Description

Reciprocating compressor

Technical Field

The present invention relates to a gas compressor and in particular to a multi-stage compressor which can be used in stations for distribution of the gas.

Background Art

Gases are normally compressed using positive displacement compressors which, to reach very high compression ratios (up to 300 atm and above), are usually of the multi-stage type. To keep the description simple, without limiting the scope of the invention, the following description refers to reciprocating compressors, substantially known and therefore not described in detail.

Such compressors comprise, schematically, a rotary part, housed in a suitable casing, to which a driving shaft is keyed, able to rotate about its axis, driven by an external source of motion.

The rotary part and the source of motion are interconnected and are supported by a frame which allows them, amongst other things, to rest on the ground or be suspended.

The rotary part comprises pistons driven by the driving shaft by means of suitable mechanisms which allow the pistons reciprocating linear motion in seats made in the casing, during driving shaft rotation. The gas is compressed;, to the desired pressure in successive

V ■ stages, that is to say, it .is compressed first by one piston then conveyed to the next and so on until the desired pressure is reached.

As is known, to prevent the compressed gas from reaching high temperatures especially at the end of the entire compression

process, the gas is suitably cooled between one compression stage and the next.

To achieve said cooling, known compressors are normally equipped with heat exchangers in which the gas circulates together with a coolant fluid, for example water.

In practice, between one piston and another, the gas is moved along a circuit extending at least partly inside a second circuit in which the coolant fluid circulates .

In particular, said second circuit is associated with the supporting frame and its pipes extend around the motor and rotary part assembly.

Known compressors are also equipped with systems for cooling the lubricants usually present in the rotary part and systems for cooling the piston seats . Such a solution has several disadvantages.

In particular, the coolant liquid circuit is wound on the supporting frame and is an obstacle around the compressor and, at least partly, exposed to impacts and damage.

Assembling it is laborious and uneconomic because a superstructure of pipes has to be produced, to be associated with the motor - rotary part unit .

Moreover, said superstructure is unsightly and does not blend in with the rest of the compressor.

Disclosure of the Invention

In this context, the main technical purpose of the present invention is to propose a multi-stage gas compressor with a simple and compact coolant liquid circuit .

It is another aim of the present invention to propose a gas compressor which has superstructures for the circulation of coolant liquids that are easy to assemble and are not an obstacle close to the compressor.

The technical purpose indicated and the aims specified are substantially achieved by a compressor described in claim 1 and in one or more of the dependent claims herein.

Brief Description of the Drawings

Further features and advantages of the present invention are more apparent in the detailed description below, with reference to a preferred, non-1inviting, embodiment of a compressor, illustrated in the accompanying drawings, in which: Figure 1 is a schematic perspective view, with some parts cut away for greater clarity, of a first embodiment of a compressor in accordance with the present invention;

Figure 2 is a schematic front view from A, with some parts cut away for greater clarity, of the compressor from Figure 1; Figure 3 is a schematic rear view from B of the compressor from Figure 1;

Figure 4 is a schematic side view of the compressor from Figure 1;

Figure 5 is a top plan view of the compressor from Figure 1; Figure 6 is a diagram relating to the gas cooling circuit in the compressor from Figure 1;

Figure 7 is a diagram relating to the gas cooling circuit in a second embodiment of a compressor in accordance with the present invention; Figure 8 is a diagram relating to the gas cooling circuit in a third embodiment of a compressor in accordance with the present invention;

Figure 9 is a schematic top plan view of a fourth embodiment of a compressor in accordance with the present invention; Figure 10 is a schematic top plan view of a fifth embodiment of a compressor in accordance with the present invention.

Detailed description of the Preferred Embodiments of the Invention

With reference to the accompanying drawings and in particular with reference to Figure 1, the numeral 1 denotes a reciprocating compressor in accordance with the present invention.

Said type of compressor is preferably designed to compress natural gas and is of the substantially known type and therefore a detailed description of it is limited to the parts necessary for an understanding of the text and the invention.

The compressor 1 comprises an electric motor 2 which forms motor means 3 for driving positive displacement compression means

Said compression means 4 comprise a casing or box 5 having a plurality of heads 6, 7 and 8 in which respective mobile pistons are inserted, driven in the substantially known way by the motor 2 using a driving shaft, not illustrated.

The positive displacement compression means 4 are preferably lubricated, using suitable lubricants, and cooled as described in more detail below.

The pistons, not visible in the accompanying drawings, are driven by the driving shaft by means of suitable mechanisms, moving with reciprocating linear motion to compress the gas in seats made in the relative heads 6 , 7 and 8.

The compressor 1 has an inlet 9 for the gas at a pressure PO and an outlet 10 from which the gas comes out at a pressure Pl which is greater than PO after gas compression in the compressor 1.

