Vijayakumar, Ph. Good practice dictates testing the performance of all filters for their overall efficiency, integrity, or absence of leaks. The article mentioned that filters are typically tested both as manufactured and after installation. In addition, many cleanrooms in regulated industries such as the pharmaceutical or nuclear facilities require these filters to be certified periodically as installed to ensure acceptable performance during their service life.
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Vijayakumar, Ph. Whether the cleanroom attains and maintains its designed cleanliness class depends largely on the performance of these filters. Hence, it is a common and good practice to test the performance of all filters installed in cleanrooms to ensure that they meet the designed specification.
Filters are typically tested as manufactured for overall efficiency and leaks. Furthermore, in many cleanrooms within regulated industries, such as the pharmaceutical or nuclear industries, these filters are also required to be certified periodically, to ensure acceptable performance during their service life. RPs It has been revised regularly to keep it relevant to current industry practice.
In its fourth and current revision, this RP remains current and compatible with the state of the art in the industry. The main goal of this revision is to make the filter classification compatible with the common test methods used by the filter manufacturers.
Further ambiguities and errors in the definitions have been addressed, and significant information on several related topics has been added in the appendices. The new filter types Types H, I, J and K are based on filter testing using a particle counter, and complement the original filter types A, B, C, D and E that rely on photometric test methods.
Although no equivalence between the methods has been established, the new filter types should assist the manufacturers that test filters with one or the other method. The requirements have been set stringent enough that the filter types in the RP based on either of the test instrumentations should be acceptable for the end user seeking a filter of a defined performance.
The different filter types and their test requirements are shown in Table 1. Click here to enlarge image Most technical documents and standards use special terms and abbreviations; this RP is no different. Over the years, familiarity with many of these common terms has meant that errors in their definitions have gone unnoticed.
This revision has taken great pains to address many of these errors, which include: The 0. The size of these aerosols intuitively understood i. Since the efficiency of filters varies greatly with particle size, these new terms have been defined in an attempt to elaborate and clarify the differences. Count mean diameter CMD is the average particle size of the number distribution of the aerosol.
Mass mean diameter MMD of the aerosol is the average particle size of the mass distribution of the aerosol. Typically, since the mass of a particle varies with the cube of its diameter, most of the mass of an aerosol tends to be in the larger sizes, resulting in the mass mean being larger than its count or number mean. Understanding the difference is significant since the filter efficiency is size-dependent i.
The filter types listed in the RP explicitly take this difference into account, thereby eliminating the confusion surrounding the subject. Particle size distribution of aerosols from common generators is noted in an effort to eliminate any confusion regarding the merits of using one or the other type of generator.
The HFATS took advantage of particle-sizing instruments, which are capable of providing information regarding particle-size-specific filter performance.
It also allowed the use of liquids other than DOP and at a much lower concentration to test the filter. The major drawback was the increased amount of time to test a filter, as well as the increased inherent variability associated with the particle-sizing instruments.
The committee developed the ASME AG-1 Section FC, Code on Nuclear Air and Gas Treatment, and includes codes and standards for design, fabrication, inspection and testing of air-cleaning and air-conditioning components and appurtenances, as well as air-cleaning components used in engineering safety systems in nuclear facilities. In particular, it covers the design, operation and testing of all HVAC system components.
EN is the European standard that combines filter classification, testing of filter media, overall filter efficiency testing, and leak testing into one document. Although no direct equivalence between the standards is possible, they have many similarities as well as several key differences. EN utilizes single or discrete particle-counting instruments for all aspects of testing filters with efficiencies of Unlike IEST, EN allows for the computation of filter collection efficiency based on the particle count data collected during the scan test.
This RP, much like other standards, strives to keep abreast of current practices. How well it delivers on this promise depends to no small measure on the input of the many professionals in the contamination-control industry. Suggestions and input on current practices are always welcome by the author and IEST.
Better yet, come join the working group WG deliberations and share your insight into this and other key topics addressed by the many RPs published by IEST. Acknowledgements: Without the input, urgency, and lively debate among the members of the working group, neither the timeliness nor the quality of this RP would be possible.
As chair of the WG, I thank them all for their support. Vijayakumar holds a Ph. He has held senior technical and marketing positions in leading filter, filter media and particle instrument companies, where he has assisted customers worldwide with their filtration and filter-testing problems. He also held the position of Chair of Standards and Practices from to He can be reached at vijay tsi.
IEST RP CC034.2 PDF
Global semiconductor sales increase This phenomenon is referred to as bleed-through, or excessive widespread nonsite-specific penetration in leak-testing. IBM lest strategic partnership with Samsung to include 7nm chip manufacturing. Would Apple change the power GaN world? The nominal acceptable criteria for the uniformity are as follows: August 30, Sponsored by Cc In comparison, the cross section of a scan head is about 0.