Pressure processing a pumpable substance with a flexible membrane

An apparatus and method for pressure processing a pumpable substance, such as a pumpable food product or slurry. In one embodiment, the apparatus includes a pressure vessel having an inlet valve toward one end and outlet valve toward the other end. A flexible bladder is coupled between the inlet and outlet valves for receiving the pumpable substance. The pressure vessel can further include a high-pressure inlet port for receiving high-pressure fluid that biases the membrane inwardly to pressure process the pumpable substance. The pumpable substance is then removed from the vessel through the outlet valve.

TECHNICAL FIELD
 This invention relates to methods and devices for pressure processing
 pumpable substances, such as food or abrasive slurries, using a flexible
 membrane.
 BACKGROUND OF THE INVENTION
 Conventional ultrahigh-pressure fluid systems have been used to pressurize
 pumpable substances, such as foods and slurries. For example, conventional
 ultrahigh-pressure systems have been used to improve the quality and
 longevity of food by subjecting the food to pressures in excess of 10,000
 psi. Conventional systems have also been used to pressurize abrasive
 slurries to ultrahigh-pressure levels. The slurries can then be directed
 toward a substrate in the form of a liquid jet to cut the substrate or
 treat the surface of the substrate.
 One conventional system includes a high-pressure cylinder with a slidable
 piston that divides the cylinder into two regions. The pumpable substance
 is placed in one region while a high-pressure fluid is introduced into the
 other region, driving the piston against the pumpable substance at a very
 high pressure. One potential drawback with this system is that as the
 piston may require specially designed seals to prevent the high-pressure
 fluid from being transported by the piston into the pumpable substance
 region. The seals may require periodic monitoring and replacement.
 Accordingly, it may be desirable to use an improved apparatus for
 pressurizing a pumpable substance while reducing the likelihood for
 contact between the pumpable substance and the pressurizing liquid.
 SUMMARY OF THE INVENTION
 The invention relates to methods and apparatus for pressure processing a
 pumpable substance, such as a food substance. In one embodiment, the
 apparatus includes a generally rigid high-pressure vessel having a first
 opening toward one end, a second opening toward the other end, and an
 internal vessel wall between the first and second ends. A flexible
 membrane is disposed within the vessel and has a first membrane opening in
 fluid communication with the first open end of the vessel and a second
 membrane opening in fluid communication with the second opening of the
 vessel. At least a portion of the membrane is movable away from the vessel
 wall to pressurize a portion of the pumpable substance positioned adjacent
 to the membrane.
 In one embodiment, the second membrane opening can be positioned beneath
 the first membrane opening so that the pumpable substance can exit the
 membrane through the second opening under the force of gravity. In another
 embodiment, valves are coupled to the first and second openings of the
 high-pressure vessel. In one aspect of this embodiment, the valves can
 each include a passage having a first portion with a first opening and
 second portion with a second opening. A piston is sealably positioned in
 the passage and axially movable within the passage between a closed
 position with the piston blocking fluid communication between the first
 and second openings and an open position with the first and second
 openings being in fluid communication with each other. The pumpable
 substance can be pumped into the membrane through the first opening,
 pressurized within the membrane by a high-pressure fluid disposed between
 the membrane and an inner wall of the vessel, and released from the
 pressure vessel through the second opening.

DETAILED DESCRIPTION OF THE INVENTION
 In general, conventional devices for pressure processing pumpable
 substances have been directed to high-pressure cylinders having an
 internal piston and/or having an inlet and outlet for the pumpable
 substance at one end of the cylinder and an inlet and outlet for the
 high-pressure fluid at the opposite end of the cylinder. By contrast, one
 aspect of the present invention includes a high-pressure cylinder having a
 flexible bladder with an entrance opening for the pumpable substance at
 one end of the bladder and an exit opening for the pumpable substance at
 the opposite end of the bladder. Accordingly, in one embodiment, the
 pumpable substance can be introduced through an inlet port at one end of
 the cylinder and removed from an outlet port at the opposite end of the
 cylinder, reducing the likelihood for contamination of the outlet port
 with unpressurized pumpable substance. The apparatus can also take
 advantage of gravitational forces to more completely remove the pumpable
 substance from the pressure vessel. Furthermore, by separating the inlet
 and outlet ports, each port can be larger, increasing the rate at which
 the pumpable substance can be moved into and out of the bladder, and
 increasing the size of pumpable substance constituents that can pass into
 and out of the bladder.
