US3692054A - Pneumatic relay - Google Patents

Pneumatic relay Download PDF

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Publication number
US3692054A
US3692054A US9853A US3692054DA US3692054A US 3692054 A US3692054 A US 3692054A US 9853 A US9853 A US 9853A US 3692054D A US3692054D A US 3692054DA US 3692054 A US3692054 A US 3692054A
Authority
US
United States
Prior art keywords
valve
stem
valve plug
plug
cavity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US9853A
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English (en)
Inventor
Melvin Lawrence Buls
Gerald Frank Varnum
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fisher Controls International LLC
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Fisher Controls International LLC
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Filing date
Publication date
Application filed by Fisher Controls International LLC filed Critical Fisher Controls International LLC
Application granted granted Critical
Publication of US3692054A publication Critical patent/US3692054A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K31/00—Actuating devices; Operating means; Releasing devices
    • F16K31/12—Actuating devices; Operating means; Releasing devices actuated by fluid
    • F16K31/126—Actuating devices; Operating means; Releasing devices actuated by fluid the fluid acting on a diaphragm, bellows, or the like
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/2278—Pressure modulating relays or followers
    • Y10T137/2365—Plural series units
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/87169—Supply and exhaust
    • Y10T137/87217—Motor
    • Y10T137/87225—Fluid motor

