Designing machines for cleanrooms

Cleanrooms are generally clean until you put something in them, and it is what you put in them that gives everybody the headaches. It is well known that a human being is probably the dirtiest thing in a cleanroom, but machines, if not properly designed, can come a close second. GMP in machine design is as important as the practice of GMP in the cleanroom itself.

As with general practices to maintain cleanrooms, the aspects of machine design for cleanroom suitability are complex. In machine design, one can often regard GMP as common sense, but it is common sense tinged with a large dose of experience. The overriding requirement is to be able to keep the cleanroom and the machine clean, and to be able to check that it is clean. Also, it is necessary to ensure line clearance procedures between batches are effective, avoid cross contamination, and above all maintain the integrity of the product. Under these circumstances it is particularly important to ensure that contaminating elements of machines are either designed out or contained. This is especially important if the machine is subjected to high wear and use. From a general design perspective, the more open the machine, the easier it is to keep clean. Unfortunately, this open design often conflicts with health and safety requirements, and guarding can often be a major hindrance to good GMP. It is therefore always important that guarding concepts are considered within part of the overall machine concept and not added as an afterthought. Further, balcony style machines, as pictured left and below left, are often preferred since they normally separate the drives and controls on one side of the back plate from the functioning elements that handle the products on the other. However, such balcony machine designs are sometimes not practical on wider machines; a good example of this is thermoforming-type machines that fundamentally require two side plates to carry the drive chain mechanisms. Lubrication requirements should always be considered in any cleanroom application. Balcony machine design normally has the advantage of having almost all lubrication points and the majority of the bearings on the back side of the back plate away from the process. Even if the balcony design is not employed, lubrication points should either be well away from the product or the process, or at least below the level of the product or process. Further GMP features include: ensuring there is adequate ground clearance beneath the machine for cleaning; designing the machine such that there are no areas to trap product, which is essential if effective line clearance is to be maintained; and ensuring dust or collection trays can be removed for inspection and cleaning. Another important consideration is potential contamination from exhaust air. All exhaust air, regardless of the source, should be either filtered or routed through to a single exhaust point for extraction from the cleanroom. Components, such as bearings, that have the potential to generate particulate or other contamination, should ideally be sealed for life. Sealed for life bearings are not always of sufficient grade under arduous applications and those that require regular lubrication often have to be specified. In these cases, centralised lubrication is often advocated by engineers and preferred by maintenance engineers, but there is a contamination danger in a cleanroom if the destination of the lubricant cannot be observed. Over-exuberant use of a centralised lubrication system can lead to some serious contamination within the machine without it being recognised if the destination of the lubricant is not visible. If in doubt, Doyen advocates the use of single lubrication points that are monitored individually. Component selection In the design of any machinery, the selection of the constituent components is a vital factor in ensuring the machine complies with requirements. In cleanroom applications, brush-less motors and enclosed slip rings are both obvious candidates for selection. Further, the type and grade of drive belts and the general drive train design can have a massive impact on the suitability of the machine for the cleanroom. Wise designers choose components that exhibit little or no fibre shedding, and this is particularly important on drive belt selection. If you are in any doubt over the suitability of a machine, just check for dust build-up below the various drive constituents to establish the likely contamination levels. Finally, a checklist to help you in a machine selection for a cleanroom: • All machine areas should be accessible for cleaning and have sufficient ground clearance for cleaning and visibility • All lubrication points should be adequately separated from the product. If a central lubrication system is used, can all the lubrication points be witnessed during the act of operating the lubricating system? • Select sealed bearings wherever possible • Use brush-less motors and enclosed slip rings, and any other item that is prone to generate dust should be enclosed • Exhaust air from any device generating air should be filtered or routed to a central exhaust point • Drive train should be tooth belt and non-shedding • If necessary, check that food grade lubricants are being specified and used. The final point is the discipline in cleanrooms. I have no doubt that most companies exercise substantial discipline over their employees on the access to, and activity in, cleanrooms. It is important that all service personnel from your machine suppliers operate to the same high level of cleanroom standards that you do. Happily, there is now a passport scheme supported by the PPMA under the PharmaChem Group that ensures that the service engineers entering the pharmaceutical or medical environment are properly trained in not only safety but also cleanroom, validation and GMP procedures. sales@DoyenMedipharm.co.uk Tel: +44(0) 1223 264300