Fire resistant seat for butterfly and ball valves

The invention contemplates a flow control valve that provides emergency sealing action upon inadvertent, thermally induced failure of the primary seal. The body of the valve includes an annular shoulder that is disposed adjacent an annular seat; and an annular collar of substantially incombustible corrosion resistant, nongalling material is specifically mounted on the shoulder, the collar including a first portion hermetically connected to the shoulder and a second, lip like portion free to move with respect to the shoulder and normally spaced from the selectively positionable valve element. This collar and more specifically the lip portion thereof is provided with prestressed regions normally situating the lip portion proximate the body shoulder and in position wherein said lip portion will not interface with the movable valve element. Upon thermal relief of the stresses stored in such regions, the collar reacts to dispose the second, or lip portion into sealing engagement with the valve elements when in the flow aperture closing position. This stress relief is permanent, such that upon subsequent cooling of the valve, the collar lip portion will remain in sealing engagement with the valve element, thereby preventing leakage, even though the primary seal may have been destroyed by the thermal event.

BACKGROUND OF THE INVENTION 
This invention relates generally to flow control valves and more 
particularly to such valves that provide for continuity in valve sealing 
action upon exposure to fire or any like, extraordinary thermal event. 
Ball valves and butterfly valves used in regulating the flow through pipes 
carrying petroleum hydrocarbons and like fluids commonly incorporate 
elastomeric seals fabricated from such materials as fluorocarbon polymers, 
polyurethanes, and various olefinic polymers and copolymers. Even the more 
thermally stable of these materials fail in their valve sealing function 
at temperatures in excess of about 650.degree. F. In my U.S. Pat. No. 
3,537,682, I have disclosed inorganic valve seals which function 
effectively at temperatures on the order of 1200.degree.-1300.degree. F. 
However, the latter seals are costly and are less desirable than 
elastomeric seals for use at more conventional operating temperatures. In 
addition, it has been known heretofore to construct flow control valves 
with auxiliary metal seats or seals which are normally disposed in 
approximate contact with the valve element and which rely primarily upon 
thermal expansion during a fire or the like in order to effect a safety 
sealing action. Under normal conditions these seals will not provide an 
effective seal, as to do so would require a degree of engagement with the 
movable valve element that would impede the desired ease of valve 
operation. Accordingly, upon cooling down after the fire has been struck, 
these prior art metal seals will contract and assume their normal 
position, resulting in an interuption of the contact with the valve 
element, creating a danger of leakage. 
It is, therefore, an important object of my present invention to provide a 
flow control valve with an auxiliary seal that affords continued sealing 
action after once having been exposed to extraordinary high temperatures 
and regardless of subsequent cooling. 
A more general object of the invention is to provide a new and improved 
flow control valve having fire safety features. 
Another object of the invention is to provide a fire safety valve which 
functions regardless of the direction of flow pressure. 
These and other objects and features of the invention will become more 
apparent upon a consideration of the following descriptions.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
Referring now in detail to the drawings, specifically to FIGS. 1 and 2, a 
disc or butterfly valve 10 which is constructed in compliance with the 
present invention is shown clamped in flow control relationship between 
the ends of a pair of aligned pipes or conduits 12 and 14. Each of the 
pipes 12 and 14 is provided with an end flange 16 rigidly attached 
thereto; and a suitable number of nut-and-bolt units 18 is disposed in a 
circular pattern for use in drawing the flanges 16 toward each other in 
order to clamp the valve 10 therebetween. 
The auxiliary fire safety seal of the present invention is usefully 
employed in various types or styles of valve. For purposes of the present 
disclosure, it is illustrated in conjunction with the construction of a 
disc or butterfly valve, such as is disclosed in my U.S. Pat. No. 
