PIPE FREEZING DEVICE

Abstract: A pipe freezing device comprises a compressor 1, condenser 3 and an expansion chamber 9. Refrigerant is pumped by the compressor 1 through the condenser 3 to the expansion chamber 9 via a capillary 8. The refrigerant entering the chamber 9 expands, cooling the walls of the chamber, and is pumped back to the compressor through return pipe 10. The expansion chamber is attached to a pipe, e.g. by clamping, to freeze the contents of the pipe.

Description: PIPE FREEZING DEVICE The present invention relates to pipe freezing devices. Such devices are used for freezing the fluid content of a pipe upstream of, or on both sides of a section which is being worked, so that the pipework does not have to be drained before work begins. More particularly, the invention relates to a portable, pipe freezing device. The commonly used method of freezing the pipe contents is to feed a coolant gas into a collar surrounding the pipe, the gas being allowed to escape to the atmosphere; a system of this type is described in GB 1211960. A major drawback of this system is the wastage of coolant gas, requiring the purchase and transport of large cylinders of the gas. Also if a cylinder is only nearly empty it is necessary to discard it and obtain a replacement before beginning a long job. GB 1199188 discloses a system in which a reservoir of liquid is cooled by a refrigerating apparatus, and the cooled liquid is fed through a jacket on the pipe, thus avoiding the loss of coolant. However this system is bulky, requiring both a refrigerating apparatus and a liquid reservoir. The present a notion provides a pipe freezing device wherein refriger-äntsgas is recirculated through an eXpansion chamber which is adapted to be attached to a pipe in a thermally conducting manner. Preferably the device includes at least two such chambers such that the chambers can be connected to a pipe either side of a section tot be worked on. Very preferably coolant is pumped to the expansion chamber through a capillary tube, preferably of polytetrafluoroethylene. The capillary tube preferably extends from a condenser to the expansion chamber and is preferably enclosed for substantially all its length in a larger diameter outer tube which is used for the return of expanded refrigerant from the expansion chamber, thus protecting the capillary tube. Preferably the device includes a portable compressor, a dryer and a condenser, the expansion chamber inlet being connected to the condenser bottom and the outlet being connected to the compressor suction side by a flexible pipe. The compressor pumps refrigerant vapour into the condenser. The refrigerant is compressed and condenses, heat is extracted from the condenser, preferably by a motorised fan. The condensed liquid refrigerant then flows into a dryer and then into a liquid tube which is connected to the inlet side of the expansion chamber or freezer block. The refrigerant on entering the chamber as liquid evaporates rapidly removing heat from the surrounding area until all the liquid has evaporated into vapour. The vapour then flows through the chamber outlet to the low pressure suction line or return line to the compressor. The vapour is drawn by suction into the compressor low side through a suction or return valve, is then compressed into the condenser and continues to be recycled continuously until the compressor is switched off. Preferably the expansion chamber comprises two closed cylinders arranged substantially parallel and opposite to one another, their volumes being connected at a first end by a tube of smaller cross-sectional area. Where the refrigerant is fed to the expansion chamber through a long capillary tube the tube preferably enters the expansion chamber at the second end of one of the cylindrical bores and passes through the connecting bore to deliver refrigerant at the second end of the other bore. The chamber outlet to the return tube is preferably at the inlet for the capillary tube, hence the expanded refrigerant will pass back through the chambers and connecting bore. In another arrangement, the capillary and return tube are connected to different chambers. The capillary need not extend all the way from the condenser to the expansion chamber. The function of the capillary is to restrict the flow of the refrigerant so that it condenses and is fed as liquid into the expansion chamber. Hence the refrigerant may be fed in a large bore pipe to the expansion chamber, a capillary being provided at the chamber inlet or in the chamber. Such a capillary may be formed in a number of ways. Preferred, are the use of an orifice or jet of small diameter at the chamber inlet, a ball urged against a seat by a spring, a capillary formed by a threaded screw in a short cylindrical bore, the peaks of the thread abutting the bore wall to form a compact helical capillary therebetween, or a length capillary extending within the expansion chamber. For the capillary to be effective in ensuring that the refrigerant is sufficiently condensed before entering the chamber it must be of a sufficient length, however the chamber must be of limited size to ensure that it can be connected to pipes where there is limited