 An apparatus 10 for pressure processing a pumpable substance in accordance
 with an embodiment of the invention is shown in FIG. 1. The apparatus 10
 includes a pressure vessel 12 that receives the pumpable substance from a
 pumpable substance source 30 and pressurizes the pumpable substance with
 fluid supplied by a high-pressure fluid source 41. The pressure vessel 12
 can include an open-ended cylinder 13 surrounded by a protective
 cylindrical shield 14. Two valve assemblies 20, shown as an inlet valve
 assembly 20a and an outlet valve assembly 20b, cap opposite ends of the
 cylinder 13, and are clamped against the cylinder 13 with a yoke 11. A
 flexible bladder 50 is coupled between the valve assemblies 20. The
 pumpable substance is pumped into the bladder 50 through the inlet valve
 assembly 20a, pressurized by high-pressure fluid entering the cylinder 13
 from the high-pressure fluid source 41, and pumped through the outlet
 valve assembly 20b to a receptacle 80, as will be discussed in greater
 detail below.
 In one embodiment, the pressure vessel 12 can include a model number 012122
 assembly available from Flow International Corporation of Kent, Wash. that
 includes the cylinder 13, the yoke 11 and the shield 14, configured to
 withstand an internal vessel pressure of at least 100,000 psi. In other
 embodiments, the pressure vessel 12 can include other cylinders 13 and
 peripheral components configured to withstand an internal pressure of
 100,000 psi or another suitable pressure, depending upon the selected
 pumpable substance and treatment. Such vessels and components are
 available from ABB Pressure Systems of Vasteras, Sweden, Autoclave
 Engineering of Erie, Pa., or Engineered Pressure Systems of Andover, Mass.
 The pressure vessel 12 can include a liner 15 adjacent an inner surface of
 the cylinder 13. The liner can be formed from stainless steel or other
 suitable materials that can withstand the high internal pressures within
 the cylinder 13. In one embodiment, the liner 15 can be attached to the
 cylinder 13 by first heating the cylinder 13 so that it expands, then
 placing the cylinder 13 around the liner 15, and then cooling the cylinder
 13 so that it shrinks tightly around the liner 15. If the liner 15 later
 becomes worn or damaged it can be removed from the cylinder 13 and
 replaced with a similar liner. An advantage of this arrangement is that
 cracks that might result from the high pressure within the pressure vessel
 12 will tend to form in the liner 15 rather than in the cylinder 13, and
 it may be easier and less expensive to replace the liner 15 than the
 cylinder 13.
 FIG. 2 is an enlarged cross-sectional side elevation view of the upper
 portion of the apparatus 10 shown in FIG. 1. As shown in FIG. 2, the inlet
 valve assembly 20a fits partially within the cylinder 13 and includes a
 flow channel 31 having a radial portion 32 in fluid communication with an
 axial portion 33. Both the radial portion 32 and the axial portion 33 can
 be strengthened or reinforced, for example, by passing through these
 portions a die having a slightly oversized diameter, or by using other
 known strengthening techniques. An inlet port 27a at one end of the radial
 portion 32 is coupled to the pumpable substance source 30 (FIG. 1). A
 bladder port 34 at the opposite end of the axial portion 33 is coupled to
 the bladder 50. An inlet sealing piston 22a moves axially upwardly and
 downwardly within the axial portion 33 between an open position (shown in
 FIG. 2) in which the pumpable substance can pass into the bladder 50 and a
 closed position (discussed in greater detail below with reference to FIG.
 3) in which the pumpable substance is sealed within the bladder 50.
