JP3225969U - Cast iron flexible joint for stainless steel pipe connection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a situation where a flexible joint is corroded by corrosion of dissimilar metals even if it is required to connect a stainless pipe to the flexible joint made of cast iron. Provide fittings. A flexible joint (100) includes a loose flange (20), a joint body (10) having a socket portion (11) and a receiving opening (12), a flange receiving portion (13) provided in the receiving opening (12), and bolt insertion holes (22) of the loose flange (20). The first packing seats 15 and 23 of the joint body 10 and the loose flange 20 and the second packing seat 16 of the end surface of the socket portion 11 of the joint body 10. A nylon coating film having a thickness of 300 μm or more is formed on the surfaces of the loose flange 20 and the joint body 10. [Selection diagram] Figure 1

Description

  The present invention relates to a cast iron flexible joint for piping, and more particularly, to a cast iron flexible joint for connecting stainless steel pipes in which corrosion of dissimilar metal is unlikely to occur even when a stainless steel pipe is connected.

  It has been found that simply connecting a stainless steel pipe to a cast iron flexible joint for piping can cause problems with the phenomenon of dissimilar metal contact corrosion. For this reason, such piping is not normally performed. The dissimilar metal contact corrosion phenomenon is that when two kinds of metals having different electric potentials come into contact with each other or two kinds of metals having different electric potentials come into contact with an electrolytic solution such as water, when the electric potential difference is large, the electric potential becomes base. This is a phenomenon in which metal serves as an anode (anode) to promote corrosion, and a metal with a noble potential serves as a cathode (cathode) to suppress corrosion. Corrosion promoted on the anode side is "different." This is known as "metal contact corrosion".

  However, when renewing an existing pipe that has deteriorated over time, the remaining cut portion of the existing pipe is reused with the intention of shortening the construction period and keeping the construction cost low. It may be required to connect the combined stainless tubing to a cast iron flexible joint. Also, due to other circumstances, it may be required to connect a stainless pipe to the cast iron flexible joint.

  An effective measure capable of coping with these requirements has been proposed in the prior art example (see Patent Document 1). According to Patent Document 1 as this prior art example, there is a possibility that the stainless sleeve forming the conduit and the flexible joint made of cast iron may come into direct contact with each other, and fastening for tightening the cushion flange of the flexible joint. Electrically-insulating packings are placed at the contact points between the flanges and bolts and nuts used in the mechanism, thereby avoiding contact between the stainless steel sleeve and the cast iron flexible joint. This prevents the flexible joint made of cast iron and the sleeve made of stainless steel from electrically connecting with each other by using the drainage flowing in the pipe as an electrolytic solution.

Japanese Patent No. 6248168

  However, as in the above-mentioned Patent Document 1, an electrically insulating packing is used to prevent contact between dissimilar metals and prevent dissimilar metals from being electrically conducted by using drainage flowing in a pipeline as an electrolytic solution. The measure to remove the packing may increase the required number of packings, increase the number of parts, and increase the work man-hours for installing the packings, which may reduce workability during construction.

  The present invention has been made in view of the above circumstances, and even when it is required to connect a stainless pipe to a cast iron flexible joint, the flexible joint can be formed by the above-mentioned dissimilar metal contact corrosion phenomenon. Not only can corrosion be effectively prevented, but cast iron for connecting stainless steel pipes that does not cause a situation such as an increase in the number of parts or a decrease in workability due to an increase in work man-hours The purpose is to provide a flexible joint.

  A cast iron flexible joint for connecting a stainless steel pipe according to the present invention has an annular loose flange, a cylindrical socket portion, and a receiving port connected to the socket portion, and the receiving port is formed so as to overlap with the loose flange. A joint main body provided with a flange receiving portion to be deployed, bolt insertion holes provided in each of the loose flange and the flange receiving portion, and a loose fitting in each of the receiving opening and the loose flange. A first packing seat for pressing the electrically insulating cushion packing in cooperation with the pipe wall surface of the insertion port of the stainless steel pipe inserted in a mating state, and the end face of the socket portion for forming the stainless steel pipe insertion port. A second packing seat that presses an electrically insulating seal packing between the tip surface and a second packing seat, and an electrically insulating cylindrical body is attached to the inner peripheral surface of the receiving port. It was arranged to face the inserted port of the stainless steel tube.

