JPS6038526B2 - Main steam stop valve cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling device for a main steam stop valve in a steam turbine.

The steam power station that makes up the conventional Rankine cycle is the first
As shown in the figure, water is supplied to the boiler 2 by a water supply pump, which generates steam, and this steam is sent to a steam turbine 6 directly connected to a generator 5 through a main steam stop valve 3 and a steam control valve 4. The steam that has completed its work in the steam turbine 6 is condensed in a condenser 7, and is then returned to the water supply pump 1.

In addition, the thermal efficiency of the steam power station mentioned above is as shown in the graph of Figure 2, where the vertical axis shows the thermal efficiency 7 of the steam power plant, and the axis shows the inlet steam hothouse. The factor is pressure P.As is clear from the graph in Fig. 2, the thermal efficiency of the steam power station is better as the inlet steam pressure P and inlet steam temperature t are higher. Note that the curve a shown by the dotted line in FIG.
As shown in the figure, the relationship between the inlet steam pressure p, the inlet steam temperature, and the exhaust chamber dryness x is
When x falls below a certain level, significant erosion by water droplets occurs in the low pressure section of the steam turbine, so it is desirable to maintain the dryness x of the exhaust gas at a high level.

In this way, increasing the thermal efficiency of a steam power plant can be achieved by increasing the steam turbine inlet steam pressure p and inlet steam t, but increasing only the inlet steam pressure p will relatively increase the turbine exhaust Since this results in a decrease in the dryness x of the chamber, it is necessary to simultaneously increase the inlet steam temperature.

On the other hand, the reheat cycle of a steam power plant eliminates the above-mentioned decrease in exhaust chamber dryness, and this is a cycle in which steam is extracted from the middle of the expansion of the steam turbine and sent to the boiler for reheating. However, according to such means, not only the dryness x of the exhaust chamber increases, but also the thermal efficiency increases, and the output per the same steam flow rate can be increased. On the other hand, the graph shown in Fig. 4 shows the relationship between the steam power plant efficiency and the inlet steam pressure p when the reheated steam temperature of the single-stage reheat cycle is reheated to the inlet steam temperature t. be. As is clear from the graph in Figure 4,
Although the means to increase the efficiency of a steam power plant have been theoretically clarified, in the conventional technology, in a subcritical pressure plant, the inlet steam condition of the steam turbine is 169 k9/min, Temperature 538:00, resteam temperature 53
The temperature is about 8℃, and in a supercritical pressure plant, the inlet steam pressure is 2
The reason why the overflow temperature of 46k9′ was limited to 538°C and the re-steam pressure temperature 56 to about o was due to the rotor that constitutes the steam turbine.
This is caused by heat-resistant materials such as blades, nozzles, and turbine casings (main body).

In particular, the material used for the casing (main body) of the main steam stop valve has increased high-temperature strength by adding chrome-molybdenum (Cr-M), and the material surface is unstable due to the addition of chrome-molybdenum. In order to suppress this phenomenon, a steel material of 1.2$r-1-0.25V, which is an alloy steel added with vanadium (V), is widely used. However, the limit temperature of the cast steel used for the casing (main body) of the main steam stop valve is approximately 56,600 ℃, and although the addition of vanadium is effective in suppressing the instability of the material surface, However, the addition of vanadium has drawbacks such as increased tendency to crack during welding.

In this way, the main valve bodies of the conventional main steam stop valve 1 and main steam control valve 0 have poor workability and jointability during welding even if heat-resistant and pressure-resistant metal materials are used. There are drawbacks such as.

On the other hand, as shown in FIG. 5, the main steam stop valve 1 as a conventional main valve and the control valve 1 are integrally constructed by welding.