Definitions

  • An adjustable gain pilot relay incorporates a body member having a pair of axially aligned valve seats therein and a valve plug coacting with each valve seat and supported by flexures which center the valve plugs relative to the valve seats and which hold the valve plugs in their operating positions.
  • the valve plugs are adjustable relative to one another and to the valve seats in a novel manner such that both ports may be open at a steady-state condition, both valve ports may be closed at a steady-p1ate condition, or that some travel of the exhaust valve stem relative to the relay housing is necessary to open either valve port. Thereby adjustment of the relay gain is made.
  • the new and improved pilot relay of this invention is used as the power amplifier in a positioner mechanism which controls the position of an actuator.
  • An input signal to the positioner creates a pressure condition to the input section of the relay resulting in a change in pressure to the actuator.
  • the actuator motion is transferred by a series of levers and springs which provides a feedback force to the input element of the positioner which balances the new input force.
  • a pilot relay of a type to which the present invention generally relates is provided with a housing having a supply inlet, an exhaust outlet, an outlet opening communicating with the actuator, and a signal opening communicating with an electro-pneumatic valve positioner, as for example, a torque motor beam which is responsive to an electrical signal for regulating the output from a nozzle.
  • Valve plug means are reciprocal in the cavity or chamber of the valve housing.
  • a standard double poppet valve is employed, with a diaphragm or like means being used to adjust the poppet valve so as to selectively position the valve elements between (I) a first position wherein the inlet is closed and the outlet is open, (2) a second position wherein the outlet is closed and the inlet is open and (3) an intermediate or steady-state position wherein both the inlet and the outlet are open for venting the supply pressure to atmosphere so as to maintain the required pressure necessary to position the stern in the actuator.
  • a limitation of the standard double poppet valve is that it usually comprises a single piece carrying lands which contact the inlet and outlet valve seats, with no means for adjusting the position of the two plugs relative to one another.
  • An object of the present invention is to provide an improved pilot relay which incorporates a pair of aligned valve plugs movable toward and away from a pair of aligned seats, with novel flexure means being provided to support the valve plugs within the valve housing.
  • Another object of the present invention is to provide an improved pilot relay wherein the location of the valve plugs with respect to one another and to their valve seats may be adjusted in a simple manner thereby creating a new relay gain or ratio of input signal pressure to output pressure.
  • Still another object of this invention is to provide an improved pilot relay wherein a pair of aligned valve plugs are flexure mounted, and wherein the supply valve stem is adjustable so as to permit valve travel to be more precise than would be economically possible if reliance were had on dimensional tolerances alone.
  • Yet another object of this invention is to provide an improved pilot relay which is economical to manufacture and reliable in use. Other objects and advantages of the present invention will become more apparent hereinafter.
  • FIG. 1 there is illustrated schematicallya system incorporatingthe pilot relay of the present invention.
  • an actuator 10 which includes a housing having therein a pressure responsive element 12 as, for example, a diaphragm, which is adapted to be connected to an actuating stem or rod for positioning a valve in a conduit (not shown) to regulate fluid flow therethrough.
  • a spring 16 disposed concentrically about the rod 14 acts against the diaphragm 12 in opposition to the pressure in the chamber above the diaphragm.
  • Positioner 20 comprises a torque motor 22 having an armature 24 which is adapted to be positioned so as to control the bleed of fluid pressure from a nozzle opening 26.
  • the torque motor 22 responds to a direct current milliampere input signal and causes the armature 24 to pivot about axis 21.
  • Feedback means 27, which will be more fully described hereinafter, are operative between the actuating stem 14 of the actuator 10 and the armature 24 of the torque motor 22.
  • the pilot relay 30 (FIGS. 1 and 2) of the present invention comprises a housing 32 which has a supply inlet opening 34 therein connected to a supply conduit 36 that is in turn communicated with a source of supply pressure. Disposed within housing 32 is a cavity or chamber 38 which communicates with the supply inlet opening 34 by means of an internal passageway 40 in housing 32.
  • a seat ring assembly 42 which has defined thereon a pair of valve seats 44 and 46, is located in cavity or chamber 38. O-rings are provided to seal between the seat ring assembly 42 and the walls of chamber 38. Valve members or valve plugs 43 and 45 are adapted to cooperate with the valve seats or ports 44 and 46. Each of the valve members 43, 45 is retained in an operating position and centered with respect to the ports 44 and 46 by flexure members or flexures 48 and 50, respectively. Each of the valve plugs 43 and 45 is secured, such as by spot welding, to flexures 48 and 50, respectively.
  • each of the flexures 48 and 50 is secured, such as by spot welding, to the seat ring assembly 42.
  • the supply valve stem 52 is threadedly engaged with the supply valve member 45 and is adapted to extend through a central passage in the seat ring assembly 42 and abut the end of the exhaust valve stem 54 extending through the exhaust valve member 43.
  • the valve member 43 is slidable with respect to the exhaust valve stem 54 and is biased against the shoulder of the exhaust valve stem 54, as viewed in FIG. 1, by means of the spring 56.
  • the seat ring assembly 42 is maintained in place by corrugated spring washer 53 which acts between the cover 31 which is affixed to and forms a part of housing 32 and special washer 51, which may be made from an aluminum alloy.
  • a diaphragm or pressure responsive member 60 is also provided in the cavity or chamber 38 within the housing 32.
  • the pressure responsive member 60 is biased upwardly, as viewed in FIG. 1, by the resilient means or spring 61 which acts against the pressure in the chamber 62 defined between the top of the diaphragm 60 and the interior wall of the housing 32.
  • a diaphragm or pressure responsive member 60 is also provided in the cavity or chamber 38 within the housing 32.
  • the pressure responsive member 60 is biased upwardly, as viewed in FIG. 1, by the resilient means or spring 61 which acts against the pressure in the chamber 62 defined between the top of the diaphragm 60 and the interior wall of the housing 32.
  • a nozzle restriction and adaptor assembly 70 is provided in the housing member 32 within passage 40 for reducing the supply pressure supplied to the nozzle passage 77 from supply conduit 36.
  • An O-ring seal is disposed about the assembly 70 to seat between the assembly 70 and housing 32 and prevent communication between passages 40 and 77 except through assembly 70.
  • Conduit 72 communicates with supply inlet opening 34 through an internal passage in assembly 70 and signal opening 77.
  • the chamber 62 above the diaphragm 60 communicates with the nozzle 26 of the torque motor assembly 22 via signal'opening 77 and conduit 72.
  • output chamber 41 within seat ring assembly 42 connects to actuator through a passage 73 in the housing 32, the outlet opening 74 and a conduit 75 that communicates outlet opening 74 with the chamber 13 above the diaphragm 12 in actuator 10.
  • Flexure 48 comprises a thin disc-like member made from metal, for example, spring tempered stainless steel and being cut out with generally Y-shaped recesses 80, 81 and 82 which provide intermediate supports 84, 85, and 86 for the central portion 88.
