ES2018280B3 - Procedimiento y dispositivo de encamisado de un tubo periferico de un generador de vapor. - Google Patents

Procedimiento y dispositivo de encamisado de un tubo periferico de un generador de vapor.

Info

Publication number
ES2018280B3
ES2018280B3 ES87400782T ES87400782T ES2018280B3 ES 2018280 B3 ES2018280 B3 ES 2018280B3 ES 87400782 T ES87400782 T ES 87400782T ES 87400782 T ES87400782 T ES 87400782T ES 2018280 B3 ES2018280 B3 ES 2018280B3
Authority
ES
Spain
Prior art keywords
procedure
coating
steam generator
peripheral pipe
peripheral
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
ES87400782T
Other languages
English (en)
Inventor
Jean-Pierre Cartry
Bruno Fraissenet
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.)
Areva NP SAS
Original Assignee
Framatome SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Framatome SA filed Critical Framatome SA
Application granted granted Critical
Publication of ES2018280B3 publication Critical patent/ES2018280B3/es
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F11/00—Arrangements for sealing leaky tubes and conduits
    • F28F11/02—Arrangements for sealing leaky tubes and conduits using obturating elements, e.g. washers, inserted and operated independently of each other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D39/00—Application of procedures in order to connect objects or parts, e.g. coating with sheet metal otherwise than by plating; Tube expanders
    • B21D39/06—Application of procedures in order to connect objects or parts, e.g. coating with sheet metal otherwise than by plating; Tube expanders of tubes in openings, e.g. rolling-in
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P19/00—Machines for simply fitting together or separating metal parts or objects, or metal and non-metal parts, whether or not involving some deformation; Tools or devices therefor so far as not provided for in other classes
    • B23P19/02—Machines for simply fitting together or separating metal parts or objects, or metal and non-metal parts, whether or not involving some deformation; Tools or devices therefor so far as not provided for in other classes for connecting objects by press fit or for detaching same
    • B23P19/022—Extracting or inserting relatively long parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B37/00—Component parts or details of steam boilers
    • F22B37/002—Component parts or details of steam boilers specially adapted for nuclear steam generators, e.g. maintenance, repairing or inspecting equipment not otherwise provided for
    • F22B37/003—Maintenance, repairing or inspecting equipment positioned in or via the headers
    • 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
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4935—Heat exchanger or boiler making
    • Y10T29/49352—Repairing, converting, servicing or salvaging
    • 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
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4935—Heat exchanger or boiler making
    • Y10T29/49387—Boiler making
    • 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
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49718—Repairing
    • Y10T29/49732—Repairing by attaching repair preform, e.g., remaking, restoring, or patching
    • 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
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49826—Assembling or joining
    • Y10T29/49908—Joining by deforming
    • Y10T29/49938—Radially expanding part in cavity, aperture, or hollow body
    • Y10T29/4994—Radially expanding internal tube
    • 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
    • Y10T29/00—Metal working
    • Y10T29/53—Means to assemble or disassemble
    • Y10T29/531—Nuclear device
    • 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
    • Y10T29/00—Metal working
    • Y10T29/53—Means to assemble or disassemble
    • Y10T29/53113—Heat exchanger
    • Y10T29/53122—Heat exchanger including deforming means

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)
ES87400782T 1986-04-30 1987-04-07 Procedimiento y dispositivo de encamisado de un tubo periferico de un generador de vapor. Expired - Lifetime ES2018280B3 (es)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR8606344A FR2598202B1 (fr) 1986-04-30 1986-04-30 Procede de chemisage d'un tube peripherique d'un generateur de vapeur.

Publications (1)

Publication Number Publication Date
ES2018280B3 true ES2018280B3 (es) 1991-04-01

Family

ID=9334831

Family Applications (1)

Application Number Title Priority Date Filing Date
ES87400782T Expired - Lifetime ES2018280B3 (es) 1986-04-30 1987-04-07 Procedimiento y dispositivo de encamisado de un tubo periferico de un generador de vapor.

Country Status (8)

Country Link
US (3) US4827594A (es)
EP (1) EP0245134B1 (es)
JP (1) JPS62263833A (es)
CA (1) CA1287483C (es)
DE (1) DE3765455D1 (es)
ES (1) ES2018280B3 (es)
FR (1) FR2598202B1 (es)
ZA (1) ZA872789B (es)

