WO2012096618A1

WO2012096618A1 - Method and device for determining position and orientation of a valve seat

Info

Publication number: WO2012096618A1
Application number: PCT/SE2012/050010
Authority: WO
Inventors: Lars-Inge Larsson
Original assignee: Larslap Ab
Priority date: 2011-01-11
Filing date: 2012-01-10
Publication date: 2012-07-19

Abstract

A method is disclosed for determining a position and orientation of a valve seat (3a, 3b) forming part of a valve (1). The method comprises determining a reference point of the valve (1) and determining said position and orientation of the valve seat (3a, 3b) with respect to said reference point. In the method, the determining of the reference point comprises using a sensor (13) to detect at least one fixed valve feature and determining said reference point at least partially based on a position of said valve feature. A device for carrying out the method is also disclosed.

Description

METHOD AND DEVICE FOR DETERMINING POSITION AND

ORIENTATION OF A VALVE SEAT

Technical Field

The present invention relates to a method and a device for determining position and orientation of a valve seat forming a part of a valve. Background

Valves are used to control flows of e.g. slurries, gases and/or liquids in various process industries. These valves are frequently fixedly installed, large and bulky, and very difficult and/or expensive to exchange. The valves are frequently subjected to wear, e.g. in the form of mechanical wear, corrosion or fatigue. One part which is particularly critical in a valve is the valve seat. The valve seat must present a very good fit with a corresponding valve plug in order to seal properly.

When installing and/or maintaining a valve, it is possible to grind, polish or lap the valve seat to render it planar and smooth and thus to bring it into a sufficient fit with the valve plug.

A valve body is generally formed through a casting operation, which may be followed by surface treatment such as sand blasting and painting. This is particularly the case when the valve body is formed by casting of an iron alloy in a sand-based mould. Hence, the valve body typically may have a fairly rough surface and quite large tolerances.

The valve seats are in many cases formed from a separate piece (e.g. having particular material properties), which is fitted to the valve at the desired position by e.g. welding or threading. Renovating a valve may involve removal and replacement of a valve seat.

Devices for grinding valve seats are known from e.g. WO85/05311 A1.

This document discloses an arrangement for grinding planar annular sealing surfaces of a valve.

However, when grinding the valve seat, some material will be removed. Hence, it is only possible to grind a valve seat to a certain extent before it is "consumed" and needs to be replaced. Furthermore, there may also be a point at which the valve seat will no longer fit and seal properly with the valve plug, because too much of the valve seat has been removed.

Hence, the maintenance of valves presents a plurality of challenges. One particular challenge is to estimate the remaining life of a valve seat. Another challenge is to determine position and orientation of one or more valve seats forming part of a valve in order to provide a matching valve plug. Yet another challenge is to check whether a valve seat position and/or orientation is acceptable or not, e.g. in connection with an installation and/or grinding operation.

These challenges may be particularly difficult when a valve is installed, since access to the valve seat or seats may be limited to a valve access opening, after removal of a valve bonnet.

JP2000298015 A discloses an apparatus for measuring flatness of valve seat surfaces in an installed valve. A tip end of a displacement gauge is rotatably driven in contact with a valve seat surface, and a flatness of the valve seat surface is measured.

JP 2000298012 A discloses a distance measuring apparatus fixed to a housing to measure a distance between valve seat surfaces in a valve gear. The distance between the valve seat surfaces is obtained by a movement distance of a moving stage and distance to the valve seat surfaces detected by the displacement gauges.

Neither of the above apparatuses is suitable estimating wear of the valve seat, since neither is able to accurately determine an absolute position and orientation of an individual valve seat.

Hence, there is a need for a way of accurately and repeatably determining a position and orientation of a valve seat.

Summary

It is a general object to provide an improved method and device for determining a position and orientation of a valve seat.

It is a specific object to provide a method and device for accurately and repeatably determining a position and orientation of a valve seat. The invention is defined by the appended independent claims, with embodiments being set forth in the dependent claims, in the following description and in the drawings.

According to a first aspect, there is provided a method for determining a position and orientation of a valve seat forming part of a valve. The method comprises using a measuring probe to detect at least one fixed valve feature, determining a reference point of the valve at least partially based on a position of said fixed valve feature and determining said position and orientation of the valve seat with respect to said reference point. The fixed valve feature is a modified portion of the valve body or a portion which is affixed to the valve body.

