SIST EN 12284:2004
(Main)Refrigerating systems and heat pumps - Valves - Requirements, testing and marking
Refrigerating systems and heat pumps - Valves - Requirements, testing and marking
This European Standard specifies safety requirements, safety factors, test methods, test pressures used and marking of refrigerating valves and other components with similar bodies, hereinafter called valves, for use in refrigerating systems.
It describes the procedure to be followed when designing (by calculation or by an experimental design method) valve parts subjected to pressure as well as the criteria to be used in the selection of materials.
The standard describes methods by which reduced impact values at low temperatures may be taken into account in a safe manner.
This standard applies to the design of bodies and bonnets for pressure relief devices, including bursting disc devices, with respect to pressure containment but it does not apply to any other aspects of the design or application of pressure relief devices.
Kälteanlagen und Wärmepumpen - Ventile - Anforderungen, Prüfung und Kennzeichnung
Diese Norm legt sicherheitstechnische Anforderungen, Sicherheitsbeiwerte, Prüfverfahren, anzuwendende Prüfdrücke und die Kennzeichnung von Kältemittelventilen und andere Bauteilen mit vergleichbaren Gehäusen, im Folgenden kurz Ventil genannt, für die Verwendung in Kälteanlagen fest.
Sie beschreibt das Verfahren, das bei der Konstruktion (durch Berechnung oder anhand von Prüfungen) von druckbeanspruchten Ventilen zugrunde zu legen ist sowie die bei der Auswahl von Werkstoffen für Ventilteile zu berücksichtigenden Kriterien.
Die Norm beschreibt Methoden, nach denen reduzierte Werte für die Kerbschlagarbeit bei niedriger Temperatur auf sichere Art und Weise berücksichtigt werden können.
Diese Norm gilt für die Konstruktion von Gehäusen und Oberteilen für Druckentlastungseinrichtungen, einschließlich Berstscheibeneinrichtungen, im Hinblick auf die Druckfestigkeit, sie gilt jedoch nicht für andere Aspekte der Konstruktion oder die Anwendung von Druckentlastungseinrichtungen.
Systemes de réfrigération et pompes a chaleur - Robinetterie - Exigences, essais et marquage
La présente Norme européenne spécifie les exigences de sécurité, les coefficients de sécurité, les méthodes d'essai, les pressions d'essai utilisées ainsi que le marquage des robinets frigorifiques et des autres composants possédant un corps similaire, ci-apres désignés par « robinets », destinés a etre utilisés dans les systemes de réfrigération.
La présente Norme décrit la procédure a suivre lors de la conception (par calcul ou par une méthode expérimentale de conception) des éléments de robinetterie soumis a une pression, ainsi que les criteres a appliquer lors de la sélection des matériaux.
Elle décrit également les méthodes permettant de prendre en compte en toute sécurité des valeurs de résilience faibles a basse température.
La présente Norme s'applique a la conception des corps et des chapeaux des dispositifs limiteurs de pression, y compris les dispositifs a disque de rupture, eu égard au confinement de la pression, mais ne s'applique pas aux autres aspects de la conception ou de l'application des dispositifs limiteurs de pression.
