JP2799862B2 - High-temperature flange fastening structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a flange joint portion of a container or a pipeline, a flange joint, or a plate joint portion of a structure.
The present invention relates to a fastening structure of a flange whose temperature rises after fastening, and more particularly to a fastening structure of a high-temperature flange whose fastening force does not decrease even when the temperature of a fastening bolt or the like together with the flange rises. (Prior Art) Generally, when a flange such as a flange joint portion of a container or a pipeline, a flange joint, or a plate joint portion of a structure is fastened by bolts and nuts, measures are taken to prevent a decrease in fastening force. There is a need to. At the beginning of the fastening, the bolt is elastically stretched, the fastened flange and washer are elastically compressed, and the contact pressure is not applied to the thread of the meshed nut. However, in some cases, bolts or flanges may expand or contract plastically, or at the moment an impact force is applied from the outside, the contact pressure of the threads may decrease and the nut (or bolt) may rotate. This is because the loosening and the fastening force are reduced. Therefore, conventionally, a reduction in the fastening force has been prevented by using the following fastening structure for the above-described flange. a) A fastening structure in which two nuts are overlapped (a so-called double nut), a locking pin is passed through a slot of a bolt using a nut with a groove, or a special nut for locking is used. These mainly prevent the nut from rotating, thereby preventing a decrease in the fastening force. b) A fastening structure in which spring washers, toothed washers and the like are sandwiched. These mainly secure the contact pressure of the thread by compensating for the above-mentioned plastic expansion and contraction of the bolt and flange by the elastic displacement of the washer. Such a structure has been widely applied to a joint portion by a bolt and a nut, and has been similarly employed in a fastening portion of a flange where the temperature rises after fastening as described above. (Problems to be Solved by the Invention) The conventional flange fastening structures a) and b) described above.
However, when the temperature of the fastening portion including the flange and the bolt rises after the fastening, there is a problem in the following points. That is, when the temperature of the fastening portion rises, if the elongation of the bolt due to thermal expansion is greater than the thickness direction of the workpiece, such as a flange, a washer, and a gasket, the fastening is performed by any of the fastening structures described above. Weakness,
Or it becomes zero. In the structure a), even if the nut is not rotated, the expansion is performed as described above due to the thermal expansion, and at the same time, the fastening force becomes almost zero.
There is a gap between the objects to be fastened between the nuts. on the other hand,
In the structure b), even if the elongation occurs as described above, the fastening force does not immediately disappear within the range of the elastic displacement of the washer, but the fastening force is greatly reduced. When acting, a gap is formed between the objects to be fastened, or when the fastening portion vibrates, the nut (or bolt) rotates and the fastening force may become zero. Such a phenomenon is caused when the expansion due to the thermal expansion of the bolt exceeds that of the work to be fastened, as described above. Specifically, for example, the linear expansion coefficient of the bolt is larger than that of the flange or the washer. In some cases, the temperature distribution of the fastening portion is not uniform, and the temperature of the bolt may be higher than the temperature of the flange or the washer. If the fastening force of the flange decreases, the external force applied to the flange acts on the bolt as an eccentric load, which may cause the bolt to break.In containers and pipelines, the sealing performance will deteriorate, and the internal fluid will leak, or extremely In such a case, the rotation of the nut may progress, the bolt may come off, and the flange may come off, leading to a serious accident. (Object of the Invention) The present invention has been made to solve the above-mentioned problems, and the temperature of a fastening portion including a flange and a bolt rises after fastening by simply adding a simple part and fastening the flange. It is an object of the present invention to provide a high-temperature flange fastening structure in which the fastening force does not decrease even in such a case. (Means for Solving the Problems) The gist of the present invention for solving the above-mentioned problems is that, for a fastening structure of a flange having a temperature rise after fastening, a structure of a head of a fastening bolt and a nut is used. Between the flange and the gasket to be fastened, a sleeve made of stainless steel or nickel steel having a larger linear expansion coefficient than the bolt, and a sleeve made of low-carbon steel, which is easy to cut gas, are sandwiched between the heads of the fastening bolts. Part is long in the direction perpendicular to the axial direction of the bolt (that is, horizontally long), and the flange on which the head is engaged is provided only when the through part is in a certain