Families Citing this family (66)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8920382D0 (en) * 1989-09-08 1989-10-25 Nnc Ltd Heat exchangers
US5009002A (en) * 1990-01-11 1991-04-23 Haskel, Inc. Method for radially expanding and anchoring sleeves within tubes
US5062199A (en) * 1990-01-11 1991-11-05 Haskel, Inc. Apparatus for radially expanding and anchoring sleeves within tubes
US5201118A (en) * 1992-03-09 1993-04-13 Mcparland Kevin W Process for repairing heat-exchanger tubes
US5367768A (en) * 1992-12-17 1994-11-29 Mpr Associates, Inc. Methods of repairing inconel 600 nozzles of pressurized water reactor vessels
US5557840A (en) * 1995-02-13 1996-09-24 J. E. Miller Inc. Tube sheet locator and tube expander
US6634431B2 (en) * 1998-11-16 2003-10-21 Robert Lance Cook Isolation of subterranean zones
GB2384502B (en) 1998-11-16 2004-10-13 Shell Oil Co Coupling an expandable tubular member to a preexisting structure
US6557640B1 (en) 1998-12-07 2003-05-06 Shell Oil Company Lubrication and self-cleaning system for expansion mandrel
US6712154B2 (en) * 1998-11-16 2004-03-30 Enventure Global Technology Isolation of subterranean zones
US6745845B2 (en) * 1998-11-16 2004-06-08 Shell Oil Company Isolation of subterranean zones
US7603758B2 (en) 1998-12-07 2009-10-20 Shell Oil Company Method of coupling a tubular member
US6823937B1 (en) 1998-12-07 2004-11-30 Shell Oil Company Wellhead
US7231985B2 (en) 1998-11-16 2007-06-19 Shell Oil Company Radial expansion of tubular members
US7357188B1 (en) 1998-12-07 2008-04-15 Shell Oil Company Mono-diameter wellbore casing
US7121352B2 (en) 1998-11-16 2006-10-17 Enventure Global Technology Isolation of subterranean zones
US6575240B1 (en) 1998-12-07 2003-06-10 Shell Oil Company System and method for driving pipe
US6758278B2 (en) * 1998-12-07 2004-07-06 Shell Oil Company Forming a wellbore casing while simultaneously drilling a wellbore
US7363984B2 (en) 1998-12-07 2008-04-29 Enventure Global Technology, Llc System for radially expanding a tubular member
US7185710B2 (en) 1998-12-07 2007-03-06 Enventure Global Technology Mono-diameter wellbore casing
US7195064B2 (en) 1998-12-07 2007-03-27 Enventure Global Technology Mono-diameter wellbore casing
GB2344606B (en) * 1998-12-07 2003-08-13 Shell Int Research Forming a wellbore casing by expansion of a tubular member
GB2356651B (en) 1998-12-07 2004-02-25 Shell Int Research Lubrication and self-cleaning system for expansion mandrel
US7552776B2 (en) 1998-12-07 2009-06-30 Enventure Global Technology, Llc Anchor hangers
AU770359B2 (en) 1999-02-26 2004-02-19 Shell Internationale Research Maatschappij B.V. Liner hanger
US7055608B2 (en) 1999-03-11 2006-06-06 Shell Oil Company Forming a wellbore casing while simultaneously drilling a wellbore
CA2306656C (en) 1999-04-26 2006-06-06 Shell Internationale Research Maatschappij B.V. Expandable connector for borehole tubes
US7350563B2 (en) 1999-07-09 2008-04-01 Enventure Global Technology, L.L.C. System for lining a wellbore casing
AU783245B2 (en) 1999-11-01 2005-10-06 Shell Internationale Research Maatschappij B.V. Wellbore casing repair
US7234531B2 (en) 1999-12-03 2007-06-26 Enventure Global Technology, Llc Mono-diameter wellbore casing
US7100684B2 (en) 2000-07-28 2006-09-05 Enventure Global Technology Liner hanger with standoffs
AU9269501A (en) 2000-09-18 2002-03-26 Shell Oil Co Liner hanger with sliding sleeve valve
WO2002053867A2 (en) 2001-01-03 2002-07-11 Enventure Global Technology Mono-diameter wellbore casing
GB2389597B (en) 2000-10-02 2005-05-18 Shell Oil Co Plastically deforming and radially expanding a tubular member
US7100685B2 (en) 2000-10-02 2006-09-05 Enventure Global Technology Mono-diameter wellbore casing
US7410000B2 (en) 2001-01-17 2008-08-12 Enventure Global Technology, Llc. Mono-diameter wellbore casing
CA2453063C (en) 2001-07-06 2011-03-22 Enventure Global Technology Liner hanger
GB2395506B (en) 2001-07-06 2006-01-18 Eventure Global Technology Liner hanger
US7258168B2 (en) 2001-07-27 2007-08-21 Enventure Global Technology L.L.C. Liner hanger with slip joint sealing members and method of use
US7793721B2 (en) 2003-03-11 2010-09-14 Eventure Global Technology, Llc Apparatus for radially expanding and plastically deforming a tubular member
WO2003023178A2 (en) 2001-09-07 2003-03-20 Enventure Global Technology Adjustable expansion cone assembly
GB2422859B (en) 2001-11-12 2006-12-13 Enventure Global Technology Collapsible expansion cone
AU2002367348A1 (en) 2001-12-27 2003-07-24 Enventure Global Technology Seal receptacle using expandable liner hanger
WO2003089161A2 (en) 2002-04-15 2003-10-30 Enventure Global Technlogy Protective sleeve for threaded connections for expandable liner hanger
US7424918B2 (en) 2002-08-23 2008-09-16 Enventure Global Technology, L.L.C. Interposed joint sealing layer method of forming a wellbore casing
WO2004018824A2 (en) 2002-08-23 2004-03-04 Enventure Global Technology Magnetic impulse applied sleeve method of forming a wellbore casing
ATE417993T1 (de) 2002-02-15 2009-01-15 Enventure Global Technology Bohrlochfutterrohr mit einem einzigen durchmesser
EP1985797B1 (en) 2002-04-12 2011-10-26 Enventure Global Technology Protective sleeve for threated connections for expandable liner hanger
AU2003225001A1 (en) 2002-05-29 2003-12-19 Eventure Global Technology System for radially expanding a tubular member
GB2418944B (en) 2002-06-10 2006-08-30 Enventure Global Technology Mono Diameter Wellbore Casing
CA2499007C (en) 2002-09-20 2012-08-07 Enventure Global Technology Bottom plug for forming a mono diameter wellbore casing
AU2003263859A1 (en) 2002-09-20 2004-04-08 Enventure Global Technology Protective sleeve for expandable tubulars
WO2004027392A1 (en) 2002-09-20 2004-04-01 Enventure Global Technology Pipe formability evaluation for expandable tubulars
CA2499071C (en) 2002-09-20 2014-06-03 Enventure Global Technology Self-lubricating expansion mandrel for expandable tubular
WO2004076798A2 (en) 2003-02-26 2004-09-10 Enventure Global Technology Apparatus for radially expanding and plastically deforming a tubular member
US7886831B2 (en) 2003-01-22 2011-02-15 Enventure Global Technology, L.L.C. Apparatus for radially expanding and plastically deforming a tubular member
US7503393B2 (en) 2003-01-27 2009-03-17 Enventure Global Technology, Inc. Lubrication system for radially expanding tubular members
GB2415988B (en) 2003-04-17 2007-10-17 Enventure Global Technology Apparatus for radially expanding and plastically deforming a tubular member
US20050166387A1 (en) 2003-06-13 2005-08-04 Cook Robert L. Method and apparatus for forming a mono-diameter wellbore casing
US7712522B2 (en) 2003-09-05 2010-05-11 Enventure Global Technology, Llc Expansion cone and system
GB2432866A (en) 2004-08-13 2007-06-06 Enventure Global Technology Expandable tubular
US8231804B2 (en) * 2008-12-10 2012-07-31 Syntroleum Corporation Even carbon number paraffin composition and method of manufacturing same
US9035115B2 (en) * 2011-12-09 2015-05-19 Chevron U.S.A. Inc. Hydroconversion of renewable feedstocks
JP2014042920A (ja) * 2012-08-24 2014-03-13 Mitsubishi Heavy Ind Ltd 拡管治具、伝熱管の拡管方法、補修方法及び閉塞方法
CN104117816A (zh) * 2013-04-28 2014-10-29 宝山钢铁股份有限公司 一种组合式的钻杆加工方法
CN114393386B (zh) * 2022-01-25 2022-08-05 山东欣盛信息科技有限公司 一种地热能发电机组的装配设备

