Making Good Environmental Choices for Lubricants

Ken Brown, Utility Service Associates
Tags: bio-based lubricants, food grade lubricants, synthetic lubricants

The environmental impact of hydroelectric power stations is becoming increasingly important. In the past, the main focus has been on the physical structures of the dam, how it fits into the environment, and its impact on water flows and fish kills. The maintenance activities of such equipment have considerable environmental impact as well. For example, it takes only a small amount of oil to form a clearly visible sheen that might extend for miles. Fortunately, it is relatively easy to reduce the impact by changing the way lubricants are being used. This article is an overview of some of these considerations.

Making good environmental lubricant choices does not have to compromise equipment reliability or functionality. In fact, appropriate environmental decisions can be part of a first-rate, cost-effective design. The design aspects include the equipment itself, maintainability, economic life span, ergonomics, operation and eventual removal. Removal does not necessarily mean disposal, because there may be some recoverable value left in the machine.

For example, oil in equipment should not be changed unless it has reached the end of its useful life. This is typically not the case, because the oil is often changed based on an arbitrary time criteria or because of contaminants such as water or dirt. These contaminants can normally be removed with the proper equipment.

A longer oil lifecycle not only contributes to less liquid waste, but there are other benefits as well: cost savings because labor can be used more effectively elsewhere, and fewer shutdowns for oil changes. These added costs can amount to at least five times the price of the oil alone. In addition, not having to drain the old oil, move it for disposal and bring in new oil also means less chance of spills. Spillage can often occur when a pail is knocked over or a drain valve breaks off.

Product Effectiveness
For a lubricant to be most effective, a number of correct decisions must be made throughout its service life, such as the following:

Initial Selection
Selecting the proper lubricant is important to sharply reduce long-term costs. The best-fit product selection can mean longer lubricant life, reduced machine wear, reduced incipient power losses and improved safety. Suitable basestocks and additives reduce environmental impact. This is important because there will be leaks, spills and eventual disposal. Table 1 illustrates examples of alternative selections.

 
Mineral Oil
Glycols
Vegetable
Oils
Synthetic
Esters
Density At 20°C
(kg/m3 )
880
1100
940
930
Viscosity Index
100
100 to 200
100 to 200
120 to 220
Shear Stability
Good
Good
Good
Good
Pour Point (°C)
-15
-40 to +20
-20 to +10
-60 to -20
Cold Flow
Properties
Good
Very Good
Poor
Very Good
Miscibility with
Mineral Oil
-
Not Miscible
Good
Good
Solubility in Water
Not Miscible
Very Good
to Poor
Not Miscible
Not Miscible
Seal Swelling
Tendency
Slight
Shrinking
Indifferent
Fair
Behavior
Against Paint
Good
Poor
Good
Good
Biodegradability
(CEC) %
10 to 30
10 to 99
70 to 100
10 to 100
Oxidation Stability
Good
Good
Fair
Good
Hydrolytic Stability
Good
-
Poor
Fair
Sludge-forming
Tendency
Good
-
Poor
Fair
Relative Cost
(Mineral Oil =
1
2 to 4
2 to 3
4 to 20
Table 1. Biodegradable Fluids

With the right lubricant, there is a greater likelihood that a product can later be used elsewhere in less demanding applications. The correct choice might be synthetic lubricants, lubricants with different additives, or biodegradable products and/or products with less environmental impact. The best product selection for each application varies, depending upon the equipment specifics. For example, some synthetic lubricants might not be compatible with the equipment construction materials. In some cases, good separability from water may be required, while good solubility is preferred in others. See Table 2 for typical fluid characteristics.