 When the inlet valve assembly 20a is in its open position, the inlet
 sealing piston 22a is retracted upwardly into a sealing block 23. An upper
 piston seal 70a, disposed annularly about the inlet sealing piston 22a,
 seals the interface between the inlet sealing piston 22a and the axial
 portion 33 of the flow channel 31 to at least restrict the pumpable
 substance from passing upwardly along the inlet sealing piston 22a. A
 lower fluid gap 38a extends annularly about the inlet sealing piston 22a,
 just above the upper piston seal 70a, for collecting and removing pumpable
 substance that might escape past the upper piston seal 70a. Purging fluid
 can be pumped through an upper inlet port 28a and into the lower fluid gap
 38a, where it can entrain pumpable substance that might be present in the
 lower fluid gap 38a. The purging fluid and entrained pumpable substance
 can then be removed through an upper exit port 29a. In one embodiment, the
 purging fluid can include water, and in other embodiments the purging
 fluid can include iodine or other substances that sanitize the surfaces in
 contact with the purging fluid.
 The inlet valve assembly 20a further includes a lower seal 70b beneath the
 upper seal 70a. When the inlet sealing piston 22a is in its open position
 (as shown in FIG. 2), the lower seal 70b is covered with a sleeve 74 that
 is biased upwardly by a sleeve spring 75. The sleeve 74 protects the lower
 seal 70b from contact with the pumpable substance. The lower seal 70b is
 exposed and seals against the inlet scaling piston 22a when the inlet
 sealing piston 22a is moved to its closed position, as will be discussed
 in greater detail below.
 The inlet sealing piston 22a is driven from its open position to its closed
 position by a driver piston 21 that moves axially within the sealing block
 23. Accordingly, the sealing block 23 includes a driver fluid port 25 that
 supplies pressurized fluid to the driver piston 21 to move the driver
 piston and the inlet sealing piston 22a together in a downward direction.
 The sealing block 23 itself can slide laterally along a block rail 24 to
 secure the inlet sealing piston 22 in the closed position. Accordingly,
 the sealing block 23 can include an actuator 26 that moves the sealing
 block 23 laterally back and forth along the block rail 24.
 In operation, the inlet sealing piston 22a moves downwardly from its open
 position to its closed position under the force of the driver piston 21.
 As the inlet sealing piston 22a moves downwardly, it engages the sleeve
 74, forcing the sleeve downwardly against the resistance provided by the
 sleeve spring 75. At this point, both the upper seal 70a and the lower
 seal 70b seal against the inlet sealing piston 22a and the inlet sealing
 piston 22a blocks communication between the radial portion 32 and the
 axial portion 33 of the flow channel 31. The inlet sealing piston 22a
 continues to move in a downward direction until an end cap 35 at the upper
 end of the inlet sealing piston 22a is aligned with a cap engaging surface
 36 of the sealing block 23. The sealing block 23 then slides laterally as
 indicated by arrow A along the block rail 24 until the end cap 35 engages
 the cap retaining surface 36. The inlet sealing piston 22a is accordingly
 secured in its closed position.
 To open the valve 20a, the sealing block 23 is moved laterally as indicated
 by arrow B until the driver piston 21 is axially aligned with the inlet
 sealing piston 22a. The sleeve spring 75 then moves the sleeve 74
 upwardly, and the sleeve 74 together with pressure from within the bladder
 50 drive the inlet sealing piston 22a upwardly to its open position.
 FIG. 3 is a cross-sectional side elevation view of the inlet valve 20a of
 FIG. 2 shown in the closed position. The inlet sealing piston 22a has
 moved downwardly in the axial portion 33 of the flow channel 31 and the
 sealing block 23 has moved laterally so that the cap engaging surface 36
 engages the end cap 35 to prevent the inlet sealing piston 22a from moving
 in an upward direction. The inlet sealing piston 22a has moved the sleeve
 74 downwardly so that the lower piston seal 70b engages the inlet sealing
 piston 22a. Accordingly, the lower fluid gap 38a, now positioned just
 above the lower piston seal 70b, is aligned with a lower inlet port 28b
 and a lower exit port 29b to remove pumpable substance from the lower
 fluid gap 38a in a manner generally similar to that discussed above with
 reference to FIG. 2. An upper fluid gap 38b is aligned with the upper
 inlet port 28a and the upper exit port 29a to operate in a manner similar
 to that discussed above with reference to FIG. 2. Accordingly, the inlet
 valve 20a can prevent the pumpable substance from escaping upwardly past
 the inlet sealing piston 22a when the inlet valve 20a is in its closed
 position and the bladder 50 is under pressure.