  And, in the present invention, the inner peripheral surface of the joint main body which comes into contact with the drainage flowing through the internal flow path of the joint main body, the inner peripheral surface of the loose flange facing the pipe wall surface of the stainless steel pipe, and the loose flange The outer end surface of the loose flange and the inner peripheral surface of the bolt insertion hole of the loose flange located on the opposite side of the flange receiving portion arranged in an overlapping manner, and the inner peripheral surface of the bolt insertion hole of the flange receiving portion. Further, a nylon coating film is formed to cover an outer end surface of the flange receiving portion located on the opposite side of the loose flange arranged in an overlapping manner on the flange receiving portion.

  According to this invention, when the stainless steel pipe is connected, the first packing seats provided on the receiving port and the loose flange cooperate with the pipe wall surface of the insertion port of the stainless steel pipe to clamp the electrically insulating cushion packing. Therefore, even if the stainless steel pipe is flexibly displaced, the original function of the flexible joint that absorbs the flexural displacement is exerted.

  In addition to this, according to the present invention, the nylon coating film formed on the inner peripheral surface of the joint body that comes into contact with the wastewater flowing through the internal flow path of the joint body allows the joint body to be made of cast iron by using the wastewater as an electrolytic solution. The electric pipe that short-circuits the stainless steel pipe is cut off (first electric line cut-off portion), and the nylon pipe formed on the inner peripheral surface of the loose flange facing the pipe wall surface of the stainless steel pipe makes the stainless steel pipe and the cast iron loose flange. And the nylon coating formed on the outer end surface of the loose flange and the inner peripheral surface of the bolt insertion hole forms a circuit that short-circuits the loose flange and the bolt and nut. The flange is cut off (third electric circuit cut-off portion), and the nylon coating film is formed on the inner peripheral surface of the bolt insertion hole of the flange receiving portion and the outer end surface of the flange receiving portion. Path is interrupted for short-circuiting the parts and bolt (fourth path blockage region).

  Also, when the stainless steel pipe is connected, due to the action of the electrically insulating cushion packing and the electrically insulating seal packing, the inner peripheral surface of the receiving port is further covered with the electrically insulating cylindrical body. Since it faces the insertion port of, the electric path that short-circuits the stainless steel pipe and the receiving opening is cut off (the fifth electric path cut-off portion).

  In the cast iron flexible joint for connecting a stainless steel pipe of the present invention which operates in this way, the conditions under which the drainage plays the role of an electrolyte and the dissimilar metal contact corrosion phenomenon occurs on the flexible joint side are It is a case where the electric circuit interruption effect is impaired in all of the fourth electric circuit interruption parts, and the electric circuit interruption effect is effective even in only one of the first to fourth electric circuit interruption parts. No metal contact corrosion phenomenon occurs. Then, it is extremely unlikely that a situation in which the electric line interruption action is impaired at all of the first to fourth electric line interruption portions during operation of the flexible joint for piping applied to the longitudinal drainage pipe for housing , Practically unlikely.

  On the other hand, the electrically insulating tubular body, the electrically insulating cushion packing, and the electrically insulating seal packing, which are provided at the fifth electric circuit cut-off portion, have a bending displacement such that the stainless steel pipe is inclined with respect to the flexible joint. However, even if it occurs, its circuit-breaking action is not impaired. For this reason, the phenomenon of dissimilar metal contact corrosion without drainage occurs only when the stainless pipe flexes and deforms and comes into contact with the cast iron skin surface of the loose flange. However, since the nylon coating is formed on the inner circumferential surface of the loose flange facing the wall surface of the stainless steel pipe at the above-mentioned second electric circuit interruption site, this nylon coating is used for the cast iron skin surface of the stainless steel pipe and the loose flange. Helps prevent contact with. In this regard, it is undeniable that the nylon coating may be damaged by the collision with the stainless steel pipe and the stainless steel pipe may come into contact with the cast iron skin surface of the loose flange.However, the stainless steel pipe may not adhere to the nylon coating on the inner surface of the loose flange. Since the collision itself is very unlikely to occur, it is almost impossible for the stainless steel pipe to come into contact with the cast iron skin surface of the loose flange.

  In the present invention, the sockets of the joint body are provided with the sockets at one end and the other end, respectively, and the loose flanges are provided with respect to the flange receivers provided at the sockets, respectively. It is possible to adopt a configuration in which the bolt insertion holes are provided in each of the flange receiving portion and the loose flange while being combined separately. According to this, even if two stainless steel pipes are connected via the flexible joint, the above-mentioned dissimilar metal contact corrosion phenomenon does not occur.

