MRO Magazine


Tips on saving energy using preventive maintenance techniques

Companies are becoming more and more focused on green or sustainable initiatives. Unfortunately, most companies are overlooking one of their most lucrative opportunities in energy savings: preventive maintenance.

Studies by the engineering institutes and international companies have shown that a company can cut energy consumption at a plant by five to 10 percent depending by focusing on their preventive maintenance effort. Companies with good preventive maintenance programs would see savings in the five-percent range. Companies with little or no preventive maintenance inspections and services would realize savings in the 10-percent range. The following will highlight some opportunities for examples of energy savings for typical plant equipment.

Mechanical Systems
Some of the energy savings in mechanical systems would be defined by the type of preventive maintenance performed on some of the basic mechanical components. For example, how accurate are couplings aligned? Misalignment by even 0.003" can lead to energy loss through the coupling. This loss is typically displayed as heat energy in the flex member of the coupling and the supporting shaft bearings. Even elastomer couplings will display energy loss.

A second type of mechanical loss is V-belt slippage. Improve tension results in slippage during loading on the belt. This loss is again shown as heat in the contact area between the belt and the sheave. Chain and gear misalignment will also lose energy in the transmission area and bearings.

A third type of energy loss is through improper bearing lubrication. If bearings have excessive lubrication, it requires more energy to churn the lubricant, increasing the fluid friction in the lubricant and overheating of the bearing. The opposite problem is insufficient lubricant, which results in excessive frictional resistance of the bearing (from metal to metal contact) and overheating of the bearing. Poor preventive maintenance practices will easily contribute a 5% to 10% energy loss for mechanical power transmission.

Electrical Systems
As with mechanical systems, the energy waste in electrical systems will be determined by the condition of the electrical systems and the level of maintenance service performed on the systems. Typical energy losses occur in loose connections and poor operating conditions for motors. For example, when a motor is coated with layers of dirt and moisture, it becomes insulated, which prevents or inhibits the thermal transfer process. This condition results in increased resistance of the wiring, which further increases the temperature of the motor and subsequently its energy consumption.

Improper or insufficient maintenance on mechanical drives will also increase the amount of energy required by the motor to drive the system. This, along with many other losses, will contribute to excessive energy requirements by electrical systems. As with mechanical systems, expect a five to 10 percent energy loss due to poor electrical system maintenance.

Steam and Compressed Air Systems
Steam generations systems have long been recognized as having potential to produce substantial energy savings for most plants. Steam trap inspection programs, energy efficient boilers, and leak detection programs have been utilized in reducing steam system losses.

Compressed air systems will experience similar problems related to leakage. Air leaks will require the compressors to run more than necessary (on a system without leaks). This requires additional energy for the compressors to operate unnecessarily. Some companies have even found that they have excess compressor capacity after instituting an air leak reduction program.

Depending on the amount of maintenance performed on the steam and air systems, energy savings from five to as much as 15 percent have been reported by companies initiating good maintenance practices. In addition, some companies have been able to decommission some compressors due to the discovered excess capacity.

Hydraulic Systems
Hydraulic system wastes are generally related to leaks. However, it should be remembered that approximately 20 percent of all input horsepower in a hydraulic system is converted to heat. As leaks are concerned, they can be internal or external. External leaks are easier to find since the oil typically leaves a pool of fluid. These leaks waste energy since the pump will have to run more frequently for the system to operate correctly. In addition, hydraulic systems will require cleaning up the leaks, another form of energy waste.

Internal leaks are more difficult to detect particularly when the leaks are small. They are usually identified by sluggish performance and in hydraulic systems, excessive component heat. Again the pumps and must run more frequently to compensate for the leaks. These, and other energy losses, easily will account for energy losses of five to 15 percent in hydraulic systems.

As seen from these brief examples, a five to 10 percent energy reduction in the plant can easily be attained by a good preventive maintenance system. This savings projection can be used to cost justify almost any comprehensive preventive maintenance program while increasing the “Green” focus for any company.