Pipe freezer

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/132,758 filed on May 6, 1999.

FIELD OF THE INVENTION

The present invention relates to an apparatus for freezing a plug of frozen liquid in a liquid-filled pipe, to plug said pipe at a point where there is no conventional valve, so that pipe repairs can be performed downstream of the plug.

BACKGROUND ART

PIPE FREEZERS USING EXPENDABLE REFRIGERANTS

A pipe freezer works by removing heat quickly enough from the liquid within a section of pipe that an ice plug forms in that section of pipe, thus effectively preventing the flow of liquid through that section of pipe. This ice plug acts as a temporary valve. When the ice plug is properly maintained (kept frozen), repairs can be performed on the pipe in the vicinity of the ice plug without the need to drain the piping system.

TWO PRIMARY METHODS OF FREEZING PIPES

1. Expendable refrigerants sprayed directly onto the pipe and vented to the atmosphere.

2. Compression cycle refrigeration, which circulates the same refrigerant in a closed loop as a refrigerator does.

1. Expendable refrigerants: These are the traditional refrigerants for freezing the contents (in a small section of pipe 5.08 cm-25.4 cm (2 in-10 in) in length) within plumbing piping or other fluid carrying conduits with a liquid that will freeze within the temperature range of the refrigerant being used.

The three more commonly used expendable refrigerants are listed below with their refrigerant number and boiling point at sea level (14.7 PSIA).

1. Liquid Carbon Dioxide: R744, −109 F. (−78 C)

2. Liquid Nitrogen: R728, −320 F. (−196 C)

3. Liquid Helium: R707, −425 F. (−269 C)

On pipes up to three 7.62 cm (three inches) of inner diameter the refrigerant of choice is carbon dioxide. There are five or more kits using carbon dioxide currently on the market in the US. Liquid nitrogen and liquid helium are not as available, are only packaged in large containers, and require additional safety training. There are companies that specialize in pipe freezing of pipes up to 152.4 cm (60 in) inside diameter. On pipes this large, liquid nitrogen or liquid helium would be used depending upon the application.

The current expendable refrigerant pipe freezing kits (for pipes up to 7.62 cm (3 in) ID) employ bags or collars that wrap around the pipe. The collars are hinged on one side and have a locking screw. The bags are wrapped around the pipe and tied on each end. Each type of kit has a spray head, which sprays the refrigerant over the pipe. A high-pressure hose delivers the liquid refrigerant to the spray heads from the tank.

As the liquid refrigerant is sprayed over the pipe within the bag or collar, dry ice is being formed due to the containment of the refrigerant (i.e., the refrigerant is not allowed to fully evaporate into the atmosphere). When enough dry ice is formed, the refrigerant valve on the tank is closed stopping the flow of refrigerant in to the bag or collar. To conserve refrigerant, heat is now removed from the pipe through the dry ice. The ability of the dry ice to remove heat from the pipe is much less than that of the denser liquid refrigerant. Throughout the process, the liquid refrigerant is turned on and off to conserve refrigerant, while depending on the dry ice, which was formed, to remove heat from the pipe.

Draw backs of free flow systems over Applicant's Multi-Cavity Adapter /Cartridge Evaporator

1. Requires longer freeze times.

2. Consumes more refrigerant

3. Cannot control vented gas location

4. Cost of equipment.

5. Danger of hose failure due to cold bending.

DESCRIPTION OF RELATED ART INCLUDING INFORMATION DISCLOSED UNDER 37 CFR 1.97 AND 37 CFR 1.98.

The present inventor invented U.S. Pat. No. 4,309,875 issued to Radichio Jan. 12, 1982 for a Pipe Freezer or the Like, in which a self contained freezing device forms a plug of ice within a pipe section. A refrigeration unit supplies refrigerant to a cradle-like freezer unit within which the section of pipe to be frozen is held in spaced relation to the inner face of the freezer. The space between the underside of the pipe and the inner face of the freezer is filled with water, for example, by spraying. As the water in contact with the cradle-like freezer unit freezes, it covers the outer surface of the pipe section with an ice jacket. Alternatively, a bag of freezable gel may be substituted for the water spray and placed over the inside face of the freezer; and then the pipe section is placed within the fold of the bag. In the case of either alternative, the refrigerant is maintained inside the freezer, and out of contact with the pipe.

