Is the glovesleeve the weak link of a containment system?
To maximize containment, all aspects of the glove and sleeve must be routinely inspected and tested
By Russell E. Krainiak, Integrated Containment Systems
As an isolator designer and builder ultimately responsible for operation, the question of the glovesleeve as a weak link is very complicated for this author. The application drives the wear, age, and how an operator performs the tasks to determine when a glove should be changed. A typical pharmaceutical user will ask “How many months?” in trying to determine when the glovesleeve is to be changed, but it isn’t that easy to determine from case history. The technology is still new to this particular industry that likes to know up front every detail of what to expect.
The intent of this article is to provide some of the details of glovesleeves, gloveports, and maintenance for keeping glovesleeves safe, thus keeping the entire operation safe and controlled. Testing is a very simple maintenance task, but some companies do not test the gloves and glovesleeves; examination is important, but they often are not examined. There are other factors to prevent actives from egress of an otherwise robust containment system. These will also be discussed.
The nuclear industry has used gloveboxes for more than 40 years. In the early years, the glovebox was a necessary device to allow access to radioactive materials for the purpose of making and servicing a weapon. The nuclear industry shares many of the same problems as the pharmaceutical industry. Glovesleeves are used to access almost everything these technicians process and similar disciplines share the same concerns. If a glove leaks, will the product escape?
The first nuclear gloveboxes were transitioned to isolators by the manufacturers. There were many design changes to accommodate cleaning, which was not as critical in gloveboxes. Cross-contamination was not as much of a concern since the glovebox product was very different. The failings of gloves always raised the same questions: when, where, and why did it happen?
Some gloves on nuclear gloveboxes have been in place for five years without leaks. As demonstrated in papers presented and forums from the American Glovebox Society (AGS),1 this length of time before failure is possible with proper maintenance and sometimes by limited use. Training is cited as being critical to the safety of the operator.1 Some glovesleeves leak starting out of the new package, which most likely occurs due to storage problems.
Figure 1. Today’s isolators incorporate test programs to ensure glove and sleeve viability. Photo courtesy of Integrated Containment Systems.
One thing the nuclear industry understood from the history of glovebox usage was leaks can contaminate the room, the facility, and the outside. Monitoring equipment is used so operators cannot leave the facility without being cleared. There are other reasons for monitoring outside the scope of this article; if a glove has a hole or tear, the risk is imminent. Most pharmaceutical facilities do not routinely perform tests that detect active pharmaceutical ingredients (APIs) for operators working in the containment facilities. Some operations do require blood tests to determine past exposures, since it is the only way to determine exposure. Operators can go home, spend time with the family, and potentially spread APIs. For this reason, the pharmaceutical isolator must have certain additional safety features and qualities.
Glove materials and types
There are several glovesleeve designs and materials available for gloves. Deciding which is appropriate for an application is dependent upon the application. Hypalon, neoprene, and butyl are the most commonly used glove materials that withstand many cleaning chemicals. Chemical damage can occur and should be considered in the design phase. All chemicals–cleaning and process–should be checked for resistance with the gloves to be used. As an example, researchers use multiple chemicals in isolators as part of their daily operations. Every chemical should be checked against the materials of glove construction just like the isolator seals. Sometimes the gloves can be changed to another material, but there are some chemicals that degrade all available glove materials. For this reason, manufacturers maintain resistance charts as part of their web sites and company literature.
Another factor to consider is mil thickness of available gloves. A thin 15-mil glove is chosen for dexterity when doing intricate weighing (such as analog weighing). When the technician will perform scooping operations from a drum, a thicker 30-mil glove is chosen for its robustness.
Operations dictate the selection of glove type and thickness but also consider hand size. Multiple operators are another variable in the design, with hand size and dexterity as factors. The gloves are available in ambidextrous and left-right hand types. After the material is selected, the designer has to choose the type of glove, thickness, hand size, and whether it will be a left-right hand type. Note that some glovesleeve manufacturers only offer their gloves in certain sizes. When choosing a glove for multiple operators, the tendency is to go to a larger glove size to accommodate more users. Another type of glove is the changeable hand type. This allows changing only the hand glove portion of the assembly; the sleeve stays with the gloveport and allows more variety of hand sizes than a single-piece glovesleeve arrangement.