 As shown in FIG. 3, the bladder 50 is attached to the sleeve 74 to receive
 the pumpable substance through the inlet valve 20a. In one embodiment, the
 bladder 50 includes an elongated tube having an upper opening 54. The
 bladder 50 can be formed from rubber, neoprene or any flexible, generally
 nonporous material. In one embodiment, the bladder 50 can include a
 medical-grade rubber suitable for use with food products. In another
 embodiment, the bladder 50 can include an abrasion-resistant rubber or
 other abrasion resistant material for use with abrasive slurries. In still
 another embodiment, the bladder 50 can include a laminate of multiple
 plies bonded together with an adhesive, such as a rubber cement. One
 advantage of this embodiment is that the bladder 50 can separate the
 pumpable substance from the high-pressure fluid even if one or more of the
 plies has a pin hole or other puncture. Another advantage is that the
 multiple plies can thicken the bladder 50 and provide thermal insulation
 between the pumpable substance and the high-pressure fluid. Accordingly,
 hot or cold pumpable substances can be pressure processed in the pressure
 vessel 12 with a reduced transfer of heat to or from the pumpable
 substance.
 A bladder fitting 51 extends through the upper opening 54 of the bladder 50
 and is attached to the bladder 50 with a band 53 or alternatively, with a
 food-grade adhesive that discourages microorganism growth, or another
 suitable securing device. The bladder fitting 51 is then coupled to the
 sleeve 74 with a removable coupling 52, such as are available from
 Tri-Clover, Inc., of Kenosha, Wis. In one embodiment, the bladder fitting
 51 can be sized to take up a substantial volume within the cylinder 13,
 thereby reducing the volume of high-pressure fluid required to pressurize
 the bladder 50 and reducing the time required to move the high-pressure
 fluid into and out of the cylinder 13.
 FIG. 4 is a cross-sectional side elevation view of the lower portion of the
 apparatus 10 shown in FIGS. 1-3. As shown in FIG. 4, the bladder 50
 includes a lower opening 55 attached to a bladder fitting 51 which is in
 turn coupled to a sleeve 74 of the outlet valve assembly 20b. In one
 embodiment, the bladder 50 can be stiffer near the lower opening 55 than
 near the upper opening 54 (FIG. 3) to prevent the bladder 50 from
 collapsing on itself near the lower opening 55 when the pumpable substance
 is removed. In one aspect of this embodiment, the stiffness of the bladder
 50 can decrease in a generally uniform manner in an upward direction
 extending away from the outlet valve assembly 20b. In another aspect of
 this embodiment, the bladder 50 can be made stiffer near the lower opening
 55 by increasing the number of plies that form the bladder 50 in this
 region.
 The outlet valve assembly 20b includes an outlet sealing piston 22b, a
 driver piston 21 and a sealing block 23, all of which operate in generally
 the same manner as was discussed above with reference to the inlet valve
 assembly 20a shown in FIGS. 2 and 3. Accordingly, the outlet valve
 assembly 20b is closed (as shown in FIG. 4) while the pumpable substance
 is pressurized, and is opened to allow the pressurized pumpable substance
 to pass out of the bladder 50.
 The outlet valve assembly 20b includes a high-pressure port 40 coupled to
 the high-pressure fluid source 41 (FIG. 1). The high-pressure fluid enters
 the pressure vessel 12 through the high-pressure port 40 at pressures up
 to and exceeding 100,000 psi, fills the region between cylinder 13 and the
 bladder 50, and pressurizes the contents of the bladder 50. In one
 embodiment, the high-pressure fluid can be water. Alternatively, the
 high-pressure fluid can be sterile citric acid or another sterile
 solution. In a further aspect of this embodiment, the high-pressure fluid
 can be selected to include water at an elevated temperature, for example,
 about 100.degree. F. At such elevated temperatures, the ductility of the
 metal forming the cylinder 13 can be increased, as determined using a
 Charpy test or other ductility tests.
