Fluid handling – Systems – Flow path with serial valves and/or closures
Reexamination Certificate
2003-05-07
2004-01-13
Lee, Kevin (Department: 3753)
Fluid handling
Systems
Flow path with serial valves and/or closures
C137S625320, C251S127000, C251S368000
Reexamination Certificate
active
06675832
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
(Not Applicable)
STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
(Not Applicable)
BACKGROUND OF THE INVENTION
The present invention pertains generally to fluid control devices and, more particularly, to a flushable blowdown valve adapted for the removal of sediment, pipe scale and other debris that may accumulate in boiler water of a boiler system.
In many applications such as power plants, paper mills and oil and gas refineries, boiler water is typically circulated through a boiler drum and/or boiler evaporator. Fuel such as natural gas, fuel oil or coal is utilized to heat the boiler water in the boiler drum in order to produce steam. The steam is routed to a turbine that rotates a generator for producing electricity. Over time, the boiler water in the boiler drum accumulates non-condensable, dissolved solids. For purposes of this discussion, such non-condensable, dissolved solids are referred to as debris. The debris may include dirt, sediment and piping scale.
If the debris is not removed from the boiler system, the boiler system will cease to function efficiently. A general rule of thumb in boiler system efficiency is that the heat transfer coefficient of the boiler system decreases by 10% for every 1% of debris (non-condensables) that is dissolved in the boiler water. Thus, a power plant may realize significant energy savings by improving the heating efficiency of the boiler system through a reduction in the amount of debris in the boiler water. The increased heating efficiency of the steam generation translates into significant cost savings through reduced fuel consumption.
Although de-mineralized feedwater may be utilized in boiler systems to minimize the accumulation of debris in the boiler drum, periodic blowdown of the boiler drum is still necessary in order to keep the boiler system free of debris and ensures its efficient operation. Periodic blowdown also provides for long and reliable equipment life while reducing maintenance time and expense. Blowdown may be performed manually on a daily basis or it may be performed semi-automatically wherein a timer is utilized to initiate blowdown for short periods according to a pre-set schedule.
The blowdown process involves activating a blowdown valve connected to the boiler drum and drawing off a small percentage of the debris-carrying boiler water from below the surface of the water in the boiler drum. The boiler water draining from the boiler drum may be pressurized up to about 5000 psi and may be heated to a temperature of up to 250° C. Conventional blowdown valves therefore may include an energy reduction device such as a diffuser to reduce the pressure and velocity of the boiler water. The energy of the pressurized and heated boiler water is typically reduced such that the high noise levels resulting from the expansion of boiler water exiting the blowdown valve may be minimized
Prior art gate valves are sometimes utilized as blowdown valves. Such prior art gate valves may include a diffuser or cage to reduce the energy of the passing high pressure boiler water. However, these prior art gate valves are configured such that fluid, including boiler water, must make a sharp turn in order to flow upwardly through a valve opening and through the cage. The combination of the pressurized boiler water and the debris carried therein acts to erode the valve body at the location near the valve opening where the flow sharply turns. Furthermore, such gate valves typically include a plug that tends to open relatively slowly such that the high-pressure boiler water will erode the plug and valve seat before the plug opens sufficiently. The erosion of the valve seat compromises closure of the valve such that leakage of the gate valve may occur. The constant leakage of the boiler water through the gate valve further accelerates the erosion damage to the valve seat.
The prior art includes blowdown valves that are configured to eliminate the above-described erosion problems of gate valves. Such blowdown valves combine a shutoff valve with a separate diffuser. The shutoff valve is an on/off valve that essentially protects the diffuser against erosion. More specifically, the shutoff valve protects a valve seat of the diffuser from erosion. In operation, the shutoff valve is initially placed in a closed or shutoff position. The diffuser is then opened and adjusted to allow for passage of a predetermined flow of boiler water.
The shutoff valve is then fully opened, allowing the boiler water to flow through the diffuser with minimal impingement upon the diffuser valve seat. By strictly limiting the shutoff valve to be fully opened or fully closed, the diffuser valve seat is not impinged by the boiler water. However, the boiler water occasionally carries debris that is too large to pass through the diffuser. Such large-sized debris accumulates at the entrance to the diffuser. Over time, the accumulation of debris may block the diffuser such that removal of the blowdown valve is necessary in order to remove the debris. Such periodic maintenance is both time consuming and costly.
The present invention specifically addresses and alleviates the above referenced deficiencies associated with prior art blowdown valves by providing a blowdown valve that combines a shutoff valve with a reversible diffuser or throttle valve. Advantageously, the throttle valve includes a pair of debris collection areas or debris zones located respectively on upstream and downstream ends of the throttle valve. When the accumulation of debris in one of the debris zones reaches a predetermined limit, the throttle valve is configured to be repositioned 180 degrees such that the debris-filled debris zone is placed downstream of the throttle valve where it may be flushed out of the blowdown valve by the flowing boiler water.
SUMMARY OF THE INVENTION
The blowdown valve of the present invention is adapted for the removal of sediment, pipe scale and other debris that may accumulate in boiler water of a boiler system. The blowdown valve is comprised of housing, a shutoff valve and a reversible throttle valve. The housing has a fluid inlet and a fluid outlet. The housing defines a housing axis. The shutoff valve and the throttle valve are disposed adjacent respective ones of the fluid inlet and the fluid outlet. During operation of the blowdown valve, the shutoff valve and the throttle valve are aligned with the housing axis. The fluid inlet and fluid outlet are in axial alignment with each other. The fluid inlet is fluidly connected to the boiler system and is configured for receiving fluid therefrom.
The shutoff valve is also fluidly connected to the fluid inlet and includes a rotatable, generally spherically-shaped valve ball having a shutoff valve bore formed therethrough. The valve ball is configured such that rotation through an angle of about 90 degrees alternately places the shutoff valve bore into and out of alignment with the fluid inlet. The shutoff valve is configured such that when the shutoff valve bore is rotated into alignment with the fluid inlet, the shutoff valve is unblocked such that fluid may pass through the shutoff valve bore. When the shutoff valve bore is rotated 90 degrees out of alignment with the fluid inlet, the passage of fluid through the shutoff valve is blocked.
The throttle valve is fluidly connected to and interposed between the shutoff valve and the fluid outlet. The throttle valve also comprises a rotatable, generally spherically-shaped valve ball having a throttle valve bore formed therethrough. The throttle valve bore includes a first end and a second end. A bore insert is interposed within the throttle valve bore between the first and second ends. The throttle valve bore is axially alignable with the fluid outlet.
The bore insert is configured for reducing energy of fluid flowing therethrough. The energy of the fluid is manifested in an elevated pressure and velocity of the fluid. The bore insert includes a plurality of passages configured to reduce the pressure and velocity of the fluid so as t
Freitas Stephen G.
Miller Stanley F.
Tran Duc Thanh
Control Components Inc.
Lee Kevin
Stetina Brunda Garred & Brucker
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