Test stand for fluid lines or fluid containers

Abstract

A test stand for fluid lines or fluid containers (1) comprises a test-liquid reservoir (3) and a closure head (6) having a throughflow-channel arrangement (7) for test liquid, connected to which is a filling and pressure-generating unit (4) for the test liquid communicating with the test-liquid reservoir (3). This unit comprises an air-hydraulic pressure booster (10) having a main body (11) and a piston unit (16) which is accommodated therein in such a way as to allow it to oscillate and form two primary working chambers (21), which are opposingly volume-variable and can each be acted on via a compressed-air connection (20), and two secondary working chambers (22), which each have an associated suction check valve (27) and pressure check valve (28). The two secondary cylinders (13) have different diameters. And the fluidic connection of the two pressure check valves (28) to the throughflow-channel arrangement (7) of the closure head (6) can be switched into at least two different operating states, wherein, in at least one of the operating states, the throughflow-channel arrangement (7) of the closure head (6) is only acted upon from one of the two secondary working chambers (22).

Description

[0001] Test bench for fluid lines or containers

[0002] The present invention relates to a test bench for fluid lines or containers, in particular for hydraulic lines, comprising a test fluid reservoir and a sealing head designed for tight interaction with an end fitting of the fluid line or fluid container to be tested, with a flow channel arrangement for test fluid, to which a filling and pressure generation unit for the test fluid, communicating with the test fluid reservoir, is connected.

[0003] Depending on their intended use, fluid lines are subject to mandatory leak testing.

[0004] Pressure resistance. Particularly stringent testing procedures apply to hydraulic lines due to the very high pressures typically present in operation and the associated risk to personnel in the event of a failure. The so-called "pressure test," i.e., the leak test, is regularly carried out using a test fluid with which the fluid line to be tested is filled and then subjected to the specified test pressure.

[0005] Test rigs designed and equipped for such pressure and leak testing are known from patent literature (see, for example, US 1,637,956 A, DE 839,103 A, US 3,334,515 A, US 4,192,177 A, US 4,413,501 A, US 5,419,184 A, US 6,997,044 A, and DE 10,2019,108,230 B3) and from practical application (see, for example, the applicant's test rigs P160, P180, P250, P320, and P350). CN 2 04 831 938 U also deals with a test rig for pressure testing a pipe or line. According to this document, in the interest of self-adaptation of the device to lines with different diameters, such a device...

[0006] The test rig, comprising a test fluid reservoir, features a conical sealing head designed and configured for tight interaction with an end fitting of the pipe under test, and includes a flow channel arrangement for the test fluid. The same applies to a second sealing head, which is equipped with a pressure relief valve and a drain valve for the test fluid.

[0007] To subject the test fluid (e.g., in the form of a water-oil emulsion) to the intended high test pressure (e.g., between 150 bar and 1,500 bar), various methods are known, including the use of an oscillating pressure intensifier operated on the primary side with 7 bar compressed air. For such pressure intensifiers, particularly pneumatic-hydraulic pressure intensifiers, reference should be made, for example, to CN 2 14 221 416 U and US 2007 / 0128053 Al. The aforementioned CN 2 14 221 416 U discloses a pneumatic-hydraulic pressure intensifier in the form of a double-piston pump, in which a tandem cylinder arrangement is provided on the primary side, such that two functionally parallel pneumatic cylinders are actuated synchronously.One of the special features of the double piston pump according to US 2007 / 0128053 Al, which forms a pneumatic-hydraulic pressure intensifier, is that two cylinder-piston units with different working surfaces can be provided on the secondary side, which allows the provision of hydraulic fluid at two different pressure levels.

[0008] The above statements regarding pressure and leak testing of pipes apply in a comparable manner to fluid containers which - unlike fluid pipes with two openings provided in each end fitting - only have one opening, such as pressure vessels.

[0009] Based on this prior art, the present invention aims to provide a test bench of the type mentioned above that is improved with regard to practical use, with particular importance in terms of practical relevance being high reliability, low acquisition costs and the shortest possible test cycles.

