Bailey Technical Catalogue - Safety Systems UK Ltd

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Safety Relief ValvesINTRODUCTIONThe effects of exceeding safe pressure levels in anunprotected pressure vessel or system, can havecatastrophic effects on both plant and personnel.Safety relief valves should be used to protect anypressurised system from the effects of exceeding itsdesign pressure limit.A safety relief valve is designed to automaticallydischarge gas, vapour or liquid from any pressurecontaining system, preventing a predetermined safepressure being exceeded, and protecting plant andpersonnel.Safety ValveA valve which automatically discharges gases andvapours so as to prevent a predetermined safepressure being exceeded. It is characterised by arapid full opening action and is used for steam, gasesor vapour service.Relief ValveA valve which automatically discharges fluid, usuallyliquid, when a predetermined upstream pressure isexceeded. The term is commonly used for pressurerelieving valves in which the lift is proportional tothe increase in pressure above the set pressure.Safety Relief ValveA valve which will automatically discharge gases,vapours or liquids, to prevent a predetermined safepressure being exceeded. It is characterised by arapid opening action.5
DEFINITIONSSet PressureThe pressure measured at the valve inlet at which asafety relief valve should commence to lift underservice conditions.OverpressureThe pressure increase above set pressure at thevalve inlet at which the discharge capacity is attained.Usually expressed as a percentage of set pressure.AccumulationThe pressure increase over a maximum safe workingpressure of the vessel or system when the safetyrelief valve is discharging at its rated capacity iscalled accumulation. The term refers to the vesselor system to be protected and not to the valve.Accumulation is the same as over-pressure when thevalve is set at the design pressure of the vessel.Re-Seat PressureThe pressure measured at the valve inlet at whichthe safety relief valve closes.Blow-DownThe difference between the set pressure and there-seating pressure expressed as a percentage of theset pressure or as a pressure difference.SimmerThe pressure zone between the valve set pressureand the popping pressure. In this pressure zone thevalve is only slightly open and therefore discharging asmall percentage of its rated capacity.Differential Set PressureThis is the difference between the set pressure andthe constant superimposed back pressure. It isapplicable only when a conventional type safety reliefvalve is used to discharge against constantsuperimposed back pressure. (It is the pressure atwhich the safety valve is set at on the test benchwithout back pressure.)Cold Differential Set PressureThe pressure at which a safety relief valve, intendedfor high temperature service, is set on a test rig usinga test fluid at ambient temperature. The colddifferential test pressure will be higher than the setpressure, in order to compensate for the effect ofelevated temperature on the valve. Refer to table onpage 8.Valve LiftThe actual travel of the valve disc away from the seatwhen the valve is relieving.Discharge CapacityActual rate of discharge of service media, which can beexpressed in mass flow or volumetric terms.Equivalent CapacityCalculated mass or volumetric flow rate of the valve ofa given test fluid. The fluids commonly used for testpurposes are steam, air and water.PRESSURE TERM RELATIONSHIPPopping PressureThe pressure at which the valve disc rapidly movesfrom a slightly open (simmer) position to apractically full open position.Superimposed Back PressurePressure higher than atmosphere in the safety reliefvalve outlet. This may result from discharge into thecommon disposal system of other safety relief valvesor devices, or as a result of a specific designrequirement. Back pressure can be either constantor variable depending on the operating conditions.Pressure VesselRequirementMaximumPermittedAccumulationDesignPressureAccumulation% of VesselDesign Pressure11010090Safety ValveCharacteristicOver-pressure(Typical)Blowdown(Typical)MaximumRelievingPressureSetPressureRe-seatPressureBuilt Up Back PressureThe pressure existing at the outlet of a safety reliefvalve caused by flow through the valve into thedisposal system.Note: System operating pressure must always be less than there-seat pressure.6
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Page 9 and 10: INSTALLATIONSafety Relief Valves sh
Page 17 and 18: SIZINGTemperature Rating in kWSize
Page 19 and 20: PARTSITEM PART MATERIALSCarbon Stee
Page 21 and 22: PARTSITEM PART MATERIALCarbon Steel
Page 23 and 24: PARTSITEM PART MATERIALThere are tw
Page 25 and 26: PARTS1418121611101978613317152ITEM
Page 27 and 28: PARTSITEM PARTMATERIAL480 490119105
Page 29 and 30: PARTSITEM PART MATERIAL211692028173
Page 31 and 32: G4 SeriesPILOT OPERATED PRESSURE RE
Page 33 and 34: LOW PRESSURE TOPGAS AND OXYGEN DUTI
Page 35 and 36: MATERIALSITEM 2042 & 2043 2044 2045
Page 37 and 38: DIMENSIONSCONNECTION OPTIONSBCScrew
Page 39 and 40: INSTALLATIONTYPICAL STEAM REDUCING
Page 41 and 42: SIZINGThe G4 Pressure Regulator can
Page 43 and 44: SURPLUS/MAINTAINING VALVESThe ‘G4
Page 45 and 46: TECHNICAL SPECIFICATION - G4 SURPLU
Page 47 and 48: PARTSITEM PARTMATERIALA191220111098
Page 49 and 50: Vent holeCXAAIN OUTBDDIMENSIONSScre
Page 51 and 52: PARTSITEM PARTMATERIAL1 Adjusting S
Page 53 and 54: PARTSITEM PARTMATERIAL121* Piston S
Page 55 and 56: 170mm(194mm with SPO)460mm(483mm wi
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RISE AT DEAD ENDDEAD END SETTINGThi
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SIGHT GLASSThe Bailey 1001S Sight G
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AIR CAPACITY CHART (l/s) @ 0.3 Barg
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SATURATED STEAM CAPACITY CHART (kg/
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WATER CAPACITY CHART (l/min) @ 10%
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HOT WATER CAPACITY CHART (kW) FOR A
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G4 DRY SATURATED STEAM CAPACITY - K
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G4 PIPE SIZINGCAPACITIES FOR STEAM
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AIR CAPACITIESInletPressure(Barg)Ou
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WATER CAPACITIESPressureDifferentia
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SATURATED STEAM CAPACITIESInletPres
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SpringSelectionCharts78
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716 SPRING SELECTIONDN15 Spring Ran
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Safety Systems UK Ltd.Sharp Street,
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Bailey Technical Catalogue - Safety Systems UK Ltd

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