Piston compressor
Patent Information
- Application Number
- ES2023000053T
- Authority / Receiving Office
- ES · ES
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2022-04-14
- Filing Date
- 2023-03-24
- Publication Date
- 2026-08-31
- Estimated Expiration
- 2043-03-24
Smart Images
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Abstract
Description
Piston compressor The invention relates to a piston compressor, comprising a crankshaft housing, a crankshaft disposed therein, connecting rods, a crosshead with a piston rod disposed therein, where at least one piston is fixed, which is guided dry-running in a cylinder, as well as valves and at least one piston rod sealing device, which is disposed around the piston rod between the cylinder and the crankshaft housing. Oil-free or dry-running high-pressure piston compressors are used for gas compression. Piston compressors are typically multi-stage and double-acting, meaning both the upper and lower pistons are used for compression. A linear compressor is known from document DE 102004052168 A1. Piston compressors are primarily used for gas compression. In double-acting compressors, the main components are a crankcase, a crankshaft mounted within it, at least one cylinder, connecting rods, a crosshead with a piston rod to which at least one piston is attached, main and connecting rod bearings, as well as sealing elements and valves. In such dry-running compressors, the high piston speed places particular stress on the piston and guide rings, as well as the piston rod seal, due to friction and undesirable high temperatures, which significantly reduces the service life of the sealing rings. A piston compressor is known from document DE 102004011410 B4, which features a piston rod seal for sealing a swiveling piston rod, where several sealing elements are arranged in the sealing housing between the piston rod and a rolling surface. These sealing elements are mounted on the outer circumference of the piston rod and are arranged on the rolling surface in the sealing housing or on the rolling surface of a rolling bushing arranged in the sealing housing, where the rolling surface may be surface-treated to increase wear resistance. In addition to document EP 2 594 795 A1, a device for compressing a gaseous fluid or a fluid composed of gaseous and liquid components is known, where the fluid is drawn in by a compressor and compressed therein in a compression chamber, where liquid is introduced into the compression chamber during compression. Furthermore, a double-walled, liquid-cooled, single- or multi-stage piston compressor is known from document DE 102013002864 A1. The compressor comprises at least one piston for compressing a medium, connected to a linear oscillating drive via a piston rod. The piston is axially movable within a cylinder, which is provided with cylinder heads on the piston side and the connecting rod side. The liquid cooling system consists of a shaped, double-walled cylinder with one or more cooling openings on the piston-facing side, through which the refrigerant flowing through the double-walled cylinder comes into contact with the cylinder area. A crankshaft housing typically has limited pressure sealing. Therefore, double-acting cylinders must be sealed extensively from the crankshaft housing using piston rod seals or stuffing boxes. Conventional stuffing boxes in oil-free compressors are constructed from sealing rings made of polymers. These sealing rings rest on the piston rod and are pressed against it by the pressure generated during compression. Such compressive forces against the reciprocating piston rod generate high frictional energy and significant wear on the sealing elements and the piston rod. In the case of a required operating mode of a compressor for generating high pressures, the wear of the gland elements is kept as low as possible by means of very complex gland systems with special cooling. WO 9831936 A1 discloses a compressor comprising at least one cylinder and a piston guided in the dry-running cylinder, which, with a cylinder insert, defines an annular gap open in each case through the common longitudinal section, allowing leakage of the compressed medium. The piston is coupled via a piston rod to a support piece guided movably in the direction of the longitudinal axis, which is connected to a drive device. The piston rod cooperates with the piston and the support piece via convex front support surfaces, which allow relative movement of the support piece with respect to the piston transverse to the longitudinal axis. Another known piston compressor is disclosed in document DE 33 10 184 A1; the compressor in this document does not include, among other things, the features that a stuffing box limits with a piston rod a sealing gap of narrowness on the order of m, open respectively over the common longitudinal section, allowing a gap leakage flow of the compressed medium; that the resulting coefficient of thermal expansion of the stuffing box and of the stuffing box sleeve essentially has the coefficient of thermal expansion of the material of the piston rod; and that the stuffing box device is supported without transverse force on a stuffing box flange with a plurality of ball elements, which are arranged around a vertical axis of the piston rod between a movable intermediate ring and a fixed ring. It has been shown that compressors running dry are particularly detrimental when, due to the high piston speed, the piston and guide rings, as well as the piston rod seal, are subjected to excessive friction and undesirable high temperatures. This excessive friction and undesirable high temperatures significantly reduce the service life of the sealing