Fluid handling – Systems – Dividing into parallel flow paths with recombining
Patent
1998-10-05
2000-08-15
Hepperle, Stephen M.
Fluid handling
Systems
Dividing into parallel flow paths with recombining
1375123, 1375147, 1375278, F16K 4702
Patent
active
061020729
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a water hammer preventing check valve to be installed in a pipeline for transporting a fluid, capable of surely and safely preventing water hammer due to the reverse flow of a fluid in the pipeline and pressure rise in the same when the supply of power to a pump is stopped suddenly to stop the transportation of the fluid.
In this specification, the term, "water" is used for the general designation of fluids. The terms, "upstream side", "downstream side (discharge side)", "inlet" and "outlet" are used to designate positions and directions with respect to the direction of normal flow (not the reverse flow) of a fluid.
BACKGROUND ART
When a pump is stopped to stop supplying a fluid, such as water, a check valve installed in a pipeline for conveying the fluid is often unable to deal with a sudden change in the state of the fluid, i.e., normal flow .fwdarw.stop .fwdarw.reverse flow, the check valve closes with a delay, and the valve element of the check valve is seated on the valve seat of the same after the start of the reverse flow of the fluid. Consequently, water hammer is created in a section of the pipeline on the downstream side of the check valve at the moment the check valve is closed, which sometimes cause a serious trouble.
Inventions relating to check valves for preventing such water hammer are disclosed in, for example, JP-40-3654B(Water Hammer Preventing Pumping Apparatus), JP-51-25930B (Improvements in Water Hammer Preventing Pumping Apparatus), and JP-63-60274 B(Swing Type Water Hammer Preventing Check Valve). These inventions will inclusively be designated as "original inventions". As is generally known, those prior art check valves have prevalently been used. The present invention relates to improvements in the water hammer preventing check valves of the original inventions.
The prior art water hammer preventing check valves of the original inventions are based on clear technical ideas surpassing generally known symptomatic technical ideas of preventing water hammer (symptomatic means which allows the valve element to be seated on the valve seat after the start of reverse flow, and retards the operation of the valve element by a damping means or installs an automatic valve and a surge tank in the pipeline to relieve shocks). It can readily be gathered from descriptions in the specifications of the original inventions that the technical ideas on which the original inventions are based include radical improvements intended to stop a reverse flow in a pipeline for the positive elimination of causes of water hammer by forming a valve element and flow passages around the valve element so that the valve element is seated substantially on a valve seat at the moment the inertial flow of a fluid in a discharge direction in the pipeline stops when the conveyance of the fluid is interrupted.
As shown by way of example in FIG. 3, a water hammer preventing check valve of the original invention is constructed so as to eliminate as many factors obstructing a valve closing motion as possible as indicated by solid lines; that is, a valve element is designed so that the valve element has an adjusted shape and a reduced mass, provides the least possible inertial resistance, and is subject to the lowest possible form drag or shape drag. This valve element is capable of performing an appropriate closing motion by its own weight in quick response to the reduction of the flow velocity of the fluid, small errors can be corrected by an additional valve closing force exerted by a weight or a spring, and thereby water hammer can be nearly perfectly prevented.
However, even the water hammer preventing check valve of the original inventions has an unsolved technical problem that "pressure rise" after the valve has closed cannot be prevented.
If the valve closes without delay, the velocity of water (fluid) at a position in front of the valve seat and that of water at a position behind the valve seat at the moment the valve element is seated on the valve seat are approxim
REFERENCES:
patent: 419447 (1890-01-01), Hussey
patent: 1029600 (1912-06-01), Foster
patent: 2930400 (1960-03-01), Wheatley
patent: 3144045 (1964-08-01), Fitzpatrick
patent: 3144876 (1964-08-01), Frye
patent: 4217931 (1980-08-01), Jaekel
patent: 4617959 (1986-10-01), Yamada
patent: 5746246 (1998-05-01), Yokota
patent: 5769116 (1998-06-01), Yokota
Yokota Hiroshi
Yokota Shingo
Hepperle Stephen M.
Kabushiki Kaisha Yokota Seisakusho
Yokota Hiroshi
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