JP2004060736A

JP2004060736A - Expansion joint used in hot environment

Info

Publication number: JP2004060736A
Application number: JP2002218455A
Authority: JP
Inventors: Koichi Kimura; 木村　紘一; Shigeru Okawa; 大川　茂; Shigeroku Yokiashi; 過足　重六; Yoshihiro Shimizu; 清水　嘉宏; Hiroshi Murata; 村田　浩
Original assignee: A&A Material Corp
Current assignee: A&A Material Corp
Priority date: 2002-07-26
Filing date: 2002-07-26
Publication date: 2004-02-26
Anticipated expiration: 2022-07-26
Also published as: JP3853266B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expansion joint capable of preventing bellows from being damaged over a long term even if internal pressure repeatedly changes made. <P>SOLUTION: A bellows 41 of an expansion joint 31, of the whole comprises a fluorocarbon resin layer placed at the inside in the radial direction and a glass fabric layer placed at the outside in the radial direction, includes a pair of sections-to-be fixed 51 and a bellows body section 53 formed so as to expose between them. Furthermore, the bellows body section includes a pair of base sections 55 and a tube-shape swelling section 57 which is placed between them, swells out of a virtual surface with a curvature that includes the pair of base sections and swells in an arc shape. Threads of the glass fabric layer have density that warps and wefts are respectively in the range of 6 to 10 and set in an area of 25 millimeters square, and such a fiber direction that each of warps and wefts slant relative to the axial center of the bellows. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、一対の管状物を接続する伸縮継手に関し、特に管状物の内圧に起因した伸縮継手の変形に対処する技術に関するものである。
【０００２】
【従来の技術】
図４〜図６に従来の伸縮継手の構造を示す。伸縮継手１は、上流側ダクト３及び下流側ダクト５の間に配設され、一対のフランジ付き本体７、９と、これら一対の本体７、９を連結するベローズ１１とを備える。一対の本体７、９はそれぞれ、対応するダクト３、５に接続するような管状部材からなる。また、一対の本体７、９は相互に離隔しており、ベローズ１１はこれら本体が離隔した空間を覆っている。ベローズ１１は、本体７、９の押え部７ａ、９ａと、対応するベローズ押え板１３、１５とに挟まれて固定されており、通常はゴム材から構成されている。
【０００３】
流れ方向に沿って見た場合の図５に示されるように、ベローズ１１は（従って、押え部７ａ、９ａやベローズ押え板１３、１５も）、流れ方向に直交する断面形状がほぼ矩形の筒状部材からなる。すなわち、ベローズ１１は、上下方向に延長し且つ流れ方向から見た投影形状が直線である一対のストレート部１７ａ、１７ｂと、横方向に延長し且つ流れ方向から見た投影形状が直線である一対のストレート部１９ａ、１９ｂと、それぞれ隣接するストレート部を接続し且つ流れ方向から見た投影形状が曲線である４つのコーナー部２１ａ、２１ｂ、２１ｃ、２１ｄ（一コーナー部を示す図６も参照）とを備えている。
【０００４】
以上のように、一対の本体７、９を離隔させ、それらの間をベローズ１１で接続しているため、ダクト内の流体の温度変化や圧力変化に起因して一対の本体７、９の位置関係に変化が強いられるような状態でも、ベローズ１１が変形して本体７、９の位置関係の変化を好適に吸収することができる。
【０００５】
【発明が解決しようとする課題】
しかしながら、上述した構造のベローズ１１を有する従来の伸縮継手においては、ダクト３、５内の流体の内圧が継手外部の外気圧よりも高くなると、ベローズ１１が変形し、場所によって膨らんだり窪んだりする現象が生じる。図７は、ベローズ１１における図６と同じ部分であり、内圧による変形後の状態を示す。図７に一コーナー部周辺が示されるように（他のコーナー部でも同様な変形が発生）、ダクト３、５内の内圧が高い場合には、ベローズ１１の４つのストレート部１７ａ、１７ｂ、１９ａ、１９ｂでは、径方向外側に膨出する部分２３が発生する。一方、４つのコーナー部２１ａ、２１ｂ、２１ｃ、２１ｄでは、ストレート部と同様、径方向外側に膨出する部分２５が発生しながら、ベローズの変形前と変形後の周長が不変であることに起因して、当該部分２５における流れ方向のほぼ中央位置には、他の部分が膨出した分だけ逆に内側に向けて窪んだ凹み部分２７が発生する。
【０００６】
そして、このような膨出部分２３、２５や凹み部分２７は、ベローズ１１の内圧が低下すると元の平坦なストレート部１７ａ、１７ｂ、１９ａ、１９ｂや平坦なコーナー部２１ａ、２１ｂ、２１ｃ、２１ｄに戻る。したがって、ベローズ１１の内圧の上昇及び降下が繰り返し生じると、ベローズの流れ方向の伸縮、半径方向の膨らみや窪み、振動なども繰り返し生じ、短期間でベローズが破損する恐れがある。特に、内側に向けて窪む凹み部分２７は、鋭角的に折れるため、上記の繰り返しの変形に際してより破損が起こりやすくなっており、また、ベローズ内側の保温材などに食い込むといった問題も起こり得る。
【０００７】
また、従来のベローズ１１は、前述したようにゴム材から構成されているため、プラントなどにおいて内部に非常に高温な流体を流通させるような態様では使用しにくく、特に高温条件下に加えて上記のような圧力変動に伴う伸縮・振動が繰り返し生じる場合には、尚更、その耐久性が問題となる恐れがあった。
【０００８】
従って、本発明は、このような従来の問題に鑑みてなされたものであり、内圧の変化が繰り返し生じても長期間に亙ってベローズが破損しない高温環境下用の伸縮継手を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上述の目的を達成するため、本発明は、一対の被接続部材に対応して設けられる一対の継手本体と、これら一対の継手本体を接続するベローズとを備えた、２００℃以上の高温環境下用の伸縮継手であって、前記ベローズは、該ベローズの上流端部及び下流端部を構成する一対の被固定部と、これら一対の被固定部の間に位置すると共に前記一対の継手本体から露出するベローズ本体部とを備え、前記ベローズ本体部は、該ベローズ本体部の上流端部及び下流端部を構成する一対のベース部と、これら一対のベース部の間に位置すると共にこれら一対のベース部を包含する曲率の仮想面よりも外側且つ弧状に膨出した筒状膨出部とを備え、前記ベローズは、径方向内側に配置されるフッ素樹脂層と径方向外側に配置されるガラスクロス層とから形成され、前記ガラスクロス層の糸密度は、２５ｍｍ四方の領域に縦糸、横糸それぞれが６〜１０本の範囲に設定され、且つ、該ガラスクロス層の繊維方向は、縦糸、横糸それぞれが前記ベローズ軸心方向に対して傾斜している、ことを特徴とする。
【００１０】
また、前記ベローズは、前記一対の被固定部及び前記ベローズ本体部の間と、前記一対のベース部及び前記筒状膨出部の間との、二段階で曲がっていてもよい。
好適には、前記一対のベース部及び前記筒状膨出部は均一な厚さに形成されている。
好適には、前記筒状膨出部はその全周方向に関して角のない弧状に膨出している。
【００１１】
【発明の実施の形態】
以下、この発明の実施の形態を添付図面に基づいて説明する。
【００１２】
図１にこの発明の実施の形態に係る高温環境下用の伸縮継手を示す。伸縮継手３１は、被接続部材としての上流側ダクト３及び下流側ダクト５の間に配設され、一対のフランジ付き継手本体３７、３９と、これら一対の本体３７、３９を連結する筒状のベローズ４１とを備える。一対の本体３７、３９はそれぞれ、対応するダクト３、５に接続するような管状部材からなる。第１の本体３７の上流側には、ダクトフランジ部３７ａが形成されている。一方、上流側ダクト３の下流側にも同様なフランジ部３ａが形成されており、フランジ部３７ａとフランジ部３ａとを図示しない締結手段により接続することにより、第１の本体３７は上流側ダクト３に気密に接続されている。なお、第１の本体３７の管路内側には、バッフル３３が設けられている。また、第２の本体３９の下流側及び下流側ダクト５の上流側にも同様なダクトフランジ部３９ａ及びフランジ部５ａが形成されており、これらフランジ部３９ａ及びフランジ部５ａを図示しない締結手段により接続することにより、第２の本体３９は下流側ダクト５に気密に接続されている。