  According to the present invention, the nylon coating having a thickness of 300 μm or more is formed on the entire inner and outer surfaces of the loose flange and the joint body and the inner peripheral surface of each of the bolt insertion holes by the fluid immersion method. It may be. The principle of the fluidized-bed method is to immerse a heated loose flange, fitting body, or other object in a floating layer of nylon powder suspended by an air stream to adhere the nylon powder to the object and melt it. Then, the nylon coating is brought into close contact with the object. The thickness of the nylon coating film formed by the fluid immersion method can be adjusted by the temperature of the object, the immersion time, and the like. By doing so, since the thickness of the nylon coating film is limited to 300 μm or more, it is almost impossible for the nylon coating film to be damaged and the stainless pipe to come into contact with the cast iron skin surface of the loose flange.

  In the present invention, by reducing the thickness of the nylon coating film formed on the inner peripheral surface of each bolt insertion hole to 300 μm or less, the bolt inserted into each bolt insertion hole and the nylon coating film are reduced. It is possible to adopt a configuration in which a gap is secured. According to this, the gap between the bolt inserted into the bolt insertion hole and the nylon coating film is appropriately maintained, and it is possible to prevent the nylon coating film from being damaged by the bolt inserted into the bolt insertion hole.

  In the present invention, it is possible to employ a configuration in which the bolt and the nut are combined with a flat washer that is superposed on the outer end surface of the loose flange. According to this, when the bolt or the nut is tightened, it is possible to prevent the nylon coating film from rubbing against the head or the nut of the bolt and damaging it.

  In the present invention, the bolt is a headed bolt that is inserted into the bolt insertion hole of the loose flange through the bolt insertion hole of the flange receiving portion, and the bolt protruding from the bolt insertion hole of the loose flange is attached to the nut. May be screwed on. According to this, it becomes possible to tighten the nut with good workability.

  As described above, according to the present invention, even when it is required to connect a stainless steel pipe to a cast iron flexible joint, the situation in which the flexible joint is corroded due to the phenomenon of corrosion of dissimilar metals is effective. It is possible to provide a cast iron flexible joint for connecting stainless pipes, which is not only prevented, but also does not cause a situation such as an increase in the number of parts or an increase in work man-hours, resulting in a decrease in workability. .

It is a longitudinal section showing an example of use of a cast iron flexible joint for stainless steel pipe connection concerning an embodiment of the present invention. FIG. 3 is a longitudinal sectional view of a cast iron flexible joint for connecting stainless steel pipes, which is illustrated by exaggerating the thickness of a nylon coating film. It is a partial longitudinal cross-sectional view of the cast iron flexible joint for stainless steel pipe connection by the modification which exaggerated and demonstrated the thickness of the nylon coating film. It is explanatory drawing which expanded and showed the A section of FIG. It is explanatory drawing which expanded and showed the B section of FIG. It is explanatory drawing which expanded and showed the C section of FIG. It is explanatory drawing which expanded and showed the D section of FIG.

  FIG. 1 is a vertical cross-sectional view showing an example of use of a cast iron flexible joint (hereinafter referred to as “flexible joint”) 100 for connecting stainless pipes according to an embodiment of the present invention. The flexible joint 100 in the figure has a basic configuration described below.

  The flexible joint 100 shown in FIG. 1 has a joint body 10 in which one end and the other end of a cylindrical socket portion 11 are provided with receiving ports 12 and 12, respectively. The loose flanges 20 and 20 are separately combined with the flange receiving portions 13 and 13 provided on the. Recessed first packing seats 15 and 23 are provided on the inner peripheral portions of the receiving ports 12 and 12 and the loose flange 20, respectively. Of these, the first packing seat 15 on the side of the receiving port 13 is a conical taper surface inclined inwardly. In addition, the one end surface and the other end surface of the socket portion 11 form second packing seats 16 and 16 which are conical tapered surfaces inclined inwardly constricted.

  While the loose flange 20 is formed in an annular shape and has bolt insertion holes 22 at a plurality of peripheral portions, the above-mentioned flange receiving portion 13 corresponding to the loose flange 20 has the receiving port 12 of the joint body 10. Is formed in a plurality of protrusions around the periphery of each of the flange receiving portions 13 and a bolt insertion hole 14 is also provided in each of the flange receiving portions 13. Then, the nut 35 is screwed into the bolt 30 that is a headed bolt that is inserted in the bolt insertion hole 14 of the flange receiving portion 13 and the bolt insertion hole 22 of the loose flange 20 in a loosely fitted state.

  FIG. 1 shows a flexible joint 100 applied to a vertical drainage pipe (stand pipe) for a house. In the illustrated example, an upper hard vinyl chloride lining steel pipe (hereinafter referred to as “PVC lining steel pipe”) 200 and a lower stainless pipe 300 are connected via the flexible joint 100. The vinyl chloride lining steel pipe 200 of the illustrated example is configured by forming an inner lining layer 202 of a required thickness made of hard vinyl chloride resin on the inner peripheral surface of a thin steel pipe 201, and is a tubular hard material excellent in lightness and corrosion resistance. The vinyl chloride lining layer 202 has a property in which the mechanical strength of the thin steel pipe 201 is added.

