ASME SEC VIII D3 PART KR-1.pdf

Part KR

PRESSURE RELIEF DEVICES

COPYRIGHT American Society of Mechanical EngineersLicensed by Information Handling ServicesCOPYRIGHT American Society of Mechanical EngineersLicensed by Information Handling Services

PART KR

Article KR-1 General Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154KR-100 Protection Against Overpressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154KR-110 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154KR-120 Types of Overpressure Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155KR-121 Rupture Disk Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155KR-122 Pressure Relief Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155KR-123 Combinations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155KR-124 Requirements for Pressure Retaining Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155KR-125 Inherent Overpressure Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-126 Intensifier Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-130 Size of Openings and Nozzles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-140 Intervening Stop Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-141 Dual Overpressure Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-150 Permissible Overpressures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-160 Set Pressures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-161 Single Pressure Relief Device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-162 Multiple Pressure Relief Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156KR-163 Pressure Effects to Be Included in the Setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

Article KR-2 Requirements for Rupture Disk Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158KR-200 Materials for Rupture Disk Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158KR-201 Marking and Stamping Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158KR-202 Burst Testing Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158KR-210 Flow Capacity Rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158KR-220 Rupture Disk Devices Used in Combination With Flow Capacity Certified

Pressure Relief Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159KR-221 Rupture Disk Devices Installed Upstream of Flow Capacity Certified Pressure

Relief Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159KR-222 Rupture Disk Devices Installed Downstream of Flow Capacity Certified Pressure

Relief Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

Article KR-3 Requirements for Pressure Relief Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-300 General Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-310 Design Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-311 Guiding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-312 Spring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-313 Seat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-314 Body and Pressure Retaining Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-315 Bonnet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-316 Inlet Fittings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-317 Sealing of Valve Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160KR-318 Drain Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

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KR-320 Material Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-321 Seats and Disks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-322 Guides and Springs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-323 Pressure Retaining Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-324 Nonpressure-Retaining Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-330 Inspection of Manufacturing and/or Assembly of Pressure Relief Valves. . . . . . . . . . 161KR-331 Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-332 Verification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-340 Production Testing by Manufacturers and Assemblers. . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-341 Hydrostatic Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161KR-342 Test Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162KR-343 Leak Tightness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162KR-344 Instrumentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162KR-345 Set Pressure Tolerance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162KR-346 Flow Capacity Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

Article KR-4 Marking and Stamping Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163KR-400 Marking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163KR-401 Marking of Pressure Relief Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163KR-402 Marking of Rupture Disk Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163KR-403 Marking of Pressure Relief Valves in Combination With Rupture Disk Devices . . . 164KR-410 Use of Code Symbol Stamp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Article KR-5 Certification of Flow Capacity of Pressure Relief Valves . . . . . . . . . . . . . . . . . . . . . 165KR-500 Flow Capacity Certification Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165KR-501 Fluid Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165KR-502 Test Pressures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165KR-510 Recertification Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165KR-520 Procedures for Flow Capacity Certification Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165KR-521 Three-Valve Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165KR-522 Slope Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165KR-523 Coefficient of Discharge Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166KR-523.1 Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166KR-523.2 Number of Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166KR-523.3 Calculation Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166KR-523.4 Determining Coefficients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166KR-523.5 Flow Capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166KR-530 Flow Capacity Conversions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167KR-531 Gas and Air Service. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167KR-532 Liquid and High Pressure Gas Service. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167KR-540 Flow Capacity Certification Testing Requirements for Test Facilities. . . . . . . . . . . . . 168KR-550 Test Data Reports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168KR-560 Certification of Flow Capacity of Pressure Relief Valves in Combination With

Rupture Disk Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168KR-561 Test Media and Test Pressures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168KR-562 Sizes of Test Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168KR-563 Testing Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168KR-570 Optional Testing of Rupture Disk Devices and Pressure Relief Valves. . . . . . . . . . . 169

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KR-571 Larger Sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169KR-572 Higher Pressures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

FiguresKR-401 Official Symbol for Stamp to Denote the American Society of Mechanical

Engineers’ Standard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163KR-523.3 ConstantC for Gas Versus Specific Heat Ratiok p CP/CV . . . . . . . . . . . . . . . . . . . . 167

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01

ARTICLE KR-1GENERAL REQUIREMENTS

KR-100 PROTECTION AGAINSTOVERPRESSURE

All pressure vessels within the scope of this Divisionshall be provided with protection against overpressureaccording to the requirements of this Part. Combinationunits (such as heat exchangers with shells designed forlower pressures than the tubes) shall be protected againstoverpressure from internal failures. The User or hisDesignated Agent shall be responsible for establishinga procedure for sizing and/or flow capacity calculationsfor the device and associated flow paths, as well aschanges in fluid conditions and properties as appropriate.These calculations shall be based on the most severecredible combinations of final compositions and re-sulting temperature. Alternatively, sizing shall be deter-mined on an empirical basis by actual capacity testswith the process in question at expected relievingconditions. The User shall be responsible for providingor approving the assumptions used in all flow capacitycalculations.

