GB2188709A - Fire-safe ball valve - Google Patents

Abstract

A top entry ball valve, for gas and oil wells and chemical plants, has a fire safe sealing assembly comprising, on each side of the ball 12, first and second tubular parts 40, 42 threaded together at 44, an outer spring urged (60) ring 52, a spring-holding ring 64, an annular spacer 68 segmented to permit top entry, and an annular spring urged (84) element 78, these elements housing sealing rings 50, 76, 102, spacers 104, 106 and a heat-resistant mass 108. During a fire, elements 50, 76, 102, 104, 106 are destroyed, spherical surface 57 of part 40 moves into sealing contact with the ball 12, and element 78 is thrust towards the ball and compresses mass 108 to form a seal. <IMAGE>

Description

SPECIFICATION Improved fluid-control ball valve with device to ensure tightness in case of fire The present invention relates to fluid control valves of the so-called ball type made up of an external body housing a moving part or plug essentially spherical in shape.

When said valves are employed for controlling fluids highly contaminated by solid particles or corrosive substances it is necessary, every now and then, to remove the plug from the valve body for maintenance or repair, especially for replacement of the worn gask efts; The removal can be done in two directions, one parallel to the longitudinal axis of the valve body and the other perpendicular to said axis, necessitating two basic types of valves termed by those skilled ir the art 'side entry' valves and 'top entry' valves.

In particular the present invention relates to a improved 'top entry' ball valve containing a device to provide tightness of said valve in case of destruction of gaskets due to overheating as from a fire.

Ball valves are widely used in many fiuidcontrol applications, even dangerous ones such as with corrosive or inflammable fluids present in chemical plants, petroleum product extraction facilities such as natural gas wells, crude petroleum wells etc., and especially wells in particular environments such as offshore wells.

It is known that petroleum products issuing from wells are contaminated by several foreign substances possibly including solid abrasive substances such as sand and scale from the storage rock containing them, corrosive liquid substances such as sea water or brackish water, and even gaseous substances such as hydrogen sulfide (H2S) and carbon dioxide (CO2) which singly or combined with other substances can have quite harmful effects on the piping and valves which convey and control them.

As a consequence of this fact it is sought to eliminate said contaminants at a place the closest the possible to the extraction well to limit as far as possible the use of materials having high resistance to abrasion and corrosion and hence being particularly costly. For this reason in the immediate proximity of extraction wells there is installed equipment performing a first decontamination of extracted products and in particular separation of the abovementioned gaseous contaminants from the natural gas or petroleum.

With offshore wells served by platforms said decontamination equipment is usually installed thereon and since said platforms are densely occupied by service and control personnel all decontaminating installations and their components must meet severe safety requirements.

One of the safety requirements which the components of said installations and in particular the ball valves, which are the subject matter of the present invention, must meet is the ability to maintain enough tightness to provide the closing function in case of overheating due for example to fires which result in destruction of heat-sensitive gaskets. Said ability is known to those skilled in the art by the term 'fire safe'.

There is already a fire safe system for ball valves of the type having a plug insertable or removable along the direction of the longitudinal axis of the valve body commonly termed 'side entry' by those skilled in the art. Said system provides sufficient tightness between the plug and the ball valve body when the soft gaskets placed between the plug and the valve seats housed in the body disappear, transferring said tightness by the action of springs placed between the body and the seats from said gaskets to special surfaces shaped complementarily to the valve plug and appropriately finished to provide said tightness. However said fire safe system cannot be transferred directly to top entry valves because a direct engagement of springs between the seats and valve body would not provide sufficient shifting of the seats to permit removal of the plug from the valves.

The object of the present invention is therefore to provide sufficient tightness to a top entry valve then overheating from fire causes complete destruction of the soft gaskets engaged between plug and seats, employing seats of an original type which can shift sufficiently when for any reason it is necessary to remove the plug from the valve body and which will be described below in the description of the present invention.