rings. The objective of the invention is to create a more developed high-pressure piston compressor, suitable for embodiments with selectable dimensions within a relatively large bandwidth and economically manufactured in a simple construction mode, which, with reduced construction costs in relatively long stroke embodiments, enables the formation of a dry-running annular gap seal for a piston rod seal, ensuring a constant leakage flow. The underlying objective is achieved according to the invention through the features of claim 1. It has proven particularly advantageous that the piston rod sealing device for the piston rod seal is implemented as a stuffing box device, which is housed in a stuffing box casing, which is incorporated into a piston compressor housing. The stuffing box device consists of a stuffing box and a stuffing box sleeve into which the stuffing box is inserted. The gland advantageously forms with the piston rod a sealing gap of narrowness on the order of m, open respectively over the common longitudinal section, which allows a gap leakage current of the compressed medium. The gland and gland sleeve are composed respectively of different materials, whose common resulting coefficient of thermal expansion advantageously presents essentially the coefficient of thermal expansion of the piston rod material. The cable gland assembly is advantageously connected to a flush, watertight, movable intermediate ring. The intermediate ring is advantageously arranged in a recess in the cable gland housing between the cable gland assembly and a pivot pin housing located in the recess of the cable gland housing. The stuffing box device is advantageously connected via the intermediate ring and the toggle pin housing with a ring, which is arranged in a notch of a stuffing box flange, which is firmly connected to the stuffing box housing and the piston compressor housing. The gland assembly is advantageously supported without transverse force by the gland through the intermediate ring on the gland flange with a plurality of ball elements, which are arranged around a vertical axis of the piston rod between the movable intermediate ring and the fixed ring. Furthermore, in a notch of the intermediate ring there is a pivoting ring which advantageously allows the gland device to readjust an oblique position of the piston rod without a significant force action of the piston rod on the gland device. The gland assembly is supported without transverse force on the gland flange advantageously by a plurality of pivot pins, which are arranged planetaryly around a vertical axis of the piston rod between the movable intermediate ring and the fixed ring. The toggle pins preferably have a length corresponding to a predetermined ball diameter and are made with domed ends with a radius equal to half the length of the toggle pin. Furthermore, the toggle pins are elastically coated with a suitable elastomer, such as a short piece of flexible tubing, in the area furthest from the pressure and are elastically positioned. The cable gland assembly is advantageously connected to the intermediate ring flush and watertight via a sealing ring arranged in a groove on the front surface of the pivot pin housing. The intermediate ring is advantageously hardened and ground and can be moved transversely without transverse force by the cable gland assembly. The intermediate ring also allows for the advantageous transfer of an axial force exerted on the cable gland device to the pivot pins, which are movably arranged as ball elements between the intermediate ring and the hardened ring. The swing ring preferably has on its front sides a very large radius of curvature, which is curved in the shape of a barrel, where the axes of the barrel curvatures are offset 90º from each other on both front sides of the swing ring. Furthermore, it has proven advantageous that the tilting ring allows the gland device to follow an inclination of the piston rod, caused by a transverse movement of the piston rod, without a significant force between the gland device and the piston rod. Furthermore, it has proven particularly advantageous that the tilting ring allows small pitching movements of the gland assembly in all directions. Other advantages and features of the invention are explained in more detail in the description by means of embodiment examples represented schematically in the drawing. They show: Fig. 1 shows a schematic sectional piston compressor at reduced scale according to the invention and a detail Z at enlarged scale; Fig. 2 an example embodiment according to detail Z of a piston rod sealing device with gap ring seal in the section of a piston compressor according to Fig. 1 according to the invention and a section II in plan view; Fig. 3 shows an example of an embodiment of a piston rod sealing device with a gap ring seal and a tilting ring in section according to Fig. 2 according to the invention; Fig. 4 is a cross-sectional representation of a rocker ring according to an example of an embodiment of a piston rod sealing device according to Fig. 3 of the invention; Fig. 5 is a schematic representation of a support for an intermediate ring with balls in section according to an example of an embodiment of a piston rod sealing device according to Fig. 2 of the invention; Fig. 6 is a schematic representation of a support for an intermediate ring with pins in section according to an example of an embodiment of a piston rod sealing device according to Fig. 2 of the invention; and Fig. 7 is a representation of a support for an intermediate ring with pins in a resilient housing in section according to an example of an embodiment of a piston rod sealing device according to Fig. 2 of