My U.S. Pat. No. 5,548,965 to Chen and Radichio issued on Aug. 27, 1996 for a Multi-cavity Evaporator which has an outer surface and an inner chamber. The outer surface has at least two pipe receiving surfaces and a pair of ends. The evaporator has a bore extending from one of the ends to the inner chamber. A tube extends into the bore sealing the chamber, such that a refrigerant flows into the inner chamber through an inner tube and out of the inner chamber through the outer tube. Each of the pipe receiving surfaces has a distinct surface adapted for receiving different size pipes.

BRIEF SUMMARY OF THE INVENTION.

The present invention uses a multi-cavity adapter having from two to eight cavities to fit standard plumbing pipes in copper, steel and plastic, metric and US standard. The refrigeration evaporator fits into a cylindrical bore in the core of the radial multi-cavity array. The cavities are arrayed around the circumference of the bore. The extrusion that forms the array is of aluminum or the like.

The coolant lines are elbowed at 90 degrees to the evaporator's longitudinal axis to facilitate attachment to pipes in small or tight spaces and from the side of the pipes. The central bore in the adapter body has a diameter slightly larger than the diameter of the evaporator which allows the evaporator to swivel freely in the adapter body thus minimizing wear and tear on the refrigeration lines to the evaporator when the evaporator is inserted into the central bore of an adapter body of the multi cavity adapter. Any of the cavities on the adapter body can be lined up with the pipe. When a single adapter is being used, the adapter is positioned on the pipe and secured with a strap having hook and loop fastening material. Then the cartridge evaporator is plugged into the adapter.

More preferably two units, a unit on either side of the pipe, are strapped in place to fully surround the pipe. Most preferably a special set of adjustable retainer mechanisms is used to tightly secure the adapters to the section of pipe to be frozen.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING.

FIG. 1

is a perspective view of a pipe freezing system utilizing my multi cavity adapter and using nonexpendable refrigerants;

FIG. 2

is a perspective view of one of the adapter bodies of the multi cavity adapter;

FIG. 3

is an enlarged perspective view of

FIG. 1

with most of the protective hose and the refrigeration system removed;

FIG. 4

is a bottom view of the

FIG. 3

;

FIG. 5A

is a side perspective view of an adapter body with the cartridge evaporator removed;

FIG. 5B

is an exploded view of

FIG. 5A

, and also shows a turned over evaporator cap to show its details;

FIG. 6

shows an elevation in section of a pipe with frozen plug;

FIG. 7

is a diagrammatic plan view of the refrigeration unit of

FIG. 1

;

FIG. 8

is an illustration of the fact that the secondary adapter body is substantially a mirror image of the primary adapter body;

FIG. 9

shows the adjustment settings of the special retainer mechanism required to interconnect the adapter bodies around any of the four standard pipe sizes that the adapter bodies can accommodate;

FIG. 10

is an exploded view of the special retainer mechanisms;

FIG. 11

shows a single adapter strapped to a pipe;

FIG. 12

which shows two adapters strapped to a pipe;

FIG. 13A

shows a perspective view of a pipe freezing system having one evaporator utilizing expendable refrigerants which utilizes my multi cavity adapter;

FIG. 13B

shows a perspective view of a pipe freezing system having one evaporator utilizing expendable refrigerants which utilizes my multi cavity adapter;

FIG. 14

is an enlarged perspective view of

FIG. 13

with most of the protective hose and the tank removed;

FIG. 15

is a diagrammatic plan view of the invention in use when using an expendable refrigerant;

FIG. 16

is a diagrammatic plan view of the invention in use when using an nonexpendable refrigerant;

FIG. 17

is a perspective view of the tight space of

FIG. 16

showing the invention mounted upon the section of pipe to be frozen;

FIG. 18

is a perspective view of the tight space of

FIG. 16

showing the invention mounted upon the section of pipe to be frozen;

FIG. 19

is a perspective view of FIG.

18

;

DETAILED DESCRIPTION OF THE INVENTION.

