Ecological conservation and environmental concerns have become a much greater influence in production facilities around the world in recent years. Concerns with environmental protection can also be found in the heart of major industrial operations such as steel mills, paper mills, sugar mills and processing plants. Conservation, oil reclamation and recycling of used oils can be a profitable and environmentally beneficial activity.
The engineering or technical manager of a large plant is often so busy managing production and ensuring optimal production with minimal downtime, that he does not have time to concern himself with the service life of oil that operates the plant machinery. After all, the plant’s purchasing department looks for the lowest priced oil and the handling/storage department ensures that all drained lube oil is disposed of via a waste removal company.
Various local, state and federal authorities have set regulations for the handling and disposal of used oil products. The U. S. Government’s Environmental Protection Agency (EPA) has also issued its own used oil management standards, and companies are required to comply with them.
Reclaiming oil accomplishes the following:
- Conserves a valuable resource;
- Prevents contamination of the environment;
- Saves money by reducing waste disposal costs; and
- Reduces long-term liability for disposed products – from beginning to end.
When to Reclaim and When to Recycle Oil
Oil Reclamation vs Oil Recycling
Oil Reclamation and recycling are two related processes, but there are significant differences between them.
Oil Recycling As an Option
The plant engineer does not have to be concerned with the details of the technology used by a recycler, and therefore, is not the focus of this article except to provide guidelines for its use in the plant. It is important to ensure that recycled lubricants are handled and processed in an environmentally acceptable manner. Ask the removal company to show an independent environmental audit of its site and processes. Ensure the company is licensed to process used oil and make regular visits to the site.
Reclamation treats a specified amount of used oil, preferably on-site, and returns the oil to the machine it was operating in for continued use. An example of this is the reclamation of transformer oil, hydraulic oil and turbine oil. Reclamation may take place off-site where the vendor of the reclamation service drains the existing oil and replaces it with previously reclaimed oil. Oil Reclamation generally involves cleaning, drying and perhaps adsorption to remove dark color, acids and sludge. The reclaiming of used oil is essentially a non-chemical process that restores oil for reuse in a lubricating or insulating system.
All oil products eventually reach the end of their useful service life and must be drained from the machine or system, whether it is in an engine, a gearbox, a hydraulic system or in a turbine. Oil that is recycled could be rerefined to new base oil or treated and sold as fuel oil.
Focus on Oil Reclamation. Traps of Oil Reclamation
Hydraulic oils, transformer oils and to some extent turbine oils, lend themselves to being reclaimed. But, one must ensure that the oil’s performance characteristics and specifications have not been downgraded after reclamation. Reclamation usually involves the used oil being filtered and the removal of debris, sludge and fine particles. Centrifuging is used to remove suspended particles and some water. Many transformer oil reclamation units dry the oil and achieve this by heating the oil and applying a vacuum to pull out moisture.
Transformer oils are frequently reclaimed through filtration. This may take the form of centrifuging, vacuum dehydration or absorption with fuller’s earth or another activated media. When considering a reclamation service for transformer oil, check the following:
- Service providers should offer references of successful reclamation of transformer oil at other companies. Ask to contact previous clients;
- Decide on the performance target for the transformer oil in consultation with the oil supplier or an independent consultant;
- Test the oil before and after reclamation to ensure compliance with your target;
- Ask for a certificate of analysis after reclamation; and
- The certificate should show breakdown voltage, moisture content, acid neutralization number and power factor.
Great care must be exercised with turbine oil when carrying out the reclamation process. Centrifuging and filtration will remove particles and water, but the turbine oil must continue to perform its task of cooling, sealing, lubricating and corrosion prevention. Even though the application is critical, turbine oil volumes warrant the reclamation effort.
The key to turbine oil reclamation is evaluating its performance under specified test procedures. Turbine oil is reclaimed by a combination of filtration, sweetening with fresh oil and sweetening with additives. The combination results in the removal of fine particles, sludge and water, and restoring the performance level.
When considering a reclamation service for turbine oil, check the following:
- Ensure lube supplier works closely with you on testing;
- Obtain a test certificate on the performance of the new oil;
- Test reclaimed oil prior to refill to ensure compliance with performance target;
- Check compatibility. Ten to 15 percent of the old oil can remain in a turbine system.
- Perform quality tests through an independent lab to verify beginning and ending oil condition and performance capability; and
- Verify oil performance after reclamation with bench tests such as Rotating Pressure Vessel Oxidation Test (RPVOT) (ASTM D2272), viscosity, AN, foam, demulsibility and color.
