Erosion monitoring system

Abstract

A system for monitoring the erosion of internal components of a valve having a valve (200, 300, 400) which in turn comprising a body (44, 17, 24), a trim (46, 19, 26) and a seat (21, 28, 48) and at least an ultrasonic probe (22, 40, 29) able to transmit ultrasonic waves through the internal components and receive waves reflection through. In this system, the gaps between the internal components of the valve are closed and the distances between them are almost equal to zero so that the continuity between components is able to transfer the waves determining therefore the distance between the ultrasonic probe (22, 40, 29) and the internal component to be monitored.

Claims

1. A system for monitoring erosion of internal components of a valve comprising a valve (200, 300, 400) which, in turn, comprises: a body (44, 17, 24), a trim (46, 19, 26), a seat (21, 28, 48), at least an ultrasonic probe (22, 40, 29) able to transmit ultrasonic waves through the internal components and receive waves reflection through; wherein said system has gaps between the internal components of the valve that are considered closed, wherein distances between them are almost equal to zero, so that a continuity between components is able to transfer waves determining therefore a distance between said ultrasonic probe (22, 40, 29) and said internal component to be monitored; and wherein said gaps between the body (44, 17, 24) and the trim (46, 19, 26) are closed by a compensator (36) mounted between the body (44, 17, 24) and the trim (46, 19, 26).

2. The system according to claim 1, wherein said gaps between the body (17, 24) and the seat (21, 28) are closed by mating conical surfaces of the body (17, 24) and conical surfaces of the seat (21, 28) which are reciprocally in contact.

3. The system according to claim 1, wherein said gaps between the body (44) and the seat (48) are closed by a pressure fit mounted for concentric cylindrical surfaces of the body (44) and the seat (48).

4. The system according to claim 1, wherein said gaps between the body (44) and the seat (48) are closed by shrink fit mounted cylindrical surfaces, and by heating the body and allowing thermal expansion of the seat guiding area.

5. The system according to claim 1, wherein said gaps between the body (44, 17, 24) and the seat (21, 28, 48) are closed by using a seat (21, 28, 48) integral to the body (44, 17, 24).

6. The system according to claim 1, wherein said gaps between the body (44, 17, 24) and the seat (21, 18, 48) are closed by welding or by a brazing process.

7. The system according to claim 1, wherein said compensator (36) has a cylindrical shape and has a curved head matching the external radius of the trim (46, 19, 26).

8. The system according to claim 1, wherein said compensator (36) has a head with a flat surface and the trim (46, 19, 26) has a flattened spot.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be now described by reference to the enclosed drawings, which show some non-limitative embodiments, namely:

(2) FIG. 1 shows a cross section of a wellhead Choke valve with “cage and plug” design, according to the background art,

(3) FIG. 2 shows a detail of FIG. 1, showing the evolution of erosion process during lifetime;

(4) FIG. 3 shows a graph showing the behavior during lifetime of the valve characteristic curve, due to the erosion of internal components, such characteristic being measured according to the background art;

(5) FIG. 4 shows an erosion monitoring system based on ultrasonic probes according to the background art;

(6) FIG. 5 shows a cross section of a wellhead Choke valve and a new erosion monitoring system based on ultrasonic waves according to an embodiment of the present invention;

(7) FIG. 6 shows a cross section of a wellhead Choke valve and a new erosion monitoring system based on ultrasonic waves according to a further embodiment of the present invention;

(8) FIG. 7 shows a cross section of a choke valve and the new erosion monitoring system based on ultrasonic waves according to an alternative embodiment of the present invention;

(9) FIG. 8 shows a horizontal sectional view of the valve as in FIG. 6, and the new erosion monitoring system based on ultrasonic waves according to the embodiment of the present invention, as in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) According to the embodiments of the present application, and according to the FIGS. 5-8, there is a way to measure and detect the erosion of the seat of a valve (in particular a choke valve). The new erosion monitoring system is realized by a special design of the seat, which is closing the gaps between the body and the seat itself. This special design is based on one or more of the following approaches:

