Anything that serves to block movement can be an isolation barrier, from a quarantine fence around an ebola treatment camp to the steel walls of a processing tank. While rope, fence or partition barriers can be used to block the movement of people, and lead or concrete barriers are used to block radiation, options are more tightly defined when gas or liquid molecules must be blocked.
The barriers used to block movement of air or gas require continuous solid material that is fluid tight or “air-tight” so that pressure or flow on either side of the barrier produces no flow through it. Isolation by use of these air-tight fluid barriers is the sort we discuss here more than any other kind.
Barrier Isolation Enclosures
When a process work space is surrounded by an air-tight physical barrier, it is a barrier isolation enclosure. Such isolation enclosures may be equipped with valves, temperature controls or other process systems, and they may provide for direct user interaction. When the enclosure or workstation is equipped with attached gloves for access to the work zone it is called a glove box, glove bag or barrier isolator.
This sort of glove box is a common implement for handling the most sensitive or hazardous materials.
Used in pharmaceutical compounding, nuclear processing, research and development and many other types of applications, barrier isolation glove box workstations are found in many compounding pharmacies, university laboratories, and research institutes.
Controlled Atmosphere Isolation
Pressurized, special atmosphere or controlled atmosphere isolation is a form of barrier isolation where a specific gas recipe is created and maintained inside a work or process chamber. This type of controlled atmosphere enclosure is generally the isolation option that offers the most reliable, high-purity process option when requirements demand high performance. It is the most efficient solution for users that require pure conditions, but aren’t prepared to consume large quantities of gas by continuous purging.
Like any important trip, the journey to a successful process outcome will only end well if we know where we are going when we buy our ticket. Controlled atmosphere isolation choices and planning require a thorough understanding of process objectives and requirements, so that isolation systems can mitigate contamination risks and support practical operation.
Specify Your Isolation Environment
Effective special atmosphere planning demands research to specify practical limits of materials and process contamination tolerance, because
contamination is INEVITABLE, but the degree of contamination depends on isolation choices.
When a manager requests an oxygen-free process atmosphere, we may ask “how much oxygen can the process tolerate?”. When the manager responds “none. It must be oxygen-free” we know that she has not done the work required to choose a practical isolation solution.
Since we don’t live in a universe where ALL oxygen molecules can be purged from the process work-space, the process owner is left with the following options:
- Avoid addressing the question of limits and just choose something (i.e. throw the dice)
- Choose an equipment supplier that will say what we want to hear, without regard to the truth
- Spend massive funds on the most theoretically powerful isolation system, to get closer to zero oxygen and hope that this complex system will work, and the isolation that falls short of zero will somehow be good enough
- Actually find out the real process tolerance limits, and choose isolation systems accordingly
On Target Beats ‘Go Big’
Effective isolation demands clear process objectives and carefully defined process limits that are practical and achievable. It is critical that the objectives and limits are chosen based on an understanding of the physics and dynamics of the process. This should be done prior to choosing an isolation system. If completed logically and carefully, it leads to great isolation results that can support practical process objectives. If done haphazardly, any capability of the isolation system to achieve process objectives is a stroke of luck.
When the approach is blind overkill, greater system complexity, additional testing and calibration and greater operational workload will be needed. Such ‘Go Big’ approaches to isolation also require more physical space, more infrastructure, more installation effort and skill as well as more time, money and labor to execute.
The reliability of such systems is nearly always lower, the schedule for deployment is longer, and the risk of quality problems, cost overruns and overall failure is greater. The extra operating labor, maintenance labor, site infrastructure, downtime, shop/lab real estate, and capital required for such overkill generally are pulled away from the primary process project effort.
A Snug Fit is Best for Isolation
The investment in isolation over-kill is generally made to avoid isolation problems and guarantee project success, but that rarely works. Such actions are naive, and result from inexperience. If you were totally unfamiliar with central heating, and needed a furnace for a large building in Norway, you might be tempted to go overboard. If you chose to heat the building with a nuclear reactor, your chances of getting the project completed on schedule and under budget would be dismal. Isolation systems offer the same penalty for overkill.
A smart, right-sizing approach will produce better, faster, more efficient isolation results, with far less risk and a lower investment. This doesn’t mean that we can get there without effort or care. To plan for the ‘snug fit’ that right-sized isolation demands, we must know a lot about the process to be isolated and the physics of that environment. This always demands careful consideration and generally requires research. It may require expert consultation or experimentation. Even considering this extensive front-end preparation, right-sizing is a prudent investment that nearly always brings an impressive return in reduced risk, better results and a quicker more positive conclusion.
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