FI61239C - ANORDNING VENTILER MED VRIDBAR VENTILKROPP - Google Patents

Description

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[] (1) UTLÄGGNINQSSKRIFT 612 39 C Patent granted on 10 06 1932 (^ 5) Patent meddelat (51) Kv.lk?/lnt.CI.3 F 16 K 5/06 FINLAND —FINLAND (21) Nt «nnlh» k * rm «—fW * ttn» fivecnln | 35W71 * (22) Htkumitpilv »- An * eknlnpd« | 09 to 12.7 ^

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Patent- och registerstyrelsen '' Araöktn utltgd och utUkriften pubiktrtd 26.02.82 (32) (33) (31) Requested «tuolkuu * - Bugird priorltut 10.12.73

Sweden-Sweden (SE) 7316611-8 (71) Saab-Scania Aktiebolag, S-5Ö1 88 Linköping, Sweden-Sweden (SE) (72) Sten Göran Stake, Linköping, Per-Arne Emanuel Lundström, Ljungsbro,

Sweden-Sweden (SE) (7U) Leitzinger Oy (5U) Device for valves with rotating valve body -Anordning vid ventiler med vridbar ventilkropp

The following invention relates to a device for valves having a valve member rotatably arranged in the flow passage, the circumference of which consists of a rotational pattern having a primarily spherical shape and arranged in cooperation with a seat member around the flow passage, at least on one side of the valve body made of a hard metallic material and form at least one pair of cooperating sealing surfaces which are pressed against each other and, when rotated around the valve member, perform a rotating-sliding, relative movement providing a high specific contact pressure with each other.

The invention is thus applicable to a long-standing group of shut-off members comprising all shapes of tap valves and rotary flap valves. The invention relates in particular to an important ball valve belonging to this group, in which the spherically shaped jacket surface of the valve member usually rests in contact against two seat rings on both sides of the axis of rotation, having cup-shaped sealing surfaces following the spherical shape of the valve member.

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A long-standing problem with these valves is the incision between the seat surface and the jacket surface. The problem becomes particularly difficult at high operating temperatures, which, when the medium is superheated steam, can rise to 400 ° C and above. No non-metallic sealing material suitable for the stresses present here is known, conventional carbon steels and alloy steels are also unsuitable, because their hardness decreases rapidly as steam temperatures now rise to normal values and the only known solution for this reason has been to produce such well a seat surface as well as a jacket surface made of stellite, which is a carbide alloy on a cobalt chromium base, which gives the parts very high hardness values (above 350 HB) and in said temperature ranges, but which can still be finely machined with high precision.

It has proved impossible to fully determine the causes of sticking in the sealing device of high-quality high-temperature valves. There are a number of variables that work together in a way that is difficult to define and it is not theoretically possible to determine the limit values at which a given valve structure shows a tendency to shear, but these factors must be determined experimentally.

In the case of a ball valve, the question is complicated by the fact that there must be a relatively high specific surface pressure between the valve member and the sealing rings due to the highest working pressure of the valve and the requirement that the valve be completely tight over that pressure range. what is the case with other types of valves is constantly affected between the sealing surfaces of the valve, i.e. also when the valve is opened and closed, whereby the surfaces perform a rotating-sliding, relative movement. For the two sealing surfaces to be operated at 400-500 ° C, this additional stress on the structure means that the risks of entrapment become very high and experience shows that if both surfaces are made of said carbide, stellite, such damage occurs that the valve becomes unusable. For this reason, the ball valve 3 61239 has not been used as a high temperature valve.

The object of the present invention is to provide a device which, in closure members of the type mentioned in the introduction, eliminates the risk of entrapment at least in the most common areas of application. The invention pays particular attention to the improvement of sealing members in currently used types of valves with the aim that their range of use could be increased in a higher temperature range which has hitherto had to be avoided due to the clogging problem.

Thus, an important object of the invention is to increase the critical values for ball valves and the like with regard to steam temperature at high pressures and which have greatly limited or made impossible the use of this type of valve in systems which work with superheated heat. In this connection, it is desired that the means recommended in the invention can be added to a ball valve which has been tried and tested in the present field of application, so that the ball valve can be used in the same basic structure in both its new and previous field of application.