access. Preferably the expansion chamber is connected to a pipe to be frozen by means of a saddle adapted to fit snugly on the pipe. A set of connecting members may be provided, each to fit a pipe of a particular diameter, such as 28, 22 and 15 mm diameter copper pipes, and iron or lead pipes, and adapted to fit snugly inside the saddle of the chamber. Preferably the connecting members and the chamber are formed of thermally conducting material such as copper or aluminium. Fig. 1 is a schematic view of a pipe freezing device according to the invention, showing an expansion chamber in cross-section; Fig. 2 is a perspective view of the expansion chamber of Fig. 1; Fig. 3 is a perspective view of a saddle for use with the chamber of Figs. 1 and 2; Fig. 4 is a perspective view of another form of chamber. Fig. 1 shows the constituent parts of a preferred embodiment of the invention. The parts are not drawn to exact scale, the expansion chamber in particular being shown oversize. A compressor 1 is mounted on a base 2. A condenser 3 is formed from a long sinuous pipe 4 having cooling fins 5 attached to it in known manner and is fed with refrigerant from the compressor 1. A fan 6, powered by an electric motor, draws or blows air over the condenser 3 to cool it. Cooled refrigerant is fed through a filter and dryer 7 to a pair of capillary tubes 8a, 8b. In the described embodiment, the capillary tubes 8a,8b each comprise a copper capillary, internal diameter about .026 inches (.7 mm) and length 7 metres which is coiled and stored adjacent the compressor, passing into the return tubes 10a, lOb adjacent the compressor, the capillary tubes being brazed to the metallic return tube on the compressor to form a leaktight seal. Thereafter the capillary, and return, tubes are formed of flexible material, being fixed to the metal portions by clips, not shown. The flexible capillary tube is preferably of plastics material, such as polytetrafluoroethylene, having an internal diameter about 1.25 mm. The thick walled return tubes loa, lOb protect the plastics capillary tubes. The pair of metallic runs of the capillary tubes, between the filter/dryer and compressor may be replaced by a single capillary, being divided to feed into flexible capillary tubes leading to the expansion chambers. The long metallic capillary tube portion serves to restrict the flow of condensed refrigerant. The restricted flow being maintained in the flexible capillary tube portions to avoid premature evaporation of the refrigerant. The capillary tubes 8a,8b feed the cooled, condensed refrigerant to respective expansion chambers 9, only one is shown in Fig. 1. The refrigerant escapes from the capillary tubes in the expansion chambers and is sucked back into the compressor 1 along return tubes 10a,10b. The operation and structure of the expansion chambers 9 will be described in detail hereinafter. Also shown in Fig. 1 is a temperature control switch 11, in the power supply line 12 to the compressor 1. The switch controls the temperature at the expansion chambers 9 by monitoring rise and fall in the pressure of the refrigerant, which is relative to temperature (e.g. cut out or turn off the compressor 1 when refrigerant pressure is Op.s.i. (-210F) and turn back on at a pressure of 0 + 10 p.s.i. (OOF). A by-pass switch, to by-pass switch 11, is provided to allow the compressor to run continuously to reach very low temperatures. Figs. 2 and 3, show a preferred form of the expansion chamber 9. The chamber is preferably machined from a rolled aluminium block. Two parallel cylindrical bores 14,15 extend from an end face 16 of a parallelepipedal block 17. The bores are typically 20mm in diameter and about 60 mm long. The bores are closed at one end 18 by the other end face 19 of the block 17. A substantially semi-cylindrical groove 20 is formed in the end face. A similar groove 21 is formed in a top face 22 of the block. The grooves are sized to receive a pipe to be frozen, for example they may have a radius of curvature of 14mm.A number of chambers 9, having different size grooves may be provided However it is preferred that the grooves 20,21 are arranged to receive saddles 23 (Fig. 4) which have an inner curvature for receiving a pipe of particular diameter, e.g. of diameter 15mm and an outer curvature to fit snugly into grooves 20, 21. The collars may be held in position by a screw through a central hole 23a, screwed into block 17. As seen in Fig. 3, the open end of one bore 15 is closed by a blanking plug 43, which is preferably screwed into the bore to allow removal for inspection The cross bore 24 joining the closed ends 18 of the bores 14,15 is formed by drilling through a side wall 25. The bore through the wall is closed by a plug 26, which again may be screwed in position to allow removal. The open end of the bore 14 is closed by a member 27 which is screwed into the end of the bore 14. Member 27 has a through hole for the passage of the capillary tube 8a,8b, and a corrugated projection 28 about which the return pipe 10a is clamped by a clamp (not-shown). The capillary tube 8a extends along the bore 14, through the cross bore 18 and back towards the blanking plug 43. Refrigerant is pumped