  At the connection point between the flexible joint 100 and the PVC lining steel pipe 200, the pipe of the insertion port 203 of the PVC lining steel pipe 200 inserted in a loose fitting state into the receiving port 12 and the loose flange 20 arranged so as to overlap the receiving port 12. A cushion packing 40 is interposed in an enclosed space surrounded by the wall surface 204, the receiving opening 12, and the first packing seats 15 and 23 of the loose flange 20. Further, the seal packing 50 is interposed in the gap between the tip end surface 205 of the insertion port 203 of the PVC lining steel pipe 200 and the second packing seat 16 of the socket portion 11, and between the cushion packing 40 and the seal packing 50. The entire tubular wall surface 204 of the insertion port 203 of the exposed vinyl chloride lining steel pipe 200 is covered with the tubular body 60. The inner peripheral surface of the receiving port 12 faces the insertion port 303 of the stainless steel tube 300 in which the tubular body 60 is mounted.

  Further, the nut 35 is screwed into the bolt 30 that is a headed bolt that is inserted in the bolt insertion hole 14 of the flange receiving portion 13 and the bolt insertion hole 22 of the loose flange 20 in a loosely fitted state, and the loose flange 20 is It is tightened by the nut 35. As a result, the cushion packing 40 is axially compressed, and the cushion packing 40 cooperates with the first packing seats 15 and 23 of the receiving port 12 and the loose flange 20 and the pipe wall surface 204 of the insertion port 203 of the PVC lining steel pipe 200. Since the cushion packing 40 presses the insertion opening 203 of the PVC lining steel pipe 200 to position the PVC lining steel pipe 200, the cushion packing 40 positions the PVC lining steel pipe 200, and the tip surface 205 of the insertion port 203 of the PVC lining steel pipe 200 and the socket portion 11 are pressed. The seal packing 50 is brought into close contact with the second packing seat 16 and exhibits sealing performance.

  On the other hand, at the connection portion between the flexible joint 100 and the stainless pipe 300, the pipe wall surface 304 of the insertion port 303 of the stainless pipe 300 inserted in the loose flange 20 and the receiving port 12 in a loosely fitted state and the receiving port 12 and the loose flange 20 are inserted. A cushion packing 40 is interposed in an enclosed space surrounded by the first packing seats 15 and 23. Further, the seal packing 50 is interposed in the gap between the tip surface 305 of the insertion port 303 of the stainless steel pipe 300 and the second packing seat 16 of the socket portion 11, and is exposed between the cushion packing 40 and the seal packing 50. The entire tubular wall surface 304 of the insertion port 303 of the stainless steel tube 300 is covered with the tubular body 60. Further, the nut 35 is screwed into the bolt 30 that is a headed bolt that is inserted in the bolt insertion hole 14 of the flange receiving portion 13 and the bolt insertion hole 22 of the loose flange 20 in a loosely fitted state, and the loose flange 20 is It is tightened by the nut 35. As a result, the cushion packing 40 is compressed in the axial direction, and moreover, the first packing seats 15 and 23 of the receiving opening 12 and the loose flange 20 and the tube wall surface 304 of the insertion opening 303 of the stainless steel tube 300 are pressed together. Therefore, the cushion packing 40 presses the insertion opening 303 of the stainless steel pipe 300 to position the stainless steel pipe 300, and seals the tip surface 305 of the insertion opening 303 of the stainless steel pipe 300 and the second packing seat 16 of the socket portion 11. The packing 50 adheres closely and exerts a sealing property. In the illustrated example, a plain washer 36 is combined with the bolt 30 and the nut 35, and the plain washer 36 is interposed between the loose flange 20 and the nut 35.

  The cushion packing 40, the seal packing 50, and the tubular body 60, which are applied to the respective connection points of the flexible joint 100, the vinyl chloride lining steel pipe 200, and the stainless pipe 300, are made of electrically insulating rubber.

  In the flexible joint 100 connecting the PVC lining steel pipe 200 and the stainless steel pipe 300 in the state shown in FIG. 1, the axes P1 and P2 of the PVC lining steel pipe 200 and the stainless steel pipe 300 are flexible as shown in the figure. Even if a bending displacement that is inclined with respect to the axis P of the joint is generated, the function of absorbing the bending displacement is exhibited. The situation in which the vinyl chloride lining steel pipe 200 and the stainless steel pipe 300 are flexibly displaced may occur due to a vibration such as an earthquake or a displacement between layers of a building.