the invention. Fig. 1 schematically shows a piston compressor 10, comprising a crankshaft housing 11 with a crankshaft 12, as well as connecting rods 13 and at least one crosshead 14 with a piston rod 15 mounted in each case in the crosshead, where pistons 16.0, 16.1 and 16.2 are respectively fixed.Pistons 16.0, 16.1 are arranged in double-acting cylinders 17.0, 17.1 and piston 16.2 is arranged axially movable in a single-acting cylinder 17.2. In addition, in the double-acting cylinders 17.0 and 17.1, for sealing the piston rod 15 with respect to the crankshaft housing 11, valves 18 are arranged for gas intake or exhaust and, in each case, a piston rod sealing device 19. In detail Z, on the enlarged scale with a break line, the crankshaft housing 11, the piston rod 15, and the piston 16.0 attached to the piston rod are shown. The piston 16.0 is movably guided in the cylinder 17.0. Also shown are the valves 18 and the piston rod sealing device 19, which is arranged in a piston compressor housing 20 around the piston rod 15. Figure 2 shows an example of the piston rod sealing device 19 with a gap ring seal in the section of a piston compressor 10 according to detail Z as shown in Figure 1. The piston rod 15 is arranged in the indicated piston compressor housing 20, where a stuffing box housing 21 for the piston rod sealing device 19 is incorporated. The piston rod sealing device 19 comprises a stuffing box device 22 consisting of a stuffing box sleeve 24 and a stuffing box 23 inserted therein. The stuffing box 23 of the stuffing box device 22 contacts the surface of the piston rod 15 with a clearance of a few mm above an indicated sealing gap 25, which is configured between the surface of the piston rod 15 and the stuffing box 23. A gap ring seal is a flow seal. A small gap leakage stream 26 is indicated by an arrow. Approximately 3% of the compressor flow rate is the magnitude of the gap leakage stream, which forms in the sealing gap 25, located between the reciprocating piston rod 15 and the stuffing box 23. The gap leakage stream 26 seals a gap ring seal against high pressure differentials, which in each case are between a cylinder pressure 27 and a crankshaft housing pressure 41, where the pressure of the gap leakage stream 26 is continuously reduced along the entire length of the sealing gap 25. The cable gland 23 of the cable gland assembly 22 typically has a manufacturing clearance of approximately 15 µm in front of the piston rod 15. The cable gland 23 is preferably made of CF-PEEK (carbon fiber polyether ether ketone) and has clearance against the surface of the piston rod 15. The cable gland 23 is pressed into the cable gland sleeve 24, which is made of steel. Both the cable gland 23 and the cable gland sleeve 24 are made of materials that allow the cable gland to exhibit approximately the same thermal expansion on the surface opposite the piston rod 15 as the surface of the piston rod 15. The crimping between the carbon fiber PEEK cable gland 23 and the cable gland sleeve 24 is temperature-dependent and can be kept essentially constant within the predetermined temperature ranges of the permissible operating conditions. A gap ring seal operates virtually without friction and is therefore particularly suitable for oil-free or dry-running piston compressors to seal high pressure differentials of typically 150 bar or more. The stuffing box 22, as indicated by an arrow, is subjected to an axial force 29, resulting from a differential pressure formed by the predominant cylinder pressure 27 in cylinder 17 and the existing pressure 41 in the crankshaft housing 11. Such high pressures do not predominate in the interior of the sealing gap 25 due to the reduction in pressure within the sealing gap. Because of the pressure differential, the stuffing box 22 is compressed, and the sealing gap 25 decreases in size as the cylinder pressure 27 increases. The sealing gap 25 and the stuffing box 23 communicate or interact with each other, and the sealing gap always has a width of approximately one (1) m between the surface of the piston rod 15 and the opposite surface of the stuffing box. The reciprocating piston rod 15 also moves slightly transversely to the imaginary cylinder axis. The stuffing box device 22, which is supported by the stuffing box 23 with a clearance of approximately two (2) m on the piston rod 15, must be able to follow such slight transverse movements, namely, without a large or significant force action of the piston rod 15 on the stuffing box 23. The stuffing box assembly 22 is connected to an intermediate ring 28. The intermediate ring 28 is movably arranged in a recess in the stuffing box housing 21. A toggle pin housing 36 is also incorporated in the recess of the stuffing box housing 21, behind the intermediate ring 28. The intermediate ring 28 is flush and watertight with the stuffing box assembly 22. The stuffing box assembly 22 is subjected to axial force 29 and allows pressure to be exerted through the intermediate ring 28 and the toggle pin housing 36 on a ring 30, which is arranged in a recess in a stuffing box flange 31. The stuffing box flange 31 is fixedly connected to the stuffing box housing 21 and the piston compressor housing 20. If the intermediate ring 28 and ring 30 were directly above each other, then a static friction would have to be overcome for a transverse displacement of the gland device 22. Static friction for transverse displacement of the stuffing box device 22 is prevented by the arrangement of a plurality of so-called ball elements 32 or toggle pins 33 in the toggle pin housing 36. The ball elements 32 or toggle pins 33 are arranged planetaryly around a vertical axis of the piston rod 15 between