 After pressurization, the pressurized pumpable substance can be removed
 through the outlet valve 20b by moving the outlet valve 20b to its open
 position and allowing the pumpable substance to pass through a pumpable
 substance exit port 27b to the receptacle 80 (FIG. 1). In one embodiment,
 the pumpable substance can exit the bladder 50 solely under the force of
 gravity. In one aspect of this embodiment, the inlet valve 20a is opened
 to a sterile environment at atmospheric pressure to allow the pumpable
 substance to descend from the bladder 50 under the force of gravity
 without introducing contaminants to the bladder 50. In another embodiment,
 the pumpable substance can be squeezed from the bladder 50 by filling the
 pressure vessel 12 with a fluid at a relatively low pressure. In one
 aspect of this embodiment (best seen in FIG. 3), the pressure vessel 12
 can include a low pressure valve 60 for transporting the low pressure
 fluid to and from the cylinder 13.
 The low pressure valve 60 (FIG. 3) can include a fluid passage 62 having a
 fluid port 61 at one end coupled to a source of the low pressure fluid
 (not shown). At the opposite end of the fluid passage 62 is a movable
 sealing ring 66 that can be moved between an open position (shown in FIG.
 3) that allows fluid communication between fluid passage 62 and the
 interior of the cylinder 13, and a closed position that prevents such
 fluid communication. In one embodiment, the sealing ring 66 is biased
 upwardly toward its closed position with a sealing ring spring 67. The
 sealing ring 66 can be moved downwardly against the force of the sealing
 ring spring 67 to its open position by an actuating piston 65. The
 actuating piston 65 can be positioned in a gas passage 64 and can move
 downwardly within the gas passage 64 when gas is supplied through a gas
 port 63. To close the fluid passage 62, the pressure at the gas port 63 is
 reduced, allowing the sealing ring spring 67 to move the sealing ring 66
 and the actuating piston 65 upwardly until the sealing ring seals against
 the inlet valve assembly 20a and closes the fluid passage 62.
 In one embodiment, the fluid passage 62 is one of three fluid passages 62
 coupled to the fluid port 61 and spaced 120.degree. apart from each other
 around the sleeve 74. Similarly, the gas passage 64 can be one of three
 gas passages 64 coupled to the gas port 63 and spaced 120.degree. apart
 from each other around the sleeve 74. In other embodiments, the low
 pressure valve 60 can include more or fewer fluid passages 62 and gas
 passages 64. An advantage of having a plurality of gas passages 64 is that
 they more evenly distribute the force applied to the sealing ring 66,
 reducing the likelihood that the sealing ring 66 will become cocked or
 tilted as it moves up and down. An advantage of having a plurality of
 fluid passages 62 is that the low pressure fluid can be more quickly and
 uniformly transported into and out of the cylinder 13. In another
 embodiment, the outlet valve 20b (FIG. 4) can also include a low pressure
 valve generally similar to the low pressure valve 60 discussed above. An
 advantage of having two low pressure valves 60 is that the low pressure
 fluid can be even more quickly transported into and out of the cylinder
 13. A further advantage is that the inlet and outlet valves 20a, 20b can
 be interchangeable.
 Operation of an embodiment of the apparatus 10 is best understood with
 reference to FIG. 1. Initially, the outlet valve assembly 20b is closed by
 moving the outlet sealing piston 22b to its upper position (shown in FIG.
 1) and the inlet valve assembly 20a is opened by moving the inlet sealing
 piston 22a to its upper position (shown in FIG. 1). The pumpable substance
 is pumped through the inlet valve assembly 20a and into the bladder 50.
 The inlet valve assembly 20a is then closed by moving the inlet sealing
 piston 22a downwardly and high-pressure fluid is pumped through the
 high-pressure port 40 of the outlet valve assembly 20b. The high-pressure
 fluid fills the space between the bladder 50 and the liner 15 and biases
 the bladder 50 inwardly to pressurize the pumpable substance within the
 bladder 50. The pumpable substance is then pressurized for a selected
 period of time.