(11) (a) mating conical surfaces. In other words the seat and the body have conical surfaces with similar angles, so that the seat is installed into the body with full contact area able to transmit waves;

(12) (b) pressure fit mounted for concentric cylindrical surfaces. This means that the assembly process is realized by means of pressure from top and minimum interference gap;

(13) (c) shrink fit mounted cylindrical surfaces. The assembly of the seat onto the body is realized by heating the body and allowing thermal expansion of the seat guiding area, in order to close the gap at cold operating condition;

(14) (d) seat integral to the body;

(15) (e) welding or brazing process.

(16) In particular, the mating conical surfaces approach is represented in FIG. 5, according to a first embodiment of the invention.

(17) In such a figure a valve 200 is shown and comprises a body 17, a plug 18, a control element or trim 19, flow ports 20 and a seat 21.

(18) The continuity of the seat 21 and the body 17 assembly is shown. In fact, with respect to FIG. 4, the seat 21 has a wedge, which grants the continuity between body and seat and therefore this configuration is able to transfer the waves up to the tip of the seat 21, determining therefore, in a very precise way, the distance between the probe 22 and the potential area subject to erosion. In FIG. 5, this measure is indicated with the letter “b”. Ultrasonic waves are traveling through different materials and reflected at the seat surface. The precision of the measure “b” is not extremely important, but it should be compared in time with the original measure, provided that the position and inclination of probe 22 is not modified along with the time. On this purpose, it must be used a proper support, or a simple machining of the body 17, able to mount the probe 22 and fix the mounting for the entire period of monitoring.

(19) Another embodiment of the present invention, FIG. 6, shows a choke valve 300 in a configuration similar to that depicted in FIG. 4, where the outside diameter of the seat 48 is arranged in a cylindrical shape, but the inner diameter of the body 44 is machined with a smaller diameter. The valve comprising a body 44, a plug 45, a control element or trim 46, flow ports 47 and a seat 48. An ultrasonic probe 40 is located in the position as in FIG. 5.

(20) The shrink fit assembly can be applied to the valve 300 where the outside diameter of the seat 48 is arranged in a cylindrical shape, but the inner diameter of the body 44 is machined with a smaller diameter. The assembly is therefore possible only because of thermal modification of one (or both) of the items 48 and 44 and in particular, by cooling the seat 48, or heating the body 44 to such an extent, that the outer diameter of item 48 is smaller than the inner diameter of item 44 in this transient thermal condition. The cold press fit consists in a similar process described in the above paragraph, but the compensation of the different diameters is obtained by the insertion of the seat 48 from the top cylindrical hole of the body 44 and pressed into position (like in FIG. 4) by the use of a hydraulic press, which elastically and also plastically deforms the components with a permanent hoop stress.

(21) The welding process and the brazing assembly processes can be obtained in different ways, but all these processes are consisting in recovering the assembly gap between the seat and the body by filling it with additional material or by using electromagnetic welding to do it.

(22) Another embodiment of the present invention, FIG. 7, shows a choke valve 400 comprising a body 24, a plug 25, a control element or trim 26, flow ports 27 and a seat 28. The valve also comprises an ultrasonic probe 29 measuring the internal erosion of the trim 26 and in particular the enlarged flow ports 31. This is the part more subject to the erosive action of the controlled fluid inside of the valve, as this is the location, where the high speed and strong vortexes are converted into pressure losses. Therefore, trim 26 is normally the first component to be mostly modified by action of the flow. For this reason, it is more important to measure the erosion of the trim 26 and not the erosion of the plug 25. There are many reasons for being the trim 26 and not the plug 25 the most critical item.

