w. Chesterton Company with others in industry with regards to the

Transcription

1 - Senior Applications Engineer -24 '1 CASE STUDY OF THE A.W. CHESTERTON COMPANY Sandra Pomer Technical Products Division A.W. Chesterton Company 2-boe Pa F ABSTRACT The purpose of this case study is to share the experience of the A. w. Chesterton Company with others in industry with regards to the process of replacing l,l,l-trichloroethane in a vapor degreasing operation to a more environmentally acceptable aqueous cleaning process. The case study covers the entire process from conception to disposal, including process maintenance. BACKGROUND A.w. Chesterton has been a world wide manufacturer of quality products for over 100 years. The company now has five divisions including Mechanical Sealing Devices, Advanced Pump Systems, Mechanical Packings/Live Loading, Technical Products, and Arc Polymer Composites. Chesterton believes in Total Quality Management and Continuous Improvement of it's people and processes. As evidence of this IS certification was received in June of Chesterton has committed its research and development staff to developing the most environmentally sound products possible. Chesterton has also given the manufacturing department the task of reducing hazardous waste and eliminating ODC's (Ozone Depleting Chemicals) from its processes. This case study is focused around the process degreasing method used in the Advanced Pump Systems Division manufacturing process. The previous method of cleaning pump parts after the machining process invoived the use of a vapor degreaser utilizing TCA (l,l,ltrichloroethane). It was necessary to find an alternative cleaning method before the May 15, 1993 deadline of the Clean Air Act which mandates the labeling of any products manufactured with the use of ODC's. These labels would not fit Chesterton's profile of being an environmentally responsible company. The task of finding a replacement was given to the production manager responsible for the vapor degreasing operation. The manager approached the task of finding a replacement for TCA by looking for a drop in replacement solvent that could be used in the existing vapor degreaser. He soon found out that there were none that could fit the bill without significant health effects. Through interviews with industry experts, he discovered that there is a tremendous push in industry to Convert solvent users to aqueous cleaning operations. Approximately 70% of ODC users will convert to water based systems. The other 30% will choose alternative solvents or choose to not clean. Water based cleaning systems are the way of the future for several obvious reasons. Water based cleaners are biodegradable, significantly less toxic and easier to dispose of than traditional cleaning solvents, and are non flammable. INFORMATION GATHERING When approaching the task of ODC replacement, an audit should be conducted of the current operation. It is important to find out what is right with the current process, and then use this information tc 486

2 determine a suitable replacement. Formation of Team It makes the most sense to use a team approach to ODC replacement. This ensures that all needs are being satisfied. The Chesterton team was composed of five key people: an environmental officer, a process engineer, an application chemist, a production worker, and the department manager. Each person plays a key role in the changeover process. * The environmental officer ensures that the selected replacement method meets the company's environmental, health, and safety standards. * The process engineer and application chemist ensure that the chosen method is technically sound and able to handle the production load. * The production worker or the person responsible for the day to day operation of the replacement system is probably the most important member of the team. Getting this person involved in the very beginning of the project will lead to a willingness to change his daily activities and take on ownership of the new operation. * The manager is important because he has the buying power and gives synergy to the team. All of the above team members play important roles in a well balanced operation with the ultimate goal being total new program acceptance from all departments involved. EVALUATION OF THE CURRENT CLEANING PROCESS One of the biggest road blocks to replacing TCA in a vapor degreaser is that it is almost too efficient. The general attitude is, why fix it if it isn't broken? Environmental reasons aside, what makes TCA a good cleaning solvent? TCA is non flammable, fast evaporating, has excellent solvency, is relatively safe for workers health, and cleans most types of metals. The vapor degreasing equipment is also very simple and effective at degreasing metal parts because it is an easy one step process, has a small footprint, and can clean a large variety of different parts in the same batch. Soil Reduction Sometimes we cannot see the forest through the trees. It is often helpful to take a step back from an operation to look at the big picture and ask if there is something further back in the production process that would make cleaning the parts easier. Is there a way to reduce the number of soils to lessen the cleaning load? Usually this means reducing the number of machining fluids used to form the parts. The machine shop at Chesterton had what was called the "Wall of Coolants". There were at least 10 different coolants due to user preferences. There were heavy petroleum oils, water soluble oils, and full water soluble synthetics. Each coolant would have to be treated as a different soil in the cleaning process. It made sense to reduce the coolants to as few as possible. After much testing, the entire shop was reduced to two coolants, a water soluble oil and a full synthetic. Both Of these coolants would be much easier to remove with water based chemistries than the heavy petroleum oils. 487