【００１３】
第１及び第２の本体３７、３９にはそれぞれ、環状の押え部３７ｂ、３９ｂが形成されている。これらの押え部３７ｂ、３９ｂにはそれぞれ、ベローズ４１の上流端及び下流端が係合している。さらに、押え部３７ｂ、３９ｂに係合したベローズ４１の上流端及び下流端の外側には、本体３７、３９の一構成部材である押え板３７ｃ、３９ｃが配設されている。すなわち、ベローズ４１は、その上流端及び下流端が押え部３７ｂ、３９ｂ及び押え板３７ｃ、３９ｃの間に挟まれ、これら押え部及び押え板が締結手段３５によって連結されることによって、一対の本体３７、３９の間に固定される。また、一対の押え板３７ｃ、３９ｃは、図中概念的に示されたシッピングボルト４３によって連結されている。さらに、ベローズ４１の内側には、適当な断熱手段４５が配設されている。
【００１４】
次に、図１及び図２をもとにベローズ４１について説明する。なお、図２は、図７と同様な図である。ベローズ４１は、大別して、一対の被固定部５１と、それら被固定部５１の間に位置するベローズ本体部５３とから構成されている。また、ベローズ４１は全体がほぼ一定の厚さを有する膜状部材であり、したがって、一対の被固定部５１及びベローズ本体部５３が同じ厚さで構成されている。なお、図２においては、ベローズ本体部５３の厚さが省略されて図示されているが、これはベローズ本体部５３の湾曲形状を明瞭に示すことを優先したためであり、実際にはベローズ４１全体がほぼ均一な厚さを有する。
【００１５】
一対の被固定部５１は、ベローズ４１の流れ方向の最上流端部と最下流端部とに位置しており、押え板３７ｃ、３９ｃと継手本体３７、３９の押え部３７ｂ、３９ｂとの間に挟まれる。また、一対の被固定部５１は、一平面（図２に符号Ｇで示される仮想平面）上に沿って延長した平坦面からなり、本実施の形態では押え板３７ｃ、３９ｃ及び押え部３７ｂ、３９ｂによって覆われている。
【００１６】
一方、ベローズ本体部５３は、その全体が押え板３７ｃ、３９ｃ及び押え部３７ｂ、３９ｂに覆われずに露出している部分であって、一対のベース部５５と、それらベース部の間に位置し弧状に膨らんだ変形抑制用の筒状膨出部５７とから構成されている。一対のベース部５５は、ベローズ本体部５３の流れ方向の最上流端部と最下流端部とに位置した平坦部である。また、本実施の形態では、一対のベース部５５は、一対の被固定部５１を包含する仮想平面Ｇに沿って配置されるのではなく、仮想平面Ｇよりも若干径方向外側に膨らんでいる。これは、ダクト内の流体の温度変化や圧力変化に起因して一対の継手本体３７、３９の位置関係に変化が強いられるような状態を考慮し、ベローズ本体部５３を継手本体３７、３９の間でピンと張らずに余裕を持たせるためである。したがって、従来のベローズの中には、一対の被固定部の間に位置するベローズ本体部分の全体が一定の曲率で膨らんだ態様のものもあるが、本発明では余裕確保のための一対のベース部５５はベローズ本体部５３における両端部のみに形成されていると共に、その間には、変形抑制用の筒状膨出部５７が設けられている。
【００１７】
筒状膨出部５７は、一対のベース部５５の間に位置しそれらベース部５５よりも更に外側に膨出している。より詳細には、筒状膨出部５７の膨出態様は、一対のベース部５５の本来の曲率を持った仮想面Ｈ（図１参照）、すなわち両ベース部５５を包含するように両ベース部５５を結ぶような仮想面Ｈに対して、さらに外側に弧状に膨出している。したがって、被固定部５１に対してベース部５５が角度をもっている場合には、ベローズ４１全体としては、被固定部５１とベース部５５との間、ベース部５５と筒状膨出部５７との間という二段階で曲がっているような形態を備える。また、筒状膨出部５７は、その周方向のいずれの位置にも角がないよう、すべてのストレート部からコーナー部に渡って弧状の湾曲を有する。したがって、角の部分から損傷が広がることを防止することができる。さらに、筒状膨出部５７における最膨出部は、ベローズの流れ方向中央部に位置しており、上述した一対のベース部５５及び一対の被固定部５１は当該最膨出部を基準に流れ方向上流側及び下流側に対称的に形成されている。
【００１８】
また、上述した一対の被固定部５１、一対のベース部５５及び筒状膨出部５７は全て、流れ方向からみた投影形状が矩形に形成されている。すなわち、一対の被固定部５１、一対のベース部５５及び筒状膨出部５７の各々は、流れ方向から見た投影形状が直線状に形成されている４つのストレート部５１ａ、５５ａ、５７ａと、隣接するストレート部を接続すると共に、流れ方向から見た投影形状が曲線状に形成されている４つのコーナー部５１ｂ、５５ｂ、５７ｂとからなる。
【００１９】
ベローズ４１は、高温環境下で内圧の変化が繰り返し生じても、長期間に亙って破損しないよう、ガラスクロス層とフッ素樹脂層（テフロン（登録商標）層）とから構成されている。具体的には、フッ素樹脂層（テフロン（登録商標）層）がベローズ４１の径方向内側を構成し、フッ素樹脂層と熱融着させて一体化したガラスクロス層がベローズ４１の径方向外側を構成する。なお、上記の高温環境の範囲は、その下限状態はベローズ内を流通する流体温度が約２００℃の状態とし、上限状態はベローズ自体の温度が約２６０℃となる状態とする。ベローズ自体の温度が約２６０℃となるこの上限状態は、ベローズの内側に設ける断熱手段の種類や厚さなどの構成によって左右され、ベローズ内を流通する流体温度で約１０００℃となる状態もある。また、ベローズ４１は、図２に一点鎖線領域Ｊで概念的に示されるように、ガラスクロス層を構成する縦糸５９、横糸６１がともに、流れ方向（ベローズ軸心方向）Ｋに対して傾いた方向となるように、配置される。なお、図２における一点鎖線領域Ｊ以外に付された格子状の線は、ベローズの曲面を理解しやすく表すためのものであり、繊維方向を示すものではない。さらに、ガラスクロス層を構成するガラスクロスの糸密度は、縦糸、横糸ともに直径２〜０．６ｍｍの太さのものを使用して、２５ｍｍ四方の領域に縦糸、横糸それぞれが６〜１０本の範囲に選択される（ＪＩＳ　Ｒ　３４２０）。これにより、高温環境下、特にベローズ軸心方向と直交するような方向の移動量が引き起こす、ベローズ４１の複雑な変形にも追従でき、長期に亙って破損を防止することができる。
【００２０】
次に、以上説明した本実施の形態に係る伸縮継手の作用について説明する。伸縮継手３１によって接続された一対のダクト３、５内には、上流側ダクト３から下流側ダクト５に向かって所定の流体が流れる。ここで、ダクト３、５や継手の内側の流体の圧力が外側の圧力よりも高い場合には、前述したようにベローズの流れ方向ほぼ中央部付近のコーナー部で、鋭角的な窪みが生じる恐れがある。しかしながら、本実施の形態の伸縮継手３１では、ベローズ４１の流れ方向ほぼ中央部付近に、もともと外側且つ弧状に突出した形状であってガラスクロス層及びフッ素樹脂層の二層構造で且つそのガラスクロス層の糸密度及び繊維方向が前述した態様である、筒状膨出部５７が設けられているため、ベローズ内側の圧力が上昇しても、ベローズ４１のコーナー部には、鋭角的に内側に窪む部分が発生しない。よって、ベローズ４１内側の圧力の上昇降下が繰り返し起きても、短期間でベローズ４１が破損することを確実に防止できる。
【００２１】
次に、耐屈曲試験を行い、糸密度の条件を除いて上記と同様な構成を有する本発明の伸縮継手のベローズ（以下、本願ベローズと称する）と、従来からある筒状膨出部を持たない既存の形態にガラスクロス層を付加したベローズ（以下、従来ベローズと称する）とを比較した結果を以下に示す。従来ベローズ及び本願ベローズとしては、無負荷状態の幅（流れ方向寸法）が２８５ｍｍ、被固定部を基準とした直径が４００ｍｍのものを使用する。まず、従来ベローズ及び本願ベローズをそれぞれ、２６０℃で３時間加熱し、上記２００℃以上の高温使用環境下の状態を与える。その後、ベローズの一端を他端に向けて往復させるような伸縮試験機にセットし、伸縮幅１００ｍｍ、伸縮速度１００回／分の条件で、ベローズを伸縮させ、１００００回伸縮終了毎に、破損状況などを含めた観察を行い、最終的には５００００回の伸縮を行って、その後で、ＪＩＳ　Ｒ　３４２０に準拠した引張り強度試験を行った。まず、従来ベローズについては、２６０℃で３時間加熱後に図３に示されるようにベローズに生じる折れジワを対称的に整えたような折れジワ６３（すなわち、図７で示した窪みに等しい）を付与し、伸縮を開始する。一方、本願ベローズについては、上述した一対の被固定部、一対のベース部及び筒状膨出部から構成された形態により、２６０℃で３時間加熱後にも折れジワは出現しなかったため、図１及び図２に示した形態のまま、伸縮を開始する。なお、本願ベローズの例としては、
（１）本願ベローズＡ：ガラスクロス層の厚さ０．６ｍｍ、糸密度が縦糸７本、横糸８本、
（２）本願ベローズＢ：ガラスクロス層の厚さ０．６ｍｍ、糸密度が縦糸１１本、横糸１１本、及び
（３）本願ベローズＣ：ガラスクロス層の厚さ０．６ｍｍ、糸密度が縦糸５本、横糸５本、
の３タイプを用意した。
一方、従来ベローズの例としては、ガラスクロス層の厚さ２．０ｍｍ、糸密度が縦糸１５本、横糸１１本、のものを使用した。
【００２２】
まず、１００００回伸縮毎のベローズ外観の観察を行ったところ、以下の表１のような結果が得られた。
【００２３】
【表１】

