IPE-EP-5-3-15

IPE Engineering Practice IPE-EP-5-3-15

Document number: IPE-EP-5-3-15 · Section: 5 — Piping

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Rupture Disk Devices 16) (*)Pressure Fluctuations (static, cyclic, pulsating): Specify cyclic or pulsating service when applicable. Cycling service is considered as a large amplitude and low frequency. Cyclic service with vacuum cycles must be indicated. Pulsating service is considered as small amplitude and high frequency. For certain types of rupture disks, the operating ratio affects the service life in cyclic applications. 17) (*)Superimposed Back Pressure: A rupture disk is a differential pressure device, therefore, this pressure needs to be considered when specifying burst pressure. Additionally, superimposed backpressure is used to determine disk type and construction. (e.g. vacuum / backpressure supports). For disks vented to atmosphere, the superimposed back pressure is atmospheric pressure and it is constant. See paragraph API RP 520 Part 1 for a discussion on the effects of superimposed back pressure on rupture disk selection. 18) (*)Built-up Back Pressure: This pressure is used to determine system back pressure. 19) (*)Back Pressure: This pressure is used in sizing the rupture disk using the coefficient of discharge method. 20) Inlet Vacuum Conditions: Inlet vacuum conditions are used to determine rupture disk type and construction (e.g. vacuum supports). Select and document vacuum units carefully, absolute units have positive values and gage units have negative values. 21) Outlet Vacuum Conditions: A rupture disk is a differential pressure device, therefore, outlet vacuum needs to be considered when specifying the burst pressure. 22) (*)Disk Located Upstream of Pressure Relief Valve (yes/no): This information is needed to verify proper selection (e.g. 3% rule) of non-fragmenting disks. 23) (*)Disk Located Downstream of Pressure Relief Valve (yes/no): This information is needed by the user to verify installation and sizing requirements for this application. 24) (*)Non-fragmenting Disk (yes/no): User must specify non-fragmenting requirement to the manufacturer. 25) (*)Nominal Pipe Size: This information is used to identify the nominal size of the mating fittings. 26) (*)Applicable Flange Standard & Class: This information is used to identify pressure ratings and dimensions of holders. 27) (*)Flange Facing (inlet/outlet): Used to identify the mating flange facing, e.g. RF, FF. 28) Piping Connection (schedule/bore): This is information is used to evaluate flow area and proper selection of holderless disks. 29) (*)Holder Tag No.: Number assigned to rupture disk holder which identifies holder location. 30) Nominal Holder Size: Specify nominal holder size. In some cases nominal holder size may be larger than the relief piping to obtain lower burst pressures. 31) Design Type: Specify holder type, such as insert or full bolting. Holder selection may be based on ease of installation and maintenance or mating connections. Full bolting holders may reduce the heat flow to flange studs in a fire. 32) Model Designator: When known, specify the applicable manufacturer’s model number, name or designator. 33) (*)Quantity Required: Specify quantity of holders required. Preventive maintenance and spares should be considered. 34) Holder Material & Coatings (inlet): User should select an inlet material compatible with process fluids. Coatings and linings are sometimes used to enhance corrosion resistance or reduce product buildup. 35) Holder Material & Coatings (outlet): Outlet holder material may be different from inlet holder material and should be selected based on frequency and duration of exposure to process and downstream fluids.

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Rupture Disk Devices 36) Gage Tap (yes/no) and Size (NPT) (outlet): Gage taps in holder outlets are primarily used to vent and/or monitor the cavity between a rupture disk and a downstream pressure relief valve. 37) Studs and Nuts (yes/no) and Material: Specify if studs and nuts are to be supplied with the rupture disc holder and if so what materials (e.g. alloy or stainless steel). 38) Jackscrews (yes/no): Indicate if jackscrews are required. Jackscrews are used to separate mating flanges to facilitate installation and maintenance of holders. 39) (*)Telltale Assembly (yes/no) and Material: Telltale assemblies typically consist of a pressure gage, excess flow valve, and connecting fittings. These assemblies are installed in holder outlets that are located upstream of pressure relief valves. These devices provide venting and monitoring of the cavity between the disk and valve as specified in API RP 520 Part 1. If other monitoring devices are required, indicate here. 40) Other: Space provided for specifying other accessories. 41) (*)Nominal Disk Size: Specify nominal disk size. In some cases the nominal disk size may be larger than the relief piping to obtain lower burst pressures. 42) (*)Disk Type: Identify preference, if any, for forward acting, reverse acting, or graphite. 43) Model Designator: When known, specify the applicable manufacturer’s model number, name, or designator. 44) (*)Quantity Required: Specify quantity of disks required. Startup, preventive maintenance, and spares should be considered. 45) (*)Manufacturing Range: User to specify the desired manufacturing range. The manufacturing range must always be evaluated before the specified burst pressure is determined to ensure that the marked burst pressure will be within applicable ASME Code pressure limits. Manufacturing ranges generally depend on (a) the specified burst pressure level, (b) the rupture disk design type, and (c) the rupture disk manufacturer. Manufacturing ranges are expressed as (a) plus or minus a percentage of the specified pressure, (b) plus or minus pressure units, or (c) zero percent or no manufacturing range. See API RP 520 Part 1 for clarification. 46) (*)Specified Burst Temperature: User to specify the temperature at which the disk is to be rated and marked. 47) (*)Specified Burst Pressure: A pressure specified by the User taking into consideration manufacturing range, burst tolerance, superimposed back pressure and operating pressure. 48) Maximum Marked Burst Pressure: This pressure is calculated by adding the positive manufacturing range to the specified burst pressure. The maximum marked burst pressure is then verified to meet the vessel or piping protection requirements for single, multiple, fire, or redundant applications. 49) Minimum Marked Burst Pressure: This pressure is calculated by subtracting the negative manufacturing range from the specified burst pressure. The minimum marked burst pressure is used to calculate the operating ratio. 50) Operating Ratio: The operating ratio is used to evaluate the proper selection of the rupture disk and is calculated as follows:(a) For marked pressures above 40 psig the operating ratio is equal to the maximum normal operating pressure divided by the minimum marked burst pressure.(b) For marked pressures 40 psig and below the operating ratio is equal to the maximum normal operating pressure divided by the minimum marked burst pressure less 2 psig. 51) Maximum Flow Resistance Factor (k): When using the total flow resistance method to size relief piping components, specify the maximum flow resistance factor required for the rupture disk. The maximum flow resistance factor is expressed as a velocity head loss.

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Rupture Disk Devices 52) (*)Rupture Disk Materials: The user is responsible for selecting and specifying rupture disk materials that are compatible with system fluids. Verify the selected materials are available for the rupture disk type, pressure, and temperature specified above. 53) Manufacturer’s Data: When available specify the manufacturer’s name and lot number. If the rupture disk has been previously ordered, the manufacturer will have lot number traceability to the previous order rupture disk specifications.

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