JPS61138805A - Longitudinal joint flange for turbine casing - Google Patents

Abstract

PURPOSE:To keep off a leak of steam out of a flange, by installing an intermediate pressure chamber in a central part on a flange surface of a longitudinal joint flange for a casing of a steam turbine, and interconnecting it to a stage at the downstream side. CONSTITUTION:An intermediate pressure chamber 7 is installed in a central part on a flange surface of a longitudinal joint flange 3 for connecting a high pressure casing 1 to a low pressure casing 2 belonging to a steam turbine, and this chamber is interconnected to a stage at the downstream side via a leading pressure hole 8. With this constitution, internal and external pressure differentials on a contact surface 11 at the low pressure side of the flange 3 are made smaller, thus a leak of steam is preventable from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vertical joint flange of a turbine casing provided with measures to prevent steam leakage.

[Technical background of the invention and its problems] A steam turbine allows high-temperature, high-pressure steam to flow in from the turbine inlet, expands repeatedly in each stage of the turbine, and exchanges the thermal energy of the steam with the rotational energy of the rotor. It is a machine that accomplishes a specific task. For this reason,
Because the steam conditions flowing inside the high-pressure and low-pressure parts of a turbine are significantly different, the casings used in the high-pressure and low-pressure parts often differ in many aspects, such as material, wall thickness, and manufacturing method. . For this reason, in unidirectional flow turbines with a large number of stages, many vertical joint type casings are used, in which the casing is divided into two parts, a high-pressure side and a low-pressure side, and each casing is connected using a W1 joint flange. I am using it.

In FIG. 5 showing a vertical joint flange portion of a conventional casing, a high-pressure casing 1 and a low-pressure casing 2 are connected at an m-joint flange 3 by a vertical joint bolt 4. As for the pressure acting on the vertical joint flange 3, the internal pressure is the steam pressure pa of the steam after passing through the nozzle 59 vane 6. In addition, the external pressure is the pressure p at the outside position of the vertical joint flange 3.
c atmospheric pressure.

Considering the flange tightening effect, the flange opening force that causes steam leakage is determined by the above internal and external pressures Pa and P.
The force due to the differential pressure c and the force due to thermal deformation are acting. Further, the force countering this flange opening force is exerted only on the bolt tightening force of the flange tightening bolt 4. Therefore, if the flange opening force, which is mainly composed of the pressure difference pa-pc between the internal and external pressures acting on the flange, is mixed with the bolt tightening force, steam leaks from the flange.

In addition, even if the bolt tightening force exceeds the flange opening force, the effect of the bolt tightening force is uneven, so there may be some areas where the bolt tightening effect is loose or the machining accuracy of the flange surface is poor. Steam leakage is likely to occur in cases where vertical joints and horizontal joints intersect.

For this reason, when designing the vertical joint flange 3, the designer
The design takes into consideration bolt tightening force and bolt placement optimization to ensure sufficient bolt tightening effects. However, the internal steam pressure P at the normally designed vertical joint position
When a is low, it is around atmospheric pressure, and when it is low, it is about several atmospheres. If the internal pressure at the 1a joint position is equal to or lower than atmospheric pressure, there is no chance of steam leaking to the outside, but if the pressure is higher than atmospheric pressure and the above steam leakage factors are present, steam leakage will occur immediately. there's a possibility that.

From this, if the vertical joint position is set to a position where the internal pressure is below atmospheric pressure, the problem will disappear. However, in reality, due to various structural constraints and reasons such as it being uneconomical to increase the range of the pressure side casing, internal pressure is often designed to be higher than atmospheric pressure, and steam leakage from vertical joint flanges is often avoided. is always a problem.

[Object of the Invention] An object of the present invention is to provide a vertical joint flange for a turbine casing that can prevent steam leakage.

[Summary of the Invention The longitudinal joint flange of a turbine casing according to the present invention comprises:
An intermediate pressure chamber is provided in the center of the flange contact surface of the vertical joint flange, and this intermediate pressure chamber is brought to a pressure almost close to atmospheric pressure using a pressure guiding hole, thereby eliminating the differential pressure on the flange surface and allowing pressure to flow outside the casing. It is characterized by being constructed to prevent steam leakage.

