JPS6322389A - Pressure tank for corrosive substance - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to an improvement in a pressure tank for corrosive substances, in particular a steel tank for hot water, which has an anti-corrosion coating on its inner surface.

[Conventional technology]

Typically, ceramic or glass lined hot water tanks have a cylindrical sidewall with a cylindrical top that has a concave inner surface that defines a "plus" head for the tank. The bottom of the tank has a convex inner surface defining a "minus" bottom of the tank. This configuration has been manufactured for many years, and the technology usually involves welding the top to a cylindrical side wall rolled from a flat rectangular blank, and creating a tank with an open bottom. It consists of an internal coating. The bottom, which is pre-coated and has a convex inner surface, is then welded to the base of the tank. This will be explained with reference to the drawings.

Hot water tanks usually store water at 48.9°C (120°F).
It is utilized in residential and commercial facilities for heating and storage to temperatures between 160° F. and 71.1° C. (160° F.), and the heat source is usually an electric heating element or a gas-fired heating device. A typical tank used in an electric type water heater is shown in FIGS. 1 and 2. Tank 10 is comprised of a cylindrical sidewall 12, a first or bottom end member 14, and a second or top end member 16. Each end member of the tank is welded to the cylindrical side wall to seal the tank and provide a compartment in which the water is heated and stored as hot water. For example, water inlets and openings for electrical heating elements in the side wall 12 are not shown. Typically, hot water is removed from the top of the hot water heater through an outlet 18.

Assembly of conventional hot water heaters is typically accomplished by welding the top member roller to the sidewall 12. In FIG. 2, the top member 16 has a peripheral end portion 20 that fits within a sidewall end portion 22. In FIG. The top member 16 is welded to the sidewall upper portion 22 by a band weld 24, thereby connecting the top edge 26 to the outer wall 28 of the top member 16. Thus, a bottom open-ended tank with the top member] 6 in place is provided, where the inner surface of the tank is coated with a corrosion-protective coating together with the inner surface of the top member. This involves cleaning the inside of the tank and top member using an abrasive or pickling method to remove oxides and contaminants from the inner surface of the steel material, and at the same time etching the surface and applying a corrosion-resistant coating to the inner surface of the tank. This is achieved by sufficient bonding. After cleaning, the interior of the tank is coated with a glaze slurry, which is commonly practiced in the art and consists essentially of finely ground ceramic powder suspended in water. The coating is applied to all inner surfaces, including the concave inner surface 30. of the top member 16. and around the bond area along the tank side wall inner surface 34 inside the tank.

To facilitate welding of the bottom end member 14 to the tank side wall, the coating is wiped from within the bottom periphery and bottom end 36 of the tank side wall. The coated tank is then passed through a dryer to remove moisture from the glaze slurry before being placed in a glaze furnace typically operated at a temperature of 871'C (1600F). As a result, a smooth corrosion-resistant coating is formed inside the tank.

The bottom end member 14, which has a convex inner surface, is cleaned and glazed in the same manner as the tank shell assembly described above. The glaze coating is wiped off in area 38 and the sidewall 12
is located adjacent to the cleaned end portion 36 of. Bottom end member 1
4 is inserted into the tank. The coating on the inner surface 40 of the tank bottom is contacted with the coating on the inner surface 34 of the side wall]2. A weld 42 is applied between surfaces 36 and 38.

Typically, the weld 42 is sufficiently spaced from the bond area 44 of the coating on the inner surfaces 34 and 40 that the heat from the welding process will not degrade the coating. Usually, this welding is carried out by a type of submerged arc welding process.

[The problem that the invention attempts to solve]

Although such a structure is satisfactory as a hot water tank,
Tank failure due to hot water at the tank top, which increases corrosion at the seam between the tank top and sidewalls, has become an industrial problem.

Such damage is usually caused by interruptions in the glaze or coating applied to this area during the coating process. Another disadvantage with this construction is that it requires the material wall thickness of the "minus" bottom of the tank to be considerably thicker than the side walls of the tank, thus ensuring that under pressure the tank bottom, at least its central area However, care must be taken to ensure that the film does not break due to bending and cracks. Another disadvantage of the "minus" head design is that it considerably reduces the assembled tank capacity and therefore requires the overall height of the hot water tank to be considerably larger.

Hot water at the top of the tank increases the corrosion reaction.