(23) One of these reason is that the wolfram carbide components (and in general ceramic materials) are more worn when impacted at angles around 90 degrees then when impacted at angles of about 45 degrees. Having the plug 25 a wedge with 45 degrees at the bottom (for seating purposes), then this has lower erosion rate factor than the 90 degrees angle of a sharp bend in the trim 26, as illustrated in FIG. 8. Another reason consists in the fact that the outlet speed of the flow at the cage is normally lower, than the speed at inlet and inside of the cage, due to expanding flow areas assigned at each pressure loss in the design of internal components. Also, the plug 25 has generally more stock material for erosion than the trim 26, therefore a premature failure of this last component is going to happen much faster than the first one. For the reasons mentioned above, it is therefore essential to control the evolution of the erosion path and advise the user by detection of distance “c”, as shown in FIG. 8.

(24) FIG. 8 is an horizontal sectional view of the valve represented in FIG. 7. From this view it can be seen the disk stack with sharp angle multistage trim 26. The trim 26 is just an example of the possible combinations of single and multistage configurations. Generally, the multistage trim is obtained by sharp angle curves that are responsible for local pressure loss of the fluid. Such sharp angle curves can be in the horizontal plane (like depicted in FIG. 7), or can also follow the vertical direction of the axis of the trim 26. In any case, it is always possible to position the probe assembly and, in particular, the distance compensator in a way that the erosion path is captured by the modified reflection of the ultrasonic waves, due to the change of internal shape of flow path in the trim 26. According to the embodiment of FIG. 7 and FIG. 8, the continuity for waves transfer through the valve is made by assembling the following components: a holder 34, a gasket 35 and a compensator 36, hold in place by a nut 33.

(25) The difference in measurement “d−c” is an estimation of the entity of eroded material in time and is made by ultrasonic waves 32 reflection time detection.

(26) The alignment of the trim 26 to the ultrasonic probe 29 can be done in different ways: an example is the use of alignment reference pins during assembly, between the compensator 36 and the trim 26. In FIG. 7 the compensator 36 is made with a cylindrical shape and a curved head mating the external radius of the trim 26. Another embodiment can be made by shaping the head of the compensator 36 with a flat surface and shape the trim 26 with a flattened spot, where the measurement is going to take place. In this case, the alignment does not require any pin and is completely automatic.

(27) The compensator 36 can be supported by a holder 34, which is equipped with proper gaskets 5 to contain the pressure inside the valve body. In FIG. 7, the embodiment is represented by the use of O-Rings, but these might be replaced with any other radial gasket made of polymers, rubber, flexible metal or Graphite.

(28) The holder 34 is fixed by a nut 33, to avoid that pressure and vibrations can un-screw the holder and therefore causing a false reading of the ultrasonic waves. The nut 33 can be also replaced by any other unscrewing mechanism, such as glues, applied on the screw between the valve body and the holder 34.

(29) The probe 29 should be fixed in an appropriate position for the entire life of the trim, in order to compare the initial distance “c”, as shown in FIG. 7 and the actual distance “d” at any time in valve life, as a result of the erosion mechanism of the fluid inside the valve. The position, the size, the number and the quality of the ultrasonic probes, as shown in figures attached to the present Patent application, are (of course) purely indicative, as these must be adapted to the need of the user, the type of the application, the model of the valve, etc. . . . . It is therefore possible to put multiple sensing points to a valve, or use a single probe, which position is controlled by a positioning system and moved through multiple points of a valve. For example, the spot distance compensator 36 can be replaced by a longer compensator which covers the entire stroke of the valve and it is able to move vertically along different levels of trim 26 positions. In this way, the ultrasonic measurement calculated as a “spot reading” in a precise position, can be transformed into a full scan of the trim 26 for its entire length.

(30) Even if at least an embodiment was described in the brief and detailed description, it is to be intended that there exist many other variants in the protection scope of the invention. Further, it is to be intended that said embodiment or embodiments described are only example and do not limit in any way the protection scope of the invention and its application or configurations. The brief and detailed description give instead the experts in the field a convenient guide to implement at least an embodiment, while it is to be intended that many variations of the function and elements assembly here described can be made without departing from the protection scope of the invention encompassed by the appended claims and/or technical/legal equivalents thereof.