No - Pharmaceutical Manufacturing



White Paper -- Strobic Air Corporation

Mixed-flow impellers offer pharmaceutical plants enhanced safety

while lowering emissions and cutting energy costs.

By Paul A. Tetley

Strobic Air Corporation

Harleysville, PA

Most pharmaceutical manufacturers operate controlled environment work areas for research, pilot production and, occasionally, for general product processing. All of these facilities share a common characteristic: exhaust from their laboratory workstation fume hoods or processing areas must be safely disbursed into the atmosphere without causing re-entrainment, neighborhood odor, or environmental violations.

Most pharmaceutical manufacturers also face extraordinarily high energy costs for their HVAC systems in general, and their conditioned, controlled environment facilities in particular. In fact, energy costs for pharmaceutical research and manufacturing are among the highest of all SIC industrial categories. Faced with these concerns (among other issues to be discussed here), these organizations seek methods to help lower energy costs while assuring workplace safety and remaining “good neighbors” as well.

There’s a practical solution to all these problems, and it’s right on the roof. This solution has been gaining broad acceptance over the last few decades; it offers freedom from pollution abatement problems, and elimination of re-entrainment and odor generation possibilities while also helping to drastically lower energy costs. It is known as mixed flow impeller technology (as employed in low profile roof exhaust systems).

Until widespread application of mixed flow impeller technology, exhausting laboratory workstation fume hoods in closed-loop, conditioned make-up air facilities was traditionally handled by centrifugal belt-driven fans with tall, individually dedicated stacks on the roof. During the past few decades, mixed flow impeller technology has made significant inroads for many of these applications. Recently, this technology has become even more popular, mainly as a result of its ability to capture ambient heat within a controlled environment facility prior to its discharge into the atmosphere. This capability alone has resulted in savings of tens and even hundreds of thousands of dollars annually for pharmaceutical organizations throughout the country – especially those located in colder climates.

Exhaust stream dilution prevents re-entrainment

Mixed flow impeller roof fans send their exhaust streams hundreds of feet into the air in a powerful vertical plume, mixing outside air with exhaust gases (dilution) to prevent re-entrainment as well as eliminate odor problems. They also provide other advantages, such as inherently lower energy consumption over comparable centrifugal-type exhaust systems. With the ability to pre-heat (and pre-cool) makeup air prior to its introduction into the building, the systems permit substantial energy savings for pharmaceutical research and manufacturing organizations.

Roof exhaust systems at pharmaceutical processors perform many different functions. Their mail purpose is to prevent re-entrainment to help assure healthy indoor air quality (IAQ), since there have been problems over the past few years as a result of poor IAQ. In fact, there have been cases where employees became ill because exhaust was re-entrained through building intake vents, doors, windows, and other openings.

While roof exhaust re-entrainment can be a serious problem, all of its negative implications may not be widely known. Not only can the health of building workers be affected by exhaust reentering the building, but the legal consequences can extend well beyond their employers. There have been cases where building owners, consulting engineers, heating, ventilation, and air conditioning (HVAC) contractors and even architects were named as defendants in major cases associated with employee illness and IAQ.

Research laboratories at most pharmaceutical organizations can range from discrete prototyping facilities through complex biosafety level (BSL) 3 or 4 facilities which require accurate, repeatable control and management over such environmental parameters as temperature, pressure, airflow, and humidity – almost always in combination. Roof exhaust re-entrainment at biosafety level laboratories may be insidious at times – but can be serious. This is especially true at BSL-3 and -4 laboratories where highly contagious microorganisms may be present. No matter what kind of research is being conducted, it is imperative that the workstation fume hood exhaust system be given proper consideration. Exhaust re-entrainment can be caused by many factors such as inefficient roof fans, poor exhaust stack design and/or location, position of building air intakes, weather and wind conditions, and other factors which will be discussed here.

BSL laboratories present a unique set of problems with regard to re-entrainment and pollution abatement. As a result they are governed by rigid codes and standards (in some instances guidelines only) formulated by a number of organizations including the American National Standards Institute (ANSI), American Industrial Hygiene Association (AIHA), National Fire Protection Association (NFPA), National Research Council (NRC), American Conference of Governmental Industrial Hygienists (ACGIH), American Institute of Architects (AIA), Occupational Safety and Health Administration (OSHA), American Society of Heating, Refrigeration and Air conditioning Engineers (ASHRAE), the Center for Disease Control (CDC), the National Institutes of Health (NIH), and the U.S. Department of Health and Human Services (DHHS).

