|To read "Part II: HVAC, Boilers and Cogeneration," click here.
Pharmaceutical manufacturing plants in the U.S. spend nearly $1 billion each year for the fuel and electricity they need to keep their facilities running (Figure 1, below). That total that can increase dramatically when fuel supplies tighten and oil prices rise, as they did last year.
Improving energy efficiency should be a strategic goal for any plant manager or manufacturing professional working in the drug industry today. Not only can energy efficiency reduce overall manufacturing costs, it usually reduces environmental emissions, establishing a strong foundation for a corporate greenhouse-gas-management program.
For most pharmaceutical manufacturing plants, Heating, Ventilation and Air Conditioning (HVAC) is typically the largest consumer of energy, as shown in Table 1 below.
This two-part series will examine energy use within pharmaceutical facilities, summarize best practices and examine potential savings and return on investment. In this first article, we will focus on efficient use of motors, drives and pumps, both for process equipment and compressed air systems. Part 2, to be published in May, will focus on overall HVAC systems, building management and boilers.
Research in this article was first published last September, in an extensive report developed by Lawrence Berkeley National Laboratories for the Energy Star Pharmaceutical Focus. Established in January 2005, this group of pharmaceutical industry corporate energy managers is working to develop resources and tools to foster improved energy efficiency within the industry.
The Environmental Protection Agency (EPA) is also working with Argonne National Laboratory to develop an energy performance benchmarking tool for pharmaceutical plants (see "Will Pharma Wear the Energy Star?"). For more information, please visit www.energystar.gov.
A “systems approach” to motors and drives
Motors and drives are used throughout the pharmaceutical industry to operate HVAC systems, to drive laboratory or bulk manufacturing equipment, including mixers, pumps, centrifuges and dryers, and to move and operate filling and finishing equipment.
In order to prioritize areas for improvement, it is best to take a “systems approach” and look at the entire motor system, including pumps, compressors, motors and fans, instead of examining each component individually. The following steps should be taken:
- Locate and identify all motor applications (e.g., pumps, fans) in the facility;
- Document their conditions and specifications;
- Compare your requirements vs. the actual use of the system to determine the energy consumption rate; this will help determine whether the motors have been properly sized;
- Collect information on potential upgrades or updates to the motor systems, including implementation costs and potential annual savings;
- If you do elect to upgrade or update any equipment, monitor its performance over time to determine actual costs savings .
Other essential issues for energy efficient operation include:
- This can save from 2% to 30% of total motor system energy use .
- Preventive measures consider electrical conditions and load, minimize voltage imbalance and include motor ventilation, alignment and lubrication.
- Predictive measures observe ongoing temperature, vibration and other operating data to determine when to overhaul or replace a motor before it fails.
- Ensuring that motors are properly sized, and that oversized motors are replaced, can save, on average, 1.2% of total motor system electricity consumption . Generally, whenever peak loads can be reduced, so can motor size.
- Belt drive replacement.
- Roughly 4% of pumps have V-belt drives, many of which can be replaced with direct couplings to save energy . Savings associated with V-belt replacement are about 4% of total motor system electricity consumption, and costs are estimated at $0.10/kWh-saved with payback within two years.
- Rewinding vs. replacement.
- Replacing an old motor with a high-efficiency motor is often a better choice than rewinding a motor. Currently, there are no quality or efficiency standards for rewinding, and motor efficiency typically decreases from 2% to 25% after rewinding.
When considering whether to rewind a motor or to replace it with a higher-efficiency model, consider the following rules of thumb:
- Never rewind a motor damaged by excessive heat;
- Replace motors that are less than 100 hp and more than 15 years old;
- Replace any motors that have previously been rewound .
High-efficiency motors, meeting or exceeding performance criteria published by the National Electrical Manufacturers Association (NEMA), reduce energy losses through improved design, better materials, tighter tolerances and improved manufacturing techniques.
Making the case for replacement
Replacing an old, poorly functioning motor with a high-efficiency one is easily justified, since payback is usually accomplished in less than a year . Twenty-three case studies of high-efficiency motor installations in the U.S. pharmaceutical industry showed an average payback period of less than three years .
Justifying replacement may be more difficult when an old motor still performs adequately, but, even in these cases, replacement can save money, especially for motors that run for long hours at high loads. One study  showed a payback period of less than 15 months for 50 horsepower (hp) motors.
