Going green27 August 2004
It is relatively easy to reduce the environmental impact of maintenance activities at hydro power plants by a series of measures relating to the lubricants being used, says Ken Brown
THERE IS a growing need to take into account the environmental impact of hydro power plant operation. In the past, this has focussed mainly on the physical structures of the dam and how it might fit into the environment and the impact on water flows and fish kills. However, maintenance activities of equipment can also have considerable environmental impact as can ‘accidents’ causing oils spills and even normal operational activities can carry a risk if lower impact materials are not used. For example, the commonly used mineral oil based lubricating oil and transformer fluids can have a significant impact if spilt on the water or even on the ground. These can require considerable clean-up costs and can involve significant loss of good will. In an effort to reduce the risk of damage to the environment and contamination of water, some hydro plant owners have turned to environmentally friendly greases, oils and hydraulic fluids, as well as modifying their O&M activities to minimise risk to the environment.
Making lubricant choices that are good for the environment does not have to mean compromising the reliability of equipment or functionality. In fact, correct environmental decisions should be a part of a good cost-effective design. The design aspects can include the equipment itself, maintainability, economic life span, ergonomics, operation and lastly, eventual removal. The latter does not necessarily mean land fill, because depending on the specifics, there may still be some recoverable worth.
For example, it does not make sense to change oil in equipment unless it is really at the end of its useful life. Unfortunately, this is usually not the case, because the oil is often changed solely on an arbitrary time criteria or because of contaminants such as water or dirt. These contaminants can usually be easily removed with the right equipment. This is also not overly expensive but the proper equipment has to obtained. For example, a good oil filter cart that can be used for oil cleaning and topping up might cost US$1500-2000. This should have wheels for ease of transport, a beta rated filter element, a filter condition indicator, pin type sample valves, automatic housing air bleeds, good hoses, quick disconnects, a screw type pump (to prevent emulsifying water), and a good quality finish.
Not only does using oil for longer periods mean that less liquid waste is produced, but there will also be cost savings because labour can be used more effectively elsewhere, new oil will not have to be purchased, and equipment does not have to be shut down for an oil change. These added costs can amount to at least five times the price of the oil on its own.
However, to be fully effective, a number of correct decisions must be made throughout the life of the product.
Selecting the proper lubricant in the first place is very important to the reduction of later costs. The correct product can have a longer life, reduce wear, reduce power losses, and it can be safer. In addition, with suitable basestocks and additives, any environmental impact can be reduced. This is important because there will inevitably be some leaks and spills, and there will be the need for eventual disposal. Some examples of alternative selections are shown in Table 1.
Furthermore, with the right choice, there is a greater likelihood that a product can later be used elsewhere in less demanding applications. The correct choice might be synthetic lubricants, it might be different additives, and in other cases it could be biodegradable products and/or products with less environmental impact. A decision matrix has been proposed for a European Community environmental evaluation.
However, while the best choices for each application can vary according to the specific circumstances, all the choices must work satisfactorily in the equipment that needs to be lubricated. For example, some synthetic lubricants might not be compatible with the materials; in other cases, good separability from water might be required or good solubility might be needed. Typical fluid characteristics are shown in Table 2.
The environmental issues are more complicated, because it is important to take into account a number of factors including:
• Whether or not the base materials are from renewable resources.
• How much energy is used and/or waste produced during
• Are they safe to use?
• Will they work?
• Do they biodegrade and what are the end products?
• Are they easy to maintain?
• Is the service life better?
• How is waste handled?
• What is the ecotoxicity?
Fortunately, doing something better can be very easy, whether it is by making better use of a current product or picking a new one. However, for the latter, it is very important to address all the issues. For example, food grade lubricants are not necessarily better environmentally and the ones that are white for cosmetic reasons often contain a significant level of zinc compounds. These can actually be more detrimental.
Eliminating conditions such as hot spots and air entrainment will reduce stresses on the lubricant. In addition, providing a good ergonomic design can help meet the axiom that: ‘If you want it done right, make it easy to do it right.’ This is because proper, and hence effective, maintenance is the key for both the equipment and the lubricants. In addition, equipment should have adequate seals to both prevent the ingress of contaminants and to reduce lubricant loss. Breathers should have adequate provisions for filtration to remove particulates and contact type shaft seals should have as long a life as possible. Non-contact labyrinth seals are more cost effective in many cases. Better care will help extend the life of the lubricant and that of the equipment if the wear cycle can be broken. Proper components can also mean lower temperatures and possibly less auxiliary equipment such as coolers or heaters. These can be high maintenance items, especially at older stations, because valves will stick, coolers will plug or leak, and thermostats or heaters and/or coolers will fail or leak. A recent oil spill was because the water in an oil cooler froze.