direction. That is, a bolt hole to be inserted is provided. (Operation) According to the high-temperature flange fastening structure of the present invention, a sleeve having a large linear expansion coefficient is sandwiched between the head of the fastening bolt and the nut together with the flange, washer, gasket, and the like as the workpiece. Therefore, when the temperature of the fastening portion rises after the fastening, the object to be fastened expands in the thickness direction more than the elongation of the fastening bolt due to thermal expansion, so that the fastening force of the flange by the bolt does not decrease. In addition, a sleeve made of a material that is easy to cut gas is inserted between the bolt head and the bolt hole of the flange on which the bolt is engaged. Since the bolts are inserted into the bolt holes, the fastening can be easily released even when the nut cannot be turned due to foreign matter biting into the screw portion or the like. After gas cutting the latter sleeve, the bolt is slightly turned (along with the nut) so that the head is oriented so that it can be inserted into the bolt hole. This is because the union is broken. Note that a sleeve made of stainless steel or nickel steel is used as a sleeve having a large linear expansion coefficient, and a sleeve made of low carbon steel is used as a sleeve that is easy to cut gas. Based on the mechanical strength and heat resistance properties of these materials, the fastening structure of the invention exhibits a considerably high fastening force and withstands thermal loads. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view of a converter and a hood having a flange fastening structure according to an embodiment of the present invention. Converter A
Is a molten metal container for refining pig iron obtained in a blast furnace or the like into steel. A large amount of high-temperature gas (mainly CO) is generated during refining. The hood B is seated at the mouth and communicates with the exhaust gas duct B11. Hood B is a main hood B1 suspended above the furnace opening,
The lower flange B21 of the skirt B2 is fastened to the furnace opening flange A1 of the converter A with the gasket A4 interposed therebetween. During refining, exhaust gas duct B11
Except for the connection part, the internal space A2 of the converter A and the hood B is sealed, and the main hood B1 and the skirt B2 are connected so as not to be separated (not shown). When the hood B is raised, an upward force (levitation force) is generated in the hood B, and the levitation force acts on a fastening portion between the lower flange B21 and the furnace port flange A1. FIG. 2 (a) shows the details of the fastening portion. The lower flange B21 is suspended by a cylinder (not shown) from a member on the main hood B1 side as a skirt B2 together with the upper flange B23, the flexible sleeve body B22, and the connecting tool B24 as a skirt B2. Before starting, the gasket A4 is lowered as shown and mounted on the furnace opening flange A1.
Is fastened to the furnace opening flange A1 using the fastening bolt 1 and the nut 2. In this embodiment, a sleeve 3 made of a material having a larger linear expansion coefficient than the bolt 1 and a sleeve 4 made of a material easy to cut gas are loosely fitted to the bolt 1 in advance, and when fastening, These are
Together with the two flanges A1 and B21 and the gasket A4, it is configured to be sandwiched between the head 1a and the nut 2. In addition, as shown in FIG.
1a is formed in a horizontally elongated rectangular shape, and is inserted through a bolt hole A1a drilled in a rectangular shape slightly larger than the head 1a, and 9
If it is turned 0 °, it can be locked to the furnace opening flange A1. Reference numeral 10 shown in FIG. 2 (a) is a fastening device for the bolt 1, which can hold the bolt 1 at all times, move up and down, and rotate, so that the flange A1,
It is a device for fastening (or releasing) B21. That is, the fastening device 10 is a socket that holds the bolt 1 by fitting and rotating the nut 2 and locking the lock nut 5.
11, a universal joint 12 and a hydraulic motor 13, which have a function of being moved up and down together with the base plate 14 by an elevating device (not shown) mounted on the lower flange B21. Before the converter A starts refining, as described above, the lower flange B21 and the furnace port flange A1 are fastened by the bolt 1 with the gasket A4 interposed therebetween, and the procedure is as follows. While the lower flange B21 is raised, the bolt 1 is raised by the fastening device 10, and the head 1a is housed in the rectangular recess B21a, but the lower flange B21 is in the position shown in FIG. Then, the bolt 1 is lowered by the fastening device 10, and the head 1a is inserted into the rectangular bolt hole A1a of the furnace opening flange A1. After this, the motor 13 of the fastening device 10
When the nut 2 is turned to rotate the bolt 2, the bolt 1 rotates together and the head 1a comes into contact with the convex portion A11a of the stopper plate A11 on the lower surface of the furnace port flange A1, and the nut 2 subsequently rotates and descends, thereby fastening. Is completed. At this time, the sleeve 3 loosely fitted to the bolt 1
And 4 are sandwiched between the upper surface of the sleeve seat B21b of the lower flange B21 and the lower surface of the nut 2, so that the fastening force by the bolt 1 and the nut 2 is reduced by the furnace port flange A1 and the gasket A.
