PG-73.2.7 In the design of the body of the valve, consideration shall be given to minimizing the effects of water deposits.
PG-73.2.8 Valves having screwed inlet or outlet connections shall be provided with wrenching surfaces to allow for normal installation without damaging operating parts.
PG-73.2.9 Means shall be provided in the design of all valves for use under this Section, for sealing all external adjustments. Seals shall be installed by the manufacturer, his authorized representative, or an assembler at the time of the initial adjustment. After spring replacement and/or subsequent adjustment, the valve shall be resealed. Seals shall be installed in such a manner as to prevent changing the adjustment without breaking the seal and, in addition, shall serve as a means of identifying the manufacturer, his authorized representative, or the assembler making the adjustment.
PG-73.2.10 Valve capacity may be restricted by restricting the lift of a valve provided the following requirements are met:
(a) The valve size shall be NPS ¾ (DN 20) or larger.
(b) No changes shall be made in the design of the valve except to change the valve lift by use of a lift restraining device described in (c) below.
(c) The restriction of valve capacity shall be permitted only by the use of a lift restraining device which shall limit valve lift and shall not otherwise interfere with flow through the valve. The design of the lift restraining device shall be subject to review by an ASME designee.
(d) The lift restraining device shall be designed so that, if adjustable, the adjustable feature can be sealed. Seals shall be installed by the valve Manufacturer or Assembler at the time of initial adjustment.
(e) Valves shall not have their lifts restricted to a value less than 30% of full rated lift, or 0.080 in. (2 mm).
(f) When sizing and selecting valves, the restricted lift nameplate capacity shall be determined by multiplying the capacity at full rated lift by the ratio of the restricted lift to the full rated lift.
PG-73.2.11 A pressure relief valve over NPS 3 (DN 80), used for pressure greater than 15 psig (100 kPa), shall have a flanged inlet connection or a welded inlet connection. The dimensions of the flanges subjected to boiler pressure shall conform to the applicable ASME standards as given in PG-42. The facing shall be similar to those illustrated in the standard.
PG-73.2.12 The pilot sensing line of pilot-operated pressure relief valves shall be adequately protected from freezing.
PG-73.3 Material Selections
PG-73.3.1 Cast iron seats and disks are not permitted.
PG-73.3.2 Adjacent sliding surfaces such as guides and disks or disk holders shall both be of corrosion-resistant material. Springs of corrosion-resistant material or having a corrosion-resistant coating are required. The seats and disks of pressure relief valves shall be of suitable material to resist corrosion by the lading fluid.
NOTES: The degree of corrosion resistance, appropriate to the intended service, shall be a matter of agreement between the manufacturer and the purchaser.
PG-73.3.3 Materials used in bodies and bonnets or yokes shall be listed in Section II, Parts A and B, and identified in Tables 1A and 1B of Section II Part D, as permitted for Section I construction. Materials used in body to bonnet or body to yoke bolting shall be listed in ASME B16.34. Materials used in all other parts required for the pressure relieving or retaining function shall be
(a) listed in ASME Section II
(b) listed in ASTM Specifications (see Note below) or
(c) controlled by the manufacturer of the pressure relief valve by a specification ensuring control of chemical and physical properties and quality at least equivalent to ASTM Standards (see Note below)
PG-73.3.4 Pressure relief valves may have bronze parts complying with either SB-61, SB-62 or SB-148, provided the maximum allowable stresses and temperatures do not exceed the values given in Table 1B of Section II, Part D, and shall be marked to indicate the class of material used. Such valves shall not be used on superheaters delivering steam at a temperature over 450°F (230°C) for SB-61 and SB-148, and 306°F (I50°C) for SB-62, and shall not be used for high-temperature water boilers.
NOTES: It shall be the manufacturer's responsibility to ensure that the allowable stresses at temperature meet the requirements of Section II, Part D, Appendix 1, Mandatory Basis for Establishing Stress Values in Tables 1A and 1B.
PG-73.4 Inspection of Manufacturing and/or Assembly
PG-73.4.1 A manufacturer shall demonstrate to the satisfaction of an ASME designee that his manufacturing, production, and test facilities and quality control procedures will ensure close agreement between the performance of random production samples and the performance of those valves submitted for capacity certification.
PG-73.4.2 Manufacturing, assembly, inspection, and test operations including capacity, are subject to inspections at any time by an ASME designee.
PG-73.4.3 A Manufacturer or Assembler may be granted permission to apply the V Code Symbol to production pressure relief valves capacity-certified in accordance with PG-69, provided the following tests are successfully completed. This permission shall expire on the sixth anniversary of the date it is initially granted. This permission may be extended for 6-yr periods if the following tests are successfully repeated within the 6-mo period before expiration.
