WO1990014550A1

WO1990014550A1 - Device for refrigerating a pipeline

Info

Publication number: WO1990014550A1
Application number: PCT/EP1990/000796
Authority: WO
Inventors: Horst Bantin
Original assignee: Horst Bantin
Priority date: 1989-05-17
Filing date: 1990-05-17
Publication date: 1990-11-29
Also published as: DE3916025A1; AU5653590A; EP0425627A1; DE3916025C2

Abstract

A device for refrigerating a pipeline conveying a refrigerant comprises a hermetically sealed refrigerant circuit with a condenser (10) and a downstream choke element (20) connected to at least one pair of tongs (26; 26'). The jaws (28, 28'; 30, 30') of the tongs, when closed, form a tongs bit (40) in thermal connection with a pipe, and each jaw has a hollow body which functions as an evaporator as well as an inlet (32, 32'; 36, 36') and an outlet (34, 34'; 38, 38') for the refrigerant. The choke element consists of a thermostatic expansion valve (20) the sensor (64) of which measures the temperature of the refrigerant in the return line (68) leading from the tongs (26, 26') to the condenser (10).

Description

—4 -

Pipe freezer

Description

The invention relates to a pipe freezer for freezing a pipeline carrying freezable media upstream and / or downstream of a pipeline section to be separated, with a refrigerant circuit which is hermetically sealed from the environment and which has a condenser, a downstream throttle element and at least one connected to it Has pliers, the jaws of which, in the closed position, form a pliers mouth, which comes into thermal contact with a tube, each contain a hollow body acting as an evaporator and are provided with an inlet and an outlet for the refrigerant.

FP5ÄT7RI ΔTT In the case of repair or installation measures on pipes or lines, in particular on heating pipes which carry a freezable medium such as water, all that is necessary to avoid the need to shut down and empty the entire heating system is to use a pipe freezer of the type mentioned at the beginning the line is frozen at one or two points in front of and / or behind the pipe section to be processed. In this way, a solid ice plug forms at these points, which seals off the pipe section to be separated from the rest of the system. This is done by placing a sleeve, pliers or the like around these lines, into which refrigerant is introduced, evaporating there and removing the heat of vaporization required for this from the corresponding pipe section, as a result of which the desired ice plug is removed at this point forms in the tube as a closure.

In the past, devices were often used for this, e.g. B. are known from DE-GM 88 02 515, in which the sleeves or pliers are open to the tube and form a cavity therewith. The refrigerant is introduced into the cavity via a hose, comes into direct contact with the surface of the tube, evaporates there, extracts the necessary heat of vaporization from the enclosed tube section and emerges in the form of gases from a section provided for this purpose NEN outlet opening into the environment. The use of such tube freezers is problematic when using refrigerants which are harmful to health and the environment. In such a case

REPLACEMENT --E --- _-. i-- Ϊ_Ϊ. namely in particular persons who carry out repair work in closed rooms are exposed to an increased degree of poisoning. Since welding or soldering is often carried out on repair work on pipelines, the risk of thermal decomposition of released refrigerant vapors in welding or soldering flames is very high. The use of CFCs, a commercially available, inexpensive and ^(~ ^{^} comparatively effective refrigerant is completely excluded in der¬ like barley, since CFC be¬ kanntlich a cause for the destruction of the ozone-forming layer in the atmosphere.

For these reasons, tube freezers of the type mentioned at the outset have been developed, the main feature of which is a refrigerant circuit which is hermetically sealed from the environment. If sleeves or tongs are used in such tube freezers, which are open to form a cavity with the tube, an adequate seal of the sleeve or tongs to the outer wall of the tube must be present. However, a secure seal can only be achieved with great effort and is therefore not entirely unproblematic. Therefore, the use of a pair of pliers is more suitable, the jaws of which contain a completely closed cavity with an inner wall which can be brought into contact with the pipe, as described in DE-GM 87 15225. Although the heat transfer from the tube into the cavity is slightly worse than in the case of a pair of pliers with an open cavity because of the inner wall between them, this disadvantage can be caused on the one hand by

, ^"* _.. - _. a _- = —-» ___ .. • the use of particularly thermally conductive materials and, on the other hand, be balanced by the fact that, owing to the hermetically sealed refrigerant circuit, particularly effective refrigerants, which are also environmentally hazardous, can be used.

