Gel Caps Need Tight Hvac Specs

May 12, 2000
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MIAMI, FL — Tropic Air Conditioning, a 42-year-old mechanical contracting company here, discussed and conceptualized one of its latest projects over a period of 11 months before the final proposal was accepted.

When Swiss Caps USA, a global pharmaceutical company, decided to build a state-of-the-art facility here in Miami, senior project manager Siegfried Schwab teamed up with Scott Gordon, president of Tropic Air.

The manufacturing process of soft gelatin capsules is a high-tech process requiring cleanrooms. Based on FDA (Food and Drug Administration) requirements, Schwab had a strict set of parameters that needed to be adhered to.

Specs to Conquer

The facility is 50,000 sq ft in size, with special drying rooms maintained at 21% rh. Should the rh increase in the drying rooms, the drying time of the capsules slows down the entire production process, said Gordon.

Six-inch PVC ducts were installed inside the walls to supply air into the drying rooms. Mech-anical tumblers and/or trays are used to allow the capsules to dry.

Two areas in the cleanrooms require 100% exhaust air. An air-to-air enthalpy wheel was designed into the project to use the cool return air to precondition outside air entering the building. According to Gordon, the use of the enthalpy wheel alone saved 25 tons off of the design.

There are Class 100,000 cleanrooms with air pressurization requirements to maintain the cleanliness of the air. Room air pressures range from 0.05 to 0.15 in. wg. The air-distribution system was designed for laminar airflow, with return air entering drywall enclosures and grilles located 6 in. above the floors and ducted back up through the ceiling.

Custom-made, stainless steel filter banks housing 90% to 95% filters are used in the weighing rooms so that certain materials generated in the weighing and measuring process are not recirculated back into the return air.

Schwab had to visualize the entire production process and recognize any potential problems so that solutions could be integrated into the original design.

Slow and steady wins the race

Tropic Air handled the design-build process to ensure that Swiss Caps’ parameters would be met.

In order to bring the project within budget, the original proposal of a 100% chilled-water system was redesigned to take as much load off of the chillers as possible, and use air-cooled rooftop package units in non-critical areas such as offices and the warehouse.

By downsizing the chilled-water equipment, savings in piping and labor were obtained. Obviously, the cost per ton for chilled water is significantly higher than with air-cooled package units.

The design-build process was challenging due to the complexity of the project and the need to have to provide a complete proposal without having the entire design completed, said Gordon. The shell was under construction during the final negotiation of Tropic Air’s contract.

Gordon worked side-by-side with Schwab to verify that design criteria were met. Using a basic floor plan, block heat loads were performed to determine tonnage, cfm, and areas that needed to be cleanrooms.

Equipment was selected, with duct and piping designed to the point that a takeoff could be made and a bid was put together. After the proposal was approved, it was time to begin on the final design.

And That’s Final

Antonio Franyie, a PE with more than 35 years of design experience, was brought in by Tropic Air to work out the final design for the project. Due to the high latent load in the drying rooms and low relative humidity requirements, the design was challenging, said Gordon.

Gas-fired desiccant dehumidifiers were selected to handle the high latent loads found in the drying rooms. As the air in these rooms needs to be circulated through drying tumblers, a primary-secondary air system was chosen.

Air is introduced into the room from the dehumidifiers, and then high static fans pull the air up through return air grilles to distribute it down to the tumblers.

The air leaves the drying room at 21% rh, then enters a chilled-water air handler where it is used to supply the encapsulation room. The rh requirement in this room is around 50%; however, there is a significant amount of moisture produced in this room when the capsules are made.

Finally, the air is returned to the dehumidifier, where the moisture is rejected through the reactivation section. A post-cooling coil cools the air from approximately 105° to 73°F.

The air entering the drying room is very dry during the moisture-absorption process. The drybulb temperature is reduced to approximately 69°, with the return air drybulb being lower than the supply air drybulb.

More System Specifics

Tropic Air subcontracted with Duct Shop Inc., Miami, for the sheet metal installation.

“Duct Shop has been a subcontractor of ours for over 10 years and has always performed to the highest level of quality,” said Gordon.

Duct Shop’s John Jones, president, and Carlos Flores, estimator and field supervisor, handled the details of installing the more than 100,000 lb of sheet metal required for the installation.

Several areas have four layers of ductwork, all of which had to be carefully planned and worked around the other trades.

Variable-frequency drives are used on the chilled-water air handlers supplying the cleanroom area. The drives are set up to increase fan speed as the HEPA filters load up, so that one air change every 2 min is maintained.

A Johnson Controls “Facilita-tor” was installed to control and monitor the numerous pieces of hvac equipment, as well as the facility’s natural gas, water, and electricity consumption. Animat-ed color graphics software helps Swiss Caps personnel monitor the facility.

Alarms are set to notify either Swiss Caps or Tropic Air via pager at the first sign of a possible problem. It is then possible to see what the problem is by contacting the building’s control system via computer, allowing dispatch of a technician with enough information to expedite the troubleshooting process.

The chilled-water plant consists of three Dunham Bush WCFX water-cooled, rotary screw chillers. Using a proportional actuator, the level of liquid in the cooler adjusts to match load requirements. “The chillers were used due to their excellent part-load performance,” said Gordon.

At full load, the plant requires only two chillers. The third chiller was designed for back-up use, in addition to providing process cooling for special encapsulation machines and several other processes cooling heat exchangers.

High static fans and cooling coils are used to cool the encapsulation machines.

Rajendra Persuad, field supervisor for Tropic Air, worked to install more than 6,000 ft of process piping for nitrogen, compressed air, vacuum, gelatin, glycerin, and sorbital. Stainless steel piping carries the raw materials used in the production of gelatin capsules via compressed air-operated membrane pumps.

The welding of stainless piping had to be done carefully to eliminate slag inside of the pipe, said Gordon. Special flanges and clamps had to be used at each joint so that the pipes could be welded, cleaned inside, and then assembled — further proof that time, careful consideration, attention to detail, and precision can lead to success.

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