The present invention relates to a device and a method for a valve intended for pressure and temperature regulation of steam, said device comprising a plug with a skirt provided with drilled holes, such that, as the plug is caused to rise, the holes are successively exposed for the regulated passage of the steam through the valve, and a water-injection arrangement situated downstream of the plug for temperature control of the steam.

Valves of the above-mentioned type commonly used on the market regulate steam pressure by the plug being lift¬ ed, thereby exposing drilled holes in its skirt simul¬ taneously as the valve controls the temperature of the steam by water being injected downstream of the plug with the aid of a separate system. This standard solu- tion functions at a low steam velocity in the valve outlet down to about 8 m/s but this has been found to be a great limitation, since in some cases plants have to work with small steam amounts giving low velocities.

The purpose of the present invention is to provide a device and a method for a valve of the kind mentioned above, the drawbacks existing with the above-mentioned, previously known arrangements being eliminated. Accord¬ ing to the invention, both pressure regulation and temperature control of the steam can be provided at low steam velocities. The characterizing features of the invention are stated in the accompanying claims.

Thanks to the invention, a device and a method for a valve of the above-mentioned type has been provided, which fulfil their purposes in an excellent manner, while the device is cheap to manufacture. By means of

the device and the method according to the invention a solution has been proposed, where the water can be vaporized with the aid of auxiliary steam taken from the high pressure side of the valve. From here the auxiliary steam is regulated by means of the steam plug in the area of its sealing surface, whereby the plug during its opening phase exposes feed means for the auxiliary steam for feeding it to at least one special atomizing nozzle, which is provided downstream of the plug and in which vaporization of the water takes place for temperature control of the low-velocity regulated steam. According to the invention, auxiliary steam can also be fed from the area of the sealing surface of the steam plug upwards through channels in the plug and further through a piping system to the atomizing nozzle or nozzles. When the valve is closed, the plug func¬ tions as a sealing means for this arrangement, since its sealing surface is then enveloped by its seal, thus closing off the distribution channels for the auxiliary steam, and when the plant is used the plug is lifted by means of an actuator for exposing the channels distri¬ buting the auxiliary steam, which can then pass to the place for injection via the atomizing nozzles on the outlet side of the valve. In accordance with the inven- tion, this arrangement eliminates a separate, outer shut-off valve, which has otherwise been necessary.

The invention will now be described below in more detail with the aid of some embodiments and with refer- ence to the enclosed drawings, on which

Fig. 1 shows a schematic, cross-sectional view through a first embodiment of a pressure-regulating valve in accordance with the present invention, this valve including a partly "balanced" steam plug,

Fig. 2 shows, like Fig. 1, a schematic, cross-sectional view of a second embodiment of the valve in accordance with the invention, said valve including an entirely "balanced" steam plug,

Fig. 3 shows, like Figs. 1 and 2, a schematic, cross- sectional view through a third embodiment of the valve in accordance with the invention, said valve comprising an entirely "tight" steam plug.

Fig. 4 shows a schematic side view of the device illu¬ strated in Fig. 1 in an enlarged, partial view, and from which it will be seen how the sealing of the atomizing steam by means of the steam plug takes place.

Fig. 5 shows an enlarged, partial side view of the valve illustrated in Fig. 1 and more precisely how the atomizing steam is distributed through the steam plug and further towards the conduit feeding the steam to the atomizing nozzles, and

Fig. 6 shows an enlarged side view in section of an atomizing nozzle, in which temperature-controlling water is vaporized by means of the auxiliary steam.

As appears in more detail from Fig. 1 and from partial enlargements thereof according to Figs. 4, 5 and 6, all these views illustrate a first, preferred embodiment of the invention, which consists of a valve 1 for the pressure regulation of steam and includes a steam plug 2 with a skirt 3 provided with bores 4, which are successively exposed as the valve is opened for regu¬ lating the passage of steam through the valve 1. The valve 1 also includes a water injection arrangement 5, situated downstream of the steam plug 2 for regulating steam temperature. As appears from Fig. 1, the water injection arrangement 5 comprises both ordinary nozzles