By determining a reference point, it is possible to obtain an absolute indication of the valve seat position and orientation in relation to the valve.

A "fixed valve feature" may be a structure which is fixedly and permanently provided in the valve, e.g. on the valve housing or on a part which is fixedly connected with the valve housing. The feature may be a functional part of the valve, or it may be a dedicated identification structure.

By determining the reference point based on a fixed valve feature, it is possible to accurately determine the absolute position of a valve seat surface forming part of the valve.

In one embodiment, the fixed valve feature may be selected from a group consisting of a valve seat edge, a machined portion of the valve access channel, and a separate part which is fixedly mounted to a wall of the valve access channel.

By using the valve seat edge, a feature is selected which is present in any valve, and which is subject to wear in substantially only one direction, thereby reducing the risk of misalignment due to wear of the valve seat.

The valve seat edge may substantially define a first valve seat edge plane, and the detecting may comprise detecting a first position of a first portion of the valve seat edge, moving the sensor in a first predetermined manner, and subsequently detecting a second position of a second portion of the valve seat edge. Hence, two points of the valve seat will be known, as will their relationship.

The method may further comprise moving the sensor in a second predetermined manner, detecting a third position of a third portion of the valve seat edge, moving the sensor in a third predetermined manner, and subsequently detecting a fourth position of a fourth portion of the valve seat edge.

In the method, a first line, comprising the first and second positions may be substantially perpendicular to a second line, comprising the third and fourth positions.

The third and fourth positions may be located on opposite sides of the first line.

The method may further comprise detecting a valve housing feature, and determining said reference point based also on said valve housing feature.

The method may further comprise providing a three dimensional coordinate system, having an initial reference point, detecting said valve seat edge portions with respect to the initial reference point, and providing said reference point based on said position of said fixed valve feature.

The initial reference point may be provided based on at least one of a fixture mounted at a valve access opening, and an arbitrary position at the valve body.

In particular, the reference point may be positioned on a line forming a central axis of the valve seat.

The reference point may be positioned on a line, which is substantially perpendicular to a valve access opening. For example, this line may be the center line of the access opening.

Furthermore, the determining of the reference point may comprise using a sensor to detect at least one second valve seat edge of a second valve seat; and determining said reference point based also on a position of said second valve seat edge.

The method may further comprise detecting at least one position of a surface point of the valve seat with respect to said reference point. The positions may be stored in a memory and associated with the individual valve. Hence, a database comprising a plurality of valves and the characteristics of the valve seats of each individual valve may be provided.

According to a second aspect, there is provided a device for

determining a position and orientation of a valve seat, comprising a fixture adapted to be mounted at a valve access opening, and a measuring probe. The measuring probe is movable with at least two degrees of freedom relative to the fixture.

At least one of said degrees of freedom may be provided in the form of a linear movement in a plane parallel with a plane comprising the valve access opening.

The device may comprise an arm, which is connected to the fixture and adapted to carry the measuring probe. The arm is movable relative to the fixture parallel with a plane comprising the valve access opening, and wherein the measuring probe is linearly movable relative to the fixture, with and/or or relative to the arm, in a direction substantially perpendicular to said plane.

The device may be used for carrying out the method disclosed above.

The arm may be movable in a direction perpendicular to said plane.

The measuring probe may comprise a non-contact sensor.

The measuring probe may comprise an elongate probe housing, wherein a beam forming component is arranged at a first end of the probe housing, and a beam deflecting component is arranged at a second end of the probe housing.

The device may further comprise a support member configured to extend into a valve access channel and to engage a valve plug guide.

The support member may present first and second clamping members adapted to clamp said valve plug guide therebetween.

A position of at least one, preferably both, of said clamping members may be controllable in a direction substantially parallel with the valve plug guide, and said at least one clamping member may present a guide surface forming a sharp angle relative to the valve plug guide, said guide surface being arranged to guide the clamping member towards the valve plug guide when said clamping member is moved in a first direction substantially parallel with the valve plug guide, and away from the valve plug guide upon movement in an opposite direction substantially parallel with the valve plug guide .

According to a third aspect, there is provided a valve seat grinder or a valve seat measuring device, comprising a fixture adapted to be mounted at a valve access opening, wherein the fixture presents a substantially U-shaped frame, as seen in a plane parallel with the valve access opening.

According to a fourth aspect, there is provided a valve seat grinder or a valve seat measuring device, comprising a support member configured to extend into a valve access channel and to engage a valve plug guide.