(a) Two sample production pressure relief valves of a size and capacity within the capability of an ASME accepted laboratory shall be selected by an ASME designee. The maximum blowdown for these samples shall not exceed the value specified in the following table:
-
See PDF for table 
The blow down for sample valves designed for use on forced flow steam generators with no fixed steam and waterline or high-temperature water boilers shall not exceed 10% of the set pressure.
(b) Operational and capacity tests shall be conducted in the presence of an ASME designee at an ASME-accepted laboratory. The valve manufacturer or assembler shall be notified of the time of the test and may have representatives present to witness the test.
(c) Should any valve fail to relieve at or above its certified capacity or should it fail to meet performance requirements in PG-72, the test shall be repeated at the rate of two replacement valves, selected in accordance with PG-73.4.3(a), for each valve that failed.
(d) Failure of any of the replacement valves to meet capacity or the performance requirements of this Section shall be cause for revocation within 60 days of the authorization to use the Code symbol on that particular t type of valve. During this period, the Manufacturer or assembler shall demonstrate the cause of such deficiency and the action taken toward against future occurrence.
PG-73.4.4 Use of the Code Symbol Stamp by an assembler indicates the use of original unmodified parts in strict accordance with the instructions of the manufacturer of the valve.
(a) An assembler may transfer original and unmodified pressure relief parts produced by the Manufacturer to other Assemblers, provided the following conditions are met:
(1) both Assemblers have been granted permission to apply the V or UV Code Symbol to the specific valve type in which the parts are to be used
(2) the Quality Control System of the Assembler receiving the pressure relief valve parts shall define the controls for the procurement and acceptance of those parts
(3) the pressure relief valve parts are appropriately packaged, marked, or sealed by the Manufacturer to ensure that the parts are
(a) produced, by the Manufacturer
(b) the parts are original and unmodified
(b) However, an assembler may convert original finished parts by either machining to another finished part or applying a corrosion-resistant coating to valve springs for a specific application under the following conditions:
(1) Conversions shall be specified by the Manufacturer. Drawings and/or written instructions used for part conversion shall be obtained from the Manufacturer and shall include a drawing or description of the converted part before and after the conversion.
(2) The Assembler's quality control system, as accepted by a representative from an ASME-designated organization, must describe in detail the conversion of original parts, provisions for inspection and acceptance, personnel training, and control of current Manufacturer's drawings and/or written instructions.
(3) The Assembler must document each use of a converted part.
(4) The Assembler must demonstrate to the Manufacturer the ability to perform each type of conversion. The Manufacturer shall document all authorizations granted to perform part conversions. The Manufacturer and Assembler shall maintain a file of such authorizations.
(5) For an Assembler to offer restricted lift valves, the Assembler must demonstrate to the satisfaction of the Manufacturer the ability to perform valve lift restrictions. The Manufacturer shall document all authorizations granted to restrict the lift of the valves, and shall maintain records of the lift restrictions made by the Assembler. The Assembler shall maintain a file of such authorizations.
(6) At least annually a review shall be performed by the Manufacturer of an Assembler's system and conversion capabilities. The Manufacturer shall document the results of these reviews. A copy of this documentation shall be kept on file by the Assembler. The review results shall be made available to a representative from an ASME designated organization.
NOTES: Within the requirements of PG-73.4 and PG-73.5, a
manufacturer is defined as a person or organization who is completely responsible for design, material selection, capacity certification, manufacture of all component parts, assembly, testing, sealing, and shipping of pressure relief valves certified under this Section.
An assembler is defined as a person or organization who purchases or receives from a manufacturer the necessary component parts or valves and assembles, adjusts, tests, seals, and ships pressure relief valves certified under this Section at a geographical location other than and using facilities other than those used by the manufacturer.
PG-73.5 Testing by Manufacturers or Assemblers
PG-73.5.1 Pressure Testing. Each pressure relief valve to which the Code Symbol Stamp is to be applied shall be subjected to the following tests by the Manufacturer or Assembler:
(a) The pressure-containing parts of each valve shall be hydrostatically tested at a pressure at least 1.5 times the design pressure of the parts. Parts meeting the following criteria shall be exempt from pressure testing:
(1) the applied stress under hydrostatic test conditions does not exceed 50% of the allowable stress; and
(2) the part is not cast or welded.
(b) Alternatively, testing may be performed pneumatically at a pressure 1.25 times the design pressure of the part. Pneumatic testing can be hazardous; it is therefore recommended that special precautions be taken when conducting a pneumatic test.