 Turning now to FIG. 3, the low pressure valve 60 is opened by forcing gas
 through the gas passage 64 to move the actuating piston 65 against the
 sealing ring 66. As the sealing ring 66 moves away from the fluid passage
 62, high-pressure fluid escapes through the fluid passage 62 and out
 through the fluid port 61. The outlet valve 20b (FIG. 1) is then opened
 and fluid is supplied at low pressure through the low pressure valve 60 to
 collapse the bladder 50 and force the pressurized pumpable substance out
 through the outlet valve 20b. Once the bladder 50 has collapsed, the
 apparatus 10 is ready to pressure process a new batch of pumpable
 substance. After a selected number of pressure cycles, the bladder 50 can
 be cleaned, for example, by passing through the bladder (in succession) a
 rinse solution, a caustic solution, hot water, a chemical sterilizer and
 citric acid.
 An advantage of an embodiment of the apparatus 10 shown in FIGS. 1-4 is
 that the bladder 50 can eliminate contact between the pumpable substance
 and the high-pressure fluid. Accordingly, the likelihood that that
 pumpable substance will be contaminated with high-pressure fluid (and vice
 versa) is substantially reduced. A further advantage is that the inlet
 valve 20a is separated by a substantial distance from the outlet valve
 20b, reducing the likelihood of contaminating the pressurized pumpable
 substance with unpressurized pumpable substance. Furthermore, by
 positioning the outlet valve 20b beneath the inlet valve 20a, the
 apparatus 10 can take advantage of gravity to remove the pressurized
 pumpable substance from the vessel 12. Accordingly, a greater portion of
 the pumpable substance can be removed from the vessel 12 after
 pressurization.
 Yet another feature of the apparatus 10 is that the flow passages 31
 through the valves 20 can have relatively large cross-sectional areas.
 This is advantageous because it allows the pumpable substance to enter and
 exit the vessel 13 more quickly. It also allows pumpable substances having
 chunks or large suspended particles to be more easily directed into and
 out of the vessel 13. For example, when the apparatus 10 is used to
 pressure process chunks of fruit, such as pineapples, the flow passages 31
 can have diameters of about one inch. In other embodiments, the flow
 passages can have other diameters to accommodate chunks of pumpable
 substance having other dimensions.
 Still another advantage is that the movable sleeve 74 can reduce the
 likelihood of exposing at least one of the piston seals 70b to the
 pumpable substance. Accordingly, the pumpable substance is less likely to
 become trapped in the piston seal 70b. Yet another advantage is that the
 flow of purging fluid alongside the pistons 22 can further reduce the
 likelihood of pumpable substance escaping from the vessel 12 when the
 vessel 12 is under pressure.
 In the embodiment discussed above with reference to FIGS. 1-4, the pumpable
 substance is placed within the bladder 50 and the high-pressure fluid is
 disposed between the bladder 50 and the inner walls of the cylinder 13. In
 another embodiment, the pumpable substance can be positioned between the
 bladder 50 and the inner walls of the cylinder 13 while the high-pressure
 fluid is disposed within the bladder 50. An advantage of placing the
 pumpable substance in the bladder 50 is that it may be easier to remove
 the pumpable substance from within the bladder 50 than from between the
 bladder 50 and the walls of the cylinder 13.
 FIG. 5 is a cross-sectional side elevation view of the upper portion of the
 apparatus 10 shown in FIG. 1 having an inlet valve 120a in accordance with
 another embodiment of the invention. The inlet valve 120a includes a low
 pressure valve 160 generally similar in appearance and operation to the
 low pressure valve 60 discussed above with reference to FIG. 3. The inlet
 valve assembly 120a further includes a flow channel 131 having an axial
 portion 133 connected to a radial portion 132. One end of the axial
 portion 133 is closed with a plug 139, and the other end is coupled to the
 bladder 50. As will be discussed in greater detail below, fluid
 communication between the axial portion 133 and the radial portion 132 can
 be opened or closed by moving a piston within the radial portion 132.