Hladilni sistemi in toplotne črpalke - Ventili - Zahteve, preskušanje in označevanje
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Refrigerating systems and heat pumps - Valves - Requirements, testing and markingSystemes de réfrigération et pompes a chaleur - Robinetterie - Exigences, essais et marquageKälteanlagen und Wärmepumpen - Ventile - Anforderungen, Prüfung und KennzeichnungTa slovenski standard je istoveten z:EN 12284:2003SIST EN 12284:2004en27.20027.08023.060.20ICS:SLOVENSKI
STANDARDSIST EN 12284:200401-september-2004
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12284September 2003ICS 23.060.20English versionRefrigerating systems and heat pumps - Valves - Requirements,testing and markingSystèmes de réfrigération et pompes à chaleur -Robinetterie - Exigences, essais et marquageKälteanlagen und Wärmepumpen - Ventile -Anforderungen, Prüfung und KennzeichnungThis European Standard was approved by CEN on 21 April 2003.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and UnitedKingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2003 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12284:2003 E
EN 12284:2003 (E)2ContentsPageForeword.31Scope.32Normative references.33Terms and definitions.44List of Symbols.65General Requirements.76Materials.87Design.108Construction and workmanship.119Testing.1410Marking and additional information.1711Documentation.18Annex A (normative)
Procedure for the design of a valve by use of a simplified method of calculation.20Annex B (normative)
Experimental design method for valves.23Annex C (normative)
Determination of the allowable pressure at the maximum operating temperature.28Annex D (normative)
Determination of the allowable pressure at minimum operating temperature(Requirements to avoid brittle fracture).29Annex E (informative) Compilation of material characteristics of often used materials.34Annex F (informative)
Justification of the individual methods.54Annex ZA (informative)
Relationship between this European Standard and the EssentialRequirements of EU Directive 97/23/EC.60Bibliography.61
EN 12284:2003 (E)3ForewordThis document (EN 12284:2003) has been prepared by Technical Committee CEN /TC 182, "Refrigeratingsystems, safety and environmental requirements", the secretariat of which is held by DIN.This European Standard shall be given the status of a national standard, either by publication of an identical text orby endorsement, at the latest by March 2004, and conflicting national standards shall be withdrawn at the latest byMarch 2004.This document has been prepared under a mandate given to CEN by the European Commission and the EuropeanFree Trade Association, and supports essential requirements of EU Directive(s).For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document.Annexes A, B, C, D are normative and annexes E and F are informativeAccording to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,Slovakia, Spain, Sweden, Switzerland and the United Kingdom.1 ScopeThis European standard specifies safety requirements, safety factors, test methods, test pressures used andmarking of refrigerating valves and other components with similar bodies, hereinafter called valves, for use inrefrigerating systems.It describes the procedure to be followed when designing (by calculation or by an experimental design method)valve parts subjected to pressure as well as the criteria to be used in the selection of materials.The standard describes methods by which reduced impact values at low temperatures may be taken into accountin a safe manner.This standard applies to the design of bodies and bonnets for pressure relief devices, including bursting discdevices, with respect to pressure containment but it does not apply to any other aspects of the design or applicationof pressure relief devices.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this EuropeanStandard only when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred to applies.EN 378-1, Refrigerating systems and heat pumps — Safety and environmental requirements — Part 1: Basicrequirements, definitions, classification and selection criteria.EN 378-2:2000, Refrigerating systems and heat pumps — Safety and environmental requirements — Part 2:Design, construction, testing, marking and documentation.EN 378-4, Refrigerating systems and heat pumps — Safety and environmental requirements — Part 4: Operation,maintenance, repair and recovery.EN 764-4, Pressure equipment — Part 4: Establishment of technical delivery conditions for metallic materials.EN 764-5, Pressure equipment — Part 5: Compliance and Inspection Documentation of Materials.EN 1563, Founding — Spheroidal graphite cast irons.
EN 12284:2003 (E)4EN 10045-1, Metallic materials — Charpy impact test — Part 1: Test method.EN 10087, Free-cutting steels — Technical delivery conditions for semi-finished products, hot-rolled bars and rods.EN 10204, Metallic products — Types of inspection documents.prEN 12516-2, Industrial valves — Shell design strength — Part 2: Calculation methods for steel valve shells.EN 13445-2:2002, Unfired pressure vessels — Part 2: Materials.prEN 14276-1:2001, Pressure equipment for refrigerating systems and heat pumps — Part 1: Vessels — Generalrequirements.EN 60534-2-1:1998, Industrial-process control valves — Part 2-1: Flow capacity — Sizing equations for fluid flowunder installed conditions (IEC 60534-2-1:1998).EN ISO 6708:1995, Pipework components — Definition and selection of DN (nominal size (ISO 6708:1995).ISO 7268:1983, Pipe components — Definition of nominal pressure.CR-ISO 15608:2000, Welding — Guidelines for a metallic material grouping system (ISO/TR 15608:2000).3 Terms and definitionsFor the purposes of this European Standard, the following terms and definitions apply.3.1Valvedevice with shut-off, non-return, regulating- or control functions for refrigerant flow or a filter device in similardimensions. It can be operated by hand, by an actuator or by the system pressure of the plantNOTEThe expression ‘control valve' denotes an automatic valve with a feedback system and the expression ‘regulating valve’denotes a hand-operated valve which may have a shaped cone to assist the regulating function.3.2Operating rangethe combination of temperature and pressure conditions at which the valve can safely be operated3.3Nominal size (DN)an alpha-numeric designation of size for components of a pipework system [See EN ISO 6708:1995]3.4Nominal pressure (PN)a value of a pressure in the range of the maximum allowable pressure for planning a plant or a component (seeISO 7268:1983)3.5Corrosionall forms of material wastage (e. g. oxidation, erosion, wear and abrasion)3.6Maximum design temperaturehighest temperature that can occur during operation or standstill of the refrigerating system or during testing undertest conditions3.7Minimum design temperaturelowest temperature that can occur during operation or standstill of the refrigerating system or during testing undertest conditions