Brief Description of the Drawings

Fig. 1 is a schematic perspective view of a valve 1 , with some parts cut away, and a measuring device 0 fixed to it.

Fig. 2 is a schematic perspective view of the valve 1 of Fig. 1 , with further parts being cut away.

Fig. 3 is a schematic sectional view of the valve of Fig. 1 , taken in a plane Y-Z, perpendicular to a flow direction of the valve 1.

Fig. 4 is a schematic sectional view of the valve of Fig. 1 , taken in a plane X-Y, parallel with flow direction of the valve 1.

Fig. 5 is a schematic sectional view of the valve of Fig. 4, with a measuring device mounted to it.

Fig. 6 is a schematic sectional view of the probe 13.

Fig. 7 is a schematic view of a support mechanism 111.

Fig. 8 is a schematic view of an alternative measuring device.

Figs 9-10 are schematic views of an alternative support member.

Description of Embodiments

Fig. 1 schematically illustrates a valve 1 with some parts cut away. The valve comprises a valve body 2, first and second valve seats 3a, 3b, first and second valve channels 4a, 4b, first and second channel flanges 5a, 5b, an access opening 6, an access flange 7 and an access channel 8 having an access channel wall 9. Furthermore, in Fig. 1 , a valve bonnet (not shown) has been removed, as has a valve plug (not shown) and an associated actuating mechanism (not shown). A measuring device 10 according to the present disclosure has been mounted at the access opening 6.

Fig. 1 illustrates a coordinate system (X-Y-Z), which will be referred to in the following description.

The measuring device 0 may comprise a fixture 11 , an arm 12 and a probe 13.

The fixture 1 may comprise a frame 110, a support mechanism 111 for firmly, but releasably mounting the frame 110 to the access opening 6, a guide 112, a cradle 113, which is movable along the guide 112, an arm 12, which is connected to the cradle 113 and which carries a probe 13.

The support mechanism 111 (Fig. 7) may be adapted to engage a guide forming part 9a of the valve 1. This may be particularly advantageous when the valve 1 comprises e.g. a linear guide (Y axis), along which a valve plug is to move.

The support mechanism 111 may thus engage a valve plug guide 9a (Fig. 4), in the event that such a valve plug guide has a sufficient vertical extent. It is also possible to have the support mechanism interact indirectly with a valve plug guide, e.g. via an adapter. This may be suitable for valves where the valve plug guide does not extend sufficiently high up in the valve access channel 8.

The support mechanism 111 may comprise a pair of support arms 1110, which are adapted to engage respective opposing wall portions 9 of the access opening 6. The support arms 1110 may be connected to a centering mechanism 1111 , 1112, which may be arranged to cause the fixture 11 to become centered relative the access opening 6 when the support arms 1110 are in engagement with their respective wall portion 9. The centering mechanism may be provided in the form of a mechanical centering

mechanism comprising e.g. a threaded rod 1111 , having portions with oppositely arranged threads, each portion engaging a respective support arm 1110. Hence, when the rod 1111 is caused to rotate by an actuating mechanism 1112, the support arms 1110 will move in opposite directions. The actuating mechanism 1112 may be a manual mechanism comprising a lever or an engagement connector for a wrench or other type of key. In the alternative, the actuating mechanism may be an actuator, which may e.g. be electrically operable.

The guide 112 may be arranged to run along a transversal direction Z of the valve 1.

A cradle 113 may be arranged to run along the guide 112. The cradle may be fixedly attached to the arm 12. In the alternative, the arm 12 may be movable relative to the cradle 113.

A cradle actuating mechanism 114 may be provided, arranged to cause the cradle to move along the guide 112 along the Z axis. The cradle actuating mechanism 114 is illustrated as comprising a crank, but may be provided in the form of a motor, which may be electrically driven.

An arm actuating mechanism (not shown) may be provided on the arm 12 and/or on the cradle 113 to cause the arm 12, and thus the probe 13, to move along the Y axis, or to cause the probe 13 to move along the arm 12, as may be the case.

The arm actuating mechanism may be provided in the form of a motor or similar device.

The probe 13 (Fig. 6) may be a non-contact probe, e.g. comprising a beam source 134 (e.g. laser), a corresponding sensor 135 and a processing device 136 for providing a distance determination based on a signal received by the sensor 135. Such probes are known per se, and thus need no further description.

