JPH06212906A - Stress control device for bolt for clamping divided pressure vessel - Google Patents

Abstract

PURPOSE:To provide a control device capable of positively keeping the stresses of bolts for clamping the flanges of a divided pressure vessel, into which high temperature fluid is introduced, below a yield stress. CONSTITUTION:A room-temperature measuring thermocouple 7 and a bolt-temperature measuring thermocouple 8 are attached to a divided pressure vessel in order to measure the temperatures of vertically divided rooms 1 and room-clamping bolts 4 for clamping the rooms 4, respectively. A control device (not shown) is connected to the thermocouples 7, 8 and a high temperature fluid inflow control valve 9 for the rooms 1. The coefficient of linear expansion and the Young's modulus of the rooms are determined as functions of the room-temperatures detected by the room-temperature measuring thermocouple 7. Similarly, the coefficient of linear expansion and the Young' s modulus of bolts are determined as functions of the bolt-temperatures detected by the bolt-temperature measuring thermocouple 8. Thus, the stress of the bolts can be determined. On the other hand, the yield stress of the bolts are determined as functions of the bolt temperatures. The control device controls an inflow control valve 9 so that the difference between the bolt-yield stress and the bolt stress may not be below a specific value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling a stress generated in a tightening bolt for assembling a split pressure vessel such as a two-split casing or a valve chamber of a steam turbine.

[0002]

2. Description of the Related Art As an example of a pressure vessel, a casing of a steam turbine which is vertically divided into two parts and which is integrally fastened with a bolt will be described. FIG. 5 shows the assembled state of the passenger compartment of the steam turbine, and FIG. 6 shows a cross section taken along the line AA of FIG. In these drawings, reference numeral 1 is a vehicle compartment, 2 is a vehicle interior fastening nut, 3 is a washer, 4 is a vehicle interior fastening bolt, 5 is a rotor, and 6 is a flange.

The passenger compartment 1 of the steam turbine is divided into upper and lower parts in a horizontal plane in order to facilitate opening of the rotor 5 and the like housed inside the passenger compartment. The vehicle compartment 1 produced by dividing into two parts is assembled as a pressure vessel by tightening with a vehicle compartment tightening bolt 4 and a vehicle compartment tightening nut 2 installed through holes formed in the flange 6 of the vehicle compartment. A high-temperature and high-pressure working fluid, such as steam in the case of a steam turbine, flows through the interior of the vehicle interior 1 assembled in this way during its operation.

When steam flows into the vehicle interior 1 assembled by tightening the bolts at room temperature, the temperature of the vehicle interior 1 rises. At this time, the temperature change of the vehicle interior 1 is caused by the temperature of the vehicle interior fastening bolt 4. It is shown in FIG. 7 along with the changes. When the steam turbine is being started, the passenger compartment 1 is first exposed to steam, and therefore, as shown in FIG.
Although the vehicle interior temperature shown by the solid line rises faster than the bolt temperature shown by the broken line, the vehicle interior temperature and the bolt temperature become almost equal under steady operation. As described above, a temperature difference occurs between the bolt 4 and the vehicle interior 1 during startup, and the stress of the bolt 4 changes due to this temperature.

The change in the bolt stress σ _B is shown in FIG. Here, the point a indicates the initial bolt stress at the normal temperature T _O , the point b is the maximum at the start point b, and the point c indicates the bolt stress during the steady operation. The value at the point b of this maximum value is determined by the temperature changes of the bolt 4 and the passenger compartment 1 during startup shown in FIG. 7, but if the startup time is short, the temperature difference ΔT between the bolt 4 and the passenger compartment 1 is large. Therefore, the point b becomes larger, but it is necessary to start such that the maximum stress is at least smaller than the bolt yield stress.

For this purpose, it is necessary to know the stress σ _{B of the} bolt 4, and one of the methods for obtaining the bolt stress is as follows.
There is a method in which a strain gauge is attached to the bolt 4 and the strain is measured. However, the high temperature strain gauge used for this is not only expensive, but also the drift amount of the strain gauge at high temperature is several times as large as the strain to be measured as shown in FIG. 9, resulting in poor accuracy and practical application. Not.

For this reason, conventionally, a device has been conventionally used in which the temperature difference ΔT between the vehicle compartment 1 and the bolt 4 is measured and the ΔT is started to be within a fixed value. The problems of this conventional type will be described below. The bolt stress σ _B is approximately

[0008]

[Equation 1]

FIG. 8 shows an example of the bolt stress obtained by the mathematical expression 1. 10 and 11 show examples of the linear expansion coefficient and Young's modulus for obtaining the bolt stress.
Since both determined as a function of temperature, using the symbols in Equation _{1, E F = E F (} T F) linear expansion coefficient and Young's modulus of the passenger compartment and _{bolts, E B = E B (T} B) Here, α _F = α _F (T _F ), α _B = α _B (T _B ) will be expressed.