Briefly, the seats in accordance with the present invention consist of a first tubular cylindrical piece facing said ball plug having at a first end a flange protruding outward and bearing on its end face facing toward said ball plug a groove designed to house an elastic gasket, said flange being surrounded by an annular ring or outer seat-ring having an inside diameter virtually equal to the outside diameter of the flange and having a recessed edge resting against said flange and a bevel forming a surface complementary to the spherical surface of the valve plug, said ring being pushed by springs housed in a second ring or spring holding ring which rests by means of a removable insert against the valve body, said cylinder being finished at its said first end in accordance with a portion of a concave spherical surface complementary to the spherical surface of the valve plug and prolonging the surface of the ring bevel, said first tubular cylindrical piece being extended in a body ending in a tightness gasket seat and subsequent shoulder producing an edge of smaller diameter at the second end of said tubular cylindrical piece to house a packing of heat resistant material and having at said second end an internal threading designed to receive a first threaded end of a second tubular cylindrical piece of outside diameter virtually smaller than that of the first cylindrical piece and inside diameter virtually equal to that of said first piece, said second cylindrical piece having at its second end a support flange for springs designed to push an annular thrust element sliding around said second tubular cylindrical piece having an outside diameter virtually equal to that of the first cylindrical piece and having a protuberance complementary to the shoulder of said first cylindrical piece housing said packing of heat resistant material while an annular spacer having an inside diameter virtually equal to the outside diameter of said second tubular cylindrical piece remains between the second end of said first cylindrical piece and the annular thrust element for the purpose of holding the protuberance of said annular element away from said packing of heat-resistant material, said spacer being made of a material which yields under and is easily destroyed by overheating.

In a preferred embodiment of the present invention the outer seat ring surrounding the outward protruding flange is provided with a locking shaft which, being placed between said ring and the rear of the flange, makes said ring integral with said flange to allow the springs which push the ring to entrain the first cylindrical tubular piece also, providing thrust of the seat against the ball plug.

In a second preferred embodiment of the present invention the removable insert which permits resting of the spring holding ring on the valve body is made up of an annular spacer divided in concatenated segments by some kind of releasable restraint so that it is sufficient to remove one segment to permit removal of all the segments.

According to another preferred embodiment of the present invention the second tubular cylindrical piece ends in another section with lowered outside diameter designed to fit in a corresponding guide seat machined in the valve body to permit withdrawal of the two tubular pieces united during withdrawal of the valve plug.

The advantages and characteristics of the present invention will be better understood from the following detailed description of an example thereof accompanied by the annexed drawings wherein: FIG. 1 shows a cross section of a top-entry ball valve containing the device providing tightness in case of fire in accordance with the present invention, FIG. 2 shows an enlarged cross section of the detail of said tightness device of the present invention illustrating how the valve plug can be removed from above or perpendicularly to the longitudinal axis of the valve body while providing tightness in case of fire.

With reference to the figures a top-entry ball valve is made up of a hollow body 10 in which there turns a ball plug 12 having a through hole 14 and being moved by a shaft 16 passing through a flange 18 fixed to the body 10 by appropriate means such as bolts 20 and being supported at the end opposite that of said shaft 16 by means of a journal 22 in a seat 24 of a ciosed bottom 26 of said valve body 10. Said valve body 10 is also fitted with means for fixing it to pipes such as the flanges 30 and 32 having through holes 34, 35, 36 and 37 to house members such as nuts and/or bolts to provide said fixing.

Tightness between the valve body 10 and the ball plug 12 is provided by two seats 38 and 39 which rest against the plug 12 by means of spherical surfaces complementary to the spherical surfaces of the ball 12.

As can be better seen in FIG. 2 which shows an enlarged partial cross section of the particular cooperation between the valve body 10, ball valve 12 and seat 39 said seat 39 is made up of a first tubular part resting against the ball plug 12 united with a second tubular part 42 by means of an internal threading 44 engaging in a corresponding threading on said second part 42. The first tubular part 40 has at the first end near the ball plug 12 an outward turned flange 46 having a groove 48 designed to house a soft gasket 50 and adjacent to a spherical surface 57 complementary to the spherical surface of the plug 12. Said flange 46 is surrounded by an external seat ring 52 having in it an inward turned step 54 ending in a spherical surface portion 56 complementary to the spherical surface of the plug 12.Said external seat ring 52 rests against the outward turned flange 46 which is made integral with the first tubular part of the seat 40 by a locking ring 55 optionally held steady by an elastic pin 58 passing through said external seat ring 52.

Said outer seat-ring 52 is pushed against the ball plug by a set of springs 60 spaced regularly around its circumference and contained in special seats 62 of a spring holding ring 64 having a flange 66 protruding externally which engages an annular spacer 68 resting against the valve body 10. Said annular spacer 68 is preferably made up of segments connectable together by means of releasable restraints to fulfill a purpose illustrated below. The annular spacer 68 rests against a first stepped recess 70 in the body 10 so as to permit the spring holding ring 64 to apply the thrust of the springs 60 to the external seat ring 52 and then, by means of the locking ring 55, to the first tubular seatpart 40 so that the walls of the groove 48 can push the soft gasket 50 against the ball plug 12, providing tightness between seat and plug.Behind the spring holding ring 64 there is a second stepped recess 72 in the valve body 10 having a function illustrated below.