EN 12284:2003 (E)53.8min t0 100the lowest temperature at which the valve can be used at a load of up to 100 % of the allowable design stress at20 °C, taking the safety factors according to Table A.2 into account3.9min t0 75the lowest temperature at which the valve can be used, if is load amounts to 75 % maximum of the allowabledesign stress at 20 °C, taking the safety factors according to Table A.2 into account3.10min t0 25the lowest temperature at which pressure parts can be used, if their load amounts to 25 % maximum of theallowable design stress at 20 °C, taking the safety factors according to Table A.2 into account
EN 12284:2003 (E)64 List of SymbolsSymbols used in this Standard are given in Table 1:Table 1 – List of symbolsALElongation after fracture where the measured length is equal or greater than 0,4times of
diameter of the rodmmA5Elongation after fracture where the measured length is equal 5 times ofdiameter of the rod%aLifetime in years; for valves 20 yearsannoCQFactor to compensate for the quality of a casting—deNegative wall thickness tolerancemmeactActual wall thickness at given measuring points of the valve to be testedmmecReduction in wall thickness caused by occurance of corrosionmmeconComponent wall thickness as specified in the design drawingmmKVImpact rupture energyJKV0Threshold value of impact rupture energy, where the impact rupture energy isdefined as independent of the temperatureJKV0tStandard value of impact rupture energy at standard temperature of the materialJKVTS minImpact rupture energy at minimum operating temperature TS minJKVSis the rate of flow of water in cubic metres per hour for a differential pressure Dp of1 bar (0,1 MPa) at the rated full opening m3/hLthe leakage in percent of KVS%N6is 31,6 according to Table 1 of EN 60534-2-1—PDDesign pressureMPaPFMaximum allowable design test pressureMPaPSMaximum allowable pressure in common sense, without regarding any influenceof temperatureMPaPS0Maximum allowable pressure at ambient temperature (- 10 °C to + 50 °C)according to strength design (without temperature correction)MPaPSTS maxMaximum allowable pressure at maximum operating temperatureMPaPSTS minMaximum allowable pressure at minimum operating temperatureMPaPTestMinimum burst test pressure (greater than PF)MPap1Upstream pressureMPaDpDifferential pressureMPap'Testing pressure of each valve after productionMPaQMMass flow ratekg/hQVupstream flow ratem3/hRe 1,0Yield strength, 1,0% offsetMPa, N/mm2Re 1,0 TS maxYield strength, 1,0% offset at highest operating temperatureMPa, N/mm2Re 0,2Yield strength, 0,2% offset at ambient temperatureMPa, N/mm2Rp 0,2Proof strength, 0,2% offset at ambient temperatureMPa, N/mm2Rp 0,2 TS minProof strength, 0,2% offset at minimum operating temperatureMPa, N/mm2Rp 0,2/tProof strength, 0,2% offset at temperature tMPa, N/mm2Rp 0,2 TS maxProof strength, 0,2% offset at highest operating temperatureMPa, N/mm2Rp 1,0Proof strength, 1,0% offset at ambient temperatureMPa, N/mm2ReHUpper yield strengthMPa, N/mm2ReH TS maxUpper yield strength at
highest operating temperatureMPa, N/mm2RmTensile strengthMPa, N/mm2
EN 12284:2003 (E)7Table 1 (continued)Rm TS maxTensile strength at
highest operating temperatureMPa, N/mm2Rm actActual tensile strength of the material of the valve to be testedMPa, N/mm2Rm conTensile strength used for the designMPa, N/mm2rDensity of the actual fluidkg/m3r0Density of water at 15,5 °Ckg/m3r1Upstream densitykg/m3SCFactor to compensate effects of corrosion—SconFactor for the calculation of the burst test pressure taking into account the tensilestrength according to Table A.2 (see footnoted of Table A.2)SFFactor to allow for forming—STS minFactor taking into consideration the impact strength reduction due to minimumoperating temperature—STS maxFactor to allow for the reduction in strength due to the highest operatingtemperature—SsFactor to allow for the test pressure—s conInitial design stressMPa, N/mm2s corrAllowable stress values derived from s conMPa, N/mm2TSOperating temperature°CTSminLowest operating temperature°CTSmaxHighest operating temperature°CVInner volume of a valvelXCorrection of the actual wall thickness relative to the wall thickness of the design—kassignes the value 1PpD—YCorrection on the basis of current strength values of the test sample relative tothe strength parameters for the design of valves—ZFactor to allow for the quality of a joint (e.g. welded joint)—¶Wall thickness reduction per yearmmNOTE
1 MPa = 10 bar5 General Requirements5.1 Installation and operationValves shall be designed to be installed and operated in accordance with the requirements of EN 378 Parts 1, 2and 4.5.2 Components under pressureAll parts of the valve shall be designed and manufactured to remain leak proof and to withstand the pressureswhich may occur during operation, standstill and transportation, taking into account the thermal, physical andchemical stresses to be expected.5.3 Excessive mechanical stressAfter installation, valves, especially valves for hot gas defrosting, shall not be under excessive mechanical stressfrom fitting of the pipe or from temperature variations during operation.NOTEHot gas defrosting can produce hydraulic shocks resulting in transient pressures in excess of PS. Furtherinformation see subclause 6.3.2 in EN 378-2:2000.