[0010] The above task is solved by a test bench of the type mentioned at the beginning, which is further characterized by the following features:

[0011] - the filling and pressure generation unit includes an air-hydraulic pressure booster;

[0012] - in a basic body of an air-hydraulic pressure booster, a primary cylinder is designed in which a primary piston is guided oscillatively along a working axis, which defines two primary working chambers with opposing volume-variable movements, each of which can be actuated via a compressed air connection, wherein the two compressed air connections are connected to a primary air control unit;

[0013] - in the base body two secondary cylinders oriented parallel to the working axis and arranged on different sides with respect to the primary piston are provided, into which secondary pistons rigidly connected to the primary piston plunge, wherein each secondary cylinder and the associated secondary piston define a secondary working space;

[0014] - Each of the secondary working chambers is connected to a suction check valve that can be fluidically connected to the test fluid reservoir and to a pressure check valve;

[0015] - the two secondary cylinders have different diameters;

[0016] - the flow-technical connection of the two pressure check valves with the flow channel arrangement of the closure head can be switched into at least two different operating states, whereby in at least one of the operating states the flow channel arrangement of the closure head is only supplied from one of the two secondary working chambers .

[0017] Of particular importance, in synergistic interaction with the other features characteristic of the test rig according to the invention, is the special feature that the two secondary cylinders have different diameters and that the flow-related connection of the two pressure check valves with the flow channel arrangement of the valve head can be switched into at least two different operating states, wherein in at least one of the operating states the flow channel arrangement of the valve head is acted upon by only one of the two secondary cylinders. In particular, this design of the test rig allows the secondary side of the filling and pressure generation unit, which is characterized by the larger diameter of the secondary cylinder, to be used for the rapid filling of the fluid line under test.of the fluid container to be tested with the test fluid, whereas this secondary side is not used for building up the high test pressure in the fluid line to be tested, in particular by being hydraulically short-circuited, i.e. from the.

[0018] The test fluid reservoir is drawn in and returned to it without pressure. In this way, without adversely affecting the duration of the respective test cycle, a separate filling pump for the test fluid, which is required in various test benches according to the state of the art, can be dispensed with. This results in less construction effort and thus lower manufacturing or acquisition costs for the test bench, and, due to the low technical complexity of the test bench, also improves its reliability.

[0019] In the sense described above, the essential feature of the invention, namely that the flow-related connection of the two pressure check valves with the flow channel arrangement of the valve head can be switched into at least two different operating states, is to be understood as meaning that direct intervention in the fluid-conducting connection between the flow channel arrangement and the respective pressure check valve is possible, but not necessarily required. This is because diverting the test fluid conveyed by the respective pressure check valve back into the system via a valve-controlled bypass is also possible.

[0020] The test fluid reservoir, which does not necessarily involve a direct intervention in the fluid-conducting connection between the flow channel arrangement and the respective pressure check valve, fulfills the aforementioned requirement according to the invention.

[0021] Depending on the type of test specimen, i.e., the fluid system being tested—a line with two (or, in the case of a branch, at least three) openings, or a container with only one opening—the test rig has one, two, or, if necessary, at least three sealing heads. With two sealing heads, both, or with three or more, at least two of them, can have a flow channel arrangement for the test fluid. This facilitates and speeds up the filling of the fluid line with the test fluid by displacing the air within it. Each flow channel arrangement can comprise one or more flow channels.

[0022] According to a first preferred embodiment of the present invention, the flow channel arrangement used for filling the test specimen and building up pressure within it can be selectively connected fluidically to either both pressure check valves or only one of the two pressure check valves, specifically only to the pressure check valve assigned to the secondary cylinder with the smaller diameter. In this embodiment, (in the first operating mode) not only the secondary side of the filling and pressure generation unit characterized by the larger diameter of the secondary cylinder contributes to filling the fluid line under test with the test fluid, but also the other secondary side of the filling and pressure generation unit, characterized by the smaller diameter of the secondary cylinder. This allows for a minimization of the filling time and thus the duration of the entire test cycle.

[0023] Without foregoing this advantage, the test rig according to the present invention can also be characterized by the fact that the flow channel arrangement used for filling the test specimen and building up pressure within it can be selectively connected either only to the pressure check valve assigned to the secondary cylinder with the larger diameter or only to the pressure check valve assigned to the secondary cylinder with the smaller diameter. In this variant, the secondary side of the filling and pressure generation unit, which is characterized by the smaller diameter of the secondary cylinder, does not contribute to the rapid filling of the fluid line under test with the test fluid in the relevant operating mode; rather, it is hydraulically short-circuited in this operating mode, i.e., it pumps from the

[0024] The test fluid drawn into the reservoir is returned to it without pressure. This design requires a simpler pressure control on the secondary side than the previously described design.

