Raised hardface overlay valve seat

A raised hardface overlay valve seat, fused around the periphery of the port of a valve, having an inverted frustoconical body cavity and an inverted frustoconical plug inserted into said cavity in sealing engagement therewith. A major advantage of the raised hardface overlay seat is that it has a taper conforming to the taper of the plug and as a consequence, reduces the area in contact with the plug and effectively intensifies the sealing stress that can be generated between the plug and the seats by a downward force. The plug may be used with lapping compound to lap the seats, both prior to service and in the field. Sufficient space is allowed in the cavity for a substantial relap life.

FIELD OF THE INVENTION 
This invention relates to metallic valves. More specifically, this 
invention relates to plug valves of the quarter-turn variety and to plug 
valves which move vertically within the valve cavity to open and close the 
valve, paralleling the traditional gate valve design. 
BACKGROUND OF THE PRIOR ART 
Applicant is aware of the following prior art: 
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U.S. PAT. NO. INVENTOR DATE 
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4,239,185 Lowe 1980 
3,743,556 Breton, et al 
1973 
3,916,506 Wolf 1975 
3,864,124 Breton, et al 
1975 
4,194,040 Breton, et al 
1980 
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SUMMARY OF THE INVENTION 
A raised hardface overlay valve seat is fused onto the metallic body 
surrounding a port of the opposed sides of the frustoconical wall of the 
body cavity of a valve, so that the area of contact of the metal plug, 
having an inverted frustoconical surface, which is parallel to the 
frustoconical wall of the body cavity, is limited to the area of the 
raised seats. Thus, the plug seals the flow-through passage when it is in 
engagement with the seats and allows flow through the body of the valve 
when the plug is out of engagement with the hardface overlay seats. The 
invention is in two embodiments. One involves a quarter-turn plug valve of 
the type previously disclosed and claimed by Lowe, in U.S. Pat. No. 
4,239,185, and the other involves a gate type plug valve with a sealing 
plug which need not turn, but which moves vertically in response to the 
rotation of the valve handwheel/yoke nut assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The invention is applicable to two embodiments of plug valves. 
QUARTER-TURN VALVE 
One embodiment relates to a quarter-turn through-flow plug valve of the 
type disclosed and claimed by Lowe, in U.S. Pat. No. 4,239,185. This valve 
is illustrated in FIG. 1 and the valve stem for use with this valve is 
illustrated in FIG. 5. The valve 1 consists of a body 2, having a cavity 3 
of an inverted frustoconical shape. The through-flow passage 4 extends 
from the threaded portion 5 to port 6 into the cavity. The port 6 is 
surrounded by a hardface raised seat 7 which extends from the wall of the 
cavity 3 toward the plug 25, but does not extend into the through-flow 
passage 4. The hardface raised seat is formed from a fabric-backed 
hardface composite 8 (FIGS. 3A and 3B) which will be described in more 
detail hereinafter. Suffice it to say that the composite is cut so as to 
form an opening 9 to conform to the port 6 and the hardface cloth 
composite is adhesively secured, in a preferred embodiment, to the 
periphery of port 6. The metal 10 surrounding the port is prepared by grit 
blasting or by pickling, so as to accept the fabric-backed hardface 
composite. A bonnet 11, containing threads 12, is fitted into the body 2 
of the valve and a bonnet flange 13 is secured to the body portion by 
bolts, not shown. A spiral-wound gasket 14 is inserted between the body 
and the bonnet to prevent leakage around this area of contact. The plug 25 
contains a through-flow passage 33 and threads 27 attached to the unitary 
stem 26. 