4, acting on the lower flange B21, the sleeves 3 and 4. Even if the above-mentioned fastening is performed at normal temperature (20 ° C.), the converter A and the hood B receive radiant heat and conductive heat from the hot metal (molten steel) and exhaust gas in the furnace during refining. The temperatures of the furnace port flange A1, the gasket A4, the lower flange B21, the sleeves 3, 4, the bolts 1 and the nuts 2 all rise almost uniformly to about 100 ° C.
The above components thermally expand due to such temperature rise. However, since the sleeve 3 sandwiched between the head 1a of the bolt 1 and the nut 2 has a higher linear expansion coefficient than the bolt 1, There is no gap between the objects and no reduction in the fastening force. On the other hand, after converter A refined several times, the temperature of the components
When the temperature is about 100 ° C., no further thermal expansion occurs after the fastening, so that the fastening force does not decrease. Here, the change in the fastening force due to the above temperature rise is
Let's examine it quantitatively. In this embodiment, the initial fastening is performed at room temperature, and the tension of the bolt 1 (fastening force) is 6000 kg.
During the refining of converter A,
As the temperature rises to 0 ° C., 2000 kg of tension acts on one bolt 1 due to the maximum buoyancy of the hood B due to the gas pressure in the furnace. All components of the fastening portion are made of low carbon steel except that the sleeve 3 is made of 18-8 stainless steel and the gasket A4 is made of a composite material containing ceramic fiber. Their thickness (axial dimension; t: mm; see Fig. 2 (a)) and coefficient of linear expansion (α: 1 / ° C; average value of 20 to 100 ° C)
Is shown below. Furnace opening flange _{A1: t 1 = 60, α} 1 = 1.21 × 10 -5 Gasket _{A4: t 2 = 20, α} 2 ≒ 0 lower flange _{B21: t 3 = 65, α} 3 = 1.21 × 10 -5 Sleeve 3: t ′ ₁ = 185, α ′ ₁ = 1.67 × 10 ^-5 Sleeve 4: t ′ ₂ = 70, α ′ ₂ = 1.21 × 10 ^-5 Also, the distance l between the head 1a of the bolt 1 and the nut 2
₀ (mm), the modulus of longitudinal elasticity E ₀ (kg / mm ² ), effective area A ₀ (mm ² ), and coefficient of linear expansion α ₀ (1 / ° C.)
It is as follows. l ₀ = t ₁ + t ₂ + t ₃ + t ' ₁ + t' ₂ = 400, E ₀ = 2.1 × 10 ⁴ , A ₀ = 2000, α ₀ = 1.21 × 10 ^-5 The temperature range ΔT = 100−20 = 80
(° C.). The free extension amount Δl of the bolt-to-face distance l ₀ of the bolt 1 due to thermal expansion is: Δl = ΔT × ₁₀ × α ₀ = 0.3872 (mm) On the other hand, the furnace port flange A1 and gasket A4 due to thermal expansion
Expansion amount Δt of the total thickness of the lower and lower flanges B21
Δt = ΔT × Σ (t _i · α _i ) = 0.121 (mm) That of the total thickness of the sleeves 3 and 4 Δt ′ is: Δt ′ = ΔT × Σ (t ′ _i · α ′ _i ) = 0.31492 (M
m), so that Δt + Δt ′ = 0.35992 ≧ Δl = 0.3882. That is, since the elongation in the thickness direction of the object to be fastened due to the free expansion is equal to or greater than the elongation of the bolt 1, the fastening force by the bolt 1 does not decrease but rather increases. In this case, the object to be fastened restrained by the bolt 1 is partially prevented from free extension, and the bolt 1 is stretched in the opposite direction, and both have the following common extension Δλ. Δl ≦ Δλ ≦ Δt + Δt ′ When the fastening force of the bolt 1 increases due to a rise in the temperature of the fastening portion, it is necessary to prevent the occurrence of excessive tension in the bolt 1 and to prevent the bolt 1 from breaking. In this embodiment, when the converter A starts refining after the flange portion is fastened with the bolt 1, the gas pressure in the furnace space A2 rises and fluctuates. Works. Therefore, the condition under which the initial fastening force does not decrease due to the temperature rise and the bolt 1 can be used safely is that the following two expressions are simultaneously satisfied: 0 ≦ ΔF... F ₀ + ΔF + F ₁ ≦ A ₀ × σ _a. . Here, F ₀ : initial fastening force (tensile force) (at 20 ° C.) (at 20 ° C.) of bolt 1 (per bolt) (ΔF): increase in tension of bolt 1 due to temperature rise (kg), ie, stress / strain From the relationship, ΔF = A ₀ × E ₀ × (Δλ−Δl) / l ₀ F ₁ : An external force acting between the furnace opening flange A1 and the lower flange B21 (here, the lifting force of the hood B. The maximum value is applied. Do)