the movable intermediate ring 28 and the fixed ring 30, as shown in Figures 2 and 5 and represented in a section II or a half-section in a plan view. The toggle pins 33 are coated on their underside, opposite the ring 30, with a flexible elastomer 35. As shown in Figure 3, a toggle ring 38 is arranged between the stuffing box device 22 and the intermediate ring 28 in a recess in the intermediate ring.The pivoting ring 38 allows the gland device 22 to follow an inclination of the piston rod 15 by means of a transverse movement of the piston rod without a significant force action between the gland device and the piston rod. The swivel ring 38 is comparable to a cross joint. The swivel ring 38 can only transmit compressive forces in the axial direction. The swivel ring 38 allows small pitching movements of the gland assembly 22 in all directions. Figure 4 shows a schematic image of a tilting ring 38 in plan view and in side view, sections AA and BB, rotated 90° respectively. The front sides 39 of the tilting ring 38 are barrel-shaped with a very large radius of curvature 40. The axes of the barrel curves on both front sides of the tilting ring 38 are offset by 90° from each other. The ball elements 32 are, in the simplest case, balls, as depicted in Fig. 5. The balls are arranged between the intermediate ring 28 and the ring 30 arranged in the gland flange 31 and positioned around the piston rod 15 as can be seen in the half-section. The axial force 29 applied to the ball elements 32 through the intermediate ring 28 is, in the optimal case, evenly distributed over the number of ball elements. In the case of high pressure differentials in the gland assembly 22, the Hertzian compression on the ball elements 32 and the predetermined bearing surfaces can be very high. The Hertzian pressing p0 depends geometrically on the ball radius according to the following relationship: Example: If the ball radius r increases by a factor of 10, the Hertzian pressing p0 is reduced by a factor of 4.6. Figure 6 shows, in illustrative terms, ball elements 32 in use with a large ball diameter. A large ball is reduced almost to a so-called rocker pin 33. The rocker pins 33 each have a length of a predetermined ball diameter and have domed ends 34 with a radius half the length of a rocker pin. The rocker pins 33 are arranged between the intermediate ring 28 and the ring 30 fixed to the gland flange 31 and positioned planetaryly around the piston rod 15, as can be seen in the half-section. The axial force 29 applied to the rocker pins 33 through the intermediate ring 28 is, in the optimal case, distributed evenly over the number of rocker pins. The pivot pins 33 are elastically positioned in the area away from the pressure by means of a suitable elastomer 35, for example, a short piece of a flexible tube according to fig. 2, fig. 7. The intermediate ring 28 can be hardened and ground and moved transversely without transverse force by the gland device 22. The axial force 29 exerted on the intermediate ring 28 is distributed evenly between the rocker pins 33 arranged in the rocker pin housing 36, which are movably arranged like balls between the intermediate ring 28 and the hardened ring 30. The rocker pins 33 are arranged between the intermediate ring 28 and the ring 30 fixed in the gland flange 31 and positioned around the piston rod 15 in a planetary fashion, as can be seen in the half-section. The toggle pins 33 have a length that, in the loaded state of the toggle pins, is several m longer than the toggle pin housing 36. A sealing ring 37 made of PTFE material is arranged between the intermediate ring 28 and the toggle pin housing 36. The sealing ring 37 bridges an axial gap not shown between the intermediate ring 28 and the toggle pin housing 36 and seals this gap, thereby preventing additional gap leakage current. A slight tilting of the piston rod 15 may occur relative to a transverse movement of the piston rod. The gland device 22 allows this tilting to occur without a large or significant force being exerted between the gland device and the piston rod 15. A compressor with a stuffing box based on a gap ring seal offers the following advantages. In dry-running compressors, due to the high piston speed, the piston and guide rings, as well as the piston rod seal, are subjected to undesirable high temperatures due to friction. This significantly reduces the service life of the sealing rings. In single- or multi-stage double-acting piston compressors, the piston rod seal can withstand high pressures exceeding 150 bar generated in the cylinders at high piston speeds, as a near-contact flow seal is configured as a piston rod sealing device 19 with a gap ring seal. The piston rod sealing device 19 comprises a specially configured stuffing box 22 within a stuffing box housing 21 consisting of a stuffing box 23 and stuffing box sleeve 24, as well as an intermediate ring 28, a pivot ring 38, and pivot pins 33. The special configuration of the piston rod sealing device 19, with a heat-shrinkable compound of the stuffing box 22 made of CF-PEEK material for the stuffing box 23 and steel for the stuffing box sleeve 24, allows for the reproduction of the coefficient of thermal expansion of the piston rod 15. The stuffing box 22 can be supported without transverse force by means of pivot pins 33 arranged planetaryly around the axis of the piston rod 15. The pivot ring 38 allows the stuffing box 22 to readjust a small inclination of the piston rod 15 without significant force. Due to the special configuration of the piston rod sealing device 19, special cooling for the cylinder and piston rod seal is eliminated in single or multi-stage double-acting piston compressors.