【００２４】
表１から分かるように、従来ベローズでは、１００００回の伸縮終了後に、ベローズ可動部側の折れジワ箇所のガラス繊維部に毛羽立ちが発生し、５００００回の伸縮終了時点には、さらに加えて他の部分にも毛羽立ちや糸切れが発生した。また、本願ベローズＢでは、１００００回の伸縮終了後の状態では異常がなかったが、５００００回の伸縮終了時点では、ベローズ中央部に毛羽立ちが発生した。また、本願ベローズＣでは、１００００回の伸縮終了後の状態では異常がなかったが、５００００回の伸縮終了時点では、フッ素樹脂層の方の中央部に亀裂が発生していた。これは、ガラスクロス層の糸密度が少なく十分な耐伸縮性が確保できなかったためである。これらに対し、本願ベローズＡでは、５００００回の伸縮終了時点でも異常がまったく生じなかった。
【００２５】
また、５００００回の伸縮終了後の引張り強度試験を行ったところ、以下の表２のような結果が得られた。なお、引張り強度試験を行う試験片は５個用意し、従来ベローズでは、図３に示されるようにベローズ軸心に対して傾斜した折りジワ部を含む領域６５から帯状（長さ１５０ｍｍ、幅２５ｍｍ）に５本切り出し、本願ベローズＡでは従来ベローズの領域６５に相当する位置の領域から同様に５本切り出して試験片とした。
【００２６】
【表２】