Family Cites Families (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962767A (en) * 1974-08-13 1976-06-15 Westinghouse Electric Corporation Method for repairing a heat exchanger tube
US4069573A (en) * 1976-03-26 1978-01-24 Combustion Engineering, Inc. Method of securing a sleeve within a tube
US4262402A (en) * 1978-10-18 1981-04-21 Westinghouse Electric Corp. Method for servicing a steam generator
US4329769A (en) * 1979-12-05 1982-05-18 Westinghouse Electric Corp. Apparatus for working on tubesheets
US4573248A (en) * 1981-06-04 1986-03-04 Hackett Steven B Method and means for in situ repair of heat exchanger tubes in nuclear installations or the like
DE3122660C2 (de) * 1981-06-06 1986-06-19 Brown Boveri Reaktor GmbH, 6800 Mannheim Einrichtung zur Inspektion und/oder zur Reparatur der Rohre eines Dampferzeugers einer Kernkraftanlage
US4641409A (en) * 1982-09-23 1987-02-10 Westinghouse Electric Corp. Reconstituting a nuclear reactor fuel assembly
US4485847A (en) * 1983-03-21 1984-12-04 Combustion Engineering, Inc. Compression sleeve tube repair
GB8317997D0 (en) * 1983-07-01 1983-08-03 Nat Nuclear Corp Ltd Heat exchange tube repairs
US4571821A (en) * 1983-08-26 1986-02-25 Westinghouse Electric Corp. Sleeve insertion
US4586250A (en) * 1983-10-03 1986-05-06 Westinghouse Electric Corp. Apparatus for sleeving tubes in hostile environments
US4688327A (en) * 1983-10-03 1987-08-25 Westinghouse Electric Corp. Sleeving of tubes of steam generator
US4639994A (en) * 1983-10-03 1987-02-03 Westinghouse Electric Corp. Suspension of tools for sleeving of tubes of steam generator
EP0137984A3 (en) * 1983-10-14 1986-02-05 Lummus Crest S.A.R.L. Tube repair insert for steam generator
US4653164A (en) * 1984-02-14 1987-03-31 Westinghouse Electric Corp. Sleeving of tubes of steam generator in hostile environment
US4580426A (en) * 1984-02-27 1986-04-08 Westinghouse Electric Corp. Hybrid expansion apparatus and process
US4547944A (en) * 1984-03-02 1985-10-22 National Nuclear Corporation Limited Tube-in-shell heat exchangers
BE899632A (nl) * 1984-05-11 1984-11-12 Ebes Ver Energie Schelde Werkwijze om pijpen van een stoomgenerator te herstellen.
US4713870A (en) * 1985-03-26 1987-12-22 Raychem Corporation Pipe repair sleeve apparatus and method of repairing a damaged pipe
FR2598209B1 (fr) * 1986-04-30 1988-08-12 Framatome Sa Procede et dispositif de chemisage a distance d'un tube de generateur de vapeur d'un reacteur nucleaire a eau sous pression.
FR2598211B1 (fr) * 1986-04-30 1988-08-12 Framatome Sa Dispositif d'alimentation a distance en pieces de forme cylindrique d'une machine automatique telle qu'une machine de bouchage de tubes d'un generateur de vapeur d'un reacteur nucleaire a eau sous pression
US4716753A (en) * 1986-07-10 1988-01-05 Dresser Industries, Inc. Flexible tube expander extension assembly
US4829648A (en) * 1987-01-27 1989-05-16 Westinghouse Electric Corp. Apparatus and method for simultaneously loading a reinforcing sleeve and mandrel into a tube

