[Code of Federal Regulations]
[Title 46, Volume 2]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 46CFR54.15-10]

[Page 157-158]
 
                           TITLE 46--SHIPPING
 
   CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)
 
PART 54_PRESSURE VESSELS--Table of Contents
 
                  Subpart 54.15_Pressure-Relief Devices
 
Sec. 54.15-10  Safety and relief valves (modifies UG-126).

    (a) All safety and relief valves for use on pressure vessels or 
piping systems shall be designed to meet the protection and service 
requirements for which they are intended and shall be set to relieve at 
a pressure which does not exceed the ``maximum allowable working 
pressure'' of the pressure vessel or piping system. Relief valves are 
not required to have huddling chambers for other than steam service. In 
addition, safety valves used on vessels in which steam is generated 
shall meet Sec. 52.01-120 of this subchapter except Sec. 52.01-
120(a)(9). For steam service

[[Page 158]]

below 206 kPa (30 psig), bodies of safety valves may be made of cast 
iron. Safety relief valves used in liquefied compressed gas service 
shall meet subpart 162.017 or 162.018 in subchapter Q (Specifications) 
of this chapter as appropriate.
    (b) Pilot-valve control or other indirect operation of safety valves 
is not permitted unless the design is such that the main unloading valve 
will open automatically at not over the set pressure and will discharge 
its full rated capacity if some essential part of the pilot or auxiliary 
device should fail. All other safety and relief valves shall be of the 
direct spring loaded type.
    (c) Safety and relief valves for steam or air service shall be 
provided with a substantial lifting device so that the disk can be 
lifted from its seat when the pressure in the vessel is 75 percent of 
that at which the valve is set to blow.
    (d) Safety and relief valves for service other than steam and air 
need not be provided with a lifting device although a lifting device is 
desirable if the vapors are such that their release will not create a 
hazard.
    (e) If the design of a safety or relief valve is such that liquid 
can collect on the discharge side of the disk, the valve shall be 
equipped with a drain at the lowest point where liquid can collect (for 
installation, see UG-134 of section VIII of the ASME Code).
    (f) Cast iron may be employed in the construction of relief valves 
for pressures not exceeding 125 pounds per square inch and temperatures 
not exceeding 450 [deg]F. Seats or disks of cast iron are prohibited.
    (g) The spring in a relief valve in service for pressures up to and 
including 250 pounds per square inch shall not be reset for any pressure 
more than 10 percent above or 10 percent below that for which the relief 
valve is marked. For higher pressures, the spring shall not be reset for 
any pressure more than 5 percent above or 5 percent below that for which 
the relief valve is marked.
    (h) The rated relieving capacity of safety and relief valves for use 
on pressure vessels shall be based on actual flow test data and the 
capacity shall be certified by the manufacturer in accordance with one 
of the following:
    (1) 120 percent of the valve set pressure for valves rated in 
accordance with Compressed Gas Association Standard S-1.2.5.2.
    (2) 110 percent of the valve set pressure for valves rated in 
accordance with UG-131 of section VIII of the ASME Code.
    (3) 103 percent of the valve set pressure for steam in accordance 
with PG-69 of the ASME Code.

[CGFR 68-82, 33 FR 18828, Dec. 18, 1968, as amended by CGD 81-79, 50 FR 
9436, Mar. 8, 1985]