That is, as shown in FIG.
A valve seat 14 is provided in the main body (casing) 13 of the main steam stop valve 1, which is equipped with an inlet 11 and an outlet row 2 connected to The lid body 16 is fixed to the upper entrance part 13a of the main body 13 with a bolt 17, and the lower part 13b of the main body 11 is fixed.
The guide member 18 is provided close to the valve seat 14 and does not fall off, and furthermore, the guide member 1
A plurality of bushes 19a, 19b, 19 divided into 8
A valve rod 20 is installed in each of the pushers 19a, 19b, and 19c, and a valve body 21 is installed at the upper end of the valve rod 20.
is provided so as to be placed on the upper seat 14, and,
An operating member (not shown) is connected to the lower end of the valve body 21, and an upstream leak-off pipe 2 is connected to the lower end 13b of the main body 13.
2 and a downstream side leak-off pipe 23 are provided so as to be suitable for each push 19a, 19b, 19c of the guide member 18, and a steam control valve is provided at the outlet 11. It is something.

In addition, the steam control valve 0' is connected to the connecting port 26 of the main frame body 25 provided with the discharge port 24 to the outlet port 12 by welding, and a lid body is attached to the upper closing portion 25a of the main frame body 25. A guide member 27 that also serves as
A plurality of bushes 28a, 28b divided into inner parts are equipped with iron, a valve rod 29 is slidably mounted in each pusher 28a, 28b, and a valve body 30 is attached to the inner end of the valve rod 29. A drive lever 32 is pivotally connected to the upper end of the valve rod 29 by a support shaft 33, and an upstream leak-off pipe 3 is attached to the guide member 27.
4 and the downstream side leak-off pipe 35 by pushing each of the above-mentioned pushes 28a.
, 28b.

Therefore, high-pressure steam from the boiler 2 flows into the main body 13 from the inlet 11 of the main steam stop valve 1, flows from the strainer 15 of the main body 13 through the valve body 21, and is flow-controlled to the valve seat 1.
It is transferred to the outflow row 2 through the valve hole 14a of No. 4.

Further, the steam flows into the main frame body 25 from the supply port 26 of the steam control valve, the flow rate is controlled by the valve body 30 of the main frame body 25, and flows out from the valve hole 30 of the valve seat 31 to the discharge port 24. It has become. On the other hand, each push 19 of the steam stop valve 1
Upper leak-off pipe 22 flowing out from a, 19b, 19c
Steam flows out to a steam header as a source of steam for sealing the gland of a steam turbine (not shown), and steam in the lower leak-off pipe 23 is supplied to a gland steam condenser.

Note that the low-temperature steam in the upper and lower leak-off pipes 34 and 35 flowing out from each push 28a and 28b of the steam control valve 0 is
It is constantly being drained to each connection line (not shown).

However, the main steam stop valve mentioned above
When opening and closing the valve under conditions of high temperature, the valve holder 20
Since the leak-off pipes 22 and 23 are configured to prevent IJ leaks from occurring due to It is difficult to always cool the main body 13 to the allowable limit temperature of the material in that state.

In view of the above-mentioned points, the present invention makes it possible to maintain the material constituting the main body of the main steam stop valve 1 as is and distribute the low temperature leak steam of the steam control valve 0 to each cooling hole of the main body. - This main body is cooled with overflow steam to reduce the occurrence of thermal stress, thereby preventing cracks and damage to the main steam stop valve body, and also reducing the overall valve equipment. A cooling device for a main steam stop valve 1 is provided for the purpose of improving its health.

Hereinafter, the present invention will be described with reference to an illustrated embodiment.

In addition, the same reference numerals are attached to the same members as those of the constituent parts of the present invention in the description. 5 to 7, reference numeral 1 denotes a main steam stop valve connected to the boiler 2, and a main body 13 of the main steam stop valve 1 includes a steam inlet row 1 and an outlet 12.
A valve seat 14 is installed inside the main body 13.

A cylindrical strainer 15 is attached to the green outer circumference of the valve seat 14, and a lid 16 is fixed to the upper entrance portion 13a of the main body 13 with each bolt 17. Further, as shown in FIG. 7, each twill bolt 17 is provided with a center hole 17a, which is connected to each leak-off pipe 34 of the steam control valve 0,
35 can be supplied with cooled steam. Furthermore, a large number of cooling holes 36 are formed at regular intervals in the main body 13, and each of these cooling holes 36 is connected to the flow of the main body 13, as shown in FIG. It is adapted to fit into each recovery header 37 attached to the outer periphery of the inlet 11 and outlet 12. On the other hand, a ring-shaped distribution header 38 is connected to each center hole 17a of each of the tightening bolts 17 via each pipe 39, and the header 38 to this distribution header 38 is connected to the above-mentioned steam control valve 0. tube 3
4.

