Cleanroom Pass Throughs Information
Wall mounted pass through. | Floor mounted | Roller transfer platform
Image Credit: Terra Universal, Inc.
Cleanroom pass throughs consist of a small airlock chamber with two doors and allow equipment and personnel to enter a cleanroom while preventing particle contamination of the cleanroom environment. They can consist of a chamber, air shower, or tunnel. Cleanroom pass throughs are very important in laboratories or manufacturing facilities that require clean and/or sterile rooms for research, manufacturing, and assembly of a product. Cleanrooms allow the room to stay clean as the product or item is moved into or out of the room.
Integrity of Cleanroom Class
Cleanliness class is a standard determined by the contamination control industry. This classification is based on particle concentration. Each designated class represents a maximum amount of particulates of known sized to be present per unit volume within the cleanroom. There are two governing agencies that have developed classification schemes used to decipher the cleanroom class: the International Organization for Standardization (ISO) and the US Federal Standards.
International Organization for Standardization (ISO)
ISO/DIS 14644-1 is a standard developed by ISO that describes the methodology of classifying a cleanroom to one of several classes. This standard is periodically reviewed and revamped to address the needs of the industry. ISO cleanroom classes are defined by the following formula:
= Maximum number of particulates per cubic meter that are equal to or greater than size D
= ISO class number, a multiple of 0.1 that is less than 9
= Size of particulate in micrometers (μm)
US Federal Standards
FED-STD-209E is a US federal government standard that is used to classify the cleanliness of a cleanroom. The class number used refers to the maximum number of particles bigger than one-half of a micron that would be allowed in one cubic foot of cleanroom air. A Class 100 cleanroom, for example, would not contain more than 100 particles bigger than half a micron in a cubic foot of air. The six classes and ISO equivalents are Class 1 (ISO 3), Class 10 (ISO 4), Class 100 (ISO 5), Class 1,000 (ISO 6), Class 10,000 (ISO 7), and Class 100,000 (ISO 8).
Image Credit: American Cleanroom Systems
When selecting a cleanroom pass through there are several important criteria to consider including size, material of construction, mounting options, and features.
When selecting a cleanroom pass through there are several important size criteria to consider. The inside width, inside depth, and inside height of the pass through should be selected based on the size of the materials that will be passing through as well as the available space in the wall from the clean room to the rest of the facility. Selecting the correct size is important to ensure that the pass through fits correctly, reducing the risk of leakage and failure.
Image Credit: Clean Air Products
Materials of Construction
Cleanroom pass throughs are manufactured from various materials including aluminum, acrylic, polypropylene, polyvinyl chloride, stainless steel, and steel. Materials of construction may be governed by the requirements of the air shower.
Aluminum is a bluish, silver-white, malleable, ductile, light, trivalent, metallic element that has good electrical and thermal conductivity, high reflectivity, and resistance to oxidation.
Acrylics are a category of plastics noted for excellent transparency and clarity in its colorless forms, breakage resistance many times that of glass, and good resistance to environmental factors such as UV radiation and chemical corrosion.
Polypropylene (PP) is a thermoplastic material exhibiting excellent cold flow, bi-axial strength, and yield elongation properties. It is similar to PVC, but can be used in exposed applications because of its resistance to UV, weathering, and ozone.
Polyvinyl chloride (PVC) is a widely used material that has good flexibility, smooth surface, and nontoxic qualities. Some grades are used in food and chemical processes due to the inert nature of PVC. Several grades of PVC are available including static-dissipative PVC, which is designed for static- or particle-sensitive applications.
Stainless steel is chemical and corrosion resistant, and can have relatively high stress ratings. Although many grades are available, most stainless steel cannot be hardened to the same degree as carbon steels.
Steel is a commercial iron that contains carbon in any amount up to about 1.7 percent as an essential alloying constituent. It is malleable when under suitable conditions, and is distinguished from cast iron by its malleability and lower carbon content.
The mounting option determines how the pass through will be installed and used in the cleanroom. There are two popular choices available.
Wall mounted pass throughs are generally installed on or within a wall. They can be small enough to only allow the product through or large enough to allow a person through.
Floor mounted pass throughs are supported by the floor and are generally large enough for a cart of products to pass through.
Pass thru air locks. Video Search: Clean Air Products
It may be necessary to choose one of several features to improve the functionality of the pass through in the specified application. Cleanroom pass throughs may include any of the following features:
Interlock switches couple a moveable guard door with a locking mechanism. It may control the power source to magnetic locks or otherwise mechanically lock opposing guard doors. Interlock switches ensure that only one door is open at any given time. Interlocks isolate what is inside the chamber of the pass through and prevent airflow that could otherwise contaminate the controlled environment.
Image Credit: Terra Universal, Inc.
ESD or static control is employed to minimize and help eliminate static charges. Static neutralization is a practical method of static reduction; however complete static elimination is not readily attainable. Cleanroom pass throughs with static control use static dissipative materials of construction to prevent static charges from accumulating and transferring across exposed surfaces.
Image Credit: SKOLNIK
Air showers are used to clean particle contamination from equipment during entry into a cleanroom environment via jets of filtered air. Removal may include dust particles or other excess contaminants residing on the equipment or object. Sprayed air is designed to blow in multiple directions and can exceed velocities of 25 m/s in certain models.
Image Credit: ESCO