EN 12284:2003 (E)85.4 LeakageThe valve shall not leak to the outside when tested as described in 9.4. Valve seats shall seal to a degree specifiedin 9.6.5.5 Functioning of hand-operated valvesProper functioning of hand-operated valves shall be ensured for the entire operating range up to the allowablepressure PS and the associated allowable temperature TS.5.6 Functioning of actuator-operated valvesProper functioning of actuator-operated valves operated by the fluid or by energy from an external source, shall beensured for the entire operating range, which is to be specified by the manufacturer.6 Materials6.1 General6.1.1 Using metalic materialsMetalic materials, included welding filler metals, solders, brazing metals and sealants, shall allow for the thermal,chemical and mechanical stresses arising in system operation. Materials shall be resistant to the refrigerants,solvents (in absorption systems) and refrigerant-oil mixtures used in each particular case.NOTEExtensive lists of suitable materials for steel can be found in EN 13445-2, where also other useful information isfound, or for other materials in Annex E of this standard.6.1.2 Using non-metallic materialsIt is permitted to use non-metallic materials, e.g. for gaskets, coatings, insulating materials, and sightglasses,provided that they are compatible with other materials, refrigerants and lubricants.6.2 Requirements for materials to be used for pressurized parts6.2.1Materials listed in this standard (see Annex E) have been identified for use in refrigerating valves6.2.2Lamellar cast iron shall not be used but nodular cast iron according EN 1563 can be used down totemperatures at which it can be proved to achieve overall levels of safety equivalent to alternative materials.6.2.3Where new materials are proposed, the design shall be carried out using Annexes A to D provided the yieldstrength or proof strength, as applicable, at the maximum operating temperature and the impact strength at thelowest operating temperature are known. If these properties are not known the material shall not be used.6.3 Compatibility of connectionsMaterials which are to be physically linked shall be suitable for an effective connection, depending on the particularmaterials used and on the dimensions of the piping specified.6.4 Requirements to avoid brittle fractureFor valves with reduced ductility at low temperatures the allowed stress shall be reduced according to Annex D.6.5 Requirements for documentationThe quality of materials is to be confirmed according to EN 10204.
EN 12284:2003 (E)96.6 DuctilityMaterials which are to be considerably deformed shall be sufficiently ductile and capable of being heat treatedwhere necessary.6.7 AgeingMaterials for pressurized parts shall not be significantly affected by ageing.6.8 CastingsCastings shall exhibit a low stress level. If they are not subjected to stress relief heat treatment, controlled coolingshall be ensured after the casting process and after any heat treatment which may have been applied.6.9 Forged and welded componentsForged and welded components shall be fabricated from suitable materials (e.g. weldable close grain low carbonsteel) and shall be heat treated where the combination of operating temperature, operating pressure and wallthickness indicates by calculation that heat treatment is necessary.6.10 Nuts, bolts and screwsMaterials for nuts, bolts and screws for jointing housing parts subject to pressure loads shall exhibit the correctcharacteristics for the material over the full range of the application limits for the nuts, bolts and screws defined bythe operating temperature, whereby the following minimum values for the elongation at fracture and notched impactstrength shall be achieved. The test piece for impact strength measurements shall be taken parallel to the drawingor rolling direction, and the notch orientation shall be perpendicular to the drawing or rolling direction.a) for ferritic materials an elongation at fracture A5 ³ 14 %;b) for cold-formed austenitic materials an elongation at fracture AL ³ 0,4 ´ d ;c) a notched impact strength KV at 20 °C for tempered alloyed steels of at least 52 J and of at least 40 J fortempered carbon steels (ISO V test-piece).The following values shall be achieved at the lowest operating temperature:a notched impact strength KV for tempered alloyed steels and tempered carbon steels of at least 27 J (ISO V test-piece).NOTESome suitable materials are given in Annex E of this standard.6.11 SpindlesMaterial for spindles shall be corrosion-resistant to ensure safe operation, and shall exhibit appropriate materialcharacteristics over the complete operating temperature range.NOTE Some suitable materials are given in Annex E.6.12 Seat, valve plate and seal materialsWhere soft materials are used for seats, valve plates and seals the material shall be fixed and restrained. Suitablematerials are, for exampIe, soft metals or polymers.