A recess 74 with a rectangular cross section on the first tubular seat-part 40 houses an O-ring 76 which provides tightness between the first seat part 40 and the valve body 10.

The second tubular seat-part 42 has an inside diameter equal to that of the first seat part 40 and an outside diameter in its first portion nearer to the first seat part 40 decidedly smaller than that of said first part so as to permit sliding thereon of an annular element 78 having a protruding front edge 80 complementary to a stepped lowering 82 in the rear zone of the first tubular seat-part 40. Said annular element 78 rests agaist thrust springs 84 arranged regularly around the circumference thereof and rested in a spring seat 86 born by a flange 88 protruding externally from the second tubular seat-part 42. Finally the second seat part 42 ends in a lowered zone 90 designed to fit in a slight stepped recess 92 made in the valve body 10 and ending in a bevel 94.Behind the flange 88 there is a stepped recess 96 made in the body 10 while behind the annular element 78 there is another stepped recess 96 also made in the valve body 10.

In the annular element 78 is made a recess 100 with a rectangular cross section housing an O-ring 102 which provides tightness between said annular element 78 and the valve body 10. Said annular element 78 is kept spaced from the bottom face of the first tubular seat-part 40 by a spacer 104 made of material which becomes yielding or volatilizes at high temperature.

The stepped lowering 82 of the first seatpart 40 is tapered so that its height decreases from the outside toward the inside and houses a heat-sensitive element 106 which yields or volatilizes at high temperature and has a heat-resistant tow seal made of felt or graphite braid outside to fulfill a sealing function iilustrated below.

To understand the operation of the present invention reference is made to FIG. 2 in which it is clearly seen that the seat 39 is held between the first stepped recess 70 of the valve body 10 against which it rests by means of the segmented annular spacer 68 and the ball plug 12 against which it usually rests by means of the soft gasket 50.

Removal of the ball plug 12 is made possible by the annular spacer 68 so that, being divided in mutually restrained segments and one of said segments being designed to be readily removed from the first stepped recess 70, removal of the spacer 68 permits the outer flange 66 of the spring holding ring 64 to be shifted back to the bottom of the stepped recess 70. Consequently all parts of the seat 39 shift into the corresponding stepped recesses so that the entire seat withdraws from the ball plug 12 and ir particular the spherical surfaces 56 and 57 of the seat withdraw from the plug 12 to allow it to be freely removed perpendicularly to the longitudinal axis of the body 10, thus realizing the top entry feature of the valve of the present invention.

The device providing tightness in case of overheating and/or fire works in the following manner.

Overheating due to fire causes melting and then volatilization of all parts made of heatsensitive material and in particular the soft gasket 50, the first O-ring 76, the second 0ring 102 of the spacer 104 and the heatsensitive element 106. Volatilization of the soft gasket 50 which keeps the spherical surface 57 of the first tubular seat-part 40 away from the spherical surface of the plug 12 allows said surface 57 to rest against the surface of the plug 12, transferring there the sealing function of the gasket, now volatilized at the two spherical surfaces which, being finished with a certain degree of precision, provide sufficient tightness to meet safety regulations albeit at the cost of a certain increase in friction due to contact between extended spherical surfaces.

Volatilization of the O-ring 76 causes loss of tightness between the seat 40 and the valve body 10 but simultaneous volatilization of the spacer 104 permits the annular element 78 pushed by the springs 84 to advance its protruding edge 80 which penetrates into the stepped lowering 82 of the first tubular seatpart 40 by pushing the heat-resistant seal 108 into the narrow space left free by the heatsenstive element 106, which has also volatilized, and, said heat-resistant element 108 being made up of a fibrous mass such as felt or graphite braid, it is compressed in said restricted space, providing between the seat 39 and the valve body 10 sufficient tightness to meet safety regulations.

Removal of the segmented annular spacer 68 permits removal of, in addition to the ball plug 1 2 in the top-entry manner, the seats 38 and 39 from their housing in the valve body 10 for maintenance and/or repair, especially after a fire has destroyed all the heat-sensitive parts of the valve.

