Metal Casting Cos

1. WASTE MINIMISATION

Introduction

Waste minimisation is the process of systematically reducing waste production. The process covers raw materials consumption, product loss, energy and water consumption, packaging, effluent production, wasted effort, and all other solid, liquid and gaseous wastes.

Companies that reduce the amount of waste produced not only reduce waste management costs, but also save in raw materials costs through reduced resource wastage. Minimising waste can also help reduce environmental liability and insurance costs, and yield income from the sale of reusable waste.

Waste Survey

A waste survey of Metal Casting Cos was undertaken on the 10^th November, 1999. The survey was carried out as an initial review using data collected on site and involved:

• Identifying wastes. A site tour, detailed discussions with site personnel, and observations were used to identify wastes generated by each process/area.
  
  
• Gathering basic quantity and cost data. Historical waste and purchase record data was collated to determine raw materials consumption, waste quantities and disposal costs. Although information gathered from historical data did not cover all wastes (i.e. product loss, handling costs, etc.), it was sufficient to identify opportunities for reducing waste. The majority of waste routes need to be better defined.
  
  
• Identifying opportunities for reducing waste. Using the available data and our experience of energy and waste management, areas of the business where there are opportunities to reduce waste were identified.
  
  
• Identifying legal obligations. All companies have a duty of care to ensure that wasted materials are managed correctly. An assessment of compliance with relevant legislation was also made.
  
  

Recommendations

Processes / Energy / Materials

• Calculation of the scrap metal to ingot ratio in the furnaces may prove useful in identifying wastage. Generally, an acceptable level of scrap metal that can be re-heated is 10% of all metal added to the furnace. Re-heating more than this level could mean an increase in items requiring rework, heating less means that ingots are being wasted.
  
  
• A feasibility study into the conversion of all metal re-heat furnaces to natural gas fired should be undertaken. Natural gas is nearly 100% methane. The combustion of methane is much cleaner than that of gas oil.
  
  
• Gas oil can be wasted in a number of ways such as:
  
  
• Imperfect set up of furnace combustion resulting in emissions of particulates and uncombusted oil vapours
  
  
• Overheating the metal above temperature required to cast
  
  
• Radiant heat losses: such as from molten metal in the open crucible
  
  
• Runners and risers being too large
  
  
• Rework (estimated at 4%)
  
  
• Coupled with a study into the merits of switching to natural gas, the areas of heat loss given above should be considered and where practicable, reduced to improve the consumption of gas oil. (Gas oil consumption figures are given at the end of this report.) Furthermore, technologies such as recuperative burners to utilise the waste heat lost in the flue gases should also be investigated - savings that can be made from the adoption of measures such as this are typically around 40%.
  
  
• It is important that the furnaces are cleaned after each shift in order to improve efficiency - including the removal of the dross from the surface of the metal and the removal of any debris.
  
  
• Furnaces should be relined periodically - perhaps around once every 3 years due to mechanical wearing in the crucible and the flue.
  
  
• The company have recently purchased a new compressor but it currently is not in use. Apart from working more efficiently and using much less electrical energy, using the new compressor will mean that the amount of condensate (mineral oil and water) generated and the associated disposal problems will be considerably reduced. The new compressor has an oil/water separator- the water can be sent to foul sewer and the oil drained into a suitable drum and disposed of as Special waste around 1-2 times per year. Currently, the mineral oil and water is left to drain onto the floor of the factory via and open valve. This is not only wasting expensive air, but is also contravening environmental regulation concerning hazardous waste and discharges of environmentally polluting substances covered both by the Water Resources Act 1991 and the Special Waste Regulations 1996. Disposal of this waste is covered in greater detail under the recommendations given in the later section on waste management.
  
  
• A compressed air survey should be undertaken to:
  
  
• Ensure that all pipework is correctly sized to reduce pressure and distribution losses
  
  
• Implement an appropriate maintenance schedule of the system
  
  
• Blank off redundant areas/isolate areas of low use
  
  
• Identify areas where compressed air tools could be substituted for electrically operated equipment or jobs that could be done by hand - for example, in knocking sand out of the boxes following removal of the cast.
  