【００２７】
表２から分かるように、従来ベローズでは、引張り強度の平均値は２５ｍｍ四方の領域で０．６４ｋＮであるのに対し、本願ベローズＡでは、引張り強度の平均値は２５ｍｍ四方の領域で１．１８ｋＮであった。すなわち、本願ベローズＡでは、５００００回の伸縮終了後でも、従来ベローズの約２倍の引張り強度が確保されていることが分かる。また、伸縮を与える前のベローズに関する同態様の試験片による引張り強度平均値は、１．２７ｋＮであり、本願ベローズＡでは、５００００回の伸縮終了後も、ほとんど破損につながるような強度の低下が生じていないことが了解される。
【００２８】
このように、耐屈曲試験の結果からも分かるように、本願の伸縮継手に採用されるベローズは、高温環境下で内圧の変化が繰り返し生じても、長期間に亙って破損しないような耐久性が確保されている。
【００２９】
【発明の効果】
以上説明したように、本発明の伸縮継手によれば、高温環境下で内圧の変化が繰り返し生じても、長期間に亙ってベローズの破損を防止することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る伸縮継手の要部縦断面図である。
【図２】本発明の実施の形態に係る伸縮継手に関し、矩形ベローズの一コーナー部近傍の形状を示す斜視図である。
【図３】比較例としてのベローズの一コーナー部近傍の形状を示す斜視図である。
【図４】従来の伸縮継手の要部縦断面図である。
【図５】従来の伸縮継手に関し、ベローズ近傍を流れ方向からみた図である。
【図６】従来の矩形ベローズの一コーナー部近傍であって、内圧による変形前の形状を示す斜視図である。
【図７】従来の矩形ベローズの一コーナー部近傍であって、内圧による変形後の形状を示す斜視図である。
【符号の説明】
３１…伸縮継手、３７、３９…筒状継手本体、４１…ベローズ、５１…被固定部、５３…ベローズ本体部、５５…ベース部、５７…筒状膨出部。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an expansion joint for connecting a pair of tubular objects, and more particularly to a technique for coping with deformation of the expansion joint caused by internal pressure of the tubular object.
[0002]
[Prior art]
4 to 6 show the structure of a conventional expansion joint. The expansion joint 1 is disposed between the upstream duct 3 and the downstream duct 5 and includes a pair of main bodies 7 and 9 with a flange and a bellows 11 connecting the pair of main bodies 7 and 9. Each of the pair of main bodies 7 and 9 is formed of a tubular member connected to the