Detailed Description of the Elements of the Preferred Embodiment

Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views,

FIG. 1

illustrates a perspective view of a pipe freezing system (utilizing non-expendable refrigerants) utilizing my multi-cavity adapter. (

FIG. 13

, described later, illustrates a perspective view of a pipe freezing system utilizing expendable refrigerants which utilizes my multi cavity adapter.) The multi-cavity adapter, generally designated as

20

in

FIG. 1

, is designed for the removal of heat from liquid filled pipes, such as

22

, to bring the liquid contents

24

, as in

FIG. 6

, below the liquid's freezing point, and to cause an ice blockage

26

, as in

FIG. 6

, within pipe

22

. With ice plug

26

in place, pipe

22

may now be cut open as at

28

, to make plumbing repairs without the need of a valve.

As best seen in

FIGS. 2 and 3

, the multi-cavity adapter for a pipe freezer, generally shown by reference numeral

20

, consists of an elongated piece of thermally conductive material

30

which has a first end face

32

, a second end face

34

, and a bore

36

passing through the piece of thermally conductive material

30

. This elongated piece of thermally conductive material

30

will be referred to as an adapter body. The bore

36

serves as a cartridge evaporator receiving port for the reception of a cartridge evaporator

38

therein.

FIG. 5A

shows a cartridge evaporator

38

removed from the cartridge evaporator receiver port

36

of an adapter body

30

.

FIG. 5B

is an exploded view of

FIG. 5A

, and also shows a evaporator cap

136

upside down to reveal its structure. The bore

36

extends from the first end face

32

to the second end face

34

of the adapter body

30

. Preferably, the bore

30

is a central bore

30

. The outer surface

40

of the adapter body

30

has a plurality of concave pipe receiving surfaces

42

-

48

. Preferably, each concave pipe-receiving surface

42

-

48

has an arc of approximately 180 degrees. Each concave pipe receiving surface

42

-

48

has a specific distinct radius of curvature which is different than the radii of curvature of the other pipe receiving surfaces

42

-

48

. Thus, pipes

22

with different outside diameters can be quickly and easily accommodated. (Please see

FIG. 9.

) The intersection of each pipe receiving surface

42

-

48

and the outer surface

40

defines a first corner edge

50

,

54

,

58

,

62

and a second corner edge

52

,

56

,

60

,

64

of each of the pipe receiving surfaces

42

-

48

. The intersection of each corner edge

50

-

64

with the first end face

32

defines a corner point of the first end face. The intersection of each corner edge with the second end face

34

defines a corner point of the second end face

34

.

Applicant's preferred embodiment of a multi cavity adapter

20

has an adapter body

30

with at least four pipe receiving surfaces

42

-

48

so that various sized pipes can be accommodated. As shown in

FIGS. 2 and 9

, the four pipe receiving surfaces

42

-

48

of the adapter body can accommodate pipes with outside diameters of 1.651 cm, 2.921 cm, 2.286 cm, and 4.191 cm (0.65, 1.15, 0.90, and 1.65 inches) respectively. The adapter body

30

of the multi cavity adapter

20

is thus designed to fit standard plumbing pipes in copper, steel and plastic, in both metric and US standard sizes. Occasionally, however, one will be required to freeze a pipe with a diameter which is different from that of the four pipe receiving surfaces

42

-

48

. For this purpose applicant's invention also includes a bushing adapter

70

(also called a reducer bushing, or sleeve) for accommodating pipes with other outside diameters. As shown in

FIGS. 11-12

, the outer surface

72

of the bushing adapter

70

is convex and complimentary to one of the concave pipe receiving surfaces

42

-

48

of the adapter body

30

. The inner surface

74

of the bushing adapter

70

is concave and has a specific distinct radius different from the pipe receiving surfaces

42

-

48

of the adapter body

30

and is adapted to receive a pipe.

Preferably, as shown in

FIG. 3

, Applicant's invention includes a second elongated piece of thermally conductive material

78

which will be referred to as the secondary adapter body

78

, and, in this case, the first elongated piece of thermally conductive material

30

will be referred to as the primary adapter body. The secondary adapter body

78

is substantially a mirror image of the primary adapter body

30

. (It should be noted, as shown in

FIG. 8

, that if one places two of the primary adapter bodies

30

,

31

in a row

80

from left to right, and the second one

31

in the row

80

is rotated about the central axis of its central bore

36

by 180 degrees (as shown in row

82

) and then turned upside down (as in row

84

), it is a mirror image of the first one

30

in the row.)

