ES2608928T3 - Piston compressor to compress gas - Google Patents

Abstract

Horizontal piston compressor for compressing gas, said compressor comprising: a frame (1), at least one cylinder (2) having a cylinder wall (5), a first cylinder end (3), a second cylinder end ( 4) and a longitudinal axis (6), in which the first end of the cylinder (3) is provided with a passage (7) for the piston rod, in which the cylinder (2) is mounted on the frame (1) ) such that the longitudinal axis (6) of the cylinder (2) extends in a substantially horizontal direction, a piston (10), with reciprocating movement within the cylinder (2), delimiting the piston (10) at least a first compression chamber (11) in the cylinder (2) including the cylinder (2) at least one inlet port (12) to the compression chamber (11) and at least one outlet port (13) from the first chamber of compression (11), a piston rod (30) having a first end (31) and a second end (32), the rod extending go of the piston (30) through the passage (7) for the piston rod of the first end (3) of the cylinder, the piston rod (30) being connected to the piston (10); an actuator assembly (40) for actuating the piston rod (30) and the piston (10) alternatively, the actuator assembly (40) being connected to the second end (32) of the piston rod (30); a gland (50) disposed at the first end (3) of the cylinder, the piston rod (30) extending through the gland (50), the gland (50) comprising one or more packing rings (51) that make contact on the piston rod (30) and provide a seal therewith; a liquid cooling system of the outer surface of the piston rod for cooling the outer surface of the piston rod with a cooling liquid, the cooling system comprising: a cooling unit (60) of the piston rod arranged adjacent to one side of the one or more packing rings (51) that is remote from the first compression chamber (11); a source of coolant (61) to provide a flow of coolant to the cooling unit (60); wherein the cooling unit (60) of the piston rod comprises: an annular member (75) having a cylindrical passage (76) through which the piston rod (30) extends, the diameter of said passage being cylindrical (76) larger than the diameter of the piston rod (30), such that an annular space (77) is present between the piston rod (30) and the annular member (75); a coolant supply channel (80), which extends from an inlet (81) thereof to one or more feed ports (86) in communication with the cylindrical passage (76) to pass the coolant into the annular space ( 77) between the annular member (75) and the piston rod (30), thereby allowing a flow of coolant in contact with the outer surface of the piston rod (30) and through said annular space to extract heat from the outer surface of the piston rod (30); wherein the cooling unit (60) of the piston rod includes axially spaced coolant seals (90) that make contact so that it seals on the piston rod (30), and in which the coolant is introduced in the annular space (77) between said coolant seals (90), wherein the cooling unit (60) of the piston rod further comprises at least one discharge channel (91) of coolant that extends from one or more discharge stations (92) in communication with the cylindrical passage (76) to an outlet for discharging said coolant from the annular space (77) between the piston rod (30) and the annular member (75); characterized in that the cooling unit (60) of the piston rod is provided with one or more respective damping gas seals (105) that delimit an annular damping gas space (104) at each axial end of the annular space (77) in where the coolant is flowed, and in which the cooling unit (60) is provided with one or more buffer gas supply channels (102), which extend from a buffer gas inlet to each of the annular buffer gas spaces (104) to feed a buffer gas thereto, and wherein the cooling system comprises a source (100) of pressurized buffer gas to establish a buffer gas pressure in each of the gas spaces damper (104), each of said buffer gas spaces (104) acting to counteract the entrainment of coolant on the outer surface of the piston rod (30) towards the outside or of the cooling unit (60).

Description

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DESCRIPTION

Piston compressor to compress gas

The invention relates to a piston compressor for compressing gas, in particular a piston compressor in which the cylinder comprising the compression chamber is arranged substantially horizontally.

In piston compressors, the piston rod extends from the compression chamber through a passage of the piston rod at the end of the cylinder. Generally, a packing gland with packing rings is provided to reduce high pressure gas leakage from the compression chamber via the passage of the piston rod at the end of the cylinder. The packing rings have to provide this reduction of the leakage under difficult circumstances: the pressure difference between the compression chamber and the outer environment of the cylinder is generally high and the piston rod makes a movement of pass through the rings of high speed packing.

In order to obtain a good seal, the packing rings must be in contact with the piston rod. In many cases, a force is applied on the packing rings, a force that pushes the packing rings tightly against the piston rod. Such force can, for example, be applied by circular springs or by means of a gas pressure. With such a design, higher pressure differences between the compression chamber and the outside environment can be handled by the packing rings.

The negative aspect of this design is that the more strongly the packing rings are pushed against the piston rod, the more friction takes place between the packing rings and the piston rod. This friction causes the piston rod to become hot and that the piston rod and packing rings suffer increased wear. In piston gas compressors in which the piston rod is arranged substantially horizontally, the problem of friction between the packing rings and the piston rod is even greater than in piston compressors with a vertical piston rod, because the rod of the horizontal piston curves under the influence of gravity. Furthermore, in particular when the piston rings are worn, a slight inclination of the piston rod occurs, which leads to an increase in friction on one side of the piston rod.

It has been proposed to lubricate the piston rod in the vicinity of the packing rings to reduce friction. However, for many applications this does not provide an acceptable solution because some of the lubricant will adhere to the piston rod. The piston rod will then introduce lubricant into the compression chamber. This is not always acceptable, for example when the compressor is used to compress a dry gas and / or in cases where a non-lubricated piston compressor is applied, such as in a floating piston compressor of the type described in the document of European patent EP0839280.