corresponding duct

3 or 5. The pair of main bodies 7 and 9 are separated from each other, and the bellows 11 covers a space where the main bodies are separated from each other. The bellows 11 is sandwiched and fixed between the holding portions 7a, 9a of the main bodies 7, 9 and the corresponding

bellows holding plates

13, 15, and is usually made of a rubber material.
[0003]
As shown in FIG. 5 when viewed along the flow direction, the bellows 11 (and thus the holding portions 7a and 9a and the bellows holding plates 13 and 15) are cylindrical tubes having a substantially rectangular cross section orthogonal to the flow direction. It consists of a shape member. In other words, the bellows 11 includes a pair of straight portions 17a and 17b extending vertically and having a straight projection shape when viewed from the flow direction, and a pair of straight portions extending horizontally and having a straight projection shape when viewed from the flow direction. And four

corner portions

21a, 21b, 21c, 21d connecting the straight portions 19a, 19b with the adjacent straight portions and having a curved projected shape as viewed from the flow direction (see also FIG. 6 showing one corner portion). And
[0004]
As described above, since the pair of main bodies 7 and 9 are separated from each other and are connected by the bellows 11, the positions of the pair of main bodies 7 and 9 are changed due to a change in temperature or pressure of the fluid in the duct. Even in a state in which the relationship is forced to change, the bellows 11 is deformed and the change in the positional relationship between the main bodies 7 and 9 can be appropriately absorbed.
[0005]
[Problems to be solved by the invention]
However, in the conventional expansion joint having the bellows 11 having the above-described structure, when the internal pressure of the fluid in the

ducts

3 and 5 becomes higher than the external air pressure outside the joint, the bellows 11 is deformed and swells or depresses depending on the location. A phenomenon occurs. FIG. 7 is the same portion of the bellows 11 as in FIG. 6, and shows a state after deformation due to internal pressure. As shown in FIG. 7 around one corner (similar deformation occurs at other corners), when the internal pressure in the

ducts

3 and 5 is high, the four straight portions 17a, 17b and 19a of the bellows 11 are provided. , 19b, a portion 23 bulging outward in the radial direction is generated. On the other hand, in the four

corner portions

21a, 21b, 21c, and 21d, the circumferential length before and after deformation of the bellows remains unchanged while the portion 25 bulging outward in the radial direction occurs similarly to the straight portion. Due to this, a concave portion 27 which is depressed inward on the opposite side by the amount that the other portion swells is generated at a substantially central position in the flow direction of the portion 25.
[0006]
When the internal pressure of the bellows 11 decreases, the bulging

portions

23 and 25 and the recessed portions 27 return to the original flat

straight portions

17a, 17b, 19a and 19b and the

flat corner portions

21a, 21b, 21c and 21d. Return. Therefore, if the internal pressure of the bellows 11 repeatedly increases and decreases, the bellows repeatedly expands and contracts in the flow direction, swells and dents in the radial direction, vibrates, etc., and the bellows may be damaged in a short period of time. In particular, the concave portion 27 that is depressed inward is sharply bent, so that it is more likely to be damaged during the above-described repeated deformation, and a problem may occur that the concave portion 27 bites into a heat insulating material inside the bellows.
[0007]
In addition, since the conventional bellows 11 is made of a rubber material as described above, it is difficult to use the bellows 11 in a mode in which a very high-temperature fluid is circulated inside a plant or the like. If the expansion and contraction / vibration caused by the pressure fluctuation as described above occur repeatedly, there is a possibility that the durability may be a problem.
[0008]
Accordingly, the present invention has been made in view of such a conventional problem, and an object of the present invention is to provide an expansion joint for a high-temperature environment in which a bellows is not damaged for a long period of time even if the internal pressure changes repeatedly. With the goal.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a pair of joint bodies provided corresponding to a pair of connected members, and a bellows connecting the pair of joint bodies, in a high-temperature environment of 200 ° C. or more. The bellows comprises a pair of fixed parts constituting an upstream end and a downstream end of the bellows, and the bellows is located between the pair of fixed parts and the pair of joint bodies. An exposed bellows main body, wherein the bellows main body is located between the pair of bases and a pair of bases constituting an upstream end and a downstream end of the bellows main body, and the pair of bases is located between the pair of bases. A cylindrical bulging portion that bulges out in an arc shape outside the imaginary surface of the curvature including the base portion, wherein the bellows is a fluororesin layer disposed radially inward and a glass disposed radially outward Cross layer The yarn density of the glass cloth layer is set in a range of 6 to 10 for each of the warp and the weft in a 25 mm square area, and the fiber direction of the glass cloth layer is such that the warp and the weft are each the bellows. It is characterized by being inclined with respect to the axial direction.
[0010]
Further, the bellows may be bent in two stages: between the pair of fixed portions and the bellows main portion, and between the pair of base portions and the tubular bulging portion.
Preferably, the pair of base portions and the cylindrical bulging portion are formed to have a uniform thickness.
Preferably, the cylindrical bulging portion bulges in an arc having no corner in the entire circumferential direction.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0012]
FIG. 1 shows an expansion joint for use in a high-temperature environment according to an embodiment of the present invention. The expansion joint 31 is disposed between the upstream duct 3 and the downstream duct 5 as connected members, and has a pair of flanged

