GB1584835A

GB1584835A - Double disc gate valve with replaceable spacer ring

Info

Publication number: GB1584835A
Application number: GB3076277A
Authority: GB
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1976-08-17
Filing date: 1977-07-21
Publication date: 1981-02-18
Also published as: ES461682A1; FR2362321B1; CH626145A5; AU2720477A; DE2736708C2; BR7705439A; JPS604394B2; SE432984B; MX144942A; DE2736708A1; IT1085745B; SE7709227L; JPS5324627A; CA1066259A; AU513511B2; NL7708748A; FR2362321A1

Abstract

The gate (26) of the valve has a pair of identically shaped closing discs (100, 102), the annular hardened seating surfaces (104) of which come into closing contact with a valve seat (56). During the opening and closing of the valve, tongues on the sides of the closing discs slide in vertical grooves. The closing discs (100, 102) are separated from one another by an annular spacer (120), the diameter of which is less than the diameter of the seating surfaces. The spacing ring is secured in position by raised portions on the inner side of the closing discs (100, 102) which engage from the inside in the spacer ring (120). The spacer ring guarantees the correct width of the gate (26) in accordance with the amount of wear. The difference in diameter between the valve seating surfaces (104) and the spacer ring (120) provides the gate with increased flexibility. <IMAGE>

Description

(54) DOUBLE DISC GATE VALVE WITH REPLACEABLE SPACER RING (71) We, ROCKWELL INTERNATIONAL CORPORATION, of 600 Grant Street, Pittsburgh, Pennsylvania 15219, United States of America, a corporation of the State of Delaware, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to gate valves and in particular to a gate valve having a. twopiece gate construction.

Two-piece or double disc gates have been proposed for gate valves because of certain inherent functional and manufacturing advantages. Such constructions, in view of the larger freedom of movement of the independent gate pieces, can conform to larger manufacturing variations in the pieces and the valve seats while, at the same time, provide complete sealing despite distortion of the seats due to differential heating and cooling rates and system stresses. One example. of this type of valve is described in our British Patent No. 1,543,939.

The object of the present invention is to provide a gate valve which is reliable in service, easily maintained, and simple to manufacture while retaining the advantages of the two-piece gate construction.

According to a first aspect of the invention there is provided a gate valve comprising a valve body having flow passages communicating with a central valving control chamber; valve seats in the valve body at the ends of the flow passages adjacent the control chamber; a gate assembly movable between an open position and a closed position by an external stem assembly operably connected to said gate, said gate assembly comprising a pair of gate pieces each having a seating surface formed on one side thereof for sealing engagement with a respective valve seat in the closed position when mutually facing surfaces on the reverse sides of the gate pieces are spaced a predetermined distance apart, and a single rigid circular spacer member remote from said stem assembly having end surfaces respectively engaging said mutually facing surfaces and having a thickness therebetween determining said distance apart of said pieces, capturing formations of each of said gate pieces bounding the outer circumferential wall of said spacer member on assembly and projecting from said mutually facing surfaces by an effective combined distance less than the thickness of the spacer member; and guide means preventing separation of the pieces during gate movement which would permit disengagement of the spacer member from the capturing formations.