  • the thickness of the flexure 48 is on the order of 00045-00055 inch.
  • the central position 88 has an opening 89 for receiving and holding a valve plug.
  • the central portion 88 can move or flex axially relative to the outer ring-like portion, yet it will not rotate about the axis of the flexure.
  • a valve plug held in the central portion 88 of the flexure 48 such as by spot welding can be centered with respect to its associated valve seat.
  • the flexure 48 can be retained within the pilot relay 30 such that it will tend to maintain the valve plug 43 carried thereon in a desired position, for example, an operating position.
  • Supply air flows from the conduit 36 through passage 40, open port 46, output chamber 41, passage 73 and conduit 75, to increase the output pressure to the chamber 13 above the diaphragm 12 in the actuator 10, moving the actuating stem or actuator rod 14 downward, as viewed in FIG. 1.
  • the increased nozzle pressure on the relay diaphragm 60 forces the exhaust valve stem 54 downward, moving the exhaust valve plug 43 toward the exhaust valve seat 44 and moving the supply valve plug 45 away from the supply valve seat 46.
  • the resulting throttling action permits a larger volume of fluid, for example, air to flow into the output chamber 41 through the supply port 46 than from the output chamber 41 through the exhaust port 44. This increases the output pressure to the chamber 13 above the diaphragm 12 and forces the actuating stem 14 to move downward.
  • actuating stem 14 is fed back to the armature 24 of the torque motor 22 by a mechanical linkage means 27 which includes links 27a, 27b, 27c and 27d.
  • Link 27a is fixedly secured at one end to the actuating rod 14. The free end of link 27a is pivoted on link 27b.
  • Link 27b pivots at the other end on link 270 which is pivoted on a support.
  • Link 270 cooperates with link 27d which is pivoted on a support.
  • a feedback spring 28 acts between the other end of link 27d and armature 24. The resultant feedback motion causes the armature 24 to rotate away from the nozzle 26. Nozzle pressure at nozzle opening 26 decreases, reducing the pressure in the chamber 62 and thereby reducing the downward force on the exhaust valve stem 54.
  • the spring 61 will bias the diaphragm 60 upwardly and permit the lower flexure 50 to move the supply valve plug 45 toward the supply valve seat 46 and the upper flexure 48 to move the exhaust valve plug 43 away from the exhaust valve seat 44, causing the flow through both ports 44 and 46 to be equal and preventing any further increase in output pressure.
  • the actuator is once again at steady-state, but at a higher input signal and a new actuating stem 14 position.
  • the reduced downward force on the exhaust valve stem 54 permits the lower flexure 50 to move the supply valve plug 45 toward the supply valve seat 46 and the upper flexure 48 to move the exhaust valve plug 43 away from the exhaust valve seat 44.
  • the resulting throttling action allows a larger volume of air to flow from the output chamber 41 through the exhaust port 44 than into the output chamber 41 through the supply port 46.
  • This decreases the output pressure to the actuator diaphragm 12 in the actuator 10 and permits the actuator stem 14 to move upward.
  • Actuating stem .14 movement is fed back to the armature 24 by the mechanical linkage 27 to reposition the armature 24.
  • the exhaust valve plug 43 moves toward the exhaust valve seat 44 and the supply valve plug 45 moves away from the supply valve seat 46, establishing equal flow rates through both ports. This prevents any further decrease in output pressure and results in steady-state conditions.
  • FIGS. 4a, 4b, 4c, 4d, and 4e there is illustrated the various positions of the valve plugs 43 and 45 during operation of the relay 30.
  • the supply valve plug 45 is closed, the exhaust valve plug 43 is fully open, and there is maximum exhaust of pressure to the atmosphere through opening 69.
  • FIG. 4b the supply valve plug 45 is closed, the exhaust valve plug 43 is fully open, and there is maximum exhaust of pressure to the atmosphere through opening 69.
  • FIG. 4c illustrates an intermediate position wherein both the supply valve plug 45 and the exhaust valve plug 43 are open.
  • FIG. 4d illustrates the exhaust valve plug 43 just closed and the supply valve plug 45 open somewhat and
  • FIG. 4e illustrates the position of maximum supply with the supply valve plug 45 fully open and the exhaust valve plug 43 closed.
  • Another feature of this invention is the means for adjusting the effective length of the supply valve stem 52, so as to adjust the position of the valve plugs 43 and 45 relative to one another and to their valve seats to accommodate manufacturing tolerance considerations as well as to provide for adjustment of the valve plug positions thereby changing the operating gain of the relay 30.
  • the flexures 48 and 50 are secured to the valve plugs 43 and 45 so as to retain same in a centered relationship with respect to the valve seats 44 and 46, respectively.
  • the flexures 48 and 50 serve as springs to bias the valve plugs vertically upward toward their operating positions.
  • Another function is served by the flexure 50, namely, to provide an antirotation means so as to hold the valve plug 45 and enable rotation of the valve stem 52 relative to the valve plug to which it is threadedly secured.
  • the effective length of the valve stem 52 can be changed such that both ports 44 and 46 may be open at a steady-state condition, both ports may be closed at a steadystate condition, or that some travel of the exhaust valve stem 54 relative to the relay housing 32 is necessary to open either valve port. Thereby adjustment of the relay gain is made.
  • the valve stem 52 is adjusted such that both ports are open at a steady-state condition.
  • the resulting continuous bleed determines the sensitivity of the relay 30 for small variations about the steady state condition.
  • an improved adjustable gainpneumatic pilot relay which produces improved performance in a system as shown, for example, in FIG. 1 of the application.
  • Incorporated within the improved pneumatic relay or power amplifier are a pair of valve plugs which are flexure mounted so as to maintain the alignment of the valve plugs with their respective valve seats and to hold the valve plugs in their operating positions.
  • the supply valve stem is adjustably connected to the supply valve plug so as to enable adjustment of the effective length of the supply valve stem and, therefore, the distance between the two valve plugs.
  • a simplified arrangement is thereby prosary to open either valve port. Thereby adjustment of the relay gain is made.
  • a pilot relay comprising a housing having a cavity therein, means defining a pair of valve seats, means defining a supply inlet into said cavity and adapted to communicate with a source of supply fluid pressure, means defining an exhaust outlet from said cavity and adapted to be vented to the atmosphere, means defining an outlet passage from said cavity, means defining a signal passage from said cavity, said valve seats being aligned with one another, the first valve seat being disposed between the supply inlet and the outlet passage, the second valve seat being disposed between the outlet passage and the exhaust outlet, first and second valve means disposed in the cavity for selectively opening and closing the valve seats, flexures supporting the first and second valve means and centering them with respect to the valve seats, pressure responsive means operatively connected to the second valve means, each valve means comprising a valve plug and a stem, the first stem abutting the second stem, the second valve plug being slidable on the second stem, the first stem being adjustably secured to the first valve plug to permit adjustment of the first valve plug relative to the second valve plug