KR-110 DEFINITIONS

Unless otherwise defined in this Division, definitionsrelating to pressure relief devices in Section 2 of ASMEPTC 25, Pressure Relief Devices, shall apply.

Assembler:a person or organization who purchases orreceives from a Manufacturer the necessary componentparts or valves and who assembles, adjusts, tests, seals,and ships pressure relief valves certified under thisDivision, at a geographical location other than and usingfacilities other than those used by the Manufacturer. AnAssembler may be organizationally independent of aManufacturer, or may be wholly or partly owned bya Manufacturer.

coincident disk temperature(supplied to the rupturedisk manufacturer): the expected temperature of thedisk when a specified overpressure condition exists,and the disk is expected to rupture.

combination device:one rupture disk in series withone pressure relief valve.

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compressibility factor:the ratio of the specific volumeof a given fluid at a particular temperature and pressureto the specific volume of that fluid as calculated byideal gas laws at that temperature and pressure.

gas: for the purpose of Part KR, a gas shall be definedas a fluid that undergoes a significant change in densityas it flows through the pressure relief device.

liquid: for the purpose of Part KR, a liquid shall bedefined as a fluid that does not undergo a significantchange in density through the pressure relief device.

Manufacturer: within the requirements of Part KR, aManufacturer is defined as a person or organizationwho is completely responsible for design, materialselection, capacity certification when required, and man-ufacture of all component parts, assembly, testing,sealing, and shipping of pressure relief valves certifiedunder this Division of the Code.

manufacturing design range:a range of pressure withinwhich a rupture disk will be stamped as agreed uponbetween the rupture disk Manufacturer, and the Useror his Agent. The range shall have a minimum and amaximum burst pressure specified. If the rupture diskis used as the primary safety relief device, cautionshould be taken in determining the disk manufacturingrange so that the stamped bursting pressure of the diskwill not exceed the design pressure of the vessel.

nonreclosing pressure relief device:a pressure reliefdevice designed to remain open after operation.

overpressure:a pressure increase over the set pressureof a pressure relief valve, usually expressed as apercentage of set pressure.

pressure relief valve:a passive pressure relief devicethat is actuated by static inlet pressure. The openingis characterized by a rapid opening (pop action), orby opening in proportion to the difference between thestatic pressure and the set pressure of the valve, de-pending on the valve design and the application. Apressure relief valve is also designed to reclose toprevent further discharge of fluid after the inlet pressuredecreases below the set pressure of the valve. Also


KR-110 PART KR — PRESSURE RELIEF DEVICES KR-124

referred to as a safety relief valve, safety valve, reliefvalve, and pop off valve.

pressure relief valve set pressure:that pressure whichcauses the valve stem to lift at least 5% of its fulltravel.

rupture disk: the rupture disk is the pressure retainingand pressure sensitive element of a rupture disk device.The failure of the rupture disk is the cause of theopening of the rupture disk device. Rupture disksneed not be flat round disks, as long as their designconfiguration meets the design burst pressure and flowcapacity requirements.

rupture disk device:a nonreclosing differential pressurerelief device actuated by inlet static pressure and de-signed to function by the bursting of a pressure retainingdisk. The rupture disk device includes the rupture disk,the rupture disk holder, and all other components thatare required for the device to function in the prescribedmanner. The holder is the structure which encloses,clamps, and seals the rupture disk in position.

KR-120 TYPES OF OVERPRESSUREPROTECTION

Pressure relief valves, rupture disks, flow paths, orvents directly or indirectly open to the atmosphere, orinherent overpressure protection in accordance withKR-125, may be used for overpressure protection. Theoverpressure limits specified in KR-150 shall apply tothese devices.

KR-121 Rupture Disk Devices

Because of the high pressures associated with thisDivision, it may be impractical to accomplish full-scaleflow capacity performance testing and certification ofpressure relieving devices. For this reason, rupture diskdevices may be the more commonly used means ofoverpressure protection for vessels within the scope ofthis Division. All rupture disks shall meet the require-ments of Article KR-2.

The use of rupture disk devices may be advisablewhen very rapid rates of pressure rise may be encoun-tered, or where the relief device must have intimatecontact with the process stream. Intimate contact maybe required to overcome inlet line fouling problems orto ensure that the temperature of the disk is the sameas the interior temperature of the vessel.

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KR-122 Pressure Relief Valves

All pressure relief valves shall meet the requirementsof Article KR-3, and shall be flow capacity performancetested and certified in accordance with Article KR-5,except in the case where their opening is not requiredto satisfy the overpressure limits given in KR-150. SeeKR-123(c) for further discussion about the use of reliefvalves in parallel with rupture disks.

KR-123 Combinations

A rupture disk device used in combination with apressure relief valve may be advisable on vessels con-taining substances that may render a pressure reliefvalve inoperative by fouling, or where a loss of valuablematerial by leakage should be avoided, or where contam-ination of the atmosphere by leakage of noxious, flam-mable, or hazardous fluids must be avoided.

(a) Multiple rupture disk devices in parallel shallnot be used on the inlet side of a pressure relief valve.