According to a second aspect of the invention there is provided a gate valve comprising a valve body having a pair of flow passages coaxially disposed along the flow axis, said flow passages having inner ends communicating with a central valving control cha.mber and outer ends connectable into a fluid flow line, said control chamber having a operational axis normal to the flow axis; circular valve seats surrounding the inner ends of the flow passages adjacent the control chamber, said valve seats being disposed in planes perpendicular to a. plane including said flow axis and said operational axis and converging toward the operational axis and being diametrically opposed with respect thereto; a gate assembly including a pair of gate pieces each being identically shaped and having a circular front seating surface inclined parallel to a respective one of the valve seats so as to be sealingly engageable therewith in a closed position, reverse sides of the pieces transverse to the flow axis being in mutually facing spaced relationship and provided each with a counterbore having a cylindrical internal side wall and a circular base wall, the base walls being spaced a predetermined distance apart when the seating surfaces are engaged with the valve seats; a stem supported on the valve body extending into the control chamber and operatively connected to the gate assembly for moving the gate assembly along the operational axis between an open position and the closed position; said gate assembly further including a single rigid circular spacer member received in said counterbores at a location on the gate pieces remote from the stem and having opposed parallel planar end surfaces respectively engaging the base walls of said counterbores thereby determining said spacing apart of said base walls to space the pieces at an overall width which will axially position the gate assembly along the operational axis in the closed position to assure full sealing contact between the seating surfaces and both valve seats, and whereby material removed from the seats and the seating surfaces during repair thereof due to damage and wear can be compensated for by replacement of the original spacer member with a replacement spacer member of increased length sufficient to re-establish said overall width and related axial position for the gate assembly; the internal side walls of the counterbores having a combined depth less than the length of said original spacer member, said side walls bounding the periphery of the spacer member to radially restrain the spacer member in assembly with sufficient clearance therebetween to permit limited relative movement between the pieces without interaction with the spacer member; and guide means preventing separation of the pieces during gate movement which would permit disengagement of the spacer member from the counterbores.

A preferred embodiment of the present invention is now more particularly described with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view of a gate valve having a two piece gate shown in the closed position; Figure 2 is a fragmentary view showing assembly of a seat ring to the valve body and its engagement with a seating surface on the gate disc; Figure 3 is a view taken along line 4X4 of Figure 1, showing tongue and groove guides between the gate and the valve body; Figure 4 is an enlarged fragmentary view taken along line 5-5 of Figure 1, showing a stem head connection at the valve discs; Figure 5 is an enlarged fragmentary perspective view of the stem head in assembly with the valve discs;; Figure 6 is a fragmentary cross-sectional view of the discs spaced by the spacer ring retained by the peripheral surface of counterbores in the discs; and Figure 7 is a view taken along line 10-10 of Figure 9.

Referring to Figure 1, there is shown a gate valve 10 of the type used for high pressure fluid applications such as electric power generation systems of either the fossil or nuclear type. Such a gate valve is usable in a product line ranging between nominal sizes of 1+ inches and 42 inches and in ANSI pressure classes of 600, 900, 1500, 2500 and 4500.

The gate valve 10 generally comprises a valve body 12, a bonnet assembly 14, a yoke assembly 20 and a handwheel assembly 22. As hereinafter described, rotation of the handwheel assembly 22 raises and lowers an internal stem assembly 24 and a double disc gate 26 to open and close a fluid passage extending through the valve body 12 along axis 28 between a left hand outlet 30 and a right hand outlet 32. The direction of flow is dependent on the system and the present equally facilitates flow in either direction.

The valve body 12 is a generally Tshaped cast carbon steel construction and includes outlet sections 33 and 34 and a control section 35 mutually intersecting at a valving chamber occupied by the gate 26. The section 33 includes the aforementioned outlet 30 and a flow passage 36.

The section 34 includes the aforementioned outlet 32 and a flow passage 38. The passages 36 and 38 are co-axially disposed along the flow axis 28. The end of control section 35 defines an upwardly opening cylindrical section 40 having an operational axis 42 which perpendicularly intersects the flow axis 28.

The inner ends of the sections 33 and 34 are formed with counterbores 50 and 52 which contain cylindrical seat rings 54.

The seat rings 54 are provided with hardened annular seats 56 (Figure 3). The seats are formed in planes inclined five degrees with respect to the operational axis 42. The planes of the seats 56 are symmetrically disposed with respect to the axes 42 and 28. The seat rings 54 are fixed to the inner surface of the valve body 12 at continuous circumferential welds 58.

The bonnet assembly 14 is retained at the upper end of the section 40 on the outer end of the section 35 by means of a split retainer ring 60. Bolts 62 clamp an.d ring 60 to draw the outer flange 63 of the bonnet 64 upwardly against the retainer ring retained in a peripheral circumferential channel section 65. The bonnet 64 is centrally apertured and receives the stem 70 of the assembly 24. The handwheel assembly 22 is attached at its outer end to the stem assembly 24 and at its lower end to the gate 26. A packing gland assembly 76 seals the periphery of the stem 70.

