NO20171559A1

NO20171559A1 - Metal - to metal sealing valve

Info

Publication number: NO20171559A1
Application number: NO20171559A
Authority: NO
Inventors: Jan Erik Skjold
Original assignee: Icon Instr As
Priority date: 2017-10-02
Filing date: 2017-10-02
Publication date: 2019-04-03
Also published as: NO344697B1

Description

The invention relates to a valve providing metal - to metal sealing both in its open and its closed position, sealing a pressurised fluid led to the valve, or sealing a pressurised fluid flowing through the valve, from the surrounding environment.

More specifically it relates to a valve, which due to its metal to - metal sealing in both its open and its closed position is particularly well suited for use within areas where the valve may be exposed to excessive pressures/ temperature without loss of sealing function.

Such areas may for example be the immediate surroundings of a wellhead or a christmas tree such as found in the oil and gas production industry. However this shall not be limiting as there may be numerous other areas and applications where a process professional will find that such a valve providing metal – to metal sealing in both operational positions is desirable.

In general according to industry practice and several national and international regulations, codes and standards there is a need for isolation valves in instrumented systems.

Such valves are required such that an instrument, typically a pressure measuring instrument, may be disconnected without affecting the process it is connected to. There are several different types of instrument valves on the market and several different methods of arranging such valves with an instrument such as a block, a block and bleed, double block and bleed etc.

The needle valve illustrated in Figure 7 is typical for such a valve and represents prior art referred in order to explain the drawbacks and limitations of current art.

In an example the valve (20) is located on a petroleum production tree which is surrounded by a liquid pool fire producing core temperatures in the range of 500 °C to 1000 °C, temperatures at which synthetic gaskets/ packers break down.

In the example the valve (20) inlet port (P1) is connected to a christmas tree producing outlet line carrying pressurized flammable fluids. Fluids shall be understood to include both liquids and gases.

In the valve body (21) there are several bores; a fluid inlet (P1) bore perpendicular to the axis (Y); a fluid outlet (P2) bore perpendicular to the axis (Y); and a bore (B) coincident with the axis (Y) accommodating the needle (22) and associated devices used for opening and closing the fluid passage connecting the two bores (P1) and (P2).

When closing the valve the crown nut (27) is turned clockwise and the needle (22) is pushed downward such that the needle (22) tip closes the fluid passage connecting the inlet (P1) with the cavity (C) and outlet (P2). See Figure 6a.

Often the angle of the opposing sealing surfaces differs slightly thereby concentrating the closing, or sealing force on a very small surface allowing some mechanical deformation. Even though the surface-roughness tolerances of the sealing areas are very small, typically in the region of 1/1000 – 1/100 mm, slight mechanical deformation ensures that no leakage paths caused by excessive roughness of the sealing surfaces remain, thereby providing a gas tight seal able to withstand very high pressure (typically > 1000 MPa). Typically the needle (22) tip will be conical with a slope of 60° relative to the axis (Y) and the opposing sealing surface will also be conical with a slope less than the tip ensuring that the tip will cut into the edge of the sealing surface.

Opening the valve (20) the crown nut (27) is turned counter-clockwise and the needle (22) is pulled upwards such that the needle (22) tip opens the fluid passage connecting the inlet (P1) with the cavity (C) and the outlet (P2).

While the valve (20) is in its open position (Figure 7b) and fluid is flowing freely from the inlet (P1) to the outlet (P2) the pressurised fluid in the cavity (C) is held from escaping through the bore (B) passage to the surrounding environment (E) - by the needle (22), the bore (B) walls and the packers (231) and (232) sealing the annulus formed between the needle (22) and the bore (B) walls. See Figure 6b.

The packers are typically made from synthetic materials such as PEEK, PTFE or NBR, which are subject to unacceptable mechanical degradation at temperatures above 350 °C such as may be found in a typical hydrocarbon pool fire which may rise up to 1000 – 1100 °C within five minutes of ignition.

By turning the crown (25) clockwise the squash plate (24) exerts force on the packers (231) and (232) leading to mechanical compression and elongation of the packers (231) and (232) thus forming a tighter seal resilient to higher pressure.

The washers (28) and (26) are low friction material ensuring that the crown nut (27) rotates freely unaffected by friction against the needle (22) and the castle nut (29), thus the needle (22) is not rotationally bound to the crown nut (27) such as to prevent galling when the needle (22) tip contacts the valve body (21). The castle nut (29) locks the vertical position of the needle (22) along the axis (Y) relative to the crown nut (27) and the split pin (30) rotationally locks the crown nut (29).

If the valve (20) in its open position is subject to excessive temperature and/ or pressure the packers (231) and (232) will likely be damaged and the pressurised fluid contained within the valve cavity (C) will have free passage to escape through the annulus between the valve bore (B) and the needle (22) to the surrounding environment, potentially escalating a critical situation.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provides a useful alternative to prior art. The object is achieved through features, which are specified in the description below and in the claims that follow. The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In the following is described a preferred embodiment illustrated by the accompanying drawings, wherein:

Figure 1 Illustrates two representations of the the apparatus (A), for clarity both a full representation and a section representation with indication of the axis (Y) which the needle moves along while opening or closing the fluid passage.