The gloveport is the attachment for the glove and is critical to the life of a glovesleeve. Friction from movement of the glove against the ring can lead to holes and tears. Most of this friction is caused by ergonomic problems that may have been designed into the isolator or result from continuous usage. Isolator manufacturers generally have proprietary designs that range from 8- to 14-inch diameters. Both oval and round versions are available. Most operators favor a large, round gloveport that provides more side-to-side and up-and-down movement. The first gloveports used on gloveboxes were 8 inches since shielding an operator’s chest was critical. Pharmaceutical workers can use much larger versions because they spend more time working in the gloveports and do not need radiation protection.
The two factors that lead to failure are repetitive motion and finger contact areas. These wear areas, like tires touching the road and wearing, are generally at the fingertips, which see the most contact and will eventually wear holes through the glove. One company manufactures a white-coated Hypalon urethane material that is a dark blue color. When the Hypalon wears off, this indicates the glove should be changed. The area where the glove constantly rubs against the ring is another wear point and should be examined and tested routinely; this is especially true for extreme reaching in an isolator. In the design phase, constructing a simple mockup to evaluate ergonomic problems in this area will allow design adjustments to be made accordingly.
Everything that fails does so for a reason. In the case of a glove, this is generally caused by repetitive wear or physical damage. What tests are available, how can you test a glove installation, and what is the best way? First you must understand how the glove works in an isolator.
Figure 2. Oval gloveports limit horizontal movement. Photo courtesy of Integrated Containment Systems.
A glovesleeve is maintained for containment isolators under a slight negative pressure, usually less than 0.5 inches water gauge during production. The pressure is imposed by the pressure drop across an inlet filter set up to flow around 100 fpm through a breached gloveport (“breached” meaning a glove completely removed for testing purposes). Although there is some pressure surge with an isolator, it doesn’t normally damage most glovesleeves. When gloves are moved for entry into a set of ports or exiting the ports, there is a surge that shouldn’t bring the negative pressure to a positive pressure but will be very close. If a leak exists in a glove, this is the moment that particles could penetrate through the hole, depending on size of the hole and the number of particles. Depending on the operator exposure limit (OEL) over time, an operator could be exposed to harmful amounts of substances. The size of the hole and how much can egress through it and at what velocity also varies. This is the justification for testing glovesleeves prior to use.
Figure 3. Round gloveports offer better range of motion. Photo courtesy Integrated Containment Systems.
Pressure is the most widely used method of testing gloves. Some will insert a plug on the outside of the ring and seal it. This is the best test method since it challenges the entire gloveport assembly in the installed, ready-to-go state. Pressure is applied to the plug and time is used to determine a preset pass/fail condition. Some test systems only challenge the glovesleeve, requiring the existing glovesleeve to be removed in order to perform the test, which works best with a new glove installation. The system uses pressure as well, but, again, only the glovesleeve is being tested, not the ring seals that lock the glovesleeve to the gloveport.
Following on the recommendation for daily testing of gloves used for low OEL applications, the trend has been to automate a glove and isolator pressure integrity test at startup of an isolator, prior to production or use. This can be a very simple way to maintain the safety of the operator; it allows a PLC to perform these testing functions by pre-validated pass-fail parameters. A PLC, unlike an operator, runs to a pre-validated program in a consistent manner that is not changed by the operator. The manual setup of an isolator for testing leaves room for error by depending on standard operating procedures (SOPs) being performed consistently. Most isolators that are set up manually are used for higher acceptable exposure applications. A PLC pressure integrity test for leaks is as simple as using the blower and inlet-outlet control valves to encapsulate the volume of trapped pressure. This helps identify the leaks on the isolator and glovesleeves. If it is determined that a leak exists for the glovesleeves, the next challenge is to determine which glovesleeve is leaking. A plug can be placed into the gloveport and sealed. A pressure line runs to a transducer to measure the pressure trapped in the glovesleeve and gloveport cavity plug. If the cavity shows negative pressure, it is leaking; if not, it is functional. These parameters can be set and controlled by the safety personnel. Using PLCs to perform the test function reduces time and money spent on testing and ensures the safety of the system. The other advantage, based on actual users in isolators, the unit passes the test most of the time, negating a “find the leak” element of the test since the glovesleeve is tested with the isolator as one volume.
