JP2012026490A - Seal ring, power-recovery device and seawater desalination unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal ring that has a long-life coating film having a stable quality, wherein the friction of the film is reduced to reduce driving energy of a piston, the film makes a power-recovery device high efficiency and is maintenance free for a long period, and also provide the power-recovery device and a seawater desalination unit with the seal ring.SOLUTION: The seal rings BR1 and BR3 are used by abutting on a sliding surface 67b on which a reciprocating and driving piston 63p and a cylinder 63s slide, or by abutting on a sliding surface 68b on which a piston rod 63r and the cylinder 63s slide. The seal rings include: annular base materials OR1 and OR3 having deformability for fluid-tightly sealing; and a diamond-like carbon film which covers at least part of the base materials OR1 and OR3 by the pulse plasma method and directly come into contact with the sliding surfaces 67b and 68b.

Description

  Embodiments described herein relate generally to a seal ring that seals a cylinder / piston fluid-tightly, and relates to a power recovery device and a seawater desalination device that use the seal ring.

  Seawater desalination equipment supplies seawater at a pressure higher than reverse osmosis pressure to a reverse osmosis membrane (hereinafter referred to as RO membrane), removes solutes such as salt in the seawater to produce freshwater, and the remaining seawater has a high concentration Drain as brine (brine). Since the brine is discharged at a high pressure, it has high pressure energy.

  Recently, in order to further save energy in the seawater desalination apparatus, a power recovery apparatus has been installed in the seawater desalination apparatus as ancillary equipment. The power recovery device is an energy saving device that recovers high-pressure brine and uses pressure energy held by the brine for pressurization of seawater, as described in Patent Document 1, for example.

JP 2009-103109 A, paragraph 0065

  By the way, the conventional power recovery device has a low friction coefficient and wear resistance as a sliding member (seal ring) for liquid-tight sealing between the cylinder and the piston in order to realize long-term maintenance-free operation. A material or an O-ring coated with a material having these characteristics is used. Various materials such as diamond-like carbon (hereinafter referred to as DLC) are described in Patent Document 1 as a coating film having a low coefficient of friction and wear resistance.

  However, the conventional DLC film tends to generate pinholes, and the film tends to crack due to the generated pinholes.

  In addition, since the base material constituting the sliding member is made of an insulating material such as hard rubber or resin and the surface is kept dry due to solid lubrication, static electricity is easily accumulated on the sliding member and is easily charged. Foreign matter tends to adhere to the charged sliding member.

  Furthermore, since the base material such as hard rubber or resin is sealed in a liquid-tight manner, it is mounted between the cylinder / piston in a compressed state, but the DLC film cannot follow the deformation of the base material, Prone to cracking and peeling.

  Embodiments of the present invention have been made to solve the above-mentioned problems, and can reduce piston drive energy by reducing friction, achieve high efficiency of a power recovery device, and realize long-term maintenance-free operation. It is an object of the present invention to provide a seal ring having a long-life and stable quality coating film, and a power recovery apparatus and a seawater desalination apparatus having the seal ring.

  The seal ring according to the present invention is a seal ring that is used in contact with a sliding surface on which a piston and a cylinder that are driven to reciprocate slide, or in contact with a sliding surface on which a piston rod and a cylinder slide. An annular base material having a deformability for liquid-tight sealing, a diamond-like carbon film coated on at least a part of the base material by a pulse plasma CVD method and in direct contact with the sliding surface; It is characterized by having.

  A power recovery apparatus according to the present invention includes a cylinder into which pressure fluid is introduced or discharged, a piston that is movably supported in the cylinder and that is driven to reciprocate in the cylinder by receiving pressure from the pressure fluid, and the piston And a seal ring that is held in a groove that opens in a sliding surface that slides in contact with the cylinder, wherein the seal ring has a deformability to seal liquid tightly. And a diamond-like carbon film coated on at least a part of the base material by a pulse plasma CVD method and in direct contact with the sliding surface.

  The seawater desalination apparatus according to the present embodiment supplies a reverse osmosis membrane module having a reverse osmosis membrane for separating a solute contained in seawater and seawater to the reverse osmosis membrane module in a state where pressure is applied to the seawater. A power recovery device having a pump, a cylinder for recovering the pressure of the concentrated water discharged from the reverse osmosis membrane module as power energy, and a piston; and when the piston reciprocates in the cylinder, And a seal ring that slides in contact with either the sliding surface or the sliding surface of the piston, wherein the seal ring has a deformability for liquid-tight sealing. An annular base material, and a diamond-like carbon film coated on at least a part of the base material by a pulse plasma CVD method and in direct contact with the sliding surface. And wherein the Rukoto.

  Important terms in this specification are defined below.

  The pulse plasma CVD method is a bias voltage in which a material gas is made plasma by intermittently generating a discharge by applying a superimposed power obtained by superimposing a high frequency power and a high voltage pulse power, and ions in the plasma are applied to the substrate. This is a chemical vapor deposition method in which a source gas component is deposited on a substrate by accelerating and pulling in the direction of the substrate with the electric field formed in step (b). In this pulsed plasma CVD method, the discharge is pulsed to form ions to be coated when a high frequency is applied, and the process of accelerating and depositing ions when a high voltage is applied is repeated. It is possible to form a laminated structure with the film. In addition, since stable discharge plasma is generated under a high gas pressure, a film having excellent adhesion can be obtained under a moderate vacuum.

The block diagram which shows the outline | summary of the seawater desalination apparatus which has a power recovery device. The block diagram which shows one form of the power recovery device at the time of operation | movement. The block diagram which shows the other form of the power recovery device at the time of operation | movement. The partial expanded sectional view which shows each sliding part between cylinders / pistons and between cylinders / rods of a power recovery device. The fragmentary sectional view which shows the seal member used for the sliding part between cylinders / pistons. (A) is a schematic diagram for demonstrating the film-forming principle of plasma CVD method, (b) is a schematic diagram for demonstrating the principle of an ion implantation method. The block diagram which shows the outline | summary of the apparatus used for a pulse plasma method. The figure which shows the principal part of the pulse plasma apparatus of FIG. (A) is a SEM photograph in which the surface of the DLC film formed by using the high-frequency plasma CVD method is photographed, and (b) is a SEM photograph in which a longitudinal section of the DLC film formed by using the high-frequency plasma CVD method is photographed. . The SEM photograph which image | photographed the longitudinal cross-section of the DLC film formed into a film using the pulse plasma CVD method. (A) is an SEM photograph of a longitudinal section of a DLC film (with cracks) formed by a high-frequency plasma CVD method, and (b) is another DLC film (with cracks) formed by a high-frequency plasma CVD method. SEM photograph of a longitudinal section. (A), (b), (c) is a schematic diagram for demonstrating the compression deformation test of the DLC film coated on the seal ring. The schematic diagram for demonstrating the friction coefficient measurement test of the DLC film coated on the seal ring. (A) is a characteristic diagram showing a friction coefficient measurement test result when the amount of compressive deformation is 0.5 mm, and (b) is a characteristic diagram showing a friction coefficient measurement test result when the amount of compressive deformation is 1.0 mm.

  Various preferred embodiments of the present invention are described below.

  (1) The seal ring according to the present embodiment is used in contact with the sliding surface on which the piston and cylinder to be reciprocated slide, or on the sliding surface on which the piston rod and cylinder slide. An annular base material having a deformability for liquid-tight sealing, and a diamond-like material that is coated on at least a part of the base material by a pulse plasma CVD method and is in direct contact with the sliding surface A carbon film.

  The DLC coating film formed using the high-frequency plasma CVD method has excellent adhesion to the base material, a columnar (wrinkle-like) structure develops in the surface layer portion, and the surface has irregularities (FIG. 9 (a) ( b)). This columnar (wrinkle-like) structure is excellent in deformability, so it is difficult to crack even when the substrate is deformed. However, because of the wrinkle-like structure, the hardness of the film is extremely low, and the surface pressure of the sliding surface When the surface pressure is small, an excellent low friction coefficient and wear resistance are exhibited. However, when the surface pressure is high as in the seal part of the seawater desalination apparatus, wear or delamination occurs in a short time. Furthermore, since the degree of vacuum in the coating is relatively high, it is impossible to coat a substrate having a large amount of volatile components such as nitrile rubber (NBR).

  On the other hand, the DLC coating film formed using the pulse plasma CVD method is not only excellent in adhesion to the base material but also excellent in film quality, and formed by the high frequency plasma CVD method. The surface is smooth compared to (Fig. 10). This film forms a relatively low hardness DLC film when the high-frequency power supply ON / high-voltage pulse power supply is OFF, and conversely forms a high hardness DLC film when the high-frequency power supply OFF / high-voltage pulse power supply is ON. Therefore, it is possible to obtain a film in which a soft film and a hard film are laminated in nanometer units. The residual stress in the DLC film can be made almost zero by such a nano-order layered structure and the effect of annealing of the film by local heating at the time of ion implantation, and the DLC film formed by the high-frequency plasma CVD method. It is harder than the film and has excellent properties such as high strength and deformability. In addition, since the coating atmosphere does not require high vacuum, it can be applied to rubber and resin with many volatile components such as nitrile rubber, and it can be easily applied to composite materials such as resin reinforced with inorganic particles. be able to.

  For the base material of the O-ring as the seal ring, any of resin, rubber-based material, or metal material can be used. Moreover, either a resin or a rubber-based material can be used for the base material of the bride ring as the seal ring. As the resin, ultra high molecular weight polyethylene (UHMW-PE) is preferred. As the rubber material, ethylene propylene rubber (EPDM) or the like is preferable. As the metal material, duplex stainless steel (SUS 329J1) or super duplex stainless steel (SUS 329J4L) is preferable.

  (2) In the above (1), it is preferable to coat a plurality of diamond-like carbon films on the base material.

  In this way, pinholes generated in the DLC film of the first layer can be closed by the DLC films of the second and subsequent layers, so that cracks starting from the pinholes do not occur. Therefore, a DLC coating film having high quality stability and a long life can be obtained.

  (3) In any one of the above (1) and (2), it is desirable that the thickness of the diamond-like carbon film is 1 μm or more, preferably 2 μm or more (FIG. 10).

  The life of the DLC film varies depending on the mating material, surface pressure, sliding conditions, etc. However, if the thickness is increased to 1 μm or more, preferably 2 μm or more, the life of the seal ring is extended and it is not necessary to replace the seal ring over a long period of time. For this reason, it becomes possible to make the power recovery device and high-pressure pump using the seal ring a maintenance-free treatment for a long time. In particular, a film formed by the pulse plasma CVD method has a high-quality film quality with excellent uniformity, so that the life of the seal ring can be greatly extended. As the DLC film becomes thicker, the sliding life tends to increase. However, if it is too thick, the manufacturing cost increases, and the film tends to crack or peel off. Therefore, it is important not to make the film thickness over 10 μm. It is.

(4) In any one of the above (1) to (3), it is preferable that the electrical resistance of the diamond-like carbon film is in the range of 10 ⁵ to 10 ⁸ Ω.

  This makes it difficult for the seal ring to be charged and makes it difficult for foreign matter to deposit, adhere and accumulate, so that an increase in sliding frictional resistance during continuous use for a long period of time is effectively prevented. Further, damage (scratching) of the DLC film due to foreign matter adhesion is effectively prevented.

Incidentally, the surface resistance of a DLC film formed by a general CVD method is usually about 10 ⁶ Ω. On the other hand, the surface resistance of the wrinkled DLC film shown in FIGS. 9A and 9B formed by the high frequency plasma CVD method is about 10 ¹² Ω.

  (5) In any one of the above (1) to (4), the base material may be a single resin or a composite material having a resin reinforced with inorganic fibers or inorganic particles.

  Ultra high molecular weight polyethylene (UHMW-PE), acrylonitrile butadiene styrene (ABS), polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyacetal (POM), polypropylene (PP), polyphenylene Any of sulfide (PPS), polyether ether ketone (PEEK), and phenyl formaldehyde (PF) is preferable.

  Carbon fiber or glass fiber can be used as the inorganic fiber serving as a reinforcing material. In addition, any of silica particles, alumina particles, zirconia particles, and silicon nitride particles can be used as the inorganic particles serving as a reinforcing material.

  (6) In any one of the above (1) to (4), the base material may include a rubber-based material.

  The base material of the O-ring and the bride ring as the seal ring can contain a rubber-based material. The rubber-based material may be used alone as a base material, or the rubber-based material may be reinforced with a reinforcing material such as inorganic fibers or inorganic particles.

  Nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), ethylene propylene rubber (EPDM), chloroprene rubber (CR), butyl rubber (IIR), urethane rubber (U), isoprene rubber (IR), Either silicon rubber (SiR) or fluororubber (FKM) is preferable.

  Acrylonitrile, butadiene, styrene (ABS), polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyacetal (POM), polypropylene (PP), polyphenylene sulfide (PPS), polyether ether ketone (resin) PEEK) and phenyl formaldehyde (PF) are preferred.

  Incidentally, a composite material of resin and glass fiber or a metal material can be used as a constituent material of the cylinder. Polycarbonate (PC), polyacetal (POM), ultra high molecular weight polyethylene (UHMW-PE), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene ether (PPE), polytetrafluoroethylene (PCT) as matrix resin for composite materials PTFE), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyarylate (PAR), polysulfone (PSF), polyetherimide (PEI), polyethersulfone (PES), polyamide (PA), polyimide ( PI) and polyamideimide (PAI) are preferred. As the metal material, duplex stainless steel (SUS 329J1) or super duplex stainless steel (SUS 329J4L) is preferable.

  Since the DLC film itself is excellent in self-lubricating properties, it is possible to reduce the coefficient of friction during sliding by coating, but since the film thickness is relatively thin, the seal ring comes into contact with the cylinder. The sliding surface of the cylinder that slides is preferably a smooth finished surface. Such a cylinder sliding surface is preferably finished to a surface roughness of a maximum height of 0.8 μm Rmax or more in order to smoothly slide the seal ring held in the outer peripheral groove of the piston. This is because the coefficient of friction with the DLC-coated seal ring is reduced to 0.1 or less by setting the surface roughness of the cylinder sliding surface to a maximum height of 0.8 μm Rmax or more.

Moreover, a metal material, a ceramic material, or an engineering plastic can be used for the constituent material of a piston and a rod. As the metal material, duplex stainless steel (SUS 329J1) or super duplex stainless steel (SUS 329J4L) is preferable. As the ceramic material, alumina (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), and sialon (SiAlON) are preferable. Engineering plastics include ultra high molecular weight polyethylene (UHMW-PE), polyphenylene ether (PPE), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyarylate (PAR), polysulfone (PSF) ), Polyetherimide (PEI), and polyethersulfone (PES) are preferable. The piston and rod are preferably made of the same material as much as possible.

  (7) The power recovery apparatus according to the present embodiment includes a cylinder into which pressure fluid is introduced or discharged, and a piston that is movably supported in the cylinder and reciprocally driven in the cylinder by receiving pressure from the pressure fluid. And a seal ring held in a groove that opens in a sliding surface that slides in contact with the cylinder, wherein the seal ring is liquid-tightly sealed An annular base material having deformability, and a diamond-like carbon film coated on at least a part of the base material by a pulse plasma CVD method and in direct contact with the sliding surface.

  In the power recovery device of this embodiment, since the high-quality DLC film coated by the pulse plasma CVD method is present on the base material of the seal ring, the cylinder / piston drive unit should be treated as maintenance-free for a long period of time. In addition to the above, it is possible to significantly reduce the driving energy of the piston by reducing the friction, and to achieve high efficiency of the power recovery device. Since the film formed by the pulse plasma CVD method has a high quality film quality excellent in uniformity, adhesion, and deformability, high recovery efficiency due to low friction can be maintained over a long period of time.

  (8) The seawater desalination apparatus according to the present embodiment includes a reverse osmosis membrane module having a reverse osmosis membrane for separating a solute contained in seawater, and seawater is added to the reverse osmosis membrane module in a state where pressure is applied to the seawater. A power recovery device having a piston and a piston for recovering the pressure of the concentrated water discharged from the reverse osmosis membrane module as power energy, and when the piston reciprocally slides in the cylinder A seal ring that slides in contact with either the sliding surface of the cylinder or the sliding surface of the piston, wherein the seal ring is deformed for liquid-tight sealing. And a diamond-like carbon film that is coated on at least a part of the base material by a pulse plasma CVD method and is in direct contact with the sliding surface. Characterized in that it has a.

  In the seawater desalination apparatus of this embodiment, since there is a high-quality DLC film excellent in low friction coefficient and wear resistance coated on the base material of the seal ring by the pulse plasma CVD method, the power recovery apparatus is It is possible to maintain high power recovery efficiency by handling maintenance for a long period of time. It becomes possible. Since the film formed by the pulse plasma CVD method has a high quality film quality with excellent uniformity, high recovery efficiency due to low friction can be maintained over a long period of time.

  (9) In the above (8), the pump may further include a seal ring covered with the diamond-like carbon film.

  In addition to the cylinder / piston drive part of the power recovery device, it is possible to extend the life of high-pressure pumps and low-pressure pumps that pump seawater to the RO membrane module.

  Further, the seawater desalination apparatus and power recovery apparatus are not only constantly in contact with high-pressure and high-concentration seawater, but are also periodically exposed to high-pressure acid and alkali solutions for cleaning the RO membrane. It is expected that organic substances such as rubber and resin are deteriorated in a short period of time because the molecular bonds are broken by such high-pressure water. Since the DLC film is not corroded by acid or alkali at all, the surface of the organic substance is not limited to the sliding part, and the life of the member composed of the organic substance is increased by blocking the acid, alkali and organic substance. Maintenance-free can also be achieved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  First, an outline of a seawater desalination apparatus including a power recovery apparatus 60 according to the first embodiment will be described with reference to FIG. In the seawater desalination apparatus 1, the pumped-up seawater is subjected to chemical treatment in the pretreatment system 10 and is fed to the safety filter 30 by the water pump 20. One of the seawater that has passed through the safety filter 30 is supplied to the high-pressure pump 40, and the other is supplied to the power recovery device 60. At this time, the pressure P3 of the seawater output from the safety filter 30 is about 0.2 MPa.

  The high pressure pump 40 pressurizes the supplied seawater and outputs it to the high pressure RO membrane module 50. At this time, the pressure P4 after the pressure increase varies depending on the type of the high-pressure RO membrane module 50, but is set to 6.0 MPa as a representative value here.

  The high-pressure RO membrane module 50 filters the supplied seawater. When the recovery rate of the high-pressure RO membrane module 50 is 40%, the high-pressure RO membrane module 50 discharges 40% of fresh water and 60% of high-concentration salt water (brine). At this time, the pressure of the fresh water is reduced to about 0.2 MPa (= P3), but the pressure P6 of the high-concentration salt water is about 5.8 MPa. Fresh water from the high-pressure RO membrane module 50 is supplied to the low-pressure pump 80, and the brine is supplied to the power recovery device 60.

  The fresh water from the high-pressure RO membrane module 50 is re-pressurized by the low-pressure pump 80 and passes through the low-pressure RO membrane module 90 to remove boron contained therein. Then, the fresh water that has passed through the low-pressure RO membrane module 90 is treated with chemicals in the water purification basin 100, and is supplied as purified water from the supply pump 110 to a home or the like.

  The power recovery device 60 uses the pressure energy contained in the high-concentration salt water to boost and output the seawater from the safety filter 30. Seawater from the power recovery device 60 merges with seawater from the high pressure pump 40 and is introduced into the high pressure RO membrane module 50.

  One end of the discharge valve 70 is open to the atmosphere. The discharge valve 70 controls the discharge flow rate of the brine whose pressure energy has been recovered by the power recovery device 60.

  Next, the configuration and operation of the power recovery device 60 will be described with reference to FIGS.

  As shown in FIG. 2, the power recovery device 60 includes a pressure adjustment valve 61, a 4-port switching valve 62, a pressure conversion unit 63, a seawater supply unit 64, rod position detection units 65 a to 65 d, and a control unit 66. . The pressure regulating valve 61 regulates the brine pressure led out to the 4-port switching valve 62 by restricting the brine flowing out from the high-pressure RO membrane module 50. The brine pressure P6 from the high-pressure RO membrane module 50 reduces the RO membrane by using the high-pressure RO membrane module 50 for a long period of time. The pressure adjustment valve 61 is used to adjust this decrease. Accordingly, the seawater pressure P14 output from the power recovery device 60 and the seawater pressure P4 output from the high-pressure pump 40 are always equal.

  The 4-port switching valve 62 switches the direction of inflow of brine into the pressure conversion unit 63 and discharge from the pressure conversion unit 63. The 4-port switching valve 62 switches the direction of inflow and discharge of brine in accordance with a switching instruction from the control unit 66. As a method for switching the 4-port switching valve 62, there are a pneumatic method, a hydraulic method, a hydraulic method, a method using a solenoid coil, and the like. As a water pressure source, brine, seawater from the water pump 20, or high-pressure salt water from the high-pressure pump 40 may be used.

  The pressure conversion unit 63 includes a pair of converters 63A and 63B. Since the converter 63A and the converter 63B have substantially the same structure, only one converter 63A will be described as a representative here. The converter 63A includes a cylinder 63s, a piston 63p, and a rod 63r.

  The cylinder 63s is made of a cylindrical glass fiber reinforced plastic (GFRP) having an inner diameter of about 200 mm and a stroke length of about 2 m, and forms a sealed space having three openings. One of epoxy resin, phenol resin, and unsaturated polyester resin is preferably used as the matrix resin of GFRP, which is a cylinder constituent material. Among these, epoxy resin is particularly preferable. This is because epoxy resins are excellent in strength, water resistance, and chemical resistance. Further, filament winding is preferable to sheet winding for GFRP for cylinders. This is because filament winding GFRP is more suitable for high-strength applications. In the apparatus of this embodiment, GFRP is used as the cylinder constituent material. However, the cylinder constituent material is not limited to this, and a carbon fiber reinforced plastic reinforced with carbon fiber may be used as the cylinder constituent material. Alternatively, a metal material such as duplex stainless steel (SUS 329J1, SUS 329J4L, etc.) may be used as the cylinder constituent material.

  One end of the rod 63r is joined to the piston 63p from the second space side, and the other end projects outside through the opening of the cylinder 63s. A sealing material (not shown) is attached to the periphery of the opening. Since the rod 63r is joined to the piston 63s from the second space side, the area A1 where the piston 63p faces the first space is different from the area A2 where the piston 63s faces the second space. Become. Here, the ratio between the area A1 on the first space side and the area A2 on the second space side is a solution of the area ratio calculated using a predetermined formula including two pressures P4 and P6 and two frictional forces. It is set in advance to match (numerical value). However, the pressure P4 is the pressure of seawater from the high-pressure pump 40, the pressure P6 is the pressure of high-concentration salt water from the high-pressure RO membrane 50, the friction force F1 is the friction force between the cylinder 63s and the piston 63p, and the friction force F2 is the cylinder This corresponds to the frictional force between 63s and the rod 63r.

  The seawater supply unit 64 includes check valves V1 to V4. The check valves V1 to V4 open and close independently depending on the surrounding pressure difference. Accordingly, seawater is supplied from the power recovery device 60 to the outside, or seawater is supplied to the pressure conversion unit 63.

  The two detectors 65a and 65b are position sensors for detecting the position of the rod 63r protruding from the first cylinder 63s. The first detector 65a is disposed at a position where the rod 63r can be detected when the piston 63p approaches the left end of the cylinder 63s (rod detectable position). The second detector 65b is arranged at a position where the rod 63r is not detected when the piston 63p approaches the right end of the cylinder 63s (rod non-detection position). The first detection unit 65 a detects the rod 63 r and outputs a detection signal to the control unit 66. The second detection unit 65b outputs a non-detection signal to the control unit 66 when the rod 63r is not detected. Thereby, the relative position of the piston 63p with respect to the cylinder 63s can be grasped.

  The 3rd and 4th detection parts 65c and 65d are the same composition as the 1st and 2nd detection parts 65a and 65b, and are for detecting the position of rod 63r projected from the 2nd cylinder 63s. It is a position sensor. The third detection unit 65 c detects the rod 63 r and outputs a detection signal to the control unit 66. The fourth detection unit 65d outputs the non-detection signal to the control unit 66 when the rod 63r is not detected. Thereby, the relative position of the piston 63p with respect to the cylinder 63s can be grasped.

  The control unit 66 outputs a switching signal to the 4-port switching valve 62 in accordance with signals sent from the four detection units 65a, 65b, 65c, and 65d. That is, when the control unit 66 receives detection signals from the first detection unit 65a and the fourth detection unit 65d, the first piston 63p is positioned in the vicinity of the left end of the first cylinder 63s in the drawing, It is determined that the second piston 63p is positioned in the vicinity of the right end of the second cylinder 63s in the drawing, so that the high-concentration salt water is drained from the first cylinder 63s and the high-concentration salt water is supplied into the second cylinder 63s. In addition, a switching signal is output to the 4-port switching valve 62.

  On the other hand, when the control unit 66 receives detection signals from the second detection unit 65b and the third detection unit 65c, the first piston 63p is positioned in the vicinity of the right end of the first cylinder 63s in the drawing, It is determined that the second piston 63p is positioned in the vicinity of the left end of the second cylinder 63s in the drawing, so that the high-concentration salt water is supplied into the first cylinder 63s and the high-concentration salt water is drained from the second cylinder 63s. In addition, a switching signal is output to the 4-port switching valve 62.

  Next, the operation of the power recovery device 60 will be described.

  In FIG. 2, the power recovery device 60 is in a state where brine is supplied to the first converter 63A and the brine is drained from the second converter 63B. Seawater from the safety filter 30 is supplied to the high-pressure pump 40 at a pressure of 0.2 MPa (= P3), and is introduced into the second space of the second cylinder 65s through the check valve V4.

  Seawater whose pressure is increased to 6.0 MPa (= P4) by the high-pressure pump 40 is merged with seawater from the power recovery device 60 and introduced to the primary side of the high-pressure RO membrane module 50. At this time, seawater from the power recovery device 60 is discharged from the second space of the first converter 63A and passes through the check valve V2. The high-pressure RO membrane module 50 discharges fresh water and brine.

  The brine discharged from the high-pressure RO membrane module 50 passes through the pressure regulating valve 61 and the 4-port switching valve 62 and flows into the first space of the first converter 63A. At this time, the second space of the first converter 63A is filled with seawater. The brine moves the piston 63p in the first cylinder 63s toward the second space, and discharges the seawater in the second space while pressurizing it.

  Here, if the area where the piston 63p faces the first space is A1, and the area where the piston 63s faces the second space is A2, the pressure P8 of the seawater discharged from the second space of the cylinder 63s is Using the brine pressure P7 from the 4-port switching valve 62, P8 = P7 × (A1 / A2). Thereby, the pressure P8 is equal to or slightly higher than the pressure P4 introduced into the high-pressure RO membrane module 50.

  Here, the states of the check valves V1 to V4 in FIG. 2 will be described below.

  Since the pressure P8> the pressure P3, the check valve V1 is closed. Further, since the pressure P8> the pressure P14, the check valve V2 is open. Here, the pressure difference between the pressure P8 and the pressure P14 can be considered as a pressure loss when seawater passes through the check valve V2.

  Further, since the pressure P14> the pressure P13, the check valve V3 is closed. Further, since one end of the discharge valve 70 is open to the atmosphere, the gauge pressure in the second space of the second cylinder 63s is almost zero. That is, P13 is a small pressure. Therefore, P3> P13 and the check valve V4 is open.

  Seawater from the safety filter 30 flows into the second space of the second cylinder 63s through the check valve V4. At this time, the first space of the second cylinder 63s is filled with brine. Here, since one end of the discharge valve 70 is open to the atmosphere, the gauge pressure in the first space of the second cylinder 63s is substantially zero. The seawater that has passed through the check valve V4 has a pressure of 0.2 MPa, and moves the piston 63p toward the first space in the second cylinder 63s. As the piston 63p moves toward the first space, the brine in the first space is discharged through the 4-port switching valve 62 and the discharge valve 70. The piston 63p slowly reciprocates within a cylinder 63s having a stroke length of about 2 m in a cycle of about 1 minute.

  When the above operation is continued, the piston 63p of the first converter 63A approaches the left end of the cylinder 63s, and the piston 63p of the second converter 63B approaches the right end of the cylinder 63s. Then, the 1st detection part 65a detects that the 1st rod 63r contacted, and the 4th detection part 65d detects that the 2nd rod 63r became non-contact. As a result, detection signals are output from the detection units 65a and 65d to the control unit 66, respectively. When each detection signal is input, the controller 66 outputs a control signal for switching the inflow direction and the discharge direction of the high-concentration salt water to the 4-port switching valve 62 based on the input signals. As a result, the power recovery device 60 enters the state shown in FIG. 3, and the inflow / discharge direction of the brine to the pressure conversion unit 63 is switched.

  In the present embodiment, the moving speed of the first piston 63p and the moving speed of the second piston 63p are made equal by opening and closing the discharge valve 70. As a result, the flow rate of the water pump 20 does not fluctuate with time and operates stably.

  In the power recovery device 60 shown in FIG. 3, the brine is supplied to the second converter 63B, and the brine is discharged from the first converter 63A.

  The brine discharged from the high-pressure RO membrane module 50 flows into the first space of the second cylinder 63s via the pressure adjustment valve 61 and the 4-port switching valve 62. At this time, the second space of the second cylinder 63s is filled with seawater. The brine moves the piston 63p toward the second space in the second cylinder 63s and discharges the seawater from the second space.

  Here, since the area where the second piston 63p faces the first space is A1, and the area where the second piston 63p faces the second space is A2, the second cylinder 63s has the second area. The pressure P13 of the seawater discharged from this space is P13 = P7 × (A1 / A2) using the brine pressure P7 from the 4-port switching valve 62. As a result, the pressure P13 is equal to or slightly higher than the pressure P4 introduced into the high-pressure RO membrane module 50.

  The check valves V1 to V4 in the state of FIG. 3 will be described.

  Since the pressure P13> the pressure P3, the fourth check valve V4 is closed. Further, since the pressure P13> the pressure P14, the third check valve V3 is open. Here, the pressure difference between the pressure P13 and the pressure P14 can be considered as a pressure loss when seawater passes through the second check valve V2.

  Further, since the pressure P14> the pressure P8, the second check valve V2 is closed. Since one end of the discharge valve 70 is open to the atmosphere, the gauge pressure in the second space of the first cylinder 63s is almost zero. That is, the pressure P8 is small. Therefore, P3> P8 and the first check valve V1 is open.

  Seawater from the safety filter 30 flows into the second space of the first cylinder 63s through the first check valve V1. At this time, the first space of the first cylinder 63s is filled with brine. Since one end of the discharge valve 70 is open to the atmosphere, the gauge pressure in the first space of the first cylinder 63s is almost zero. The seawater that has passed through the first check valve V1 has a pressure of 0.2 MPa, and moves the piston 63p toward the first space in the first cylinder 63s. As the piston 63p moves toward the first space, the brine is discharged from the first space.

  When the above operation is continued, the second piston 63p is close to the left end of the cylinder 63s, and the first piston 63p is close to the right end of the cylinder 63s. Then, the 3rd detection part 65c detects that the rod 63r contacted, and the 2nd detection part 65b detects that the rod 63r became non-contact. As a result, detection signals are output from the detection units 65b and 65c to the control unit 66, respectively. When each detection signal is input, the controller 66 outputs a control signal for switching the inflow direction and the discharge direction of the brine to the 4-port switching valve 62 based on the input signals. As a result, the power recovery device 60 returns to the state shown in FIG. 2, and the inflow / discharge direction of the brine to the pressure conversion unit 63 is switched.

  Next, the sliding part between the cylinder, piston, rod, and seal ring will be described with reference to FIGS.

  As shown in FIG. 4, a groove G1 is formed in the outer peripheral sliding surface 67a of the piston 63p, and an O-ring OR1 as a seal ring is inserted into the groove G1. The O-ring OR1 slightly protrudes from the groove G1 and is in contact with the sliding surface 67b of the cylinder 63s. A space (piston movement space) in the cylinder 63s is partitioned into a first space and a second space by the O-ring OR1. Brine is supplied from the high-pressure RO membrane module 50 to the first space on the right side in the figure, and seawater is supplied from the seawater supply unit 64 to the second space on the left side in the figure.

  As shown in FIG. 5, a bride ring BR1 is mounted on the outer periphery of the O-ring OR1. The bride ring BR1 is a protective member that is fitted on the outer periphery of the O-ring OR1, protects the O-ring OR1 as a strength member, and extends the life of the O-ring OR1. The outer peripheral surface of the O-ring OR1 is covered with a DLC film 69a. The DLC film 69b is also coated on the outer peripheral surface of the bride ring BR1. These DLC films 69a and 69b are formed using a pulse plasma CVD method or a high-frequency plasma CVD method, and have a film thickness of 1.3 μm and 2.1 μm, respectively. For film formation by the pulse plasma CVD method, a CVD film formation apparatus 120 shown in FIGS. 7 and 8 described later was used. The constituent material (base material) of the O-ring OR1 is nitrile rubber. The constituent material (base material) of the bride ring BR1 is high molecular polyethylene or carbon fiber filled PTFE resin. In the present embodiment, the DLC film is coated on the outer peripheral surface of the bride ring BR1, but the DLC film may also be coated on both sides and the periphery of the bride ring BR1 and the periphery of the O-ring.

  Two grooves G2 and G3 are formed on the sliding surface 68b of the cylinder 63s, an O-ring OR2 as a seal ring is inserted into one groove G2, and an O-ring OR3 as a seal ring is inserted into the other groove G3. Has been inserted. Bride ring BR3 is installed on the inner circumference of O-ring OR3. The bride ring BR3 is coated with a DLC film in the same manner as the above-described bride ring BR1. The bride ring BR3 is in contact with the DLC film so as to directly contact the sliding surface 68a of the rod 63r. On the other hand, the B-ring is not attached to the O-ring OR2, and the DLC film of the O-ring OR2 is in direct contact with the sliding surface 68a of the rod 63r.

  In this embodiment, the seal ring holding groove is formed on the sliding surface side of the outer periphery of the piston. However, the seal ring holding groove may be formed on the sliding surface side of the cylinder. In this embodiment, the seal ring holding groove is formed on the cylinder sliding surface side. However, the seal ring holding groove may be formed on the sliding surface side of the rod.

  Next, a high frequency plasma CVD method and a pulse plasma CVD method will be described as a thin DLC film formation process with reference to FIG.

  In the high-frequency plasma CVD method, as shown in FIG. 6A, low-energy film-forming components are sequentially stacked and deposited on the surface of a substrate. That is, in the high-frequency plasma CVD method, discharge plasma is generated above the base material, and the cations ionized by the film formation component gas in the discharge plasma are attracted to the base material by an electric field, and the film formation component is deposited on the base material. Let it be a membrane.