A capillary tube is used as a throttling device in this tube freezer to adjust the refrigerant mass flow, the tube length of each tube depending on the setting range of the thermostat used and the properties of the evaporator, compressor and condenser existing refrigerant circuit must be determined experimentally. That is, Because of the capillary tube length which has been determined once and cannot be changed thereafter, the cooling capacity remains fixed. The optimum evaporator charge can therefore only be achieved in a very specific operating state. This means that even after the desired freezing temperature has been reached, at which the temperature difference between the pipe and tongs is considerably lower than at the start of the cooling process and thus only a correspondingly low mass flow of the refrigerant is required at the outlet of the evaporator effective cavity in the tongs there is only superheated steam and there is no overfilling with danger for the compressor due to liquid hammer, the capillary tube length must be adjusted to this operating state. However, this means that at the beginning of the cooling process, when the temperature difference between the tube and the tongs is still very high, the cavity of the tongs acting as an evaporator is due to the relatively low mass flow

£ RSAT5 © ^ - f and thus underfilling occurring is poorly exploited. Because of these conditions, cooling down with the aid of the capillary tube control is possible only very slowly, as a result of which the overall capacity of the system is extremely limited, so that it becomes uneconomical, in particular for tubes with larger diameters, because of the extraordinarily long cooling times is out of the question.

It is therefore an object of the invention to further develop a tube freezer of the type mentioned at the outset such that considerably shorter freezing times are achieved and tubes of larger diameter can also be treated.

This object is achieved in that the throttle element is a thermostatic expansion valve, the sensor of which measures the temperature of the refrigerant in the return line leading from the tongs to the condenser.

In contrast to the capillary tube, the thermostatic expansion valve known per se, which is used according to the invention for a tube freezer, permits regulation. With this control, the overheating at the end of the evaporator is used as a control variable for controlling the expansion valve. With increasing overheating the valve opens for a larger mass flow of the refrigerant, with falling overheating it closes to limit the mass flow of the refrigerant. In this way, the hollow body acting as an evaporator in the tongs is optimally used because its heat exchange surface in every operating

E SATC ^ Ä F state the maximum possible amount of heat is exceeded and can thus flow away. Seen from the refrigerant side, this means that the entire available heat exchange surface must always be wetted by the evaporating refrigerant. With the help of the thermostatic expansion valve, the filling of the evaporator is now always controlled in such a way that, regardless of the prevailing temperature difference, which is very high at the beginning of cooling and relatively low after the desired freezing temperature has been reached, optimal filling of the evaporator is achieved without overfilling leading to the backflow of unevaporated refrigerant to the compressor. That is, due to the regulation of the refrigerant mass flow through the thermostatic expansion valve, only superheated steam is present in the return line leading from the tongs to the liquefier.

According to the invention, the capacity of the system is not determined by the physical conditions in the freezer state, but is designed independently of it so that a rapid cooling of pipes, even those with a large diameter, is possible. This is because the thermostatic expansion valve regulates the mass flow in such a way that it is greatest when there is a high temperature difference between the tongs and the pipe at the beginning of the cooling process and is reduced accordingly until the nominal freezing temperature is reached in the final state, since then the temperature difference limit is considerably lower and thus a correspondingly lower mass flow is only required. The temperature is correspondingly steep

, -_____ ^" - *. '- 1_ ^* curve at the beginning of the cooling process downwards, while the slope decreases more and more towards the final state; the temperature curve therefore has a hyperbolic course.

The cooling capacity of the tube freezer is preferably essentially determined by the amount of heat that can be dissipated via the tongs at the highest temperature difference, the width of the pincer mouth surrounding the tube being at least 0.9 times its diameter. This is because the pipe freezer according to the invention can be used particularly advantageously when the pliers jaws cover a pipe section over a surface area, the axial length of which is at least 0.9 times its outer diameter.

In a further embodiment of this embodiment, the expansion valve is arranged in the pliers. In this way, heat and pressure losses are avoided, which can occur in a line between the expansion valve and the pliers. Because in this development the evaporation takes place directly behind the expansion valve in the hollow bodies of the jaws.

