(7) specified disk temperature _____ °F (°C);
(8) minimum net flow area _____sq in. (sq mm);
(9) certified flow resistance (one or more as applicable);
(a) KRG _____ for rupture disk certified on air or gases;
(b) KRL _____ for rupture disk certified on liquid;
(c) KRGL _____ for rupture disk certified on air or gases, and liquid;
(10) ASME symbol as shown in Fig. UG-129.2;
(11) year built, or alternatively, a coding may be marked on the rupture disk such that the rupture disk device Manufacturer can identify the year the rupture disk device was assembled and tested.
Items (1), (2), (5), (10), and (11) above and flow direction shall also be marked on the rupture disk holder.
(f) Pin Devices and Pin Actuated Pilot Operated Pressure Relief Devices. Pin devices shall be plainly marked by the Manufacturer with the required data in such a way that the marking will not be obliterated in service. The marking may be placed on the device housing or on a plate or plates that satisfies the requirements of UG-119. The marking shall include the following:
(1) the name, or an acceptable abbreviation of the Manufacturer
(2) Manufacturer's design or type number
(3) NPS (DN) size (the nominal pipe size of the device inlet)
(4) set pressure psi (kPa)
(5) flow direction
(6) pin to pin device identifier
(7) for capacity certified devices
(a) lb/hr of saturated steam at an overpressure 10% or 3 psi (20 kPa), whichever is greater for devices certified on steam complying with UG-131(b), or
(b) gal/min of water at 70°F (20°C) at an overpressure of 10% or 3 psi (20 kPa), whichever is greater for devices certified on water, or
(c) SCFM [standard cubic feet per minute at 60°F and 14.7 psia (20°C and 101 kPa)], or lb/min, of air at an overpressure of 10% or 3 psi, whichever is greater. Devices that are capacity certified in accordance with UG-131 (c) (2) shall be marked “at 20% overpressure."
(d) In addition to one of the fluids specified above, the Manufacturer may indicate the capacity in other fluids (see Appendix 11).
(8) for flow resistance certified devices:
(a) minimum net flow area _____ in2 (mm2)
(b) certified flow resistance (one or more as applicable)
(1) KRG _____ for pin devices certified on air or gases
(2) KRL _____ for pin devices certified on liquid
(3) KRGL _____ for pin devices certified on air or gases, and liquid
(9) ASME symbol as shown in Fig. UG-129.2
(10) year built, or alternatively, a coding may be marked on the device such that the device Manufacturer can identify the year the device was tested
(11) The pin shall be marked according to one of the following methods:
(a) for pin devices using a replaceable pin to control set pressure, the pin shall be marked with its lot number, pin temperature °F (°C) and the information required by (f) (l), (f) (4), (f) (6), (f) (10), or
Note: When the pin size or configuration does not permit the use of an attached metal tag, a metal tag may be attached using a nonmetallic connector with an adhesive that complies with Appendix 18 of this Division.
(b) for pin devices that are single use and permanently assembled, the marking requirements of (f) (8) (a), (f) (8) (b), and (f) (11) (a) shall be applied to the device, or
(c) for pin devices that have a replaceable pin within the sealed body per UG-138, the pin shall be marked with its lot number.
(g) Spring Loaded Nonreclosing Pressure Relief Devices. Spring loaded nonreclosing pressure relief devices shall be marked in accordance with (a) above except that the Code Symbol Stamp is to be applied only when the capacity has been established and certified in accordance with UG-127 (c) (3) and all other requirements of UG-130 have been met.
(h) For units other than those included above, see U-4.
UG-130 CODE SYMBOL STAMP
Each pressure relief device
59 to which the Code Symbol (see Figs. UG-129.1 and UG-129.2) will be applied shall have been fabricated or assembled by a Manufacturer or Assembler holding a valid Certificate of Authorization (UG-117) and capacity certified in accordance with the requirements of this Division. A Certified Individual (CI) shall provide oversight as required by UG-117(a). Each use of the Code Symbol shall also be documented on a Certificate of Conformance Form UV-1 or UD-1, as appropriate.
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UG-133 DETERMINATION OF PRESSURE RELIEVING REQUIREMENTS
(a) Except as permitted in (b) below, the aggregate capacity of the pressure relief devices connected to any vessel or system of vessels for the release of a liquid, air, steam, or other vapor shall be sufficient to carry off the maximum quantity that can be generated or supplied to the attached equipment without permitting a rise in pressure within the vessel of more than 16% above the maximum allowable working pressure when the pressure relief devices are blowing.
(b) Pressure relief devices as permitted in UG-125(c)(2), as protection against excessive pressure caused by exposure to fire or other sources of external heat, shall have a relieving capacity sufficient to prevent the pressure from rising more than 21% above the maximum allowable working pressure of the vessel when all pressure relief devices are blowing.
(c) Vessels connected together by a system of adequate piping not containing valves which can isolate any vessel, and those containing valves in compliance with Appendix M, M-5, may be considered as one unit in figuring the required relieving capacity of pressure relief devices to be furnished.
(d) Heat exchangers and similar vessels shall be protected with a pressure relief device of sufficient capacity to avoid overpressure in case of an internal failure.