The reason is that the oxygen-containing released gases are free to chemically react with and corrode the bare metal exposed from the defective glaze or coating. Furthermore, it has been recognized that the rate of chemical reactions doubles for every 100C increase in temperature. Additionally, the abutment of the tank top and tank side attachment is not always perfect due to cuts or other imperfections in the tank sidewalls and the outer periphery of the cylindrical portion of the top. Therefore, even if the greatest care is taken in applying the glaze material, there will be some uncoated area at the junction between the tank top and tank sidewalls.

To increase the tank capacity, it is advantageous to provide the hot water tank not only with a "plus" head but also with a "plus" bottom. This has the potential to increase tank capacity for a given diameter and reduce tank height due to the "plus" head shape. However, in the current state of the art, no technique is known for joining a "plus" bottom to a tank after the tank with a welded "plus" top has been coated with a ceramic material.

If a pre-coated tank "plus" bottom edge is welded to the tank sidewall in the same manner that the top is welded, the coating film will be severely degraded or damaged by the welding heat. become. Such deterioration results in uncoated parts of the steel material, which are corroded by hot water.

Considering prior art tank constructions that provide "plus" heads and bottoms for cylindrical tank constructions, U.S. Pat. No. 3,199,711 discloses a firefighting tank containing pressurized material. has been done. This tank is constructed from a material that will not be corroded by its contents;
Therefore, there is no protective or anti-corrosion coating inside the tank. For example, when containing a fire extinguishing fluid, the tank is made of copper or a similar material and the components are soldered together. A similar system is shown in US Pat. No. 3,952,904, in which the structural material is not corroded by its contents. A plastic bottom with a concave internal shape is sonic welded to the plastic sidewall of the barrier and the joint is provided with a seal to prevent leakage. This system does not require any protective coating and if the welding heat affects the internal protective coating,
No welding is used in the joints.

Another type of container having a "plus" end on the cylindrical tank sidewall is disclosed in U.S. Pat. No. 3,098,577 and U.S. Pat. No. 3,132,618. None of these contemplate an internal coating on the tank surface to prevent corrosion by its contents. The aforementioned problems with conventional hot water tank structures are not solved by the tank structures disclosed in these patents.

[Means for solving problems]

According to the invention, the tank for containing corrosive substances has a corrosion-protective coating on its inner surface.

The tank is constructed from a cylindrical steel sidewall and first and second end members that are secured to and close the tank. At least the first end member has a concave shape and has a shape such that the inside of the tank projects outward. At least the first end member is fixed to the tank by a connecting member, and the connecting member is an annular body portion that controls the action of welding heat on the corrosion-resistant coating applied in advance to the inner surface of the tank side wall and the inner surface of the first end member. It is equipped with The first portion of the annular body portion is connected at a first connection at the periphery of the first end member. The second portion of the annular body portion is connected to the cylindrical end portion of the side wall at a second connection. 1st and 2nd
The portion and the corresponding one of the first and second connections are coated with a corrosion-resistant coating. The other of the first and second portions is a welded connection. The annular body portion is adapted to control the temperature at which the coating is heated by spacing the weld joint a predetermined distance from the corrosion-protective coating.

The invention further provides a method for connecting a steel end member to a corresponding end of a steel tank for containing corrosive substances. The tank includes a cylindrical side wall having an inner surface, an end member thereof having a circular concave shape with the inside of the tank protruding outward, and a connecting member connecting the end member to the end of the tank side wall. There is. The method of the present invention includes:
It consists of connecting a connecting member to the end member or tank side wall. The inner surface of the tank, the concave inner surface of the end member and the exposed portion of the connecting member are coated with a corrosion-resistant coating.

The connecting member is welded to the end member or tank side wall. To complete the connection of the end member to the tank side wall, the coated exposed portion of the connection member abuts the coating on the inner surface of the end portion of the inner surface of the tank side wall to form a coating bond. The temperature at which the membrane bond is heated is controlled by predetermining the rate at which the coupling member spaces the weld of the coupling member from the membrane bond.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing preferred embodiments.

The invention is applicable to a wide variety of tank structures containing media that are corrosive to the tank material, such as steel tanks containing water, gas cylinders for acid gases, extinguishers and beer kegs.

A preferred embodiment of the invention is illustrated with a hot water steel tank construction. However, it will be clear that this embodiment is equally applicable to other tank structures.