Figure 2 Illustrates two representations of the apparatus (A), to the left is a 3D representation for clarity and to the right is a schematic representation for identification of the apparatus (A) parts.

The basic part is a valve body (1) which can be in any shape or form, a single valve or part of a block with a plurality of valves. In the valve body there is an inlet port (P1), an outlet port (P2) and a bore (B). Further there are sealing surfaces in the valve body (SP1), (SP2), (S11) and (S31) arranged to mate with corresponding sealing surfaces.

The bore (B) may be stepped, typically in three steps where the first step (BT) is threaded to accommodate the plug (3) and the crown (6), the second step (BC) may be smooth and forms a fluid cavity and the third step (BP) may be a narrow bore fluidly connecting the cavity (BC) with the inlet port (P1).

The inlet port (P1) and the outlet port (P2) may be fluidly connected through the cavity (BC) and may in operation be externally connected with threaded ferrules to tubes carrying the process fluid.

The needle (2) may consists of a single part formed in different sections where the first section (21) is the needle head having two sealing surfaces, one at its lower end (S12) and one at its upper end (S21), the head may also bear vertical grooves to ease fluid passage during vertical movement in the cavity (BC).

The second stem section (22) is smooth and fits tightly into holes in the packers (41) and (42), which in turn fit tightly into the plug (3) forming a tight seal between the cavity (BC) and the environment (E) while the needle is in an intermediate position (not open and not closed).

The third stem section (23) fits into the crown nut (8) and is finished by a threaded fourth stem section (24) adapted to fit a castle nut (10) and a hole in which a split pin (11 on Fig. 4, 5, and 6) is inserted rotationally locking the crown nut (10) with the needle (2).

The plug (3) (see Fig.3 for details) is threaded on its outside such that it fits the tread in the bore (BT) and has two sealing surfaces, one on its lower outer edge (S32) and one on its lower inner edge (S22).

There are typically two, or any other number of packers (41) and (42) adapted to fit tightly into the plug (3) in the annular space formed between the inner side of the plug (3) and the needle (2). The plug (3) is castellated on its upper end allowing securely tightening by use of a tool when inserted into the bore (B).

A squash plate (5) is adapted to fit above the plug (3), with a lower section adapted to fit inside the plug (3) and exert mechanical force onto the packers (41) and (42) situated inside the plug (3) when the crown (6) is tightened in a clockwise direction.

The crown (6) is threaded on its outside to fit into the valve bore (BT) and may be adjusted rotationally around the axis (Y) increasing or decreasing mechanical force exerted onto the packers (41) and (42), resulting in compression and elongation of the packers (41) and (42) subsequently increasing or reducing the pressure tightness between the needle (2) and the plug (3).

On the inside the crown (6) is threaded to fit the crown nut (8). The crown nut (8) is adapted such that the needle (2) passes through it and is locked in position relative to the crown nut (8) by a castle nut (10) which fits the needle (2) threaded portion (24). The castle nut (10) is held rotationally in place on the needle (2) by a split pin (11) passing through the slots in the castle nut (10) and a hole in the needle (2).

The crown nut (8) is interfaced with the castle nut (10) through a washer (9) and with the needle (2) through a washer (7) allowing free rotation of the crown nut (8) independent of the needle (2).

The needle (2) is not rotationally bound to the crown nut (8) such as to prevent galling when sealing surfaces (S12) and (S22) are in contact or when sealing surfaces (S21) and (S22) are in contact.

Operation of the crown nut (8) may be by use of an ordinary tool or a handle (12) may be placed on to the crown nut (8) easing operation.

Figure 3 Illustrates the apparatus (A) metal sealing surfaces. There are typically sealing surfaces on each connection port, inlet (P1) has a sealing surface (SP1) and the outlet (P2) has a sealing surface (SP2), both suited to mate with corresponding sealing surfaces of connection ferrules securing tubes to each port.

The seal made by the valve body (1) sealing surface (S11) and the needle (2) sealing surface (S12) making contact, make up the apparatus (A) closed position seal isolating the inlet (P1) from the cavity (BC).

The seal made by the needle (2) sealing surface (S21) and the plug (3) sealing surface (S22) making contact - and the seal made by the valve body (1) sealing surface (S31) and the plug (3) sealing surface (S32) being in contact - form the apparatus (A) open position seals isolating the inlet (P1) and cavity (BC) from the surrounding environment (E) through the bore (B).