  
• Identify all leakages through no load testing and electrical metering
  
  
• Identify the times when compressors can be switched off
  
  
• The lighting system can be made more energy efficient through the gradual replacement of all fluorescent tubes with energy efficient tubes.
  
  
• The feasibility of nightshift work should be investigated to take advantage of the reduced electricity cost.
  
  
• Details of motors on site were not available during the audit. Motors can consume a significant amount of electricity which can be reduced through consideration of the following:
  
  
• Reduction of the speed-through the installation of variable speed drives or rewiring can reduce the speed of the motor
  
  
• The motor may not be sized correctly - average and peak motor loads should be checked
  
  
• High efficiency motors can be installed - these are around 1-4% more efficient.
  
  
• Replacing old motors - the efficiency of motors declines each time they are re-wound
  
  
• A transport improvement strategy should be implemented to:
• Ensure that all vehicles are regularly maintained and serviced (with emissions testing)
  
  
• Look into all possibilities of alternative vehicles and fuel over the next year
  
  
• Assess vehicle use and route planning methodologies every 6 months
  
  
• Improve the fuel efficiency of the entire fleet (including company cars) by 5% over the next two years
  
  
• Encourage at least 50% of all employees to use car pooling systems, public transport, cycling and walking where possible over the next year.
  
  
• Red Sand addition rates should be examined - a target reduction should aim to be less than 2%.
  
  
• The automatic sand mixer should be regularly calibrated to ensure sand and chemical ratios are correct, coupled with a regular sand testing regime. The calibration controls should be secured against any unauthorised adjustment.
  
  
• Contracts should be reviewed regularly for the purchase of sand, binders and additives.
  
  
• Sand to molten metal ratios should be reduced as far as possible. This can be achieved through:
  
  
• Using shaped boxes that follow the casting contours more closely
  
  
• Blanking off the corners of boxes to reduce the amount of sand needed
  
  
• Looking at the thickness of walls and the depth of the sand beneath the casting - using reinforcing wires or bars may be preferential to thick walls
  
  
• The silica sand going to landfill should be segregated as a short term measure from the general waste mixed in the same skip - under the existing landfill tax aggregates and materials defined as inactive 'construction waste' is charged at a lower rate. This will not apply to construction waste that is mixed with general industrial waste such as food wastes, cardboard etc.
  
  
• The reclamation of the chemically bonded silica sand should ultimately be addressed. There are many primary reclamation techniques available, perhaps the most suitable for this site being shot blasting - through loading the mould and the casting into a shot blast machine the mould completely disintegrates and the casting is also cleaned, hence giving it an improved finish for the customer. The sand and shot are then subsequently separated. It is recommended that the company conduct a feasibility study into the purchase of a shot blast machine.
  
  
• Chemically bonded sand can also be used in other industries for example in cement manufacture - this is another alternative to sending the sand to landfill. This should be investigated further.
  
  
• Sand storage needs to be improved. The silo should be waterproofed and the red sand storage area covered. Excessive moisture in the sand can result in delayed strip times, mould distortion on stripping and prevention of curing (in extreme cases).
  
  
• The company should minimise the effects of sand segregation (a change in the particle size distribution) which is a result of the movement and handling of sand. The greatest area where segregation problems occur is through the use of small volumes of sand in the larger continuous mixer and with small batch mixing. Continuous mixing results in striated cores - containing layers of strong or weak sand. With small batch mixing, which occurs only at Metal Casting Cos prior to fresh sand deliveries - the remaining 2 tonnes of sand left in the silo are removed. (This is due to the fact that the angle and height of the silo is such that the bottom portion of sand is unable to feed into the mixer.) In this case, the small mixer in Unit 2 is used. This type of mixing may invariably mean that there will be an occasional weak batch of sand. Modifications to the existing silo or investing in a new silo in accordance with best practice guidelines will optimise silica sand use and cut wasted manpower and energy.
  
  

Waste management

• All loading and unloading areas of sand, oil and chemicals need to be designated, marked out and isolated from the surface water drainage system.
  
  
• The storage yard should be roofed as this reduces the volume of contaminated drainage for disposal. Skips need to be lidded to prevent the escape of wind blown litter and sand.
  