EN 12284:2003 (E)107 Design7.1 GeneralThe design requirements herein cover parts subject to pressure constructed of materials defined in clause 6. Thedimensions of pressurized parts shall be such that the stress of the parts in the entire operating range shall be keptwithin safe limits. Valve strength design shall be based on European Standards (for exampleprEN 12516-2:2000).The valve design shall be so that any liquid trapped internally shall be safely relieved or contained.7.2 Maximum allowable pressureThe maximum allowable pressure PS of the refrigerant containing parts shall not be less than the value derivedfrom the temperatures specified in 5.1.2 in EN 378-2:2000.The maximum allowable pressure PS shall not be exceeded except during the short period of time necessary forthe pressure relief device to operate with a maximum value of 1,1 times PS.7.3 Design pressureThe design pressure PD shall not be less than PS which is derived from the temperatures specified in 5.1.2 inEN 378-2:2000.7.4 Bodies and bonnetsBodies and bonnets subjected to pressure shall be designed by strength calculation according to prEN 12516-2:2000 or by an experimental design method including a test with the maximum allowable design test pressure PFand the minimum burst test pressure PTest according to Annex A to D on a representative prototype.Spindles, discs and gland seals are not subject to these calculations or tests.7.4.1Safety factors shall be used in the design of valve bodies, bonnets, flanges, nuts, bolts and screws.Appropriate factors and methods of using them in design of valve bodies and bonnets are specified in normativeAnnexes A to D.7.4.2Cast or welded valves shall be designed to take account of possible imperfections in the casting or in thewelded zone. These matters are covered in Annex A to C.7.4.3The material properties used to calculate the strength of bodies and bonnets subjected to pressure and ofnuts, bolts and screws used as fasteners shall relate to a temperature of 20 °C.7.4.4Screwed bonnets shall be so constructed that it is impossible to screw the bonnet out of the valve bodywithout removing a locking device.7.5 Final assessmentThe strength of the valve shall be verified by test with the maximum allowable design test pressures PF and theminimum burst test pressure PTest, see Annex A to D.7.6 Pressure-sensitive componentsThe functioning of pressure-sensitive components which form part of metering, control and shut-off valves andwhich are subject to pressure from the refrigerant circuit shall not be impaired at pressures up to the allowablepressure.When verifying the strength of pressure-sensitive components in a bursting test, a test pressure equal to 2.5 timesthe allowable pressure shall be applied.