Conventional tank construction of the type described above consists of a "plus" head at the top of the tank and a "plus" head at the bottom of the tank.
It has been used for many years when providing a "minus" head. A "minus" head would significantly reduce the capacity of the tank, considering its overall height. The bottom portion, which has a convex inner surface, must be formed from a thicker material than the side walls in order to withstand the pressure within the hot water tank. If the bottom is made of thin walled material, the bottom will buckle, creating an exposed area for coating cracks and corrosion, which can lead to tank failure. The wall thickness of the material for the bottom is typically in the range of 1.6 times the wall thickness of the material for the "plus" head section if the dish shape is similar, which is typically the thickness of the material for the side walls. Thicker.

This results in significant inventory problems, requiring at least three different wall thicknesses to be stocked depending on the part being formed. Additionally, special tools and machinery are required to manufacture the parts.

Providing a "plus" end at the bottom of the tank is a desirable embodiment in order to increase the capacity of the tank relative to its diameter, and to at least allow the use of thin walled materials in the bottom of the tank. However, after the assembly of the tank side wall to the tank top and the coating and subsequent welding of the "plus" bottom of the tank to the tank side wall, welds will be made to the tank bottom portion in the area being coated.

The heat from welding is transmitted directly through the tank bottom wall member and deteriorates the ceramic coating. This becomes even more problematic when non-ceramic coatings are used, such as polymeric coatings containing various suitable polyamides, such as SUILON®.

Deterioration of such a coating leads to its destruction and loss of anti-corrosion properties.

As mentioned above, another problem with normal tank construction is that
Some of the tank failures are due to damage to the coating in the top seam area of the tank top to the sidewall. Therefore, when constructing the top of a hot water tank, it is desirable to have a structure that avoids such damage.

In the present invention, a connection is provided at the end of the cylindrical side wall of the tank so that it can be configured in use either at the top or at the bottom of the tank. As shown in FIG. 3, the cylindrical tank side wall 12 has a "plus" bottom end member 46 attached to its bottom end 36. Bottom end member 46
has a concave inner surface 48 such that the inside of the tank protrudes outward. In this embodiment, the concave inner surface 48 has a semi-elliptical shape. However, this end is
(American Society of Mechanical Engineers) Boiler and Pressure Vessel Code, Section ■, Part 1, 1977 Edition.
ape). Due to the essentially constant material thickness, the outer surface 52 of the end member 46 has the same shape. A connecting member 54 having an annular body portion is utilized to connect the end member 46 to the interior of the side wall 12 .

In one form of the invention, connecting member 54 is connected to end member 46
is secured to the outer peripheral edge 56 of the.

This connection is made by welding or other suitable fastening means.

Prior to assembly of the end member 46 to the cylindrical side wall 12 of the tank, the inner surfaces 34 and 48 of the tank and the exterior of the connecting member 54 are coated.

Any excess coating applied to the gap area 57, which is subsequently welded to the tank wall, is wiped off.

The inner edge of the tank is also wiped to leave an opposing uncoated surface for welding. The end member 46 is then inserted into the end 36 of the cylindrical side wall such that the coatings on the coupling member 54 and on the inner surface 34 of the tank overlap and contact each other to seal the end of the tank. . Connecting member 54 is then welded to end 36 by band weld 58. Connecting member 54 is arranged and configured to control the temperature at which the overlapping coating bond is heated during welding thereof to end portion 36. This temperature control is effected by predetermining the spacing of the connecting member 54 and the strip weld 58 from the joint of the overlapping coatings and from the coatings on the inner surfaces of the end members and tank side walls.

The connecting member 54 conducts heat from the area of the weld 58 to the bond of the coating. Trial and error allows the temperature at which the coating is heated to be controlled from the rate at which the connecting member spaces the weld from the bond of the coating. It is desirable to control the temperature within a range that minimizes or avoids the effect of welding heat on the coating at the joint. Further, it is desirable to control the temperature to at least a range where the coating at the joint portion is fused during the welding operation. If it is desired to increase the temperature at the membrane joint, the height of the joint H may be shortened, but the mass of the joint member may be reduced, or alternatively it may be made of a material that conducts heat rapidly to the joint area. Make it. Details of the overlap and formation of the coating bond and the welding techniques are described in the various embodiments of the invention shown in FIGS. 4-9.