However, expansion valves, which can continuously reduce their opening width to the closed position, are very expensive, since the construction is very complex and complicated. In contrast, expansion valves of this type which have only a limited control range are considerably cheaper, ie they do not have a minimum opening width If you want to use such inexpensive expansion valves in the pipe freezer according to the invention for cost reasons, the desired rapid cooling is still obtained, but in the final state the danger of overfilling the return line can occur , since the expansion valve in the lowest operating point of its control range still delivers more refrigerant mass flow than is required for the evaporation in the tongs. In order to avoid this, a further embodiment of the invention is characterized in that the evaporator is additionally formed from the supply line leading to the tongs, the minimum volume of which is determined, given the total volume of the cavities of the tongs jaws the refrigerant has essentially evaporated at the lowest operating point of the control range specified by the thermostatic expansion valve at the beginning of the return line. The feed line from the expansion valve to the tongs thus serves - with a low and correspondingly slow mass flow - as a "pre * evaporator or buffer, in which part of the refrigerant evaporates before the tongs so that it reaches the The outlet from the pliers is completely evaporated, which avoids the risk of overfilling and thus a liquid hammer in the compressor.As heat is extracted not only from the pipe but also from the environment, the refrigerant becomes a little bit from the expansion valve to the pliers This heat loss can, however, be accepted in view of the considerable cost savings in the expansion valve.

ERw «ι_ £ __3._U_ <Hi In a further advantageous embodiment of the invention, two pliers can be connected in parallel; >. be by connecting the inlet of the first jaw to a feed line, the outlet of the first jaw to the inlet of the second jaw and the outlet of the second jaw to the return line for each pair of pliers. Each pair of pliers is preferably connected to the thermostatic expansion valve via a separate feed line.

In an alternative embodiment, two pliers are connected in series, in that the inlet of the first jaw of the first pliers with the feed line, the outlet of the first jaw with the inlet of the second jaw of the first pliers, and the outlet of the second jaw of the first pliers with the inlet of the first jaw of the second pliers, the outlet of the first jaw is connected to the inlet of the second jaw of the second pliers and the outlet of the second jaw of the second pliers is connected to the return line.

The parallel connection has the advantage that the same evaporation temperature prevails in both tongs, but a total of four supply and return lines are required. In contrast, only one supply and one discharge line are connected to the pair of pliers in the series connection, which can be advantageous in some applications due to the limited space available. However, the evaporation temperature is then not the same in both tongs, but is somewhat higher in the tongs downstream, so that the freezing takes a little longer there.

TSBLA T Because of their flexibility, the feed and discharge lines should preferably consist of cold-resistant hoses, for example of cold-resistant rubber or of polyamide with a rubber cover.

It has been found that the thermostatic expansion valve should preferably be set to a temperature difference of 5 ° K.

In a further embodiment of the invention, a liquid separator is connected to the return line leading to the condenser. This is only an additional security measure to protect a compressor.

The invention is explained below with reference to the embodiments shown in the drawings. Show it:

Fig. 1 is a block diagram of the

Pipe freezer in a first embodiment;

2a, b a pair of pliers in an enlarged individual view, namely in side view (a) and top view (b);

Fig. 3 the connection of the two pliers to the

Pipe freezer in a second embodiment;

ERSA - t.- i. Fig. 4 is a diagram showing the operation of the expansion valve used in the first and second embodiment;

5 shows the connection of the two tongs to a third embodiment of a pipe freezer;

6 shows the connection of the two tongs to a fourth embodiment of the pipe freezer; and

Fig. 7 is a diagram showing the operation of the expansion valve used in the third and fourth embodiments.