Applicant's invention contemplates two ways of fastening the multi cavity adapters

20

to the section of pipe

22

to be frozen. In Applicant's preferred embodiment as shown in

FIG. 3

, both the primary

30

and secondary

78

adapter bodies have locking channels

86

which are substantially parallel to the axes of the central bores

36

of the adapter bodies and extend from the first end face

32

to the second end face

34

of each of the adapter bodies

30

,

78

. As shown in

FIG. 1

there are four locking channels

86

in each adapter body. Each locking channel

86

has a channel opening

88

in the first end face

32

and a second channel opening

89

in the second end face

34

. Preferably, the circular edges of the channel openings

88

,

89

of these locking channels

86

are approximately 0.25 cm (0.1 inches) from an edge of the adapter first end face

32

and situated between the corner points of the first end face

32

at a position where there will be no interference between the pipe section

22

to be frozen and the retainer mechanisms

90

,

92

when the retainer mechanisms

90

,

92

are inserted in those channels

86

. Most preferably as shown in

FIG. 9

, the channel openings

88

of these locking channels

86

are situated such that the number of adjustment settings of the special retainer mechanism required to interconnect the adapter bodies around any of the four standard pipe sizes that the adapter bodies can accommodate are minimized.

Special adjustable fastening mechanisms such as the retainer mechanisms

90

,

92

as shown in

FIG. 3

(and in greater detail in

FIG. 10

which is an exploded view of these) are used to fasten the primary

30

and secondary

78

adapter bodies to the section of pipe

22

to be frozen. The first retainer mechanism

90

has a first prong

94

and a second prong

96

. These prongs

94

,

96

are threaded at their ends

98

. The first prong

94

is adapted to be received into a channel opening

88

of the primary adapter body

30

, and the second prong

96

is adapted to be received into a channel opening

88

of the secondary adapter body

78

, so that when the primary

30

and secondary

78

adapter bodies are aligned such that a pipe receiving surface

42

-

48

of the primary adapter body

30

is facing a pipe receiving surface

42

-

48

of the secondary adapter body which has the same radius of curvature as the primary adapter body

30

, the primary

30

and secondary

78

adapter bodies can be hingedly fastened together by the first retainer mechanism

90

, such that the primary

30

and secondary

78

adapter bodies can be draped around the section of pipe

22

which is to be frozen. The first retainer mechanism

90

includes two nuts

100

,

100

for threading onto the ends

98

,

98

of the threaded prongs

94

,

96

for securing the first retainer mechanism

90

in the locking channels

86

,

86

.

The second retainer mechanism

92

is essentially similar to the first retainer mechanism

90

. It has a first prong

94

and a second prong

96

, and the prongs are threaded at their ends. The first prong

94

is adapted to be received into a locking channel

86

of the primary adapter body

30

, and the second prong

96

is adapted to be received into a locking channel

86

of the secondary adapter body

78

, so that the primary

30

and secondary

78

adapter bodies can be fastened together, such that the primary

30

and secondary

78

adapter bodies can tightly encompass and secure the section of pipe

22

which is to be frozen.

In Applicant's preferred embodiment, special retainer mechanisms

90

,

92

as shown in

FIG. 3

, are used to fasten the multi-cavity adapters

20

to the section of pipe

22

to be frozen. Each retainer mechanism

90

,

92

consists of a first and second locking pin

102

,

104

, a straight pin

116

, which interconnects them, and a spring

118

under tension mounted on the straight pin

116

between the two locking pins

102

,

104

to hold the locking pins

102

,

104

apart from one another. As best seen in

FIGS. 3 and 10

, the first retainer mechanism generally shown by reference number

90

in

FIG. 10

consists of a first locking pin

102

whose first end

106

has a golf club-like head

108

which has a nonthreaded hole

110

. The golf club-like head

108

is offset from the central axis of the locking pin

102

so that when the retainer mechanisms

90

,

92

are inserted into the adapter bodies to be joined, the offsets will ensure that the straight pins