(c) Testing may be done in the component or assembled condition.
(d) When the valve is designed for discharging directly to atmosphere, the valve components downstream of the valve disk are exempt from pressure testing.
(e) Valve components downstream of the disk and fully contained within the body are exempt from pressure testing.
(f) These tests shall be conducted after all machining and welding operations on the parts have been completed.
(g) There shall be no sign of leakage.
PG-73.5.2 Every valve shall be tested with steam by the manufacturer or assembler to demonstrate its set point and pressure-containing integrity. The blowdown control elements of the pressure relief valve shall be set to the Manufacturer's specifications.
PG-73.5.2.1 Tests shall be conducted either on equipment that meets the requirements of PG-73.5.6, or on the boiler, by raising the pressure to demonstrate the set pressure.
PG-73.5.2.2 When the valve is beyond the production test equipment capabilities, an alternative test method presented in PG-73.5.2.2.1 or PG-73.5.2.2.2 may be used, provided all of the following conditions are met:
(a) testing the valve at full pressure may cause damage to the valve, or testing of the valve is impractical due to boiler system operational safety considerations
(b) the valve lift has been mechanically verified to meet or exceed the required lift
(c) the blow down control elements of the safety valve are set to the valve manufacturer's specification
(d) the valve design is compatible with the alternative test method selected
PG-73.5.2.2.1 The valve, with its lift temporarily restricted during the test, if required to prevent valve damage, shall be tested on steam to demonstrate set pressure.
PG-73.5.2.2.2 The valve may be fitted with a hydraulic or pneumatic lift assist device and tested on steam at a pressure less than the valve set pressure. The lift assist device and test procedure shall be calibrated to provide the set pressure setting within the tolerance of PG-72.2.
PG-73.5.3 Leak Test
(a) A seat tightness test shall be conducted at maximum expected operating pressure but at a pressure not exceeding the reseating pressure of the valve. When being tested, a valve exhibiting no sign of leakage shall be considered adequately tight.
(b) Closed bonnet pressure relief valves designed for discharge to a closed system shall be tested with a minimum of 30 psig (200 kPa) air or other gas in the secondary pressure zone. There shall be no sign of leakage.
11
- See PDF for table
PG-73.5.4 A manufacturer or assembler shall have a documented program for the application, calibration, and maintenance of test gages.
PG-73.5. Testing time on steam valves shall be sufficient to assure that test results are repeatable and representative of field performance.
PG-73.5.6 Test fixtures and test drums, where applicable, shall be of adequate size and capacity to assure that the observed set pressure is consistent with the stamped set pressure within the tolerance required by PG-72.2.
PG-73.6 Design Requirements. At the time of submission of valves for capacity certification or testing in accordance with PG-69, the ASME designee has the authority to review design for conformity with the requirements of this Section and to reject or require modification of designs that do not conform, prior to capacity testing.
PG-73.7 Code Symbol “V" Stamp. Each pressure relief valve to which the Code “V" symbol (see Fig. PG-105.4) will be applied shall have been fabricated or assembled by a manufacturer or assembler holding a valid Certificate of Authorization (PG-105.2) and c capacity certified in accordance with the requirements of this Section. A Certified Individual (CI) shall provide oversight to assure that each use of the Code “V" symbol on a pressure relief valve is in accordance with the requirements of this Section, and that each use of the Code “V" symbol is documented on a Certificate of Conformance, Form P-8.
PG-73.7.1 Requirements for the Certified Individual (CI). The CI shall
(a) be an employee of the manufacturer or assembler
(b) be qualified and certified by the manufacturer or assembler. Qualifications shall include as a minimum
(1) knowledge of the requirements of this Section for the application of the Code “V" symbol
(2) knowledge of the manufacturer's or assembler's quality program
(3) training commensurate with the scope, complexity, or special nature of the activities to which oversight is to be provided
(c) have a record, maintained and certified by the manufacturer or assembler, containing objective evidence of the qualifications of the CI and the training program provided
PG-73.7.2 Duties of the Certified Individual (CI). The CI shall
(a) verify that each item to which the Code “V" symbol is applied has a current capacity certification and meets all applicable requirements of this Section
(b) review documentation for each lot of items to be stamped to verify, for the lot, that requirements of this Section have been completed
(c) sign the Certificate of Conformance, Form P-8, prior to release of control of the pressure relief valves
PG-73.7.3 Certificate of Conformance, Form P-8
(a) The Certificate of Conformance, Form P-8, shall be filled out by the manufacturer or assembler and signed by the Certified Individual. Multiple duplicate pressure relief valves may be recorded as a single entry, provided the valves are identical and are produced in the same lot.
