Field of the invention:

The present invention generally relates to valves used for directing and controlling flow of fluids and more particularly, to an in-situ spring loaded seat replacement device used for in-line maintenance of a spring loaded slab gate valve.

Background of the invention:

A valve is a mechanical device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids) by opening, closing, or partially obstructing the inlet and outlet ports. All valves are designed to allow/ stop the flow of a fluid through a pipeline. The slab gate valves are commonly used in natural gas and oil industry. The slab gate valves have two sealing faces perpendicular to the pipeline axis and its closing member is a single gate.

The slab gate valve includes a valve body and a gate (obturator) which moves in a plane which is perpendicular to the direction of flow. Reciprocating motion of the gate from a first closed position to a second open position allows for fluid to flow through the valve by aligning central passage of the gate with an inlet and an outlet of the valve. The gate is fitted between the two spring loaded seats which provide sealing on both sides, regardless of upstream or downstream pressure conditions.

The main purpose of the spring loaded seat is to provide low pressure sealing. The spring forces the resilient seals mounted on seat on the gate. When the line pressure increases, contact load between the seat and the slab gate increases which helps sealing. At present, replacement of the spring loaded seats needs valve to be removed from the pipeline and also it is difficult to create sufficient force to press the seat into a body cavity manually. This incurs heavy cost in plant shut down for many hours, usage of manpower and heavy material handling equipments.

Accordingly, there exists a need to design a seat replacement device to aid in line replacement of seat without removal of a valve from a pipeline thereby overcoming the drawbacks of the prior arts.

Objects of the invention:

An object of the present invention is to remove old seats from a valve body and replace with new seats without removing the valve from a pipeline.

Another object of present invention is to reduce inline service maintenance cost.

Summary of the invention:

Accordingly, the present invention provides an in- situ spring loaded seat replacement device (hereinafter, “device”) for a slab gate valve. The device comprises a seat guide plate, a fixture stem, a shaft guide plate, a seat removal mechanism, a top plate and a hand wheel.

The seat guide plate holds the spring loaded seats. The seat guide plate includes at least four guide pins configured thereon. The guide pins hold a bore of the spring loaded seats and the seat guide plate presses the spring loaded seats into a seat cavity during a seat insertion. The spring loaded seats are held in a body of the slab gate valve using seat holding pins. The fixture stem includes an upper link bush, a lower link bush and a stem groove. The upper link bush and the lower link bush are fixed on the fixture stem and connected to a pair of links. The pair of links guides the seat guide plate. The stem groove is provided on the fixture stem. The stem groove includes a stem collar located thereon. The shaft guide plate is fixed to the fixture stem through the stem collar for providing support to the spring loaded seats from a back side. The shaft guide plate includes at least four resting pads configured thereon. The seat removal mechanism is attached on the seat guide plate. The seat removal mechanism includes a seat puller, a puller spring bracket, a grub screw and a spring. The seat puller is placed in the puller spring bracket using the spring and a pin. The grub screw is provided in the puller spring bracket to adjust position of the seat puller at the time of the seat insertion. The spring loaded seats have an enlarged outside diameter that includes a groove accommodated thereon to be used for holding by the seat puller, and a chamfer provided thereon for facilitating the smooth travel of the seat puller over the spring loaded seats during the operation. The grub screw is loosened for removing the spring loaded seats from the slab gate valve. The top plate guides the fixture stem in a vertical axis with the help of a lock nut system. The top plate includes a pair of locating pins configured on a bottom surface thereof and a pair of eye nuts configured on a top surface thereof. The pair of locating pins facilitates resting of the top plate on an upper surface of the body during any one of the seat insertion and a seat removal. The hand wheel is positioned on one end of the fixture stem for applying torque. The hand wheel rotates in a clockwise direction and an anticlockwise direction during the seat insertion and the seat removal.

In accordance with the present invention, during removal of the spring loaded seats, the rotation of the hand wheel in the clockwise direction causes expansion of the pair of links that results in sliding of the seat puller over the taper surface of the spring loaded seats and locking of the seat puller in the groove of the spring loaded seats due to force of the spring thereafter the seats are removed by rotating the hand wheel in the anticlockwise direction. Specifically, for removing a first spring loaded seat from one side of the slab gate valve, the resting pads are removed from the shaft guide plate and for removing a second spring loaded seat from another side of the slab gate valve, the resting pads are fixed on the shaft guide plate. In accordance with the present invention, during insertion and pressing of the first spring loaded seat, the resting pads of the shaft guide plate rests on the face of a body pocket and during insertion and pressing of the second spring loaded seat, the shaft guide plate directly rests on the other side of seat surface.

