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Cleanroom HVAC Design

A cleanroom’s HVAC system is truly the most vital and complex component system of a cleanroom facility.  HVAC…an acronym for Heating, Ventilation, and Air Conditioning…generally describes the idea of providing indoor environmental comfort by creating and controlling indoor air quality (cleanliness, air changes per hour, temperature, humidity and pressure).

 

Here are some highlights that summarize how cleanroom HVAC systems are unique:

Cleanroom HVAC vs. Conventional HVAC

In addition to creating a comfortable environment…Cleanroom HVACs specifically focus on:

  1. Increased Air Supply
  2. Airflow Patterns
  3. High Efficiency Filters
  4. Room Pressurization
  5. Regulations & Cleanliness level guidelines
  6. Temperature & Humidity Control
  7. Accounting of processes taking place inside the cleanroom
  8.  Specialized Ventilation Duct Expertise

HVAC System vs. HVAC Unit

HVAC systems and their component HVAC air handling units (AHU) are sometimes confused. The air handler is simply the enclosure in which the air is heated, filtered, and cooled. It includes DX cooling coils, chilled water coils, electric heat or hot water heat coils and humidifiers. The HVAC system is, as its name spells out, the whole system, which includes the air handling unit, but also the duct work, the diffuser, the HEPA filters, the air return, and the control and monitoring system.

Choose/Design the appropriate system

The required cleanliness level of the cleanroom (ISO class) is the key driver of the HVAC design process…in addition to the required temperature, humidity, and pressure differential. These conditions are dictated by the processes taking place in the cleanroom and the required comfort of the personnel working inside the room.

Air Flow (CFM)

The most important bit of information needed to begin the Cleanroom HVAC design process  (by your cleanroom supplier/manufacturer) is:

How many air changes per hour is needed in your cleanroom in order to calculate the required air flow? (CFM: cubic feet per minute).

Though difficult to determine, the answer must take into account the following elements:

  • Cleanliness level (number of particles per cubic foot of air) the cleanroom must be kept within: often determined by the cleanroom class (ISO 5-6-7-8, GMP A-B-C, etc.)
  • Number of people working in the cleanroom
  • Size of the cleanroom and the number of rooms inside
  • Equipment, furniture, and supplies inside the cleanroom since they generate air particulates and contamination
  • Heat gain
  • Movement of people and material in and out of the cleanroom

Temperature and Humidity

The heat produced by both the users and the equipment must be compensated by the air conditioning. Therefore, it is important to know how many people will be working in the cleanroom, the equipment in place and the heat it generates (watt).

Pressure Differential

The HVAC system is responsible for creating pressure differentials to keep pressure cascades in between the divisions of the cleanroom and the outside of the cleanroom.  Most cleanrooms are held in positive pressure. This means that the air will flow out of the room instead of in, thus preventing unfiltered air or air particulates from entering the cleanroom.  When dealing with hazardous products however, the cleanroom must be held in negative pressure.

 

Read More – CEMag

HVAC Maintenance and the Art of Keeping Cleanrooms Clean

Keeping contamination at or below predetermined acceptable levels is a fundamental requirement of cleanroom maintenance.  Even the tiniest random dust particle is considered a legitimate contaminant.

HVAC systems are by definition a critical component system of any cleanroom environment because they are designed to move air from one area to another with the goal of attaining climate control. This process poses many unique challenges to maintaining air quality.  Part of the HVAC system intricacy is that it’s also comprised of multiple other systems that need to be maintained in order to achieve cleanroom high performance standards safely and effectively.


Here a some steps toward keeping your HVAC system clean:

  • Change Filters Regularly – Cleanrooms contain multiple filtering systems… pre-filters, standard filters, and high efficiency filters…Combined, they virtually guarantee that airflow remains free of contaminants down to sizes under .03 microns.  An adequate filter maintenance program shuld schedule filter cleaning at minimum of four to eight week cycles.
  • Clean Coils Regularly – Clean coils keep the system operating at high efficiency levels as well as mitigating bacterial growth within the system. Clean regularly at planned system shutdown intervals and treat with EPA-registered mold and mildew inhibitors.  Properly maintained coils can play a key role in managing critical humidity levels.
  • Clean Blowers Regularly – Blowers in air handler units (AHU) can be magnets for dirt and debris. Make sure to properly visually inspect and clean these often overlooked, yet critical, components of the HVAC system.
  • Clean Ductwork Routinely-  Often overlooked in normal commercial HVAC systems…but in the case of cleanrooms, duct cleanliness is vital. Inspect and clean all ductwork  when  routine filter changes are performed.
  • Clean Other Major HVAC Components – Cooling towers and boilers, for example. As with all above prescriptions, it helps to maintain peak system efficiency and performance.