Figure 4 Illustrates the basic valve block (1) of the apparatus (A) with its inlet (P1), its outlet (P2) and the bore (B) in where a closing device is fitted seen in a closed position. The following seals are formed; (S11), (S12) – isolating the inlet (P1) from the cavity (BC) and the surrounding environment (E) through the bore (B) (See Fig.3). Seals are exclusively metal – to metal.

Figure 5 Illustrates the basic valve block (1) of the apparatus (A) with its inlet (P1), its outlet (P2) and the bore (B) in where a closing device is fitted seen in an intermediate position. The following seals are formed; (S31), (S32) and packers (41) and (42) isolating the cavity (BC) from the surrounding environment (E) through the bore (B). Seals are not exclusively metal – to metal.

Figure 6 Illustrates the basic valve block (1) of the apparatus (A) with its inlet (P1), its outlet (P2) and the bore (B) in where a closing device is fitted seen in an open position. The following seals are formed; (S31), (S32) and (S21), (S22) – isolating inlet (P1), outlet (P2) and the cavity (BC) from the surrounding environment (E) through bore (B). Seals are exclusively metal – to metal.

Figure 7 Illustrates a valve (20) according to current art in a) a closed position and b) an open position.

The valve (20) is a typical example of current art. There is only one metal – to metal sealing function which is when the valve (20) is in its closed position and the needle (22) point is in contact with the the valve body (21) forming a metal – to metal seal. When the valve (20) is in any other position the pressure from the inlet port (P1) enters the cavity (BC) and is retained only by the packers (231) and (232) sealing the annular space between the valve body (21) and the needle (22). The packers are held in place by a squash plate (24) and the crown (25) which may be used to adjust the mechanical force exerted onto the packers (231) and (232). The castle nut (29) keeps the needle (22) vertically locked towards the crown nut (27) which if rotated clockwise will force the needle (22) down into a closed position and if rotated counter clockwise will pull the needle (22) up into an open position. The castle nut (29) is locked rotationally with the needle (22) by a split pin (30) passing through a hole in the needle (22) and the slots in the castle nut (29).

As the seals preventing pressurised fluid from leaking through the bore (B) and into the surrounding environment (E) in the valves intermediate or open positions are not metal – to metal the valve packers (231) and (232) will when exposed to excessive pressure/ temperature break down leading to leakage of fluids from the cavity (BC) through the bore (B) to the surrounding environment (E).

The apparatus (A) of the invention as described and illustrated (Figures 1, 2, 3, 4, 5 and 6) provides metal – to metal sealing in both operational positions, open and closed.

This feature is particularly useful in situations where there is a demand for an instrument isolation valve to be open at all times within an area subject to fire classification, for instance when continuous pressure monitoring may be required and the valve needs to be open at all times.

The valve as presented may then be open in all situations without risk of leakage due to excessive temperature and/ or pressure caused by extraneous circumstances such as fire, without the risk of leaking potentially hazardous fluids.

The apparatus (A) fulfils this requirement by employing a gas and fluid tight metal – to metal seal in its closed position as well as in its open position.

Claims

C l a i m s

1. An apparatus (A) for opening and closing a fluid passage, where the fluid inlet port is isolated from the environment through the apparatus by metal – to metal seals both in open and closed position c h a r a c t e r i s e d i n that the apparatus comprises:

- a valve body (1) with a cylindrical bore (B), a needle (2) with a lower head section (21) with a diameter larger than the hole in the plug (3) placed within the bore and a plug (3) with a hole, arranged in the bore (B) around the needle stem (22), thus occupying the annulus space between the bore (B) and the needle stem (22), aligned with an axis (Y) passing through the valve body, an inlet port (P1) fluidly connected to the bore (B) below the sealing surface (S11) of the bore (B), and an outlet port (P2) fluidly connected to the bore (B) above the sealing surface (S11) and below the sealing surface (S32) or (S22) of the plug (3), where;

- the plug (3) has a sealing surface (S32) which when made to contact a sealing surface (S31) arranged in the valve body (1), forms a metal – to metal seal

- the needle (2) head section (21) has a sealing surface (S12) on its lower end, which when brought into contact with a sealing surface (S11) in the valve body (1) forms a metal - to metal seal isolating the inlet port (P1) from the environment (E) through the bore (B)

- the needle (2) head section (21) has a sealing surface (S21) on its upper end which when brought into contact with a sealing surface (S22) in the plug (3) forms a metal - to metal seal isolating the inlet port (P1) and the outlet port (P2) from the environment (E) through the bore (B)

2. The apparatus according to the previous claim where the annular space between the needle (2) and the plug (3) is closed off by one or more circular packers (41) sealing the bore (B) from the environment (E) while the needle is in an intermediate position (not closed and not open)

3. The apparatus according to any of the previous claims where the opposing sealing surfaces have differing angles relative to the axis (Y) and where the angle relative to the axis (Y) of the minor diameter sealing surface is less than the angle relative to the axis (Y) of the major diameter sealing surface.

4. The apparatus according to any of the previous claims where loose seals are applied to any of the parts described