  By the way, on the joint body 10 and the loose flange 20 described above, a nylon coating film indicated by a symbol F is formed by a fluidized-bed method. The nylon coating film F is in close contact with the cast iron skin surfaces (described later) of the joint body 10 and the loose flange 20 and has electric insulation itself. The locations where the nylon coating film F is formed include the inner peripheral surfaces of the bolt receiving holes 14 and 22 of the flange receiving portion 13 and the loose flange 20. The principle of the fluidized dipping method is to immerse a heated object such as the joint body 10 or the loose flange 20 in a floating layer of nylon powder suspended by an air flow to adhere the nylon powder to the object and melt it. Then, the nylon coating is brought into close contact with the object. The thickness of the nylon coating film formed by the fluid immersion method can be adjusted by the temperature of the object, the immersion time, and the like. In this embodiment, the nylon coating film F having a thickness of 300 μm or more is formed on the entire inner and outer surfaces of the joint body 10 and the loose flange 20 and the inner peripheral surfaces of the bolt insertion holes 14 and 22, but each bolt insertion The thickness of the nylon coating film F formed on the inner peripheral surfaces of the holes 14 and 22 is reduced to 300 μm or less by using a tool such as a drill. By doing so, the bolts can be inserted into the bolt insertion holes 14 and 22. The gap between the bolt 30 and the nylon coating film F to be secured is properly secured. By doing so, it is possible to prevent the nylon coating film F from being damaged by the bolt 30 inserted into the bolt insertion holes 14 and 22.

  Further, in the case of FIG. 1, the gap S1 between the nylon coating film F formed on the inner peripheral surface of the loose flange 20 and the insertion opening 303 of the stainless steel pipe 300 is wide enough to allow the bending displacement of the stainless steel pipe 300. It is Further, a required gap S2 is secured between the nylon coating film F formed on the inner peripheral surface of the receiving port 12 of the joint body 10 and the tubular body 60 mounted on the insertion port 303 of the stainless steel pipe 300. ing.

  FIG. 2 is a vertical cross-sectional view of the flexible joint 100 in which the thickness of the nylon coating film F is exaggeratedly illustrated. In this embodiment, the cylindrical socket portion 11 of the joint body 10 is assembled in correspondence with the receiving opening 12 on one side of the receiving openings 12, 12 provided at one end and the other end, respectively. The nylon coating film F is formed only on the loose flange 20, and the nylon coating film is not formed on the loose flange 20 to be assembled corresponding to the receiving port 12 on the other side. As shown in FIG. 1, the stainless steel pipe 300 that causes the corrosion phenomenon of dissimilar metal contact is connected only to the receiving port 12 on one side, and the PVC lining steel pipe 200 connected to the receiving port 12 on the other side is in contact with the dissimilar metal. Because it does not cause a corrosion phenomenon.

  As shown in FIG. 1 or 2, when the nylon coating film F is formed on the entire inner and outer surfaces of the loose flange 20 and the joint body 10 and the inner peripheral surfaces of the bolt insertion holes 14 and 22, the nylon coating film F is formed. Exerts the action of blocking the electric circuit. That is, as shown in FIG. 1, even if the stainless pipe 300 is flexed and displaced by the angle θ, the stainless pipe 300 may contact the cast iron skin surface 21 (see FIG. 2) of the loose flange 20. Blocked by the nylon coating F covering 21. Further, the contact of the cast iron skin surface 17 of the socket portion 11 of the joint body 10 with the drainage flowing through the pipe is also prevented by the action of the nylon coating film F covering the cast iron skin surface 17. Further, a steel bolt 30 (see FIG. 1) contacts the flange receiving portion 13 and the cast iron skin surfaces 17 and 21 of the loose flange 20 and is interposed between the steel nut 35 and the loose flange 20. The flat washer 36 made of steel (see FIG. 1) is also prevented from coming into contact with the cast iron skin surface 21 of the loose flange 20 by the action of the nylon coating film F covering these cast iron skin surfaces 17 and 21. .