The yoke assembly 20 is retained at the top of section 35 by means of a split yoke lock ring 78. A pair of roller bearings 80 and 82 have their outer races received in counterbores at the upper end of the yoke 20 and have their inner races fixedly carried a.t opposite ends of rotatable bushing 84 which has an internal thread engaging the threaded end 86 of the valve stem 70. The bushing 84 is keyed to the handwheel 22 such that rotation of the handwheel 22 rotates the bushing 84 to rise and lower the stem 70 through the packing assembly 76, thereby raising and lowering the gate 26 between the illustrated lowered closed position and a raised opened position as guided by the cooperation between guide tongues formed at the sides of the discs and the grooves between guide rods formed at the sides .of the body (Figure 4).In the open position the gate 26 is housed within a generally hemispherical depression 90 in a lower surface of the bonnet 64 so as to reduce the vertical height of the valve.

The gate 26 comprises two identically formed gate discs 100 and 102. In assembly the discs 100 and 102 have opposed seating surfaces hereinafter described which sealingly engage the seats 56 of the seat rings 54 to prevent migration of fluid past the sealing interfaces. Each disc has a projecting hardened seating surface 104 which is ground flat in a plane inclined with respect to its planar back surface at an angle equal to the inclination of the seat 56 or, in other words, five degrees with respect thereto. The outer diameter of the surface 104 is slightly larger than the surface 56. In initial assembly, the fully seated closed position, the overall thick-ness of the wedge is sized such that the axis 106 of the wedge assembly is located above flow axis 28.As the seating surfaces wear, the axis 106 will shift downwardly and will maintain complete sealing contact until the outer diameter of surface 104 is unacceptably below the outer diameter of seat 56 at the upper center thereof.

An annular spacer ring 120 is located between discs 100 and 102 as detailed below. The spacer ring 120 has a predetermined thickness which, in combination with the thickness of the individual discs, establishes an overall width for gate 26 sufficient to ensure proper seating of the gate discs against the seats. The ring 120 is substantially smaller in diameter than the seating surfaces to increase the deflection of the latter under pressure and stem loading.

Should excessive wear occur at the seating interfaces or should any of the seating surfaces become scored or otherwise damaged during operation, the gate must be removed and the seating surfaces refinished.

Inasmuch as this will result in the removal of metal, there would be excessive downward travel of the gate past the point where sealing contact is established. This would normally necessitate the replacement of the entire gate. In the present instance, however, only the spacer ring 120 must be replaced. The only replacement requirement is that the thickness of the spacer ring compensate for material reduction occasioned by the machining operation so as to re-establish the desired operational relationships between the seating surfaces.

The means for capturing and retaining the spacer ring 120 is shown in detail in Figures 6 and 7. Counterbores 111, are formed coaxial with the axis 106 in the mutually facing reverse sides 110 of the discs 100, 102 having circular base walls 110'. The spacer ring 120 has a predetermined axial length which, in combination with the thickness of the individual discs as measured from the circular base walls 110', establishes an overall width for the. gate sufficient to ensure proper seating of the gate discs against the seats. The cylindrical internal side wall 112' of the counterbore forms an inwardly fa.cing peripheral surface which circumferentially bounds and thereby captures the outer peripheral surface of the spacer ring 120.The diameter of the side wall is slightly larger than the outer diameter of the spacer ring such that the latter is received with a slight radial clearance therewithin. The combined depths of the counterbores is less than the thickness of the spacer ring such that limited relative movement is accommodated without a corresponding interaction. The ring 120 is substantially smaller in diameter than the seating surfaces to increase the deflection of the latter under pressure stem loading.

The lower end of the stem 70 is provided with a T-head construction comprising an actuating collar 130, a cylindrical neck 132 and a T-wedge 134. As shown in Figures 4 and 5, the collar 130 has a substantially frustoconical surface provided with a lower annular bearing surface 136. The T-wedge 134 has outer faces 137 substantially identical in diameter to the outer diameter of the collar 130 and inclined side surfaces 138 symmetrically disposed with respect to the axis 42 to thereby form a downwardly tapering wedge shaped section.