3M conducted an in-house motor system performance optimization project at a facility housing pilot plants, mechanical and electrical maintenance shops, laboratories and support functions. After evaluating all electric motors larger than 1.5 hp in the building, the company identified 50 older, standard-efficiency motors that ran for more than 6,000 hours per year. Twenty-eight of these motors were replaced with energy-efficient motors.
The company expected to see a 2% to 5% improvement in energy efficiency for each motor that was replaced. 3M also took other steps such as changing impellers or sheaves to reduce the driven load, downsizing motors to better match system requirements, and repairing and cleaning components to reduce efficiency losses. Payback took 3.1 years .
Adjustable speed drives (ASDs) better match speed to load requirements, offering substantial savings in a variety of applications . Typical savings range from 7% to 60%. Four case studies in the U.S. pharmaceutical industry have demonstrated an average payback period for ASDs of less than two years . These four case studies included the installation of ASDs on cooling tower fans, ventilation equipment and a dust collector motor. Genentech has installed ASDs on variable air volume (VAV) air handlers in its Vacaville, Calif. facility, saving about $23,000 per year.
Compressed air: the money pit
Compressed air is required for many pharmaceutical manufacturing applications, including equipment operation, vacuum cleaning, spray systems, ambient and instrument air in hazardous areas. In pharmaceutical facilities, compressed air often comes in contact with products, such as in spray coating operations or in packaging, so it is often filtered to meet strict contamination control standards.
Despite its importance, compressed air is one of the least energy-efficient applications in any drug manufacturing plant. Efficiency of compressed air systems is only around 10%, so compressed air should be used sparingly. When used, it should be monitored, and weighed against potential alternatives.
Techniques for reducing energy consumption in compressed air systems aren’t very expensive, and savings can range from 20% to 50% or more of total system electricity consumption . Below are some issues to consider where compressed air systems are concerned.
Buying additional compressors should only be considered after a complete system evaluation. Energy efficiency can often be improved without adding compressors (visit www.compressedairchallenge.org for tips on selecting the right integrated service provider, as well as guidelines defining walk-through evaluations, system assessments and fully instrumented system audits).
Maintenance is essential to improving efficiency. The following guidelines should apply:
- Keep the compressor and intercooling surfaces clean.
- Blocked filters increase pressure drop, and more frequent filter changing can reduce annual energy consumption by 2%. Seek filters with just a 1 psig pressure drop over 10 years. The payback for filter cleaning is usually under two years . Fixing improperly operating filters will also prevent contaminants from entering into equipment, which can cause premature wear.
- Keep motors properly lubricated and cleaned.
- Compressor lubricant should be changed every two to 18 months and checked to make sure it is at the proper level.This will also reduce corrosion and degradation of the system.
- Inspect fans and water pumps
- for peak performance.
- Inspect drain traps periodically
- to ensure that they are not stuck in either the open or closed position and that they are clean. Some users leave automatic condensate traps partially open at all times to allow for constant draining. This should never be done, as it wastes a substantial amount of energy. Instead, install simple pressure-driven valves. Inspecting and maintaining drains typically has a payback of less than 2 years  .
- Maintain the coolers on the compressor
- to ensure that the dryer gets the lowest possible inlet temperature .
- If using compressors with belts, check belts for wear and adjust them.
- A good rule of thumb is to adjust them every 400 hours of operation.
- Replace air lubricant separators according to specifications or sooner.
- Rotary screw compressors generally start with their air lubricant separators having a 2-3 psi pressure drop at full load. Once this number increases to 10 psid, change the separator .
- Check water-cooling systems for water quality (pH and total dissolved solids), flow and temperature.
- Clean and replace filters and heat exchangers per manufacturer’s specifications.
- Minimize leaks
- (see also the “Leak Reduction” section below).
- Specify pressure regulators that close when failing.
- Check all applications requiring compressed air for excessive pressure, duration or volume.
- They should be regulated either by production line sectioning or by pressure regulators on the equipment itself. Equipment that does not have to run at maximum system pressure should use a quality pressure regulator that will not drift. Payback for this step is less than six months .