3,563,510. Accordingly, the valve 10 includes a main valve body 20 and a 
valve body clamping ring 22 which cooperate to define an annular groove or 
valve seat 24. A flow control valve element or disc 26 is mounted on a 
support shaft 28 for rotation between a closed position indicated in solid 
outline in FIG. 2 and an open position shown in broken outline in that 
illustration, the arc of traverse of the valve disc or element 26 being 
indicated by the reference numeral 30. The valve element 26 is preferably 
crowned in transverse section to present a spherical curvature to a 
polymeric primary seal ring 32. An operating handle 34 is attached to the 
shaft 28, as shown in FIG. 1, for selectively positioning the valve 
element 26 with respect to the circular valve opening defined by the 
primary sealing ring 32; and if desired, provision for locking the handle 
in a desired position may be incorporated in the valve 10 by means 
including an anchor plate section 36. Means for biasing the valve element 
26 into valve closing condition is also use fully included in the valve 
10. 
With particular reference to FIG. 2, the primary sealing ring 32 comprises 
a strip 38 of yieldable, resilient polymeric material, such as 
polytetrafluoroethylene, folded about an annular, elastomeric reinforcing 
member 40 having normally torodial shape. Such an arrangement has been 
termed a caulking ring. 
Other details of the construction of valve 10, the normal mode of operation 
thereof, and cooperation of the respective parts are described more fully 
in my aforesaid U.S. Pat. No. 3,563,510. However, in compliance with the 
principles of the present invention, the valve body 20 and specifically 
the clamping ring 22 is arranged to define an annular shoulder 42 situated 
generally in the downstream direction from the annular valve seat 24, as 
is best seen in FIG. 3. In further compliance with the present invention, 
an annular collar 44 which is to provide the auxiliary or emergency seal 
is fabricated of a substantially incombustible material, and is to be 
mounted on the shoulder 42. Collar 44 includes a first downstream edge 
portion 46 that is hermetically connected to the shoulder 42, as by a 
continuous annular weld 50 and a second upstream lip portion 48 which is 
free to move with respect to the shoulder 42. Advantageously, the collar 
44 is fabricated from a suitable corrosion resistant metal, preferably 
stainless steel, or similar alloy which is selected due to its ability to 
release stored stresses upon being heated above a predetermined 
temperature. 
Continuing with reference to FIG. 3 the configuration of the collar 44 will 
now be considered in greater detail. It should be noted, however, that the 
design of collar 44 shown in the drawings, while possessed of novel 
features in and of itself, has been selected for purposes of illustration 
and discussion of the broad concept of the overall invention. Indeed, it 
is contemplated and intended that other collar designs can and will be 
employed without departure from the invention, depending of course, upon 
the structure of the valve and the particular use thereof. 
With the above in mind, attention is directed to the collar 44 of FIG. 3. 
More specifically, the first, or downstream edge 46 of said collar 44 is 
of a greater cross sectional thickness than the lip portion 48. Edge 46 is 
received in an annular notch 49 in shoulder 42 to facilitate positioning 
and welding of the collar 44 to the valve body component 22. Extending 
from the annular edge portion 46 is the annular lip portion 48, having a 
free end section designated generally 52 and spaced slightly from the 
shoulder 42. The lip portion 48 is preferably shaped, in cross-section, to 
correspond to a beam of constant stress. That is to say, the 
cross-sectional thickness of the lip portion 48 at location 54 is greater 
than that at location 56, which in turn is greater than the cross-section 
thickness at location 58 proximate the free end 52. These dimensions and 
the taper of the lip 48 can be determined by standard formulas to provide 
an approximately constant stress along the length of said lip. In 
addition, the tapered configuration insures that the free end 52 will flex 
elastically after being brought into contact with the valve element 26 
subsequent to the thermal event. This feature, thus permits the valve 
element to be operated after said thermal event, without the danger of 
permanent deformation of the lip portion 48 and destruction of its ability 
to seal effectively against the valve element 26. 
Turning now to the method of fabricating the overall valve, the collar 44 
is initially formed to the general configuration as shown in FIG. 4, with 
the exception of the free end 52 which extends approximately as shown in 
dotted outline. Thus, with the illustrated design, the collar 44 can be 
easily disposed within the bore of clamp ring 22 and then assembled to the 
shoulder 42, such as by the weld 50. Next, the collar 44 and most 
particularly the lip portion 48 is stretched circumferentially, by rolling 
or some other suitable well-known method of cold working to attain a 
stressed circumferential dimension of the general configuration as shown 
in FIG. 3, viz., with the lip portion 48 disposed such that it will not 
adversely affect or interfere with the operation of the valve element 26. 
