Flexible Containment Development in a Rapidly Evolving Environment
Like other forms of containment, Flexible Containment has evolved as a viable solution to serve the needs of today’s rapidly advancing technical needs.
Airflow Controlled Containment
Had its roots in the days of open experimentation to prevent the user from being overwhelmed with chemical fumes, and debris from accidental incidents. Today it exists as the primary control for dispensing, with evolution including snorkels for local pickup, sophisticated Airflow enclosures including Biological Safety cabinets, and the technical wonders from vendors who invested in development of airflow models to create small enclosures which overcome the intervention of personnel habits as much as possible. User work practice still dominates the outcome.
Evolved because Airflow Control was insufficient to isolate radioactive materials from both the workplace and the outside environment. Early development was funded under Government directive, which still has a major influence. The US space program had need for materials isolation with protection from an alien entity as its goal. The containment initiative picked up when the Pharmaceutical Industry started development of highly potent materials, but still relies heavily on the vendors’ concept of putting your equipment into their enclosure.
Powder Systems Limited (PSL) stands out among today’s vendors because it evolved solely from industrial needs in the Chemical and Pharmaceutical world. By prioritizing the study of the materials handling process, they take a unique approach of minimizing the dependence on rigid containment, with as much of the process accessible outside the Containment Enclosure as possible. In this way PSL minimizes Glovebox design and cost, while optimizing materials access. Finally, by conditioning the internal surface to minimize corrosion and optimize cleanability, PSL is able to ensure that cleaning turnaround is effective.
Evolved more slowly than the above concepts. Flexible Containment was first developed in the 1950’s for handling low-level radioactive waste as an economical pass-through out of a Glovebox. The flexible containment concept came to the forefront with nuclear powered vessels, which required extensive containment during maintenance turnaround, since Rigid Containment was impossible to install with the limited access. Rapid advances in Flexible Containment occurred when the Pharmaceutical Industry began to realize the potential for installation because Rigid Containment is not feasible at many points in research, development, manufacturing, deployment, shipping, and third party handling. It has taken a long time, since 1993, for other vendors to realize that Flexible Containment is a technology in its own right. With this insight, the technology is rapidly advancing with evolutionary changes leading to entirely new concepts in contained materials handling.
Rationale of Rigid and Flexible Containment
Both evolve from the same basic concept - design and build what is initially a gas-tight enclosure. To this you can now add vents, pass-throughs, instrumentation penetrations, etc. in such a way that the integrity of the envelope remains uncompromised other than by intent.
The technologies have different size limitations, weight, utilities requirements, adaptability, design and delivery cost, speed of transition from prototype to final functional item, and Flexibility – which is where the two Technologies most part company. The very fact that both have their own attributes has been realized through a working collaboration between flexible (FabOhio Inc.) and rigid (Powder Systems Limited) fabricators. To this end, new product concepts that benefit from a combination of the two technologies are beginning to emerge, and will provide clients with more design freedom in applications.
Flexible Containment adaptations for the Pharmaceutical Industry
The earliest known Pharmaceutical application was a series of fully contained, and dockable, enclosures built by LaCalhene (a company versed in Rigid Containment) for a French finishing facility. Photographs of the entire cart mounted system were in circulation in the early 1990’s, but sadly no data or user information was released.
The second known application was in 1993 when a feasibility test for dispensing bulk materials into, and out of, 55-gallon drums was conducted. The enclosure was made of polyethylene film sealed together using duct tape. It consisted of a Glovebag style top, with the sides attached to a dispensing table using ChemTape. Testing was performed by dispensing operators, in an unused chill room, having no ventilation flow. Drum-to-drum dispensing testing was performed several times. The dispensed powder was an antibiotic material having a Dustiness Index of 11% (Heubach method), and 14% after milling. The quantitation limit was 0.05 µg/m3. Despite trying several methods to seal the sides to the rectangular dispensing table, it was not possible to achieve acceptable performance. This is when the first Pharmaceutical Glovebag Fabricator (FabOhio Inc.) entered the picture, with 30 years of prior experience in the nuclear and heavy industries, who advised the use of a Glovebag with an integral floor. This approach proved successful and established a working relationship between the Pharmaceutical Company and FabOhio Inc, with FabOhio Inc. providing continued support through advice on design as well as rapid turnaround on new prototypes and final working products. This team effort led the industry for several years, delivering formal presentations of designs and performance results at professional and trade events.
Another containment vendor entered the picture in 1995 with a concept for on-line packaging, with the same Pharmaceutical Company providing financial support. The simultaneous development and production use of a continuous liner by a second Pharmaceutical Company, plus the impetus provided by their own previous successes convinced management to fund a rapid development project at a cost of $3 million and resulting in a marketable product line.
Flexible Concept Evolution
1) 1993 – 1995 Localized containment in conjunction with the design of a new containment building.
Fugitive release sources are common in most materials handling facilities, with numerous small, localized fugitive release locations. Drips and aerosol releases occur when process lines are pressurized, e.g. equipment pressurization using compressed gas or pumps. Such releases are sporadic and often missed during casual observation. Gasketed seals eventually wear and give rise to emissions. Sites have prepared for this by using discrete enclosures made to enclose the release point. With releases being transient, the enclosures are fitted with passive HEPA filters and internal sorbent pads. During normal building operations, when the sorbent pads show evidence of staining due to residues left behind after the solvent has evaporated off, it’s time to take remedial action.