Reducing liquid waste
First, try to extend the life so that less waste oil is generated. Fortunately, industrial oils seldom wear out, so in order to get the best out of the oil and of the oil-lubricated equipment, one goal should be to keep the oil clean and dry. For self-contained sumps, this can be as simple as ensuring that make-up oil is added properly, that the breathers are adequate and working, and that any cloudiness, such as from water, is corrected. For circulating oil systems, it is also important to make sure that the make-up oil is not a source of contaminant. In most cases, effective use can be made of inexpensive but good equipment to remove dirt and/or water. These can be either off-line or on-line filtration and either continuous or as required.
An important aspect of extending the lubrication service life is condition monitoring. This serves three main purposes. First, to ensure that the right lubricant is in place, because when starting to do such checks, it is often found that oil of the wrong viscosity has been used. Such tests can also determine if the right oil is being used. For example, a hydroelectric turbine oil will destroy the required ability to separate out water. Similarly, in some cases, extreme pressure additives may be necessary while in others, such as rolling element bearings, they can actually reduce fatigue life or reduce the maximum operating temperatures of plastic cages.
Secondly, it is important to know how the oil-lubricated equipment is. A major advantage of oil testing is that you can detect problems in the oil before it shows up in the equipment. Other methods have to wait until there is damage. This is very important, as the goal is not to save the oil, which is usually very inexpensive, but to prevent consequential damage to bearings and/or gears. Even the cheapest shaft bearing will require an outage for replacement.
Lastly, by testing the oil, it can be determined what is required to keep it in good condition. This can be filtration, purification, sweetening, or, with large systems, re-inhibition with additives. The advantage is that if you do not have to change it, uptime is maximised and waste oil generation is minimised.
However, even when there is contamination, it is usually an advantage if the lubricant can be treated while it is still in the equipment so that an outage is not required. The treatment process is simpler if the lubricant is not mixed with other products or inadvertently contaminated.
Portable equipment is available that can usually be taken right up to the oil to be treated.
Review or obtain technical assistance to help ensure that the selection of equipment has been optimised for environmental and tribological (i.e. friction, wear, bearings, etc.) considerations.
Selection of Material
Product selection can include ‘green’ additive packages, long-life lubricants, recycled oils, natural sourced and/or biodegradable products.
Consider speciality maintenance items to help reduce liquid waste and to improve lubricant sampling procedures for better condition monitoring. Also review condition monitoring testing for effectiveness, review results and successes, do a periodic lubricant survey, and set up guidelines on how to do a proper failure analysis and to do lubricant reviews. Unfortunately, cost accounting can hinder improvement if the added incremental cost of a better product comes out of the maintenance budget. It is not fair that their costs go up while the benefits might be elsewhere so a more appropriate accounting system might be required.
Quick site tests can usually help determine if the oil requires treatment or if the bearing is in distress. Proactive oil testing is also one of the few techniques that can be used to prevent damage. Conversely, most other methods can only detect damage after it has occurred.
When action is required, a lubricant can often be effectively treated while still in the equipment. In many cases, this can be done while the equipment is still on-line, with no loss of production.
If using a contractor, it is important to ensure that they have treated this particular fluid successfully before. It is also prudent to ensure that there will not be any cross-contamination. For example, any equipment should have been well flushed before use with the same fluid.
Re-use or disposal
There are often cost-effective alternatives to disposal, such as the possibility of being able to use the fluid in less demanding applications. These can be on-site or in other industries. An example of this might be making a mineral oil into a cutting fluid.
Correct actions require that those making the proposals and the decisions must be fully aware of all the implications of their actions, of non-actions and of alternatives. Products, equipment and rules are quickly changing so that periodic updates make good sense. It is worth considering asking suppliers to give presentations or arrange for industry experts to provide specific training. Encouraging personnel to go to the appropriate conferences or even to talk to other users can be very helpful.
Last but not least, it is often very important to show that efforts have been made to reduce the environmental impact of operation and/or spills. This is usually under the heading of ‘Due Diligence’. While this might not help prevent environmental charges from being laid if there are spills, it can help reduce the likelihood of problems and/or reduce the environmental consequences. Simply ask ‘How do you know what is being done is right?’ If the only answer is that they have always done it that way then action is likely to be required. Another axiom is: ‘If you are not going forward, you are going backwards’. Times are changing but it is easy to take some action. At the very least check what oils, greases and fluids are being used and what ‘proven’ alternatives are available.
In many situations, it should be relatively easy to make improvements by taking advantage of the options mentioned above. This really makes it a ‘win-win’ scenario, because not only can the equipment run better, but there can be less environmental impact. For VSG, a wicket gate grease, is mainly canola oil, biodegradable, works as well or better than mineral oil based greases, is from a sustainable resource and some stations have used 42 times less! In addition, going ‘Green’ is easy and can cost less in the long-term when all the life-cycle factors are taken into account.
|What is a green lubricant?|
Environmentally friendly lubricants first came on to the market in the mid 1980s. It is generally recognised that these lubricants should have two main characteristics – low toxicity and high biodegradability. For example, if grease is washed out of a wicket gate bearing into the water, the grease should not be toxic to aquatic life, and it should biodegrade in a short period of time.