Also Published As

Publication number Publication date
US4827594A (en) 1989-05-09
US4922605A (en) 1990-05-08
DE3765455D1 (de) 1990-11-15
ZA872789B (en) 1988-03-30
CA1287483C (en) 1991-08-13
EP0245134A1 (fr) 1987-11-11
US4976027A (en) 1990-12-11
JPS62263833A (ja) 1987-11-16
FR2598202B1 (fr) 1990-02-09
FR2598202A1 (fr) 1987-11-06
EP0245134B1 (fr) 1990-10-10

Similar Documents

Publication Publication Date Title
ES248035Y (es) Un dispositivo distribuidor de vapor
BR8701158A (pt) Dispositivo medidor de vazamento de vapor
AR231555A1 (es) Dispositivo de planchado a vapor
ES517210A0 (es) Perfeccionamientos en un generador de vapor.
FR2598202B1 (fr) Procede de chemisage d'un tube peripherique d'un generateur de vapeur.
ES2002258B3 (es) Procedimiento de colocacion de tubos en un generador de vapor.
ES521751A0 (es) Dispositivo de control de flujo para un generador de vapor.
ES525240A0 (es) Distribucion de circulacion de entrada de un generador de vapor.
BR8701793A (pt) Dispositivo julgador de operacao de purgador de vapor
BR8805886A (pt) Gerador de vapor
ES549899A0 (es) Procedimiento de control optico de forma y de dimensiones del extremo de los tubos de un generador de vapor
ES513289A0 (es) "generador de vapor".
BR8603361A (pt) Gerador de vapor
MX9200347A (es) Sistema generador de vapor.
ES541149A0 (es) Un dispositivo para extraer tapones de tubos taponados de generador de vapor
ES538746A0 (es) Generador de vapor
ES2021132B3 (es) Condensador de vapor
ES542883A0 (es) Generador de vapor
BR8108514A (pt) Lampada a vapor de metal de alta pressao
BR8207693A (pt) Processo e dispositivo de alimentacao de um gerador de vapor
ES510610A0 (es) "una instalacion generadora de vapor con dispositivo de purificacion de los gases de escape".
ES510587A0 (es) Perfeccionamientos en un generador de vapor sobrecalentado
ES257485Y (es) Dispositivo de guia de tubo y de arrastre de guia para generador de vapor .
ES501221A0 (es) Aparato generador de vapor que incluye un canon generador devapor
BR8806107A (pt) Dispositivo gerador de vapor sem pressao