§ 52.01-120 Safety valve and safety relief valves (modifies PG-67 through PG-73). ( a ) ( 1 ) Boiler safety valves and safety relief valves must be as indicated in PG-67 through PG-73 of Section I of the ASME BPVC (incorporated by reference; see § 52.01-1) except as noted otherwise in this section.
( 2 ) A safety valve must: ( i ) Be stamped in accordance with PG-110 of Section I of the ASME BPVC;
( ii ) Have its capacity certified by the National Board of Boiler and Pressure Vessel Inspectors;
( iii ) Have a drain opening tapped for not less than 6mm (1 ⁄ 4 in.) NPS; and
( iv ) Not have threaded inlets for valves larger than 51mm (2 in.) NPS.
( 3 ) On river steam vessels whose boilers are connected in batteries without means of isolating one boiler from another, each battery of boilers must be treated as a single boiler and equipped with not less than two safety valves of equal size.
( 4 ) (Modifies PG-70.) The total rated relieving capacity of drum and superheater safety valves as certified by the valve manufacturer must not be less than the maximum generating capacity of the boiler, which must be determined and certified by the boiler manufacturer. This capacity must comply with PG-70 of Section I of the ASME BPVC.
( 5 ) In the event the maximum steam generating capacity of the boiler is increased by any means, the relieving capacity of the safety valves must be checked by an inspector, and, if necessary, valves of increased relieving capacity must be installed.
( 6 ) (Modifies PG-67.) Drum safety valves must be set to relieve at a pressure not in excess of that allowed by the Certificate of Inspection. Where for any reason this is lower than the pressure for which the boiler was originally designed and the revised safety valve capacity cannot be recomputed and certified by the valve manufacturer, one of the tests described in PG-69 of section I of the ASME BPVC must be conducted in the presence of the Inspector to ensure that the relieving capacity is sufficient at the lower pressure.
( 7 ) On new installations the safety valve nominal size for propulsion boilers and superheaters must not be less than 38mm (1.5 in.) nor more than 102mm (4 in.). Safety valves 38mm (1.5 in.) to 114mm (4.5 in.) may be used for replacements on existing boilers. The safety valve size for auxiliary boilers must be between 19mm (3 ⁄ 4 in.) and 102mm (4 in.) NPS. The nominal size of a safety valve is the nominal diameter (as defined in § 56.07-5(b) of this subchapter) of the inlet opening.
( 8 ) Lever or weighted safety valves now installed may be continued in use and may be repaired, but when repairs are not possible, lever or weighted safety valves must be replaced by valves conforming to the requirements of this section.
( 9 ) Gags or clamps for holding the safety valve disk on its seat must be carried on board the vessel at all times.
( 10 ) (Modifies PG-73.2.) Cast iron may be used only for caps and lifting bars. When used for these parts, the elongation must be at least 5 percent in 51mm (2 inch) gage length. Nonmetallic material may be used only for gaskets and packing.
( b ) ( 1 ) (Modifies PG-68.) Superheater safety valves must be as indicated in PG-68 of Section I of the ASME BPVC except as noted otherwise in this paragraph.
( 2 ) The setting of the superheater safety valve must not exceed the design pressure of the superheater outlet flange or the main steam piping beyond the superheater. To prevent damage to the superheater, the drum safety valve must be set at a pressure not less than that of the superheater safety valve setting plus 5 pounds, plus the pressure drop through the superheater and associated piping, including the desuperheater if fitted. See also § 52.01-95(b)(1).
( 3 ) Drum pilot actuated superheater safety valves are permitted provided the setting of the pilot valve and superheater safety valve is such that the superheater safety valve will open before the drum safety valve.
( c ) ( 1 ) (Modifies PG-71.) Safety valves must be installed as indicated in PG-71 of Section I of the ASME BPVC except as noted otherwise in this paragraph (c).
( 2 ) The final setting of boiler safety valves must be checked and adjusted under steam pressure and, if possible, while the boiler is on line and at operating temperatures, to the satisfaction of a marine inspector who, upon acceptance, must seal the valves. This regulation applies to both drum and superheater safety valves of all boilers.
( 3 ) The safety valve body drains required by PG-71 of Section I of the ASME BPVC must be run as directly as possible from the body of each safety valve, or the drain from each safety valve may be led to an independent header common only to boiler safety valve drains. No valves of any type may be installed in the leakoff from drains or drain headers and they must be led to suitable locations to avoid hazard to personnel.
( d ) ( 1 ) (Modifies PG-72.) The operation of safety valves must be as indicated in PG-72 of Section I of the ASME BPVC except as noted in paragraph (d)(2) of this section.
( 2 ) (Modifies PG-73.) The lifting device required by PG-73.1.3 of Section I of the ASME BPVC must be fitted with suitable relieving gear so arranged that the controls may be operated from the fireroom or engine room floor.
[CGFR 68-82, 33 FR 18815, Dec. 18, 1968, as amended by CGD 81-79, 50 FR 9433, Mar. 8, 1985; USCG-2003-16630, 73 FR 65161, Oct. 31, 2008]