ASSEMBLY 
During assembly, stem 26 is fitted into bonnet 11 so that stem threads 27 
engage bonnet threads 12. The plug is fitted into the frustoconical cavity 
3 so that the through-flow passage 33 extends perpendicularly to the major 
axis of the through-flow passage 4 of body 2. Bonnet 11 is turned in 
relation to stem 26 which lowers the plug 25 in the cavity 3. When the 
wall of the frustoconical plug sealingly engages the raised surface of 
valve seat 7 (closed position), bonnet flange 13 is placed over the 
assembled stem and bonnet and bolted to the body 2. This assures proper 
sealing force of the plug 25 against the seats 7 and proper orientation of 
the through-flow passages 33 and 4 in the closed position. In this 
embodiment, the plug and the stem are unitary, i.e. machined from a single 
piece of metal. As illustrated in FIG. 1, the stem is surrounded by a 
series of packing rings 19, which is held in position by a packing gland 
20, which is secured to the bonnet 11 by a packing nut 21. A metal packing 
ring 18 prevents extrusion of the packing rings around the stem 26. The 
stem 26 extends through the bore of the packing nut 21 and is attached by 
a handle 30 (shown 90.degree. displaced for purposes of illustration) 
which extends over into a lever arm 31 and is held in place by a lock nut 
32. The end of stem 26 is machined square as shown in FIG. 5 to engage the 
square bore 29 of lever arm 31. As previously indicated, the lever arm 
turns only one-quarter of a turn from open (limited by a stop pin, not 
shown) to valve closure against seat 7. The plug, in closed position (as 
shown in FIG. 1) wedges across the raised hardface seat 7 on either side 
of the cavity. Since the hardface seat is fused onto the wall of the valve 
body cavity surrounding the port, the valve can accommodate high 
temperatures and does not require a great deal of torque to turn from open 
to closed position. This is because the only contact of the plug is in the 
vicinity of the raised seats 7 and turning of the valve plug 25 a quarter 
of a turn tends to raise the plug to an area of smaller diameter, 
therefore relieving the compression of the plug against the seat 7. This 
allows for easy movement from closed to open. In closing the valve, the 
movement of the lever arm is in the opposite direction, which turns the 
through-flow passage 33 away from the port 6 and lowers the plug 25 as it 
is turned into wedging position against the raised seats 7, thus sealing 
the valve against flow therethrough. 
GATE TYPE PLUG VALVE 
The gate type plug valve is illustrated in FIG. 2 and again consists of the 
valve body 2, containing the inverted frustoconical cavity 3 and a 
through-flow passage 4, extending to the threaded portion 5 and the port 
6. Again, surrounding the port is the hardface raised seat 7. The 
construction, however, of the stem differs somewhat, since, in the gate 
type plug valve, the plug 55 can rotate freely when disengaged from valve 
seats 7. Rotation of the handwheel/yoke nut assembly causes the 
nonrotating stem 56 to lower and lift the plug vertically in and out of 
engagement with the seats 7. This is accomplished by means of a valve stem 
56, having a hexagonal guide member 57 near its base, which fits into a 
threaded bushing 28 with an internal hexagonal hole 15, mounted in the 
bonnet 11 of the valve. The up and down movement of the plug 55 is 
initiated by rotation of the handwheel/yoke nut assembly 36 and 23. The 
stem 56 is restrained from rotation by its hexagonal guide 57 engaging in 
the fixed hexagonal bushing 28 and shaped hole 15. Thus, rotation by the 
handwheel/yoke nut 36 and 23, engaged with stem thread 38, causes the stem 
56 to move in an upward or downward motion, depending on handwheel/yoke 
nut rotation direction. Referring to the stem and plug, these are shown in 
FIG. 8. The stem 56 is an integral piece with threads 38 at the top, to 
engage with the threads, not illustrated, of the yoke nut 23, upon 
rotation of the handwheel 36. 
The hexagonal guide 57 is cut away to form a shoulder 44 and a neck portion 
42, which terminates in a button 43. The button slides into the U-shaped 
slot 46 and the neck portion 42 slides into the collar slot 45, extending 
to the top surface of the plug 55. 
The handwheel/yoke nut assembly is located outside of the valve portion 
proper and is supported by means of a yoke 16. 
The bonnet 11 is connected to the body 2 by bonnet bolts, not shown, and 
the valve stem 56 is surrounded by packing rings 19 retained by packing 
gland 22. The packing gland 22 is held in position by means of gland bolts 
40 and gland nuts 41. 
The yoke nut 23 is separated from the yoke 16 by the bearing ring 35 and 
the handwheel is connected to the yoke nut by means of jamb nut 37. As is 
shown, space 60 is left in the bottom of the valve cavity to allow for 
relapping of the hardface raised seats 7. 