In the illustrated embodiment, the light source 134 and the sensor 136 may be provided in an upper part 131 of a probe housing 130. At the lowermost part 132 of the probe housing, there may be a mirror arrangement 133 provided, arranged to reflect outgoing and incoming beams 137, 137' towards the measuring area 3a and the sensor 135, respectively.

In one embodiment, the probe may be configured to measure in both directions parallel with the X axis. Thus, e.g. opposing valve seats may be measured in a single movement sequence. It is possible to use one or more semitransparent mirrors (not shown), in order to provide beams 137a, 137b in both directions parallel with the X axis.

The description will now focus on the operation of the measuring device 10. In order to determine a position and orientation of a valve seat 3a, 3b, the valve bonnet and the actuating mechanism are removed, as is the valve plug. In the illustrated example, the valve 1 is a wedge slide valve, having two opposing valve seats 3a, 3b, which are substantially planar and slightly inclined, with an angle a of e.g. about 3-10 degrees, relative to the Y-Z plane (see Fig. 4).

The fixture 11 is mounted at the access flange 7 of the valve 1.

Support members 1110 are arranged inside the valve opening 6 and caused to expand so as to firmly abut the walls 9 of the access channel 8. Optionally, the support members 1 10 may be fitted against a vertical guide member 9a provided on the inside of the wall 9 and adapted to operate as a guide for the valve plug's sliding movement. In the illustrated embodiment, the frame 11 of the fixture is arranged to extend in parallel with the Z axis, i.e. substantially perpendicular to a flow direction X of the valve, or substantially parallel with a horizontal component of a plane defined by the valve seat.

As a starting position, the arm 12 and the probe 13 may be brought to a center position of the fixture 11 , which, as a consequence of the design and mounting of the fixture 11 may substantially correspond to a vertical centre axis L3 of the access channel 8.

The probe 13 is then lowered into the access opening 6 towards the level of the valve seats 3a, 3b. At some point while still in the access channel 6, the probe 13 may measure its position relative a wall portion 9 of the access channel 8. Optionally, where the probe may be arranged to measure in two opposite directions, distances to two opposing wall portions of the access channel 8 may be measured. These measurements may be used to verify the positioning of the fixture 11 , to provide a dimension on which an initial reference point may be determined and/or to provide a dimension on which the (final) reference point may be determined. The probe 3 may then be further lowered while activated. At some point 3.1 (Fig. 3), the signal from the probe will shift from indicating a relatively short distance to indicating a much larger distance. Hence, the upper edge 3.1 of the valve seat has been detected.

The probe 13 may then be further lowered linearly along line L1

(parallel with the Y axis) until it once again comes to indicate a relatively short distance. Hence the lower edge 3.2 of the valve seat has been detected.

The probe may then be raised a distance corresponding to e.g. half the distance between the upper and lower valve seat edges 3.1 , 3.2, where it will indicate a relatively long distance. Then the probe may be caused to move substantially horizontally, along line L2 in a first direction which is parallel with the Z axis until a relatively short distance is indicated. Hence, a first lateral valve seat edge 3.3 has been detected.

The probe may then be caused to move along line L2, in a second horizontal direction, which is opposite to the first direction, until once more, a relatively short distance is indicated. Hence, a second lateral valve seat edge 3.4 has been detected.

At this point, four points of the valve seat edge are known with respect to X, Y and Z coordinates. However, due to the inclination of the valve seat, the X coordinates may be disregarded.

A central axis A of the valve seat may then be determined based on the four valve seat edge points which are now known. In the illustrated example, the Y coordinate halfway between the upper and lower valve seat edges 3.1 , 3.2 may be selected as a base Y coordinate for the coordinate system. The Z coordinate halfway between the lateral valve seat edges 3.3, 3.4 may be selected as a base Z coordinate for the coordinate system.

One advantage of selecting Y and Z coordinates based on the valve seat edge is that these coordinates will remain even though the valve seat surface becomes worn or is subjected to grinding, since such wear will operate only in the X direction.

The process may be repeated, or in practice performed

simultaneously, for the valve seat edges of the opposing, second valve seat 3b. The Y and Z coordinates of the reference point may then be selected based on one or both (e.g. an average) of the valve seats 3a, 3b. On replacing valve seats (e.g. by removing a consumed valve seat and refitting (welding on) a new valve seat, one valve seat may be replaced at a time, with the other being used to as a reference.

It now remains to determine the X coordinate of the reference point.