A cylindrical base or stand 60 is provided to complete the assembly of the bottom of the hot water tank. stand 60
is an inward stepped portion 6 fixed to the inner surface 64 of the connecting member 54.
2. The stand 60 has a peripheral bottom end 66 which extends below the lowest portion 68 of the end member 46 and which is provided for when the hot water tank is placed upright in use. It has the function of a supporting leg.

The coating on the connecting member 54, the end member 46 and the interior 34 of the tank side wall 12 is shown in detail in figure m14. Connecting member 54 includes an annular skirt whose outer surface 76 is welded at 74 to outer surface 56 of end member 46 . The skirt extends outwardly of the end member 46 and is stepped in region 84 to facilitate insertion of the end member 46 into the tank. The coating 70 applied to the interior surface 34 can be a fired ceramic composition or a polymeric composition such as "nylon." In forming the ceramic or glass lining coating as described above, a slurry containing ceramic particles is coated on the inner surface 34 of the tank sidewall. The lower peripheral edge portion 72 of the inner surface of the sidewall has no coating material applied thereto, so this area remains uncoated after the tank sidewall has been dried and fired. End member 46 and connecting member 54
It also has a slurried ceramic coating applied over the entire inner surface 48 of the end member and overlaps in the weld area including the connection of the connecting member 54 to the outer end portion 56 of the end member 46. The outer surface 76 of the connecting member is also coach inked with slurried material, thereby forming an essentially continuous coating 78.

Lower end portion 80 is left uncoated to form an uncoated peripheral area 80 around the periphery of coupling member 54 .

The coating applied to the inner surface of the tank side wall and end member 46 is then glazed, hardened or fused. The end member 46 is then inserted into the tank end so that the final coated surfaces 70 and 78 are brought into contact at the lower region 82 of the connecting member outer surface 76 and the tank side wall coating 70. Such coating contact forms a seal around the bottom edge of the tank, preventing water leakage and effectively forming a continuous coating from the side wall to the end member 46. To provide parallel coating surfaces forming a coating bond,
A predetermined contact circumferential band area is provided for the contact coating. Such a contact band area provides contact between the coatings over the height of the band, thereby forming a seal around the peripheral coating bond. As previously mentioned, if it is difficult to provide a seal around the peripheral coating bond, the connecting member allows the coating bond to heat in that area and seal the bracket without overall deterioration of the coating. The temperature at which the coating is fused can be controlled without losing the sealing potential at the joint. This is particularly amenable when the coating is made of a polymeric material such as "nylon" which can be fused when heated to the appropriate temperature. A sealant such as an epoxy coating or gasket can be applied to the joint before welding. In that case, the welding heat is controlled by the connecting member so that the epoxy sealant or gasket does not deteriorate.

The end member 46 is now in position to be secured to the tank side wall 12. The coupling member 54 extends a sufficient distance outwardly of the coating coupling portion 82 so that when the uncoated portion 80 is welded to the uncoated portion 72 of the tank side wall, welding heat is minimal and both the coupling portion 82 and the interior thereof are welded. The non-corrosive properties of the coating are not degraded in this region.

This connecting member 54 changes the welding area from the coating to the connecting member 5.
4-1-, but also on the inner surface of the end piece 46, so that when the welding is completed, a continuous coating is obtained on the side wall area and the bottom of the tank. The welding used to connect the connecting member 54 to the outer circumferential edge 56 of the end member is performed before the coating is applied to the end and the connecting member, so that the welding heat of this connection is transferred to the subsequent coating process. It has no effect. In fact, the coating can overlap the seam area and the weld and provide a coating and protection so that the area is not corroded by the containing fluid, which is usually water.

It will be apparent that the principles of the invention may be accomplished in various configurations of connecting the end member to the tank side wall. Such an arrangement is shown in FIGS. 5-9, in which the surfaces exposed to the containing liquid are coated with a corrosion-resistant material.

As shown in FIG. 5, the end member 46 has a concave inner surface 86, which is elliptical, toric-shaped, as shown in FIG.
It can have a spherical compound shape or a hemispherical shape. Connecting member 54 has an annular skirt portion 88 extending outwardly from the interior of the tank. In this embodiment, mechanism-1
The - portion 88 is a continuous portion of the wall portion 90 of the end member bent by the reverse layer bend portion 92 . The end member 46, which is formed from a wood-consistent material thickness preparation, is coated before being inserted into the tank side wall 12, which has a coating on the inner surface 34. The coating forms a bond in region 94 that effectively forms a seal around the bottom of the tank. Areas 72 and 96 outside the skirt portion are provided with uncoated portions of the tank sidewalls so that the end member 46
A strip weld 98 is utilized to connect the tank side wall 12 to the tank side wall 12. The skirt portion of the connecting member 54 extends a sufficient distance outward from the inside of the tank so that the connecting member 54
At least in the region of the joint 94 on the periphery of the weld 9, the welding heat does not deteriorate the non-corrosive properties of the coating.
8. By providing this reverse ply bend 92 on the end member 46, the entire end member is manufactured from a single steel sheet material stock without any welding operations to the reverse ply bend 92.

