Fluid Power and Fluid Handling

Technology Focus part 2
This section was written by Associate Editor Michael Valenti
Detecting Airport Fuel Leaks Improving the measurement of underground fuel leaks at airports was the aim of Vista Research Inc. in Mountain View, Calif., when it designed its leak detection system.

The HT-100 detects aviation fuel leaks that are as small as 0.004 percent via volumetric changes at Montreal's Dorval airport.

Many airports have pressure test systems to watch for fuel leaks, but the systems can be inaccurate because they do not account for changes in fuel volume caused by temperature variations. There are other methods, but they have disadvantages of their own. For instance, a system using fuel additives that can be detected by buried fuel sensors is expensive; tracer wires installed alongside pipelines in trenches require replacement in three years. These tests can also be affected by soil conditions.

The Vista system measures the volume changes that occur at operating pressure, as well as the volume changes when pressure is dropped to atmospheric levels. The system automatically compensates for the thermal expansion and contraction of liquid in the line, to eliminate the major source of error in pressure-based testing.

The HT-100's programmable logic controller-based system calculates the fuel's expected change in volume under the influence of outside ground and air temperatures. If the fuel volume doesn't match the anticipated changes, this indicates a leak in the system.

The Vista system is attached to the test pipeline by a flexible hose or steel pipe so fuel will flow through the unit. Testing is typically conducted late at night and takes three hours. The Vista system is equipped with a computer-controlled pump and pressure relief valve to maintain constant pressure in the line.

The Vista leak detection system has been tested at airports in Boston, Dallas, Miami, Phoenix, Portland, San Francisco, and St. Louis, where it demonstrated its ability to detect leaks as small as 0.004 percent. The managers of Dorval and Mirabel airports in Montreal have purchased two of Vista's HT-100 systems. One unit has been permanently installed at Dorval's fuel storage area, where the fueling system contains about 350,000 gallons in its pipelines. The other HT-100 is installed on a truck that is used to test the entire hydrant fuel line system at nearby Mirabel and sections of the piping at Dorval.

Enamel Beats the Heat Fashioning bathtubs is not a simple task for Crane Plumbing's steel stamping and porcelain enameling plant in Dallas, when summertime temperatures reach 110° F. The heat affects the compounds that are used to draw enamel paste from a press onto the steel tub and interferes with the cleaning compounds used to remove grease and other materials from the steel so the porcelain will adhere. The ups and downs of the Texas heat forced operators to constantly vary their pressing operations by adjusting holding pressure or adding water to the enamel paste. Even then there were a high number of flawed products that required reworking or were rejected outright.

Oakite compounds draw enamel in the Texas heas for Crane Plumbing's bathtubs.

Crane evaluated a variety of materials before selecting the Draw Clean 36P and GardoClean SMD drawing compounds made by Oakite Products Inc. of Berkeley Heights, N.J., to cure its summertime troubles, and began using them in the past two years. Draw Clean is a reformulated version of Oakite's fat- and soap-based Die Gard 36 drawing compound. Adding Draw Clean 36 to its press provided Oakite with a consistent drawing lubricant quality in each batch of enamel paste to produce surfaces without constant readjustments.

GardoClean SMD is a high-alkaline cleaner that Oakite uses to remove the Draw Clean 36P and other grease and soils from its press. This compound contains a natural defoamant to control the foam that the spray washer raises in cleaning the press. Indeed, Oakite partnered with Crane to make the porcelain company's six-stage power spray wash more efficient. Among other things, the pro-cess uses a diluted form of Gardo- Clean solution with hot water to remove soil instead of a full-strength version of the cleaner, and so cuts down on Crane's overall use of chemicals. Oakite also eliminated an acid cleaner prior to alkaline cleansing, because one neutralized the other.

Protecting Seaborne Electricals
The humidity of the open sea is an ever-present threat to the electrical equipment onboard ships, an opportunity seized by the engineers of A.C.C.I. in Tregunc, France, who designed the Aela marine dehumidifier. This device has been installed by Sedam in Brittany on fishing boats operating from the Port de Concarneau, a major French fishing port; by EBS, an electronics company based in Loctudy, France, on fishing boats and rescue vessels; and also by Labbé, a shipping concern in St.-Malo, on ferries plying the Channel Islands.