In particular, the gas is compressed to the pressure Pl in successive stages 6a, 7a, 8a, 8b, that is to say, it is compressed first by one piston then conveyed into the next and so on until the desired pressure is reached. In the solution illustrated by way of example, in particular with reference to Figures 1, 5, 6 the gas comes out of a first compression stage 6a, from the head 6, and is fed, in a direction Vl, along a first duct 11 which passes through a first heat exchanger 12. Then, the gas is fed through a second duct 13 from the heat exchanger 12 to the head 7, into a second compression stage 7a.

When it comes out of the head 7, moving in direction Vl in a third duct 14, the gas passes through a second exchanger 15.

When it comes out of the second exchanger 15, a fourth duct 16 conveys the gas to the head 8 for a third compression stage 8a.

From the head 8, a fifth duct 17 conveys the gas, in the direction Vl, through a third exchanger 18.

When it comes out of the third exchanger 18, a sixth duct 19 feeds the gas to the head 8 for the fourth and final compression stage 8b.

From the head 8 a seventh duct 20 feeds the gas into a fourth exchanger 21, from which it is fed out at the pressure Pl and an

eighth duct 22 feeds the gas to the outlet 10.

It should be noticed that before coining out of the outlet 10, the gas passes through a damper or separator 60, of the substantially known type and not described in detail. The exchangers 12, 15, 18, 21 are part of a gas cooling circuit 23 and are preferably of the counter-current flow type.

In general, a coolant liquid, for example water, moving in a direction V2 opposite to the direction Vl, in the exchangers 12, 15, 18, 21 flows close to the ducts 11, 14, 17, 20, exchanging heat with the gas circulating in them.

In alternative embodiments not illustrated, the exchangers are of the parallel flow type and the coolant liquid and the gas circulate in them in the same direction.

The motor means 3, together with the positive displacement compression means 4, the exchangers 12, 15, 18, 21, the ducts 11, 14, 17, 20, the ducts 13, 16, 19, 22 and the exchanger 60 are supported by supporting means 24.

In the preferred embodiment illustrated in Figures 1 to 5 the supporting means comprise a first and a second structural element 25, 26 or cross-members.

Said first and second elements 25, 26 are respectively positioned at the motor means 3 and positive displacement compression means 4.

The elements 25 and 26 are transversal, substantially perpendicular, to a main direction L of extension of the ^" compressor 1.

It should be noticed that the elements 25 and 26 together with the exchangers 12, 15, 18, 21 form gas cooling means 50.

In particular, the elements 25 and 26 are part of the cooling circuit 23.

As illustrated in Figures 1 to 7, the exchangers 12, 15, 18, 21 are in fluid communication with the structural elements 25, 26 to form the gas cooling circuit 23.

In more detail, the elements 25 and 26 form manifolds for the coolant liquid.

With particular reference to Figure 6, assuming for the sake of simplicity, without limiting the scope of the invention, that

the element 26 is a coolant liquid intake manifold, said liquid passes from the element 26 to the exchangers 12, 15, 18, 21 respectively through tubular inlet connectors 27, 28, 29, 30.

Assuming, without limiting the scope of the invention, that the element 25 is a coolant liquid outlet or discharge manifold, said liquid comes out of the exchangers 12, 15, 18, 21 then goes into the element 25 through tubular discharge connectors 31, 32,

33, 34.

Advantageously, in alternative embodiments not illustrated, the element 25 is used as an intake manifold and the element 26 as a discharge manifold, so that the exchangers 12, 15, 18, 21, without changing the direction of the gas, operate with parallel flow.

As illustrated in particular in Figures 4 and 6, the compressor 1 comprises means 35 for introducing the liquid into the cooling circuit 23, for example a tap, associated in particular with the element 26.

The compressor 1 also comprises discharge means 36 for getting the coolant liquid out of the circuit 23, for example a tap, associated in particular, with the element 25.

With particular reference to Figure 6 , it should be noticed that the compressor 1 comprises an exchanger 100 for cooling the lubricant for the positive displacement compression means 4.

Advantageously, the exchanger 100 is in fluid communication, by means of a duct 101 and a duct 102, respectively with the element 26 and with the element 25, so that the gas coolant liquid also cools the lubricant for the compression means 4.

Said lubricant, mobile in a direction V3, is circulated, in the substantially known way, in the exchanger 100 by means of a duct 107.

The lubricant goes into the duct 107 through an inlet 103 and comes out of it through an outlet 104.

In this way the lubricant cooling circuit is also compact and the supporting means 24 partly comprise it. With reference to Figures 1, 3, 5, it should be noticed that a head 6, 7, 8 cooling circuit, for the sake of simplicity only illustrated only relative to head 8, is also fed by the manifolds

25 and 26.

In the preferred embodiment illustrated, the head 8 cooling circuit, of the substantially known type and described only regarding the part relating to the present invention, is fed by a duct 105 which conveys the coolant liquid from the element 26, the intake manifold, to the head 8.