Isolators are predominantly built from stainless steel, with welded and sealed construction that can maintain the pressure boundaries that separate the worker and the API or hazard within. The openings, predominantly gloveports, are susceptible for one reason: This is where the wear and movement take place. The design of the isolator can add to the wear of the glovesleeves since a design that is not ergonomic can lead to stretching, yielding damage to elastomeric glovesleeves and tears that could result in exposures. Although the available materials are quite robust, continued and repetitive movements will lead to early replacement of glovesleeves.
Another glovesleeve failure observed by pharmaceutical companies includes extreme negative pressure, operating at around <1 inch water gauge. The excessive pressure will fatigue the operator, who must struggle with the glovesleeves for even the simplest movement. In this situation, the operator will have failures based on certain fatigue areas where creases are created and continually fold in the same location.
Training is essential for any new installation and new technology. Training is conducted by the isolator suppliers because they are equipped to understand the operation and maintenance of the equipment. The weak link is how to do it safely regarding the gloves’ weaknesses and strengths. This supplier training is rarely conducted in any detail for each custom isolator project.
General training for operators is provided by the AGS at its annual conference. Attendees learn physical anthropology, how to work in a glovebox/isolator to avoid injury, and how to maintain the safety of the unit. Since many smaller pharmaceutical operations are not equipped to perform training within their facilities, this specialized training is a good start. Key information is given on how to visually examine gloves, how to avoid moves that might lead to glovesleeve damage, and safety related to glovesleeves. While this is a good starting point for a general “how to” training, it cannot replace understanding the specific equipment operations and procedures.
As noted, PLC control is used to incorporate most of the SOPs in the isolator program by the manufacturer and the user. This can further reduce training and operator setup responsibilities. Many programs include a safe setup or alarm for any failure. For example, if the isolator fails the pressure integrity test, the operator cannot use the equipment until it passes. The PLC simply locks out the operator. In the case of a leaky glovesleeve, the isolator will have a screen for pressure testing the gloveport and sleeve with the tester. Otherwise, an operator might use the isolator in an unsafe condition and risk exposure. This is common with older isolators that used manual operator setup. The operator could use the isolator without realizing a hole or tear exists on the glovesleeve.
To maximize the safety of the operator and facility, training, testing, history, and good isolator design features must be incorporated into a high-level containment system. Glovesleeves are fairly robust in most isolators and have been used for years by both the nuclear and pharmaceutical industries to successfully contain product. The pharmaceutical industry has a greater challenge in preventing egress of its products from the facilities. Gloves should be tested daily during production runs, along with visual examination to determine viability. Isolators should never be used if a leak is found as the risk is too great. PLCs should be used for any low OEL active, and a program should be established to minimize SOPs dealing with isolator pressure integrity testing and with glovesleeve/gloveport testing. This is the safest method and provides the greatest cost savings over time compared to manual testing with gauges and SOPs. The activity in the isolator, not necessarily the length of time on the isolator, will dictate how long the gloves remain on the gloveports. The other factor mentioned regarding chemical resistance should mandate that the material for the glove is compatible. Some chemicals will actually dissolve the glovesleeve. This failure could be catastrophic if an operator had their hands in the glovesleeves at the time. There is information available for news users from professional societies and technical forums to aid in determining wear and care of gloves.
Russell E. Krainiak is currently director of technology for Integrated Containment Systems, a design and build company of isolation and containment systems (www.integratedcontainmentsystems.com). He can be reached at firstname.lastname@example.org.
- M. Cournoyer, C. Lawton, Los Alamos National Laboratory, “Why Good Gloves Go Bad,” pres. American Glovebox Society Forum, 2006 AGS Annual Conference.