joint bodies

37 and 39 and a cylindrical member connecting the pair of

bodies

37 and 39. And a bellows 41. Each of the pair of

main bodies

37 and 39 is formed of a tubular member connected to the

corresponding duct

3 or 5. On the upstream side of the first main body 37, a duct flange portion 37a is formed. On the other hand, a similar flange portion 3a is formed on the downstream side of the upstream side duct 3, and the first main body 37 is connected to the upstream side duct 3 by connecting the flange portion 37a and the flange portion 3a by a fastening means (not shown). 3 is hermetically connected. A baffle 33 is provided inside the first main body 37 in the duct. A similar duct flange portion 39a and a similar flange portion 5a are formed on the downstream side of the second main body 39 and on the upstream side of the downstream side duct 5, and these flange portions 39a and 5a are fastened by fastening means (not shown). By connecting, the second main body 39 is airtightly connected to the downstream duct 5.
[0013]
The first and second

main bodies

37 and 39 are formed with annular pressing portions 37b and 39b, respectively. The upstream end and the downstream end of the bellows 41 are engaged with these holding portions 37b and 39b, respectively. Further, pressing

plates

37c, 39c, which are components of the

main bodies

37, 39, are disposed outside the upstream end and the downstream end of the bellows 41 engaged with the pressing portions 37b, 39b. That is, the bellows 41 has its upstream end and downstream end sandwiched between the holding portions 37b, 39b and the holding

plates

37c, 39c, and these holding portions and the holding plate are connected by the fastening means 35, thereby forming a pair of main bodies. It is fixed between 37 and 39. The pair of holding

plates

37c and 39c are connected by a shipping bolt 43 conceptually shown in the drawing. Further, inside the bellows 41, a suitable heat insulating means 45 is provided.
[0014]
Next, the bellows 41 will be described with reference to FIGS. FIG. 2 is a view similar to FIG. The bellows 41 is roughly composed of a pair of fixed portions 51 and a bellows main body portion 53 located between the fixed portions 51. Further, the bellows 41 is a film-like member having a substantially constant thickness as a whole. Therefore, the pair of fixed portions 51 and the bellows main body 53 have the same thickness. In FIG. 2, the thickness of the bellows main body 53 is omitted from the illustration, but this is because priority has been given to clearly showing the curved shape of the bellows main body 53, and in fact, the entire bellows 41 is actually shown. Have a substantially uniform thickness.
[0015]
The pair of fixed parts 51 are located at the most upstream end and the most downstream end in the flow direction of the bellows 41, and are located between the holding

plates

37c, 39c and the holding parts 37b, 39b of the

joint bodies

37, 39. Sandwiched between. In addition, the pair of fixed portions 51 are formed of flat surfaces extending along one plane (a virtual plane indicated by reference numeral G in FIG. 2), and in the present embodiment, the

pressing plates

37c, 39c and the pressing portions 37b, 39b.
[0016]
On the other hand, the bellows main body 53 is a portion that is entirely exposed without being covered by the holding

plates

37c, 39c and the holding portions 37b, 39b, and is located between the pair of bases 55 and the bases. And a cylindrical bulging portion 57 for suppressing deformation which bulges in an arc shape. The pair of base portions 55 are flat portions located at the most upstream end and the most downstream end in the flow direction of the bellows main body 53. Further, in the present embodiment, the pair of base portions 55 are not arranged along the virtual plane G that includes the pair of fixed portions 51, but swell slightly radially outward from the virtual plane G. . This takes into account a state in which the positional relationship between the pair of

joint bodies

37 and 39 is forced to change due to a temperature change or a pressure change of the fluid in the duct, and the bellows body 53 is connected to the

joint bodies

37 and 39. This is to allow room without tension between the two. Therefore, some conventional bellows have a configuration in which the entire bellows main body portion located between the pair of fixed portions bulges at a constant curvature, but in the present invention, a pair of bases for securing a margin is provided. The portions 55 are formed only at both ends of the bellows main body 53, and a cylindrical bulging portion 57 for suppressing deformation is provided therebetween.
[0017]
The tubular bulging portion 57 is located between the pair of base portions 55 and bulges further outward than the base portions 55. More specifically, the swelling mode of the tubular swelling portion 57 is such that the pair of base portions 55 have both the virtual surfaces H (see FIG. 1) having the original curvature, that is, both base portions 55 It bulges further outward in an arc shape with respect to a virtual plane H connecting the parts 55. Therefore, when the base portion 55 has an angle with respect to the fixed portion 51, the bellows 41 as a whole is formed between the fixed portion 51 and the base portion 55, and between the base portion 55 and the cylindrical bulging portion 57. It has a form that bends in two steps, between. Further, the cylindrical bulge portion 57 has an arc-shaped curve from all the straight portions to the corner portions so that there is no corner at any position in the circumferential direction. Therefore, it is possible to prevent the damage from spreading from the corner portion. Further, the most bulged portion in the tubular bulged portion 57 is located at the center in the flow direction of the bellows, and the above-described pair of base portions 55 and the pair of fixed portions 51 are based on the most bulged portion. It is formed symmetrically on the upstream and downstream sides in the flow direction.
[0018]
In addition, the above-mentioned pair of fixed portions 51, the pair of base portions 55, and the tubular bulging portions 57 are all formed in a rectangular projection shape as viewed from the flow direction. In other words, each of the pair of fixed portions 51, the pair of base portions 55, and the cylindrical bulging portion 57 has four