The Aela dehumidifier keeps moisture damage away from the electrical systems of French fishing boats, like these based in Marseilles.

The Aela dehumidifier consists of a base plate that is mounted to the deck and supports the unit's drain pan, coils, fan motor, and a ventilation network that includes one inlet and three outlet ducts. Each duct is connected to a condensate drainage pipe designed to prevent overflow, even on a vessel that maintains a constant list over a long period of time. The Aela's fan circulates humid air around the coils to ensure efficient heat transfer before the cooled and dehumidified air is distributed through the outlet ducts.

The dehumidifier's compressor is equipped with an external heat protection system, a silencer, and both internal and external anti-vibration mounts to make it operate as unobtrusively as possible. An RAL9010 enamel-coated aluminum body protects the Aela from the corrosive effects of salt air.

The Aela can treat up to 26 pounds of air in 24 hours with an intake air temperature of 68°F at 65 percent relative humidity. The device operates on 110 volts or 220 volts ac at either 50 or 60 hertz, or on 12 volts or 24 volts dc. A battery option enables ship crews to use the Aela as a portable unit.

A Hog for Dust United Air Specialists of Cincinnati has introduced the Dust Hog Supra-Blast, a centralized cartridge dust collection system designed for easy maintenance. The maker recommends it for applications that include welding, grinding, sanding, laser cutting, and powder coating. For example, The Metalworking Group, located in Cincinnati, uses the device in its grinding operations.

A Dust Hog Supra-Blast removes dust from several metal-grinding stations simultaneously.

At the heart of the Supra-Blast dust collector is a tubular air distribution insert built into the cartridge filter. As compressed air is released from the pulse valve, the conical tip of the insert diffuses the blast along the entire length of the filter, to remove as much dust as possible from the filter when it is cleaned. The Supra-Blast removes dust along the entire length of each filter.

In addition, the new filters offer 310 square feet of media, which is 22 percent more filter area than the industry standard, according to the manufacturer.

Designers provided the Supra-Blast with a lever-operated, push-to-seal closure with a quick-release mechanism that enables operators to change filters in a fraction of the time required by standard, turn-knob doors. UAS engineers added a hinged rear access door that enables maintenance personnel to inspect the pulse valves in the clean air plenum without entering the unit. An added benefit of the access door is that it allowed the filter's designers to situate both the compressed air manifold and pulse valve in the clean air chamber, shielding them from the weather and harsh work environments, thereby improving performance and reliability.

Measuring the Breath of Life
DHD Healthcare in Canastota, N.Y., designed the TheraPEP breathing gauge to improve respiratory patients' breathing by means of positive expiratory pressure (PEP) therapy. Persons afflicted with chronic obstructive pulmonary diseases, such as cystic fibrosis and emphysema, are typically introduced to TheraPEP during a hospital stay and then bring it home with them. Users blow into the TheraPEP, which is equipped with a plastic indicator that shows if they are exhaling with sufficient pressure to clear away secretions and open the airways in their respiratory systems. They use the measuring device to adjust their breathing to provide the requisite pressure.

The TheraPEP gauge contains a diaphragm, designed to be sensitive to the very low pressure of human breathing, to ensure respiratory patients are using the proper force in expiratory therapy.

Because the TheraPEP must respond to the very low pressures of human breathing (between 10 and 20 centimeters of water), the device's diaphragm had to be extremely sensitive and needed to meet tight tolerances to provide repeatability. An all-rubber silicone diaphragm from RPP Corp. in Lawrence, Mass., was chosen because it provided these characteristics and it could be molded with exceptionally thin walls.

An added benefit of the silicone diaphragm is that it can be easily cleaned with vinegar and mild soap, unlike the steel aneroid gauges that the TheraPEP replaces. The metal gauges are more expensive and more easily broken than the plastic TheraPEP. The TheraPEP reportedly is sold to hospitals and home care companies in 36 countries, including the United States and Japan.



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