Here, the change of the bolt stress σ _B when the temperature difference ΔT (ΔT = T _F −T _B ) between the passenger compartment and the bolt which has been conventionally adopted is kept within a certain value (for example, ΔT = 100 ° C.) is shown. 12 shows. Here, T _B = T _F −ΔT = T _F −100
Therefore, if the linear expansion coefficient and the Young's modulus of the passenger compartment and the bolt are calculated, E _F = E _F ( _TF ), E _B = E _B ( _TF −100) α _F = α _F (T _F ), α _B = α _F (T _F −100) and the bolt stress σ _B can be obtained from the above Equation 1 using this.

As is apparent from FIG. 12, when ΔT is set to a constant value (ΔT = 100 ° C. in the example of FIG. 12), ΔT is limited too small in the range where the vehicle compartment temperature T _F is low. That is, the startup time is too long. Conversely, T
_{When F} is high, ΔT is too large. That is, it can be seen that it is necessary to take a longer startup time.

FIG. 12 shows the bolt stress σ _B during actual starting.
An example of the change in is also shown, but it shows that the bolt stress may exceed the yield stress depending on the starting. In other words, if the limit value of ΔT is not changed depending on the temperature of the passenger compartment, it will yield. If the bolt yields, the tightening force of the bolt will decrease and the working fluid inside will leak from the two-divided surface of the pressure vessel. Become.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device capable of reliably maintaining the stress of a bolt for fastening a flange of a divided pressure vessel into which a high temperature fluid is introduced, at a yield stress of the bolt or less. I am trying. Further, the present invention makes it possible to shorten the start-up time by avoiding unnecessarily taking a long start-up time because of concern about bolt stress when the temperature of the pressure vessel is low at the time of starting the apparatus, An object is to provide a stress control device for bolts.

[0014]

In order to solve the above-mentioned problems relating to the bolt stress for tightening the flange of the divided pressure vessel into which the high temperature fluid is introduced, in the bolt stress control device according to the present invention, the temperatures of the divided pressure vessel and the bolt are respectively adjusted. A temperature measuring means for measuring and a stress generated in the bolt from the temperature measured by this temperature measuring means are calculated, and in accordance with the calculated stress, an inflow control valve of the high temperature fluid introduced into the divided pressure vessel is operated, A structure having a control device for keeping the stress of the bolt within the allowable value of the yield stress is adopted.

[0015]

Since the bolt stress control device according to the present invention employs the above-mentioned configuration, if the bolt stress obtained from the respective measured temperatures of the divided pressure vessel and the bolt approaches the yield stress, the inflow control valve for the high-temperature working fluid is controlled. The opening degree of is fixed and the starting time becomes longer, and the bolt stress is kept below the yield stress.

On the other hand, when the temperature of the divided pressure vessel is low, the bolt stress is different from the yield stress, so that the working fluid inflow control valve is opened and the starting time can be shortened.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bolt stress control device for fastening a divided pressure vessel according to the present invention will be specifically described below with reference to the illustrated embodiments. In FIG. 1 showing one embodiment of a bolt stress control device according to the present invention, the same parts as those of the device shown in FIG. 6 are designated by the same reference numerals. FIG. 1 shows an example in which the bolt stress control device according to the present invention is applied to a passenger compartment of a steam turbine as a pressure vessel.

In FIG. 1, reference numeral 1 is a compartment vertically divided into two, 2 is a compartment fastening nut, 3 is a washer, 4 is a compartment fastening bolt, and 6 is a flange. In order to measure the temperatures of the passenger compartment 1 and the passenger compartment tightening bolt 4, a passenger compartment temperature measuring thermocouple 7 is attached to the passenger compartment 1 (flange 6 in the illustrated example), and the passenger compartment tightening bolt 4 has a bolt temperature. The thermocouple 8 for measurement is attached. Further, the working fluid is passed through the inflow control valve 9 to the passenger compartment 1
Is flowing into. A control device (not shown) is connected to the thermocouples 7 and 8 and the inflow control valve 9.

An example of the control function of this control device is shown in FIG. According to FIG. 2, the vehicle interior temperature T _F is measured from the thermocouple 7, and the linear expansion coefficient α _F and the Young's modulus E _F of the vehicle _interior are obtained as a function of the measured temperature. Similarly, the bolt temperature T _B is measured from the thermocouple 8, the linear expansion coefficient α _B and Young's modulus E _B of the bolt are obtained as a function of the measured temperature, and the bolt yield stress σ _Y is also a function of T _B. Desired. If α _F , E _F , α _B , and E _B are obtained, then from Equation 1, T
_The bolt stress σ _B is determined as a function of _F and T _B.

There is a difference Δ between the bolt yield stress σ _Y and the bolt stress σ _B obtained here (5 kg / mm ^{2 in} the example of FIG. ² )
If it is larger, the inflow control valve 9 is opened and the activation is continued. Δ
If it is smaller than a certain value, the bolt stress σ _B approaches the bolt yield stress σ _Y , so that the opening degree of the inflow control valve 9 is held (fixed) and the start is temporarily stopped (held) until σ _B becomes smaller. When Δ becomes negative, the inflow control valve 9 is closed and the activation is stopped. Since the circuit configuration of the control device for calculating the stress and the like and controlling the control valve 9 described above can be appropriately designed by those skilled in the art, detailed description thereof will be omitted.

FIG. 3 shows an example of activation by this control means. According to FIG. 3, by keeping the opening of the inflow control valve during startup to temporarily hold the rotation speed or the load (both are shown in the example of FIG. 3) rise, the temperature rise in the passenger compartment can be suppressed. It is possible to prevent excessive bolt stress. As a result, as shown in FIG. 4, the bolt stress σ _B during startup can be controlled without exceeding the bolt yield stress σ _Y.

The device according to the present invention has been specifically described above based on the illustrated embodiment, but it goes without saying that the present invention is not limited to this embodiment. For example, in the illustrated one, the split stress container is shown divided into two, but the device according to the present invention may be applied to a pressure container divided into three or more.

[0023]

As described above, the stress control device for a bolt for tightening a divided pressure vessel according to the present invention includes temperature measuring means for measuring the temperature of the divided stress vessel and the temperature of the bolt, respectively. By operating the inflow control valve of the high temperature fluid introduced into the pressure vessel according to the calculated stress generated and the calculated stress, since it has a control device for keeping the stress of the bolt within the allowable value of the yield stress, According to the device according to the present invention, by controlling the high temperature fluid introduced into the pressure vessel, the stress of the bolt fastening the divided pressure vessel can be controlled to be smaller than the bolt yield stress even during start-up, and the bolt yields. The working fluid is prevented from leaking from the dividing surface of the pressure vessel.

Further, since the inflow control valve is controlled according to the bolt stress, it is possible to avoid unnecessarily lengthening the starting time when the passenger compartment temperature is low, which contributes to shortening the starting time.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a steam turbine casing to which an apparatus according to the present invention is applied.

FIG. 2 is a block diagram showing a control function in one embodiment of the stress control system according to the present invention.

FIG. 3 is a diagram showing temperature changes in a vehicle compartment and bolts when the present invention is implemented.

FIG. 4 is a diagram showing a change in bolt stress when the bolt stress control device according to the present invention is adopted.

FIG. 5 is a perspective view of a cabin of a steam turbine as an example of a pressure vessel.

6 is a sectional view taken along the line AA of FIG.

FIG. 7 is a diagram showing an example of temperature changes of a conventional passenger compartment and bolts to which the present invention is not applied.

FIG. 8 is a diagram showing a conventional bolt stress.

FIG. 9 is a diagram showing characteristics of a high temperature strain gauge according to temperature.

FIG. 10 is a diagram showing an example of linear expansion coefficients of a passenger compartment and a bolt.

FIG. 11 is a diagram showing an example of Young's modulus coefficients of a passenger compartment and a bolt.

FIG. 12 is a diagram comparing a bolt stress during starting and a bolt yield stress in a conventional device.

[Explanation of symbols]

 1 Cabin 2 Nut 3 Washer 4 Cabin tightening bolt 5 Rotor 6 Flange 7,8 Thermocouple 9 Inflow control valve

Claims (1)

[Claims] 1. A device for controlling the stress of a bolt for tightening a flange of a divided pressure vessel into which a high temperature fluid is introduced within an allowable value, and temperature measuring means for measuring the temperature of the divided pressure vessel and the temperature of the bolt, respectively. The stress generated in the bolt is calculated from the temperature measured by, and the inflow control valve of the high temperature fluid is operated according to the calculated stress, and the control device keeps the bolt within the allowable value of the yield stress. A stress control device for the bolts that tighten the divided pressure vessel.