As mentioned above, one option is to use the X coordinate as determined by the mounting of the fixture or as determined by one or more measurements on the access channel wall 9.

By taking the X coordinate off e.g. the access channel wall 9, after the

Y and Z coordinates have been determined, it is possible to determine the location of this point accurately and repeatedly, as its Y and Z coordinates are known.

Once the reference point has been established, one or more positions M1 , M2, M3, M4 on the valve surface are to be measured. The probe will be moved to a respective predetermined position in the Y and Z dimension, after which a distance to the valve seat surface in the X dimension is determined. The position in the Y and Z dimensions may be determined as a position which is about e.g. 45 degrees off the Y axis and radially spaced from the valve seat edge. Further Y-Z positions may be determined by regular intervals, e.g. 90 degrees spaced apart, at which associated X values are determined.

At this point, exact positions of a predetermined number of points on the valve seat surface are known. This information may be sufficient to characterize the valve seat surface with respect to position and orientation.

The values may be used as outlined by way of introduction above, e.g. to estimate wear/remaining life time of the valve seat or as a basis for producing a properly fitting valve plug. With a sufficient number of

measurements on the valve seat surface, it is possible to determine flatness of the valve seat.

A data processing device 14 may be provided for receiving the measurement data and storing it in a database along with identifiers and other characteristics of the valve. Hence, a database comprising data of a plurality of valves may be provided, wherein data on position and orientation of each individual valve seat of each individual valve is kept. In such a database, data from several measurement occasions may be kept for each valve, thus enabling a user to follow the wear of the valve seat and optionally to predict future wear and maintenance needs.

One option is to provide the valve with some reference surface, which is not in contact with the active parts of the valve, and which is thus not subjected to wear, contamination or corrosion, and which may thus be used as a reference for one or more dimensions of a coordinate system.

It is noted that it is not essential that the valve seat edge points are identified at the horizontal and vertical centers of the valve seat, but it may be convenient from a design perspective. It is also not essential that the movements of the probe are strictly parallel to the Y and Z axes, respectively, but it may also be convenient from a design perspective.

The method and device disclosed above may be used for wedge type or parallel slide valves, having two valve seats, as mentioned, but also for other types of valves, including such valves having only a single valve seat.

In order to determine a position and orientation of a valve seat of a valve having a valve seat which is parallel with the access opening, such as e.g. a control valve, the measuring device may comprise a fixture adapted to be mounted at a valve access opening, and a measuring probe. The measuring probe may be movable with at least two degrees of freedom relative to the fixture. For example, the measuring probe could be linearly movable with two degrees of freedom in a plane parallel with the access opening. As an alternative, the probe could be rotatable about two axes. A combination of linearly moveable along one axis and rotatable about that axis is also conceivable. An arm and a cradle as described above may also be provided, but are optional, since it is may be possible to measure the valve seat from a greater distance.The method and device disclosed above may be used for valve seats which are substantially planar, for valve seats which are conical or even for valve seats which are spherical. For example by causing the probe to move along a radial line of the valve seat while activated, data may be obtained along that entire line, showing the planar, conical or spherical shape of the valve seat.

The disclosed method and device are flexible in that they allow multiple measurements to be made at any position within the Y-Z plane.

There are various ways of determining the reference point of the valve

1. For example, it is possible to determine the reference point as a

predetermined position of the measuring device 10, provided that it is possible to mount the measuring device accurately enough. This may be possible if the measuring device is mounted against an accurately formed part of the valve body, such as a machined part, e.g. a machined flange, a machined guide member or one or more holes 71 in formed in the flange 7.

The measuring device 0 may also be mounted to the valve 1 via an adapter (not shown). For example, the adapter may be mounted to the valve flange 7, and the measuring device may, in turn, be mounted to the adapter, thus providing an indirect mounting of the measuring device 10.

It is also possible to provide a valve with special fixed valve features, which are intended to be used either for mounting the measuring device or for detection by the measuring device. Such fixed valve feature may have the form of one or more machined portions of the valve access channel, or of separate parts which are fixedly mounted to e.g. walls of the valve access channel. The fixed valve feature or features may have a predetermined shape or be arranged in a predetermined pattern relative each other.

While the probe 13 above has been described as a laser probe, it is possible to use other techniques for the measurement. Examples of non- contact probes include laser, ultrasound and camera vision based probes. For example, a stereoscopic camera could be utilized. It is also possible to use contact type probe systems.

