ASME SEC 1 pdf download PART PVG REQUIREMENTS FOR ORGANIC FLUID VAPORIZERS
The rules in Part PVG are applicable to organic fluidvaporizers and parts thereof and shall be used in conjunc-tion with the general requirements in Part PG as well aswith the special requirements in the applicable Parts ofthis Section that apply to the method of fabrication used.
PVG-5.1 Materials used in the construction of pres-sure parts for organic fluid vaporizers shall conform toone of the speci fications in Section l and shall be limitedto those for which allowable stress values are given inTables 1A and 1B of Section lI,Part D. Safety valvematerials shall conform to PG-73.2.3.
PVG-5.2 The requirements for materials given in PartPG shall apply in all respects to organic fluid vaporizers.
The rules in the following paragraphs apply speci ficallyto the design of organic fluid vaporizers and parts thereofand shall be used in conjunction with the general require-ments for design in Part PG as well as with the speci ficrequirements for design in the applicable Parts of thisSection that apply to the method of fabrication used.
The Manufacturer shall be responsible for providingin the design the limited heat absorption rates，properfurnace proportions，etc.，which will permit satisfactoryand safe operation of the vaporizers under all conditionsof operation.
Gage glasses shall be of the flat glass type with forgedsteel frames. Gage cocks shall not be used.
PVG-11 DRAIN VALVES
Suitable drain valves of the globe or angle type may beused in lieu of the blowoff valve required in ASME B31.1.
PVG-12.1 Safety valves shall be of a totally enclosedtypesodesignedthatvapors escapingbeyondthevalveseatshall not discharge into the atmosphere，except through anescape pipe that will carry such vapors to a safe point ofdischarge outside of the building. A suitable condenser thatwill condense all the vapors discharged from the safetyvalve may be used in lieu of piping the vapors to the atmo-sphere.The safety valve shall not have a lifting lever. Thevaporizer shall be designed in accordance with the rules inthis Code for a working pressure of at least 40 psi (280 kPa)above the operating pressure at which it will be used. Valvebody drains are not mandatory.
PVG-12.2Safety valves shall be disconnected fromthe vaporizer at least once yearly，when they shall beinspected，repaired if necessary，tested,and then replacedon the vaporizer.
PVG-12.3In order to minimize the loss by leakageof material through the safety valve,a rupture disk maybe installed between the safety valve and the vaporizer,provided the requirements of PVG-12.3.1 through PvG-18.104.22.168 are met.
PVG-12.3.1 The cross-sectional area of the con-nection to a vaporizer shall be not less than the requiredrelief area of the rupture disk.
PVG-12.3.2Every rupture disk shall have a speci-fied bursting pressure at a speci fied temperature，shall bemarked with a lot number，and shall be guaranteed by its manufacturer to burst within 5% (plus or minus) of its specified bursting pressure.
PVG-12.3.3 The specified bursting pressure at the coincident specified temperature shall be determined by bursting two or more specimens from a lot of the same material and of the same size as those to be used. The tests shall be made in a holder of the same form and pressure area dimensions as that with which the disk is to be used.
PVG-12.3.4 A rupture disk may be installed between a safety valve and the vaporizer provided:
PVG-22.214.171.124 The maximum pressure of the range for which the disk is designed to rupture does not exceed the opening pressure for which the safety valve is set or the maximum allowable working pressure of the vessel.
PVG-126.96.36.199 The opening provided through the rupture disk, after breakage, is sufficient to permit a flow equal to the capacity of the attached valve and there is no chance of interference with the proper functioning of the valve; but in no case shall this area be less than the inlet area of the valve.
PVG-188.8.131.52 The space between a rupture disk and the valve should be provided with a pressure gage, try cock, freevent, orasuitable telltale indicator.This arrange- ment permits the detection of disk rupture or leakage