For collar 44, the exact cold working process and sequence of operation, 
i.e., whether cold worked prior to or after connection to the valve body 
element, depends to a great extent upon the particular valve structures 
and operational features. Thus, it is to be understood that the disclosed 
method of fabrication wherein cold working by rolling is effected after 
the collar 44 is assembled, is illustrative of one form of the overall 
concept of the invention. Accordingly, where the valve design permits, the 
auxiliary or emergency seat or seal may be cold worked by alternate known 
process, other than rolling, and/or assembled to the valve body component 
after cold working, without departing from the invention. 
With continued reference to FIG. 3, and the illustrated embodiment, the 
circumferential stretching of the lip portion 48 alters the dimension of 
said lip so that it will be disposed in closer proximity to shoulder 42, 
with the free end 52 undergoing the greater increase in circumferential 
dimension. This relationship is illustrated by a comparison of FIGS. 3 and 
4. While it would be desirable to have the lip portion 48 in engagement 
with shoulder 42, to reduce wear thereof due to any abrasion in the fluid 
passing through the valve and to assure that it does not contact the valve 
element 26 during normal operation, this is not practical with the 
illustrated embodiment and method of assembly. More specifically, due to 
the resilient nature of material from which collar 44 is fabricated, and 
the limitations upon its deformation during cold rolling existing due to 
its prior attachment to the lip 48 cannot be stretched sufficiently to 
attain flush contact with said shoulder and will tend to return to a 
position wherein it is slightly spaced from said shoulder 42. 
As an additional matter, and as noted above, it is preferable that the lip 
portion 48 not contact the valve element 26 during normal operation, since 
a high degree of contact would tend to increase the force required to 
operate the valve, or could result in galling between lip portion 48 and 
the valve element. It can be appreciated, however, that a slight degree of 
engagement of the free end 52 with the valve element 26 can be tolerated, 
provided it does not increase operating force requirements above 
acceptable levels and does not induce galling. 
Discussion will now be directed to the ability of the valve as discussed 
above, to provide an effective seal both during and after a thermal event. 
Accordingly, should the valve and its component collar 44 be exposed to 
excessive high temperatures, as upon exposure to a fire or other 
extraordinary thermal event, sufficient to destroy the ability of the 
primary seal 32 to block fluid flow, the stresses stored in the collar lip 
portion 48, will be relieved thermally and said lip portion 48 will tend 
to return to its original shape. As this occurs, the lip 48 will move into 
sealing engagement or contact with the valve element 26; or at least 
assuming a position such that when said valve element 26 is closed, said 
engagement will result, as is shown in FIG. 4. Of specific importance here 
is the fact that this relief of the collar 44 and repositioning of lip 
portion 48 is permanent, and subsequent cooling will not disrupt the 
engagement of the lip portion 48 with the valve element 26. 
Partial destruction of the primary sealing ring 32 has been suggested in 
FIG. 4, as well as invasion by line fluid of the space between the 
shoulder 42 and the collar 44. As will be appreciated, upstream pressure 
elastically deflects the valve element into contact with the collar and 
thus promotes the creation of a seal between valve element 26 and the end 
48 of collar 44. However, elastic memory of the collar alone, upon release 
of the stored stresses, can be arranged to provide an effective seal, even 
under conditions of backpressure from the downstream side of the valve 
element. 
The drawings and the foregoing descriptions are not intended to represent 
the only form of my invention in regard to the details of its construction 
and manner of operation. Changes in form and in the proportion of parts, 
as well as the substitution of equivalent, are contemplated as 
circumstances may suggest or render expedient; and although specific terms 
have employed, they are intended in a generic and descriptive sense only 
and not for the purposes of limitation, the scope of the invention being 
delineated in the following claims.