U.S. Patent Document US 3,194,568 discloses the cooling of a piston rod inside the stuffing box. The stuffing box comprises a channel that brings water to an annular space in the stuffing box that is present around the piston rod. Seals are provided at both axial ends of this annular space to keep the water majority in the annular space. Some water will adhere to the piston rod and drain through the seals. According to the disclosure of the US patent document. US 3,194,568, this water will evaporate due to the high temperature of the piston rod and then disappear through vent holes provided in the stuffing box.

Practice has shown that the cooling capacity of such a design is limited and that it can only be used in combination with a limited number of types of coolant.

Austrian patent document AT507564A4 discloses a seal arrangement in accordance with the principle of a sealant barrier that provides sealing elements 8, 9 arranged in a radial direction at a distance from the radial end of the recess 10 receiving the sealing elements 8, 9.

The invention aims to provide a piston compressor with a cooling system of the outer surface of the piston rod.

According to a first aspect of the invention, a horizontal piston compressor for compressing gas is provided, said compressor comprising:

a rack,

at least one cylinder having a cylinder wall, a first cylinder end, a second cylinder end and a longitudinal axis, in which the first end of the cylinder is provided with a passage for the piston rod,

in which the cylinder is mounted on the frame such that the longitudinal axis of the cylinder extends in a substantially horizontal direction,

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a piston with reciprocating movement inside the cylinder, delimiting the piston at least a first compression chamber in the cylinder, including the cylinder at least one inlet port to the first chamber of

compression and with at least one exit port from the first compression chamber,

a piston rod having a first end and a second end, the piston rod extending through the passage for the piston rod of the first end of the cylinder, the piston rod being connected to the piston,

an actuator assembly for actuating the piston rod and the piston alternately, the actuator assembly connected to the second end of the piston rod,

a gland provided at the first end of the cylinder, the piston rod extending through the gland, the gland comprising one or more packing rings that make contact on the piston rod to provide a seal therewith,

a liquid cooling system of the outer surface of the piston rod to cool the outer surface of the piston rod with a cooling liquid comprising the cooling system:

a piston rod cooling unit disposed adjacent to one side of the one or more rings of

packing that is far from the first compression chamber;

a source of coolant to provide a flow of coolant to the cooling unit; wherein the piston rod cooling unit comprises:

an annular member having a cylindrical passage through which the piston rod extends, the diameter of said cylindrical passage being larger than the diameter of the piston rod, such that an annular space is present between the piston rod and the annular member,

a cooling liquid feed channel, which extends from an inlet thereof to one or more feeding ports in communication with the cylindrical passage to pass the cooling liquid to the annular space between the annular member and the piston rod, allowing in this way a flow of cooling liquid in contact with the outer surface of the piston rod and through said annular space to extract heat from the outer surface of the piston rod.

wherein the piston rod cooling unit includes axially spaced coolant seals that make contact so that it seals on the piston rod and in which coolant is introduced into the annular space between said coolant seals ;

in which the cooling unit of the piston rod further comprises at least one refrigerant liquid discharge channel, which extends from one or more discharge ports in communication with the cylindrical passage to an outlet to discharge said refrigerant liquid from the annular space between the piston rod and the annular member;

the piston rod cooling unit is provided with one or more respective buffer gas seals that delimit an annular buffer gas space at each axial end of the space in which the cooling liquid is flowed; Y

wherein the cooling unit is provided with one or more buffer gas supply channels which extend from a buffer gas inlet to each of the annular buffer gas spaces to feed buffer gas thereto; and wherein the cooling system comprises, a source of pressurized buffer gas to establish a buffer gas pressure in each of the buffer gas spaces, each buffer gas space acting to counteract the entrainment of cooling liquid on the external surface from the piston rod to the outside of the cooling unit.

According to a second aspect of the invention, a cooling system of the outer surface of the piston rod is provided for cooling the outer surface of the piston rod of a piston compressor with a cooling liquid, the system comprising:

a piston rod cooling unit, which is arranged adjacent to the side of the one or more packing rings away from the first compression chamber of the compressor,

a source of coolant that is adapted to provide a flow of coolant to the cooling unit;

wherein the cooling unit comprises: an envelope;

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an annular member having a cylindrical passage through which, in use, a piston rod of the compressor extends, the diameter of said cylindrical passage being larger than the diameter of the piston rod, such that an annular space is present between the piston rod and the annular member,

a cooling liquid feed channel, which extends from an inlet thereof to one or more feeding ports in communication with the cylindrical passage to pass the cooling liquid to the annular space between the annular member and the piston rod, allowing this way establishing a flow of cooling liquid in contact with the outer surface of the piston rod and through said annular space causing heat extraction from the outer surface of the piston rod;

wherein the cooling unit is provided with axially spaced coolant seals that make contact so that it seals on the piston rod and in which said coolant is introduced into the annular space between said coolant seals;

and wherein the cooling unit further comprises at least one refrigerant liquid discharge channel, which extends from one or more discharge ports in communication with the cylindrical passage to an outlet to discharge said refrigerant liquid from space annular between the piston rod and the annular member; Y

wherein the cooling unit is provided, near one or each of the refrigerant liquid seals, of one or more respective buffer gas seals that delimit an annular buffer gas space at each axial end of the annular space in the that the coolant is flowing ;; Y,

wherein the cooling unit is provided with one or more buffer gas supply channels which extend from a buffer gas inlet to each of the annular buffer gas spaces to feed buffer gas thereto; and in which the cooling system comprises, a source of pressurized buffer gas that is adapted to establish a buffer gas pressure in each of the buffer gas spaces, and each buffer gas space acting to counteract the entrainment of cooling liquid on the outer surface of the piston rod towards the outside of the cooling unit.