Σ _{a is} the allowable stress of the bolt 1 (kg / mm ² , a value that takes into account the yield point stress of the material of the bolt 1 and the safety factor). The equation is clearly satisfied from the above-described equation of ΔF ≦ Δλ and ΔF described above. The value of Δλ is determined accurately in connection with not only the bolt 1 but also the longitudinal modulus of elasticity and the cross-sectional area of each workpiece.
As described above, since Δλ ≦ Δt + Δt ′, the value of ΔF does not exceed A ₀ × E ₀ (Δt + Δt′−Δl) / l ₀ in any case. That is, a value in the range of ΔF ≦ 2000 × 2.1 × 10 ⁴ × (0.121 + 0.31492−0.3872) / 400 = 5120 (kg). In the present embodiment, the allowable stress sigma _a of the bolt 1 made of a low carbon steel is 10 (kg / mm ^2), the initial fastening force F ₀ 6000
(Kg), because the tension F ₁ acting on one bolt 1 by the maximum buoyancy of the food B by gas pressure is 2000 (kg), the left side F ₀ + [Delta] F + F ₁ expression, 6000 + 5120 + 2000 = 13210 The (kg) Since the right side A ₀ × σ _a is 2000 × 10 = 20000 (kg), the expression is satisfied. As discussed above, in the flange fastening structure of this embodiment, it is confirmed that the initial fastening force does not decrease due to the temperature rise, and that the bolt 1 is used safely within the allowable stress. When the converter A finishes the refining, the converter A tilts the furnace body for tapping, so the lower flange B21 is connected to the furnace port flange A1.
And the skirt B2 needs to be raised. To release the fastening between the lower flange B21 and the furnace opening flange A1, use the fastening device 10 to loosen the nut 2 by turning the nut 2 in the opposite direction to that at the time of fastening, and then pull up the bolt 1 to the original position. It should be left. When the nut 2 is loosened, the head 1a of the bolt 1 comes into contact with the protrusion A11a of the stopper plate A11, and the rotation stops in the direction matching the rectangular hole A1a of the furnace opening flange A1. No problem when lifting. In the event that rotation of the nut 2 becomes impossible due to, for example, a thread caught by a foreign matter, the fastening can be released by burning off the sleeve 4 that is easy to cut gas. The fastening structure of the high-temperature flange according to the present invention is not limited to the above embodiment, but may be implemented as follows, for example. That is, a) The material of the sleeve 3 shown in the embodiment is not limited to 18-8 stainless steel as long as it has a larger linear expansion coefficient than the fastening bolt. , Stainless steel, nickel steel, copper alloy, aluminum alloy, etc.). B) Of course, not only when the flanges of the converter and the hood are fastened, but also the flange joints of vessels and pipelines,
It can be widely applied to a flange joint or a plate joint portion of a structure (in such a case, the gas cutting sleeve 4 or the fastening device 10 is often unnecessary. It is preferable that the washer be sandwiched between the flanges because the flange is not damaged. C) The temperature rise after fastening is not limited to the range shown in the embodiment, and there is no problem if the temperature rises to a temperature at which the yield point of the material of the sleeve does not extremely decrease. D) The same can be applied to a fastening portion where there is no gasket between the flanges. E) The present invention is not limited to the case where two or more flanges are fastened, but can also be applied to the case where one flange is fastened on a base with bolts. The conditions shown in the examples, under which