(e) The official rated capacity, or the certified flow resistance and minimum net flow area, of a pressure relief device shall be that which is stamped on the device and guaranteed by the Manufacturer.
(f) The rated pressure relieving capacity of a pressure relief valve for other than steam or air shall be determined by the method of conversion given in Appendix 11.
(g) The relieving capacity of a pressure relief device for compressible fluids may be prorated at any relieving pressure greater than 1.10p, as permitted under UG-125, by applying a multiplier to the official relieving capacity as follows:
(U.S. Customary Units)
(SI Units)
where
P = relieving pressure, psig(kPa gage)
p = set pressure, psig(kPa gage)
For steam pressures above 1,500 psig (10 MPa gage), the above multiplier is not applicable. For steam valves with relieving pressures greater than 1,500 psig (10 MPa gage) and less than or equal to 3,200 psig (22.1 MPa gage), the capacity at relieving pressures greater than 1.10p shall be determined using the equation for steam and the correction factor for high pressure steam in UG-131 (e) (2) with the permitted absolute relieving pressure and the coefficient K for that valve design.
(h) When sizing and selecting valves, the restricted lift nameplate capacity shall be determined by multiplying the capacity at full rated lift as defined in UG-131 (e) (3) by the ratio of the restricted lift to the full rated lift.
UG-134 PRESSURE SETTINGS AND
PERFORMANCE REQUIREMENTS
(a)
When a single pressure relief device is used, the set pressure
61 marked on the device shall not exceed the maximum allowable working pressure of the vessel. When the required capacity is provided in more than one pressure relief device, only one pressure relief device need be set at or below the maximum allowable working pressure, and the additional pressure relief devices may be set to open at higher pressures but in no case at a pressure higher than 105% of the maximum allowable working pressure, except
as provided in (b) below.
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(b) For pressure relief devices permitted in UG-125(c)(2) as protection against excessive pressure caused by exposure to fire or other sources of external heat, the device marked set pressure shall not exceed 110% of the maximum allowable working pressure of the vessel. If such a pressure relief device is used to meet the requirements of both UG-125(c) and UG-125(c)(2), the device marked set pressure shall not be over the maximum allowable working pressure.
(c) The pressure relief device set pressure shall include the effects of static head and constant back pressure.
(d) (l) The set pressure tolerance for pressure relief valves shall not exceed ±2 psi (15 kPa) for pressures up to and including 70 psi (500 kPa) and ±3% for pressures above 70 psi (500 kPa), except as covered in (d)(2) below.
(2) The set pressure tolerance of pressure relief valves which comply with UG-125(c)(3) shall be within -0%, +10%.
(e) The burst pressure tolerance for rupture disk devices at the specified disk temperature shall not exceed ±2 psi (15 kPa) of marked burst pressure up to 40 psi (300 kPa) and ±5% of marked burst pressure 40 psi (300 kPa) and over.
(f) Pressure relief valves shall be designed and constructed such that when installed per UG-135, the valves will operate without chattering and shall not flutter at the flow-rated pressure in a way that either would interfere with the measurement of capacity or would result in damage.
UG-135 INSTALLATION
(a) Pressure relief devices intended for relief of compressible fluids shall be connected to the vessel in the vapor space above any contained liquid or to piping connected to the vapor space in the vessel which is to be protected. Pressure relief devices intended for relief of liquids shall be connected below the liquid level. Alternative connection locations are permitted, depending on the potential vessel overpressure scenarios and the type of relief device selected, provided the requirements of UG-125(a)(2) and UG-125(c) are met.
(b)(1) The opening through all pipe, fittings and nonreclosing pressure relief devices (if installed) between a pressure vessel and its pressure relief valve shall have at least the area of the pressure relief valve inlet. The characteristic of this upstream system shall be such that the pressure drop will not reduce the relieving capacity below that required or adversely affect the proper operation of the pressure relief valve.
(2) The opening in the vessel wall shall be designed to provide unobstructed flow between the vessel and its pressure relief device (see Appendix M).
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(c) When two or more required pressure relief devices are placed on one connection, the inlet internal cross-sectional area of this connection shall be either sized to avoid restricting flow to the pressure relief devices or made at least equal to the combined inlet areas of the safety devices connected to it. The flow characteristics of the upstream system shall satisfy the requirements of (b) above. (See Appendix M.)
(d) There shall be no intervening stop valves between the vessel and its pressure relief device or devices, or between the pressure relief device or devices and the point of discharge, except:
(1) when these stop valves are so constructed or positively controlled that the closing of the maximum number a of block valves possible at one time will not reduce the pressure relieving capacity provided by the unaffected pressure relief devices below the required relieving capacity; or
(2) under conditions set forth in Appendix M.
(e) The pressure relief devices on all vessels shall be so installed that their proper functioning will not be hindered by the nature of the vessel's contents.
(f) Discharge lines from pressure relief devices shall be designed to facilitate drainage or shall be fitted with drains to prevent liquid from lodging in the discharge side of the pressure relief device, and such lines shall lead to a safe place of discharge. The size of the discharge lines shall be such that any pressure that may exist or develop will not reduce the relieving capacity of the pressure relief devices below that required to properly protect the vessel, or adversely affect the proper operation of the pressure relief devices. [See UG- 136(a)(8) and Appendix M.]