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Multiple-Way Valves (AREA)
  • Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
  • Control Of Fluid Pressure (AREA)
US9853A 1970-02-09 1970-02-09 Pneumatic relay Expired - Lifetime US3692054A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US985370A 1970-02-09 1970-02-09

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US3692054A true US3692054A (en) 1972-09-19

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Application Number Title Priority Date Filing Date
US9853A Expired - Lifetime US3692054A (en) 1970-02-09 1970-02-09 Pneumatic relay

Country Status (8)

Country Link
US (1) US3692054A (nl)
JP (1) JPS5425190B1 (nl)
BE (1) BE762642A (nl)
CA (1) CA931854A (nl)
DE (1) DE2105776C2 (nl)
FR (1) FR2079328B1 (nl)
GB (1) GB1294282A (nl)
NL (1) NL162759C (nl)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3994311A (en) * 1973-10-15 1976-11-30 Tangen Drives, Inc. Pneumatic amplifier
US4726395A (en) * 1983-03-17 1988-02-23 Kunkle Valve Company, Inc. Flexible guide
EP0833239A2 (en) * 1992-09-09 1998-04-01 Fisher Controls International, Inc. Pneumatic pressure relay
US6443183B1 (en) * 2000-06-07 2002-09-03 Transcend Inc. Valve and assembly for axially movable members
US20050229775A1 (en) * 2004-04-16 2005-10-20 Fisher Controls International Llc Asymetric volume booster arrangement for valve actuator
US20060172924A1 (en) * 2004-08-31 2006-08-03 Winslow Robert M Methods to enhance hemodynamic stability using oxygen carrying compositions
CN101968118A (zh) * 2009-07-28 2011-02-09 丹佛斯（天津）有限公司 膨胀阀及其膜片支撑结构
US20120061606A1 (en) * 2010-09-15 2012-03-15 Fisher Controls International Llc Volume booster with variable asymmetry
US20120260993A1 (en) * 2011-04-01 2012-10-18 General Equipment And Manufacturing Company, Inc., D/B/A Topworx, Inc. Poppet valve assembly for controlling a pneumatic actuator
US9074695B2 (en) 2010-09-15 2015-07-07 Fisher Controls International Llc Volume booster with discrete capacity adjustment
CN107246498A (zh) * 2017-07-26 2017-10-13 中国长江电力股份有限公司 一种供水系统减压阀用双先导阀控制系统及控制方法

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3911238A (en) * 1973-12-06 1975-10-07 Automatic Switch Co Condition responsive control device with capacity for independent adjustment of control points and transducer therefor
DE2809554C2 (de) * 1978-03-06 1984-09-20 Wabco Westinghouse Fahrzeugbremsen GmbH, 3000 Hannover Relais-Ventil
DE3120203A1 (de) * 1981-05-21 1982-12-23 Wabco Westinghouse Fahrzeugbremsen GmbH, 3000 Hannover Relaisventil
DE102011108177B4 (de) * 2011-07-22 2013-03-21 Festo Ag & Co. Kg Ventilmodul

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1887322A (en) * 1928-09-29 1932-11-08 Lewis L Nettleton Valve for controlling fluid pressure
US2912006A (en) * 1956-03-12 1959-11-10 Gen Gas Light Co Valve structure
US2919711A (en) * 1958-03-19 1960-01-05 United Aircraft Prod Tank pressurizing in aerial craft
US3105508A (en) * 1960-03-29 1963-10-01 Foxboro Co Pneumatic relay
US3548879A (en) * 1968-11-12 1970-12-22 Teldix Gmbh Three-way valve

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2919716A (en) * 1955-06-29 1960-01-05 Elliott Brothers London Ltd Valves
US3004526A (en) * 1958-11-20 1961-10-17 Fairchild Stratos Corp Pressure controlled positioner
US3195416A (en) * 1962-04-16 1965-07-20 Security Valve Company Of Cali Pilot or relay valve
US3548979A (en) * 1969-02-24 1970-12-22 Goodyear Tire & Rubber Brake element with high heat sink characteristics

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1887322A (en) * 1928-09-29 1932-11-08 Lewis L Nettleton Valve for controlling fluid pressure
US2912006A (en) * 1956-03-12 1959-11-10 Gen Gas Light Co Valve structure
US2919711A (en) * 1958-03-19 1960-01-05 United Aircraft Prod Tank pressurizing in aerial craft
US3105508A (en) * 1960-03-29 1963-10-01 Foxboro Co Pneumatic relay
US3548879A (en) * 1968-11-12 1970-12-22 Teldix Gmbh Three-way valve

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3994311A (en) * 1973-10-15 1976-11-30 Tangen Drives, Inc. Pneumatic amplifier
US4726395A (en) * 1983-03-17 1988-02-23 Kunkle Valve Company, Inc. Flexible guide
EP0833239A2 (en) * 1992-09-09 1998-04-01 Fisher Controls International, Inc. Pneumatic pressure relay
EP0833239A3 (en) * 1992-09-09 1998-12-23 Fisher Controls International, Inc. Pneumatic pressure relay
US6443183B1 (en) * 2000-06-07 2002-09-03 Transcend Inc. Valve and assembly for axially movable members
US7458310B2 (en) * 2004-04-16 2008-12-02 Fisher Controls International Llc Asymmetric volume booster arrangement for valve actuator
US20080276798A1 (en) * 2004-04-16 2008-11-13 Fisher Controls International Llc Asymmetric Volume Booster Arrangement for Valve Actuators
US20050229775A1 (en) * 2004-04-16 2005-10-20 Fisher Controls International Llc Asymetric volume booster arrangement for valve actuator
US7845268B2 (en) 2004-04-16 2010-12-07 Fisher Controls International Llc Asymmetric volume booster arrangement for valve actuators
US20060172924A1 (en) * 2004-08-31 2006-08-03 Winslow Robert M Methods to enhance hemodynamic stability using oxygen carrying compositions
CN101968118B (zh) * 2009-07-28 2014-07-30 丹佛斯（天津）有限公司 膨胀阀及其膜片支撑结构
CN101968118A (zh) * 2009-07-28 2011-02-09 丹佛斯（天津）有限公司 膨胀阀及其膜片支撑结构
US9074695B2 (en) 2010-09-15 2015-07-07 Fisher Controls International Llc Volume booster with discrete capacity adjustment
US9032986B2 (en) * 2010-09-15 2015-05-19 Fisher Controls International Llc Volume booster with variable asymmetry
US20120061606A1 (en) * 2010-09-15 2012-03-15 Fisher Controls International Llc Volume booster with variable asymmetry
US20120260993A1 (en) * 2011-04-01 2012-10-18 General Equipment And Manufacturing Company, Inc., D/B/A Topworx, Inc. Poppet valve assembly for controlling a pneumatic actuator
US9279433B2 (en) * 2011-04-01 2016-03-08 General Equipment And Manufacturing Company, Inc. Poppet valve assembly for controlling a pneumatic actuator
CN107246498A (zh) * 2017-07-26 2017-10-13 中国长江电力股份有限公司 一种供水系统减压阀用双先导阀控制系统及控制方法
CN107246498B (zh) * 2017-07-26 2023-10-20 中国长江电力股份有限公司 一种供水系统减压阀用双先导阀控制系统及控制方法

Also Published As

Publication number Publication date
NL162759C (nl) 1980-06-16
NL162759B (nl) 1980-01-15
JPS5425190B1 (nl) 1979-08-25
BE762642A (fr) 1971-08-09
GB1294282A (en) 1972-10-25
DE2105776C2 (de) 1982-08-19
CA931854A (en) 1973-08-14
FR2079328B1 (nl) 1975-01-17
FR2079328A1 (nl) 1971-11-12
NL7101545A (nl) 1971-08-11
DE2105776A1 (de) 1971-08-19

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