  FIG. 3 is a partial vertical cross-sectional view of a flexible joint according to a modified example in which the thickness of the nylon coating film F is exaggeratedly illustrated. In this flexible joint, an inner peripheral surface of the joint main body 10 that comes into contact with drainage flowing through the internal flow passage of the joint main body 10, specifically, a cast iron skin surface 17 corresponding to the inner peripheral surface of the socket portion 11, and a stainless pipe. The cast iron skin surface 21 corresponding to the inner peripheral surface of the loose flange 20 opposed to the pipe wall surface 304 (see FIG. 1) of 300 and the loose flange opposed to the nut 35 (see FIG. 1) screwed into the bolt 30 in the axial direction. A cast iron skin surface 21 corresponding to the outer end surface of 20, a cast iron skin surface 21 corresponding to the inner peripheral surface of the bolt insertion hole of the loose flange, and a cast iron skin surface 17 corresponding to the outer end surface of the flange receiving portion 13. Nylon coating film F is formed on the surface, and the thickness of the nylon coating film F is 300 μm or more. Here, the outer end surface of the loose flange 20 is the outer end surface of the loose flange 20 that is located on the opposite side of the flange receiving portion 13 arranged so as to overlap the loose flange 20. Further, the outer end surface of the flange receiving portion 13 is an outer end surface of the flange receiving portion 13 located on the opposite side of the loose flange 20 arranged in an overlapping manner on the flange receiving portion 13.

  The nylon coating film F which is partially formed on the inner and outer surfaces of the joint body 10 and the loose flange 20 as shown in FIG. 3 also exerts the action of blocking the electric path at the formation location. That is, as shown in FIG. 1, even if the stainless steel pipe 300 is bent and displaced by the angle θ, the stainless steel pipe 300 is in contact with the cast iron skin surface 21 of the loose flange 20 and covers the cast iron skin surface 21. Blocked by nylon coating F. Further, the contact of the cast iron skin surface 17 of the socket portion 11 of the joint body 10 with the drainage flowing through the pipe is also prevented by the action of the nylon coating film F covering the cast iron skin surface 17. Further, a steel bolt 30 is in contact with the flanged receiving portion 13 and the cast iron skin surfaces 17 and 21 of the loose flange 20, and a steel flat washer is interposed between the steel nut 35 and the loose flange 20. The contact of 36 with the cast iron skin surface 21 of the loose flange 20 is also prevented by the action of the nylon coating film F covering these cast iron skin surfaces 17, 21.

  In FIG. 3, the loose combined with the receiving opening 12 on one side of the receiving openings 12, 12 provided at one end and the other end of the cylindrical socket portion 11 of the joint body 10 respectively. A nylon coating film F is formed only on the flange 20. This is because the stainless steel pipe 300 is connected only to the receiving port 12 on one side as shown in FIG.

  4 is an explanatory view showing an enlarged part A of FIG. 1, FIG. 5 is an explanatory view showing an enlarged part B of FIG. 1, and FIG. 6 is an explanatory view showing an enlarged part C of FIG. FIG. 7 is an explanatory view showing an enlarged part D of FIG. 1.

  According to the flexible joint 100 in which the nylon coating film F is formed in the form described with reference to FIG. 2 or FIG. 3, as can be seen by also looking at FIG. Nylon coating film F formed on the cast iron skin surface 17 corresponding to the inner peripheral surface of the joint body 10 that contacts with, more specifically, the cast iron skin surface 17 corresponding to the inner peripheral surface of the socket portion 11 is formed. The nylon coating film F cuts off the electric path that short-circuits the socket portion 11 of the cast iron joint body 10 and the stainless steel pipe 300 using the drainage as the electrolytic solution (first electric path cut-off portion). Further, as can be seen by also looking at FIG. 5, a nylon coating film formed on the cast iron skin surface 21 corresponding to the inner peripheral surface of the loose flange 20 facing the tube wall surface 304 of the stainless steel tube 300 with a gap S1. The electric line that short-circuits the stainless steel pipe 300 and the cast iron loose flange 20 is cut off by F (second electric line cut-off portion). Further, as can be seen by also looking at FIG. 6, a cast iron skin surface 21 corresponding to the outer end surface of the loose flange 20 and a cast iron skin surface 21 corresponding to the inner peripheral surface of the bolt insertion hole 22 of the loose flange 20 are formed. The nylon coating film F that is formed blocks the electric path that short-circuits the loose flange 20, the flat washer 36, and the bolt 30 (third electric path cut-off portion). Further, as can be seen by also looking at FIG. 7, the cast iron skin surface 17 corresponding to the inner peripheral surface of the bolt insertion hole 14 of the flange receiving portion 13 and the cast iron skin surface 17 corresponding to the outer end surface of the flange receiving portion 13 are formed. The nylon coating film F cuts off the electric path that short-circuits the flange receiving portion 13 and the bolt 30 (fourth electric wire cut-off portion).