3 Parts Configuration When converting to aqueous cleaning methods, the configuration of the parts being cleaned becomes very important. The size and shape of the parts will play a key factor in determining which type of equipment will used for the cleaning process. The parts being cleaned in the Pump Division were varied in size and shape. The smallest part was four inches and the largest was three feet. Some parts had deep holes and some had occluded areas and caverns. ~ l of l these different parts had to cleaned using the same process. Substrates Different metals present their own cleaning problems when switching to water based chemistries. One of the main concerns is the possibility of flash rusting in ferrous metals like cast iron and mild steel. In the Pump Division at Chesterton, three base metals had to be cleaned by the same process. The metals were stainless steel, cast iron, and mild,steel. The stainless steel does not rust. However, the cast and mild steel were very susceptible to flash rusting, which presented another variable in the cleaning equation. The process and chemistry chosen had to have a built in safeguard against this particular problem. Space Consideration Converting from solvent vapor degreasing to aqueous systems usually involves more equipment because the parts may have to be rinsed and dried after cleaning. The added equipment usually requires additional floor space in the factory. At Chesterton, the factory space was at a premium and the first choice was be for the new equipment to fit into the existing space then occupied by the vapor degreaser. However, additional space was available if absolutely necessary. Time Allowed for the Cleaning Process Some manufacturing processes have a limited time window available for the cleaning process. It would be ridiculous to be evaluating a system that requires 10 minutes to clean the parts when there is only an 8 minute time window allowed in the manufacturing process for cleaning. Generally speaking, aqueous cleaning requires more time than solvent cleaning because there are usually more steps involved. ie. rinsing and drying. However, there are many technologies available to keep the added time to a minimum like using heated solutions and adding automation to the cleaning process. At Chesterton, the cleaning process was very flexible. The production people were willing to make- the necessary adjustments to achieve the same results they were getting with the solvent vapor degreasing operation. Cleanliness Requirements Cleanliness requirements will differ from application to application. Many times parts are over cleaned or do not have to be cleaned at all. To determine cleanliness requirements, it is important to know what happens to the parts after they are cleaned. For example, 488

4 *the parts are sent to a customer who cleans the parts upon their arrival, why are they being cleaned twice? Leaving the machining fluid.on the parts could help to protect the parts from corroding during transportation. Also, not Cleaning the parts would help to reduce manufacturing costs. The pump parts at Chesterton are coated with an epoxy enamel after the cleaning process. Therefore, a low residue level was required, but it was not necessary for the parts to have llzeroll residue. The paint used could tolerate slight rust, but it was optimal to keep rusting to an absolute minimum. TESTING Laboratory Testing After all the preliminary information is gathered, The next logical step is to perform some laboratory testing. Several tests should be performed based on the information gathered at the audit. Due to the parts configuration, it was determined that immersion cleaning would be best for this operation to reach all areas of the parts. A small laboratory bench top dip tank was used to test various chemistries, concentrations, temperatures, and time for the soil to be removed from the substrates. Controlled humidity chambers were set up to determine flash rusting potential of the different chemistries tested on the ferrous metals. Because the parts were being coated after the cleaning process, samples of the epoxy paint were obtained to perform ASTM D Adhesion by Tape Testing, commonly referred to as The X-Hatch Adhesion Tape Test. This testing would determine if the residue left behind by the cleaner would interfere with the coating process. In Process Testing - Testing Done at Beta-site After preliminary laboratory testing was performed, it was logical to take the recommended process for a "test drive". Usually a local beta-site that has the desired cleaning equipment can be located by an equipment manufacturer and made available for testing. Another option is to rent the desired equipment for testing purposes. Usually, the rental fee is deducted from the purchase price if the equipment is purchased. The reason behind the Vest drive" is to evaluate the equipment and to achieve a relative feel for the actual cleaning process. The team located a system that was available for beta-testing within an hour's drive from the Chesterton factory. Several soiled parts and the recommended cleaner were taken to the site. The day was spent cleaning parts, optimizing concentration and temperature, and determining correct cleaning time for the cleaning process. At the end of the day, the team decided to purchase the equipment and move ahead with the project. There were no doubts about the new process. This was clearly the right equipment and chemistry for the application. PROCESS RECOMMENDATIONS BASED ON TESTING RESULTS Approaching a conversion process ir. a scientific fashion has many 489