Fig. 8 schematically illustrates a measuring device having an

alternative support mechanism. In this embodiment, the probe 13 is vertically slidable relative to a substantially vertically oriented cradle 213. The cradle 213 is, in its turn, substantially horizontally slidable relative to a frame 21 , which comprises a bridge portion 211 and a pair of angular portions 212a, 212b. The bridge portion provides one or more guides along which the cradle 213 is slidable.

The bridge portion 211 and the angular portions 212a, 212b may, as seen from above, or in a plane parallel with the valve access opening, form a structure which is laterally open and which may be substantially U-shaped, with the probe 13 being fully accessible through the lateral opening. Hence, this embodiment provides a support mechanism, which makes it easier to access and replace the probe 13.

Figs 9 and 10 show another embodiment of the support members 2110. These support members may be used in either of the previously disclosed embodiments.

Fig. 9 illustrates a support member, which is adapted for being clamped to a valve plug guide 9a.

The support member may present a support member body 2111 , having a load bearing surface 2112, which is adapted for abutting the valve access flange 7, and in particular a machined portion of such flange. Hence, a major portion of the weight of the measuring device will be carried by the load bearing surfaces. Typically, the valve access flange 7 may present such a machined portion intended for sealing against a valve bonnet. The machined portion may form an edge of the valve access opening.

The support member 2110 further presents a guide receptacle 2113, which is axially and laterally open and adapted for receiving an uppermost part of the valve plug guide 9a (Figs 3, 4). In the receptacle 2113, there is at least one, possibly two, gripping members 2114a, 2114b, which may be slidable relative to the support member body and which may be arranged to interact with the support member body through one or more cam surfaces 21 5, such that the gripping members 2114a, 2114b when caused to slide axially also are caused to reduce the opening of the receptacle 2113.

The gripping members 2114a, 2114b may be connected to a control device 2 16, 2118 which is adapted to cause the gripping members to slide relative to the support member body 2111 , thus causing the gripping members to engage the valve plug guide 9a. The control device may comprise a control member 2116, which may be acutated by e.g. turning it about its longitudinal axis, with the axial movement being provided by e.g. threads or by interacting cam surfaces. The control member 2116 may be connected to a setting member 2118, which may be adapted for interaction with e.g. a key or wrench, in order to cause the control member 2116 to be slidingly and/or rotatably displaced.

The inclination of the cam surfaces 2115 may be adapted to provide a sufficient clamping force in view of the axial movement and force which can be provided by the control member.

As shown in Fig. 10, the support member may be provided with cover plates 2117a, 2117b to keep the gripping members 2114a, 2114b in place.

Moreover, referring to Fig. 8, an auxiliary guide part 70 may be inserted into the valve in case the valve does not itself comprise any valve plug guide 9a. The auxiliary guide part 70 may be adapted to substantially follow an inner cross section of the valve body. As illustrated, the auxiliary guide part 70 may be substantially U-shaped. The support members 1110 and 2110 may thus be caused to engage such auxiliary guide part, whereby the device can be used also for valves which do not have any valve plug guide 9a.

It is noted that the support mechanisms and the support members disclosed above may be used for measuring devices, but also for e.g. a valve grinding device, such as the one disclosed in e.g. WO85/05311 A1.

Claims

1. A method for determining a position and orientation of a valve seat (3a, 3b) forming part of a valve (1), the method comprising:

using a measuring probe (13) to detect at least one fixed valve feature, determining a reference point of the valve (1) at least partially based on a position of said fixed valve feature, and

determining said position and orientation of the valve seat (3a, 3b) with respect to said reference point,

wherein said fixed valve feature is a modified portion of the valve body or a portion which is affixed to the valve body.

2. The method as claimed in claim 2, wherein said fixed valve feature is selected from a group consisting of:

a valve seat edge (3.1 , 3.2, 3.3, 3.4),

a machined portion of the valve access channel, and

a separate part which is fixedly mounted to a wall of the valve access channel.

3. The method as claimed in claim 2, wherein the valve seat edge substantially defines a first valve seat edge plane, and said detecting comprises:

detecting a first position of a first portion (3.1) of the valve seat edge, moving the measuring probe in a first predetermined manner, and subsequently detecting a second position of a second portion (3.2) of the valve seat edge.

4. The method as claimed in claim 3, further comprising:

moving the measuring probe in a second predetermined manner, detecting a third position of a third portion (3.3) of the valve seat edge, moving the measuring probe in a third predetermined manner, and subsequently detecting a fourth position of a fourth portion (3.4) of the valve seat edge.