Indeed, looking at the seat 39 shown in FIG.2 it is seem that, once removed from the valve body 10,it can be disassembled in all its component parts because the rear cylindrical part 42 of the seat unscrews from the front part, permitting sliding out of the annular element 78 for cleaning, and at the same time allows access to the stepped lowering 82 for removal of residue of the heat-sensitive element 106 and the tow sealing element 108, which is compressed by the protruding edge of the annular element 78. In addition the spring holding ring 64 can be pulled out at the rear from the first tubular part 40 of the seat 39 while removal of the locking ring 55 permits front removal of the outer seat-ring 52.

After cleaning of all the disassembled component parts all the heat-sensitive elements, i.e. the soft gasket 50, the O-ring 76, the spacer element 106 and the heat-resistant seal 108, they are replaced in their seats. The O-ring 102 is also replaced in the recess with rectangular cross section 100 of the annular element 78, which is fitted on the second tubular part 42 of the seat 39. Finally the spacer 104 is placed in front of the annular element 78 and the second cylindrical part 42 is screwed into the first cylindrical part 40 so that said spacer 104 is pushed against the annular element 78 to compress the thrust springs 84 and hold the protruding edge 80 away from the seal 108. Upon completion of this last operation the seat 39 is entirely reassembled and ready to be placed in the valve body 10.

Once the seats 38 and 39 have been replaced in the valve body 10 the ball plug 12 is replaced between the two seats and, reinserting the segmented annular spacers 68 between the seats 38 and 39 and the valve body 10, said seats are pushed against the ball plug 12 where they rest by means of their soft gaskets 50, thus completing assembly of the valve.

The above description of an embodiment of the invention is given as an example and fully or partially equivalent solutions can obviously occur to those skilled in the art from reading of the present description.

It is accordingly intended to cover all of said fully or partially equivalent solutions.

Claims (5)

1. Improved fluid-control ball valve made up of an outer body housing a virtually spherical plug against which there rest housed in said outer body two seats of the type with plug removal in a direction virtually perpendicular to the direction of the longitudinal axis of said valve body and having a device providing sufficient tightness in case of overheating as from a fire characterized in that said seats consist of a first tubular cylindrical piece facing said ball plug and having a first end of a flange protruding outward and bearing on the outer face facing said ball plug a groove designed to house an elastic gasket, said flange being surrounded by an annular ring or outer seat-ring having an inside diameter virtually equal to the outside diameter of the flange and having a recessed edge resting against said flange and a bevel forming a surface complementary to the spherical surface of the valve plug, said ring being pushed by springs housed in a second ring or spring holding ring which rests by means of a removable insert against the valve body, said cylinder being described at said first end by a portion of concave spherical surface complementary to the spherical surface of the valve plug and continuing the surface of the bevel of the ring, said first tubular cylindrical part extending in a body ending in a gasket seat and in a subsequent shoulder producing an edge of smaller diameter in the second end of said tubular cylindrical piece to house a packing of heatresistant material and having at said second end an internal threading designed to house a first threaded end of a second tubular cylindrical piece of an outside diameter virtually smaller than that of the first cylindrical piece and inside diameter virtually equal to that of said first piece, said second cylindrical piece having at its second end a supporting flange for springs designed to push an annular thrust element sliding around said second tubular cylindrical piece and having an outside diameter virtually equal to that of the first cylindrical piece and a protruberance complementary to the shoulder of said first cylindrical piece housing said packing of heat-resistant material while an annular spacer having an inside diameter virtually equal to the outside diameter of said second tubular cylindrical piece stays between the second end of said first cylindrical piece and said annular thrust element to hold the protruberance of said annular element away from said packing of said heatresistant material, said spacer being made of a material which yields under and is easily destroyed by overheating, allowing said thrust element to compress with its protruberance said packing of heat-resistant material.

2. Improved ball valve in accordance with claim 1 characterized in that the outer seatring surrounding the outward protruding flange has a locking ring which, being placed between said ring and the rear of the flange, makes said ring integral with said flange, allowing the springs which push the outer seatring to also entrain the rest of the seat to provide continuous thrust of the seat against the ball plug.

3. Improved ball valve in accordance with claim 1 characterized in that the removable insert which allows resting of the spring holding ring on the valve body is made up of an annular spacer divided in segments concatenated by some kind of releasable restraint so that it is sufficient to remove a single segment to permit subsequent removal of all the other segments.

4. Improved ball valve in accordance with claim 1 characterized in that the second tubular cylindrical piece ends in a last section with Lowered outside diameter designed to fit in a corresponding guide seat machined in the valve body and designed to allow withdrawal of the two tubular pieces united during removal of the valve plug.

5. A ball valve substantially as hereinbefore described with reference to the accompanying drawings.