The invention will be explained in more detail with reference to the drawings, in which non-limiting embodiments of the invention are shown. The drawings show in:

Figure 1: a horizontal piston compressor,

Figure 2: an embodiment of a cooling unit according to the invention,

Figure 3: second embodiment of a cooling unit according to the invention,

Figure 4: an embodiment of a cooling system according to the invention,

Figure 5: different ways of mounting the cooling unit on the piston rod.

Figure 1 shows a side view of a horizontal piston compressor. The compressor comprises a frame 1, in or to which other parts of the compressor are mounted.

The compressor comprises a cylinder 2. The cylinder 2 has a first end 3 of the cylinder and a second end 4 of the cylinder. The first end 3 of the cylinder and the second end 4 of the cylinder are each arranged at an axial end of the cylinder 2. The first end 3 of the cylinder comprises a passage 7 of the piston rod.

The cylinder 2 also has a wall 5 of the cylinder and a longitudinal axis 6.

In the cylinder 2, a piston 10 is mounted. The piston 10 has alternative movement in the cylinder 2, which means that it can move forward and backward within the cylinder 2 along the longitudinal axis 6 of the cylinder 2.

In traditional piston compressors, the piston is lubricated by a lubricating liquid (eg oil) in such a way that metal-to-metal contact between the piston and the cylinder wall is prevented. In a more modern design, no lubrication oil is necessary between the piston and the cylinder wall. Such piston compressors, in which there is no lubrication between the piston and the cylinder wall is referred to as non-lubricated compressors. Such compressors, however, may comprise parts, for example grna rings that extend around the piston, which contain a solid lubricant such as molybdenum disulphide. A special class of non-lubricated compressors are called "floating piston compressors." In such compressors, a gas film is present between the piston and the cylinder wall to prevent metal-to-metal contact between the piston and the cylinder wall. Examples of a floating piston compressor are described in European patent document EP0839280.

At least one compression chamber is present in cylinder 2. Each compression chamber is delimited at one axial end by the piston and at the opposite axial end by one end of the cylinder. In the embodiment of Figure 1, the piston compressor comprises two compression chambers 11,21.

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Each compression chamber has an inlet port 12, 22 and an outlet port 13, 23. In each inlet port 12, 22 of the compression chamber there is an inlet valve 14, 24. In each outlet port 13 , 23 of the compression chamber an outlet valve 15, 25 is arranged. The valves 14, 24, 15, 25 are controlled such that when the inlet valve 14, 24 of a compression chamber 11, 21 is open , the outlet valve 15, 25 of that same compression chamber is closed and when the outlet valve 15, 25 of a compression chamber 11, 21 is open, the inlet valve 14, 24 of that same compression chamber is closed.

The piston 10 is mounted on the piston rod 30. The piston rod has a first end 31 and a second end 32. In the embodiment shown in Figure 1, the piston 10 is connected to the first end 31 of the piston rod 30 In an alternative embodiment (not shown), the piston rod may extend beyond the piston 10 in the pressure chamber 11 and through the passage at the second end 4 of the cylinder.

In the embodiment of Figure 1, the piston rod 30 extends through a spacer piece 35 in the frame 1 to the drive assembly 40. In this embodiment, the second end 32 of the piston rod 30 is connected to the crosshead 41. In use, the crosshead moves alternately within the spacer part 35 of the frame 1.

The crosshead 41 is operated by the connecting rod 42. The connecting rod 42 has a first end 43 and a second end 44. The first end 43 of the connecting rod 42 is connected to the crosshead 41, while the second end 44 of connecting rod 42 is connected to crankshaft 45. In use, crankshaft 45 rotates. The connecting rod 42 transforms this rotation into a translation and, thereby, drives the alternative movement of the crosshead 41.

Where the piston rod 30 leaves the cylinder 2 via the passage of the piston rod 7 of the cylinder cover 3, a good seal is important to prevent the escape of gas from the pressure chamber 21 via the passage of the piston rod piston 7. This seal is provided by the gland 50, which is shown only schematically in Figure 1. The piston rod 30 extends through the gland 50.

In packing gland 50, packing rings 51 are present for the actual sealing. The packing rings 51 reduce or even prevent gas leakage from the compression chamber 21 on the surface of the piston rod. For effective sealing, the packing rings 51 have to fit tightly around the piston rod 30. This causes friction between the packing rings 51 and the piston rod 30 and, thereby, the heating of the piston rod.

In the embodiment shown in Figure 1, two sets of multiple packing rings are present in the stuffing box. As the skilled person will understand, any other number of packing rings is possible.

In the embodiment of Figure 1, the piston rod 30 extends through only one of the ends of the cylinder. In an alterative embodiment, in which the piston rod extends through both ends of the cylinder, two cable glands are present, each to seal a passage of the piston rod.

The horizontal piston compressor of Figure 1 is provided with a cooling system of the outer surface of the piston rod to cool the surface of the piston rod. The cooling system of the outer surface of the piston rod comprises a cooling unit 60 of the piston rod. In the embodiment shown in Figure 1, the cooling unit 60 is disposed outside the packing gland 50 which contains the packing rings and is not connected to the packing gland 50. In alternative embodiments (not shown), the cooling unit may be connected to the outside the stuffing box or arranged inside the stuffing box.

The cooling unit 60 of the piston rod is preferably disposed adjacent to the packing ring or packing rings, because it is there where the piston rod is heated, due to friction between the packing rings and the piston rod .

