Many small communities with limited financial resources find it difficult to meet U.S. Environmental Protection Agency standards for drinking water. The solution for a number of small municipalities is to work directly with manufacturers such as Osmonics Inc. in Minnetonka, Minn., which can design complete, competitively bid water-treatment systems for as little as half the cost of those by third-party consulting engineering firms.

This combination ozonation/reverse-osmosis system is designed to remove the organics and dissolved solids from small-town drinking water

In fact, the economy of the Osmonics sole-source equipment offering has led the company to market its systems among North American towns with populations ranging from 200 to 2,000.

Froid, Mont. (population 182), takes its drinking water from a shallow well. The water is deeply colored with lignins and tannins, and it has high levels of total dissolved solids including iron and manganese. The high levels of chlorine that is needed to treat the well water conventionally would yield unacceptable levels of trihalomethanes.

Osmonics engineered and supplied a reverse-osmosis system that was integrated with an ozonation system. Froid's well water is first treated with ozone to break down the organics and oxidize the dissolved iron and manganese, which causes the solids to precipitate for removal by a media filter. The portion removed is used as pretreat water.

Treated water is then sent to the Osmonics reverse-osmosis equipment, consisting of an array of five membrane element housings. The housings are loaded with spiral-wound membranes measuring 8 inches in diameter and 40 inches long. These membranes are formulated to reject the ions that comprise the total dissolved solids, reducing their presence to the point where the water can be blended with pretreat water from the media filter and still meet water-quality standards. This reduces the cost of subjecting the town's water to reverse-osmosis treatment.

The Variseals are made of Turcon compounds, a proprietary material that combines polytetrafluoroethylene resin with a variety of fillers--including graphite, carbon, glass fibers, and polyamides--to produce such performance properties as wear resistance, extrusion resistance, and lubricity. The seals are machined to form a U-shaped jacket with a cross section customized for each application. A corrosion-resistant stainless-steel spring energizer is inserted into the jacket to provide permanent resilience.

During operation, fluid pressure and spring load create a positive seal with minimal friction. In addition, a backup ring may be located between the seal and gland to prevent extrusion.

In the McDonnell Douglas application, the Variseal was used on hundreds of hydraulic cylinders that were mounted between the airframe and a steel scaffolding surrounding it.

All Series HF models have dual scales that also show metric equivalents (liters per minute). Wetted parts include brass, Teflon-coated Alnico 304 stainless steel, and Buna-N, materials specially selected for superior compatibility.

Dwyer's flow monitors employ a patented design based on a combination of sharp-edged orifice disk and a variable-area flowmeter that yields accuracy of ±2.5 percent of full scale over the center one-third of the scale and ±1-percent full-scale repeatability. All internal wetted parts are contained inside a sealed brass tubular casing so they are maintenance-free.

The flowing media cause linear motion of a spring-loaded orifice disk and ring-shape transfer magnet, both riding on a tapered center shaft. The transfer magnet drives a clearly visible follower outside the flow tube.

One of the costs associated with maintaining a landfill is treating the leachate produced by rainwater that percolates through garbage. This typically means piping the liquid wastes from the landfill to a storage tank or impoundment before shipping it to a separate treatment plant. Fluids Controls Inc. in Huntsville, Ala., designed a recirculation system that greatly reduces leachate-management costs by spraying leachate back into the landfill, thereby using the garbage mass itself as a storage/treatment system.

This valve box is made of high-density polyethylene to handle corrosive leachate that is recirculated to the landfill or sent on to storage tanks

The Fluids Controls system uses existing landfill equipment, such as the sump pump in the landfill's slope riser. The pump sends leachate through the company's own Fluid-Lok dual-containment high-density-polyethylene (HDPE) pipingÑwhich safeguards against leaksÑinto an HDPE manhole used as a valve box. This manhole contains a flowmeter that measures the amount of leachate removed from the landfill as well as valves that direct the leachate into the landfill for recirculation, to holding tanks, or to the treatment plant. Transparent plastic ports in the manhole top enable operators to read the meter and check the position of the valves without opening the manhole.

Covel Gardens Recycling & Disposal Facility in San Antonio, Tex., installed Fluid Controls' recirculation systems last fall, reducing the operating costs of leachate handling by at least 90 percent, according to the landfill representatives.

Composite materials based on polyetheretherketone (PEEK), such as Xytrex 451, were originally developed for aerospace and defense applications. EGC's material is made of PEEK resin and chopped carbon fiber that imparts a tensile strength of 17,000 pounds per square inch and temperature resistance up to approximately 350 degrees F in continuous service.

Components made of Xytrex 451 do not gall or seize when in contact with metal mating surfaces. They also exhibit low-wear and low-friction characteristics, provide longer life by extending meantime between failures, and incur significantly lower maintenance costs than conventional metal rings.

Caltex Corp. in Dallas chose Xytrex 451 case rings for the 257 process pumps, plus spares for 43 pumps, in its Mapta Phut, Thailand, refinery. To design the case rings so they could be installed in the pumps without any further machining, EGC engineers used tighter tolerances than recommended by pump manuals. The case rings exceeded Caltex's expectations, according to EGC.

Despite the fact that torque tightens flange bolts upon installation, the British Petroleum Chemicals (BP) specialty chemical-processing plant in Hull, England, experienced leaks caused by thermal cycling from production shutdowns. These leaks cost the company $22,500 to seal during 1994-95.

BP approached Rotabolt to solve the problem. Rotabolt engineers determined the load that would be required to provide a tight seal at each flange, and modified a total of 900 load-monitored fasteners that were then fitted to all flanges in the Hull plant. The tension of the bolts can be guaranteed to within 5-percent accuracy, compared with 30-percent accuracy provided by a torque wrench. In addition, the tension can be quickly inspected by a maintenance worker, who only has to check the rotor cap to ascertain that the fastener is at the prescribed limit and that correct tension is being maintained.

Since the bolts were installed at the Hull plant in September 1995, there has not been a single joint leak, despite plant shutdowns. BP is working with Rotabolt to reduce fugitive emissions by 50 percent from 1990 levels at its main processing sites in the United Kingdom, Europe, and the United States.

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