 

Of course, all the above should be performed by thoroughly trained and highly qualified technicians. But when done correctly and routinely, the process yields several benefits.

Key Benefits of HVAC Maintenance:

  1. For cleanroom management, it’s a necessity and not an option.
  2. A clean HVAC system reduces energy costs, because it doesn’t need to work as hard to keep up as it would if the system was dirty or filled with debris and other contaminants.
  3. HVAC system potential breakdown or need repair is greatly reduced and controlled. Scheduled and properly performed HVAC system maintenance is much less time-consuming much less expensive than shutting down the system for larger repairs or even replacements.

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See Also

 

Cleanroom HVAC Strategies

[The following abstract of an article on HVAC design for cleanrooms and controlled environments is highly technical and the field…as technology is in general…is dynamic and continuously evolving.  It offers an excerpted overview of several key considerations.  Ultimately, your project’s unique properties…especially those of your process, product, research requirements and your physical plant…will determine best practices.]

Cleanroom HVAC design has two (2) critical concerns that can be considered different perspectives on on the same issue:

  1. Contaminants
  2. Control of the Environment

If the war on these manufacturing enemies are not won in the design process, the result can be millions of lost dollars due to insufficient product yield and compromised product integrity…hitting a company’s bottom line forcefully.


Optimal HVAC design solutions are determined by desired temperature and humidity control, air flow and pressure, and filtration requirements and air change rates…at the very least. These design factors are dictated by the requirements unique to your process, facility, and regulatory requirements.

Whether creating a controlled environment for an electronics manufacturer or a life sciences environment free of pathogens, the HVAC system controls your success and will significantly impact your operating costs.

Three (3) contamination fundamentals must be considered…regardless of the degree of desired air quality and cleanliness:

• Contaminants are never beneficial…begin by preventing their passage from outside into the work environment.
• Those that infiltrate your environment must be eliminated quickly.
• Besides worrying about particulate interlopers from the outside environment, make sure you have your own house in order. This means minimizing contaminants that your manufacturing or research processes—including the equipment integral to your operations—throw off, whether through biological, chemical, or operating processes. And make sure your employees consistently follow protocols developed to minimize contamination.

Cleanrooms demand an estimated 10 to 100 times more energy than standard office spaces…due to strict air cleanliness standards—and the HVAC system can account for more than half of the facility’s energy costs.  Following are a variety of strategies to help reduce energy costs related to your HVAC system:

  1. Minimize Demand. Take a look at your building. Can you increase the efficiency of the shell? When building new, carefully orient and develop the building form. Is there an opportunity to reduce the volume of your cleanroom? Less volume equates to less air re-circulation with resulting HVAC savings.
  2. Accurately scope the level of cleanliness and the square footage required. Going overboard in either category will drive up your costs. Considering reducing positive pressurization where prudent.
  3. Flexibility is key. Design your HVAC system with an eye towards flexibility, not only for sustainability, but for future product line and expansion capabilities as well. Remember to accommodate part load scenarios in HVAC equipment purchase.
  4. Subdivide your facility’s space classifications. Carefully examine the proposed process and product requirements when determining your required cleanroom classification. Don’t shoot an ant with an Uzi. Do you really need the entire space to be stringently controlled?
  5. Mini- and micro-environments are your friends; stick or prefab? Consider the use of micro- or mini-environments (see the May 2013 issue of Controlled Environments) and a mix of stick built and prefabricated areas—determined by process specifications and flexibility needs. Utilize these tools to meet your process requirements instead of upgrading your entire cleanroom.
  6. Invest in high efficiency equipment. Upfront costs are an investment with surprisingly short payback periods.