Further, a large number of cooling holes 40 are bored at regular intervals in the lower part of the main body 13, and one end of each cooling hole 40 is not ring-shaped and is connected to the distribution header 41 through each conduit 42. connected. Furthermore, this distribution header 41 is connected to the lower leak-off pipe 35 of the steam control valve D,
The cooled steam is supplied from this lower leak-off pipe 35 to the distribution header 41. Further, the ends of the cooling holes 40 are provided so as to fit in with each of the recovery headers 37. Incidentally, the barrels 37 are connected to each collecting pipe 43 by respective collecting pipes 43. Therefore, high-temperature, high-pressure steam from the boiler 2 flows into the main body 13 from the inflow row 1 of the main steam stop valve 1, flows through the strainer 15 of the main body 13 and is controlled in flow rate by the valve body 21, and is controlled by the valve hole of the valve seat 14. 14a to the outlet 12.

Further, the steam is supplied to the main frame body 2 from the supply port of the steam control valve 0.
5, the flow rate is controlled by the valve body 30 of the main frame body 25, and flows out from the valve hole 30 of the valve seat 31 to the discharge port 24. On the other hand, the low-temperature steam in the upper and lower leak-off pipes 34, 35 flowing out from each push 28a, 28b of steam control valve 0 flows from each distribution header 38, 41 to each conduit pipe 39, 42.
and into each cooling hole 36,40.

In this step, the low-temperature steam exchanges heat with the main body 13 whose temperature is rising, thereby cooling the main body 13. After completing the work, the steam is collected in each distribution header 37 and then transferred to each collecting pipe 43.
It is designed to be leaked through. The steam in the upper and lower leak-off pipes 22 and 23 of the steam stop valve 1 is
It is not used during normal operation because it does not leak. As described above, according to the present invention, a large number of cooling holes 36, 40 are bored at regular intervals in the main body 13 of the main steam stop valve 1 equipped with the inlet 11 and the outlet row 2. Each cooling hole 36,
40 is connected to the distribution header 38, 41, and the leak-off pipe 3 of the steam control valve is connected to the distribution header 38, 41.
4 and 35 are connected to each other, and the other side of each of the cooling holes 36 and 40 is connected to the recovery header 37, thereby reducing thermal stress due to temperature difference between the inner and outer surfaces of the main body 13 and reducing fatigue caused by material beams. In addition, even if conventional materials are used, it is not only possible to supply steam at a higher temperature than conventional ones, but also to improve the integrity of the entire equipment. Can be done.

[Brief explanation of the drawing]

Figure 1 is a system diagram of the steam power station that constitutes the ranking cycle, Figures 2 to 4 are graphs showing the relationship between inlet steam temperature, thermal efficiency, and inlet steam pressure in the steam power station, and Figure 5 is the conventional 6 is a sectional view of the main valve including the main steam stop valve and the steam control valve, FIG. 6 is a perspective view of the cooling device for the main steam stop valve according to the present invention, and FIG. 7 is an enlarged sectional view of the tightening bolt of the present invention. be. 11... Inlet, 12 Outlet, 13... Main body, 34
...Upper leak-off pipe, 35...Lower leak-off pipe, 36...Cooling hole, 37...To be recovered, 38.
...Distribution header, 40...Cooling hole, 41...Distribution header. Multi-wing family 2 drawings 3 drawings 'Old 4 drawings * lacquer drawing 6 drawings

Claims (1)

[Claims] 1. A main steam stop valve having an inlet and an outlet, with a number of cooling holes formed at regular intervals, and one end of each cooling hole connected to a distribution header. A cooling device for a main steam stop valve, characterized in that a leak-off pipe of a steam control valve is connected to the distribution header, and the other end of each of the cooling holes is connected to a recovery header. 2. The main steam stop valve cooling device according to claim 1, wherein a portion of each cooling hole is communicated with a center hole of each tightening bolt.