Ventilation Sleeve

The Rheo Ventilation Sleeve provides 360 degrees of dust extraction. This design ensures that there is air-flow around the full perimeter of the dust zone so that regardless of obstructions in the air flow such as an operator’s hand or a drum liner or a discharge chute, there are no “stagnant” air zones that allow air-borne dust to drift into the operator’s breathing zone.

The Rheo Ventilation Sleeve provides localized dust extraction. This relies on creating air-currents that will pull dust away directly from the source, rather than just creating a barrier between the dust zone and the operator. Very few drum cones, or stainless shroud designs provide a complete, leak-proof enclosure and fugitive dust is often released in an unpredictable manner. This results in compromising containment. Even if there is a perfect seal with a rigid enclosure design, often that enclosure has to be removed from the product container (eg, the drum cone must be pulled off of the drum at some point when switching to the next drum). Without localized extraction, there is no effective means of preventing residual powder from falling off of the product contact surfaces and ending up on several surfaces of the surrounding floor, equipment, etc. This shrouding, drum cone, valves, etc. also significantly increases the product contact surface area that must be cleaned.

Surrogate testing has demonstrated that by implementing the Rheo Ventilation Sleeve in a process that is being performed in a down-flow booth operator exposure levels can be significantly reduced. The localized dust extraction of the Ventilation Sleeve eliminates a vast amount of the dust before it even gets into the main air stream of the down-flow booth. This reduces the dust that may be drug across other equipment in the suite. This also directs the largest volume of dust into one dedicated filter rather than contaminating all of the filters of the down-flow booth.

The Rheo Ventilation Sleeve has a removable cover that provides wipe down access to all surfaces of the sleeve. Typically the Ventilation Sleeve is wiped down with a moist towel after use and then removed from the application and taken to a parts washing area. For higher containment, the sleeve should be wiped down and then removed and placed into a disposable bag such as a drum liner. This provides a more contained means of transporting to the parts cleaning area.

There multiple components that prevent the loss of product through the Ventilation Sleeve slots.

• The primary reason that this is prevented is that the basic slot design and the nature of the utility requirements are such that the static pressure at the slots is quite low, but the volumetric flow rate is quite high. This has the opposite effect of a vacuum cleaner, in that it is creating air currents around the perimeter of the sleeve that draws in air-borne dust, but it does not have high pressure suction such that it is vacuuming heavier solids out of the product stream. This obviously depends on material characteristics of the powder being transferred and should this become an issue there are two possible remedies. 1. The duct connection can be fitted with a damper control to control the flow rate at the sleeve and 2. a tapered product shield can be added to the design to divert any product flow away from the slots.
• Another major component to this design is the basic procedure that is followed in using the Ventilation Sleeve. Often this sleeve is used for applications where products are being transferred from drums (with liners) or from bags or from discharge chutes (rigid or flexible). Part of the procedure requires that the drum liner, bag, or chute be used to channel the discharge below the extraction slots. Typically the operator chokes off the drum liner neck until it is positioned below the extraction slots, this prevents product from being pulled into the slots and it provides for the best containment. A video of this procedure is available.
• Verification: Some simple testing has been performed to evaluate product loss through a Ventilation Sleeve. One such field test was performed by dumping 49.8kg of product through the Ventilation Sleeve and the exhaust air was passed through an in-line filter. The total product collected in the in-line filter amounted to a total of 0.052kg which calculates to be a little above 0.1% product loss. This testing is very product-specific and Rheo offers product testing in our testing facility in Peoria, IL if desired.

The basic premise behind the Rheo Ventilation Sleeve is extracting air at a high enough flow rate that any fugitive dust will be caught into currents of air and extracted into the dust collection system. Each Ventilation Sleeve is designed such that these air-currents create a slightly negative pressure within the dust zone so that a loose fitting sleeve will not leak dust. This allows for simpler design specifications and easier insertion and positioning of the Ventilation Sleeve.

The basic design of the Ventilation Sleeve does not provide uniform face velocities around the perimeter of the sleeve. The slots located near the dust collection port typically have a face velocity measurement of approximately 2600 fpm and the slots directly opposite typically have about 60% of that number. While this creates an eccentric velocity profile within the sleeve area, it does not reduce the efficacy of the containment.

Since the development of the core design, the Rheo Ventilation Sleeve has been installed and widely accepted within multiple plants of nearly every major pharmaceutical manufacturer world-wide. A list of references can be provided upon request.

If product is being poured from a drum without a drum liner, there are two options that can be considered. The first would be to use a disposable product chute that is pulled over the outside of the drum and either taped or band-clamped in place. This chute would then function similar to a drum liner. Another option would be to use the tapered product shield option and then simply pour the product using a chute or tapered spout. The tapered product shield deflects the product away from the slots to prevent any product from being channeled into the flow chamber.

The flow chamber is the internal channel where the air-flows away from the slots and towards the dust collection port. For GMP clean-ability requirements, this channel is often considered the same as exhaust duct where it is only contacted by “rejected” dust. Any dust in this chamber will be pulled into the dust collection system and will not re-enter the product contact area. This consideration allows for less costly internal surface finish requirements.