Use Current Product “Green” Options Advantages
Bearings on
Electric Motors
and Pumps
Lithium-thickened
mineral oil
Synthetic oil
with a complex
thickener
Less torque in winter
and less oil loss in summer.
Possibly longer
relubrication intervals.
Can also be more
biodegradable.
Motor Oil in
Vehicles or
Equipment
10W30 mineral oil 5W30 with 50%
or similar recycled
mineral oil
Energy and fuel savings,
less wear and using
a recycled oil.
Transformer Mineral oil Synthetic
ester-based fluids
Readily biodegradable
and better fire resistance.
Gearboxes ISO VG460 synthetic
PAO oil
Energy savings, potentially
longer service lives and
less need for heating in
winter and cooling in
summer.
Wicket Gates
Mineral oil-based
grease
Canola oil-based Base fluid is vegetable oil
that is renewable, can be
readily biodegradable
and less ecotoxic.
Wire Ropes Asphaltic solvent
cut back mineral oil
Vegetable- or
ester-based oils
and calcium
sulphonate
thickeners
Less polynuclear aromatics
and less solvent. Can have
better corrosion
protection.
Table 2. Environmentally Friendly Lubricant Choices

Product selection from an environmental perspective is a bit more complicated. One must consider a number of factors such as: whether the base materials are from renewable resources, how much energy is used and/or waste produced during manufacture, safety, efficiency, biodegradability, the end products, ease of maintenance, service life, waste handling and the product’s ecotoxicity. While the required information should be readily available, (if not, this should be a red flag), interpreting such information is not as straightforward. At first glance, one might think an H1- or H2-designated food-grade grease would be better, but this is often not the case. Many are not AW- or EP-rated, so there might be more wear, and many are just as bad for the environment. For example, zinc oxide used to give the white coloring in greases is not good environmentally.

Equipment Design
Eliminating conditions such as hot spots and air entrainment, as well as providing a good ergonomic design, will reduce the stresses on the lubricant. Proper and effective maintenance is the key for maximum performance from both the equipment and the lubricants.

 

Equipment should have adequate seals to prevent the ingress of contaminants and reduce lubricant loss. Breathers should have adequate provisions for filtration to remove particulates and contact-type shaft seals should be selected based on lifecycle and durability. These kinds of features help extend the life of the lubricant and the equipment. Proper component selection and configuration can also mean lower temperatures and possibly less auxiliary equipment such as coolers or heaters.

Reducing Liquid Waste and Cost
Industrial lubricant lifecycles can be extended dramatically from typical annual lifecycles if the lubricant is managed effectively in the sump. To get maximum value from the oil-lubricated components, keep the oil cool, clean and dry. For self-contained sumps this can simply mean ensuring that make-up oil is added properly, that the breathers are adequate and operational, and that any cloudiness is corrected. For circulating oil systems, ensure that the make-up oil is not a source of contaminant. In most cases, side-stream filtration, either continuous or intermittent, can be deployed to control these factors.

Condition Monitoring
Lubricant condition monitoring (oil analysis), is critical for safe lifecycle extension. Analysis serves three main purposes: First, it ensures that the right lubricant is in place. Viscosity, additive content and acid number are all telltale indicators of lubricant mixing. Some types of cross contamination become immediately evident. For example, even a slight amount of combustion engine oil mixed into the turbine circulating oil will destroy the turbine oil’s ability to shed water. Extreme pressure additives may be necessary in some cases, while the same additive may be detrimental in others. Generally, they shorten service lives or present additional considerations for materials such as for the plastic cages in bearings.

Secondly, machine condition monitoring, when done in conjunction with lubricant condition monitoring, provides a long-term view into the health of the production asset. An advantage of lubricant-based analysis is that it detects machine problems in the oil before the problems are manifested in the equipment. Other analysis methods, while certainly beneficial, measure for damage that already exists at a level which almost always requires repair.

This is important, as the goal is not to save the oil, which is typically inexpensive, but rather to prevent damage to and extend lubricant component lifecycles. Even an inexpensive shaft bearing will require taking that equipment out of service to be replaced.

Lastly, oil testing determines what is required to keep it in good condition. This can be purification or additive supplement through sweetening (bleed and feed). When contamination exists, it is usually an advantage if the lubricant can be treated while still in the equipment so an outage will not be required.

Taking Action

  1. Equipment Design. Request technical assistance to ensure that the equipment selection has been optimized for environmental and tribological considerations.

  2. Selection of Material. Product selection can include additive packages, long-life lubricants, recycled oils, or biodegradable or environmentally friendly products.