Additional small adaptations include small flashlight enclosures for use when inspecting dirty areas, and even creating drainage from an inaccessible decontamination pool.
2) Support Frames
The early flexible enclosures required support frames to which the enclosures were anchored using suspension cords and later using Velcro strips welded to the enclosure. FabOhio Inc. demonstrated the inflatable frame Glovebag in 2003. This approach eliminates the need for an external frame. The technology is currently capable of supporting enclosures as tall as 4 ft. The image demonstrates how lightweight the enclosures can be made.
3) Sloped viewing window
Sloped viewing windows installed in rigid enclosures have been available from Powder Systems Limited since 1989.
Typical design approach for rigid rectangular enclosures follows the general Guidelines of the American Glovebox Society Publications, i.e. typical reach of 21 inches. Accommodating operators of differing height and girth with this constraint, while also providing good visibility, was overcome in two ways:
- The top of the operator’s window is sloped at an inward angle. This was first introduced for an inflatable frame enclosure in 2003.
- The amount of slack in the inflated frame enhances the operator’s reach. All sides of the flexible enclosure have controlled freedom of movement due to the elasticity and mobility. Combined with the sloped front window, this allows multiple users to reach several inches further than the Guidelines recommendations.
Once demonstrated for an inflatable frame enclosure it was a simple matter to apply the sloping window to frame mounted enclosures. This approach addresses both viewing and lighting challenges. Combined with the improved elasticity and flexibility, the operators experience optimal working conditions for any containment need.
4) Bottom Discharge
The floor of a flexible enclosure is normally supported by a solid table surface. Pharmaceutical Glovebags evolved from the need to contain dispensing operations. Creating a hole in the underlying table allowed for a bottom-mounted Glovebag sleeve to become the discharge chute for dispensing into a drum or reactor opening. This concept has been adapted to create a controlled handling method, e.g. by adding a Cam-lock fitting for charging vessels. Adaptations and uses of this design are without limit.
5) Development of Cleaning Methods
One-use flexible enclosures are simply collapsed after use and placed in a burn drum, creating minimal waste with negligible environmental impact. Enclosures intended for reuse require a cleaning method that creates minimal waste volumes. FabOhio Inc. pioneered simple but effective cleaning methods for different size enclosures – from small laboratory enclosures, through intermediate size, e.g. rework or centrifuge enclosures, to full-scale manufacturing suites. In all cases, the methods were developed to minimize waste volumes. Typical waste generation ranges from 20 cc to 20 gallons of liquid depending on enclosure size. This allows for more complex enclosures to be reused with a minimum of time, effort, and operator training.
6) Integral Support Floor
Flexible enclosure design has long followed the Glovebox concept, i.e. intended for use at a single location. Just as for Gloveboxes, materials transfers require overpacks and special handling procedures. Enclosures also occupy existing hood or bench space, which is often at a premium. The potential of Flexible Enclosures, especially Glovebags, that do not require fixed utilities is overlooked. Adding a freestanding floor support, which is attached to the Glovebag, allows Glovebag use on any horizontal support surface such as a marble weighing table, and the surface need not even be as large as the Glovebag floor. The first model was on display at INTERPHEX 2016.
The image shows a Glovebag having an inflated frame, which makes it light to handle. A more permanent structure can be made using a solid frame mounted to the floor support which limits the user to a single Glovebag design, plus additional weight.
The Glovebag support is a one-time purchase, which provides extended use.
With an integral floor support, a Glovebag can be placed on any cart, making it mobile. As long as the Glovebag base and cart are narrower than doorway openings, the assembly can be wheeled to different locations. Since materials are fully enclosed within the contained space, the Glovebag cart can move freely through public access areas and even be transported within and across sites with ease. This does require handling the enclosure assembly appropriately to protect it from damage. This mobility eliminates packing materials in overpacks and removal from the enclosure. An additional feature is the ability to lift the enclosure, with contents, from the cart at its destination. Without disturbing materials inside the enclosed space, the inflated frame Glovebag can be reduced in height, requiring less space for temporary storage in a safe place. When needed at a later date, it is a simple matter to remount the Glovebag onto a cart and transport it before restoring the Glovebag to full height ready to resume operation.
The concept was displayed at INTERPHEX 2016.
Should the Glovebag require purging with inerting gas, it is a simple matter to attach a laboratory sized utility canister to the cart during transport and storage.
8) Two Sided Access
Adding an integrated support allows greater freedom in enclosure design. When mounted on a free-standing table it provides access from all directions. This makes all external faces available. Operator access can be increased by adding glovesleeves on two, or more, sides further increasing the working range beyond the nominal 21 inches. When designing for an inflated frame design, optimum viewing and lighting is achieved. Operators appreciate the ability to have additional operators hands available to assist, making materials handling easier, more secure, safer, and less strenuous.
INTERPHEX 2016 was the first time this configuration was presented.
When creating a mobile design, doorway access is a limiting factor to the support footprint.
9) Enhanced pass-through sleeves
Another Technical Bulletin entitled ‘Microparticle Challenges for Containment’ discusses the need for microparticle containment. The concept required that the contained enclosure be completely isolated from outside environments. The collaborative program between FabOhio Inc. and Powder Systems Limited is focused on achieving this goal. A new approach to both designing and using pass-through sleeves for this function has been created. The result is a concept that can be employed for any materials transfer involving contained spaces, for both flexible and rigid enclosures.