In Fig. 1, a first embodiment of the tube freezer with the refrigerant circuit is shown schematically as a block diagram, which is hermetically sealed from the environment. A compressor 4 serves to compress and transport the refrigerant and is connected to a condenser 10 via an oil separator 6. The oil filtered out of the refrigerant by the oil separator 6 is returned to the compressor 4 via an oil return line 8. A fan 12 ensures improved heat dissipation from the condenser 10. The refrigerant is transported from the condenser 10 to a thermostatic expansion valve 20 via a collecting container 10, a dryer filter 16 and a sight glass 18. At the entrance to the thermostatic expansion valve 20, the refrigerant has a temperature of approximately + 28 ° C. and a pressure of approximately 13.31 kp / cm ² . The refrigerant is expanded by the expansion valve 20 to a pressure of approximately 1.66 kp / cm ² and reduced to a temperature of approximately -35'C. A T-connector 22 is connected to the expansion valve 20, from which two supply hoses 24, 24 "lead to two pliers 26, 26 '. The supply hoses 24, 24 * are preferably made of cold-resistant rubber or polyamide with rubber cover and have at least a length of 2m and an inner diameter of 7.9mm.

The structure of the pliers 26, 26 'in detail is shown in FIG. 2, the pliers 26 being shown. The main component of the pliers are two jaws 28, 30, which together form a pliers mouth 40 that can be placed on a tube. Each jaw 28, 30 contains a cavity of approximately 48 cm ³ , to each of which an inlet 32 and 36 and an outlet 34 and 38 lead. The jaws 28, 30 are articulated to one another via a connecting joint 42 which is provided with a spring (not shown) which generates a clamping pressure. Each jaw 28, 30 terminates in a handle 48, 49 protruding beyond the connecting joint 42. The pliers jaw 40 is formed by hollows 50, 51 formed in each jaw 28, 30. Half-shells (not shown) can be releasably inserted into each trough 50, 51 and can be exchanged in order to enable adaptations to different pipe diameters of a pipe to be repaired. For the connection of hoses, each inlet 32 and 36 and each outlet 34 and 38 is designed as a connecting piece.

1 shows both pliers 26, 26 'are connected in parallel. For this purpose, the pliers 26, 26 ' The associated supply hose 24 or 24 'is connected to the inlet 32 or 32' of the first jaw 28 or 28 '. The outlet 34 and 34 * of the first jaw 28 or 28 'is at each pliers 26, 26' to the inlet 36 or 36 'of the ⁱ ze s jaw 30 or 30' and the outlet 38 and 3 with a Return line 60 or 60 'connected.

The cavities in the pliers jaws 28, 28 ', 30, 30' act as evaporators, in which the refrigerant evaporates completely at a temperature of approximately -32 ° C., so that through the two return lines 60, 60 'only Steam is carried. Possibly. a portion of the refrigerant is already evaporating in the two supply hoses 24, 24 * in front of the pliers 26, 26 ', which will be described in more detail below.

From the pliers 26, 26 ', both return line hoses 60, 60' lead to a T-connector 62, which connects them to a single suction gas line 68. The return line hoses 60, 60 * can preferably consist of the same material as the line line hoses 24, 24 '. At the suction gas line 68, an expansion valve sensor 64 measures the temperature, which is transmitted as an electrical signal to the thermostatic expansion valve 20 via a sensor line 66. The thermostatic expansion valve is set to a temperature difference of 5 * K. In the suction line 68, the vaporous refrigerant has a Tempera¬ ture of about -30 ^β C and a pressure of about 2.03 kgf / cm ^2. A filling control connection 70 is connected to the common suction gas line 68. The suction gas Line 68 leads to a liquid separator 72, which is installed in the compressor 4 as an additional safeguard against liquid hammer. The refrigerant is then finally returned to the compressor 4 by the liquid separator 72.

Except for the pliers 26, 26 'and the hoses 24, 24' and 60, 60 'connected to them, all other parts are contained in the protective housing 80.

Instead of the parallel connection shown in FIG. 1, both pliers 26, 26 * can also be connected in series, as shown in FIG. 3. This embodiment differs from the one described above in that in total only one supply hose 24 and one return hose 60 are connected to the pair of pliers 26, 26 ', so that the T-connectors 22 and 62 required in the first embodiment are omitted. With each pair of pliers 26, 26 ', the outlet 34 or 34' of the first jaw 28 or 28 'is connected to the inlet 36 or 36' of the second jaw 30 or 30 '. The outlet 38 of the second jaw 30 of the first tong 26 is connected via a connecting hose to the inlet 32 * of the first jaw 28 'of the second tong 26'. The outlet 38 'of the second jaw 30' of the second pliers 26 'is connected to the return hose 60, which is connected to the suction gas line 68 in the housing 80.

