This section was written by Senior Editor Michael Valenti



Fluid Power and Fluid Handling

Technology Focus part 2

The Fine Art of Humidity Control
The Carnegie Museum of Art in Pittsburgh uses its Gallery 12 to display traveling exhibitions, which require strict relative humidity conditions year-round. During recent winters, on cold days, condensation has dripped from Gallery 12's skylights, and icicles have formed outside the building. The museum's administration commissioned Pittsburgh neighbor Burt Hill Kosar Rittelmann Associates to design a system that protects the gallery and its art by keeping humidity stable throughout the year. It was also important that the new system not disturb the layout of Gallery 12, which was designed by the eminent architect Edward Larabee Barnes in the early 1970s.

Can you spot the humidity control system in Gallery 12 of Pittsburgh's Carnegie Museum of Art? The system works behind the scenes to preserve the integrity of contemporary artworks.

In the winter and spring of 1998, Burt Hill's architects prepared a preliminary study by surveying the insulation and air/vapor barrier of the walls and skylight, analyzing the airflow path through the gallery, the wall plenum, and skylight attic, and studying air pressures in the gallery. After receiving a green light from the museum's administrators, Burt Hill composed the actual design from summer 1998 to early 1999, and construction began in February 1999. Work was completed last July.

In order to rehabilitate Gallery 12, Burt Hill reinsulated the gallery walls with a continuous air/vapor barrier composed of three inches of poly-urethane cellulose called URE-K made by International Cellulose Corp. of Houston. The company added one inch of cellulose fireproofing made by W.R. Grace & Co. and reglazed the skylights with insulating and shading glass made by Fisher Skylights of New York. The skylights got a retractable shading system fabricated by Solar Veil of New York, a company that has provided similar shading systems in many other museums.

Burt Hill designed a ducted air return system in the interstitial space behind the gallery walls, as well as an air heating system in the gallery attic that is activated on very cold days when there is a risk of condensation. Finally, Gallery 12 was equipped with its own dedicated air-handling unit to combine heating, cooling, humidification, and dehumidification functions.

The new gallery was used for the first time this winter as the site of the Carnegie International, an important survey of contemporary art from around the world.

Extending the Shelf Life of Juice
The shelf life expectancy of juices packaged in PET bottles is getting longer. The U.S. food and beverage division of Graham Packaging Co. L.P. in York, Pa., is a leading supplier of plastic containers to the juice industry, and has begun to apply gas barrier coatings to polyethylene terephthalate containers.

Although it's invisible, the Bairocade coating on these juice bottles will lengthen their shelf life.

The coating, called Bairocade, is an epoxy-amine developed by PPG Industries Inc. of Pittsburgh to protect the contents of PET bottles from reacting with oxygen in the air. Bairocade-coated PET bottles have up to three times the shelf life of uncoated bottles.

The 8- to 20-ounce PET bottles blow molded at Graham Packaging's York facility are carried by chucks into a steel spraying booth. The chucks impart an electrical charge to attract droplets of Bairocade sprayed from oppositely charged guns. The sprayed bottles are sent to infrared ovens to cure the coating. Bairocade imparts a glossy finish that improves the typically hazy appearance of PET bottles, and resists scuffing.

In addition, chemists at PPG formulated the Bairocade coating to meet the specifications of PET's resin identification code so that PET bottles coated with clear or colored versions of the material can be recycled without modification.
Hybrid Manifold Simplifies Blowdown
Many industrial processors measure flow rate in their lines by bleeding off a portion of the process fluid through impulse lines connected to a manifold that is connected, in turn, to a differential pressure transmitter. The latter instrument measures the pressure differential of the fluid, which reflects flow rate. It is important that the impulse lines be periodically purged, or blown down, in order to remove any fluid that can compromise the pressure transmitter's accuracy. Hex Valve of Cincinnati designed its HM56 five-valve instrument manifold to simplify and speed up impulse line blowdown.

The HM56 instrument manifold combines a three-valve manifold design with two independent blowdown valves to replace a host of piping, tubing, and nipples typically used to blow down impulse lines.