through the capillary tube 8a to flow out of the end 29 of the tube. The refrigerant then passes back through the bores to return tube lOa. Cooling the metal expansion chamber as it expands and contacts the walls of the bores. In use the expansion chamber, with an appropriate adapter 23 is clamped to a pipe to be frozen. By providing the grooves 20, 21 in the positions shown the expansion chamber 9 can be readily fitted to pipes in most locations. The end groove 20 is particularly suitable where there is a run of several closely spaced parallel pipes. The expansion chamber may be held on the pipe by a clamp. It is preferred that the grooves 20, 21 subtend an angle of 0 slightly less than 1800. However the collars 23 and or grooves 20,21 may subtend an angle slightly greater than 1800, to form a snap fit onto a pipe. It will be appreciated that a single bore may be provided in the block 17, however the configuration with two, or at least two, bores is considered to give improved thermal efficiency. The bores are preferably cylindrical but other shapes may be utilised. The fittings 23,26,27 are preferably of brass. Fig. 5 shows another form of expansion chamber, formed from a pair of cylinders 30,31 closed at one end and joined by a cross-pipe 32. The other ends of the cylinders receive respectively refrigerant inlet and return pipes 33,34, a capillary device being provided at the inlet 35. The figure shows a collar arrangement 36 which is slidable onto the cylinders and has a saddle 37 for attachment to a pipe. This embodiment may advantageousw be formed from copper tubing. The compressor may be of 6 hp low back pressure, and the refrigerant dichlorodifluoromethane. The flexible tubes connecting the expansion chambers are preferably of about lm to 2m in length, but other lengths may be used. The compressor and condenser are preferably mound in a portable box and run from mains electricity. Battery operation may be allowed for. Advantageously, the condenser is at one end of the box, with the fan at the other end, which is apertured for the flow of air. The compressor and filter are located between these units so that cooling air is drawn over all the units by the fan. The expansion chambers and connecting pipes 8,10 may be stored in a tray above the compressor. The condenser may be in the form of a skin condenser i.e. a thin chamber forming the skin of the portable box. One or more surfaces of the expansion chamber may be covered with an insulating material to facilitate handli# of the chamber whilst it is cold. The channels 10,21 and saddles 23 may be sized to fit larger outer diameter pipes, such as iron and lead pipes.

Claims: CLAIMS: 1. A pipe freezing device characterised in that refrigerant is recirculated through an expansion chamber 9 which is adapted to be attached to a pipe in a thermally conducting manner. 2. A device as claimed in claim 1, characterised in that the device further comprises a compressor 1 and a condenser 3, the compressor 1 pumping refrigerant from the expansion chamber 9 to the condenser 3 where the refrigerant is cooled, and from the condenser 3 back to the expansion chamber 9, the expansion chamber being connected to the compressor and condenser by means of elongate flexible tubes 8,10. 3. A device as claimed in claim 2, wherein refrigerant is fed from the condenser 3 to the expansion chamber 9 through a capillary 8 which extends substantially the whole distance from the condenser 1 to the expansion chamber 9. 4. A device as claimed in claim 1,2 or 3, characterised in that the expansion chamber comprises an elongate chamber 14,15 having an outlet 27 at one end thereof and refrigerant is released into said chamber at an end 29,23 distal of said outlet. 5.' A device as claimed in claim 4, characterised in that refrigerant is fed into the elongate chamber 14,15 through a capillary 8 which enters the chamber via the outlet. 6. A device as claimed in claim 5, characterised in that the capillary 8 is enclosed in a return pipe 10 feeding refrigerant from the expansion chamber 9 to the compressor 1. 7. A device as claimed in any one of claims 1 to 6, characterised in that the expansion chamber 9 comprises a pair of substantially parallel elongate bores 14,15 closed at one end and having their volumes connected at the one end, the chamber outlet being located at the other end of one of the bores. 8. A device as claimed in claim 8, characterised in that a first channel 21 is provides substantially parallel to the bores 14,15 and a second channel 20 is provided transverse to the first channel and across the closed ends of the bores 14,15, said channels having a cross-section suitable for receiving a pipe therein. 9. A device as claimed in any one of claims 1 to 7, characterised in that the expansion chamber 9 is provided with a channel 20,21 having an arcuate crosssection. 10. A device as claimed in claim 9, characterised in that saddles are provided for fitting into said channel and having a cross-section for receiving a pipe of standard diameter such as 15, 22, or 28 mm.

Inventors: HALLETT, RONALD
Applicants: HALLETT, RONALD
Application year: 1984
Main classification: F16L55
IPC codes: F25D15, F25B41, F16L55, F25B5