As shown in Figure 4 and 5, the individual discs 102 include an upper bearing surface 140 engageable by the surface 136, a semi-circular axial groove 144 adapted to loosely surround the neck 132 and a wedge shaped transverse slot 146 extending transverse to the axes 106 and 42. The slot is within the confines of the seating areas of the gate, resulting in a lowered profile.

Pairs of raised inclined pads 148 are formed at the sides of the slots 146 and operationally have a slight clearance with respect to the inclined surfaces 138 of wedge 134. In assembled relationship as shown partially in Figure 5, the stem head end is received within the slot 146 and the other half of the gate assembly is received thereover such that the wedge 134 is captured within the confines of the slots 146. The transverse slot design affirmatively retains the stem end and will permit entry thereof to the fluid line in the event of stem fracture.

Due to the wedge shape of the gate 26, the force transmitted by the stem assembly 24 to the seating surfaces is greatly magnified, resulting in a large sealing force between the mating seating surfaces. The independent flexure of the seating surfaces accommodated by the split wedge design allows the individual seating surfaces to flex and conform to the mating surfaces under fluid pressure without a corresponding reaction by the opposite disc. It also substantially equalizes the seating forces on the individual seating surfaces. Accordingly, when it is desired to move the gate assembly to the open position, the upper surface of the T-head 134 engages the undersurfaces of the slot 146 and, inasmuch as the discs are independent, the flexure thereby provided relieves the seating force sufficiently to disengage the seating surfaces.

The gate assembly is translated upwardly through rotation of the handwheel 22 and upward movement of the stem 24 until such time as the conical back seat 130 of the stem 70 engages the back seat 150 on the bonnet 64 the tongue and grooves and the projecting peripheral surfaces preventing axial separation of the discs and providing axial capturing of the spacer ring.

Thereat flow through the passages 36, 34 is substantially unrestricted.

It should be noted that only during the final closing and initial opening movement of the gate is there any mechanical or pressure loaded sliding movement of the seating surfaces across the seats, thereby, resulting in reduced cycle wear to these surfaces.

WHAT WE CLAIM IS: 1. A gate valve comprising a valve body having flow passages communicating with a central valving control chamber; valve seats in the valve body at the ends of the flow passages adjacent the control chamber; a gate assembly movable between an open position and a closed position by an external stem assembly operably connected to said gate, said gate assembly comprising a pair of gate pieces each having a seating surface formed on one side thereof for sealing engagement with a respective valve seat in the closed position when mutually facing surfaces on the reverse sides of the gate pieces are spaced a predetermined distance apart, and a single rigid circular spacer member remote from said stem assembly having end surfaces respectively engaging said mutually facing surfaces and having a thickness therebetween determining said distance apart of said pieces, capturing formations of each of said gate pieces bounding the outer circumferential wall of said spacer member on assembly and projecting from said mutually facing surfaces by an effective combined distance less than the thickness of the spacer member; and guide means preventing separation of the pieces during gate movement which would permit disengagement of the spacer member from the capturing formations.

2. A gate valve as in Claim 1 wherein a central circular opening is formed in the spacer member.

3. A gate valve as in Claim 1 or 2 wherein said capturing formations are the circular side walls of counterbores formed in the reverse sides of the gate pieces and said opposed surfaces are circular bases of said counterbores, said counterbores having a combined depth of less than the thickness of the spacer member.

4. A gate valve comprising a valve body having a pair of flow passages coaxially disposed along the flow axis, said flow passages having inner ends communicating with a central valving control chamber and outer ends connectable into a fluid flow line, said control chamber having a operational axis normal to the flow axis; circular valve seats surrounding the inner ends of the flow passages adjacent the control chamber, said valve seats being disposed in planes perpendicular to a plane including said flow axis and said operational axis and converging toward the operational axis and being diametrically opposed with respect thereto; a gate assembly including a pair of gate pieces each being identically shaped and having a circular front seating surface inclined parallel to a respective one of the valve seats so as to be sealingly engageable therewith in a closed position, reverse sides of the pieces transverse to the flow axis being in mutually facing spaced relationship and provided each with a counterbore having a cylindrical internal side wall and a circular base wall, the base walls being spaced a predetermined distance apart when the seating surfaces are engaged with the valve seats; a stem supported on the valve body extending into the control chamber and operatively connected to the gate assembly for moving the gate assembly along the operational axis between an open position and the closed position; said gate assembly further including a single rigid circular spacer member received in said counterbores at a location on the gate pieces remote from the stem and having opposed