5. The method as claimed in claim 4, wherein a first line (L1), comprising the first and second positions (3.1 , 3.2), is substantially

perpendicular to a second line (L2), comprising the third and fourth positions (3.3, 3.4).

6. The method as claimed in claim 5, wherein said third and fourth positions (3.3, 3.4) are located on opposite sides of the first line (L1).

7. The method as claimed in any one of the preceding claims, further comprising detecting a valve housing feature (9, 9a), and determining said reference point based also on said valve housing feature (9, 9a).

8. The method as claimed in any one of the preceding claims, further comprising:

providing an three dimensional coordinate system (X, Y, Z), having an initial reference point,

detecting said valve seat edge portions (3.1 , 3.2, 3.3, 3.4) with respect to the initial reference point, and

providing said reference point based on said position of said valve seat edge.

9. The method as claimed in claim 8, wherein the initial reference point is provided based on at least one of:

a fixture (11) mounted at a valve access opening (6), and

an arbitrary position at the valve body (2, 9).

10. The method as claimed in claim 8 or 9, wherein said reference point is positioned on a line forming a central axis of the valve seat (3a, 3b).

11. The method as claimed in any of the preceding claims, wherein said reference point is positioned on a line (L3), which is substantially perpendicular to a valve access opening (6).

12. The method as claimed in any one of the preceding claims, wherein the determining of the reference point comprises:

using a sensor ( 3) to detect at least one second valve seat edge of a second valve seat (3b); and

determining said reference point based also on a position of said second valve seat edge.

13. The method as claimed in any one of the preceding claims, further comprising detecting at least one surface point (M1 , M2, M3, M4) of the valve seat with respect to said reference point.

14. A device for determining a position and orientation of a valve seat, comprising:

a fixture (11) adapted to be mounted at a valve access opening (6), and

a measuring probe (13);

wherein the measuring probe (13) is movable with at least two degrees of freedom relative to the fixture (11).

15. The device as claimed in claim 18, wherein at least one of said degrees of freedom is provided in the form of a linear movement in a plane parallel with a plane comprising the valve access opening (6).

16. The device as claimed in claim 14 or 15, further comprising: an arm (12), which is connected to the fixture (11) and adapted to carry the measuring probe (13);

wherein the arm (12) is movable relative to the fixture (11) parallel with a plane comprising the valve access opening (6), and

wherein the measuring probe (13) is linearly movable relative to the fixture (11), with and/or or relative to the arm (12), in a direction substantially perpendicular to said plane.

17. The device as claimed in any one of claims 14-16, wherein the arm (12) is movable in a direction perpendicular to said plane.

18. The device as claimed in any one of claims 14-17, wherein the measuring probe (13) comprises a non-contact sensor (134, 135).

19. The device as claimed in any one of claims 14-18, wherein the measuring probe (13) comprises an elongate probe housing (130), wherein a beam forming component is arranged at a first end (131) of the probe housing (130), and a beam deflecting component is arranged at a second end (132) of the probe housing.

20. The device as claimed in any one of claims 14-19, wherein the fixture presents a substantially U-shaped frame, as seen in a plane parallel with the valve access opening.

21. The device as claimed in any one of claims 14-20, further comprising a support member (1110) configured to extend into a valve access channel (8) and to engage a valve plug guide (9a).

22. The device as claimed in claim 21 , wherein the support member presents first and second clamping members adapted to clamp said valve plug guide therebetween.

23. The device as claimed in claim 22, wherein a position of at least one, preferably both, of said clamping members is controllable in a direction substantially parallel with the valve plug guide (9a), and wherein said at least one clamping member presents a guide surface forming a sharp angle relative to the valve plug guide (9a), said guide surface being arranged to guide the clamping member towards the valve plug guide (9a) when said clamping member is moved in a first direction substantially parallel with the valve plug guide, and away from the valve plug guide upon movement in an opposite direction substantially parallel with the valve plug guide (9a).

24. A valve seat grinder or a valve seat measuring device, comprising a fixture (11) adapted to be mounted at a valve access opening (6), wherein the fixture presents a substantially U-shaped frame, as seen in a plane parallel with the valve access opening.

25. A valve seat grinder or a valve seat measuring device, comprising a support member (1 1 10) configured to extend into a valve access channel (8) and to engage a valve plug guide (9a).