These objects and desires are achieved in that in the valves covered by the invention, one of the two parts which together form a sealing surface pair against the other part on its pressing side is provided with metallic, pure molybdenum liners, preferably thermally bonded to the base material of that part. then forms a sealing surface having a lower hardness than the sealing surface of the second part, so that the lubricating (friction-reducing) effect of the molybdenum liner or liners can be protected from the high temperature combined with the high pressure of the flow medium.

The invention will be described in more detail below with reference to the accompanying drawing, which shows an example of the application of the invention to ball valves.

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Figure 1 is a longitudinal section of a ball valve with two seats and

Figure 2 is a fragmentary view of the same valve showing on a larger scale one solution of the device according to the invention.

The construction shown in the drawing of the invention relates to a ball valve including a valve housing 1, comprising two end pieces 2 projecting in both directions into the central part of the valve housing and having the outermost parts forming the valve connections 3, as threaded connections shown here. Between these there is a flow channel, the cross-section of which is determined by the flange part 4 formed in each end piece and by the seat members located inside the valve. According to the most common construction for ball valves, in the construction example there are two seat members, marked 51 and 511, which in their concentric positions, delimited by fixed guide surfaces 6, reach annularly along mutually parallel planes at an angle to the flow channel.

The central part of the valve flow channel is filled by a valve member 7 pierced by a circular opening 8 connected to a stem 10 by a gripper or other torque transmitting switch 9. This is pivotally mounted on an angle housing 11 of one valve housing containing a sealing housing or the like, a stop member 12 which, in cooperation with a handle 13 non-rotatably arranged at the end of the spindle and supplemented by a handle, determines the pivot position of the spindle and valve body with the valve open and shown in the drawing and the closed state of the valve reached by 1/4 turn and valve the opening 8 of the amplifier must no longer be in any way in connection with the connections 3, which position of the valve member is indicated by broken lines in Figure 2.

The seat members 5, which in the second type of tap valves with a cylindrical or conical tap are equivalent to the cooperating part of the tap hole wall in the valve stem, consist of a metal seat ring 14, a seal IS placed in a conical, annular and annular space which, when the medium is steam, is suitably made of asbestos, as well as a pressure ring 16 which is axially movable in said state behind the seal. Between the pressure ring and the housing flange part, each seat has a disc spring 17 or similar resilient member which is prestressed and transmits a force evenly distributed around the circumference of the seat 16, which on the other hand causes the seal 15 to compress so that no leakage along the guide surface 6 occurs. and the inner hollow space 18 between the seats of the housing is sealed with respect to both ends 3 of the housing, on the other hand that the interacting main parts 51, 7 and 511 of the valve seal are pressed against each other.

As is the case with all types of faucet valves, there is continuous surface contact between said main parts, which are hereinafter assumed to be made of hard metal material, which requires that the jacket surface of the valve member or faucet, denoted 19 here, form a rotationally symmetrical pattern, e.g. around an axis running in that direction. In order to achieve good surface contact, it is also required that the sealing surfaces 20 in both seat rings 14 have a shape closely matched to the jacket surface 19, which means that the two parts acting sealingly in both pairs rest against each other along an unbroken line or surface. that the surface 20 in each pair of sealing surfaces is shaped cup-shaped with the same radius as the radius of the jacket surface 19 and taking into account that the centers of the spherical surfaces at least approximately coincide.

An arbitrary jacket surface element M (see Fig. 2), located so as to contact the seat surface 20 when the valve member is rotated, thus draws a circular path located in the plane X-X perpendicular to the axis of rotation and following the seat surface transversely over it. Clearly, during each closing and opening phase, the surface element M will slide back and forth over the same strip 20 of the surface 20 along this gripping path, while at the beginning and / or end of the same circulation the surface element and the strip are separated from each other.

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During contact, the previously mentioned springs 17 compress the rotating-sliding surfaces relative to each other, a force which helps to seal the surfaces against the lower working pressures present, and a force which is a function of the current pressure drop in the valve. Together, these two external forces provide a surface load on that portion of the relative movement of the surfaces where the valve member moves toward or away from the closed position, and this maximum load generates a specific sealing surface pressure significantly higher than the fluid pressure, which can be assumed to be evenly distributed throughout the seat. the surfaces present have a shape in manufacture which follows exactly a predetermined, geometric shape and if this exact shape can be maintained during use.