Brief description of the drawings:

The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein Figures la- lb show a cut section of a slab gate valve assembly, in accordance with the present invention;

Figure lc shows a spring loaded seat, in accordance with the present invention;

Figure 2 shows an isometric view of an in-situ spring loaded seat replacement device with the spring loaded seat, in accordance with the present invention;

Figure 3a- 3b show a front view and a side view of the in-situ spring loaded seat replacement device, in accordance with the present invention;

Figure 3c shows a detail view of a seat removal mechanism attached on a seat guide plate of the in-situ spring loaded seat replacement device, in accordance with the present invention;

Figure 4 shows a sectional view of a valve body while replacing the spring loaded seat, in accordance with the present invention; and

Figures 5a- 5b show an isometric view and a sectional view of the body after inserting seat holding pins for holding the spring loaded seats, in accordance with the present invention. Detailed description of the invention:

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides an in-situ spring loaded seat replacement device. The seat replacement device is used for in line maintenance of a slab gate valve. Specifically, the seat replacement device is used to remove spring loaded seats from the valve in service and replace with new seats. After mounting new seats in a seat pocket using the seat replacement device, the seat position is held by two seat holding pins and holding pins are withdrawn after a slab gate is inserted into a body of the valve.

This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description as well as in a table given below. Table:

Referring to figures la- lb, a slab gate valve (50) (hereinafter, “valve (50)”) in accordance with the present invention is shown. The valve (50) includes a body (2), a bonnet (4), spring loaded seats (6), a stem (8), a slab gate (10), a gate guide (12), a nut (14), a stud (16), a yoke (18), an adaptor flange with bevel gear operator (20) (hereinafter, “adaptor flange with BGO (20)”) and an actuator (22) as shown in figures la- lb.

Figure lc shows the spring loaded seat (6) in accordance with the present invention. In an embodiment, the valve (50) includes a first seat (6) mounted internally on one side thereof and a second seat (6) mounted internally on another side thereof. Specifically, each seat (6) includes a chamfer (not shown) provided on an outside diameter thereof and the outside diameter of each seat (6) is enlarged to accommodate a groove (not shown) thereon.

Referring now to figures 2a- 5b, an in-situ spring loaded seat replacement device (hereinafter, “device (100)”) for the valve (50) in accordance with the present invention is shown. The device (100) comprises a seat guide plate (54), a fixture stem (64), a shaft guide plate (68), a seat removal mechanism (78), a top plate (84) and a hand wheel (88).

The seat guide plate (54) is used for holding the spring loaded seats (6). In an embodiment, the seat guide plate (54) includes at least four guide pins (52) configured thereon. However, it is understood here that the seat guide plate (54) may include any number of guiding pins (52) in other alternative embodiments of the present invention. The guide pins (52) hold the bore of the seat (6). The seat (6) is held in the body (2) of the valve (50) using seat holding pins (90). The fixture stem (64) includes an upper link bush (56), a lower link bush (58) and a stem groove (not shown). The upper link bush (56) and the lower link bush (58) are fixed on the fixture stem (64) and connected to a pair of links (60). The pair of links (60) guides the seat guide plate (54). The stem groove includes a stem collar (62) located thereon.

The shaft guide plate (68) is fixed to the fixture stem (64) through the stem collar (62). The stem collar (62) guides the shaft guide plate (68). The shaft guide plate (68) rests such as the center of the shaft guide plate (68) coincides with the center of a valve bore. The shaft guide plate (68) is used to provide support to the seat (6) from a back side. In an embodiment, the shaft guide plate (68) includes at least four resting pads (66) configured thereon. However, it is understood here that the shaft guide plate (68) may include any number of resting pads (66) in other alternative embodiments of the present invention. The resting pads (66) act as a stopper to provide the spring force in opposite direction at the time of first side seat insertion.