116

,

116

of the retainer mechanisms

90

,

92

will not come in contact with the section of pipe

22

to be frozen. These golf club-like heads

108

,

110

are referred to as offset golf club-like heads. The second end

120

of the first locking pin

102

is threaded. The second locking pin

104

, likewise, has a golf club-like head

110

which has a threaded hole

114

. The diameter of this threaded hole

114

is smaller than the diameter of the nonthreaded hole

112

in the golf club-like head

108

of the first locking pin

102

. The second end

120

of the second locking pin

104

is threaded. These two locking pins

102

,

104

are connected via a straight pin

116

. The straight pin

116

has a first end with an Allen head

122

with a diameter larger than the diameter of the nonthreaded hole

112

in the golf club-like head

108

of the first locking pin

102

. The straight pin is threaded except for the Allen head end

122

. The straight pin

116

is adapted to be inserted into the nonthreaded hole

112

of the offset golf club like head

108

of the first locking pin

102

. It is then pushed through that hole

112

until it engages the threaded hole

114

of the offset golf club like head

110

of the second locking pin

104

, and then is screwed into the threaded hole

114

of the second locking pin

104

. A pair of nuts

110

,

110

are screwed onto the second ends

120

,

120

of each locking pin to secure the first retainer mechanism

90

in the locking channels

86

,

86

. The Allen head end

122

of the straight pin

116

is then turned to draw together the golf club-like heads

108

,

110

of the locking pins

102

,

104

and thus tighten and secure the adapter bodies

30

,

78

on the section of pipe

22

to be frozen.

Preferably, a spring

118

under tension is mounted on the straight pin

116

of each retainer mechanism

90

,

92

. This spring

118

serves to push apart and hold the first and second locking pins

102

,

104

in substantially parallel alignment to one another, which enables one to simultaneously insert the locking pins

102

,

104

into corresponding locking channels

86

,

86

of the primary

30

and secondary

78

adapter bodies.

The second retainer mechanism

92

consists of a first locking pin

102

whose first end

106

has a golf club-like head

108

which has a nonthreaded hole

110

. Again, the golf club-like head

108

is offset from the central axis of the locking pin

102

so that when the retainer mechanisms

90

,

92

are inserted into the adapter bodies to be joined, the offsets will ensure that the straight pins

116

,

116

of the retainer mechanisms

90

,

92

will not come in contact with the section of pipe

22

to be frozen. As mentioned above in the description of the first retainer mechanism, these golf club-like heads

108

,

110

are referred to as offset golf club-like heads. The second end

120

of the first locking pin

102

is threaded. The second locking pin

104

, likewise, has a golf club-like head

110

which has a threaded hole

114

. The diameter of this threaded hole

114

is smaller than the diameter of the nonthreaded hole

112

in the golf club-like head

108

of the first locking pin

102

. The second end

120

of the second locking pin

104

is threaded. These two locking pins

102

,

104

are connected via a straight pin

116

. The straight pin

116

has a first end with an Allen head

122

with a diameter larger than the diameter of the nonthreaded hole

112

in the golf club-like head

108

of the first locking pin

102

. The straight pin is threaded except for the Allen head end

122

. The straight pin

116

is adapted to be inserted into the nonthreaded hole

112

of the offset golf club like head

108

of the first locking pin

102

. It is then pushed through that hole

112

until it engages the threaded hole

114

of the offset golf club like head

110

of the second locking pin

104

, and then is screwed into the threaded hole

114

of the second locking pin

104

.

In use, the locking pins

102

,

104

of the second retainer mechanism

92

are not fully inserted into the locking channels

86

,

86

. Therefore, when the Allen head

122

of the straight pin

116

is tightened, thus pulling the upper parts of the locking pins

102

,

104

together, the lower tips

120

,

120

of the locking pins

102

,

104

spread apart and contact the inner walls of the locking channels

86

,

86

. Thus the locking pins

102

,

104

bind in the locking channels

86

,

86

, thus securing the locking pins

102

,

104

in the locking channels

86

,

86

, and a second set of nuts is not needed to hold the locking pins

102

,

104

of the second retainer mechanism in the locking channels

86

,

86

. In other words, by tightening the Allen head

122

of the straight pin

116

interconnecting the two locking pins

102

,

104

, we can make the distance between the two locking pins

102

,

104

less than the distance between the channel openings

88

,

88

of the adapter bodies

30

,

78

we are fastening together around the section of pipe

22

to be frozen, and thus the locking pins

102

,

104

will bind as you push them into their set of channel openings

88

,

88

. The approximate distances between channel openings of the adapter bodies to be joined by the retainer mechanisms

90

,

92

in Applicant's preferred embodiment are shown in FIG.

