High efficiency filtration

Industries such as pharmaceutical, microelectronics, optoelectronics, microbiology and medical research establishments, which require machine generated test certificates that provide traceability, and can be called upon by other agencies, for example the FDA (Food and Drugs Administration). Manufacturers of cleanrooms, clean benches, safety cabinets containment and extraction systems, and also consultants can rely on BS EN 1822 tested filters to perform to their design specification. The BS EN 1822 Test Rig has been designed purely for testing mini pleat HEPAs and ULPA air filters, ranging from H13 to U17 classifications. The equipment is regularly calibrated to ensure that consistent performance can be guaranteed. The test rig works by measuring the MPPS (most penetrating particle size) efficiency of the filter, which is a more realistic method than previous test, which gave an efficiency against a fixed particle size. EN 1822 is the first European wide standard introduced to provide a uniform classification for HEPA and ULPA filters. Prior to the introduction of this new standard, filter companies in the UK worked between the British Standard BS 3928, Eurovent 4/4 or DOP scanning methods. Cleanroom design was based on the US Federal standard 209E or British Standard 5295. With filters tested in mainland Europe, to French, German or other standards, and cleanrooms constructed to different standards in each country, it was essential that a single European standard was written. In 1990 the original working group TC195/WG2 from the Committee for European Normalisation (CEN), met to start work on a new standard thatwould be introduced to standardise classifications throughout Europe. It was several years before the first drafts of this new standard were issued and the HEPA/ULPA filter test section of the new EN1822 standard was finally implemented in 1998. (UPLA, or Ultra Low Penetration Air is the highest quality of air filter available). The Test Rig installed by McLeod Russel fully meets the stringent requirements of the new standard. Each filter is automatically scanned with the test results printed, showing local and overall efficiency figures. It uses Condensation Nucleii Counting (CNC) equipment and an illustration of the sensitivity of this test rig is that it can detect five particles in 10 million, down to 0.06 microns. The equipment detects particles with continuous upstream sampling with dilution and two sampling heads downstream with automatic and manual scan capability. CNCs enhance particles by condensing alcohol on the particle in such a way that it enables the counter to detect them. This process allows the detection of most liquid and solid aerosols. The definable particle size range for the mono-dispersed aerosol used to test the filters is selectable from 0.12 to 0.25 microns count mean diameter. (A micron is one millionth of a metre and 10 microns is the smallest entity visible to the naked eye). This range represents the Maximum Penetrating Particle Size for ULPA and HEPA filters. In terms of performance, the HEPA range removes from 99.95 to 99.995% of all 0.18 micron particles. A high grade ULPA for example would remove up to 99.999995 of all 0.12 microns, i.e. it is allowed to pass only five out of every 10 million 0.12 micron particles. Such efficiencies are necessary because the processes the filters are required to protect require air cleanliness levels sufficient to ensure that the products being manufactured, such as in the pharmaceutical, microelectronics and biotechnology industries, are free from contamination. If filters fitted failed to provide the required cleanliness standards of the processes, the primary result in an installed facility is that, if properly monitored, the process would not be able to operate - as the level of contamination would result in product rejects, product failures, impurity, health hazards etc. In pharmaceuticals, clean air is required for a large proportion of all processes that result in the production of drugs and medicines. The effectiveness of these products is largely related to the purity of the constituents of which they are made. Today we are used to highly concentrated products and clean air plays an important role in enabling this. In microelectronics, the presence of unfiltered air during manufacture could severely affect the reliability of printed circuit boards used in equipment we all use, the most common example being the processors in computers. Unreliable manufacture would increase the cost of production and hence the cost to the consumer. We are all used to faster and faster speeds of production. Without clean air the development of this technology would be almost impossible. In biotechnology, research into diseases that affect mankind and the animal world can only be accomplished within a controlled environment such as is produced using HEPA filtered air. The efficient separation of dangerous substances from the air protects the worker and the environment. In the medical world we are becoming more used to the benefits of Ultra Clean Operating Theatres in hospitals where the environment is controlled with high efficiency filters. This prevents the spread and distribution of bacteria, which has been an all too familiar result of patients undergoing surgery developing secondary infections. Clean filtered air is the primary method of control. In the food packaging industry the presence of a controlled environment, such as is provided by clean air, is fundamental in ensuring the longest possible "life" from production to use. As consumers we are used to having the maximum choice of fresh produce available to them, be they edible foodstuffs or drinks. Such ability is closely linked to the use of clean air. In all of these examples you can appreciate what would happen if the correct level of clean air were not available due to the use of inappropriate filters. It is therefore essential to maintain the quality of the filters installed. The way filters are tested depends on the application. The higher level of efficiency, the more sophisticated the test method has to be to ensure reliability in service. The EN 1822 test rig offers the highest level of integrity, using a closed loop system, which does not hamper the test result – and the result clearly printed on the product label. In-house testing means there are fewer failures on site and hence increased surety that any failures are due to transport and handling ex-works rather than in-works, which helps with faultfinding. End-users can be confident in product integrity, while re-sellers save costs by purchasing products which they know have been tested to this standard, thus reducing the risk of failures and batch rejects. Stringent methods associated with the EN 1822 test rig include the rule that filters can only be tested twice. Travelling at a controlled speed, the XY system incorporates a scanning head, which scans the entire filter face, searching for any particle penetration of the media. It works out the local efficiency and then calculates the overall efficiency. If a filter fails the test by exceeding the local value then, the scanning head will re scan the suspect area again using the relevant co-ordinates and calculating the exact figure of local penetration. If it fails again then the filter must be repaired or rejected. Only certain repairs are acceptable; these are clearly defined within the Standard, and must not affect the quality appearance of the filter, or its overall specified performance. The test rig is highly adjustable and can test filters ranging from 305x305mm up to 914x1829mm. By making certain adjustments it will be possible to accommodate even larger filters. Once a filter has passed the test, it is given a unique serial number, the efficiency, pressure drop together with other relevant information are included on the filter label. This information provides the client with the assurance that the filter has been subjected to the most stringent test available and passed. Clearly, the primary advantage of using the EN 1822 test rig is absolute confidence that the filter has been 100% tested. This automatic test method is up to 1000 times more sensitive than traditional test methods. It is now possible to certify filters to U17, which was previously not possible. The EN 1822 test is not reliant on the test operator hand scanning the entire filter face and recording photometer readings manually. With the EN 1822 test rig, clients can be assured of a reliable product, which has undergone the most stringent of tests.

Contact Kirstie Niland Tel/fax: +44 (0) 1772 768706 Email: kirstieniland@aol.com