In the flexible joint 100 shown in FIG. 2 or FIG. 3, the drainage plays a role of an electrolytic solution and causes the dissimilar metal contact corrosion phenomenon on the flexible joint 100 side under the above-mentioned first to fourth conditions. This is a case where the electric circuit interruption effect is impaired at all of the electric circuit interruption sites (the areas indicated by reference characters A to D in FIG. 1), and even if only one of the first to fourth electric circuit interruption sites has the electric circuit interruption effect. When enabled, dissimilar metal contact corrosion phenomena do not occur. It is highly possible that the situation in which the electric circuit interruption action is impaired at all of the first to fourth electric circuit interruption sites occurs during operation of the flexible joint for piping applied to the longitudinal drainage pipe for housing. Low, practically unlikely. For example, when high-temperature wastewater flows and the nylon coating film F on the inner peripheral surface of the socket portion 11 is softened and broken, or foreign matter in the drainage damages the nylon coating film F or when cleaning the pipes. Even if the coating film F is damaged, the nylon coating film F at any of the other second to fourth electrical circuit interruption sites blocks the electrical path, so that the phenomenon of contact with different metals does not occur. Further, the location where the dissimilar metal contact corrosion phenomenon occurs without passing through the drainage is limited to the case where the stainless steel pipe 300 is flexibly deformed and comes into contact with the loose flange 20 made of cast iron. However, since the nylon coating film F is formed on the inner peripheral surface of the loose flange 20 facing the tube wall of the stainless steel pipe 300 at the second electric circuit interruption portion shown in FIG. This serves to prevent contact between the 300 and the cast iron skin 21 of the cast iron loose flange 20. In this respect, although it is undeniable that the nylon coating film F is damaged by the collision with the stainless steel pipe 300 and the stainless steel pipe 300 comes into contact with the cast iron skin surface 21 of the loose flange 20, the stainless steel pipe 300 is not included in the loose flange 20. It is very difficult for the nylon coating F to collide with the peripheral nylon coating F itself, and the thickness of the nylon coating F is limited to 300 μm or more. Is unlikely to come into contact with the cast iron skin surface 21 of the loose flange 20. Further, the bolt 30, the flat washer 36, and the nut 35 that fasten the loose flange 20 to the flange receiving portion 13 are formed on the loose flange 20 by the nylon coating film F formed on the third electric circuit cutoff portion shown in FIG. Contact with the cast iron skin 21 is prevented. Similarly, the flange receiving portion 13 and the bolt 30 are prevented from contacting with each other by the nylon coating film F formed on the fourth electric circuit interruption portion shown in FIG.
When the nylon coating film F on the third and fourth electric circuit breaking portions is damaged, the bolt 30 or the flat washer 36 may rub against the nylon coating F at the time of tightening. However, the plain washer 36 is the nut 35. It is difficult for the bolt 30 to rotate during tightening, and it is unlikely that the bolt 30 rotates or the flat washer 36 rubs against the nylon coating film F during tightening. The plain washer 36 can be omitted.

  As shown in FIG. 1, in this embodiment, the tubular body 60 covering the entire pipe wall surface 304 of the insertion port 303 of the stainless steel pipe 300 exposed between the cushion packing 40 and the seal packing 50 is covered by the tubular body 60. The electric circuit that short-circuits the pipe wall surface 304 of the insertion port 303 and the receiving port 12 is cut off (fifth electric circuit cutoff portion). Even at this fifth electric circuit cut-off portion, it is undeniable that the tubular body 60 may be damaged by hitting the receiving port 12 and the stainless steel pipe 300 may come into contact with the cast iron skin surface 17 of the receiving port 12, but the tubular body 60 will contact the receiving port 12. Since the collision itself is very unlikely to occur, the situation in which the tubular body 60 is damaged and the stainless steel pipe 300 comes into contact with the cast iron skin surface 17 of the receiving port 12 hardly occurs.

  It is desirable that the cushion packing 40, the seal packing 50, and the tubular body 60 be integrally formed of rubber. By doing so, the cushion packing 40, the seal packing 50, and the tubular body 60 are respectively formed. Not only the number of parts is reduced as compared with the case where the cushion packing 40 and the seal packing 50 are separated, but also the entire tubular wall surface of the insertion port 303 of the stainless steel pipe 300 exposed between the cushion packing 40 and the seal packing 50 is ensured by the tubular body 60. As a result, the corrosion phenomenon of dissimilar metal contact caused by the contact between the pipe wall surface 304 of the insertion port 303 of the stainless steel pipe 300 and the receiving port 12 is reliably prevented.