  3. Maintenance. Consider specialty maintenance items to reduce liquid waste and improve sampling procedures. Review condition monitoring testing, particularly the results and successes. Periodically perform a lubricant survey. Set up guidelines for conducting a proper failure analysis, including lubrication failure modes and effects analysis.

  4. Condition Monitoring. Quick on-site tests can usually determine if the oil requires treatment or if the machine is in distress. Proactive oil testing prevents damage. In contrast, most other testing/monitoring methods require some damage to have already occurred.

  5. In-situ Treatment. A lubricant can often be effectively treated while still in the equipment, and in many cases can remain on-line. Caution should be exercised to prevent inadvertent contamination of the sumps from oil previously treated with the filtration equipment, if required drain housings and hoses have separate ones for turbine oils or phosphate esters.

  6. Reuse or Disposal. Cost-effective alternatives to disposal are offered because the fluid can often be used in less-demanding applications either on-site or in other industries. For example, mineral oil could made into a cutting fluid or recycled.

  7. Training. Correct actions require decision makers to be fully aware of their actions, nonactions and alternatives. Products, equipment and rules change quickly and necessitate periodic updates. Consider asking suppliers to give presentations or arrange for industry experts to provide specific training. Ongoing, two-way communication is a must.

  8. Persistence. Last but not least, it is important to show that efforts have been made to reduce the environmental impact of operation and/or spills. While this might not prevent charges from being levied if there are spills, it can reduce the likelihood of problems and/or reduce the environmental consequences.

Consider what your company or plant site has done to address the following:

  1. Demonstrate effort and findings to reduce the likelihood of chemical or petroleum releases.

  2. Demonstrate initiatives to reduce risk and consequences of spills.

  3. Demonstrate initiatives to reduce the impact of releases and spills.

  4. Verify efforts to maintain hazard compliance.

It should be easy to make improvements by taking advantage of one or more of the options in the previous section. This provides a win-win situation because not only can the equipment run better, but there is less environmental impact.

There are many reasons why better products are not used. Often the plant staff is not aware of how easy it can be to choose better lubricants. The plant is often locked into one supplier, with limited options from that supplier.

In some instances, the “credit” attributed to the site for use of a green product outweighs the performance value of the lubricant in the machinery. In this case, the perception can be that the maintenance department is forced to use products that make maintenance and machine condition management more difficult for a political benefit that is given to another department. This might still be the case for some “green” hydraulic fluids that have shorter service lives, but in other cases, the correct “green” lube can perform just as well or even better. If a machine part fails because of lubrication, it is often a simple remedy to prevent it from happening again. Making “green” product choices for the application is an added consideration.

Alternatively, maintenance might find a superior performance green product alternative, but have to pay two to three times more to use the product. As an incentive, incrementally higher costs attributed to the use of “green” product choices could come out of a separate fund, at least for the first few years.

Recommendations

  1. Know the products and equipment and use them wisely.

  2. Know what you are using, and know how to track it from cradle to grave.

  3. Have financial objectives in place that actively support the use of energy-saving green and/or cost-saving products.

  4. Do not compartmentalize the decision-making process so much that initiatives die. Let a champion go with getting support or direction as required.

  5. Talk to industry/government resources before embarking on new project. Do not do the wrong thing for the right reasons. It is beneficial to use existing technology and resources.

References

  1. Bergstra, R. “ Green Means Go .” LubesNGreases, November 2004. p 36-42.
  2. Fulton, E. “ Using Environmental Friendly Lubricants at Hydro Stations.” Hydro Review , May 2000. p. 10-12.
  3. “ Biobased Lubricant. ” EPA EPP (Environmentally Preferred Purchasing) Update, Update 10, January 2002. f
  4. “Going Green.” International Water Power & Dam Construction, August 2004.
  5. Brown, K. ” The Green Way to Lubricate.” Renewable Energy 2004. p 55-57.
  6. Hanna, L. and Pugh, C. “ Environmentally Safe – Green Lubricants for Wicket Gates. ” U.S. Bureau of Reclamation, Denver, Colorado

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