| Tweet |
Custom Search
|
|
|
||
 TB 55-1900-201-45/1
b. The safety valve and/or relief valve equipment shall be inspected and tested as frequently as necessary and
at least biannually.
c. The minimum thickness and maximum corrosion rate for any part of the vessel should be determined at
each inspection.
(1) The depth of corrosion in vessels subjected to corrosive service may best be determined by gaging from
protected surfaces within the vessels, when such defects may be available.
(2) For a considerable corroded area, the average of the least thickness within that area may be considered
as the thickness of the metal therein. This thickness may be used as a basis for computing the allowable working pres-
sure and for determining corrosion rates at that location.
(3) Isolated pits may be ignored provided that their depth is not more than one-half of the thickness of the
vessel wall, and the total area of the pits does not exceed seven square inches, within any eight inch diameter circle.
d. Inspection for defects. The parts of a pressure vessel which should be most carefully inspected depend upon
the type of vessel and the operating conditions to which it is subjected. The surveyor shall be familiar with the operating
conditions of the vessel and with the causes of defects and deterioration that may result therefrom.
(1) All surfaces of shell plates shall be carefully examined for cracks, laminations and other defects.
(2) The inner and outer surfaces of all welded joints shall be carefully inspected for possible cracks.
(3) All attachments shall be examined for distortion and for corrosion. Threaded connections shall be ex-
amined for condition, and if they seem defective, the threaded nipples shall be removed to permit an inspection on the
number of threads that are effective.
e. Safety valves and relief valves and other protective devices shall be inspected to see that they are in proper
condition. Inspection of valves will normally include a check on the required operation at the set pressure.
f. The allowable working pressure for a vessel in operation can be computed from the appropriate formula,
found in Section 8, Unfired Pressure Vessels, ASME Manual, using dimensions actually determined by inspection for the
thickness.
g. Hydrostatic test. Vessels subjected to internal pressures shall be hydrostatic tested to current USCG stan-
dard for pressure at the test temperature (60 , 140 ).
F
C
h. The following pressure vessels will not normally be subjected to a hydrostatic test.
2-29
|
||
|
||
