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Product category: Metals and Minerals Processing News
News Release from: Flowserve | Subject: Worcester V-Flow control valves
Edited by the Processingtalk Editorial Team on 27 June 2003

AvestaPolarit upgrades with Worcester
Valves

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AvestaPolarit has upgraded the gas control system on its steel mill Argon Oxygen Decarburisation converter, to provide greater operational flexibility through increased gas flows and enhanced control

AvestaPolarit has upgraded the gas control system on its Argon Oxygen Decarburisation (AOD) converter at its steel mill on Shepcote Lane in Sheffield This will provide greater operational flexibility through increased gas flows and enhanced control capability during the refining of stainless steel

AvestaPolarit is the largest stainless steel maker in the UK and is a subsidiary of Outokumpu of Finland.

The company produces a large range of stainless steel at sites in Scandinavia, the US and the UK.

AvestaPolarit in Sheffield manufactures a wide variety of steel grades, finishes and products that are supplied to a broad group of customers who, in turn, make anything from cutlery to industrial chemical plants.

The site at Shepcote Lane has a melting plant with a capacity of over 500,000 tonnes of finished products each year, along with cold rolling and finishing facilities that produce around 300,000 tonnes of finished product annually.

Production at the site consists of stainless sheet between 0.4 and 6 mm in thickness and up to 1.5 m wide.

The AOD converter is used to remove carbon to the extremely low levels required for stainless steels with the liquid steel being supplied from the electric arc furnace at the plant.

The gas system is designed for continuous operation, 24 hours per day, seven days a week and was supplied by VAI Industries (UK) to give increased gas flows and better control.

The four main gases are oxygen, pure and industrial argon and nitrogen, which are blown into the steel at high pressure through submerged pipes at the bottom of the AOD converter.

The gas mixtures can vary from pure oxygen to pure inert gas depending upon the need to generate temperature in the steel and the need to promote the carbon removal reaction.

Nitrogen and argon are equally effective in the carbon removal process and since nitrogen is approximately one-tenth the cost of argon, nitrogen is used wherever the specified maximum nitrogen content of the steel allows.

The pipes, which are called tuyeres in the steel making industry, are actually two concentric pipes with a cooling shroud of inert gas flowing between the inner and outer pipes and the working gases flowing down the central pipe.

The shroud gases are there to prevent burn back of the pipes when blowing oxygen.

AvestaPolarit stipulated that all control valves were to be pneumatically actuated, controlled with electro-pneumatic positioners with closed position indication.

The block and vent valves were also pneumatically operated fitted with open and closed position indication switch boxes.

Flowserve Flow Control, already an approved supplier to AvestaPolarit, was chosen to provide valves for the system.

Nine Worcester V-Flow control valves were stipulated (including four in stainless steel and four in monel) to deal with the highly demanding application and one in carbon steel, in sizes ranging from 14mm to 80mm.

Additionally,Worcester Controls manual isolation valves, ranging up to 150mm including three Series 52 valves in monel were incorporated into the system.

All pneumatically operated valves were fitted with Norbro actuators and PMV/Norbro ancillaries.

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