[0025] From a design perspective, it is particularly advantageous if, according to yet another preferred embodiment of the present invention, the base body of the filling and pressure generation unit comprises a cylinder tube and two end pieces closing it. This further development of the invention is characterized by a particularly low structural complexity. According to particularly preferred, structurally advantageous embodiments, the primary air control unit is attached, either separately or optionally cumulatively, to one of the two end pieces, with a primary air channel extending between the two end pieces, and / or a pneumatically switchable primary air control unit comprising a 5 / 2-way valve is provided, with an end-position pilot valve arranged on each of the two end pieces and a control air channel extending between the two end pieces, and / or

[0026] - a T-piece is attached to each of the head pieces, on which a suction check valve and a pressure check valve are provided.

[0027] The present invention will now be explained in more detail with reference to four preferred embodiments illustrated in the drawing.

[0028] Fig. 1 shows a first embodiment of the invention based on a pneumatic / hydraulic circuit diagram,

[0029] Fig. 2 shows a preferred design embodiment of the device used in the test rig according to Fig. 1.

[0030] air hydraulic pressure intensifier ,

[0031] Fig. 3 shows a second embodiment of the invention based on a pneumatic / hydraulic circuit diagram,

[0032] Fig. 4 shows a third embodiment of the invention based on a pneumatic / hydraulic circuit diagram and

[0033] Fig. 5 shows a fourth embodiment of the invention based on a pneumatic / hydraulic circuit diagram.

[0034] The test rig illustrated in Fig. 1 of the drawing for a test specimen 2 designed in the form of a fluid line or a fluid container 1 comprises a

[0035] Test fluid reservoir 3, a filling and pressure generation unit 4 communicating with it for the test fluid, a closure head 6 designed for tight interaction with an end fitting 5 of the test specimen 2 with a flow channel arrangement 7 connected to the filling and pressure generation unit 4 for the test fluid, and a measuring arrangement 8. The filling and pressure generation unit 4 is designed to be connected to a standard compressed air supply 9, which serves as the energy source for printing the

[0036] Test fluid - compressed air of, for example, 7 bar is provided.

[0037] The filling and pressure generation unit 4 comprises, as its core component, an air-hydraulic pressure booster 10. This booster has a base body 11 with a primary cylinder 12 and two secondary cylinders 13 arranged on opposite sides of the primary cylinder 12, oriented parallel to the primary cylinder 12, preferably even coaxially. A primary piston 14 is guided in the primary cylinder 12 in a sealing manner and is oscillatable along a working axis X. Two secondary pistons 15 are rigidly connected to the primary piston 14 on opposite sides of it. Each of these plunges into one of the two secondary cylinders 13. Thus, the primary piston 14 and the two secondary pistons 15 oscillate together as a piston unit 16 in the base body 11 of the filling and pressure generation unit 4. This is schematically illustrated in Fig.1. A constructed embodiment of the two secondary pistons 15, each comprising a piston rod 17 and a piston head 18 arranged at its end, wherein the piston rod 17 is sealed against the base body 11 of the filling and pressure generation unit 4 by means of a ring seal arrangement 19, although this is not mandatory. Alternatively, each of the two secondary pistons 15 could not be constructed separately, but rather formed in one piece with the diameter of the respective piston head 18 (see Fig. 2).

[0038] The primary piston 14, together with the primary cylinder 12, defines two counter-rotating, volume-variable primary working chambers 21, each of which can be pressurized via a compressed air connection 20. And each of the two secondary pistons 15, together with the respective assigned secondary cylinder 13, defines a secondary working chamber 22.

[0039] The oscillating movement of the piston unit 16 is forced by an alternating application of compressed air to the two primary working chambers 21. For this purpose, their compressed air connections 20 are connected to a primary air control unit 23 supplied by the compressed air supply 9.

[0040] This includes two pneumatic end position pilot valves 24, which can be actuated by the primary piston 14 via the switching pins 49 projecting into the primary working chambers 21, and a reversing valve 25 controlled by these in the form of a bistable 5 / 2-way valve 26.

[0041] Each of the two secondary working chambers 22 is connected to a suction check valve 27 which is fluidically connected to the test fluid reservoir 3 and to a pressure check valve 28. Thus, during each complete stroke cycle of the piston unit 16, test fluid is successively pumped from the test fluid reservoir 3 to the pressure side of the respective secondary cylinder 13, i.e., downstream of the associated pressure check valve 28, first in one secondary cylinder 13 and then in the other secondary cylinder 13. To the extent described above, the filling and pressure generation unit 4 used in the embodiment shown in Fig. 1 corresponds to the well-known prior art for double-acting air-hydraulic pressure intensifiers (see, for example, US 2,826,149 A, US 3,540,348 A, US 3,811,795 A, CN 108644084 A, CN 108488111 A, WO 2011 / 051661 A1), so that no further explanation is necessary.