the initial fastening force does not decrease due to the temperature rise and in which the fastening bolts can be used safely, are arranged and expressed as the conditions applicable to the general flange fastening portion. First, the equation can be replaced by Δt + Δt ′ ≧ Δl..., Because Δλ satisfying Δl ≦ Δλ needs to be generated as described above. As described above, since ΔF does not exceed A ₀ · E ₀ (Δt + Δt'-Δl) / l ₀ , the formula is A ₀ · E ₀ (Δt + Δt'-Δl) / l ₀ ≤A ₀ · σ _a It is sufficient to satisfy −F ₀ −F ₁ ... ′. ',' Combining 0 ≦ Δt + Δt'-Δl ≦ (A 0 · σ a -F 0 -F 1) l 0 / A 0 E 0 ∴Δl-Δt ≦ Δt '≦ (A 0 · σ a -F 0 −F ₁ ) l ₀ / A ₀ E ₀ + Δl−Δt, but this equation is applied when n total sleeves are clamped together with m total flanges, gaskets, washers, etc. When, Becomes In other words, this equation is the condition of the thickness t ′ _i and the linear expansion coefficient α ′ _i of the sleeve to be inserted when the temperature of the fastening portion including the flange and the bolt increases by ΔT after the fastening. (Effects of the Invention) According to the high-temperature flange fastening structure of the present invention configured as described above, the following effects are provided. That is, even if the temperature of the fastening portion including the flange and the bolt rises after fastening, the fastening force does not decrease, so that the fluid in the container or the pipeline leaks or the bolt receives an uneven load and breaks. There is no. In addition, only a simple part called a sleeve is required, and no special cost or labor is required. Further, even when the nut cannot be turned due to foreign matter biting or the like, the fastening between the flanges can be easily released. There is also an effect that the fastening force is high and the heat resistance is excellent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a converter and a hood according to an embodiment of the present invention, FIG. 2 (a) is a detailed view of a flange fastening portion in FIG. 1, and FIG. 2 (b) FIG. 2 is a bottom plan view of FIG. 2 (a). 1 ... bolt, 2 ... nut, 3, 4 ... sleeve, 10 ...
… Fastening device, A… Converter, A1… Furnace opening flange, A4…
Gasket, B: Hood, B21: Lower flange.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-200311 (JP, A) JP-A-60-170050 (JP, U) JP-A-57-164316 (JP, U) JP-A-60-160 112717 (JP, U) Actually open sho 59-133,752 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16B 39/01

Claims (1)

(57) [Claims] A fastening structure of a flange having a temperature rise after fastening, between a head of a fastening bolt and a nut, together with a flange or a gasket to be fastened, and a stainless steel or nickel steel having a larger linear expansion coefficient than the bolt. And a sleeve made of low-carbon steel from which gas can be easily cut, the head of the fastening bolt is shaped to be long in the direction perpendicular to the axial direction of the bolt, and the head is A high-temperature flange fastening structure, wherein a bolt hole to be inserted only when the head is in a fixed direction is provided in the flange on the side to be engaged. 2. The temperature increase width is ΔT, and the linear expansion coefficient is _{m along} with a total of m flanges and gaskets having a coefficient of linear expansion α ₁ , α ₂ ,..., Α _m and thicknesses t ₁ , t ₂ ,. Coefficients α ' ₁ , α' ₂ , ..., α ' _n , thicknesses t' ₁ , t ' ₂ , ..., t'
_n total sleeves including the two types n,
These are referred to as longitudinal elastic modulus E ₀ , linear expansion coefficient α ₀ , effective area
Using the bolt A _0, if it enters between the inter-surface distance between the bolt head and the nut _{l 0 (= t 1 + ...} + t m + t '1 + ... + t' n), the linear expansion of each sleeve Coefficient and thickness, (Where, σ _a : allowable tensile stress of bolt, F ₀ : initial fastening force per bolt, F ₁ : tension per bolt generated by external force acting on the flange). The high-temperature flange fastening structure according to claim 1.