The HM56 manifold combines a traditional three-valve manifold with two independent blowdown valves. When the operator blows down the impulse lines, the block valves on the manifold are closed, and the two separate blowdown valves are open. This allows the impulse lines to be cleaned out through the ports in the blowdown valves.

The new manifold functions as a single, compact assembly in place of the eight nipples, four tees, and two shutoff valves that would be required for a conventional blowdown valve installation. The manifold is equipped with a single flange that enables the unit to be mounted directly to the pressure transmitter, eliminating more piping, tubing, and nipples. This flange has an outlet flange-face protrusion designed to mate with the transmitter's inlet cavity, thereby providing an internal barrier to minimize fugitive emissions. Backseated bonnets enhance emissions control and also prevent the manifold stem from being removed or blown out.
Yogurt Mixing Made Easy
 Yogurt processors have their hands full adding the proper amount of fruit to their products. The common practice is to mix the fruit and yogurt well upstream of the filling hopper, which contains the portion of mixture that is pumped into the cups. This entails using a different hopper for each flavor, and does not guarantee a precise dosing of fruit into each cup. Another drawback to upstream mixing is that it incurs considerable losses of fruit from purging the line when a production run is changed. Now, PCM Dosys of Rambouillet, France, aims to eliminate these problems with a just-in-time method of injecting and mixing fruit immediately before the filling hopper.

The Dosyfruit pumps simplify yogurt making by injecting the specified amount of fruit for each cup.

The fruit-mixing system, called Dosyfruit, consists of a series of pumps, each designed to deliver fruit pieces up to one inch across into the same pipe that sends plain yogurt into the filling hopper. Every Dosyfruit pump is equipped with automated control valves synchronized with the intake of the dosing pump that fills the yogurt cups from the hopper. The Dosyfruit pumps inject fruit pieces simultaneously with the plain yogurt, just prior to the filling of the yogurt cups. Operators adjust the valves to deliver the requisite amount of fruit, and the quick mixing just prior to delivery guarantees the thorough mixing of yogurt and fruit.

This system eliminates the need for separate hoppers for different flavors and adding fruit to the hopper separately, and minimizes losses of fruit. Among Dosyfruit installations are Danone in France, Poland, Russia, and Spain, and Yoplait in Australia, Mexico, and New Zealand.
Cooling From the Top
 Factories, warehouses, and distribution centers are among the large structures that use an evaporative roof cooling system to lighten the load on air conditioning equipment.

The Sprinkool system creates a mist that removes heat from roofs, helping air conditioners work more efficiently by cooling building interiors.

According to the developer and marketer, Delta T Corp. of Lexington, Ky., the system, called Sprinkool, can reduce roof temperatures by 70°F on hot summer days. Cooling the roof can lower floor temperatures by as much as 10°F, to lift some of the burden from air conditioning systems.

Delta T engineers typically divide a client's roof into 5,000-square-foot zones before installing a series of pipes and sprinklers that will generate a water mist. They also attach their own thermistor-type temperature sensors on the roof. These instruments send data to a Pentium chip computer that calculates the precise amount of mist needed to cool each roof section.

Each ounce of water that evaporates completely removes 31 Btu of thermal energy. Evaporating 1.5 gallons of water will remove nearly 12,000 Btu of heat from the roof, which is equivalent to one ton of air conditioning.

Each sprinkler head is equipped with molded polymer filters to prevent minerals in the water from clogging the orifice. Delta T also replaces the copper pipes of previous generations of sprinklers with lightweight plastic and uses oversized acrylonitrile/butadiene/styrene pipe supports to let the pipes expand without placing stress on the roof. When weather turns cold, compressors inject air at 40 to 50 psi to purge the pipes of water before it can freeze.

Webcraft Inc. of Salisbury, Md., uses a Sprinkool roof cooling system to lower temperatures in its 60,000-square-foot printing plant. "Because we are a web printer, our machines are equipped with ovens that generate heat during operation, 24 hours per day, seven days per week, for about 360 days per year," explained plant engineer John Atkins. Webcraft was able to eliminate 50 tons of air conditioning equipment by using a Sprinkool system to augment the Salisbury plant's air conditioning equipment, which weighs a total of 150 tons. "Installing the Sprinkool system reduced our capital and operating costs," noted Atkins.

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