Special exhaust requirements at BSL laboratories

Biosafety level laboratories (mainly levels 3 and 4) must incorporate many special design and engineering features to prevent microorganisms from being discharged into the environment. These features would typically include specially shielded isolation rooms under negative pressure with sophisticated control and monitoring systems for managing their environmental parameters; they would also require 100% conditioned “makeup” air to prevent re-use of the ambient air within an enclosed facility.

Obviously exhaust emissions from laboratory workstations at these facilities must be treated carefully. For one reason, they may be highly toxic or noxious – or both. Their danger to people covers a broad spectrum which might be mildly annoying to seriously unhealthy. Even if the exhaust stream does not present health issues, public tolerance for annoying odors has sharply decreased in recent years, partly because government agencies are continually setting more stringent standards and lowering allowable exposure limits. Obviously there is no room for tolerance with regard to possible contamination from some agents that are exhausted at BSL Level 3 and 4 facilities.

HEPA filter modules reduce dust emissions

As in most pharmaceutical research laboratories and pilot processing areas, a dedicated air supply and exhaust system is critical to safety as well as comfort. The HVAC system would typically be independent of all other supply and exhaust systems within the building. Because of increasingly stringent environmental regulations, mixed flow impeller systems incorporating bag-in/bag-out (BIBO) High Efficiency Particulate Air (HEPA) modules and filters are also becoming popular for research, pilot plant, and production environments. The modules are typically matched with application specific filter media which accommodate a variety of HEPA and ASHRAE filter efficiencies.

Mixed flow impeller systems with HEPA modules and filters are particularly useful at pharmaceutical processing organizations, since unwanted dust is created during the manufacturing and packaging cycle. Sources for this dust vary. They can include formulating tablets or capsule ingredients from powders, spray coating tablets, drying products (which creates particulate fines through airstream abrasion or contact friction) and even packaging when tablets are transported at high speeds on conveyor lines or capsules are being filled by automated equipment.

Heat recovery saves thousands of dollars yearly

With regard to the extraordinarily high energy costs faced by most pharmaceutical organizations, there appears to be no cap in sight. In fact, based on an extremely unstable geopolitical climate among many energy producing nations, it would be surprising to see significant cost reductions in the future. To that end most prudent pharmaceutical processors seek new ways to reduce their energy costs. Mixed flow impeller technology has proved to be beneficial for these organizations where conditioned air must be filtered, heated, cooled, humidified, or de-humidified (or some combination) depending upon requirements.

These organizations must provide comfortable and safe environments for scientists and technicians, and that requires efficient – and expensive – heating and cooling of makeup air for the workplace. In addition, workstation fume hoods usually require sophisticated controls and energy consuming hood management equipment for proper operation. When you add fume hood exhaust systems on the roof – which must operate whenever a workstation is being used – energy costs mount up quickly.

Mixed flow impeller technology represents an ideal solution to these problems. By adding accessory heat recovery modules consisting of glycol/water filled coils that extract heat from workstation fume hood exhaust before it is discharged above the roofline, substantial energy savings are realized. The warm air from the heat exchanger is transferred to the supply side handler to preheat the conditioned air entering the building, thus reducing the amount of natural gas or fuel oil needed to heat makeup air. This process works the same way for chilled air, of course.

3% energy savings for each 1° F temperature increase

Mixed flow impeller exhaust systems with heat exchanger coils save about 3% of energy costs for each 1° F rise in recovered heat; similar, but not quite as dramatic, savings are realized for cooling applications. Systems such as these are most practical when outside air temperatures are below 40° F (5° C) or above 80° F (27° C) typically. That’s because there must be a large enough difference between outside and inside air to make it cost-effective. On the cooling side, if the outside air temperature is 90° F (32° C) and the chilled indoor air is sent through the heat recovery coils, the makeup air temperature drop is typically 4° to 5° F.

As anti-pollution laws become tougher, even the sight of a tall exhaust stack on the roof imparts negative connotations in a community. Also, tall exhaust stacks usually require complex, expensive mounting hardware (elbows, flex connectors, spring vibration isolators, guy wires, roof curbs, etc.), and often still do not totally prevent re-entrainment of exhaust fumes back into the building or adjacent facilities. In addition, the belt-driven centrifugal fans associated with these systems require regular maintenance; because of this they are often housed on the roof inside a “penthouse.” The penthouse protects workers from the elements during maintenance operations; however, these workers might also be subject to exposure from toxic and/or noxious fumes, since the fans’ discharge is always under positive pressure.