9

.

Applicant has found that if both retainer mechanisms

90

,

92

are inserted in the same ends of the adapter bodies

30

,

78

, when the Allen heads of the straight pins

116

,

116

are turned to tighten the locking pins

102

,

104

, the adapter bodies

30

,

78

are pulled together at that end and tend to spread apart at the other end. The result is that there is not a good overall contact of the adapter bodies

30

,

78

on the section of pipe

22

to be frozen. Therefore, preferably, if the first retainer mechanism

90

is inserted in channel openings

88

,

88

of the first end faces

32

,

32

of the primary

30

and secondary

78

adapters, the second retainer mechanism

92

should be inserted in channel openings

89

,

89

of the second end faces

34

,

34

of the primary

30

and secondary

78

adapters. When this is done, the two adapter bodies

30

,

78

can be tightly secured to the section of pipe

22

to be frozen.

An alternate adjustable fastening mechanism for fastening a multi cavity adapter

20

to the section of pipe

22

to be frozen is a flexible strap with hook and loop fastener material such as shown in

FIG. 11

which shows a single adapter

20

strapped to a pipe

22

and

FIG. 12

which shows two adapters

20

,

20

strapped to a pipe. In use, pipe

22

is wet. Then two adaptors

20

and

20

are strapped by hook and loop (such as Velcro®) strap

124

around pipe

22

. Thus the two adaptors

20

,

20

clamp to both sides of pipe

22

.

As shown in

FIGS. 1

,

3

, and

4

, a close fitting cartridge type evaporator

38

is inserted in the central bore

36

of each adapter body

30

,

78

. This type of cartridge evaporator provides a way for using a refrigerant to freeze a pipe

22

for those types of pipe freezers which use Applicant's multi cavity adapter

20

to encompass the section of pipe

22

to be frozen.

As best seen in

FIGS. 5A and 5B

(which is an exploded view of FIG.

5

A), the cartridge evaporator

38

has an inner chamber

126

and a bore

128

which extends from the first end surface

130

of the cartridge evaporator to the inner chamber

126

. A metering tube

132

extends into the bore

128

and protrudes into the inner chamber

126

of the evaporator

38

for moving a refrigerant into the inner chamber

126

of the evaporator

38

at a predetermined rate. The metering tube

132

of Applicant's invention is a capillary tube having an outside diameter of 1.778 mm (0.07 inches) and an inside diameter of 0.5588 mm (0.022 inches). A return tube

134

extends out of the bore

128

for moving evaporated refrigerant out of the inner chamber

126

of the evaporator. In use, refrigerant flows into the inner chamber

126

through the metering tube

132

and evaporated refrigerant flows out of the inner chamber

126

through the return tube

134

. Preferably, as shown in

FIGS. 5A and 5B

, the metering tube

132

passes through and is surrounded by the return tube

134

, thus providing protection for the metering tube

132

.

Preferably, the first end

138

of the cartridge evaporator

38

has a cap

136

which is fixedly fitted over the first end

138

of the cartridge evaporator

38

. The cap

136

has a side wall

140

which extends along the outer surface

39

of the evaporator

38

for at least a portion of the length of the outer surface

39

. The cap

136

has a first end

144

which is closed, and a second end

146

which has a face

150

with a sufficiently large bore

148

in it for the second end

146

of the cap

136

to fit over the first end

138

of the evaporator

38

. The face

150

of the second end

146

of the cap

38

has an outside diameter which is greater than the diameter of the central bore

36

of the adapter

38

serving as the cartridge evaporator receiving port

36

. Thus, when the second end

152

of the evaporator

38

having this cap

136

is inserted into the central bore

36

at one end of the adapter body

30

,

78

and pushed along the bore

36

, the face of the cap

136

eventually comes to rest against the end face (

32

or

34

) of that adapter

30

,

78

.

As shown in

FIGS. 1 and 13

, in which a nonexpendable refrigerant is being used, Applicant's invention contemplates a complete pipe freezing system

154

for freezing the contents of a section of pipe

22

. As shown in

FIG. 7

which shows the interior details of the refrigeration unit, this pipe freezing system

154

consists of a refrigeration unit

156

having a compressor

158