6 for injecting water for temperature control and at least one atomizing nozzle 7 for vaporizing this water by means of auxiliary steam, said nozzles 6, 7 being fed with water via conduits 24 and at least one connec- ting means 25. For small openings of the valve 1, i.e. when the regulated steam has low velocity and small steam quantity and when the velocity of steam at the outlet usually may be below about 8 m/s, the mentioned auxiliary steam is fed from the high pressure side 13 of valve 1 from the sealing surface 8 of the plug 2, such that this steam can be shut off by means of the plug 2 when the valve 1 is closed. The valve is provid¬ ed with at least one means 9 for feeding auxiliary steam through the steam plug to the atomizing nozzle 7. The feed means 9 thus includes an inlet 21 opening out in the sealing surface 8 of the plug 2, and the inlet being shut off when the plug is in its position corres¬ ponding to the "valve closed" state. In the atomizing nozzle 7 the water used in this case for cooling the steam is disintegrated by the auxiliary steam, very effective cooling of the regulated steam being achiev¬ ed. With previously known arrangements, where this type of atomizing nozzle is not used, but only ordinary nozzles 6, erosion is caused in the system at low, regulated steam velocities by the cooling water not being disintegrated by the regulated steam, which is normally the case at high steam velocities but immerges at the outlet of the valve as water droplets, which fall against the wall of the outlet conduit and can then not be vaporized.

According to a first embodiment of the invention illu¬ strated in Fig. 1 the feed means 9 for the auxiliary steam includes at least two distribution ducts 10 extending from outlets 21 up through the plug 2 close to its circumference, said ducts 10 being, via a cham¬ ber 15 above the plug, in communication with conduits

11 connected to the atomizing nozzle 7 at the injection place 12 on the outlet side 14 of the valve 1, on which side a silencer 22 is also arranged. As will appear in more detail from Fig. 4, for a closed valve state the sealing surface 8 of the steam plug 2 contains the mouth of the inlet 21 for the auxiliary steam conducted by the feed means 9. By this arrangement a "partly balanced" steam plug is obtained. When the valve is put into operation the plug 2 is lifted by an actuator 17, and the steam inlets 21 are exposed, thus enabling the steam to pass via the ducts 10 towards the injection place 12 at the outlet side 14 of the valve. According to this arrangement pressure is built up in the en¬ closed volume forming the transport path of the auxili- ary steam. This means that a larger operating force is required for setting the valve than according to an arrangement, where the plug 2 is balanced.

An entirely "balanced" steam plug 2 will be seen from the embodiment illustrated in Fig. 2. Here, sealing off the auxiliary steam takes place in the same manner as with the arrangement illustrated in Fig. 1 and describ¬ ed above. However, distribution of the auxiliary steam takes place in a different way, so that the enclosed volume above the upper side 16 of the plug 2 can be balanced out by means of ducts 18 passing straight through the plug 2. This means that a smaller operating force is required than with the embodiment first de¬ scribed. Distribution of the auxiliary steam according to this embodiment takes place with the aid of a chan¬ nel 20 provided centrally through the plug and its actuator spindle, and opening out above the chamber via an upper part 23 of the actuator 17. The chamber 15 is in constant communication with the downstream side 19 of the plug 2 by means of at least one elongated open¬ ing constituting said centrally situated channel 20.

The embodiment illustrated in Fig. 3 relates to an entirely "tight" steam plug 2, although sealing and distribution of the auxiliary steam take place in exactly the same manner as described above in connec¬ tion with the embodiment illustrated in Fig. 2. The enclosed volume above the upper side 16 of the plug 2 is, however, not connected to any outlet to the down¬ stream side 19, i.e. there can be no steam leakage to the downstream side.

In Fig. 6 there is shown en enlarged, cross-sectional view of an atomizing nozzle 7 used with the valve according to the invention. By using this atomizing nozzle there is obtained effective temperature control of the steam regulated by the valve 1, even for small steam velocities and small steam quantities. Just outside this nozzle the water used for steam tempera¬ ture control is disintegrated by the auxiliary steam fed to the nozzle from the high pressure side of the valve. In the Figure arrows are used to show the paths of temperature-controlling water and auxiliary steam through the valve.

According to the inventive method, at pressure regula- tion and simultaneous temperature control of the steam through the valve, when it operates with small steam quantities and velocities, there is obtained very effective temperature control of the regulated steam. This is enabled since, for small openings of the valve, where the velocity of the regulated steam at the outlet of the valve is below about 8 m/s, the auxiliary steam is taken from the high pressure side of the valve and used for vaporization of the temperature-controlling water, the supply of auxiliary steam being regulated with the aid of the plug 2, such that feed means 9 in the area of the plug sealing surface 8 are exposed during the opening phase of the valve. The means 9 thus

allows the auxiliary steam to pass when the plug moves from its sealed position so that steam can be fed to at least one atomizing nozzle 7, for vaporization of the temperature-controlling water, thus to obtain very effective cooling of the regulated steam.