if the inlet pressure has dropped below the minimum requirement or if the outlet pressure has exceeded the maximum setting. These are complimented by sensors for the lubrication oil, providing crucial information on oil level, temperature and pressure, ensuring that each of the pumps delivers reliable service.

For  more information, visit www.rmipsl.com

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