The two previously described embodiments are characterized in that both pliers 26, 26 'via a supply hose 24 or 24' to the thermostatic expansion valve 20 are connected. This arrangement is recommended when a thermostatic expansion valve 20 is used which has only a limited control range, ie cannot fall below a minimum opening width. In contrast to those valves which can infinitely reduce their opening width to the closed position, such expansion valves are simpler and considerably less expensive in their construction.

Such an expansion valve also regulates the coolant mass flow in such a way that it is greatest at a high temperature difference between tongs 26 and 26 'at the beginning of the cooling process and is reduced accordingly until the nominal freezing temperature on the pipe is reached. Thus, the temperature decreases rapidly at the beginning of the cooling process, while the slope of the temperature curve decreases more and more towards the final state. Accordingly, the thermostatic expansion valve 20 regulates the refrigerant mass flow, as the diagram of FIG. 4 shows schematically. At the start of the cooling process, the temperature difference is very high, e.g. B. 105 * K, if the liquid medium in the tube at the point enclosed by the pincer jaw 40 is +70 ^β C and should be cooled down to -35 ^β C. Then the greatest possible refrigerant mass flow is required so that the expansion valve 20 is fully open. In contrast, the temperature difference in the area of the nominal freezing temperature is very small and is only a few * K, since it is only caused by the heat losses. Accordingly, only a very low refrigerant mass flow is required.

- However, the minimum opening width of the above-mentioned thermostatic expansion valve 20 of a simple design is above the opening width required in the final state in the range of the freezing temperature, so that in relation to the prevailing low temperature difference, more refrigerant mass flow is always delivered than for the evaporation is required in the tongs when the freezing temperature is reached. Thus, the risk of overfilling the

Return hose 60 or 60 * occur. However, this is avoided by the fact that the evaporator is additionally formed from the supply hose 24 or 24 'leading to the pliers 26, 26'. The supply hose 24 or 24 'thus serves as a "pre" evaporator or buffer, in which part of the refrigerant evaporates even before the tongs 26, 26' - and the more the temperature increases, the more so in the tube approaches the evaporation temperature in tongs 26, 26 * and the temperature difference between the tube and the tongs 26, 26 'is reduced. This ensures that the refrigerant is completely evaporated when it enters the return hose 60 or 60 ', thereby avoiding the risk of overfilling and thus of a liquid hammer in the compressor 4.

This process is clearly shown in the diagram of FIG. 4, the expansion valve being closed to its minimum opening width at point X and thus delivering a constant minimum mass flow even at lower temperatures or lower temperature differences (curve A) , even if only a lower mass flow corresponding to the dashed curve B is required. The stronger the - 7 -

The difference between the curves A and B (hatched area C), the more refrigerant is evaporated in the supply hose 24 or 24 '.

If, on the other hand, the costs are irrelevant, a thermostatic expansion valve can also be used for the tube freezer according to the invention, which can continuously reduce its opening width up to the closed position. Then, in order to avoid heat losses, it is advisable to arrange the expansion valve directly on the pliers 26 or 26 '. Such an embodiment is shown in FIGS. 5 and 6.

The embodiment according to FIG. 5 thus differs from the embodiment according to FIG. 1 in that instead of an expansion valve in front of the T-connector 22, a thermostatic expansion valve 20 'and 20 "is now arranged on each pair of pliers 26, 26' directly at the inlet 32 or 32 'of the first jaw 28 or 28 *. The associated expansion valve sensor 64' or 64 "is arranged at the outlet 38 or 38 * of the second jaw 30 or 30 ' net. Otherwise, the design of this embodiment is the same as that of the tube freezer shown in FIG. 1.

FIG. 6 shows an embodiment which differs from the embodiment according to FIG. 3 distinguishes in that the thermostatic expansion valve 20 'at the inlet 32 of the first jaw 28 of the first tong 26 and the associated expansion valve sensor 64' at the outlet 38 * of the second jaw 30 'of the second tong

ge 26 'is arranged. Otherwise, the structure is the same as in the embodiment according to FIG. 3.