The same circuit also comprises a duct 105 which conveys the coolant liquid from the head 8 to the element 25, the discharge manifold. The circuit 23 is completed by refrigeration means, for example radiant masses not illustrated, which receive the liquid fed out (hot) from the element 25, cool it and convey it, in the substantially known way, back to the means 35 for introducing it into the element 26. As illustrated in Figures 1 to 5, the supporting elements

25, 26 are designed to allow the compressor 1 to rest on the ground whilst the rigid connection between the motor means 3 and the positive displacement compression means 4 is guaranteed by connecting means 37. In the preferred embodiment illustrated, the connecting means 37 comprise a connecting spider 38 of the substantially known type .

Therefore, in said embodiment the elements 25 and 26, as already indicated, are for resting on the ground and preferably have, respectively, one supporting bracket 39 and two brackets 40 and 41 which form a single supporting plane and which guarantee compressor 1 equilibrium.

In particular with reference to Figure 1, it should be

^■ noticed that the compressor 1 ■comprises auxiliary service means 70, for example electric panels and boxes, pressure transducers, of the known type and not described in detail, which are supported by the connecting means 37, in particular by the connecting spider

38.

As illustrated in Figure 7 , in a different embodiment the supporting means 24 comprise a third and a fourth structural element 42, 43 forming, together with the first and second elements 25, 26, a supporting frame 44.

The elements 42 and 43 themselves form exchangers 45 and 46 in which the ducts 20, 17 and 11, 14 respectively run together with the coolant liquid.

In practice, the entire cooling circuit 23 circulates inside the frame 44 which is equipped with the means 35 and 36 for introducing and discharging the coolant liquid.

Moreover, in said case, the frame 44 forms the connecting means 37 between the motor means 3 and the positive displacement compression means 4 which are connected to one another by transmission means of the known type and not illustrated.

The cooling circuit 23 is preferably closed by transfer ducts 45, 46, 47, 48 between the structural elements 25, 26, 42, 43.

As illustrated in Figure 8, the structural elements 25, 26 both have means 35 for introducing the coolant liquid and means 36 for discharging the coolant liquid.

The ducts 17, 20 are inserted in the element 25 and the gas passes in them with a consequent heat exchange.

The ducts 11, 14 are inserted in the element 26 and the gas passes in them with a consequent heat exchange.

In other words, the structural elements 25, 26 themselves form the exchangers 18, 21 and 12, 15.

In this way, the gas cooling circuit 23 is further simplified and almost completely inserted in the supporting means 24.

The latter solution can be produced either when the supporting elements 25, 26 are designed for resting the compressor on the ground and the rigid connection between the motor means 3 and the positive displacement compression means 4 is guaranteed by the connecting means 37, or when, as illustrated with a dashed line, the supporting means ^' 24 comprise a third and a fourth structural element 42, 43 forming, together with the first and second elements 25, 26 the frame 44 for supporting and connecting the motor means 3 and the compression means 4. As illustrated in Figure 9, in the preferred embodiment illustrated, the element 25 is smaller than the element 26 and is only for resting the compressor 1 on the ground, without being

affected by the cooling circuit 23.

In particular, the element 25 is preferably as wide as the electric motor 2 to allow it to rest stably on the ground.

The ducts 11, 14, 17, 20, of which only two are visible in the accompanying drawings, are all inserted in the supporting structural element 26 which therefore forms a single gas cooling exchanger .

The ducts 11, 14, 17, 20 pass through the element 26 from a first end 110 to a second end 111, transversally to the direction L of extension of the compressor 1.

Therefore, the element 26 has means 35 for introducing the coolant liquid and means 36 for discharging it.

In the preferred embodiment illustrated by way of example, said means 35 and 36 are positioned in such a way that the coolant liquid circulates in the direction V2 with counter-current flow relative to the gas, which moves in the direction Vl.

Advantageously, in alternative embodiments not illustrated, the liquid and the gas circulate in the same direction in the element 26, exchanging heat between them. As illustrated in Figure 10, the ducts 11, 17 are bent and go into and come out of the structural element 26 at the end 110.

The ducts 14, 20 are bent and go into and come out of the structural element 26 at the second end 111.

It should be noticed that there is only one set of means 35 for introducing coolant liquid, positioned substantially at a middle portion 112 of the element 26.

The means 36 for discharging the liquid are at both the end 110 and the end 111.

In this way gas cooling in the ducts 11, 17 and 14, 20 occurs partly with a counter-current flow and partly with a parallel flow.

The invention described brings important advantages.

The gas cooling circuit is simple and compact, without projecting from the outline of the compressor. The cross-members are part of the cooling circuit, that is to say, the water goes into and comes out of them to close the water - gas exchangers circuit, allowing savings in terms of material and

structural work.

The cross-members themselves may form the heat exchangers and take on a dual role, both supporting and cooling.

Once the individual structural work elements of which the compressor consists are produced, assembly and testing of the compressor with the cooling circuit is more rapid than with conventional assemblies .

The connection between the motor and the compression means using the spider is simple to produce and assemble. Assembly with cross-members and the spider guarantees significant savings in terms of storage space because the structural work is easy to stow, even painted.

The invention described has evident industrial applications and may be modified and adapted without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements .