Field of the invention

The present invention relates to a method for replacing a plate pack of the Plate&Shell -type plate heat exchanger and an openable plate heat exchanger according to the preambles of the independent claims presented below.

Background of the invention

Plate and Shell -type welded plate heat exchangers are previously known, which heat exchangers are composed of a plate pack formed by heat exchange plates and a shell surrounding it, functioning as a pressure vessel. The plate pack is formed of heat exchange plates having openings and the heat exchange plates are attached to each other as plate pairs, the inner parts of which plate pairs are arranged in connection with each other via flow channels formed by the openings of the heat exchange plates. A primary circuit of the heat exchanger is formed of the flow channels formed by the openings of the heat exchange plates and the inner parts of the plate pairs that are in connection with these flow channels. An outer casing of the heat exchanger surrounds the plate pack. A secondary circuit of the heat exchanger is formed of the shell part of the heat exchanger, which shell part is in connection with the spaces between the plate pairs of the plate pack.

Inlet and outlet connections for a first heat exchange medium, i.e. inlet and outlet tube connections of the primary circuit are conventionally welded directly to the plate pack of the plate heat exchanger and also to the cover plate of the outer casing.

If the plate pack of the heat exchanger has damaged and it has to be replaced to new one, it is laborious to arrange a new plate pack in the construction since both the cover plate of the outer casing and the plate pack has to be re-constructed due to the inlet and outlet connections. Summary of the Invention

It is an object of the present invention to reduce or even eliminate the above- mentioned problem appearing in prior art.

The aim of the invention is to provide a novel construction of an openable plate heat exchanger, which also provides a novel method for replacing the plate pack of the openable plate heat exchanger. It is especially an object of the present invention to provide a method for replacing a plate pack of the openable Plate&Shell -type heat exchangers.

In order to achieve among others the objects presented above, the invention is characterized by what is presented in the characterizing parts of the enclosed independent claims.

Some preferred embodiments of the invention will be described in the other claims. A typical openable Plate&Shell -type plate heat exchanger according to the invention comprises at least

- a plate pack formed of heat exchange plates having openings and arranged on top of each other, and which plate pack comprises support plate on the both ends of the plate pack in the direction of the heat exchange plates and an outer surface defined by the outer edges of the heat exchange plates,

- an outer casing surrounding the plate pack, which casing comprises a first cover plate and a second cover plate mainly in the direction of the support plates of the plate pack and a shell connecting the cover plates, the first cover plate is arranged to be openable,

- inlet and outlet connections for a first heat exchange medium, arranged through the openable first cover plate of the outer casing, which connections are arranged in connection with the openings of the plate pack,

- inlet and outlet connections for a second heat exchange medium arranged through the shell of the outer casing, which connections are arranged in connection with the inside of the outer casing, i.e. with the outside of the plate pack, and

- an additional end plate having openings, which end plate is arranged between the first cover plate and the support plate of the plate pack, the openings of all plates (i.e. the support plate of the plate pack, the additional end plate and the openable first cover plate of the outer casing) are aligned to each other.

The additional end plate according to the invention has attached to the first cover plate and to the support plate of the plate pack on its outer periphery and the inlet and outlet connections for the first heat exchange medium are attached only to the first cover plate of the outer casing and/or the openings of the additional end plate, the connecting points between the additional end plate and the openings of the plate pack are free of the welded joints.

A typical method according to the invention for replacing a plate pack of the plate heat exchanger comprises at least the following steps:

opening the first cover plate of the outer casing and removing the plate pack attached to the first cover plate out from the outer casing,

- detaching the plate pack from the first cover plate so that the additional end plate remains in connection with the cover plate,

obtaining a new plate pack formed of heat exchange plates having openings arranged on top of each other, and which plate pack comprises support plate on the both ends of the plate pack in the direction of the heat exchange plates and an outer surface defined by the outer edges of the heat exchange plates,

arranging the new plate pack in contact with the additional end plate so that the openings therein are aligned to each other,

attaching, preferably welding, the support plate of the plate pack to the additional end plate only at its outer periphery, and

closing the heat exchanger by arranging the new plate pack attached to the first cover plate into the outer casing.

The present invention is based on an openable plate heat exchanger construction with replaceable plate pack. An additional end plate arranged between the openable cover plate of the outer casing and the support plate of the plate pack makes possible it that the plate pack can be easily replaced to new one. The old replaceable plate pack is detached from the joint between the support plate of the plate pack and the additional end plate attached to the openable cover plate of the outer casing. Correspondingly, the new plate pack is attached tightly to the additional end plate, but only at the outer periphery of the support plate of the plate pack.

The construction of the openable cover plate with the additional end plate according to the invention and cassette type plate pack makes possible to change the plate pack to a new one easily and without laborious work steps, thus ensuring that process downtime is kept to a minimum. The new plate pack can be delivered to the location of the plate heat exchanger and it can be welded to the additional end plate at the outer periphery of the support plate. There is no need for the new cover plate of the outer casing or the new inlet and outlet connections of the primary circuit since they are not attached tightly to the plate pack construction and thus they are not damaged during the replacing. Therefore, the plate pack as a spare part can be easily and quickly assembled and delivered, and it can be easily attached to the cover plate of the outer casing having the additional end plate according to the invention. The required welded joint between the support plate of the new plate pack and the additional end plate is not a part of the outer casing of the pressure vessel.

The method according to the invention is meant specifically for heat exchangers based on the Plate&Shell technology that are comprised of a plate pack formed of circular heat exchange plates and a cylindrical shell surrounding it. The plate pack is made up of several plate pairs. Each plate pair is typically formed of two heat exchange plates that are welded together at least at their outer periphery. Each heat exchange plate has at least two openings for the flow of the first heat exchange medium, i.e. the plate pack comprises flow channels formed by the openings of the heat exchange plates. Adjacent plate pairs are attached together by welding or by otherwise combining the openings of two adjacent plate pairs to each other. Thus, the first heat exchange medium can flow from a plate pair to another through the openings in the plates. The second heat exchange medium is arranged to flow inside the shell in the spaces between the plate pairs. Inlet and outlet connections both for the first and the second heat exchange medium are arranged through the outer casing of the Plate & Shell plate heat exchanger. The inlet and outlet connection of the first heat exchange medium are arranged in connection with the inner parts of the plate pair of the plate pack. The primary circuit of the plate heat exchanger is thus formed between the inlet and outlet connection of the first heat exchange medium. The inlet and outlet connection of the second heat exchange medium are arranged in connection with the inside of the shell, that is, the outside of the plate pack. In other words, the secondary circuit of the plate heat exchanger is formed between the inlet and outlet connection of the second heat exchange medium, inside the shell, in the spaces between adjacent plate pairs. The primary and secondary circuits are separate from each other, that is, the first heat exchange medium flowing in the inner part of the plate pack cannot get mixed with the second heat exchange medium flowing in the shell, that is, outside the plate pack. Thus, the first heat exchange medium on the primary side flows in every other plate space and the second heat exchange medium on the secondary side flows in every other plate space of a plate heat exchanger.

The method according to the invention is especially suitable for openable Plate&Shell -heat exchangers. The cover plate of the heat exchanger, which is flanged or bolted, is opened and the plate pack attached to the cover plate construction according to the invention can be withdrawn from the casing.

An additional end plate according to the invention having openings and two large surfaces, a first large surface is arranged in contact with the support plate of the plate pack and a second large surface is arranged in contact with the openable first cover plate of the outer casing so that the additional end plate is attached only at its outer periphery to the support plate of the plate pack. The plate pack is arranged in contact with the additional end plate so that the openings therein are aligned to each other, the support plate of the plate pack and the additional end plate has openings correspond to the openings of the heat exchange plates of the plate pack. According to a preferred embodiment of the invention the inlet and outlet connections having a tube like shape are arranged through the first cover plate of the outer casing and the additional end plate. The inlet and outlet connections for the first heat exchange medium are attached, preferably welded, only to the first cover plate of the outer casing and/or the openings of the additional end plate. Preferably, the inlet and outlet connections for the first heat exchange medium are attached both to the first cover plate of the outer casing and the openings of the additional end plate by welding. The connecting points between the additional end plate and the openings of the support plate of the plate pack are free of the welded joints. The large surfaces of the additional end plate and the support plate of the plate pack are arranged tightly against each other and thus there is no need for the welded joint between the inlet and outlet connections of the first heat exchange medium and the openings of the support plate of the plate pack for achieving the flow channels without any leakage. The inlet and outlet tube connections are not welded to the plate pack construction, i.e. to the heat exchange plates of the plate pack nor to the support plate of the plate pack. The additional end plate has only attached to the support plate of the plate pack at its outer periphery, preferably by welding. The plate pack is fully welded to the additional end plate at its outer periphery, and thus the first and the second heat exchange medium are separated from each other with the welded joints in the heat exchanger construction of the invention.

According to an embodiment of the invention the support plate of the plate pack has a thickness from 5 mm to 70 mm, preferably from 5 mm to 20 mm. The support plates are arranged on the both ends of the plate pack. The additional end plate has a thickness from 5 mm to 30 mm, preferably from 10 mm to 25 mm, and more preferably about 20 mm.

The construction according to the invention does not set limitations to the size of the plate pack. According to an embodiment of the invention the diameter of the heat exchange plates of the plate pack is from 190 to 1400 mm. A diameter of the additional end plate is substantially same as the diameter of the heat exchange plates of the plate pack.

According to an embodiment of the invention the plate pack is detached from the first cover plate construction by grinding between the additional end plate and the support plate of the plate pack. The new plate pack is arranged in connection with the additional plate attached to the openable cover plate. The support plate of the plate pack is attached, preferably welded, to the additional end plate only at its outer periphery, and the heat exchanger is closed by arranging the new plate pack attached to the first cover plate into the outer casing. The cover plate is attached e.g. with bolts to the shell of the outer casing.