Reduced installation costs, less maintenance problems

Roof exhaust systems incorporating mixed flow impeller technology eliminate nearly all of these problems. Their low profile design (typically about 15' high) eliminates the need for all structural reinforcements on the roof. Because they are substantially shorter (and constructed modularly) than the tall, often unsightly stacks they are used to replace, their simplicity also helps reduce installation time and costs significantly. In fact, in many retrofit applications there is virtually no downtime associated with their installation.

Under normal conditions, mixed flow impeller systems are designed to operate continuously for years without maintenance. Direct drive motors have lifetimes of L10 400,000 hours (see sidebar). And the non-stall characteristics of the blade design permits variable-frequency drives to be used for added variable-air-volume (VAV) savings, built-in redundancy, and design flexibility. These fans also operate at lower noise levels than centrifugal fans – particularly in the lower octave bands – which could be advantageous in some locations. When noise is still an issue, however, accessories such as low profile acoustical silencer nozzles can be used.

Low operating costs help the bottom line

Mixed flow impeller fans typically consume about 25% less energy than conventional centrifugal fans, and offer faster payback periods as well. Typical energy reduction is $0.44 per cubic foot per minute (CFM) at $0.10/kilowatt-hour, providing an approximate two-year return on investment. These numbers do not include the drastic energy savings they can provide for conditioned makeup air facilities.

Building aesthetics should also be considered

When designing or retrofitting a new roof exhaust system stack height should also be considered as well for performance (re-entrainment prevention and pollution abatement), aesthetics, and code/standard compliance. Ideally you would seek the lowest profile possible which not only eliminates the “smoke stack” pollution generating negative connotations perceived by many people, but it may also help conform to applicable architectural/aesthetic ordinances. Elimination of tall, unsightly stacks which are either prohibited by code or undesirable is an added benefit. In some areas for example, no stacks are allowed on the roof – period.

Conclusion

There are hundreds of pollution control standards that must be addressed when considering dedicated roof exhaust systems. Mixed flow impeller technology has proved over the past few decades its value with regard to aiding conformance to virtually all appropriate standards.

If you’re planning to upgrade, retrofit, or construct new laboratory workstation facilities or process areas, mixed flow impeller technology exhaust systems represent a practical and cost-effective approach for eliminating re-entrainment, preventing pollution and neighborhood odor, conforming to aesthetic ordinances and standards, and cutting energy costs substantially. In addition to dramatic fuel savings for heating and cooling (in 100% conditioned makeup air facilities), this technology offers advantages of lower energy consumption over comparable centrifugal-type exhaust fans, and virtual elimination of periodic maintenance headaches. Based on current trends, this technology will likely continue to meet the needs of a growing base of pharmaceutical research and manufacturing organizations.

About the Author:

Paul A. Tetley is vice president and general manager at Strobic Air Corp., a subsidiary of Met-Pro Corp. Since joining the company in 1989 as engineering production manager, he has designed and/or invented Tri-Stack fan systems, an acoustical silencer nozzle, and a unique multi-fan plenum system. He may be contacted at 215-723-4700 or by email at ptetley@.

|Sidebar 1: Characteristics Of |

|Mixed Flow Impeller Technology Systems |

| |

|Mixed flow impeller systems operate on a unique principle of diluting contaminated exhaust air with unconditioned, outside ambient |

|air via a bypass mixing plenum. The resultant diluted process air is accelerated through an optimized discharge nozzle/windband |

|where nearly twice as much additional fresh air is entrained into the exhaust plume before leaving the fan assembly. Additional |

|fresh air is entrained into the exhaust plume after it leaves the fan assembly through natural aspiration effect. The combination |

|of added mass and high discharge velocity minimizes the risk of contaminated exhaust being re-entrained into building fresh air |

|intakes, doors, windows, or other openings. |

| |

|As an example, a mixed flow fan moving 80,000 cfm of combined building and bypass air at an exit velocity of 6300 feet per minute |

|can send an exhaust air jet plume up to 120 feet high in a 10 mph crosswind. This extremely high velocity exceeds ANSI z9.5 |

|standards by more than twice the minimum recommendation of 3000 fpm. Because up to 170% of free outside air is induced into the |

|exhaust airstream, a substantially greater airflow is possible for a given amount of exhaust – providing excellent dilution |

|capabilities and greater effective stack heights over conventional centrifugal fans without additional horsepower. |