(b) When a combination device is used, both therupture disk device and the pressure relief valve shallmeet the applicable requirements of Part KR. Therupture disk device shall be installed to prevent frag-ments from the rupture disk from interfering withthe proper operation of the pressure relief valve. Foradditional requirements, see KR-220 and KR-340.

(c) A rupture disk device may be used in parallelwith a pressure relief valve whose set pressure is lowerthan the rupture disk when it is important to limit thequantity of a release or it is impractical to certify theflow capacity of the pressure relief valve under therules of this Division. The calculated flow capacity ofthe rupture disk device acting alone shall be adequateto meet the requirements of KR-150, and the rupturedisk device shall meet all the applicable requirementsof this Part. With the exception of the flow capacitycertification, the pressure relief valve shall meet all therequirements of this Part.

KR-124 Requirements for Pressure RetainingComponents

All components subject to the design pressure shallmeet the requirements of this Division; requirementsfor the pressure relief valve seat, spring, and valvestem are given in Article KR-3, and requirements forthe rupture disk component are given in Article KR-2. Components that are subject to pressures lower thanthe design pressure when the pressure relief deviceopens shall meet the requirements of this Division orother Divisions of Section VIII.


KR-125 2001 SECTION VIII — DIVISION 3 KR-162

KR-125 Inherent Overpressure Protection

Overpressure protection need not be provided whenthe source of pressure is external to the vessel andwhen the source of pressure is under such positivecontrol that the pressure in the vessel cannot exceedthe design conditions except as permitted in KR-150.

KR-126 Intensifier Systems

In the case where a vessel is pressurized by anintensifier system whose output pressure to the vesselis a fixed multiple of the supply pressure, the pressurerelief device may be located on the low pressure supplyside of the intensifier if all the following requirementsare met.

(a) There shall be no intervening stop valves orcheck valves between the driving chamber(s) and therelief device(s).

(b) Heating of the discharge fluid shall be controlledto prevent further pressure increase which would exceedvessel design conditions.

(c) The discharge fluid shall be stable and nonreactive(water, hydraulic fluid, etc.).

(d) The material being processed in downstreamequipment is stable and nonreactive, or is provided witha suitable secondary vent system which will effectivelyprevent transfer of secondary energy sufficient to over-pressure the vessel.

The Designer is cautioned to consider the effects ofleaking check valves in such systems.

KR-130 SIZE OF OPENINGS ANDNOZZLES

The flow characteristics of the entire pressure reliev-ing system shall be part of the relieving capacitycalculations. The size of nozzles and openings shallnot adversely affect the proper operation of the pressurerelieving device.

KR-140 INTERVENING STOP VALVES

There shall be no intervening stop valves between thevessel and any overpressure protection device associatedwith the vessel, except as permitted in KR-141.

A full-area stop valve may be placed on the dischargeside of a pressure relieving device when its dischargeis connected to a common header with other dischargelines from other pressure relief devices on vessels thatare in operation, so that this stop valve when closedwill prevent a discharge from any connected operating

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vessels from backing up beyond the valve so closed.Such a stop valve shall be so arranged that it can belocked or sealed in either the open or closed positionby an authorized person. Under no condition shall thisvalve be closed while the vessel is in operation.

KR-141 Dual Overpressure Protection

Where it is desirable to perform maintenance onrelief devices without shutting down the process, afull-area three-way transfer valve may be installed onthe inlet of the relief device(s). The design of thetransfer valve and relief devices must be such that therequirements of KR-150 are met at any position of thetransfer valve. Alternatively, the User may elect toinstall stop valves in each branch, but so controlledthat one branch is open at all times and the requirementsof KR-150 are always met while the process is inoperation.

KR-150 PERMISSIBLE OVERPRESSURES

The aggregate capacity of the safety relief devices,open flow paths, or vents shall be sufficient to preventoverpressures in excess of 10% above the design pres-sure of the vessel when the safety relief devices aredischarging.

The Designer shall consider the effects of the pressuredrop in the overpressure protection system piping duringventing when specifying the set pressures and flowcapacities of pressure relief valves and rupture diskdevices. When multiple pressure relief devices candischarge through a common stack or vent path, themaximum back pressure that can exist during simultane-ous releases at the exit of each pressure relief deviceshall not impair its operation.

KR-160 SET PRESSURES

KR-161 Single Pressure Relief Device

A single safety relief device shall open at a nominalpressure not exceeding the design pressure of the vesselat the operating temperature, except as permitted inKR-162.

KR-162 Multiple Pressure Relief Devices

If the required discharging capacity is supplied bymore than one device, only one need be set to operateat a pressure not exceeding the design pressure of thevessel. The additional device or devices may be set at


KR-162 PART KR — PRESSURE RELIEF DEVICES KR-163

a higher pressure but not to exceed 105% of the designpressure of the vessel. The requirements of KR-150shall also apply.

KR-163 Pressure Effects to Be Included in theSetting

The pressure at which any device is set shall includethe effects of superimposed back pressure through thepressure relief device and the vent system (see KR-150).

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ASME SEC VIII D3 PART KR-1.pdf

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