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Steel Castings Pty Ltd
Cleaner Production - Optimisation of Binder and Catalyst Addition

Steel Castings Pty Ltd installed a computerised ‘Autocat’ system to control the addition of catalyst and binder for the production of sand moulds. The finer control of addition rates significantly reduced the number of reject moulds and achieved annual savings of $21,780 from reduced raw sand and chemical costs.

Background

Steel Castings Pty Ltd operates a foundry located in Port Melbourne, Victoria. The foundry produces high integrity steel, alloy and stainless castings from 50 kg to 5.500 kg in size. It also produces forging ingots to 5.25 tonnes in alloy, stainless and Duplex grades. 

Its customers include manufacturers of heavy earth moving equipment and mills and crushers for the mining industry, pumps and valves for the oil and gas industry, parts for the power generation, steel, sugar and paper industries and mooring equipment for the offshore oil and gas industry.

The Process

The casting process is achieved by pouring molten metal into a mould. Steel Castings uses sand mixed with binders and a catalyst to produce the moulds. After cooling, the casting is removed from the mould and the sand is discarded. All this discarded sand, which is 97 per cent pure silica sand and 3 per cent sodium silicate, is sent to landfill.

Pouring a mould

Pouring a mould

Steel Castings used a 6 tonne per hour continuous cold setting sand mixer, plus core making facilities for the production of moulds. In the preparation of moulds, sand is mixed with sodium silicate and an ester-based setting agent. As well as sand discarded from the final moulds, waste sand was generated because of:

The single largest cause of sand wastage was the temperature variation in the new sand. If the sand had only recently been processed (screened and dried) by the supplier prior to delivery, its temperature could be up to 100 degrees Celsius. When the catalyst addition rate was set for a temperature of between 10 and 30 degrees Celsius, this could cause significant problems, including setting of the sand inside the mixer. Conversely, during periods of cold overnight temperatures the sand cooled significantly, resulting in insufficient setting and consequent sagging in the middle of large moulds.

Cleaner Production Initiative

Steel Castings installed a computerised ‘Autocat’ system, for metering catalyst and binder to the sand in the mixing machine, at a cost of $22,700. The Autocat system utilises computer control for dosing of additives, to achieve the optimal ratio of catalyst to binder for the current operating temperature (sand and ambient), and the required curing time to suit the specific mould being prepared.

Mould preparation

The system continuously monitors parameters such as sand temperature, ambient temperature, and catalyst flow rate, and changes the catalyst-to-binder ratios and flow rates as required to maintain cure times. The system also blends slow and fast catalysts to give a mix with the correct set time at the correct strength.

Advantages of the Process

Steel Castings has realised a number of benefits from the installation of the Autocat system, including:

The introduction of the Autocat system has achieved attractive cost savings for Steel Castings.

ECONOMIC BENEFITS
Cost  
Autocat Machine $16,400
Installation $ 6,300
Total $22,700
Annual Savings  
New Sand $ 4,780
Binder $ 2,800
Catalyst $13,500
Sand Disposal $ 700
Total Annual Saving $21,780
Payback Period 1.1 years

The reduction in labour costs also contributed significantly to the savings achieved, resulting in a true payback of closer to six months.

Cleaner Production Incentive

The possibility for reducing sand wastage from the mould preparation activities was identified by the developer of the Autocat system. The developer contacted Steel Castings to see if they would be prepared to trial a prototype of the Autocat system. A 12 month evaluation was extremely encouraging, after which Steel Castings purchased the prototype.

When the company expanded operations in 1992 and installed a second, 12 tonne per hour, sand mixer there was no hesitation in purchasing a second Autocat unit.

Barriers

There were no significant barriers to the introduction of the Autocat system. In particular the operators who prepared the sand moulds were very receptive to the technology because it reduced the number of defective moulds. There was minimal requirement for retraining.

Further Developments

Steel Castings has continued to benefit from these initiatives.

Contact

Mr James West
Managing Director
Steel Casting Pty Ltd
49 Bertie Street
Port Melbourne VIC 3207
Ph: 61 3 9645 1333
Fax: 61 3 9645 1909
Date of implementation: 1992
Date of further initiatives: Ongoing.
Case study prepared: January 1997 by ACCP 
Date last modified: May 2001.
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