  In contrast, in the pulse plasma CVD method, as shown in FIG. 6 (b), a film forming component is allowed to enter the substrate with high energy. That is, in the pulse plasma CVD method, carbon ions are accelerated by a strong electric field generated by a high-pressure pulse, and are implanted into the substrate, and the film forming components (component atoms) are injected into the substrate.

[Film formation method and apparatus]
Next, an outline of the pulse plasma CVD method and apparatus used for coating the DLC film will be described with reference to FIGS.

  The characteristics of the pulse plasma CVD method are listed below.

1) Form a highly deformable film without residual stress
2) Low deposition temperature (60 ° C or less)
3) A high degree of vacuum is not required, and the film can be formed even on organic substances with many volatile components (low vacuum)
4) High film adhesion
5) Higher film hardness than high-frequency plasma CVD method and good wear resistance. Because of the above features, seawater desalination equipment and power recovery equipment sliding parts according to pulse plasma CVD method Thus, a low-friction, wear-resistant (long life), high adhesion, high toughness, and low-cost DLC film can be obtained with respect to organic material members such as rubber and resin.

  Such a film formation process of the pulse plasma CVD method is performed using a pulse plasma film formation apparatus 120 shown in FIG. The pulse plasma film forming apparatus 120 has two power sources 126 and 127. That is, two are a high-frequency power source 126 and a high-voltage pulse power source 127. Two powers (high-frequency power and high-voltage pulse power) supplied separately from these two power sources 126 and 127 are superimposed by a matching circuit of the superimposing device 128, and the superimposing power is applied to the electrodes 123 and 124 in the vacuum chamber 121 through the feedthrough 125. Then, intermittent pulse plasma discharge 129 is generated around the electrodes 123 and 124. A film forming gas is supplied into the vacuum chamber 121 from a gas supply source (not shown).

  As shown in FIG. 8, a cylindrical auxiliary electrode 124 is erected on a plate-like base electrode 123, and a plurality of workpieces 122 (O link or bright link) are mounted on the auxiliary electrode 124. The outer diameter of the auxiliary electrode 124 is substantially equal to the inner diameter of the work 122, and the work 122 is fitted in a state of being in contact with the outer peripheral surface of the auxiliary electrode 124. When high frequency power is applied to the electrodes 123 and 124, a discharge plasma 129 is generated so as to surround the electrodes 123 and 124 and the workpiece 122. At this time, the source gas such as methane is ionized and ionized, and the surface of the workpiece 122 is covered with carbon ions. Thereafter, when the high-frequency power is turned off and the high-pressure pulse power is applied, the ionized component of the source gas is accelerated in the direction of the substrate by a strong electric field. By repeating this process at predetermined intervals, a DLC film in which a soft film and a hard film are laminated can be formed. Furthermore, it is difficult to suppress the occurrence of pinhole defects in thin film coatings such as CVD by changing the conditions from the initial film formation conditions to stacking two, three or four or more layers. By providing an interval for turning off both the high frequency power and the high voltage pulse power, the pinhole generated in the first layer is closed and the total thickness of the DLC film is increased to 2.0 μm or more.

[Microstructure of DLC film formed by high-frequency plasma CVD method]
A DLC film was coated on each of four types of rubber-based and resin-based materials such as ethylene propylene rubber (EP rubber), nitrile rubber (NBR rubber), silicon rubber, and epoxy resin by a high-frequency plasma CVD method.

  A coating test was conducted using a mixed gas of argon and methane as a film forming gas.

  Among the various samples, DLC coating was possible on EP rubber and silicon rubber base material, but nitrile rubber with many volatile components could not be coated. As a representative example, a DLC coating film formed on an EP rubber substrate was photographed at a magnification of 20,000 times using a scanning electron microscope (SEM).

  As shown in FIG. 9A, the surface of the DLC film coated on the EP rubber by the high-frequency plasma CVD method is uneven.

  As shown in FIG. 9B, when a cross section of the sample film is observed, DLC particles having a uniform particle diameter are observed inside, and a DLC columnar structure is developed in the surface layer portion.

[Microstructure of DLC film formed by pulsed plasma CVD method]
Similarly, a DLC film was coated by a pulse plasma CVD method on four types of rubber materials and resin materials such as ethylene propylene rubber (EP rubber), nitrile rubber (NBR rubber), silicon rubber, and epoxy resin.

  A superimposed power obtained by superimposing a high frequency power of about 14 MHz and a high voltage pulse power of about 10 kV, which was subjected to a coating test using a mixed gas of argon, methane, and toluene as a film forming gas, was applied to the electrodes.

  The formed DLC coating film was photographed at a magnification of 20,000 times using a scanning electron microscope (SEM). The average film thickness of the DLC coating film was 2.1 μm.

  As shown in FIG. 10, the DLC film coated on the silica particle-dispersed epoxy resin by the pulse plasma CVD method has a smoother surface than the film formed by the high-frequency plasma CVD method, and is a dense and excellent in uniformity. It was a membrane with tissue.

[Microstructure of Comparative Example Sample Film]
Two types of comparative DLC films were coated on an aluminum substrate by a high-frequency plasma CVD method. Two DLC coating films of comparative examples were photographed at a magnification of 20,000 times using a scanning electron microscope (SEM).

  As shown in FIG. 11A, cracks occurred in the DLC film of Comparative Example 1.

  As shown in FIG. 11B, cracks were also generated in the DLC film of Comparative Example 2.

  Incidentally, when the hardness of the film was examined, the film of Comparative Example 1 had a Vickers hardness Hv60, and the film of Comparative Example 2 had a Vickers hardness Hv984.

[Compression deformation test of DLC film]
The DLC coating film is compressed and deformed using the compression deformation test shown in FIG. 12, and the surface of the film after the compression deformation is observed with a scanning electron microscope to check whether the film is cracked or peeled. The deformation performance was evaluated. A sample obtained by coating an O-ring with a DLC film was used.