  
• Many pollution incidents are a direct result of poor security. The company should therefore ensure that all gates, doors and valves are locked in both the factory area and external storage facilities. All fenced areas should be made secure and materials should all be stored undercover.
  
  
• Oil and chemical storage areas must be bunded. The bund must be impermeable and be able to hold at least 110% of its contents. Detailed guidance on above ground oil storage: PPG2: Above ground Oil Storage Tanks should be obtained from the Environment Agency.
  
  
• The appropriate spill kits should be stored next to all oil and chemical storage areas, and relevant personnel trained in their use.
  
  
• The oil pipe lines running along the internal walls of the factory should be encased in protective sleeves or ducting.
  
  
• All deliveries of oil need to be strictly supervised by a trained member of personnel, and any spillages isolated immediately with the appropriate material. Tankers should discharge oil via a lockable fixed coupling within the bunded area. Personnel should ensure that automatic cut off valves should be fitted to delivery pipes to prevent overflowing.
  
  
• A chemicals inventory should be devised and kept up to date.
  
  
• The company needs to give consideration to fires and how to deal with contaminated fire water. A first step is through obtaining PPG20: Pollution Prevention Measures for the Control of Spillages and Fire Fighting Run-off from the Environment Agency.
  
  
• Compressor condensate should be disposed of as Special Waste using the consignment note system under the Special Waste Regulations 1996.
  
  
• Dross is also classed as Special Wastes and should be disposed of accordingly. Grinding dusts also may be classed as Special Wastes (particularly zinc) as they are combustible. The Environment Agency will be able to give further advice on this. These metal wastes were collected by a local traveller in the past and subsequently sent to a scrap yard. The location of the scrap yard is unknown as a copy of the site license is not retained on file, and it is highly unlikely that the waste carrier was licensed which is reinforced by the fact there is no supporting paperwork. (Refer to the table of legislation at the end of the report).
  
  
• There is no record of a waste licence on site for the waste contractor - Tom White Waste Limited - a local waste transfer station, for the general waste skip. It is therefore unknown as to whether the company is licensed to remove and store the waste prior to sending it to landfill. Metal Casting Cos do not have copies of waste carrier's certificates which detail a waste carrier's registration - these are important requirements of the Duty of Care provisions under the waste section of the Environmental Protection Act 1990 (refer to the table of legislation at the end of the report). Under this legislation, Metal Casting Cos are also required to keep waste transfer notes on file for at least two years. One delivery note was made available during the audit - which suggests that the transfer may be covered by an annual season ticket - although there was no evidence of this. Furthermore, the delivery note (see Appendix.1) was incorrectly completed by the waste contractor in that it describes the waste as construction, even though it is mixed and should be industrial.
  
  
• Appendix.2 tabulates the responsibilities of each waste holder in relation to the Duty of Care requirements.
  
  
• Training of personnel is required in order to reduce waste. Basic awareness is good, for example employees are diligent at switching off lights and taps although detailed waste management training is necessary to key employees upon improvements being made.
  
  
• A waste costing exercise will enable the company to understand the true costs of its waste. This involves comparing the cost of the raw material in the waste added to the cost of disposal. This is reliant upon more accurate figures than were made available during the audit and is something that the company should consider undertaking in the near future.
  
  

2. Basic cost data

The company's principal resources, waste outputs, quantities and cost (where available) are listed below. This data was collated from historical purchase and waste records. The data is not complete but useful in highlighting high consumption and cost resources and wastes (apart from electrical energy and water used that is charged as a percentage)

3. COMPLIANCE WITH WASTE MANAGEMENT LEGISLATION

Controlled Waste

Part 2 of the Environmental Protection Act 1990 (EPA) defines any waste that comes from industrial, commercial or domestic sources as being controlled waste. The EPA established a duty of care on anyone (except householders) who has control of, or responsibility for, controlled waste at any stage from its production to its disposal.

Special Waste

Certain controlled wastes are considered to be potentially hazardous and require special handling and treatment. The handling of these wastes is controlled by the Special Waste Regulations 1996 (SWR) as amended, which defines a more stringent system of control.

Appendix.1: Responsibilities of each waste holder

*This could involve auditing a waste disposal site for peace of mind (especially where Special Waste is concerned), or following a waste vehicle