EN 12284:2003 (E)11Proof of adequate strength shall be deemed to have been provided if the pressure-sensitive component does notburst.NOTEThe bursting test pressure for pressure-sensitive components is less than the pressure used for testing the mainassembly.8 Construction and workmanship8.1 GeneralThe construction of a valve shall be suitable for using a valve at pressure and temperature of the refrigerant towhich the valve is exposed.Valves with flanges can only be used in connection with fitting companion flanges.8.2 Body and bonnet8.2.1Particular attention shall be paid to smooth transitions of cross-sections in body design, as sharp edges areliable to reduce the deformability and may thus result in fracture.8.2.2Seals between body and bonnet shall be continuously located so that they are confined. Metal to metalseals are permissible provided sufficient force can be applied to seal by deformation.8.2.3The contact faces on body and bonnet, on the gland and on the valve head and on the seat faces shall besufficiently smooth to ensure sealing.8.3 Valve seatsHand-operated valves with seat diameters above 25 mm shall be designed so as to prevent sliding frictionoccurring between the valve plate and the seat in the body, e.g. by providing a spindle capable of rotating against anon-rotating valve Plate.8.4 Spindle seals and back seating for valves8.4.1Spindle seals, such as O-rings, bellows or gland packing, shall, at the operating temperature of the valve,be resistant to oil and refrigerants and remain tight when subjected to positive or negative pressures. In order toprevent breaking caused by freezing water, no moisture shall be allowed to penetrate into bellows seals.8.4.2Back sealing (sealing of the spindle by the valve retainer, when the valves is totally open) and spindle sealsshall be so designed that the seal (e.g. gland or O-ring) can be replaced or re-tightened from the outside withoutany risk under operating conditions. The back seat shall be sufficiently tight when the valve is in the fully openposition. Replacing and re-tightening from the outside does not apply to spindles which are seldom operated, e.g.for forced opening of solenoid valves, if they are covered by a sealing cap.8.4.3When the spindle is sealed by a bellows seal or a diaphragm, a back seat or a gland has to ensure, thatthe spindle remains sealed if the bellows or the diaphragm fractures. In addition a screwed sealing cap may beprovided.8.4.4Shut-off valves without back seating e.g. gate-, butterfly-, ball-valves have to be installed in accordance to7.1.6 in EN 378-2:2000, which states that it must be possible to isolate the shut-off valve from the system withoutinterrupting the system (see 8.4.2).8.4.5Hand-operated shut-off valves intended for use during infrequent maintenance operations shall be fittedwith a sealing cap in addition to the normal sealing of the valve unless the valve may be required during anemergency.
EN 12284:2003 (E)128.5 Screwed spindles8.5.1The valve spindle screw shall be sealed within the valve by the gland, unless the sealing is provided bybellows or diaphragms (see 8.4 3).8.5.2The valve spindle shall be designed to avoid additional stresses within the valve so there is no risk whenthe spindle fails under excessive torque.8.5.3Valve spindles shall be designed to avoid scuffing between the spindle, the bonnet and the thread piece, ifany. This can be achieved by selecting materials which are compatible in respect of low frictional forces.8.5.4Valve spindles shall be manufactured from such materials, which are resistant against corrosion caused byrefrigerant and its oil as well as the surrounding conditions (see Annex E).8.6 Design of glandsIt shall be impossible for any part of the gland assembly or the gland assembly as a whole to be unscrewed andthus ejected by internal pressure. One method of achieving this is by using screw threads of a different pitchwhereby the screw thread of the gland nut is of the minor pitch.Means to remove gland assemblies easily shall be provided. Possible methods of achieving this are by providingtapped holes or a collar.NOTESpecial design features may be required in the case of temperatures below about – 40°C in order to ensure properfunctioning over the whole range of allowable temperatures. One method of achieving this is by providing a heated or thermallyinsulated extension of the bonnet.8.7 Locking of spindles and shaftsSpindles and shafts of shut-off valves shall be secured against unintentional unscrewing.8.8 CapsThe body or bonnet may be provided with a seal cap where the spindle passes through the gland. Caps of shut-offvalves which are not, in normal circumstances, to be used shall be capable of being provided with a seal wire and aseal to prevent operation by unauthorized persons. Screwed caps which are intended to act as a seal shall remaintight up to the allowable pressure PS and shall be so designed that the internal pressure decreases on openingbefore the screw thread ceases to be capable of sustaining the load. Methods of achieving this include a relief borein either the cap or the valve body.Screw threads on valve caps shall be right-handed.8.9 Hand-operated valves8.9.1Attention shall be paid to the need to equalize differential pressure if the valve nominal size and thepressure difference are sufficiently high to require it. Equalization may be by external or internal bypass, seeTable 2.NOTEFor permissible manual forces see EN 12570: Industrial valves — Method for sizing the operating element.
EN 12284:2003 (E)13Table 2— Hand operated valves: Suggested maximum differential pressure for closing by handPSDNMPa1001251502002503003504001,0————0,90,60,450,351,6———1,40,90,60,450,352,5——2,11,40,90,60,450,354,0—3,32,11,40,90,60,450,356,34,43,32,11,40,9———NOTE 1Where there is pressure downstream over a valve, valves with PS / DN combinations above and to the left ofthe stepped line and pressure under the valve retainer can be closed manually when the differential pressure does notexceed the allowable pressure marked above.NOTE 2PS / DN combinations below and to the
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