  As shown in FIG. 12A, an O-ring 141a as a sample is placed on a fixed base, a compression jig 140 is overlaid on the O-ring 141a, and the O-ring 141a is compressed via the compression jig 140. Apply force. The initial diameter of the O-ring 141a is about 5 mm.

  As shown in FIG. 12B, under the first pressure, the O-ring 141a is compressed and deformed until it becomes 0.5 mm thinner than the initial thickness.

  As shown in FIG. 12C, in the second reduction, the O-ring 141b deformed by the previous reduction is compressed and deformed until it becomes 1.0 mm thinner than the initial thickness.

  The film surface of the bridging ring 141c after compressive deformation is observed with a scanning electron microscope, and it is examined whether or not the film is cracked or peeled. In this way, the deformability of the DLC film can be evaluated.

  The DLC film formed by the general high-frequency plasma CVD method by the above-described compression deformation test was peeled when it was compressed and deformed until it became 0.5 mm thinner than the initial thickness. In the DLC film (FIG. 9) and the DLC film (FIG. 10) formed by the pulse plasma method, no crack or peeling occurred in any of the sample films.

[DLC film friction coefficient measurement test]
Next, the coefficient of friction was measured using an O-ring test piece coated with DLC by a high-frequency plasma CVD method and a pulse plasma method.

  As shown in FIG. 13, the friction coefficient was measured by fixing a DLC-coated O-ring test piece around two metal disks, and installing a GFRP plate as a piston material between them. At that time, the O-ring was subjected to compressive deformation of 0.5 mm and 1.0 mm by adjusting the position of the metal disk. Thereafter, the friction coefficient was calculated from the driving force when the GFRP plate was moved. In addition, the test was made into 1 cycle when the board made from GFRP was reciprocated, and the test was performed to 100 cycles.

  The test results are shown in FIGS. 14 (a) and 14 (b).

  When the amount of compressive deformation is 0.5 mm, as shown in FIG. 14 (a), no significant change is observed in the friction coefficient up to 100 cycles in both cases, but when the amount of compressive deformation is 1.0mm, ), A significant increase in the friction coefficient was confirmed in the O-ring coated with DLC by the high-frequency plasma CVD method. Since the DLC coating is almost completely worn out after the test, it is presumed that the hardness of the film is low. on the other hand. The OLC test piece DLC-coated by the pulse plasma method showed almost no change in the coefficient of friction even after 100 cycles.

1 ... seawater desalination equipment, 40 ... high pressure pump,
50, 90 ... reverse osmosis membrane module (RO membrane module), 80 ... low pressure pump,
60 ... Power recovery device,
61 ... Pressure adjusting valve, 62 ... Switching valve,
63 ... Pressure converter, 63A, 63B ... Converter, 63s ... Cylinder, 63p ... Piston, 63r ... Rod,
64 ... Seawater supply part, 65a-65d ... Detection part, 66 ... Control part,
67a ... piston sliding surface, 67b ... cylinder sliding surface,
68a ... Rod sliding surface, 68b ... Cylinder sliding surface,
69a, 69b ... DLC film (coating film),
OR1, OR2, OR3 ... O-ring (seal ring),
BR1, BR3 ... Bride ring (seal ring),
G1, G2, G3 ... groove,
120 ... Pulse plasma deposition system, 121 ... Chamber, 122 ... Work (O-link, Bright-link), 123 ... Base electrode, 124 ... Auxiliary electrode, 125 ... Feed-through, 126 ... High frequency power supply, 127 ... High voltage pulse power supply, 128 ... superimposition device, 129 ... generated plasma,
140: compression jig, 141a, 141b, 141c ... O-ring.

Claims (9)

A seal ring that is used in contact with a sliding surface on which a piston and cylinder to be reciprocated slide, or in contact with a sliding surface on which a piston rod and cylinder slide,
An annular base material with deformability for liquid-tight sealing;
A diamond-like carbon film that is coated on at least a part of the substrate by a pulse plasma CVD method and is in direct contact with the sliding surface;
A seal ring characterized by comprising:   The seal ring according to claim 1, wherein a plurality of diamond-like carbon films are laminated and coated in a plurality of times on the base material.   The seal ring according to claim 1 or 2, wherein the diamond-like carbon film has a thickness of 1 µm or more, preferably 2 µm or more. The seal ring according to any one of claims 1 to 3, wherein an electric resistance of the diamond-like carbon film is in a range of 10 ⁵ to 10 ⁸ Ω.   The seal ring according to any one of claims 1 to 4, wherein the base material is made of a single resin or a composite material having a resin reinforced with inorganic fibers or inorganic particles.   The seal ring according to claim 1, wherein the base material includes a rubber-based material. A cylinder into which pressure fluid is introduced or discharged; a piston that is movably supported in the cylinder and that is driven to reciprocate within the cylinder under pressure from the pressure fluid; and the piston that slides in contact with the cylinder A power recovery device comprising: a seal ring held in a groove that opens in a sliding surface.
The seal ring is
An annular base material with deformability for liquid-tight sealing;
A diamond-like carbon film that is coated on at least a part of the substrate by a pulse plasma CVD method and is in direct contact with the sliding surface;
A power recovery device comprising: A reverse osmosis membrane module having a reverse osmosis membrane for separating a solute contained in seawater, a pump for supplying seawater to the reverse osmosis membrane module with pressure applied to the seawater, and discharged from the reverse osmosis membrane module A power recovery device having a cylinder and a piston for recovering the pressure of the concentrated water as power energy, and a sliding surface of the cylinder or a sliding surface of the piston when the piston reciprocates in the cylinder. A seawater desalination apparatus comprising a seal ring that contacts and slides on any of the above,
The seal ring is
An annular base material with deformability for liquid-tight sealing;
A diamond-like carbon film that is coated on at least a part of the substrate by a pulse plasma CVD method and is in direct contact with the sliding surface;
A seawater desalination apparatus characterized by comprising:   The seawater desalination apparatus according to claim 8, wherein the pump further includes a seal ring covered with the diamond-like carbon film.

Images