Fluid handling – Hydrant type – Protection against freezing
Reexamination Certificate
2001-04-10
2003-05-13
Walton, George L. (Department: 3753)
Fluid handling
Hydrant type
Protection against freezing
C137S302000, C137S550000
Reexamination Certificate
active
06561214
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
The present invention generally relates to hydrants, but more specifically to the draining of fire hydrants after use. The most common type of fire hydrant manufactured today is the “dry” barrel fire hydrant. The dry barrel hydrant gets its name from the fact that water is pumped or drained from the hydrant barrel when the hydrant is not in use to prevent corrosion of the interior and freezing of the hydrant in winter weather. Water flow into and out of the hydrant barrel is controlled through the manipulation of a main valve located in the base of the hydrant. When the main valve is opened, the barrel is pressurized and available for use. When the main valve is closed, water enclosed within the barrel is drained.
Since the main valve of the dry barrel hydrant is located underground, below the freeze line, the hydrant incorporates an automatic means for draining the barrel above the main valve after each use. The means for draining the hydrant barrel is usually an automatic drain valve working in conjunction with the operation of the main hydrant valve. The drain valve is automatically open, allowing water to drain from the interior of the barrel to the exterior of the hydrant, when the main hydrant valve is closed, and closed when the main hydrant valve is open. This process will maintain the hydrant barrel dry at all times during non-use and prevent corrosion or freezing of the hydrant.
Drain valves for fire hydrants may be of the slide valve type, spring loaded valve type, sliding tube type, or cam operated to open and/or closed type. The most predominantly used type of drain valve is the slide valve type. In this type of drain valve, the valve consists of a drain passageway and a drain valve facing strip. The drain passageway extends from the interior of the barrel, at a location just above the main valve, through the barrel or base of the hydrant to the exterior of the hydrant. The drain valve facing strip is located on a longitudinal rib extending upward from the main valve. The rib and drain valve facing strip are positioned such that the facing strip is either covering or not covering the opening of the drain passageway depending upon the position of the main valve.
In dry barrel hydrants, the drain valves operate automatically such that the drain passageway is either open, providing for drainage, or closed. Therefore, the passageway remains open whenever the main hydrant valve is closed. Consequently, when a hydrant is located in an area where water may collect for any period of time above the hydrant main valve, and thus the drain passageway, there is the opportunity for water or water with dirt, grit, and other foreign matter to backflow through the drain passageway into the hydrant. Backflow can cause damage to the hydrant's main valve or corrosion to the interior parts of the hydrant. There is also a danger of subsequent freezing if the backflow pressure is sufficient to raise the water level in the barrel above the freezing line.
To prevent backflow of water through the drain passageway some hydrants have incorporated backflow preventer valves. However, these devices are prone to mechanical failure, corrosion, and clogging by foreign matter. Failure of the backflow preventer exposes the hydrant to the backflow of ground water and may result in the release of high pressure water during hydrant use, resulting in water and water pressure loss and in destruction erosion of the soil surrounding the hydrant.
Clogging of the drain passageway is also an issue in wet areas where backflow of water and/or water with dirt, grit, and other foreign matter is likely. Clogging of the drain passageway prevents drainage of the barrel after use of the hydrant and can lead to corrosion of the interior of the hydrant and/or freezing of the water trapped in the hydrant barrel. In an attempt to prevent clogging of the drain passageway many hydrant drain valves are constructed of a force-flushing design. By this design, the drain valve remains open momentarily as the main hydrant valve begins to open and/or just before the main hydrant valve closes so that full main pressure is applied to the drain passageway to clear foreign material from the drain valve and passageway before the hydrants next use. However, this flushing is not guaranteed to remove all foreign matter and often results in destructive erosion of the soil surrounding the hydrant.
After use of the dry barrel hydrant, all water is automatically drained from the barrel into the immediate vicinity surrounding the hydrant. The flow of the water draining from the hydrant may result in general or localized erosion of the soil in the area surrounding the hydrant. Flushing and failure of backflow preventers results in destructive erosion of the soil surrounding the hydrant. Since the vast majority of hydrants are located in cities along sidewalk and roadways, the effect of this erosion over time results in undermining and eventual failure of these surfaces.
BRIEF SUMMARY OF THE INVENTION
Broadly stated the present invention relates to an improvement in a hydrant and, more particularly, to the addition of an improved drainage arrangement for allowing drainage of a dry barrel hydrants over a larger drainage field, thus, preventing erosive effects to the soil surrounding the hydrant, and for the prevention of the backflow of foreign matter into the hydrant. This drainage arrangement includes a diffusion means connected to the exterior of the hydrant at the outer end of the drain passageway(s).
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Wahlstrom, et al., “The Design and Manufacture of Fire Hydrants,” Design Project #1: Casting Manufacturing Methods Spring 2000 (Mar. 3, 2000).
“Types of Dry Barrel Hydrants” taken from AWWA Manual M17 www.firehydrant.org/info/drybarreltypes.html printed Jun. 29, 2000, 6 pages.
“Definitions and Names of Hydrant Components,” taken from AWWA Manual M17 www.firehydrant.org/info
omenclature.html printed Jun. 29, 2000, 2 pages.
“The Dry Hydrant Concept,” Step 3 www.firewise.org/pubs/operationWater/dry hyd concept.html printed Jun. 29, 2000, 2 pages.
“Installing Dry Hydrants,” www.firewise,org/pubs/operationWater/installing dry hyd.html printed Jun. 29, 2000, 3 pages.
“Dry Hydrant Design Features Checklist,” www.firewise.org/pubs/operationWater/dry hyd checklist.html printed Jun. 29, 2000, 2 pages.
McAndrews Held & Malloy Ltd.
Walton George L.
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