Monitoring can save significant energy and cost in compressed air systems. The following tips can help:
- Install pressure gauges
- on each receiver or main branch line and differential gauges across dryers and filters.
- Use temperature gauges
- across the compressor and its cooling system to detect fouling and blockages.
- Measure the quantity of air used
- with flow meters.
- Monitor the effectiveness of air dryers
- with dew-point temperature gauges.
- Place kilowatt-hour (kWh) meters and hours-run meters on the compressor drive.
Compressed air distribution systems should be checked when equipment has been reconfigured to be sure that air isn’t flowing to unused equipment or obsolete parts of the compressed air distribution system. Compressed air use should also be checked outside of normal production hours.
In addition, it is important to check for flow restrictions of any type within the system, since they will require higher than necessary operating pressures. The pressure rise that results from resistance to flow increases the drive energy on the compressor by 1% of connected power for every 2 psig of differential.
- Leak reduction.
- Air leaks are a major energy drain, but they also can damage equipment. A poorly maintained compressed air system will likely have a leak rate equal to 20% to 50% of total capacity. Leak maintenance can reduce this number to less than 10%. Fixing leaks pays off, reducing annual energy consumption by 20% .
- The magnitude of the energy loss varies with the size of the hole in the pipes or equipment. A compressor operating 2,500 hours per year at 6 bar (87 psi) with a leak diameter of 0.02 in. (½ mm) will lose 250 kWh per year; 0.04 in. (1 mm) will lose 1,100 kWh per year; 0.08 in. (2 mm) will lose 4,500 kWh per year; and 0.16 in. (4 mm) will lose 11,250 kWh per year . Payback takes less than two months . The best way to detect leaks is to use an ultrasonic acoustic detector.
- Turning off unnecessary compressed air, using a solenoid valve.
- Modifying rather than increasing operating pressure.
- For individual applications that require a higher pressure, instead of raising the operating pressure of the whole system, consider special equipment modifications, e.g., a booster, increasing a cylinder bore, changing gear ratios or changing operation to off-peak hours.
- Considered alternatives to compressed air, such as:
- air motors only for positive displacement;
- air conditioning fans instead of compressed air vortex tubes in cooling electrical cabinets;
- vacuum pumps instead of venturi methods for flowing high-pressure air past an orifice;
- blowers for cooling, aspirating, agitating, mixing or package inflating;
- blowers or vacuum pump systems for cleaning parts or removing debris;
- electric actuators or hydraulics for moving parts;
- low-pressure air for blowguns, air lances and agitation;
- motors for tools or actuators, except in situations where precision and safety are paramount.
- Payback for replacing compressed air with other options takes an average of 11 months.
- Better load management.
- Avoid partial load operation.
- For example, unloaded rotary screw compressors still consume 15-35% of full-load power while delivering no useful work. Centrifugal compressors are cost-effective when operated at high loads.
- Use air receivers near high demand areas to provide a supply buffer
- to meet short-term demand spikes that can exceed normal compressor capacity. In this way, the number of required on-line compressors may be reduced.
- Replace single-stage compressors with two-stage compressors.
- This typically provides a payback period of two years or less. Multi-stage compressors theoretically operate more efficiently than single-stage compressors because they cool the air between stages, reducing the volume and work required to compress the air.
- Use multiple smaller compressors instead of one large compressor.
- Large compressors consume more electricity when they are unloaded than do multiple smaller compressors with similar overall capacity. Optimal sizing pays for itself in about 1.2 years.
- Minimizing pressure drop.
- Manufacturers’ recommendations for maintenance should be followed, particularly in air filtering and drying equipment, which can have damaging moisture effects like pipe corrosion. Finally, the distance that the air travels through the distribution system should be minimized. Audit results found that the payback period is typically shorter than 3 months for this measure.
- Reducing inlet air temperature.
- If airflow is kept constant, reducing the inlet air temperature reduces the energy used by the compressor. In many plants, it is possible to reduce the inlet air temperature to the compressor by taking suction from outside the building. As a rule of thumb, each 5°F (3°C) will save 1% compressor energy.
- Maximizing the allowable pressure dew point at air intake.
- Choose a dryer that has the maximum allowable pressure dew point and best efficiency. A rule of thumb is that desiccant dryers consume 7-14% of the total energy of a compressor, whereas refrigerated dryers consume 1-2% of the total energy of a compressor.