An alternative embodiment of a hot water tank end member 46 mounted and coupled to the tank side wall 12 is shown in FIG. In this type of configuration, the top and bottom members can be of the same diameter. This method greatly reduces the inventory costs of having separate tank end pieces in completing a tank structure. End member 46 has a concave inner surface 100. The connecting member 54 has a skirt portion 102 whose top end is connected to the bottom portion 1 of the end member 46.
An angle is formed toward 04. A band weld at 106 connects the angular portion of the skirt to the end member 46.

The connecting member 54 and end member 46 assembly is coated by a method similar to that used for coating other embodiments. The inner surface 34 of the sidewall is coated so that when the end member 46 is inserted into the tank sidewall 12;
The coatings are adapted to contact and form a seal at bonding region 110. Once the end member is assembled into the tank,
The uncoated portions of tank end 72 and connecting skirt 112 are connected by band welds 114, the heat of which does not affect the coating in area 110. The embodiment of FIG. 7 is modified from that of FIG. 2, in which an arrangement is provided which allows the use of the same end member as the other end member used to connect to the top of the tank side wall 12 by the technique shown in FIG. In order to adapt to the wall thickness of the connecting member 54, the side wall 12 is stepped in the region 116. In this embodiment,
Connecting member 54 is a skirt portion 118 that is welded at 120 to peripheral end portion 122 of end member 46 . The end member 46 with the connecting member 54 is coated independently from the sidewall inner surface 34. In coating the end piece 46, the coating covers the seam area including the weld 120. After the end member 46 is inserted into the tank end section, the end member 46 is secured by the weld 124. Skirt part 1
18 extends sufficiently outwardly of the tank to position the weld 124 at a sufficient distance from the area 126 and around the tank inner surface 34.
The coatings on the two and connecting members 118 contact each other. The welding heat of the weld 124 will not degrade the coating in or within this region, including the coating on the interior 128 of the end member 46.

Another configuration for coupling the end member 46 to the tank side wall 12 is shown in the eighth embodiment.
As shown in the figure. Connecting member 54 includes a skirt portion 130 that is welded to peripheral end 134 of end member 46 at seam 132 . Then the welding assembly is the 8th
It is bent inwardly to the extent shown to provide a guide for inserting the end member 46 into the tank sidewall 12. Tank side wall] 2 is provided with a coating in the same manner as explained in FIG.
The end member of the tank with the
30 extends below the outer wall portion 138. A fairly close and acceptable fit is provided between the uncoated portion of the outer surface 138 of the skirt portion 130 and the corresponding uncoated portion 72 of the tank sidewall. The weld 140 is located at a sufficient distance from the coating bond 141 to avoid degrading the coating portion. Similarly, the skirt portion 130 is adapted to space the weld 140 from the interior coating 136 of the end member 46.

It is also possible to connect the tank side wall to a "plus" end, ie, a bottom end member or a top end member, where the inner diameter at the circumference is larger than the outer diameter of the tank shell. This type of connection is shown in FIG. 9, where the tank side wall 12 is provided with a coupling lug 54 fixed at a first portion 142 to the exterior 144 of the tank side wall. The inner surface 34 of the link, including the connecting region 146 and the remaining exposed outer surface 148 of the connecting member 54, is provided with a corrosion-resistant coating.

The "plus" end member 46, which serves as the bottom member, has a coating on its inner surface 48 before it overlaps the coating on the connecting member surface 148 in area 1.50.

The second portion 152 of the connecting member is connected at 154 to the end member 4
6 to complete the assembly of the end member 46 to the tank side wall 12. The connecting member 54 is adapted to space the weld strip 154 a sufficient distance from the overlap region 1.50 to control the temperature to which the overlap region of the coating is heated during the welding operation.

This technique allows the large end to be assembled into a small tank shell.