straight portions

51a, 55a, 57a whose projection shapes viewed from the flow direction are linearly formed. And four corner portions 51b, 55b, and 57b that connect adjacent straight portions and have a curved projection shape as viewed from the flow direction.
[0019]
The bellows 41 is composed of a glass cloth layer and a fluororesin layer (Teflon (registered trademark) layer) so that even if the internal pressure repeatedly changes in a high-temperature environment, the bellows 41 is not damaged for a long period of time. Specifically, a fluororesin layer (Teflon (registered trademark) layer) constitutes a radially inner side of the bellows 41, and a glass cloth layer which is heat-sealed and integrated with the fluororesin layer covers a radially outer side of the bellows 41. Constitute. The range of the high-temperature environment is such that the lower limit state is a state where the temperature of the fluid flowing through the bellows is about 200 ° C., and the upper limit state is a state where the temperature of the bellows itself is about 260 ° C. This upper limit state in which the temperature of the bellows itself is about 260 ° C. depends on the type and thickness of the heat insulating means provided inside the bellows, and in some cases, the temperature of the fluid flowing through the bellows is about 1000 ° C. . In the bellows 41, both the warp yarn 59 and the weft yarn 61 constituting the glass cloth layer are inclined with respect to the flow direction (bellows axial center direction) K, as conceptually indicated by the one-dot chain line region J in FIG. It is arranged so that it may become a direction. Note that the grid-like lines attached to regions other than the dashed-dotted line region J in FIG. 2 are for easy understanding of the curved surface of the bellows, and do not indicate the fiber direction. Further, the yarn density of the glass cloth constituting the glass cloth layer is such that the warp yarn and the weft yarn have a diameter of 2 to 0.6 mm, and the warp yarn and the weft yarn are each 6 to 10 yarns in a 25 mm square area. The range is selected (JIS R 3420). This makes it possible to follow complicated deformation of the bellows 41 caused by a movement amount in a high-temperature environment, particularly in a direction orthogonal to the bellows axis direction, and prevent damage for a long period of time.
[0020]
Next, the operation of the expansion joint according to the present embodiment described above will be described. A predetermined fluid flows from the upstream duct 3 to the downstream duct 5 in the pair of

ducts

3 and 5 connected by the expansion joint 31. Here, when the pressure of the fluid inside the

ducts

3 and 5 and the joint is higher than the pressure outside, there is a possibility that a sharp depression may occur at the corner near the center in the flow direction of the bellows as described above. There is. However, the expansion joint 31 according to the present embodiment has a two-layer structure of a glass cloth layer and a fluororesin layer, and has a two-layer structure composed of a glass cloth layer and a fluororesin layer near the center of the bellows 41 in the flow direction. Since the tubular bulging portion 57 in which the yarn density and the fiber direction of the layer are in the above-described manner is provided, even if the pressure inside the bellows increases, the corner portion of the bellows 41 is sharply inwardly formed at the corner portion. No depression occurs. Therefore, even if the pressure inside the bellows 41 rises and falls repeatedly, it is possible to reliably prevent the bellows 41 from being damaged in a short period of time.
[0021]
Next, a bending resistance test was performed, and the bellows of the expansion joint of the present invention (hereinafter, referred to as the bellows of the present application) having the same configuration as above except for the yarn density condition, and a conventional cylindrical bulging portion were provided. The result of comparison with a bellows having a glass cloth layer added to an existing form (hereinafter referred to as a conventional bellows) is shown below. As the conventional bellows and the bellows of the present application, those having a width (dimension in the flow direction) of 285 mm in a no-load state and a diameter of 400 mm based on the fixed portion are used. First, the conventional bellows and the bellows of the present application are each heated at 260 ° C. for 3 hours to give a state in a high-temperature use environment of 200 ° C. or more. Then, the bellows is set on an expansion / contraction tester that reciprocates one end toward the other end, and the bellows is expanded / contracted under the conditions of an expansion / contraction width of 100 mm and an expansion / contraction speed of 100 times / min. Observation including the above was performed, and ultimately, expansion and contraction was performed 50,000 times. Thereafter, a tensile strength test in accordance with JIS R 3420 was performed. First, as for the conventional bellows, a folding wrinkle 63 (that is, the same as the depression shown in FIG. 7) is obtained by heating the bellows at 260 ° C. for 3 hours, as shown in FIG. Apply and start stretching. On the other hand, with respect to the bellows of the present application, no fold wrinkles appeared even after heating at 260 ° C. for 3 hours due to the above-described configuration including the pair of fixed portions, the pair of base portions, and the cylindrical bulging portion. And expansion and contraction is started with the form shown in FIG. In addition, as an example of the bellows of the present application,
(1) Bellows A of the present application: glass cloth layer thickness 0.6 mm, yarn density 7 warp yarns, 8 weft yarns,
(2) Bellows B of the present application: glass cloth layer thickness of 0.6 mm, yarn density of 11 warp yarns and 11 weft yarns, and (3) Bellows of the present application C: glass cloth layer thickness of 0.6 mm, yarn density of warp yarn 5 threads, 5 weft threads,
3 types were prepared.
On the other hand, as an example of the conventional bellows, a glass cloth layer having a thickness of 2.0 mm, a yarn density of 15 warp yarns and 11 weft yarns was used.
[0022]
First, the appearance of the bellows was observed every 10,000 times of expansion and contraction, and the results shown in Table 1 below were obtained.
[0023]
[Table 1]