The cooling system of the external surface of the piston rod further comprises a source of coolant 61. The source of coolant 61 is connected to the cooling unit 60 of the piston rod by means of at least one pipe 62 coolant This first coolant circulation tube 62 carries coolant from the source of coolant 61 to the cooling unit 60 of the piston rod. Preferably, a second coolant liquid circulation tube 63 is also present, which carries coolant from the cooling unit 60 of the piston rod back to the source of coolant 61.

Figure 2 shows an embodiment of a cooling unit 60 of the piston rod according to the invention. The piston rod 30 extends through the cooling unit 60 of the piston rod, so that the cooling unit can act directly on the surface of the piston rod 30. It is very common to make the stainless steel piston rods. . Stainless steel is not such a good heat conductor, so a significant portion of the heat that is created on the surface of the piston rod remains present on the surface of the piston rod instead of dissipating into the core of the piston rod.

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The piston rod 30 moves alternately through the cooling unit 60 of the piston rod according to arrow 33.

The cooling unit 60 of the piston rod comprises an envelope 70, which in the embodiment of Figure 2 is constituted by a first wrap ring 71 and a second wrap ring 72. Use two or more wrap rings that together form the shell 70 It allows an easy assembly of the cooling unit on the piston rod. Within the envelope 70, an annular member 75 is present. For easy assembly, the annular member 75 and the surround rings 71, 72 are constituted by two or more ring segments. The wrapping rings 71, 72 are mounted in such a way that they cannot move with respect to each other.

In the embodiment shown in Figure 2, the outer diameter of the annular member is smaller than the inner diameter of the wrapping rings 71, 72 where the wrapping rings 71, 72 extend over the annular member 75. This creates a circular crown 73 between the outer diameter of the annular member 75 and the inner diameter of the wrapping rings 71, 72 in the part where they extend over the annular member 75. This circular crown 73 makes possible the relative movement in radial directions of the annular member 75 with respect to the tubular shell 70.

The annular member 75 comprises a cylindrical passage 76. When the cooling unit 60 of the piston rod is mounted on the piston rod of a piston compressor, the piston rod 30 extends through this cylindrical passage 76.

The diameter of the cylindrical passage 76 is larger than the external diameter of the piston rod 30, or at least greater than the external diameter of the part of the piston rod 30 that moves alternately through the cooling unit 60 of the rod of the piston The difference between the diameter of the cylindrical passage and the diameter of the piston rod means that an annular space 77 is present between the annular member 75 and the piston rod 30. If the piston rod 30 is perfectly centered on the cylindrical passage 77, the distance 78 between the piston rod 30 and the surface of the cylindrical passage 76 is the same over the entire circumference of the cylindrical passage.

The diameter of the cylindrical passage may vary over the length of the cylindrical passage, for example in the form of a stepped variation, but the diameter may also be constant over the length of the cylindrical passage.

In a possible embodiment, the difference between the diameter of the cylindrical passage 76 and the diameter of the piston rod 30 is between 0.1 mm and 0.6 mm in the portion of the cylindrical passage 76 having the smallest diameter. In an alternative embodiment, the difference between the diameter of the cylindrical passage 76 and the diameter of the piston rod 30 is between 0.2 mm and 0.4 mm in the portion of the cylindrical passage 76 having the smallest diameter. In yet another alternative embodiment, the difference between the diameter of the cylindrical passage 76 and the diameter of the piston rod 30 is about 0.3 mm in the portion of the cylindrical passage 76 having the smallest diameter.

The cooling unit 60 of the piston rod further comprises a channel 80 for supplying cooling liquid. This coolant supply channel has an inlet 81, which receives coolant from the source of coolant via the coolant circulating pipe 62.

Channel 82 allows the coolant to flow through the surround ring 71. From the channel 82, the coolant enters the coolant liquid feed space 83, between the surround ring 71 and the annular member 75. The space 83 Coolant feed is part of the circular crown 73 between the annular member 75 and the wrapping rings 71, 72. In use, the circular crown may be empty or filled with coolant, or partially filled with coolant, completely or partially filled of a buffer gas or any other type of gas, or it can accommodate elastic members and / or seals.

The coolant liquid feed space 83 is sealed at its two axial ends by seals 84. The seals 84 cause the coolant to flow from the coolant liquid feed space 83 to the channel 85 of the annular member 75 and does not escape before having reached the annular space 77 between the annular member 75 and the piston rod 30.

The channel 85 in the annular member 75 allows the refrigerant liquid to flow from the refrigerant liquid feed space 83 to the feed port 86, which is in fluid communication with the cylindrical passage 76 of the annular member 75. From the port of feed 86, the coolant enters the annular space 77 between the annular member 75 and the piston rod 30. The feed port 86 preferably has a diameter smaller than the channel 85 such that it forms a hole. This creates a better flow profile in the flow of the cooling liquid.

In the annular space 77, the coolant is in direct contact with the outer surface of the piston rod, so that it can cool the surface of the piston rod 30.

It is possible that the annular member 75 is provided with more than one channel 85 with a feed port 86. This provides a better distribution of cooling liquid from the cavity 83 to the annular space 77 between the annular member and the piston rod. As an alternative, there is a single channel 85 with power port 86.

From the feed port 86, the coolant flows through the annular space 77 to the chambers of

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87 refrigerant liquid collection. The flow of refrigerant liquid through the annular space 77 cools the outer surface of the piston rod 30.

In the embodiment of Figure 2, two collection chambers 87 of cooling liquid are provided. It is also possible, however, that only a single collection chamber 87 is present.

In the embodiment of Figure 2, the cooling unit 60 of the piston rod further comprises two coolant liquid seals 90. These can be of any type are suitable seals; in figure 2 scraper rings are applied. These have the additional benefit of - apart from sealing - scratching coolant from the surface of the alternative piston rod.