Read More – Controlled Environments

Energy Cost Efficiencies for Cleanroom HVAC Systems

Cleanrooms are well known for being some of the highest energy consuming facilities in the world.  The intensive HVAC requirements for performing stringent airflow and pressurization functions within strict temperature and humidity control parameters…is a major reason.  Consuming anywhere between 10 to 100 times the amount of energy compared to normal office space…a cleanroom’s HVAC system can easily be responsible for over 50% of the entire facility’s energy costs. Having a profound impact on operating costs and overall profitability…achieving the necessary air cleanliness standards is the HVAC systems’s vital role in the production process.  And as overall demand grows …from existing technologies that become increasingly sophisticated…and new technologies that create additional demand…the controlled environments produced by highly efficient HVAC systems becomes more vital with each day.

Here are some selected key design strategies for reducing energy costs related to a cleanroom’s HVAC system:

  1. 1st Priority – Minimize demand:  Consider the building facility as a whole. Can efficiency of the building’s shell be increased? With new buildings, carefully orient and develop the building form. Is there an opportunity to reduce the volume of your cleanroom? Less volume equates to less air re-circulation with resulting HVAC savings.
  2. Accurately Scope the Square Footage Required & Cleanliness Level – Going overboard in either category will drive up your costs. Considering reducing positive pressurization where prudent.
  3. Flexibility – Design your HVAC system with scrutiny on flexibility…not only for sustainability’s sake…but for future product line and expansion capabilities as well.
  4. Subdivide the Facility’s Space Classifications. Carefully examine the proposed process and product requirements when determining your required cleanroom classification. Overkill is an easy trap to fall into. Do you really need the entire space to be stringently controlled?
  5. Invest in High Efficiency Equipment.  Upfront dollars invested in the best equipment… have surprisingly short payback periods.  Remember to use high efficiency filters too.
  6. Alternate Energy Sources – Use them appropriately to reduce the load on your HVAC system through careful analysis and appropriate design throughout the facility. Consider solar heating and power, daylight, wind energy, and thermal energy wherever it’s technically sound and fiscally responsible.
  7. Analyze the Viability of Reducing Air Change Rates (ACR).  Motors and fans sizes are driven largely by the air change rate in the cleanrooms. Larger motors and fans drive increased HVAC investment and operating costs. You can reduce power usage by approximately two-thirds if you reduce your ACR by approximately one-third.
  8. Adjust Airflow to Match Production Load. Scheduling software and timers can be used to decrease air recirculation and the HVAC load during periods of reduced production.  Occupancy sensors can make automatic adjustments depending on the occupancy levels of your biggest contaminant source—people.
  9. Locate Equipment Outside the Cleanroom when feasible. Locate process tools in an adjacent chaseway and provide critical clean access on the cleanroom side, you will reduce heat gain as well as the square footage required in your cleanroom, resulting in less demand on the HVAC system. This also makes future equipment maintenance easier and less costly.
  10. Variable Frequency Drives (VFDs). Variable frequency drives, which adjust HVAC equipment speed to match conditions, can cut your energy up to a third compared to constant speed drives.
  11. Use Particle Counters to Manage Airflow in Real Time. Carefully located optical sensors provide 24/7 particle counts to the building management system, allowing the HVAC system to operate with efficiency matched to need.
  12. Don’t Overdesign Your HVAC System – Being too cautious & conservative or cautious by building in too many safety nets. Those behaviors compromise operating efficiencies.

Lawrence Mechanical - Clean Room HVAC - San Jose CA

Read More – CEMag

HVAC Cleanroom Design – An Introduction

Cleanrooms are enclosures designed to facilitate sensitive research, fabrication and other operations that must take place in the absence of dust, moisture and other airborne contaminants.  There are two main standards systems against which the cleanliness of a clean room is measured:

  • US FED STD 209E – the system of standards set by the U.S. Government
  • ISO Standards – the system of standards set by the International Organization for Standardization

The Cleanroom Industry was born out of and developed for the aerospace and micro-technology industries.  Cleanrooms are used in several other disciplines such as the bio-technology and medical research fields.

 

Several types of cleanrooms exist with unique attributes according to their respective industry requirements:

  • Class 100 Cleanrooms
  • Class 1000 Cleanrooms
  • Class 10000 Cleanrooms
  • Modular Cleanrooms
  • Portable Cleanrooms

Read More about HVAC Cleanroom Systems & Design.