FIG. 7 shows the characteristic curve of the control range of the expansion valve used in the embodiments according to FIGS. 5 and 6. From this it can be seen that this thermostatic expansion valve is a valve with "ideal" control behavior. This valve differs from the valve used in the embodiment according to FIGS. 1 and 3 in that it also regulates the mass flow in the lower temperature range in accordance with the dashed curve B of FIG. 4.

SPARE BLADEΓ

Claims

Expectations

1. Pipe freezer for freezing a pipeline carrying freezable media in front of and / or behind a pipe section to be separated, with a refrigerant circuit that is hermetically sealed from the environment and that contains a condenser r ^~~ (10), a downstream throttle element (20) and has at least one pliers (26; 26 ') connected to it, the jaws (28, 28 *; 30, 30') of which in the closed position form a pliers mouth (40) which comes into thermal conduction with a pipe, one each Contain as an evaporator hollow body and are provided with an inlet (32, 32 '; 36, 36') and an outlet (34, 34 '; 38, 38') for the refrigerant, characterized in that the throttle element is a thermostatic Expansion valve (20), the sensor (64) of which measures the temperature of the refrigerant in the return line (68) leading from the tongs (26; 26 ') to the condenser (10).

2. Pipe freezer according to claim 1, characterized in that the cooling capacity of the pipe freezer is essentially determined by the amount of heat that can be dissipated at the highest temperature difference via the pliers (26, 26 '), the width of the pipe enclosing Forceps jaw (40) is at least 0.9 times its diameter.

ER8ATZ3LATT

3. Pipe freezer according to claim 2, characterized in that the expansion valve (20) in the tongs (26, 26 ') is arranged.

4. Pipe freezer according to Claim 1 or 2, characterized in that the evaporator is additionally formed from the supply line (24, 24 ') leading to the tongs (26, 26'), the minimum volume r of which for a given total volume of the cavities the pliers jaws (28, 28 '; 30, 30') then determine that the refrigerant in the lowest working point of the control range specified by the thermostatic expansion valve (20) at the beginning of the return line (60, 60 ') essentially evaporated.

5. Pipe freezer according to one of claims 1 to 4, characterized in that two pliers (26; 26 ') are connected in parallel by the inlet (32; 32') of the first jaw (28 ; 28 ') with a feed line (24; 24'), the outlet (34; 34 ') of the first jaw (28; 28') with the inlet (36; 36 ') of the second jaw (30; 30') and the outlet (38; 38 ') of the second jaw (30; 30') is connected to the return line (60; 60 ').

6. Pipe freezer according to claim 4 and 5, characterized in that each pair of tongs (26, 26 ') is connected via a separate feed line (24, 24') to the thermostatic expansion valve (20).

7. Pipe freezer according to one of claims 1 to 4, characterized in that two tongs (26, 26 ')

- RÄZBLÄΓT are connected in series by the inlet (32) of the first jaw (28) of the first pliers (26) with the feed line (24), the outlet (34) of the first jaw (28) with the inlet (36) of the second jaw (30) of the first pliers (26), the outlet (38) of the second jaw (30) of the first pliers (26) with the inlet (32 *) of the first jaw (28 *) of the second pliers (26 *), the outlet (34 ') of the first jaw (28') with the inlet (36 ') of the second jaw (30') of the second pliers (26 ') and the outlet (38') of the second jaw ( 30 ') of the second pliers (26 *) is connected to the return line (60).

8. Pipe freezer according to one of claims 1 to 7, characterized in that the supply and discharge lines (24, 24 '; 60, 60') consist of cold-resistant hoses.

9. Pipe freezer according to claim 8, dadurc characterized in that the hoses consist of cold-resistant-rubber.

10. Pipe freezer according to claim 8, characterized in that the hoses are made of polyamide with a rubber cover.

11. Pipe freezer according to claim 4, 6 and 10, characterized in that the supply line forming hoses (24, 24 ') have a diameter of at least 7.9 mm and a length of at least 2 m and the total volume of the cavities in the jaws of the two pliers is 8cm3.

12. Pipe freezer according to one of claims 1 to 11, characterized in that the thermostatic expansion valve (20) is set to a temperature difference of 5 ° K.

13. Pipe freezer according to one of claims 1 to 12, characterized in that a liquid separator (72) is connected to the return line (68) leading to the condenser (10).