The coolant seals 90 delimit the annular space between the annular member 75 and the piston rod 30 in the axial direction. The collection chambers 87 of cooling liquid are widened portions of this annular space, formed by parts of the cylindrical passage having a diameter larger than the central portion of the cylindrical passage. The central portion of the cylindrical passage has the smallest diameter and thereby forms the part of the annular space 77 that has the smallest distance 78 between the annular member 75 and the piston rod 30.

From the coolant collection chamber 87, the coolant is discharged. For download, multiple download channels 91 are provided in this example. Alternatively, a single download channel may be present.

The coolant enters the discharge channel via a discharge port 92. This discharge port 92 is in fluid communication with the cylindrical passage 76 and thereby with the annular space 77 between the annular member 75 and the rod of the piston 30

From the discharge port 92, the refrigerant liquid enters the channel 93 in the annular member 75 and, from there, in the discharge space 94 of the refrigerant liquid, which is part of the circular crown 73 between the annular member 75 and the envelope 70. Seals 99 seal the outer axial ends of the discharge spaces 94 of cooling liquid. The internal axial ends of the refrigerant liquid discharge spaces 94 are sealed by the seals 84. The seals 84 prevent the flow of refrigerant liquid from the refrigerant liquid feed space 83 to a discharge space 94 of the refrigerant liquid. Seals 99 prevent the escape of cooling liquid from the discharge spaces 94 of cooling liquid towards their respective external axial ends.

The seals 99 and 84 are arranged in grooves 88 of the wrapping rings 71, 72. The grooves 88 are sized such that the seals 99.84 can move relative to the wrapping ring 71, 72, thereby allowing relative movement of the annular member with respect to the envelope 70.

The refrigerant liquid in the refrigerant liquid feed space 83 and the refrigerant liquid discharge spaces 94 acts as a combination of a spring and a damper for the relative movement of the annular member 75 and the envelope 70.

The coolant seals are arranged in grooves 97 in the annular member 75. The grooves 97 have a radial dimension larger than the outer diameter of the coolant seal 90, so that in the radial direction there is space between the outer diameter of the seal of liquid refrigerant and the wall of the respective groove 97.

The slots 97 are in fluid communication with the coolant discharge channel via conduit 98. If some coolant drains beyond seal 90 to slot 97, it flows out of slot 97 again through via the conduit 98. The conduits 98 thereby prevent the accumulation of coolant in the slots 97.

In the embodiment of Figure 2, the cooling unit 60 is also provided with a buffer gas system.

The buffer gas system comprises a source 100 of buffer gas for the supply of pressurized buffer gas. The source 100 of the damping gas supply supplies a pressurized damping gas, via the dampening gas supply lines 101, to the damping gas supply channels 102. Each of the wrapping rings 71, 72 has been provided with a channel 102 for supplying the buffer gas.

The buffer gas may be an inert gas, such as nitrogen. The buffer gas may be the same type of gas as the gas that is compressed by the compressor piston. The source of the buffer gas may receive the gas that will function as the buffer gas from the same source from which the compressor receives the gas to be compressed. The source of buffer gas could also be an independent container containing a pressurized gas.

The wrapping rings 71, 72 have a part with a large internal diameter. This part extends over the annular member 75.The wrap rings 71, 72 also have a part with a smaller internal diameter. This part is located next to an axial end of the annular member 75.

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When a buffer gas system is present, preferably there is some distance between the axial ends of the annular member and the adjacent wrapping rings, such that a gap 103 is present between the axial end of the annular member and the adjacent wrapping ring. The buffer gas can enter this space from the buffer gas supply channel 102. From this space 103, the buffer gas can reach the annular buffer gas space 104. Alternatively, the buffer gas channel 102 may be extended such that it feeds the buffer gas directly into the associated buffer gas space 104.

The damping gas spaces 104 are delimited at an axial end by means of a damping gas seal 105 and at the opposite axial end by a coolant liquid seal 90.

The gas in the buffer gas spaces is kept under pressure by the source 100 of the buffer gas. The pressure of the buffer gas in the spaces 104 of the buffer gas acts to counteract the entrainment of liquid refrigerant on the outer surface of the piston rod towards the outside of the cooling unit.

Maintaining the pressure of the buffer gas above the pressure of the coolant in the collection chambers 87 reduces or even prevents the leakage of coolant over the coolant seals 90 of the cooling unit.

In an advantageous embodiment, as shown in Figure 2, the buffer gas can also enter the space 106 between the outer diameter of the annular member 75 and the inner diameter of the wrap ring 71, 72. In this way, the pressure of the buffer gas also acts on the seals 99, helping to reduce or even prevent the leakage of refrigerant liquid on these seals.

Figure 3 shows a second embodiment of a cooling unit according to the invention.

In the cooling unit 200 of Figure 3, an annular member 205 is present. The annular member has a cylindrical passage 206, which cylindrical passage has a diameter that is larger than the diameter of the piston rod 30, or at least larger than the outer diameter of the part of the piston rod 30 that moves alternately through the cooling unit 200 of the piston rod. The piston rod 30 extends through the cylindrical passage 206 of the annular member 205. In use, an annular space 207 is present between the surface of the cylindrical passage 206 of the annular member 205 and the outer surface of the piston rod 30.

The annular member 205 is disposed in an envelope, which envelope comprises an enveloping ring 210. In the embodiment shown in Figure 3, the outer diameter of the annular member 205 is smaller than the inner diameter of the wrapping ring 210 where the wrapping ring 210 extends over the annular member 205. This creates a circular crown 215 between the outer diameter of the annular member 205 and the internal diameter of the envelope ring 210 in the part where it extends over the annular member 205. This circular crown 215 makes possible the relative movement in radial directions of the annular member 205 with respect to the surround ring 210.