It is clear that the geometry of movement described above in a ball valve seal, the main parts of which can be considered rigid in terms of durability, is considerably less favorable than in other types of valves in which the valve member moves at an angle to and away from the valve seat and thus has no sliding, relative movement under high surface pressure. Assuming that the surface element M in Fig. 2 represents a protrusion from this ideal, spherical shape, which in practice may result from a slight ovality or some other small geometric shape defect in the jacket surface, then the surface element The shape defect can, since it moves in the same way each time the valve is guided, leave its mark in the form of a scratch running from one edge to the other in the seat ring 14. In the worst case, such local contact and increase in surface pressure can lead to surface sticking.

Under normal conditions of use, the risk of this type of damage to the ball valve sealing device is reduced by the resilience provided by the spring members 17 and consequently the position of the seat members fits the valve member and minor shape defects are eliminated by maintaining substantially normal sealing surface pressure.

7 61239 However, the use of a tap valve or a ball valve for superheated steam or other media with a similarly high temperature, in which the temperature range up to and above 400 ° C is particularly meant, will, as experience shows, place excessive stresses on the sealing members and despite they are made of high quality valve materials, such as stellite, and with the highest possible dimensional accuracy and surface smoothness, the sliding surfaces are often damaged due to clipping. Such a situation could be expected to result from the complete absence of lubricating oil film from surfaces under such conditions, together with local temperature rises if point contact occurs in the sealing members and raises the surface temperatures of the effect welds together. In order to avoid such damage to the sealing members, one of the two parts 7 and 14 forming the pair of sealing surfaces 19, 201 of the valve is provided with the liners 21, located on the side which is pressed against the other part. The lining consists of high purity molybdenum in metallic form. Molybdenum coating is carried out by a thermal process, primarily by plasma spraying, in which the metal is melted and finely ground in a molten, fine form against a base material, which in this case may be alloy steel, coating by other gas or electric welding methods is also useful, provided that the layer becomes uniform and tight and that it binds well to the parent compound. The lining gets a hardness of about 250 hp.

After the liner 21 is added to the ball valve seat ring or rings, the molybdenum surface is finely machined to meet its shape and surface smoothness requirements for the sealing surface 201. A second sealing surface that will co-operate with the molybdenum liner, i.e. the valve member 7 , is made in the usual way from a stellite or similar material with a hardness of about 400 HV.

According to the invention, with the same basic structure as in a conventional ball valve seal, the valve obtains a pair of sealing surfaces which

Claims (1)

61239 8 also has its sealing capacity and wear and shear resistance in the above-mentioned elevated temperature ranges. The result results in a considerable difference in hardness between the stellite material and the softer molybdenum liner, together with the lubricating effect which the latter gives on the pair of sealing surfaces and which manifests itself as less friction. Although, for manufacturing and economic reasons, it is more advantageous to place a soft liner in the valve body seat member and make the valve ball of a harder material, the opposite placement includes an alternative to implementing the idea of the invention, especially tapered taps with taper holes. The same idea can be considered when applying the invention to reversing flap valves, in which, also due to the construction and manufacturing method, a molybdenum liner can be placed in the valve member or the valve body seat member. Apparatus for valves in which a rotatable valve member (7) is arranged in the flow passage, the circumference of which consists of a rotation pattern of primarily spherical shape and which is arranged in cooperation with the seat passage (51, 511) around the passage, at least on one side of the valve member, to close or open the passage, said cooperating parts are made of a hard metallic material and form at least a pair of cooperating sealing surfaces (19, 201) which are pressed against each other and perform a rotational-sliding relative movement when the valve member (7) is rotated, creating a high specific contact pressure, characterized by that one of the two parts (51, 511 * 7) which together form a sealing surface pair against the other part on its pressing side is provided with metallic liners (21) made of pure molybdenum, preferably heat-sealed. n in the form of a layer connected to the base material of the part in question, which, after fine machining, forms a sealing surface (201) having a lower hardness than the sealing surface of the second part, so that the sealing surfaces of the valve can be