The tools for affecting the relapping procedure are shown in FIG. 7 and in 
FIG. 9. In the case of the quarter-turn valve, a lapping fixture 59 is 
fitted over the body 2 of the valve and this, as is illustrated, may be 
made of plastic, wood or metal. The purpose of the lapping guide 59 is to 
maintain the stem in proper orientation during rotation of the plug 25 at 
low speeds against the surface of the raised seats 7. As is shown, the 
stem in this case extends through the bore of the lapping guide to a chuck 
61, which is driven at low speeds by a variable-speed drill (not shown). 
In the case of the gate type plug valve, a special fixture is used, 
involving a shank 50, again with a cut at the bottom to form a shoulder 51 
and a neck 52, terminating in a U-shaped button 53. The U-shaped button 53 
fits into the U-shaped slot 46 and the neck portion 52 fits into the 
collar slot 45, with the shoulder portion resting on the upper surface of 
the plug 55. The U-shaped button 53 fixes the plug to the fixture 50 and 
thus rotation of the fixture 50 turns the plug 55 within the valve body 
cavity and against the seat surfaces 7. 
In the case of the quarter-turn valve, the regular plug 25 and valve stem 
26 are used. This is illustrated in FIG. 7, in use with the lapping guide 
59. Lapping guide 59 may be used as illustrated in FIG. 7. 
RAISED HARDFACE OVERLAY VALVE SEAT 
The hardface overlay raised valve seat 7, according to a preferred form of 
this invention, is prepared from a fabric backed hardface alloy composite. 
Such composites have been described in U.S. Pat. Nos. 3,743,556; 
3,916,506; 3,864,124 and 4,194,040. The process of forming the composites 
is also described by Shewell, in Metal Progress, November, 1983, pages 
1-6. A hardface alloy is one having a solidus temperature lower than the 
metal of the material to which it is to be joined and which, in the molten 
state, wets the metal and contains a powdered filler, having a solidus 
temperature higher than either the metal to which it is to be joined or of 
the hardface alloy and which is wetted by the molten hardface alloy. 
In order to control the shape of the seat as it is applied around the 
periphery of the port 6, a fabric-backed hardface composite is formed in 
which the fabric consists of fibrillated polytetrafluoroethylene. The 
metal particles are mixed into the fibrils of polytetrafluoroethylene 
(Teflon.RTM.) * which entrap the powder particles. Many different alloys 
can be utilized (see Shewell, loc. cit.). However, in a preferred 
embodiment, a nickel-chromium-boron alloy is embedded into a fibrillated 
polytetrafluoroethylene and formed into a fabric-like material. A cobalt 
alloy powder is mixed with the fibrillated polytetrafluoroethylene and the 
two sheets, or lamina, of the composite are joined together and formed 
into a single sheet. Thereafter, the laminated hardface composite is cut 
into the desired shape, as is shown in FIG. 3 (see also Shewell). 
FNT Registered trademark of E. I. duPont de Nemours 
Breton, in U.S. Pat. No. 3,864,124 and in 4,194,640, uses the words "braze 
alloys" and "hardface alloys" almost synonymously. He lists a series of 
intermetallic compounds that could be used as the hardface powdered 
component of the hardface overlay and quotes the Braze Manual of the 
American Welding Society as to the characteristics of a braze alloy. (See 
also Baumeister, loc. cit.). 
The powdered materials, in the past, have included various refractory 
materials, as for example, titanium carbide and the like. However, it has 
been found that cobalt particles tend to give to the overlay antigalling 
and corrosion protection characteristics. Thus, the overlay material may 
be described as one with islands of cobalt in a matrix of 
nickel-chrome-boron alloy. 
Once the fabric particle component is cut to the desired shape, it is 
adhesively secured to the treated, prepared metal 10, FIG. 4, surrounding 
the port 6, by glue, shellac or the like. 
The valve body base metal 10 is preferably prepared by an acid pickling 
treatment or by a grit blast, as described by Shewell and as is well known 
in the art. 
Thereafter, the entire treated valve body is heated in a hydrogen 
atmosphere or other controlled atmosphere at temperatures so as to 
vaporize the Teflon.RTM. or polytetrafluoroethylene and to braze the 
nickel-chromium-boron alloy and the cobalt particles and fuses them to the 
steel valve body surface. While the furnace brazing atmosphere is 
controlled, there are other methods of applying hardfacing, such as laser 
beams, plasma-arc welding, induction brazing, diffusion techniques, vacuum 
brazing and the like (see Marks', loc. cit.). 