In a possible embodiment, the difference between the diameter of the cylindrical passage 206 and the diameter of the piston rod 30 is between 0.1 mm and 0.6 mm. In an alternative embodiment, the difference between the diameter of the cylindrical passage 206 and the diameter of the piston rod 30 is between 0.2 mm and 0.4 mm. In yet another alternative embodiment, the difference between the diameter of the cylindrical passage 206 and the diameter of the piston rod 30 is about 0.3 mm.

The cooling unit 200 of the piston rod further comprises a coolant liquid feed channel 220. This coolant feed channel has an inlet 221, which receives coolant from the source of coolant via a coolant circulating pipe 62.

Channel 222 allows the coolant to flow through the surround ring 210. From the channel 222, the coolant enters a coolant liquid feed space 223, between the shell ring 210 and the annular member 205. The space 223 of Coolant feed is part of the circular crown 215 between the annular member 205 and the surround ring 210. In use, the circular crown may be empty, or filled with coolant, or partially filled with coolant, completely or partially filled with a buffer gas or any other type of gas, or it can accommodate elastic members and / or seals.

The coolant liquid feed space 223 is sealed at its two axial ends by seals 224. The seals 224 cause the coolant to flow from the coolant liquid feed space 223 to the channel 225 of the annular member 205 and does not escape before having reached the annular space 207 between the annular member 205 and the piston rod 30.

The channel 225 of the annular member 205 allows the refrigerant liquid to flow from the refrigerant liquid feed space 223 to a feed port 226 which is in fluid communication with the cylindrical passage 206 of the annular member 205. From the feed port 226, the coolant enters the annular space 207 between the annular member 205 and the piston rod 30. The feed port 226 preferably has a diameter smaller than the channel 225 such that it forms a hole. This creates a better flow profile in the flow of the cooling liquid.

In the annular space 207, the coolant is in direct contact with the outer surface of the rod of the

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piston, so that it can cool the surface of the piston rod 30.

It is possible that the annular member 205 is provided with more than one channel 225 with a feeding port 226. This provides a better distribution of cooling liquid from the cavity 223 to the annular space 207 between the annular member and the piston rod. As an alternative, there is a single channel 225 with power port 226.

From the supply port 226, the coolant flows through the annular space 207 to the collection chambers 227 of primary coolant. The flow of liquid refrigerant through the annular space 207 cools the outer surface of the piston rod 30.

The primary cooling liquid collection chambers 227 are arranged at both axial ends of the annular space 207 between the piston rod 30 and the annular member 205. They receive coolant from the annular space 207. Instead of two collection chambers 227 of primary coolant, it is possible to have a single collection chamber 227 of primary coolant. In that case, it is advantageous to arrange the feeding port 226 at one axial end of the annular space 207 and the collection chamber 227 of primary coolant at the other axial end of the annular space 207.

Each of the collection chambers 227 of primary coolant is formed in a discharge ring 240. Each of the discharge rings 240 is disposed at an axial end of the envelope ring 210. Each of the discharge rings 240 is provided of a cylindrical passage 241. The diameter of the cylindrical passage 241 of each discharge ring is preferably larger than the diameter of the cylindrical passage 206 of the annular member 205.

From the collection chambers 227 of primary coolant, the coolant is discharged. For discharge, one or more discharge channels 242 are provided on each discharge ring 240. Each of the discharge rings has a discharge port 243 and an outlet 244. The cooling liquid flowing out of the discharge channels 242 is collected in one or more secondary 245 coolant collection chambers.

In the embodiment of Figure 3, two secondary coolant collection chambers 245 are present, each associated with a discharge ring 240. In the example of Figure 3, the secondary coolant liquid collection chambers 245 are extends over the circumference of the discharge rings 240 and are formed by a ring 246 having a recess 247 in it. The recess 247 preferably extends around the entire internal circumference of the ring 246.

Preferably, the coolant that is collected in a secondary coolant collection chamber 245 flows from that secondary coolant collection chamber 245 back to the source of coolant via a liquid circulation tube 63.

At the axial end opposite the axial end facing the annular member 205, each of the primary coolant collection chambers 227 is delimited by a coolant liquid seal 230. The refrigerant liquid seals 230 may be any suitable type of seals; in figure 3, scraper rings are applied. These have the additional benefit of - apart from sealing - scratching coolant from the surface of the alternative piston rod.

Each of the coolant seals 230 is arranged in a groove 231 in the discharge ring 240. Both grooves 231 have a radial dimension larger than the outside diameter of the coolant seal 230, so that in the radial direction there is a space between the external diameter of the refrigerant liquid seal 230 and the wall of the respective slot 231 in which it is arranged.

The slots 231 are in fluid communication with the secondary coolant collection chamber 245 via conduit 233. If some coolant drains beyond seal 230 to slot 231, it flows out of slot 231 of again via the conduit 233. The conduits 233 thereby prevent the accumulation of coolant in the slots 231.

In the embodiment of Fig. 3, two safety rings 270 are also present. Each of the safety rings 270 is disposed adjacent to a discharge ring 240, on the side opposite the side facing the annular member. 205. The safety ring 270 has a cylindrical passage 272 which is preferably smaller than the outside diameter of the refrigerant liquid seal 230, so that it can provide axial support for the refrigerant liquid seal ring 230. The piston rod 30 extends through this cylindrical passage 272.