Another stand assembly for a hot water tank is shown in FIG. The end member 46 is assembled to the tank side wall 12 in a structure generally shown in FIG. For hot water tanks insulated by a foam material, such as urethane foam, a preformed foam substrate 156 is provided that receives the shape of the end member 46. With the tank bottom placed on the foam base 156, the shell assembly 58 is assembled around the base and the tank is mounted between the tank exterior 158 and the tank sidewall 12, and around the top portion (not shown). 160 blank spaces are left. Once the assembly is complete, a foam material is introduced into the cavity 160, filling the cavity with the insulating foam material and once the foamed urethane composition is cured.
The structure is solidified. This provides a rapid assembly technique for a hot water tank structure in which the shell 158 containing the platform 162 is completed and ready for use, where the platform is attached to the projecting legs. It includes 164.

As discussed in connection with FIG. 2, prior art techniques for assembling the top member to the tank end have resulted in failure. This is the same technique for assembling the [brass] bottom end of the tank as the "plus" top end of the tank is similarly assembled as described in connection with Figures 3-10. can be avoided in tanks with a "minus" bottom. In joining the top member to the tank, a skirt extension or the like 60 as shown in FIG. 3 is not required. If the foam insulates the tank, the top of the tank shall be provided with suitable openings and piping arrangements for the outlet of the hot water tank;
It is possible to make the shape shown in FIG. 10 \opposed without the placement of legs or the like.

[Operation and effects of the invention]

The assembly method of the present invention provides a "plus" head structure at each end of the tank to isolate the welds in order to join the tank end member to the tank side wall without degrading the tank coating. This increases the tank capacity and also allows the use of thin walled materials in the tank since the concave shape of the tank end can accommodate considerably higher stresses without sagging. By reducing the material thickness of the end members to a value equal to or less than the wall thickness of the tank side wall, considerable savings are achieved in tank construction. For example, in a tank structure where the top is also utilized as the bottom and is assembled in the manner shown in FIG. 7, a material saving of approximately 8% is achieved. For a tank end shape with an end of the elliptical shape of FIG. 3, or a similar composite toric-sphere shape, a material saving of approximately 20% is achieved. If the tank ends are hemispherical, the material savings will be approximately 31%. This is achieved due to the fact that if the tank end approximates a hemispherical shape, a considerably thinner material can be used for the tank end to accommodate the tank pressure.

The relationship of the material thickness of the tank end member to the wall thickness of the tank side wall in order to resist the stresses caused by the pressure within the tank is well understood in pressure tank design. This allows for the use of thin walled materials for the tank end, and in designing the tank end to accommodate certain stresses, it is possible to considerably reduce the amount of material used in the manufacture of the tank. Surprisingly, in the conventional construction of FIG. 2, which has a "plus" head configuration at the top of the tank, the material wall thickness at the top of the tank is typically 1.6 times the tank sidewall thickness, and the material thickness at the bottom is For "minus" heads, the wall thickness typically averages 1.9 times the tank sidewall thickness. on the top and bottom of the tank.
In the present invention where a "plus" head configuration is used, both ends can have a wall thickness that is less than the wall thickness of the tank sidewall. In this way, great material savings of up to 28% are achieved and damage to the tank in the region of the connection between tank top and side wall is greatly reduced. Moreover, this design achieves significant savings in glaze processing energy, which can range from 10 to 30%, depending on the shape of the tank end. Another form of energy savings can be realized by the overall reduction in tank surface area relative to the volume of water contained. The reduced tank surface area results in less heat loss and therefore less energy required to maintain the water at the desired temperature.

The method of the invention is carried out as already described, an important advantage of one of the embodiments of the invention being that it is coated independently of the tank side walls or end pieces. The interior of the sidewall can therefore be inspected for defects before the end member is joined to the tank sidewall. Furthermore, the threads of the outlet 18 can also be inspected independently. This is particularly important when ceramic slurry coatings are applied inside tanks. Furthermore, if the tank end piece is coated with a ceramic slurry, the effectiveness of the coating can be tested, especially around the seam area of the connecting piece.