Hydraulic Oil Reclamation
Hydraulic oils are a complex mixture of carefully selected base oils and specific additives.
Top-tier hydraulic oils, often called anti-wear (AW) hydraulic oils, must meet performance specifications set by original equipment manufacturers (OEMs). They must also meet standards set by hydraulic pump makers and standards organizations such as Deutsches Institut für Normung (DIN) and the American Society of Testing and Materials (ASTM).
Plant engineers are increasingly interested in extending the service life of hydraulic fluid. As a result, suppliers and consultants are often asked ways to carry this out. Because of their high-pressure operation, hydraulic fluids tend to accumulate silt. Silt must be eliminated to avoid valve sticking and polishing wear. Hydraulic oils and fluids are reclaimed by a combination of filtration, vacuum dehydration and adsorption. The combination results in the removal of fine particles, sludge and water, and restoring the performance level of the fluid.
Traps of Oil Reclamation
When considering a oil reclamation service for turbine oil, check the following:
- Ensure reclamation vendor can show proof of previous success;
- Obtain from the vendor a certificate of analysis at the end of the reclamation. Compare this to the condition of the oil before reclamation;
- Be sure you understand the performance capability of the new oil and the performance requirements of the OEM. Test against those standards;
- Perform quality tests through an independent lab to verify beginning and ending oil condition and performance characteristics; and
- Test certificates/records should be filed for the next oil change.
After finding a reputable and trusted reclamation vendor, the key is to assemble a team to manage the process.
The Reclamation Team
Managing used oil recycling or reclamation is often left to an individual or is completely neglected in a plant. It is useful to form a team to focus on the process if there is sufficient volume of used lubricating or process oil at the site to justify reclamation. A recycling and reclamation team may consist of a buyer, lubrication engineer, maintenance engineer, oil supplier representative, a reclamation company representative and an environmental officer. They work together to improve the recycling program. In doing so, they compile the information found in Table 1.
The manager of the plant will have to make a decision between reclamation and recycling for his used lubricants and process oils. Because lubricants have different processing requirements, some lubricants are not good candidates for reclamation. The waste oils should be broken into two categories, for either reclamation or recycling.
If it is not clear whether the used oil stream is a good candidate for reclamation, contact the reclamation company and ask whether the specific product, by product name, can be reclaimed.
Candidates for consideration may include:
- Cutting fluids;
- Hydraulic oils;
- Turbine oils;
- Transformer oil;
- Spent lube oils; and
- Engine oils and gear oils.
Using Recycled Oil
Reuse of waste oil can include:
- Burning without treatment – not advised;
- Reprocessing to industrial fuel;
- Re-refining to new oil; and
- Disposal to landfill – avoid at all costs.
Note that the EPA has specified that used oil that does not meet the following criteria must be classified as “Off-Specification.” This used oil may be used as a fuel only in an industrial facility registered with the EPA. These include cement mills, lime kilns, coke ovens and blast furnaces.
If the halogen content is greater than 1,000 ppm, then the used oil must be managed in accordance with the Federal Resource Conservation and Recovery Act (RCRA) hazardous waste regulations. While all lubricants eventually reach a condition where they can no longer be used and must be discarded as used lubricating oil, the plant engineer can examine the following options for minimizing the volume of used oil generated:
In-line oil sensors to ensure that oil life is extended and unnecessary oil changes do not occur.
- Use of oil mist lubrication on industrial gear boxes and other equipment;
- Choice of extended drain period diesel engine oils for fleets;
- Selection of equipment with reduced oil volume sizes;
- Improving the filtration of the lube oil charge and dosing with additives; and
- Prevention of oil contamination.
Every plant should have a coordinated plan for managing used lubricating oil. Cleaner production methods and waste minimization should be the first initiatives in reducing waste oil at a factory. When lubricating oil reaches the end of its projected service life, it must be either reclaimed or recycled.
If reclaimed, the lube oil may continue to serve its intended function for many more operating hours. Rigorous testing and record-keeping are necessary for this approach. If the waste oil is a mixture of contaminants and spent oils, then the used lube oil can be reprocessed by a contracted recycler, keeping within local government regulations. Every business should keep track of the used oil it generates once it leaves the plant. Plants that generate large volumes of used oil should seek an independent report on the process practiced by their contracted recycler.