| |

|Mixed flow impeller systems also reduce noise, use less energy, and provide enhanced performance with faster payback over |

|conventional laboratory fume hood exhaust systems. A typical reduction of $.44 per cfm at $.10/kilowatt-hour provides an |

|approximate two year R.O.I. Energy consumption for mixed flow fans is about 25% lower than conventional centrifugal fans with |

|substantially reduced noise levels, particularly in the lower octave bands. They also conform to all applicable laboratory |

|ventilation standards of ANSI/AIHA z9.5 as well as ASHRAE 110 and NFPA 45, and are listed with Underwriters Laboratory under UL |

|705. |

| |

|Mixed flow systems are designed to operate continuously with a minimum amount of required maintenance, providing years of trouble |

|free performance under normal operating conditions. Direct drive motor bearings have lifetimes of l10 400,000 hours. (this refers|

|to a “sample” of 100 motors in which the bearings in ten motors {10%} would fail within a 400,000-hour timeframe. It is a baseline|

|for comparison of motor bearing lifetimes.) Non-stall characteristics of the system’s mixed flow wheel make it ideally suited for |

|constant volume or variable air volume (VAV) applications, along with built-in redundancy, and design flexibility. VAV |

|capabilities are achieved via the bypass mixing plenum or by using variable frequency drives to provide optimum energy savings. |

| |

|Virtually maintenance free operation (there are no belts, elbows, flex connectors, or spring vibration isolators to maintain) |

|eliminates the need for expensive penthouses to protect maintenance personnel under adverse conditions. Consequently, additional |

|savings of several hundreds of thousands of dollars may be realized in a typical installation. |

| |

|Mixed flow impeller systems are available with a variety of accessories that add value, reduce noise, and/or lower energy costs |

|substantially. For example, accessory heat exchanger glycol/water filled coils for use in 100% conditioned makeup air (controlled |

|environment) facilities add exhaust heat to intake ventilation air to save thousands (or hundreds of thousands) of dollars in |

|annual energy costs. |

|Sidebar 2: Biosafety Considerations |

| |

|Biosafety laboratory levels are graded from 1 to 4, with many different standards and guidelines set by the organizations mentioned |

|in the accompanying text. These organizations mandate guidelines that identify and list specific agents as to classes of |

|laboratories required for their presence. The different levels are essentially determined by the degree of risk associated with |

|exposure to various infectious agents within the laboratories. For example, Level 1 agents are usually not placed on the list but |

|are assumed to include all fungal, viral, rickettsial, chlamydial, and parasitic agents which have not been included in higher |

|biosafety levels. For the most part these agents can be handled safely in the laboratory without special equipment using techniques |

|generally acceptable for non-pathogenic materials. Typical examples include certain influenza strains, infectious canine hepatitis |

|viruses, and other “low-risk oncogenic viruses,” according to the University of California, San Diego Biosafety Handbook. |

| |

|Biosafety Level 2 bacteria are considered of “moderate potential hazard to healthy human adults and the environment.” Some agents |

|listed may cause disease by contact or respiratory routes, but they are self-limiting and do not cause a serious illness. For |

|example, common cold viruses (rhinoviruses) are considered Level 2 agents. Other examples include streptococcus pneumonia, |

|staphylococcus aureus, poliovirus, etc. There is a specific list of bacteria, fungal, and parasitic agents, along with viruses and |

|prions and moderate risk oncogenic viruses that are clearly defined in the infectious agents list of the UCSD Biosafety Handbook. |

| |

|With regard to more serious (and potentially lethal) diseases that may be transmitted via inhalation, laboratories handling them must|

|conform to Biosafety Level 3 standards. These standards are also defined for bacterial agents, fungal agents, parasitic agents, and |

|viral agents, but include more virulent and toxic forms than Biosafety Level 2 materials. |

| |

|Biosafety Level 4 agents are considered “dangerous and exotic…and pose a high individual risk to aerosol transmitted laboratory |

|infections which result in a life threatening disease, or related agents with unknown methods of transmission.” According to the |

|infectious agents list, these agents require the most stringent conditions for their containment and are “extremely hazardous” to |

|laboratory personnel or may even cause serious epidemic diseases. Not only are facilities and equipment critical in operation of |

|Biosafety Level 4 laboratories, but the guidelines also call for “staff with a level of confidence greater than one would expect in a|

|college department of microbiology, and who have had specific and thorough training and handling dangerous pathogens…” |

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