  At the connection portion between the flexible joint 100 and the PVC lining steel pipe 200 shown in FIG. 1, even if the PVC lining steel pipe 200 is flexibly displaced by an angle θ and comes into contact with the upper loose flange 20, the potential difference is small at this contact portion. Since the loose flange 20 made of cast iron and the thin-walled steel pipe 201 are only in contact with each other, and the PVC-lined steel pipe 200 has the hard vinyl chloride lining layer 202 of electric insulation on the inner surface of the thin-walled steel pipe 201, A situation in which the thin-walled steel pipe 201 of the lining steel pipe 200 and the socket portion 11 of the joint body 10 or the stainless steel pipe 300 are electrically connected by using the drainage flowing in the pipe line as an electrolytic solution does not occur. Therefore, the dissimilar metal contact corrosion phenomenon does not occur at the connection point of the PVC lining steel pipe 200 in the flexible joint 100.

  In the embodiment described above, an example in which the stainless steel pipe 300 is connected to only one of the receiving ports 12 of the flexible joint 100 has been described. It is also possible to adopt a configuration in which a stainless steel pipe is connected to each. In this case, the loose flange 20 having the nylon coating film F, the cushion packing 40, the seal packing 50, and the tubular body 60 corresponding to the respective receiving ports 12 and 12 of the one end and the other end of the joint body 10. , The bolts 30 and the nuts 35 are combined, and by doing so, the above-mentioned first to fourth electric path interruption portions and the fifth electric passage interruption portions are formed.

10 Joint body 11 Socket part 12 Receptacle 13 Flange receiving part 14,22 Bolt insertion hole 15,23 First packing seat 16 Second packing seat 20 Loose flange 30 Bolt 35 Nut 36 Flat washer 40 Cushion packing 50 Seal packing 60 Cylindrical body 300 Stainless steel pipe 303 Stainless steel pipe insertion port 304 Stainless steel pipe insertion port wall surface 305 Stainless steel pipe insertion port tip face F Nylon coating film

Claims (6)

An annular loose flange,
A joint main body having a tubular socket part and a receiving port continuously provided to the socket part, and a flange receiving part provided in the receiving port so as to be overlapped with the loose flange is provided,
Bolt insertion holes provided in each of the loose flange and the flange receiving portion,
A first packing seat that is provided in each of the receiving port and the loose flange and that cooperates with a pipe wall surface of an insertion port of a stainless pipe that is inserted into the receiving port and the loose flange in a loosely fitted state to clamp the electrically insulating cushion packing;
A second packing seat that is formed by the end surface of the socket portion and that presses an electrically insulating seal packing between the end surface of the insertion opening of the stainless pipe and the second packing seat;
The inner peripheral surface of the receiving port is a cast iron flexible joint for connecting stainless pipes, which is adapted to face the insertion port of the stainless pipe on which an electrically insulating tubular body is mounted,
An inner peripheral surface of the joint body, which comes into contact with wastewater flowing through the internal flow path of the joint body,
An inner peripheral surface of the loose flange facing the pipe wall surface of the stainless pipe,
An outer end surface of the loose flange located on the opposite side of the flange receiving portion arranged in an overlapping manner on the loose flange, and an inner peripheral surface of the bolt insertion hole of the loose flange,
An outer peripheral surface of the flange receiving portion located on the opposite side of the loose flange, which is arranged to overlap the inner peripheral surface of the bolt insertion hole of the flange receiving portion and the flange receiving portion,
A cast iron flexible joint for connecting stainless steel pipes, characterized in that a nylon coating is formed to cover the.   The socket is continuously provided at each of the one end and the other end of the socket portion of the joint body, and the loose flanges are separately combined with the flange receivers provided at each of the sockets. The cast iron flexible joint for connecting a stainless steel pipe according to claim 1, wherein the bolt receiving hole is provided in each of the flange receiving portion and the loose flange.   The nylon coating film having a thickness of 300 μm or more is formed on the entire inner and outer surfaces of the loose flange and the joint body and the inner peripheral surface of each of the bolt insertion holes by a fluid immersion method. A cast iron flexible joint for connecting the described stainless pipes.   By reducing the thickness of the nylon coating film formed on the inner peripheral surface of each bolt insertion hole to 300 μm or less, the gap between the bolt and the nylon coating film inserted into each bolt insertion hole is reduced. The cast iron flexible joint for connecting a stainless steel pipe according to claim 3, which is secured.   The cast iron flexible joint for connecting stainless steel pipes according to any one of claims 1 to 4, wherein the bolt and the nut are combined with a flat washer that is superposed on the outer end surface of the loose flange.   The bolt is a headed bolt that is inserted into the bolt insertion hole of the loose flange through the bolt insertion hole of the flange receiving portion, and the nut is screwed into the bolt protruding from the bolt insertion hole of the loose flange. The cast iron flexible joint for connecting a stainless steel pipe according to any one of claims 1 to 5.

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