The semi-finished valve body has a raised hardface overlay alloy seat fused 
to the wall of the metal of the body cavity. The raised hardface overlay 
alloy seat extends from the wall of the body cavity 3, toward the plug 25. 
The seat 7 does not extend through the port 6 into the through-flow 
passage 4. This is of considerable importance, since there is no 
possibility of developing a leak or cavitation between the seat 7 and the 
wall of the port 4, as has been the case with the tubular valve seats in 
which the tube extends into the through-flow passage. 
Thereafter, the raised seat is machined, lapped by conventional processes 
and assembled in the factory. The valve is ready for installation 
thereafter in the field. 
FIELD LAPPING 
One of the major advantages of the raised hardface overlay valve seats of 
this invention resides in the fact that the valves can be lapped in the 
field. 
As previously indicated, the plugs 25 and 55 can be used as the lapping 
tool and, in the case of the quarter-turn valve, the plug 25 and valve 
stem 26 are utilized with the lapping guide 59, illustrated of wood (see 
FIG. 7). 
In order to field lap the valves, it is necessary, of course, to take the 
valve out of service and to remove the bonnet flange and the bonnet and 
the valve stem 26. The stem 26 is then removed from the bonnet 11. 
Thereafter, the valve stem 26 and plug 25, in the case of the quarter-turn 
valve, are inserted through the bore in the lapping guide 59, which is 
attached to the flange of the valve body 2. Lapping compound is applied 
directly to the plug and the stem 26 is inserted into a chuck 61 and 
driven at low speeds, in contact with the surface of the seats. Various 
commercial lapping compounds are available, but a 180 grit, water- or 
oil-based silicon carbide material is preferred. It is also possible, of 
course, to use diamond powder in an oil or water base as the lapping 
compound (see Marks',loc. cit.). 
FIELD ASSEMBLY 
Since the lapping of the seats with the plug changes the orientation of the 
through-flow passage 33 of the plug 25 with the axis of the through-flow 
passage 4 of the valve body 2, it is necessary, in the case of the 
quarter-turn valve, to reassemble the valve after lapping. This involves 
orienting the through-flow passage 33 of the plug 25 at right angles to 
the major areas of the through-flow passage 4 of the body 2. The bonnet 11 
is then turned in relation to stem 26, thereby moving plug 25 downward so 
that it again sealingly engages seat 7. This means that the frustoconical 
wall of plug 25 is in sealing engagement with the raised surface of the 
hardface valve seat 7. Thereafter, the bonnet flange 13 is fitted over the 
stem and bonnet assembly and bolted to the valve body. This, then, assures 
proper orientation of the plug 25, through-flow passage 33 and 
through-flow passage 4, in the position of valve closure, even after one 
or more lapping procedures. 
As previously mentioned, there is an area of space left in the bottom of 
the valve cavity 3, which is designated by numeral 60 as the relap life. 
This space, then, allows for the valve to be relapped several times in the 
field before the valve plug finally contacts the bottom of the valve 
cavity. 
As previously mentioned, the arrangement for a valve lapping tool for the 
gate type plug valve is somewhat different than the quarter-turn valve, 
since the stem 56 is not permanently attached to the plug 55. Therefore, a 
shaft 50 is provided which does not have the hexagonal guide means 57, but 
which has a cut-away portion, forming a shoulder portion 51, a neck 
portion 52, and terminating in a U-shaped button 53, which slides into the 
U-shaped slot 46. The throat portion 52 then slides through the collar 
slot 45 and the shoulder 51 of the shaft rests on the upper surface of the 
plug 55. The U-shaped button 53 engages the plug to the shaft, thus 
allowing the shaft to turn when connected to chuck 61 to turn the plug 55 
with the lapping compound, allowing the fine finish of the hardface 
overlay seats and mated plug. Again, this allows for relapping of the 
seats in the field. 
Many valve modifications will occur to those skilled in the art from the 
detailed description hereinabove given. Such description is meant to be 
nonlimiting, except insofar as to be commensurate in scope with the 
appended claims.