Claims
1. A piston compressor comprising a crankshaft housing (11), a crankshaft (12) disposed therein, connecting rods (13), a crosshead (14) with a piston rod (15) disposed therein, wherein at least one piston (16) is fixed, which is dry-running guided in a cylinder (17), as well as valves (18) and at least one piston rod sealing device (19), which is disposed around the piston rod (15) between the cylinder (17) and the crankshaft housing (11), wherein the piston rod sealing device (19) comprises a stuffing box device (22), wherein the stuffing box device (22) is disposed in a stuffing box housing (21) which is incorporated in a piston compressor housing (20), wherein the stuffing box device (22) has a stuffing box (23) and a stuffing box sleeve. (24) , where the cable gland (23) is inserted,where the stuffing box (23) limits with the piston rod (15) a sealing gap (25) of narrowness on the order of µm, open respectively over the common longitudinal section, allowing a gap leakage current (26) of the compressed medium, where the stuffing box (23) and the stuffing box sleeve (24) are respectively made of different materials, the resulting coefficient of thermal expansion of which is essentially the coefficient of thermal expansion of the material of the piston rod (15), where the stuffing box device (22) is flush and leak-proofly connected with a movable intermediate ring (28), which in a notch of the stuffing box housing (21) is disposed between the stuffing box device (22) and a pivot pin housing (36) disposed in the notch of the stuffing box housing,where the stuffing box device (22) is connected via the intermediate ring (28) and the toggle pin housing (36) to a ring (30), which is arranged in a notch of a stuffing box flange (31), which is fixedly connected to the stuffing box housing (21) and the piston compressor housing (20), where the stuffing box device (22) is supported without transverse force on the stuffing box flange (31) by a plurality of ball elements (32 / 33), which are arranged around a vertical axis of the piston rod (15) between the movable intermediate ring (28) and the fixed ring (30),and wherein the stuffing box device (22) allows readjustment of an oblique position of the piston rod (15) without significant force action of the piston rod on the stuffing box device by means of a pivot ring (38) disposed in a recess of the intermediate ring (28).
2. Piston compressor according to claim 1, wherein the stuffing box device (22) is supported without transverse force on the stuffing box flange (31) by a plurality of pivot pins (33), which are arranged planetaryly around a vertical axis of the piston rod (15) between the movable intermediate ring (28) and the fixed ring (30).
3. Piston compressor according to claim 2, wherein the pivot pins (33) have a length of a predetermined ball diameter and domed ends (34) with a radius of half the length of a pivot pin.
4. Piston compressor according to claim 2,wherein the rocker pins (33) are elastically coated with a suitable elastomer (35), such as a short piece of flexible tubing, in the area away from the pressure and elastically positioned.
5. Piston compressor according to claim 1, wherein the stuffing box device (22) is connected to the intermediate ring (28) flush and leak-proof via a sealing ring (37) arranged in a groove in a front surface of the rocker pin housing (36).
6. Piston compressor according to claim 5, wherein the intermediate ring (28) is hardened and ground and can be moved transversely without transverse force by the stuffing box device (22).
7. Piston compressor according to claim 6, wherein the intermediate ring (28) allows an axial force (29) exerted on the stuffing box device (22) to be transmitted to the rocker pins (33).which are movably arranged as ball elements (32) between the intermediate ring (28) and the hardened ring (30).
8. Piston compressor according to claim 1, wherein the tilting ring (38) has a very large radius of curvature (40) on its front sides (39), which is barrel-shaped, wherein the axes of the barrel curvatures are offset by 90° from each other on both front sides of the tilting ring.
9. Piston compressor according to claim 7, wherein the tilting ring (38) allows the stuffing box device (22) to follow an inclination of the piston rod (15) by means of a transverse movement of the piston rod without a significant force action between the stuffing box device and the piston rod.
10. Piston compressor according to claim 7, wherein the tilting ring (38) allows small pitching movements of the stuffing box device (22) in all directions.