Description of the drawings

The invention will be described in more detail with reference to appended drawings, in which

Fig. 1 shows an openable cover plate, a plate pack and an outer shell of the plate heat exchanger according to an embodiment of the invention,

Fig. 2 shows a plate pack, which is fully welded to the openable cover plate according to an embodiment of the invention,

Fig. 2a shows more detailed a construction between the plate pack and the cover plate of the outer casing, and

Fig. 3 shows a cross section view of the openable cover plate with the plate pack according to an embodiment of the invention.

Detailed description of the invention

Figure 1 shows an openable Plate&Shell -type plate heat exchanger construction according to an embodiment of the invention. The plate heat exchanger 1 comprises a plate pack 2 formed of circular heat exchange plates having openings 14 and arranged on top of each other, and which plate pack comprises support plates 3, 5 on the both ends of the plate pack in the direction of the heat exchange plates and an outer surface defined by the outer edges of the heat exchange plates. The support plates 3, 5 of the plate pack having openings are attached in contact with the outermost heat exchange plates of the plate pack. Typically, the heat exchange plates comprise two openings 14, which forms flow channels inside the plate pack.

Flow directors 12, 12' are arranged on the outer surface of the plate pack and they are attached to the support plates 3, 5 of the plate pack. An outer casing surrounding the plate pack 2 comprises a first cover plate 7 and a second cover plate 8 mainly in the direction of the ends of the plate pack and a shell 6 connecting the cover plates 7, 8. The first cover plate 7 is arranged to be openable in the construction of the invention and thus it enables to remove the plate pack out from the shell. The first cover plate 7 is arrangeable against a flange 9 in order that the cover plate 7 can be fastened to the shell of the outer casing in an openable manner.

Inlet and outlet connections 10, 1 1 for a first heat exchange medium are arranged through the openable first cover plate 7 of the outer casing. These connections 10, 1 1 are arranged in connection with the openings 14 of the plate pack. Inlet and outlet connections 13, 15 for a second heat exchange medium are arranged through the shell 6 of the outer casing, which connections are arranged in connection with the inside of the outer casing, i.e. with the outside of the plate pack.

Figure 2 and 2a shows a construction of the openable cover plate of the invention. Same reference numbers are used in all Figures for identifying the corresponding structures. An additional end plate 4 is attached, preferably welded, to the openable cover plate 7 of the outer casing. The inlet and outlet tube connections 10, 1 1 are welded to the openable cover plate 7 of the outer casing and preferably also to the additional end plate 4. The additional end plate 4 is welded at its outer periphery to the openable cover plate 7. A diameter of the additional end plate 4 is substantially same as the diameter of the support plate 3 of the plate pack. The additional end plate 7 is also arranged in contact with the support plate 3 of the plate pack so that the large surfaces of them are tightly attached against each other, and they are attached, preferably welded, to each other only by their outer periphery. There is no welded joint between the inlet and outlet connections 10, 1 1 and the support plate 3 of the plate pack. Figure 2a illustrates a point of the welded joint between the support plate 3 of the plate pack and the additional plate 4. A cross section view of the openable cover plate 7 with the plate pack 2 is illustrated in Figure 3. The openings 14, 14' of the plate pack 2 have been aligned with the openings of the support plate 3, the additional end plate 4 and the cover plate 7 so that the flow channels for the first heat exchange medium are formed from the inlet connection 10 through the plate pack 2 to the outlet connection 1 1 . The inlet and outlet connections 10, 1 1 for the first heat exchange medium have typically a shape of the tube and they are arranged through the openable first cover plate 7 of the outer casing and the additional end plate 4, and so the connections are arranged in connection with the openings 14, 14' of the plate pack 2. The inlet and outlet connections 10, 1 1 are welded to the cover plate of the outer casing and the additional end plate 4. The connecting points between the inlet and outlet connections 10, 1 1 and the support plate 3 of the plate pack are free of the welded joints. The large surfaces of the additional end plate and the support plate 3 of the plate are arranged tightly against each other and so the leak free connection between the connection tubes 10, 1 1 and the plate pack 2 is achieved. In the method according to the invention, an openable cover plate 7 of the outer casing is opened and so the plate pack 2 can be removed from the outer casing. The plate pack 2 tightly attached to the cover plate 7 is detached from the cover plate so that the additional end plate 4 remains in the cover plate 7. After that the new plate pack formed of heat exchange plates having openings (14, 14') and arranged on top of each other and comprises support plates (3, 5) in the direction of the heat exchange plates, is attached to the additional end plate 4, preferably by welding, at its outer periphery. The new plate pack which is now tightly attached to the cover plate 7 is arranged into the outer casing and the heat exchanger construction is closed.

The invention is not intended to be limited to the above-presented exemplary embodiments, but the intention is to apply the invention widely within the inventive idea defined by the claims defined below.