 FIG. 6 is a top, partial cross-sectional view of the inlet valve 120a shown
 in FIG. 5. As shown in FIG. 6, the inlet valve 120a includes a sealing
 piston 122 that moves laterally within the radial portion 132 of the flow
 channel 131. When the sealing piston 122 is in its leftmost position
 (shown in FIG. 6) the pumpable substance can pass from the radial portion
 132 of the flow channel 131 to the axial portion 133 and into the bladder
 50 (FIG. 5). When the sealing piston 122 is in its rightmost position
 (discussed in greater detail below with reference to FIG. 7), the sealing
 piston 122 prevents fluid communication between radial portion 132 and the
 axial portion 133.
 The sealing piston 122 is sealed within the radial portion 132 with two
 piston seal assemblies 170, shown as a left piston seal assembly 170a and
 a right piston seal assembly 170b. The right piston seal assembly 170b is
 covered with a sleeve 174 when the inlet valve is in its open position (as
 shown in FIG. 6). The sleeve 174 is biased toward the covered position by
 a sleeve spring 175 when the inlet valve 120a is in the open position, in
 a manner generally similar to that discussed above with reference to the
 sleeve 74 shown in FIG. 2. The sleeve 174 includes an inlet port 127a
 coupled to the pumpable substance source 30 (FIG. 1) with a flexible
 conduit 126. Accordingly, the conduit 126 can maintain the connection
 between the pumpable substance source 30 and the inlet port 127a as the
 sleeve 174 moves laterally.
 The seal assemblies 170 can include a seal 171 that extends between the
 sealing piston 122 and the walls of the radial portion 132 of the flow
 channel 131. The seal assemblies 170 can also include an O-ring 172, an
 anti-extrusion ring 173 to prevent the seal 171 from extruding outwardly
 away from the radial portion 132, and a backup ring 176 to support the
 seal 171 and the anti-extrusion ring 173. This seal assembly arrangement,
 shown in detail in FIG. 6, can also be used in conjunction with the seals
 70a, 70b shown in FIGS. 1-4.
 A driver piston 121 connected to one end of the sealing piston 122 drives
 the sealing piston 122 laterally within the radial portion 132. The driver
 piston 121 moves within a driver cylinder 123 which can include two driver
 fluid ports 125 (shown as a left port 125a and a right port 125b). When
 pressurized fluid is supplied to the right port 125b, the driver piston
 121 and the sealing piston 122 move to the left toward the open position.
 When pressurized fluid is supplied to the left port 125a, the driver
 piston 121 and the sealing piston 122 move to the right toward the closed
 position.
 FIG. 7 is a top, partial cross-sectional view of the inlet valve assembly
 120a shown in FIG. 6 with the sealing piston 122 and the driver piston 121
 moved to the closed position. As shown in FIG. 7, the sealing piston 122,
 when in the closed position, prevents fluid communication between the
 radial portion 132 and the axial portion 133 of the flow channel 131.
 Accordingly, the sealing piston 122 can prevent pumpable substance from
 escaping from the cylinder 13 when the cylinder is pressurized.
 When the sealing piston 122 is in the closed position, it engages the
 sleeve 174 and moves the sleeve 174 to the right (as seen in FIG. 7) until
 the sealing piston 122 seals against the right seal assembly 170b. Fluid
 gaps 138 (shown as a left fluid gap 138a and a right fluid gap 138b)
 adjacent the sealing piston 122 receive purging fluid from inlet ports 128
 (shown as a left inlet port 128a and a right inlet port 128b) to purge the
 region adjacent the seals 170. The purging fluid, with pumpable substance
 entrained, can be removed through exit ports 129a and 129b in a manner
 generally similar to that discussed above with reference to the fluid gaps
 38 shown in FIGS. 2 and 3.
 From the foregoing it will be appreciated that, although specific
 embodiments of the invention have been described herein for purposes of
 illustration, various modifications may be made without deviating from the
 spirit and scope of the invention. For example, the liner 15 can be
 disposed in a high-pressure vessels that include means other than the
 bladder 50 for pressurizing the pumpable substance. Accordingly, the
 invention is not limited except as by the appended claims.