As shown in figure 3c, the seat removal mechanism (78) is attached on the seat guide plate (54) which guides the mechanism during insertion and removal of the seats (6). The seat removal mechanism (78) includes a seat puller (70), a puller spring bracket (72), a spring (74) and a grub screw (76). The seat puller (70) is placed in the puller spring bracket (72) with the help of the spring (74) and a pin (75). Specifically, the spring (74) is a compression spring. The seat puller (70) helps to pull the seat (6) from the valve assembly during removal. The groove on the outside diameter of the seat (6) is held by the seat puller (70) and the chamfer facilitates the smooth travel of the seat puller (70) over the seat (6) during the operation. The grub screw (76) is provided in the puller spring bracket (72) to adjust position of the seat puller (70) by means of an alien screw (not shown) at the time of a seat insertion. The grub screw (76) is loosened for removing the seats (6) from the valve (50). The top plate (84) guides the fixture stem (64) in a vertical axis with the help of a lock nut system (86). The top plate (84) includes a pair of locating pins (80) configured on a bottom surface thereof and a pair of eye nuts (82) configured on a top surface thereof. The pair of eye nuts (82) is used for pulling the device (100) from the valve (50). The top plate (84) rests on an upper face of the body (2) through the pair of locating pins (80). The hand wheel (88) is positioned on one end of the fixture stem (64) and is used for applying torque. The hand wheel (88) rotates in a clockwise direction and an anticlockwise direction during the seat insertion and the seat removal.

Again referring to figures la to 5b, a procedure for removal of the seats (6) from the valve (50) is described herewith. While disassembly of the first seat (6), the actuator (22), the adapter flange with BGO (20), the yoke (18) and the bonnet (4) are removed from the body (2) of the valve (50). Then, the slab gate (10) and the valve stem (8) are removed from the body (2) followed by removal of the gate guide (12).

For removing the first seat (6), the resting pads (66) are removed from the shaft guide plate (68) and the grub screw (76) of the seat removal mechanism (78) is loosened prior to insertion of the device (100). Then, the device (100) is inserted into the body (2) from an upper side. The top plate (84) is rested on an upper surface of the body (2) through the pair of locating pins (80). The shaft guide plate (68) is directly rested on one seat (6) and the seat guide plate (54) is moved to another seat (6) by rotating the hand wheel (88) in the clockwise direction that causes expansion of the pair of links (60) that results in sliding of the seat puller (70) over the taper surface of the seat (6) and due to force of the spring (74), the seat puller (70) locks in the groove provided on the seat (6) as shown in figure 3c. After locking, the first seat (6) is removed by rotating the hand wheel (88) in the anticlockwise direction. The device (100) is removed from the body (2) and the grub screw (78) of the seat removal mechanism (78) is tightened for removing the first seat (6) from the device (100). Then the resting pads (66) are fixed on the shaft guide plate (68) of the device (100) and same procedure as mentioned above is followed for removing the second seat (6) except this time the resting pads (66) of the shaft guide plate (68) are rest on the face of a body pocket. The device (100) is removed from the body (2) of the valve (50) and the second seat (6) is removed from the device (100).

Again, referring to figures la to 5b, a procedure for pressing of the seats (6) into the valve (50) is described herewith. For pressing the first seat (6), the grub screw (76) of the seat removal mechanism (78) is tightened to lock the seat puller (70) to avoid contact of the seat puller (70) with the seat (6) while pressing of the seats (6). A bore (not numbered) of the first seat (6) is located on the guide pins (52) that are provided on the seat guide plate (54). The device (100) with the new seat (6) is inserted into the body (2) and the top plate (84) of the device (100) rests on the upper surface of the body (2) through the pair of locating pins (80). The resting pads (66) of the shaft guide plate (68) rests on the face of the body pocket. The seat guide plate (54) presses the first seat (6) into a seat cavity where all springs are in a compressed condition with zero clearance between a seat face and a body face by rotating the hand wheel (88) in the clockwise direction. The seat holding pins (90) are inserted into the body (2) for holding the seat (6) as shown in figures 5a- 5b. The device (100) is then removed from the body (2) and the resting pads (66) are removed from the shaft guide plate (68).

Again, above mentioned procedure for pressing of the first seat (6) into the valve (50) is followed for inserting the second seat (6) except this time the shaft guide plate (68) directly rests on the other side of seat (6) surface. The seat holding pins (90) are inserted into the body (2) for holding the second seat (6) as described in figures 5a- 5b. The device (100) is then removed from the body (2). After placing the seats (6) on both sides of the valve (50), the gate guides (12) are inserted and the seat holding pins (90) are withdrawn after the slab gate (10) is inserted into the body (2) which allows the seats (6) to seal against the gate surface. Advantages of invention:

1. The device (100) helps to remove old seats from the body (2) of the valve (50) and replace with new seats without removing the valve (50) from the pipeline thereby reducing inline service maintenance cost.

2. The seat removal mechanism (78) allows the seat puller (70) to lock in the groove provided on the seat diameter due to spring force that helps in removal of the seats (6).

3. The spring loaded seat position is held by two seat holding pins (90) after removal of the device (100). The seat holding pins (90) are withdrawn after inserting the slab gate (10) into the body (2) that does not affect the seat seal surface.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.