Fluid handling – Destructible or deformable element controlled – Heat destructible or fusible
Reexamination Certificate
1998-03-20
2001-03-20
Walton, George L. (Department: 3753)
Fluid handling
Destructible or deformable element controlled
Heat destructible or fusible
C251S214000, C251S315130, C251S315140, C251S368000, C277S359000, C277S500000, C277S914000, C277S931000, C277S938000, C277S946000
Reexamination Certificate
active
06202668
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to valves for industrial applications, and more particularly, to a valve having a fire-resistant seal which provides sealing therein when the valve is subjected to heat which can damage other sealing components therein.
2. Description of the Prior Art
Valves for use in controlling the flow of fluid through conduits or pipes are well known. A great variety of valves have been developed for various applications, and many of these are rotary valves which are operated by rotating a valve stem extending from a valve housing. One popular rotary valve configuration is the ball valve which has a rotating ball within a housing. The ball is actuated by a valve stem which is engaged with the ball. When the valve is closed, the ball blocks flow of fluid through the valve, and when the valve is open, a port through the ball is aligned with the inlet and outlet ports of the housing. A major advantage of ball valves is that they have substantially no restrictions therethrough and do not cause any significant pressure drop through the valve which can impede fluid flow.
Standards have been developed for industrial application valves by standards organizations, such as the American Petroleum Institute (API). These standards provide specifications for both design, materials and performance criteria, depending upon the application. It is particularly important in applications handling toxic or flammable fluids that these fluids are not released to the atmosphere in the event of fire or other catastrophe. To this end, a variety of sealing arrangements have been employed. A problem with such previous designs is that they use large radial graphite seals which need continual attention and maintenance to insure that they function when needed. Relatively high constant loading of such seals is necessary to overcome the potential of leakage to the atmosphere. Such high loads necessary to maintain the integrity of the seal result in increasing torque necessary to operate the valve. Further, the graphite seals can cause corrosion on the rotary valve stems, and this further increases the possibility of leakage. Details of some prior art valves will be discussed in more detail herein.
The valve of the present invention eliminates the need for a large graphite seal and the attention that such a seal requires. This is done by replacing the large graphite seal with a more resilient seal material and including a relatively smaller fire-resistant graphite seal which works only in the event of sufficient heat being applied to the valve. The new seal design of the present invention also results in considerably reduced loading and a corresponding reduction in torque necessary to operate the valve.
SUMMARY OF THE INVENTION
The valve of the present invention is designed with a fire-resistant seal for use in industrial applications where high heat conditions may exist and where maintaining the sealing of the fluid in the valve is critical under such conditions. The valve apparatus of the present invention comprises a body defining a pair of ports therein, a stem rotatably disposed in the body, a valve element engaged with the stem and movable in said body by rotation of the stem between an open position in which the ports in the body are in fluid communication and a closed position in which fluid communication between the ports is prevented, and a sealing apparatus for sealing the rotatable stem in the body both when in normal operation and when the valve is subjected to fire or other extreme heat conditions.
The sealing apparatus comprises a primary sealing means for sealing between the stem and the body during normal conditions, a thrust bearing disposed between the stem and body and adapted for absorbing thrust loading on the stem, and a fire-resistant seal disposable between the stem and body and adapted for sealing between the stem and body if the thrust bearing is substantially damaged by heat. In the preferred embodiment, the body has a body bearing surface thereon, and the stem has a stem bearing surface thereon spaced from the body bearing surface. The stem bearing surface is biased in an axial direction toward the body bearing surface by thrust loading from fluid pressure in the body. The thrust bearing is disposed between the body and stem bearing surfaces and is initially engaged therewith such that the thrust loading on the stem is absorbed. The fire-resistant seal is disposed between the body and stem bearing surfaces and is initially unengaged with at least one of the body and stem bearing surfaces. That is, the fire-resistant seal has a thickness less than an original thickness of the thrust bearing. The thrust bearing seals have an annular configuration and are generally concentric. The fire-resistant seal has an outside diameter smaller than an inside diameter of the thrust bearing and fits therein.
The thrust bearing is preferably made of a non-metallic, resilient material. For example, but not by way of limitation, the resilient material may be reinforced polytetrafluorethylene (PTFE).
The fire-resistant seal is preferably made of a heat-resistant material such that, if the thrust bearing is damaged by heat applied thereto, the fire-resistant seal will sealingly engage both of the body and stem bearing surfaces. A preferred heat-resistant material, but not by way of limitation, for the fire-resistant seal is graphite.
The space between the body bearing surface and stem bearing surface is substantially annular, and the thrust bearing and fire-resistant seal are initially disposed therein. A cavity is defined in the valve body adjacent to the body bearing surface and the fire-resistant seal. The cavity is formed by a chamfered surface extending from the body bearing surface. When sufficient heat is applied to the valve to damage the resilient material of the thrust bearing, the thrust loading on the valve stem caused by fluid pressure in the body will move the body and stem bearing surfaces together, and the material of the thrust bearing will be destroyed and/or extruded out of the space between the body and the stem bearing surfaces. As this occurs, the fire-resistant seal will sealingly engage both the body and stem bearing surfaces, as previously described, and sufficient thrust loading on the stem will cause at least a portion of the fire-resistant seal to be forced into the chamfered cavity. When this occurs, the fire-resistant seal will sealingly engage the surface of the chamfered cavity and also sealingly engage the radially outer surface of the stem and will further sealingly engage the stem bearing surface.
When the fire or high heat condition has been eliminated, and it is safe to dismantle the valve, the fire-resistant seal and the remains of the thrust bearing are easily removed and replaced with new components, assuming that the other parts of the valve are still safe to use.
Numerous objects and advantages of the invention will become apparent as the following detailed description of the preferred embodiment is read in conjunction with the drawings which illustrate such embodiment.
REFERENCES:
patent: 2647721 (1953-08-01), Volpin
patent: 3177887 (1965-04-01), Priese
patent: 3630483 (1971-12-01), Canalizo
patent: 4082105 (1978-04-01), Allen
patent: 4273148 (1981-06-01), Charland
patent: 4289157 (1981-09-01), McGee
patent: 4332370 (1982-06-01), Williams
patent: 4474203 (1984-10-01), Meyer
patent: 4519412 (1985-05-01), Grazioli
patent: 4558874 (1985-12-01), Williams et al.
patent: 4570659 (1986-02-01), Karr, Jr.
patent: 4658847 (1987-04-01), McCrone
patent: 4792118 (1988-12-01), Yusko, Jr. et al.
patent: 4822000 (1989-04-01), Bramblet
patent: 4976403 (1990-12-01), Bramblet
patent: 5056758 (1991-10-01), Bramblet
North American-Nutron Company Brochure entitled “Floating Ball Valves Series F150, Series F300, Series F600” (Apr., 1997).
North American-Nutron Company Brochure entitled “Floating Ball Valves, Carbon & Stainless Steel, Series C25, Series C30” (Apr., 1997).
North American-Nutron Company Brochure entitle
McAfee & Taft
North American Corporation
Walton George L.
LandOfFree
Valve with fire-resistant seal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Valve with fire-resistant seal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Valve with fire-resistant seal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441299