Machining Coolant Recycling

Unidrive Pty. Ltd.

Unidrive Pty. Ltd. undertake extensive machining operations during the production of automotive components. In the past this resulted in the generation of 20,000 litres of waste coolant every week. By implementing a coolant recovery and recycling system, Unidrive have saved approximately $179,000 per annum as a result of more efficient coolant usage and management.

Contact

Mr Kevin Montague
Technical Support Group
Unidrive Pty. Ltd.
45-49 McNaughton Road
Clayton VIC 3168
Ph: 61 3 9542 4101
Fax: 61 3 9544 8117
 
Mr Peter Mitchell
Technical Services Chemist
Houghton Australia Pty. Ltd.
287 Wickham Road
Moorabbin VIC 3189
Ph: 61 3 9555 0344
Fax: 61 3 9555 0748

Background

Unidrive Pty. Ltd. was established in the late 1950s and currently has a workforce of over 400. It manufactures drive assemblies and other associated components, such as lower suspension arms, for the Australian automotive industry. The components are manufactured by casting or drop forging, followed by machining to achieve the desired tolerances and surface finish.

The Process

In its Melbourne operations, Unidrive has a total of about 800 machines of varying size and capacity, which are used for grinding and machining operations. Coolant is used in these operations to provide a degree of lubrication and to remove heat from the workpiece. Coolant is pumped to the workpiece from sumps, generally located under each machine. As a result of the machining operations, the coolant becomes contaminated with particulate material and 'tramp' oil from a variety of sources. In the case of cast iron machining and grinding, a viscous black sludge builds up in the bottom of the machine sumps.

The contamination from oil and sludge results in deterioration of the coolant. This stimulates the growth of bacteria which feed on additives, such as emulsifiers, present in the coolant, and can cause instability and eventual emulsion splitting if not controlled. Anaerobic bacteria also produce hydrogen sulphide, which is the cause of 'Monday morning odour', and is one of the main causes for dumping coolant.

Approximately 20,000 litres per week of waste coolant was being generated by Unidrive's machining operations. In addition, 6 different types of coolant were being used and this complicated the possibility of recovery and recycling.

Cleaner Production Initiative

In conjunction with Houghton Australia (a supplier of industrial oils and chemicals, including machining coolants), Unidrive has implemented a coolant recycling and recovery system. The systems utilises Hyde technology from the United States. At the same time, the number of coolant fluids used by Unidrive was rationalised from six to two. The system was installed in late 1993.

Contaminated coolant is removed from the individual machine sumps using a portable pump and storage tank unit. The contaminated coolant is then transferred to a coolant recycling unit. The coolant is filtered to remove solids and heavy sludge. Free floating and dispersed oil are then removed in a coalescing separator. The recovered oil is collected for disposal. The cleaned coolant is continually circulated through the recycling unit until it is required in the plant. The coolant is then returned to the machine by a reticulated mains system. This means that a machine can be refilled with cleaned coolant immediately after the dirty coolant has been pumped out, thus achieving minimal disruption to production activities.

Using this system, the coolant in individual machines can be changed before the onset of any significant deterioration of the coolant. This requires monitoring of the quality of coolant in each machine to ensure the integrity of the program.

Total waste coolant generation has been reduced from 20,000 litre per week to 8,500 litres per week. Actual waste generation from the machines has been reduced by 95 per cent (there are other sources of waste coolant such as carryover with swarf).

Advantages of the Process

The main advantages of the coolant recycling system to Unidrive are:

In addition to savings in new coolant and waste coolant disposal there have been significant savings from the installation of a reticulated mains system for delivery of the recycled coolant to the machines. Previously, the new coolant arrived in 200 litre drums, and had to be manually diluted with water to achieve the correct strength, before being carried to the particular machine in 20 litre pails. Now, the coolant is delivered in 1000 litre bulk containers and dosed directly into the clean side of the coolant recycling unit in order to maintain concentration and makeup for losses due to evaporation and carryover with swarf.

Better control of the coolant concentration is now being achieved, and this has resulted in a cleaner coolant and an increased level of operator satisfaction.

Another unquantifiable benefit that has flowed from the coolant recycling program is prolonged tool life. This has not been able to be quantified because there was not an adequate baseline available. Nevertheless, Unidrive believes that there have been considerable benefits in this operational area.

The economic benefits to Unidrive have been significant:

ECONOMIC BENEFITS

Costs  
Coolant recovery system $121,000
Labour (per annum) $ 30,000
Total $151,000
Annual Savings  
New coolant $ 88,500
Waste coolant disposal $ 40,100
Delivery $ 1,000
In-plant distribution of coolant $ 30,000
Machine cleaning $ 7,000
Reduced water usage $ 12,000
Total Annual Saving $178,600
Payback Period 0.8 years

Cleaner Production Incentive

The main incentive for implementing the project was cost reduction. Working closely with the coolant supplier, Houghton Australia, was critical in the identification of this opportunity.

Unidrive's customers are also starting to focus on environmental responsibility as an issue in sourcing products and this also influenced Unidrive in searching for cleaner production opportunities.

 

Barriers

A number of barriers have been experienced and overcome during implementation and running the program.

There was some initial employee resistance to the introduction of the recycling process. This was quickly overcome, and was facilitated by thoroughly cleaning all of the machines prior to the change-over to the recycling system. The ongoing success of the project has been enhanced by the appointment of a fully dedicated employee to operate the unit. This has been critical in developing interest, responsibility and ownership for the recycling system.

After commissioning, it was found that heavy particulate loadings in the contaminated coolant were causing excessive wear and increased maintenance on the pump of the recycling unit. This was overcome by fitting a prefilter.

A further concern was uncertainty as to whether the program had actually reduced waste volumes. As total site waste generation had not fallen by the amount expected, it was questioned whether the anticipated coolant savings had been achieved. The savings were demonstrated by having available data which showed that while reduced waste coolant generation had been achieved, waste generation in other areas had actually increased. This meant there had been little change in overall site waste generation. Having a good waste database meant that the changes in waste generation from various operations could be identified.

Case study prepared: June 1997 by ACCP

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The Cleaner Production Case Studies Directory is part of EnviroNET Australia.
For more information contact:
Environment Australia
Environment Protection Group
PO Box E305
KINGSTON ACT 2604
AUSTRALIA
Email: cproduction@ea.gov.au
URL: http://www.environment.gov.au/net/environet.html


URL: http://www.environment.gov.au/portfolio/epg/environet/ncpd/auscase_studies/unidriv1.htm
Last modified: 4 May 1998