5 benefits. Much of the guess work is removed from the process and there is no doubt in any team member's mind that the chosen system will not work. Also, by doing the testing up front, down time is virtually eliminated and the change over of the cleaning process will not impact the total manufacturing operation. Based on the laboratory and beta-site testing results, the following recommendations were made for the Pump Division: * Equipment - Agitated, heated dip tank $18, gallon capacity 2000 pound capacity loading tray Bag filter Automated temperature controls Hydraulic lift cover * Chemistry - Moderate alkaline aqueous cleaner Concentration at 5% ph is 9.8 Contains no phosphates, butyls, or caustics Accepted by the Chesterton Environmental Health t Safety Dept. * Temperature F * Time in tank - 8 minutes * No rinse required based on the results of the X-hatch adhesion testing * Factory air used to dry parts to help reduce flash rusting Purchase, Installation, and Start-up of New Equipment The in house maintenance Staff at Chesterton was used to install, plumb, and vent the new equipment. The technical staff was also present at the start-up of the new equipment and the first production batches to work out any system bugs or unforeseen problems, The results were very positive. Production cleaning was in place on day one of the new operation. The vapor degreaser was removed, the new equipment was slid in its place, and production was never interrupted. The whole changeover process was transparent to the manufacturing process. PROCESS MAINTENANCE The average bath life of the aqueous cleaning system is six to eight weeks. Routine oil skimming of the dip tank helps to reduce soil loading of the cleaning solution and prolongs the bath life, The team is currently evaluating micro-filtration units to further extend the bath life. DISPOSAL OF SPENT CLEANER The Chesterton facility operates on a septic system and the town does not allow any discharge to the ground water. This is due to the fact that the previous site inhabitants, a shoe manufacturer, caused two of the town's wells to be shut down because they released 1,1,1- trichloroethylene, a potential human carcinogen, into the ground water. The options left open to the company were limited. Fortunately, there was an evaporator in house used to evaporate other aqueous fluids like synthetic machinery coolants and cleaning fluids. A sample of the spent cleaner was submitted for testing. It was found that there were no VOC's (Volatile Organic Compounds) present. Theref ore, the spent 490

6 eaner was found to be acceptable for evaporation by local authorities'. COST SAVINGS The real cost savings associated with making the change to aqueous cleaning systems is in the disposal of the spent cleaner. Previously, the cost of disposing the TCA was $150.00/55 gallon drum and increasing rapidly. Presently, it costs approximately $1.20/55 gallon drum to evaporate the spent aqueous cleaning solution, a considerable cost savings. The waste reduction is estimated at 96%. The overall savings to the A.W. Chesterton Company is estimated at $100, annually. As a result of this dramatic reduction in waste, the Chesterton company has been recognized by the Environmental Protection Agency as being a model company for their efforts to minimize hazardous waste. 491