[0042] The particularly important feature of the test rig according to Fig. 1 is that the two secondary cylinders 13 – and consequently also the piston heads 18 of the two secondary pistons 15 – have different diameters. The diameter of the first secondary cylinder 13 shown on the left in the drawing is significantly larger than the diameter of the second secondary cylinder 13 shown on the right in the drawing. Consequently, the two sides have considerably different delivery volumes per stroke of the piston unit 16; and – in an inverter fashion – the two pressure intensifiers also differ from the primary side to the respective secondary side of the pressure intensifier.

[0043] Furthermore, for the test rig illustrated in Fig. 1, it is significant that the flow-related connection of the two pressure check valves 28 with the flow channel arrangement 7 of the sealing head 6 can be switched into several different operating states. For this purpose, two control valves 29 in the form of 2 / 2-way valves 30 are provided, each assigned to one of the two secondary cylinders 13. These control valves are each connected to a bypass line 31, which branches off from the connecting line 32 linking the assigned pressure check valve 28 with the flow channel arrangement 7, specifically upstream of a further downstream check valve 33 provided in said connecting line 32.

[0044] The two control valves 29 are each switchable between a neutral position, in which the test fluid pumped by the associated pressure check valve 28 is returned to the test fluid reservoir 3 via the bypass line 31, and a closed position that prevents the return flow. For reasons of increased operational reliability, the control valves 29 are designed here as normally open valves. Depending on the switching position of the two control valves 29, neither of the two secondary sides of the air-hydraulic pressure booster 10 supplies test fluid to the test specimen 2 (zero position of both control valves 29), one of the two secondary sides supplies test fluid to the test specimen 2 (zero position of one control valve 29 and closed position of the other control valve 29), or both secondary sides of the air-hydraulic pressure booster 10 supply test fluid to the test specimen 2 (closed position of both control valves 29).

[0045] It should be noted as a precaution that Fig. 1 does not show a device for venting the test specimen 2 and draining the

[0046] The test fluid is drawn from this after the pressure test has been completed. Such a device, which can be implemented in any known manner, is not the subject of the present invention.

[0047] According to Fig. 2, the base body 11 of the air-hydraulic pressure intensifier 10, as it can be used as part of the filling and pressure generation unit 4 of the test rig according to Fig. 1, comprises a cylinder tube 34 and two end pieces 35 closing it. Each end piece 35 comprises a base 36, which is sealed to the cylinder tube 34 by means of a seal 37, and an insert 38 in the base 36, in which the respective secondary cylinder 13 is located. The two end pieces 38 are each sealed by a ring seal 50 in a cylindrical bore of the base 36 and fixed there by means of a nut 51. The two bases 36 are clamped against each other by means of four tie rods 39.Each of the two inserts 38 – each in the form of a T-piece – has two threaded bores 40 communicating with the respective secondary cylinder 13. These bores serve to accommodate the associated suction check valve 27 and the associated pressure check valve 28. Figure 2 also shows in detail the ring seal assemblies 19, which serve to seal the two primary working chambers 21 and slide on the outer surface of the secondary pistons 15, secured by means of the union nuts 52. The assembly of the piston unit 16 is also shown, in which the two secondary pistons 15 are screwed together, clamping the (disc-shaped) primary piston 14 between them.

[0048] In terms of construction, the primary air control unit 23 (see above) is preferably attached as a corresponding control block 41 to the base 36 of one of the two headpieces 35. A primary air duct 42 extends between the two headpieces, through which – according to the

[0049] Air control is provided by the primary air control unit 23 – air flows to the other headpiece 35, i.e., the headpiece 35 (shown above in Fig. 2) without the primary air control unit 23, and from there into the associated primary working chamber 21. Furthermore, a control air channel 43 extends between the two headpieces 35, through which the two end-position pilot valves 24, arranged on the bases 36 of the two headpieces 35, are pneumatically connected to each other.

[0050] In the second embodiment illustrated in Fig. 3 - only in the scope affected by modifications compared to Fig. 1 - it is not possible to actuate the two control valves 29 independently of each other; rather, they are coupled via a switching bridge 44 in such a way that a total of two operating positions are possible, whereby one of the two control valves 29 is always open (zero position), while the other is closed (lock position).

[0051] A pneumatic actuator 45 is provided for actuating the switching bridge 44. Without its activation, the control valve arrangement is in the operating position in which the filling and pressure generation unit 10 – for filling the test specimen 2 – delivers a comparatively large quantity of test fluid at a comparatively low delivery pressure, whereas when the pneumatic actuator 45 is activated, it switches to the second operating position in which the filling and pressure generation unit 10 – for pressure testing the test specimen 2 – delivers a comparatively small quantity of test fluid at a comparatively high delivery pressure.

