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Trico Products Pty Ltd
Cleaner Production - Replacement of Electrostatic Spray Guns with Plastic Electrostatic Rotary Bells

Trico Products Pty Ltd has implemented two major cleaner production initiatives at its production facility. The replacement of electrostatic spray guns with plastic electrostatic rotary bells in its coating operations has significantly reduced reject rates and resulted in annual savings of $59,000 per annum. The replacement of a conventional hot caustic paint stripping process with a sand furnace has been even more financially successful, with annual savings in the region of $126,000.

Background

Trico Products Corporation has operations in the USA, Mexico, England, Wales, Argentina and Australia. Trico Products Pty Ltd (Australia) is a manufacturer of windscreen wiper systems for the domestic vehicle industry and also exports to the USA and England.

The philosophy of Trico Products Pty Ltd is to retain its prominence in the Australian vehicle industry by staying ahead of advances in technology and vehicle design.

The Process

As part of the production process, all wiper components are coated to provide corrosion protection and an acceptable surface finish. This is done in two stages, involving electro-deposition of an undercoat, and electrostatic spray application of an acrylic top coat.

In the pre-excisting process, the top coat was applied using two AN-9 electrostatic spray guns coupled with a rotating rack arrangement. Although electrostatic spraying was used, the guns still required air for atomisation of the paint droplets. This resulted in a relatively high rate of overspray generation. The excessive overspray caused an unacceptably high reject rate on the surface finishing.

During the painting process, the racks used for conveying the components through the spray booth would become coated with paint and require regular cleaning. The paint was removed by soaking the racks in a hot caustic bath for eight hours. A maximum of 35 racks could be immersed in the bath at any time. After soaking, the racks were removed and cleaned with high pressure water to remove residual paint and caustic carryover. The use of hot caustic presented safety problems and minor spills contributed to a hazardous working area. The water cleaning of the racks generated approximately 1,500 litres of wastewater per day, which was collected for specialist treatment off-site.

The caustic paint stripping process comprised a 4,000 litre tank of caustic based paint stripper maintained at a temperature of 100 degrees Celsius. The caustic had to be replaced between two and four times per year.

Cleaner Production Initiatives

In 1996, Trico replaced the electrostatic guns with two electrostatic rotary atomisers (bells). The bells use the high speed of a rotating disc, rather than air, to atomise the paint, resulting in a higher transfer efficiency of paint to the work piece.

Typical electrostatic spraying operation using a rotary atomiser

Typical electrostatic spraying operation using a rotary atomiser

The rotary atomisers chosen by Trico use a special plastic bell instead of the more conventional metal bell. The advantage is that the distance between bell and workpiece can be reduced without electrical arcing occurring. This results in less overspray.

By adjusting the stroke of the reciprocator and controlling the shaping air, the evenness of the spray build can be fine tuned.

The hot caustic process used for stripping paint from the racks was replaced in 1996 with a sand furnace, which totally removes the paint from the racks and does not require any high pressure water cleaning. All paint wastes are combusted within the sand furnace and the only discharge to the environment are products of combustion (i.e. carbon dioxide, water vapour and nitrogen oxides).

Advantages of the Process

The significant advantages to Trico in implementing these cleaner production initiatives have been:

The rotary atomiser has achieved a lower reject rate due to more uniform paint coverage. Wiper assemblies comprise an arm assembly and blade parts, but though reject arm assemblies can be reworked, reject blade parts have to be scrapped. The reject rate on the arm assemblies has fallen from 9 per cent to 3.5 per cent, while the reject rate on the blade parts has fallen by 2 per cent.

Paint usage has decreased from 60 litres per day to 55 litres per day, primarily due to the increased transfer efficiency. This has resulted in a cleaner environment within the paint booth, with a 50 per cent reduction in sludge generated from the water wash wall, and less maintenance required on the suction fan and baffle system (reduced from 10 days to 3 days per annum). The finer atomisation generated by the bells has resulted in an increased rate of solvent evaporation. To compensate for this the paint has to be sprayed at a lower viscosity, which is achieved by running at a slightly higher solvent content.

Reduced work distance between the Nordson bell and a conventional metal bell

Reduced work distance between the Nordson
bell and a conventional metal bell

The savings have been significant, with a payback period of approximately 16 months being realised.

ECONOMIC BENEFITS (1996) - Rotary Atomisers

Costs

<> 

Rotary Atomisers

$67,500

Equipment Modifications

$10,000

Total

$77,500

Annual Savings

 

Reduced Blade Rejects

$35,000

Reduced Arm Rejects

$15,000

Reduced Paint Usage

$ 9,000

Total Annual Savings

$59,000

Payback Period

1.3 years

The sand furnace allows much quicker cleaning of racks (20 minutes for 15 racks), and has a number of other advantages:

There are also a number of minor drawbacks, including:

Even with these minor drawbacks, the savings from the introduction of the sand furnace have been significant.

ECONOMIC BENEFITS (1996) - Sand Furnace Paint Stripping

Costs  
Sand Furnace $ 59,750
Miscellaneous Works $ 15,250
Total $ 75,000
Annual Savings  
Waste Caustic Disposal $ 60,200
Raw Chemical Costs $ 48,700
Effluent Treatment $ 16,800
Total Annual Savings $125,700
Payback Period 0.6 years

Cleaner Production Incentive

The significant factor in replacing the electrostatic spray guns with the rotary atomiser was the previous high reject rate from painting operations. Although some components could be reworked, a number of smaller components could not. This high reject rate was adding to total production costs.

The driving force for replacement of the caustic bath for cleaning of paint racks was the elimination of a hazardous chemical process.

Barriers

The main barrier to the successful change over to the rotary atomisers was of a technical nature relating to paint formulation. Reformulation of the paint was required and this involved close cooperation with the paint supplier.

The rotary atomisers also produce a more complex spray pattern than conventional spray guns, and this has required more rigorous process control on the spraying process.

Further Developments

In late 1999, as a result of the sand furnace not performing as efficiently as predicted and concerns with occupational health and safety issues, the cleaning of the paint racks was outsourced eliminating the use of the sand furnace. The rotary atomisers however continue to be utilised effectively.

Other cleaner production initiatives undertaken by Trico include the recladding, in 2000, of an old asbestos cement clad building with foam-steel laminate on the walls and roof, avoiding the construction of a new building. The reclad building has superior insulation and energy efficient lighting has been installed. The new and refurbished factory also includes a new paint plant and different oven design. The upgrades have resulted in a reduction in energy consumption by 8%.

Trico Products Pty Ltd is currently working towards accreditation to ISO14001, is a signatory of the Greenhouse Challenge and a participant in Victoria's Sustainable Energy Authority's Energy Smart Program. 

Contact

Peter Smith
Manager Product Engineering
Trico Products Pty Ltd
820-850 Princes Highway
Springvale  VIC  3171
Ph: 03 9271 3235
Fax: 03 9271 3290
Email: peter.smith@tricoproducts.com.au

Casestudy implementation: 1996
Further initiatives: 2000
Casestudy initially prepared: February 1997 by the Australian Centre for Cleaner Production

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Last modified: May 2001