[0024]
As can be seen from Table 1, in the conventional bellows, after the end of the expansion and contraction of 10,000 times, the glass fiber portion of the bent wrinkle portion on the bellows movable part side became fuzzy, and at the end of the expansion and contraction of 50,000 times, the other additional Flushing and thread breakage also occurred in the part. Further, in the bellows B of the present application, there was no abnormality in the state after the end of the expansion and contraction of 10,000 times, but at the time of the end of the expansion and contraction of 50,000 times, fluffing occurred in the center of the bellows. Further, in the bellows C of the present application, there was no abnormality after the expansion and contraction of 10000 times, but at the end of the expansion and contraction of 50,000 times, a crack was generated in the central portion of the fluororesin layer. This is because the yarn density of the glass cloth layer was low and sufficient elasticity could not be secured. On the other hand, in the bellows A of the present application, no abnormality occurred even at the end of the 50,000 expansions / contractions.
[0025]
In addition, when a tensile strength test was performed after 50,000 times of expansion and contraction, the results shown in Table 2 below were obtained. In addition, five test pieces for performing a tensile strength test were prepared, and in the conventional bellows, as shown in FIG. 3, a band-like shape (length 150 mm, width 25 mm) was formed from a region 65 including a folding wrinkle portion inclined with respect to the bellows axis. ) Were cut out, and in the case of the bellows A of the present invention, five test pieces were similarly cut out from a region at a position corresponding to the region 65 of the conventional bellows.
[0026]
[Table 2]

[0027]
As can be seen from Table 2, in the conventional bellows, the average value of the tensile strength is 0.64 kN in a 25 mm square area, whereas in the present bellows A, the average tensile strength is 1.18 kN in a 25 mm square area. Met. That is, it can be seen that the bellows A of the present application secures about twice the tensile strength of the conventional bellows even after the end of the 50,000 expansions / contractions. The average tensile strength of the bellows before the expansion and contraction by the test piece of the same aspect is 1.27 kN. It is understood that it has not occurred.
[0028]
Thus, as can be seen from the results of the bending resistance test, the bellows used in the expansion joint of the present application is durable so as not to be damaged for a long period of time even if the internal pressure changes repeatedly under a high temperature environment. Is secured.
[0029]
【The invention's effect】
As described above, according to the expansion joint of the present invention, it is possible to prevent the bellows from being damaged for a long period of time even when the internal pressure repeatedly changes in a high-temperature environment.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a main part of an expansion joint according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a shape near one corner of a rectangular bellows in the expansion joint according to the embodiment of the present invention.
FIG. 3 is a perspective view showing a shape near one corner of a bellows as a comparative example.
FIG. 4 is a longitudinal sectional view of a main part of a conventional expansion joint.
FIG. 5 is a view of the vicinity of a bellows as viewed from a flow direction in a conventional expansion joint.
FIG. 6 is a perspective view showing a shape near a corner of a conventional rectangular bellows and before deformation by internal pressure.
FIG. 7 is a perspective view showing a shape after being deformed by internal pressure in the vicinity of one corner of a conventional rectangular bellows.
[Explanation of symbols]
31: expansion joint, 37, 39 ... cylindrical joint main body, 41 ... bellows, 51 ... fixed part, 53 ... bellows main body part, 55 ... base part, 57 ... cylindrical bulging part.

Claims

A pair of joint bodies provided corresponding to the pair of connected members, and a bellows connecting the pair of joint bodies, an expansion joint for a high temperature environment of 200 ° C. or higher,
The bellows includes a pair of fixed portions forming an upstream end portion and a downstream end portion of the bellows, and a bellows body portion located between the pair of fixed portions and exposed from the pair of joint bodies. ,
The bellows body has a pair of bases constituting an upstream end and a downstream end of the bellows body, and an imaginary surface having a curvature located between the pair of bases and including the pair of bases. A cylindrical bulging portion that bulges outwardly and in an arc shape,
The bellows are formed from a fluororesin layer disposed radially inward and a glass cloth layer disposed radially outward,
The yarn density of the glass cloth layer is set in the range of 6 to 10 warp yarns and weft yarns in an area of 25 mm square, and the fiber direction of the glass cloth layer is such that the warp yarns and the weft yarns are the bellows axial center directions. Inclined to
An expansion joint for use in a high temperature environment.

The bellows is bent in two stages, between the pair of fixed portions and the bellows main body, and between the pair of base portions and the tubular bulging portion. An expansion joint for use in a high-temperature environment according to 1.

3. The expansion joint according to claim 1, wherein the pair of base portions and the cylindrical bulging portion are formed to have a uniform thickness. 4.

The expansion joint for a high-temperature environment according to any one of claims 1 to 3, wherein the cylindrical bulging portion bulges in an arc shape having no corner in the entire circumferential direction.