[0052] Figure 3 also shows a second sealing head 46, which closes the test specimen 2 at a second position. To accelerate the filling of the test specimen 2, it can be vented at the beginning of the test via this second sealing head 46 and the downstream purge valve 47.

[0053] In the further embodiment illustrated in Fig. 4, a safety valve 48 is provided as an additional safety feature. This valve is actuated by a hood of the test stand in such a way that it only assumes its closed position when the hood is closed, in which pressure build-up in the test specimen 2 is possible. When the hood is open, however, the safety valve 48 is open, so that pressure build-up in the test specimen 2 is impossible. The filling and pressure generation unit 10 delivers

[0054] The test fluid instead returns to the system via the open safety valve 48.

[0055] Test fluid reservoir 3.

[0056] The embodiment shown in Fig. 5 shows the modification of the embodiment shown in Fig. 1 by implementing both a second closure head 46 with a downstream flushing valve 47 and a safety valve 48 actuated by the hood of the test stand, as explained above.

Claims

Claims 1. Test stand for fluid lines or reservoirs (1), in particular for hydraulic lines, comprising a test fluid reservoir (3) and a sealing head (6) designed for tight interaction with an end fitting (5) of the fluid line or fluid reservoir to be tested, with a flow channel arrangement (7) for test fluid, to which a [connection] is connected. Test fluid reservoir (3) communicating filling and pressure generation unit (4) for the test fluid is connected, with the following features: - the filling and pressure generation unit (4) includes an air-hydraulic pressure booster (10); - in a base body ( 11 ) of the air-hydraulic pressure booster ( 10) a primary cylinder ( 12 ) is provided in which a primary piston ( 14 ) is guided oscillatively along a working axis (X), which defines with the primary cylinder ( 12 ) two counter-rotating volume-variable primary working chambers (21 ) each which can be actuated via a compressed air connection (20), wherein the two compressed air connections (20) are connected to a primary air control unit (23); - in the base body ( 11 ) two secondary cylinders ( 13 ) oriented parallel to the working axis (X) and arranged on different sides with respect to the primary piston ( 14 ) are provided, into which secondary pistons ( 15 ) rigidly connected to the primary piston ( 14 ) immerse, wherein each secondary cylinder ( 13 ) and the associated secondary piston ( 15 ) define a secondary working chamber (22 ); - each of the secondary work spaces (22 ) is connected to a flow-engineered connection with the test fluid reservoir (3) connected suction check valve (27) and with a pressure check valve (28) in connection; - the two secondary cylinders ( 13) have different diameters ; - the flow-technical connection of the two pressure check valves (28 ) with the flow channel arrangement (7 ) of the closure head ( 6) can be switched into at least two different operating states, wherein in at least one of the operating states the flow channel arrangement (7 ) of the closure head ( 6) is supplied only from one of the two secondary working chambers (22 ).

2. Test rig according to claim 1, characterized in that the flow channel arrangement (7) can be selectively connected to both pressure check valves (28) or only to one of the two pressure check valves (28) in terms of flow technology.

3. Test rig according to claim 2, characterized in that the flow channel arrangement (7) can be flow-technically connected either to both pressure check valves (28) or only to the pressure check valve (28) which is assigned to the secondary cylinder (13) with the smaller diameter.

4. Test rig according to claim 1, characterized in that the flow channel arrangement (7) can be flow-technically connected either to the pressure check valve (28) which is assigned to the secondary cylinder (13) with the larger diameter or to the pressure check valve (28) assigned to the secondary cylinder (13) with the smaller diameter.

5. Test rig according to one of claims 1 to 4, characterized in that the base body ( 11 ) of the air-hydraulic pressure booster ( 10) comprises a cylinder tube (34 ) and two end pieces (35) closing this at its end.

6. Test rig according to claim 5, characterized in that the primary air control unit (23) is attached to one of the two head pieces (35), wherein a primary air channel (42) extends between the two head pieces.

7. Test stand according to claim 6, characterized in that a pneumatically switchable primary air control unit (23) comprising a 5 / 2-way valve (26) is provided, wherein an end position pilot valve (24) is arranged on each of the two head pieces (35) and a control air channel (43) extends between the two head pieces (35).

8. Test stand according to one of claims 5 to 7, characterized in that an insert (38) designed as a T-piece is attached to each of the head pieces (35), on which a suction check valve (27) and a pressure check valve (28) are provided.

Images