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Expansion Tanks

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Modern tanks are called diaphragm expansion tanks and are attached and hang down from the boiler piping on the supply side of the system. Older models were larger, horizontal and connected from above the system. Read More…

Expansion Tanks Expansion tanks are small vessels containing pressurized air that are components of closed water heating systems for both residential and commercial buildings.
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Leading Manufacturers

Oak Lawn, IL  |  800-282-1574

If you are looking for innovative pressure vessels, you’ve come to the right place! We actively manage your project every step of the way. We keep you informed of what we are doing to ensure we keep up to your standards and delivery times.

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Midwest Imperial Steel Fabricators, LLC $$$

Gladwin, MI  |  989-426-4768

Gladwin Tank Manufacturing specializes in custom designed and built ASME tanks and ASME jacketed weldments of any shape or size made from carbon steel, stainless, duplex and nickel alloys.

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Gladwin Tank Mfg., Inc. $$$

West Alexandria, OH  |  937-307-3597

Rexarc is the global leader in acetylene gas plant production, and is trusted in over 50 countries around the world with the generation, purification, and compression of the highly volatile gas. We have the knowledge, attitude, equipment, and processes to support your needs in the vessel production. We also offer value added services of piping, instrumentation, paint, and other controls integration.

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Rexarc International $$$

Savannah, GA  |  912-233-8902

We serve the chemical processing, pulp & paper, pharmaceutical, food, and coatings industries with high quality, on-time delivery and competitive pricing. Our pressure vessels meet today’s demanding market, fabricated to ASME tank standards. We offer carbon, stainless, alloy 20, monel, inconel, hastelloy and 904L; thicknesses up to 1” and pressures up to 1000 PSIG; non-destructive testing options.

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Savannah Tank and Equipment Corporation $$$

Sharpsville, PA  |  800-645-1248

Sharpsville Container manufactures a variety of pressure vessels, stainless steel tanks, poly tanks, chemical storage tanks, and other containment vessels for a diverse customer base. Our vessels serve a variety of industries including pharmaceutical, food, beverage, high-purity and intermediate chemicals.

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Sharpsville Container $$$

Seattle, WA  |  888-623-8626

Essential Innovations is a research and development company manufacturing and supplying unique products to the commercial and industrial industries in areas of liquids, powders, and solids processing. We have several patents for our development in vacuum fluid transfer and filtration technology which we have used to further develop specialized equipment for liquid degassing and residual solvent removal for high-grade products.

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Essential Innovations $$$
placeholder image Midwest Imperial Steel Fabricators, LLC Gladwin Tank Mfg., Inc. Rexarc International Savannah Tank and Equipment Corporation Sharpsville Container Essential Innovations

Expansion tanks are easy to maintain, and if they are pre-charged, these tanks are literally maintenance free. All repairs should be done by a certified plumber. These pressure tanks ensure constant pressure within the piping system, and act as a safety device. Without them, the boiler may explode, the pipes could burst and overflowing is a major concern.

They are typically composed of a stainless steel tank, blue or green exterior paint and a rubber spacer called a diaphragm located on the inside of the tank. This diaphragm provides an air-tight seal and divides the tank in half-the bottom is pressurized air, while the top is left open for excess water from the boiler.

Plasite Lined Tank Expansion Tanks - Gladwin Tank Mfg., Inc.

Since they occasionally hold drinking water, expansion tanks, like boilers or other food processing tanks and water pressure tanks, must be sanitary, non-contaminating and conform to health standards. The interior walls of the tanks need to be smooth and groove free. Besides domestic and commercial closed heating systems, most vehicles contain smaller expansion tanks for their heating systems.

The purpose of expansion tanks is to absorb excess water pressure in a closed water heating system. Any water heated in a closed space will expand. Therefore, heating systems need additional space for the increased water volume when it is at a high temperature. The excess water enters the expansion tank, which is filled halfway with pressurized air at 12 psi and divided by a rubber diaphragm spacer.

While the water volume is up, the extra water fills the tank. The top half of the tank is directly connected with the heating system, and when the temperature decreases, the pressurized air on the bottom half of the expansion tank pushes the water back into the boiler system. This ensures there will be no pipe damage because of too much pressure.

Water heating systems without expansion tanks risk the internal boiler pressure increasing beyond the release setting of the pressure release valve (PRV). When the PRV opens, the water leaves the system and creates pressure that is too low. Expansion tanks are always properly charged with air, which shouldn't exceed 12 psi, or the water will boil and this consistency is a major benefit to using expansion tanks.

Expansion Tanks Informational Video