- Sophisticated controls can save 12% per year. Options include start/stop, load/unload, throttling, multi-step, variable speed and network.
- Properly sized regulators —
- optimally, those that close when they fail.
- Properly sized pipe diameters.
- Increasing diameters can reduce energy consumption to 3%.
- Heat recovery for water preheating.
- Up to 90% of the electrical energy used by an industrial air compressor is converted into heat. In many cases, a heat recovery unit can recover 50-90% of the available thermal energy. It has been estimated that approximately 50,000 btu/hour of energy is available for each 100 cfm of compressor capacity . Payback periods are typically less than 1 year.
- Natural gas engine-driven air compressors.
- Gas engine-driven air compressors can replace electric compressors. They are more expensive but may have lower overall operating costs, depending on the relative costs of electricity and gas. Variable-speed capability is standard for gas-fired compressors, offering a high efficiency over a wide range of loads. Heat can be recovered from the engine jacket and exhaust system. However gas compressors need more maintenance, have a shorter useful life and have a greater likelihood of downtime.
Pumping systems account for about 25% of the electricity used in U.S. manufacturing plants, and pumping coolants is an energy-intensive pharmaceutical application. Studies have shown that over 20% of the energy consumed by pumping systems could be saved through changes to equipment and/or control systems.
In general, for a pump system with a lifetime of 20 years, the initial capital costs of the pump and motor make up a mere 2.5% of the total costs. In contrast, energy costs make up about 95% of the lifetime costs of the pump. Maintenance costs comprise the remaining 2.5% . Hence, the initial choice of a pump system, consisting of a pump, a drive motor, piping networks and system controls such as ASDs or throttles should be highly dependent on energy cost considerations rather than on initial costs.
The energy-efficiency measures described below apply to all pump applications.
- Proper pump system maintenance includes the following:
- Replacement of worn impellers, especially in caustic or semi-solid applications.
- Bearing inspection and repair.
- Bearing lubrication replacement, on an annual or semiannual basis.
- Inspection and replacement of packing seals. Allowable leakage from packing seals is usually between 2 and 60 drops per minute.
- Inspection and replacement of mechanical seals. Allowable leakage is typically 1 to 4 drops per minute.
- Wear ring and impeller replacement. Pump efficiency degrades 1-6 points for impellers less than the maximum diameter and with increased wear ring clearances.
- Pump/motor alignment check.
- Better pump maintenance saves between 2% and 7% of pumping electricity, with paybacks within a year.
- Pump demand reduction.
- Holding tanks can be used to equalize the flow over the production cycle, enhancing energy efficiency and potentially reducing the need to add pump capacity. Bypass loops and other unnecessary flows should be eliminated. Each of these steps can save 5-10% of pump system electricity consumption.
- The objective of any control strategy is to shut off unneeded pumps or, alternatively, to reduce pump load until needed.
- Replacing older pumps with high-efficiency pumps.
- According to inventory data, 16% of pumps used in industry are more than 20 years old. A pump’s efficiency may degrade by 10-25% in its lifetime. Newer pumps are typically 2-5% more efficient, while high-efficiency motors have also been shown to increase the efficiency of a pumping system by 2-5%..
- Properly sized pumps.
- Optimal sizing can save, on average, 15-25% of the electricity consumption of a pumping system. Paybacks for implementing these solutions are typically less than 1 year.
- Multiple pumps for variable loads.
- This is the most cost-effective and energy-efficient solution for varying loads.
- Impeller trimming.
- If a large differential pressure exists at the operating rate of flow (indicating excessive flow), the impeller diameter can be trimmed so that the pump does not develop as much head. Impeller trimming can save up to 75% of electricity consumption.
|To read "Part II: HVAC, Boilers and Cogeneration," click here.
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- Flex Your Power, an Industrial Product Guide—Manufacturing and Processing Equipment: Compressed Air Equipment. The Efficiency Partnership, San Francisco, 2004.
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- Op. Cit., Department of Energy, 1998.
- Op. Cit., IAC.
- Radgen, P. and Blaustein., E. (Eds.), Compressed Air Systems in the European Union, Energy, Emissions, Savings Potential and Policy Actions, LOG_X Verlag, GmbH, Stuttgart, Germany, 2001.
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