The safety rings are provided with one or more channels 271, which are in fluid communication with a collection chamber 245 of secondary coolant. In this way, some coolant that flows beyond the seals 230 via the surface of the piston rod 30, can flow to the collection chamber 245 of secondary coolant and from there back to the source of coolant via the pipeline 63 of the circulation of liquid refrigerant.

In the embodiment of Figure 3, the cooling unit 200 is also provided with a buffer gas system.

The buffer gas system comprises a source 250 of buffer gas for the gas supply

5

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fifteen

twenty

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30

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pressurized damper. The damping gas supply source 250 supplies a pressurized damping gas via the damping gas supply lines 251 to the damping gas supply channels 252. In the embodiment of Fig. 3, separate rings 255 of buffer gas have been provided. Each of the damping gas rings 255 is provided with one or more channels 252 of damping gas.

The buffer gas may be an inert gas, such as nitrogen. The buffer gas may be the same type of gas as the gas that is compressed by the piston compressor. The source of the buffer gas may receive the gas that will function as the buffer gas from the same source from which the compressor receives the gas to be compressed. The source of buffer gas could also be an independent container containing a pressurized gas.

Each of the rings 255 of buffer gas has been provided with a cylindrical passage 256, such that a space 260 of buffer gas is created. The damping gas spaces 260 are delimited at both axial ends by a seal 261a, b of damping gas. The damping gas seals 261a at the inner axial end of a damping gas space 260 presses against a surface of a safety ring 270, while the seals 261b at the outer axial end of a damping gas space 260 press against the surface of an end ring 275.

The gas in the buffer gas spaces is kept under pressure by the source 250 of buffer gas. The pressure of the buffer gas in the buffer spaces 260 acts to counteract the drag of coolant onto the outer surface of the piston rod to the outside of the cooling unit.

Maintaining the pressure of the buffer gas above the pressure of the coolant in the primary coolant collection chambers 227 reduces or even prevents the leakage of coolant over the coolant seals 230 of the cooling unit.

In the embodiment of Figure 3, the discharge rings 240, the safety rings 270, the gas rings 255 and the end rings 275 are all independent rings. However, it is possible to combine two or three adjacent rings into a single ring. For example, a discharge ring and a safety ring, or a safety ring, a buffer gas ring and an end ring can be combined into a single ring.

In a possible embodiment, the rings of a cooling unit such as that shown in Figure 2 or Figure 3 are held together in the axial direction by holding them between two flanges, arranging them in an envelope of the cooling unit or in the envelope of the stuffing box, or holding them between a flange and the packing of the stuffing box.

Figure 4 shows an embodiment of a cooling system of the outer surface of the piston rod according to the invention.

The system of Figure 4 comprises a cooling unit 60, which is mounted on the piston compressor such that the piston rod 30 extends through the cooling unit 60. The cooling unit may be the embodiment as shown in figure 2 or any other embodiment according to the invention. In the example of Figure 4, the cooling unit is mounted outside the stuffing box.

The cooling system of the outer surface of the piston rod of Fig. 4 further comprises a source of coolant 61 in the form of a reservoir containing coolant. A first coolant circulation pipe 67 connects the coolant source to a pump 65. The pump 65 provides the flow of coolant through the cooling system.

A second circulating pipe 62 of cooling liquid carries the cooling liquid to the cooling unit. A third circulating pipe 63 of coolant receives the coolant from the cooling unit 60 again. The coolant has now been heated by the piston rod.

The third circulating pipe 63 of the coolant carries the heated coolant to the heat exchanger 66, where the coolant is cooled again. The heat exchanger can be any suitable kind of heat exchanger, for example a cross flow heat exchanger, a heat exchanger with atmospheric air as a cooling medium.

A fourth circulation tube 68 of cooling liquid carries the cooled cooling liquid back to the source of cooling liquid 61, the reservoir, again.

Preferably, the source 61 of the cooling liquid, the pump 65 and the heat exchanger 66 are mounted in a housing 64 together.

Figure 5 shows different ways of mounting the cooling unit 60 on the piston rod 30.

In Figure 5A, the envelope of the cooling unit 60 is provided with a flange 69. By means of this flange 69, the cooling unit is fixed to the gland 50 using bolts.

In Figure 5B, the cooling unit is not fixed to the gland 50, but to the frame 1. The connection with the

frame 1 causes the cooling unit 60 to remain in place regardless of the action of the piston rod 30. Optionally, hinges 79 are provided in the connection between the cooling unit 60 and the frame 1. In this way, the The cooling unit can cope with the inclinations of the piston rod with respect to the frame, as for example, occurs due to the bending of the piston rod.

Figure 5C shows a gland 50 that is enlarged, so the cooling unit 60 can be placed inside the gland 50.

