How to Predict Contained Dust Collection System Performance

Surrogate testing offers a way to provide meaningful performance information prior to installation

By David Steil, pharmaceutical market manager, Camfil AIr Pollution Control

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The proper selection and operation of contained dust collection equipment is critical to the operations in pharmaceutical plants for a host of reasons, from environmental requirements and employee health and safety, to production cleanliness and efficiency. Historically, no performance data has existed on contained dust collection systems until they were already installed.

Surrogate testing offers a way to provide meaningful performance information prior to installation, to help pharmaceutical manufacturers determine if the equipment will meet required specifications and standards for a specific project. It can thereby help to reduce costs while also reducing risk. 

THE ROLE OF SURROGATE TESTING
In selecting dust-collection equipment for pharmaceutical applications, it is critical to understand the potent, toxic or allergenic properties of the dust. This information helps determine the Occupational Exposure Limit (OEL), a value specific to each individual API. The OEL is defined as the amount of material determined to be the maximum air concentration, expressed as a time weighted average (TWA), to which a healthy worker can be safely exposed for an eight-hour shift, 40-hour work week. This value is typically expressed in micrograms per cubic meter of air (µg/m3).

In most cases, some level of isolation and containment is required due to the fact that the pharmaceutical dust is hazardous and cannot be released into the surrounding environment for employee health and cross-contamination concerns.

EQUIPMENT TO BE EVALUATED
The equipment selected for evaluation in this test was a cartridge-type contained system designed for high efficiency collection of dry dusts. It contained four cartridge filters rated at 99.999 percent efficiency (MERV 16) on 0.5 micron particles and larger. The supplier’s stated claim was that the equipment would perform at or below the standard threshold limit of 1.0 µg/m3 for an 8-hour TWA.

The dust collector was equipped with soft-walled, safe-change containment technology for both the filter cartridges inside the collector and the discharge system underneath. The filter cartridges utilized bag-in bag-out (BIBO) technology, with two cartridges removed per bag. The discharge system utilized continuous liner technology to contain the dust that would be released from the cartridges to the hopper below during automatic reverse pulse-cleaning.

TESTING PROTOCOL AND METHODOLOGY
To perform the testing, the dust collection equipment supplier engaged an independent laboratory accredited by the American Industrial Hygiene Association (AIHA). Together the supplier and laboratory outlined a test protocol conforming to the ISPE Good Practice Guide, “Assessing the Particulate Containment Performance of Pharmaceutical Equipment.”

To supplement the ISPE guidelines, the test protocol also incorporated AIHA Good Industrial Hygiene Practices. The methodology included the following elements: 

Surrogate compound selection: Lactose was selected as the compound that would best simulate the customer’s API without posing a hazard to the operators or the surrounding environment. The surrogate dust was 100 percent lactose, undiluted with other materials. In real-world processes, the API is incorporated in a specified concentration and mixed with other inactive substances and excipients. By the time it reaches the dust collector, the API might account for just a very small percentage of the dust being captured. By using an undiluted test dust, the collector would thereby be challenged with a “worst case scenario.”

Test room: The dust-collection equipment was located in a dedicated and decontaminated area of the equipment supplier’s factory. The test area was isolated, sealed off, pressure-washed and cleaned prior to the test. Access was tightly controlled to keep the area pristine and avoid contamination. Humidity, temperature and pressure were all tightly maintained, with an air change rate of 3-5 changes per hour prior to the test.

TEST SEQUENCE  
The test conditions mimicked workplace operations as closely as possible. Working from a charging area adjacent to the test room, an employee charged the lactose surrogate dust to the collection system on a pre-determined schedule. Two charge and discharge cycles using 12.5 kg of lactose per cycle occurred during the first simulated work-shift test day, and one additional charge of 12.5 kg also occurred on this day. This third charge of lactose was left in the dust collector until the following test day.

Test operators conducted an additional liner change operation on the following day to discharge the third charge of 12.5 kg of lactose left in the system the previous day. They performed two additional charges of 12.5 kg of lactose to the system to conduct liner discharges No. 2 and 3. The recirculating air-conditioning system in the test room was kept off so as not to skew results during the test.

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