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Figure 5, the stem head end is received within the slot 146 and the other half of the gate assembly is received thereover such that the wedge 134 is captured within the confines of the slots 146. The transverse slot design affirmatively retains the stem end and will permit entry thereof to the fluid line in the event of stem fracture. Due to the wedge shape of the gate 26, the force transmitted by the stem assembly 24 to the seating surfaces is greatly magnified, resulting in a large sealing force between the mating seating surfaces. The independent flexure of the seating surfaces accommodated by the split wedge design allows the individual seating surfaces to flex and conform to the mating surfaces under fluid pressure without a corresponding reaction by the opposite disc. It also substantially equalizes the seating forces on the individual seating surfaces. Accordingly, when it is desired to move the gate assembly to the open position, the upper surface of the T-head 134 engages the undersurfaces of the slot 146 and, inasmuch as the discs are independent, the flexure thereby provided relieves the seating force sufficiently to disengage the seating surfaces. The gate assembly is translated upwardly through rotation of the handwheel 22 and upward movement of the stem 24 until such time as the conical back seat 130 of the stem 70 engages the back seat 150 on the bonnet 64 the tongue and grooves and the projecting peripheral surfaces preventing axial separation of the discs and providing axial capturing of the spacer ring. Thereat flow through the passages 36, 34 is substantially unrestricted. It should be noted that only during the final closing and initial opening movement of the gate is there any mechanical or pressure loaded sliding movement of the seating surfaces across the seats, thereby, resulting in reduced cycle wear to these surfaces. WHAT WE CLAIM IS:

1. A gate valve comprising a valve body having flow passages communicating with a central valving control chamber; valve seats in the valve body at the ends of the flow passages adjacent the control chamber; a gate assembly movable between an open position and a closed position by an external stem assembly operably connected to said gate, said gate assembly comprising a pair of gate pieces each having a seating surface formed on one side thereof for sealing engagement with a respective valve seat in the closed position when mutually facing surfaces on the reverse sides of the gate pieces are spaced a predetermined distance apart, and a single rigid circular spacer member remote from said stem assembly having end surfaces respectively engaging said mutually facing surfaces and having a thickness therebetween determining said distance apart of said pieces, capturing formations of each of said gate pieces bounding the outer circumferential wall of said spacer member on assembly and projecting from said mutually facing surfaces by an effective combined distance less than the thickness of the spacer member; and guide means preventing separation of the pieces during gate movement which would permit disengagement of the spacer member from the capturing formations.

parallel planar end surfaces respectively engaging the base walls of said counterbores thereby determining said spacing apart of said base walls to space the pieces at an overall width which will axially position the gate assembly along the operational axis in the closed position to assure full sealing contact between the seating surfaces and both valve seats, and whereby material removed from the seats and the seating surfaces during repair thereof due to damage and wear can be compensated for by replacement of the original spacer member with a replacement spacer member of increased length sufficient to reestablish said overall width and related axial position for the gate assembly; the internal side walls of the counterbores having a combined depth less than the length of said original spacer member, said side walls bounding the periphery of the spacer member to radially restrain the spacer member in assembly with sufficient clearance therebetween to permit limited relative movement between the pieces without interaction with the spacer member; and guide means preventing separation of the pieces during gate movement which would permit disengagement of the spacer member from the counterbores.

5. A gate valve as in Claim 4 wherein said spacer member is an annular ring with a central circular opening.

6. A gate valve as in Claim 4 or 5 wherein the spacer member is of substantially smaller diameter than the seating surfaces of the gate pieces to increase the flexibility in assembly of said pieces.

7. A gate valve substantially as hereinbefore described with reference to and as shown in the accompanying drawings.