Claims (9)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1.- Horizontal piston compressor for compressing gas, said compressor comprising: a frame (1), at least one cylinder (2) having a cylinder wall (5), a first cylinder end (3), a second cylinder end (4) and a longitudinal axis (6), in which the first end of the cylinder (3) is provided with a passage (7) for the piston rod, wherein the cylinder (2) is mounted on the frame (1) such that the longitudinal axis (6) of the cylinder (2) extends in a substantially horizontal direction, a piston (10), with reciprocating movement inside the cylinder (2), delimiting the piston (10) at least a first compression chamber (11) in the cylinder (2) including the cylinder (2) at least one inlet port (12) to the compression chamber (11) and at least one outlet port (13) from the first compression chamber (11), a piston rod (30) having a first end (31) and a second end (32), the piston rod (30) extending through the passage (7) for the piston rod of the first end (3) of the cylinder, the piston rod (30) being connected to the piston (10); an actuator assembly (40) for actuating the piston rod (30) and the piston (10) alternatively, the actuator assembly (40) being connected to the second end (32) of the piston rod (30); a gland (50) disposed at the first end (3) of the cylinder, the piston rod (30) extending through the gland (50), the gland (50) comprising one or more packing rings (51) that make contact on the piston rod (30) and provide a seal therewith; a liquid cooling system of the outer surface of the piston rod to cool the outer surface of the piston rod with a cooling liquid, the cooling system comprising: a cooling unit (60) of the piston rod disposed adjacent to one side of the one or more packing rings (51) that is remote from the first compression chamber (11); a source of cooling liquid (61) to provide a flow of cooling liquid to the cooling unit (60); wherein the cooling unit (60) of the piston rod comprises: an annular member (75) having a cylindrical passage (76) through which the piston rod (30) extends, the diameter of said cylindrical passage (76) being greater than the diameter of the piston rod (30), such that an annular space (77) is present between the piston rod (30) and the annular member (75); a feed channel (80) of cooling liquid, which extends from an inlet (81) thereof to one or more feeding ports (86) in communication with the cylindrical passage (76) to pass the cooling liquid to the annular space ( 77) between the annular member (75) and the piston rod (30), thereby allowing a flow of cooling liquid in contact with the outer surface of the piston rod (30) and through said annular space to extract heat from the outer surface of the piston rod (30); wherein the cooling unit (60) of the piston rod includes axially spaced coolant seals (90) that make contact so that it seals on the piston rod (30), and in which the coolant is introduced in the annular space (77) between said coolant seals (90), wherein the cooling unit (60) of the piston rod further comprises at least one discharge channel (91) of cooling liquid extending from one or more discharge stations (92) in communication with the cylindrical passage ( 76) to an outlet for discharging said coolant from the annular space (77) between the piston rod (30) and the annular member (75); characterized by that The cooling unit (60) of the piston rod is provided with one or more respective damping gas seals (105) that delimit an annular damping gas space (104) at each axial end of the annular space (77) where it is made flow the coolant, and 5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 wherein the cooling unit (60) is provided with one or more buffer gas supply channels (102), which extend from a buffer gas inlet to each of the annular buffer gas spaces (104) for supplying a buffer gas thereto, and wherein the cooling system comprises a source (100) of pressurized buffer gas to establish a pressure of buffer gas in each of the spaces of buffer gas (104), each of which acts said gas buffer spaces (104) for counteracting the drag of liquid refrigerant on the outer surface of the piston rod (30) towards the outside of the cooling unit (60). 2. - The piston compressor of claim 1, wherein the compressor has a floating piston. 3. - The piston compressor of claim 1, wherein the compressor has a non-lubricated piston 4. - The piston compressor of claim 1, wherein the one or more damping gas seals (105) are provided near each refrigerant liquid seal (90). 5. - The piston compressor of claim 4, wherein the one or more buffer gas seals (105) prevent the leakage of coolant over the coolant seals (90). 6. - The piston compressor of claim 1, wherein the source of buffer gas is maintained at a pressure above the pressure of the coolant in the cooling unit (60). 7. - The piston compressor of claim 1, wherein the buffer gas space (104) is formed between an end ring (275) and a safety ring (270) of the cooling unit (60). 8. - The piston compressor of claim 1, wherein the space (104) of damping gas is delimited at both axial ends by respective damping gas seals (105). 9. - A cooling system of the external surface of the piston rod for cooling an external surface of the piston rod of a piston compressor with a cooling liquid, the system comprising: a cooling unit (60) of the piston rod, which is arranged adjacent to the side of one or more packing rings (51) away from a first compression chamber (11) of the compressor; a source (61) of coolant that is adapted to provide a flow of coolant to the cooling unit (60); wherein the cooling unit (60) comprises: an envelope (64), an annular member (75;) having a cylindrical passage (76) through which, in use, a piston rod (30) of the compressor extends, the diameter of said cylindrical passage (76) being greater than the diameter of the piston rod (30), such that an annular space (77) is present between the piston rod (30) and the annular member (75); a feed channel (80) of cooling liquid, which extends from an inlet thereof to one or more feeding ports in communication with the cylindrical passage to pass the cooling liquid into the annular space between the annular member (75) and the piston rod (30), thus allowing to establish a flow of cooling liquid in contact with the outer surface of the piston rod and through said annular space (77) causing heat extraction from the outer surface of the piston rod ( 30); wherein the cooling unit (60) is provided with axially spaced coolant seals (90) that make contact so that it seals on the piston rod (30), and in which said coolant is introduced into the annular space (77) between said refrigerant liquid seals (90), and wherein the cooling unit further comprises at least one discharge channel (91) of cooling liquid which extends from one or more discharge stations (92) in communication with the cylindrical passage (76) to an outlet for discharging said coolant from the annular space (77) between the piston rod (30) and the annular member (75); characterized by that The cooling unit (60) is provided, near one or each of the refrigerant liquid seals (90), of one or more respective damping gas seals (105) that delimit an annular damping gas space (104) at each axial end of the annular space in which the cooling liquid is flowed. Y wherein the cooling unit (60) is provided with one or more channels (102) of supply of damping gas which extend from a damping gas inlet to each of the annular damping gas spaces (104) to feed buffer gas thereto; and wherein the cooling system comprises a source of pressurized buffer gas that is adapted to establish a damping gas pressure in each of the damping gas spaces (104), and each damping gas space (104) acting to counteract the drag of liquid refrigerant on the outer surface of the piston rod (30) towards the outside of the cooling unit (60). 5. A method for compressing gas using the horizontal piston compressor according to claim 1.