[Title 46 CFR 52.01-120]
[Code of Federal Regulations (annual edition) - October 1, 2006 Edition]
[Title 46 - SHIPPING]
[Chapter I - COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)]
[Subchapter F - MARINE ENGINEERING]
[Part 52 - POWER BOILERS]
[Subpart 52.01 - General Requirements]
[Sec. 52.01-120 - Safety valves and safety relief valves (modifies PG-67]
[From the U.S. Government Publishing Office]


46SHIPPING22006-10-012006-10-01false52.01-120Sec. 52.01-120SHIPPINGCOAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)MARINE ENGINEERINGPOWER BOILERSGeneral Requirements
Sec. 52.01-120  Safety valves 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 the ASME Code except as noted 
otherwise in this section.
    (2) A safety valve must:
    (i) Be stamped in accordance with PG-110 of the ASME Code;
    (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 shall be treated as a single boiler and equipped with not less 
than two safety valves of equal size.

[[Page 131]]

    (4) (Modifies PG-70.) The total rated relieving capacity of drum and 
superheater safety valves as certified by the valve manufacturer shall 
not be less than the maximum generating capacity of the boiler which 
shall be determined and certified by the boiler manufacturer. This 
capacity shall be in compliance with PG-70 of the ASME Code.
    (5) In the event the maximum steam generating capacity of the boiler 
is increased by any means, the relieving capacity of the safety valves 
shall be checked by an inspector, and, if determined to be necessary, 
valves of increased relieving capacity shall be installed.
    (6) (Modifies PG-67.) Drum safety valves shall 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-70(3) of the ASME Code shall be 
conducted in the presence of the Inspector to insure 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\1/2\ 
in.) nor more than 102mm (4 in.). Safety valves 38mm (1\1/2\ in.) to 
114mm (4\1/2\ 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 the inlet opening.
    (8) Lever or weighted safety valves now installed may be continued 
in use and may be repaired, but when renewals are necessary, lever or 
weighted safety valves shall not be used. All such replacements shall 
conform to the requirements of this section.
    (9) Gags or clamps for holding the safety valve disk on its seat 
shall 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 shall be as 
indicated in PG-68 of the ASME Code except as noted otherwise in this 
paragraph.
    (2) The setting of the superheater safety valve shall 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 shall be set at a pressure not less than that of the 
superheater safety valve setting plus 5 pounds minimum plus 
approximately the normal load pressure drop through the superheater and 
associated piping, including the controlled desuperheater if fitted. See 
also Sec. 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 shall be installed as 
indicated in PG-71 of the ASME Code except as noted otherwise in this 
paragraph.
    (2) The final setting of boiler safety valves shall be checked and 
adjusted under steam pressure and, if possible, while the boiler is on 
the line and the steam is at operating temperatures, in the presence of 
and to the satisfaction of a marine inspector who, upon acceptance, 
shall 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 the ASME Code 
shall be run as directly as possible from the body of each boiler safety 
valve, or the drain from each boiler safety valve may be led to an 
independent header common only to boiler safety valve drains. No valves 
of any type shall be installed in the leakoff from drains or drain 
headers and they shall be led to suitable locations to avoid hazard to 
personnel.
    (d)(1) (Modifies PG-72.) The operation of safety valves shall be as 
indicated in PG-72 of the ASME Code except as noted in paragraph (d)(2) 
of this section.

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    (2) (Modifies PG-73.) The lifting device required by PG-73.1.3 of 
the ASME Code shall be fitted with suitable relieving gear so arranged 
that the controls may be operated from the fireroom or engineroom floor.

[CGFR 68-82, 33 FR 18815, Dec. 18, 1968, as amended by CGD 81-79, 50 FR 
9433, Mar. 8, 1985]