[Brief explanation of drawings]

Figure 1 is a perspective view of the hot water tank of the conventional device, and Figure 2 is the perspective view of the hot water tank of the conventional device.
3 is a sectional view through the bottom of the hot water tank with a method of joining the "plus" bottom to the tank in accordance with an embodiment of the present invention; FIGS. FIG. 10 is a schematic cross-sectional view of various embodiments of the present invention for coupling a "plus" bottom of a hot water tank to a side wall of the tank according to the present invention; FIG. FIG. 6 is a cross-sectional view of the hot water tank showing another arrangement. 10 is a tank, 12 is a side wall, 14 is a first end member, 16 is a second end member, and 54 is a connecting member. Applicant Air Clean, Engineering, Products

Claims (9)

[Claims] (1) A tank comprising a steel cylindrical side wall and first and second end members fixed to the tank and closed, wherein at least the first end member has a concave shape and the inside of the tank protrudes outward. In a steel pressure tank for corrosive materials having a corrosion-resistant coating on the inner surface, the first end member is fixed to the tank by a connecting member, the connecting member having an annular body portion, and the first end member is fixed to the tank by a connecting member, and the connecting member has an annular body portion and the inner surface of the tank side wall and the The influence of welding heat on the corrosion-resistant coating applied in advance to the inner surface of the first end member is controlled, and the first portion of the annular body portion is a first connecting portion of the periphery of the first end member. Further, a second portion of the annular body portion is connected to a cylindrical end of the side wall at a second connecting portion, and one of the first and second portions and the corresponding first or second connecting portion are connected to the cylindrical end portion of the side wall. the other of the first and second portions is welded together, the annular body portion spacing the welded joint a predetermined distance from the corrosion-resistant coating; A pressure tank characterized in that the temperature at which it is heated is controlled. (2) the second connecting portion is coated, the second portion of the annular body portion is connected to an outer surface of the side wall cylindrical end, and the first portion of the annular body portion is connected to the outer surface of the side wall cylindrical end; It is welded to the circular inner surface of the first end, and the annular body portion is coated with the coating and is in contact with the coating on the inner surface of the first end in the circumferential direction. The tank according to claim 1, wherein: (3) The annular body portion is configured to control the temperature of the contacting coating so as to fuse the contacting coating during welding of the first connecting portion. The tank according to claim 1 or 2. (4) The annular body portion extends outwardly of the first end member and is covered with the coating applied to the inner surface of the first end member, and the annular body portion extends inside the side wall. slidably received by a cylindrical end, the coating on the inner sidewall surface circumferentially contacting the coating on the toroidal body portion to couple the inner sidewall coating and the toroidal body portion coating; forming a seal at the inner surface of the sidewall and the adjacent portion of the annular body portion are uncoated outwardly of the coating bond, and the uncoated sidewall and the annular body portion are welded together. Tank according to claim 1, 2 or 3, characterized in that they are connected. (5) The second end member has a concave shape, the inside of the tank protrudes outward, and is welded to the side wall so that a peripheral edge is formed between the second end member and the second end wall of the side wall. 5. Tank according to claim 4, characterized in that it forms an internal joint and the coating extends over the internal joint. (6) The annular body portion is integral with the first end member and is formed from a reverse extension of the end member formed by a reverse bent portion of a peripheral edge of the first end member. 5. The tank according to claim 4, wherein the reverse bent portion forms the first connecting portion. (7) The first end member has an elliptical shape, a toric-spherical composite shape, or a hemispherical cross-sectional shape along the diameter of the first end member. The tank according to any one of the ranges 1 to 6. (8) The first end member has a substantially uniform wall thickness that is less than or equal to the substantially uniform wall thickness of the sidewall. The tank according to any one of items 1 to 7. (9) In a tank containing a corrosive substance and comprising a cylindrical side wall having an inner surface and a circular end member having a concave shape such that the inside of the tank protrudes outward, the end member is attached to the end of the side wall. A method of joining the steel end member to a corresponding end portion of a steel tank by a connecting member to be joined, the method comprising: joining the connecting member to the end member or the tank side wall, and connecting the inner surface of the tank, the end coating the inner concave surface of the member and the exposed portion of the connecting member with a corrosion-resistant coating;
The connecting member is welded to the end member or the tank side wall to complete the joining of the end member to the tank side wall, and the coated exposed portion of the connecting member is welded to the end member inner surface or the tank side wall. the temperature at which the coating bond is heated by contacting the coating on the inner surface to form a coating bond, and by the coupling member spacing the welded portion of the coupling member a predetermined distance from the coating bond; A method for joining an end member to an end of a tank side wall, the method comprising: controlling the end of a tank.