[Embodiments of the Invention] The present invention will be described below with reference to embodiments shown in FIGS. 1, 2, and 3. A steam turbine casing 20 to which the present invention is applied is a high-pressure casing 1 as shown in FIG.
and a low-pressure casing 2 are connected at a vertical joint flange 3 with vertical joint bolts 4. The contact surface of the vertical joint flange 3 on the low-pressure casing 2 side is machined with an intermediate pressure chamber 7 in the form of an annular groove extending all around the circumference, thereby converting the contact surface of the vertical joint flange 3 into a high-pressure side contact surface 10 and a low-pressure side contact surface 11. It's divided. The intermediate pressure chamber 7 is connected to the downstream stage through a pressure introducing hole 8. Here, the groove portion of the intermediate pressure chamber 7 is
As shown in the figure, several pressure-conducting holes 8 are provided around the entire circumference.
One pressure guiding hole 8a of the pressure guiding holes 8 is provided directly below the groove of the intermediate pressure chamber 7 in consideration of drain removal within the groove.

In FIG. 1, the steam pressure at the pressure guiding hole inlet 9 is equal to the pressure Pb in the downstream stage, and because the intermediate pressure chamber 7 has the pressure guiding hole 8, the pressure is the same as the pressure Pb.

Therefore, by providing the pressure guiding hole inlet 9 at a position where the steam pressure is approximately equal to atmospheric pressure, the pressure in the intermediate pressure chamber 7 can be made approximately equal to atmospheric pressure.

According to the present invention, the flange contact surface is a double contact of the high pressure side contact surface 10 and the low pressure side contact surface 11. Here, regarding the low-pressure contact surface 11 from which steam leaks from the flange, the differential pressure between the inside and outside of the flange contact surface becomes equal to zero, so no steam leaks from the vertical joint flange.

Next, in another embodiment shown in FIG. 4, the pressure guiding hole 8 is connected to the air bleed pipe 12, and the pressure in the intermediate pressure chamber 7 is made equal to the bleed air pressure, so that the same effect as described above can be obtained. It is characterized by the fact that it has

[Effects of the Invention] As described above, according to the present invention, the pressure in the intermediate pressure chamber provided at the center of the vertical joint flange can be freely made equal to the pressure in other stages using the pressure guiding hole. Therefore, by setting the pressure in the intermediate pressure chamber to approximately the same as atmospheric pressure, the difference between the inside and outside of the low-pressure side contact surface of the flange can be reduced to approximately zero, and steam leakage from the flange can be prevented. Furthermore, steam leakage from the vertical joint flange can be prevented regardless of the magnitude of the internal steam pressure of the vertical joint flange. Also, from this, the vertical joint flange position can be freely selected, and the degree of freedom in turbine design can be greatly expanded.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a vertical joint flange of a turbine casing according to the present invention, and FIG. 2 is a cross-sectional view taken along line X-X in FIG.
3 is a sectional view showing the entire turbine casing, FIG. 4 is a sectional view showing another embodiment of the present invention, and FIG. 5 is a vertical sectional view showing a vertical joint flange of a conventional casing. It is a diagram. 1... High pressure casing 2... Low pressure casing 3... Vertical joint flange 4... Vertical head bolt 5... Nozzle 6... Vane 7... Intermediate pressure chamber 8...・Pressure hole 9...Pressure hole entrance 10...High pressure side flange contact surface 11...Low pressure side flange contact surface 12...Bleed pipe (8733) Agent: Yoshiaki Inomata, patent attorney (and 1 others)
Figure 1 Figure 2 Figure 4 Figure 5

Claims (3)

[Claims] (1) A vertical joint flange for a steam turbine casing, characterized in that the vertical joint flange for a turbine casing is provided with an intermediate pressure chamber communicating with a downstream stage in the center of the flange surface. (2) The vertical joint flange of a turbine casing according to claim 1, wherein the intermediate pressure chamber is formed by an annular groove provided on the flange surface. (3) The vertical joint flange of a turbine casing according to claim 1, wherein the pressure guide hole of the intermediate pressure chamber is opened to an air bleed pipe.