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    1.1 Pmta

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    gabao123
    This document outlines requirements and guidelines for pressure relief devices and pressure relief valves. Some key points include: - The rated capacity of a pressure relief device is the value stamped by the manufacturer and guaranteed to relieve pressure as specified. - Pressure relief devices must have sufficient capacity to prevent pressure rises above certain thresholds during relief events. - Pressure relief valve set pressures must be within specified tolerances of the maximum allowable working pressure. - Pressure relief devices must be installed properly with consideration for flow characteristics, intervening valves, and discharge piping. - Pressure relief valves must meet minimum mechanical requirements like spring compression and material specifications.

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    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    1.1 Pmta

    Uploaded by

    gabao123
    160 views2 pages
    This document outlines requirements and guidelines for pressure relief devices and pressure relief valves. Some key points include: - The rated capacity of a pressure relief device is the value stamped by the manufacturer and guaranteed to relieve pressure as specified. - Pressure relief devices must have sufficient capacity to prevent pressure rises above certain thresholds during relief events. - Pressure relief valve set pressures must be within specified tolerances of the maximum allowable working pressure. - Pressure relief devices must be installed properly with consideration for flow characteristics, intervening valves, and discharge piping. - Pressure relief valves must meet minimum mechanical requirements like spring compression and material specifications.

    Original Description:

    part asme code, where say about maximun allowable open relief pressure

    Original Title

    1.1 PMTA

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    This document outlines requirements and guidelines for pressure relief devices and pressure relief valves. Some key points include: - The rated capacity of a pressure relief device is the value stamped by the manufacturer and guaranteed to relieve pressure as specified. - Pressure relief devices must have sufficient capacity to prevent pressure rises above certain thresholds during relief events. - Pressure relief valve set pressures must be within specified tolerances of the maximum allowable working pressure. - Pressure relief devices must be installed properly with consideration for flow characteristics, intervening valves, and discharge piping. - Pressure relief valves must meet minimum mechanical requirements like spring compression and material specifications.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    160 views2 pages

    1.1 Pmta

    Uploaded by

    gabao123
    This document outlines requirements and guidelines for pressure relief devices and pressure relief valves. Some key points include: - The rated capacity of a pressure relief device is the value stamped by the manufacturer and guaranteed to relieve pressure as specified. - Pressure relief devices must have sufficient capacity to prevent pressure rises above certain thresholds during relief events. - Pressure relief valve set pressures must be within specified tolerances of the maximum allowable working pressure. - Pressure relief devices must be installed properly with consideration for flow characteristics, intervening valves, and discharge piping. - Pressure relief valves must meet minimum mechanical requirements like spring compression and material specifications.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
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    of 2

    2013 SECTION VIII - DIVISION 1

    UG-134

    (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) T h e r a t e d p r e s s u r e r e l i e v i n g c a p a c i t y o f a
    pressure relief valve for other than steam or air shall be
    determined by the method of conversion given in
    Mandatory 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:

    The Combination Capacity Factor shall be used as a


    multiplier to make appropriate changes in the ASME rated
    relieving capacity of the pressure relief valve in all sizes of
    the design. The value of the Combination Capacity Factor
    shall not be greater than one. The Combination Capacity
    Factor shall apply only to combinations of the same design
    of pressure relief valve and the same design of nonreclosing pressure relief device as those tested.
    (-e) The test laboratory shall submit the test results to the ASME designated organization for acceptance
    of the Combination Capacity Factor.61
    (b) Optional Testing of Nonreclosing Pressure Relief Devices and Pressure Relief Valves
    (1) If desired, a valve Manufacturer or a nonreclosing
    pressure relief device Manufacturer may conduct tests in
    the same manner as outlined in (a)(4)(-c) and (a)(4)(-d)
    above using the next two larger sizes of the design of nonreclosing pressure relief device and pressure relief valve
    to determine a Combination Capacity Factor applicable
    to larger sizes. If a greater Combination Capacity Factor
    is established and can be certified, it may be used for all
    larger sizes of the combination, but shall not be greater
    than one.
    (2) If desired, additional tests may be conducted at
    higher pressures in accordance with (a)(4)(-c) and
    (a)(4)(-d) above to establish a maximum Combination Capacity Factor to be used at all pressures higher than the
    highest tested, but shall not be greater than one.

    UG-133

    UG-132

    (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.

    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) P r e s s u r e r e l i e f d e v i c e s a s p e r m i t t e d i n
    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 w ith
    Nonmandatory 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.

    UG-134

    PRESSURE SETTINGS AND


    PERFORMANCE REQUIREMENTS

    (a) When a single pressure relief device is used, the set


    pressure61 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.
    (b) F o r p r e s s u r e r e l i e f d e v i c e s p e r m i t t e d i n
    UG-125(c)(2) as protection against excessive pressure
    caused by exposure to fire or other sources of external
    99

    UG-134

    UG-136

    2013 SECTION VIII - DIVISION 1

    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) See below.
    (1) 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 (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 and including 40 psi (300 kPa) and 5% of marked burst pressure
    above 40 psi (300 kPa).
    (f) The set pressure tolerance for pin devices shall not
    exceed 2 psi (15 kPa) of marked set pressure up to and
    including 40 psi (300 kPa) and 5% of marked set pressures above 40 psi (300 kPa) at specified pin temperature.
    (g) 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 flowrated pressure in a way that either would interfere with the measurement of capacity or would result
    in damage.

    UG-135

    (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 Nonmandatory 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 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 Nonmandatory
    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 vessels 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
    d e v i c es . [ S e e U G - 1 3 6 ( a ) ( 8 ) a n d N o n m a n d a t o r y
    Appendix M.]

    INSTALLATION

    UG-136

    (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) See below:
    (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 characteristics 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 Nonmandatory Appendix M).62

    MINIMUM REQUIREMENTS FOR


    PRESSURE RELIEF VALVES

    (a) Mechanical Requirements


    (1) The design shall incorporate guiding arrangements necessary to ensure consistent operation and
    tightness.
    (2) The spring shall be designed so that the full lift
    spring compression shall be no greater than 80% of the
    nominal solid deflection. The permanent set of the spring
    (defined as the difference between the free height and
    height measured 10 min after the spring has been compressed solid three additional times after presetting at
    room temperature) shall not exceed 0.5% of the free
    height.
    For direct spring loaded valves that have set pressures above the maximum pressure used in the capacity
    certification tests, the spring force ratio shall not exceed
    1.1 times the spring force ratio of the valve with the highest set pressure that was used in the capacity certification
    tests. For direct spring loaded valves that have orifices larger than the largest size used in the capacity certification
    tests, the spring force ratio shall not exceed 1.1 times the
    100

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