Tanks that include an internal bladder are usually smaller, and sometimes called captive air or bag tanks. There are styles that are designed to replace the expansion tank in a domestic hot water or chilled water system. Most bladder tanks are standard vertical design. On larger versions, the bladder is often replaceable through a flange, which can be either on the top or bottom of the tank depending on the application.
Periodic boiler maintenance includes a blowdown cycle to reduce scaling. Local laws usually do not allow high temperature water to be dumped into sewers, and a blowdown tank system is designed to reduce temperatures by mixing cold water with the effluent. It also enables high pressure water to flash to steam safely. Hanson Tank manufactures a range of recommended sizes based on boiler capacity.
Hanson can manufacture cylindrical buffer tanks in carbon or stainless steel for both hot and chilled water systems. Buffer or Volume tanks add extra capacity to any system that contains fluid. Their purpose is to increase the volume of water in the system to achieve optimum efficiency. The tanks are usually insulated to reduce unwanted heat transfer. Hanson Buffer tanks are normally vertical and as they are for indirect closed loop systems, are usually unlined. Without a buffer tank, rapid fluctuation of water temperature causes frequent stops and starts ("short cycling") of the equipment. A correctly sized and located thermal buffer tanks significantly improve the performance and longevity of the entire system they are installed in.
Thermal expansion and contraction of the water in a heating system is contained in a small tank installed at the highest point in the system. Hanson expansion tanks include all the necessary FNPT openings to install valves, gauges and controls, and are available galvanized or plain. Industry standard sizes are from 15 to 400 U.S. gallons.
Water that contains particulates can be purified by passing it through tank containing a filter medium. Depending on the nature of the contaminants and the eventual purpose of the filtered water, filter media can be sand, activated carbon, nthracite, or combinations of special materials. The incoming water flow is distributed evenly through the filter medium by a diffuser, and there is usually a back flow function designed into the system to flush out the contaminants periodically. Hanson Tank has manufactured both the basic vessels and complete systems, although the filter medium is usually supplied and installed by others.
HOT WATER STORAGE TANKS:
Hotels, apartment buildings, hospitals and other facilities that need constant supplies of hot water usually have a storage tank that has been sized to meet peak demands, even though the usage at these times exceeds the output of the heater. This is achieved by selecting a tank of sufficient size, with adequate insulation, and designed to prevent incoming cold water from mixing with the hot water supply. These tanks are normally lined to prevent rusting, and the standard design working pressure is 125 psi, which exceeds typical city water main pressure.
Hanson Tanks offers a full range of standard and custom water storage tanks, and has several of the most popular sizes in stock for immediate shipment.
Any vessel that contains both water and air under pressure can be called a hydropneumatic tank. The two most common applications are in well water systems, or as buffer tanks to absorb water hammer shocks in large capacity pumping systems. In both cases, the captive compressed air acts as a cushion which can exert or absorb pressure as required.
Large hydropneumatic tanks are usually horizontal and 2000 gallons or more. Hanson Tank has manufactured hydropneumatic tanks up to 30,000 gallon capacity. The size is determined by the needs of the system, and is approximately the drawdown gallons times four. A small air compressor can be included to replenish the air volume periodically as it is absorbed into the water. Sensors monitor the water level and pressure and automatically control compressor operation as required. These vessels are usually lined to prevent corrosion and have a design working pressure of 125# ASME. Hanson Tank can manufacture the basic tank or supply all the components for a complete system ready to install.
Tanks that include an internal bladder are usually smaller, and sometimes called captive air or bag tanks. There are styles that are designed to replace the expansion tank in a domestic hot water system. All bladder tanks are usually a standard vertical design. On larger versions, the bladder is often replaceable through a flange, which can be either on the top or bottom of the tank depending on the application.
Vertical hydropneumatic tanks can also have a diaphragm which can be fixed or floating. This virtually eliminates the absorption of the air into the water over time and makes the compressor unnecessary. These are built to order only.
Here is a list of the most popular tank linings, with their characteristics.
Service life is impossible to predict, as there are dozens of factors involved,
especially the temperature and Ph level of the water. However, as all Hanson
lined water tanks are equipped with an access opening, regular inspection
of the lining is easy.
Epoxy: Sprayed on to a sand blasted surface, epoxy
linings have a durable,
glossy surface. Typically lower in cost than other linings, they offer
excellent durability during shipping and handling but can deteriorate if
water temperatures of 180oF or more are encountered.
Glass: More correctly called "porcelain enamel", glass lining is sprayed onto
a sand blasted surface, and then fired at 1500 f to fuse it to the tank
interior. Although the surface is smooth and continuous, minor imperfections
are normal, and protected by the installation of anodes. These deteriorate
first, and must be checked periodically and replaced when necessary. The
glass lining can be damaged during shipment, and the tank must be skidded
Cement: The tank interior is coated with a special blend of Portland cement to
a thickness of .75", over a welded wire mesh. The
lining must be kept moist up to the time the vessel is put into service
to prevent cracking. Careful handling of the tank is also necessary to
avoid damage . If periodic inspections reveal damage or erosion of the
lining during service, field repairs can be carried out.
Galvanizing: After preparation, the tank is submerged in molten zinc, which coats
both the inside and outside with a thin layer. Due to the size limits of
the vats available, galvanizing is more common on smaller tanks, and although
an option, is rarely used on large hot water storage tanks. However, it
is frequently specified on smaller vessels such as expansion tanks.
The majority of hot water storage tanks are insulated to save energy. This
can be done very cost effectively at the factory. These are the most popular
Polyurethane Foam: The standard system is a two component sprayed coating that expands and
hardens to about two inches thick, for about an R16 insulation value. When
cured, it is coated with 25 mils of semi- rigid white acrylic weatherproof
coating. Any minor damage during shipment can easily be repaired in the
We can install most commercially available insulation types, some of which are clad with metal jackets.
Aluminum Jacket Insulation: Semi-rigid Fiberglass with Aluminum Jacket insulation medium is purpose
- manufactured semi-rigid premium quality fiberglass wrap with Kraft paper
lining and flexible foil vapor barrier. The fiberglass
filaments are laminated parallel to the facings for enhanced flexibility and
After installation, the insulation is clad with an aluminum jacket to ASTM B-209 with a laminated 1 mil polyethylene moisture barrier on the tank side. Standard exterior jacket finish is embossed "stucco" pattern to minimize glare and resist minor damage. All tank connections are recessed and the ASME nameplate exposed. All seams are caulked with aluminum pigmented silicone for weather protection.