Page 42 - Pressure Vessel Design Manual

28 Pressure Vessel Design Manual

STIFFENING RING CHECK FOR EXTERNAL PRESSURE
I Moment of inerlia wlo shell

Moment of inertia w/ shell
As If B > 2,500 psi,
determine A from D2LO + AS/W
E = modulus of applicable material 1: = 10.9
elasticity
charts
From Ref. 1, Section UG-29.

PROCEDURE 2-3

CALCULATE MAP. MAWP. AND TEST PRESSURES

Notation E =joint efficiency, see Procedure 2-1
and Appendix C
Sa = allowable stress at ambient temperature, psi
SDT = allowable stress at design temperature, psi
SCA = allowable stress of clad material at ambient tempera- Definitions
ture, psi
Maximum Allowable Working Pressure (MAWP): The
SCD = allowable stress of clad material at design tempera- MAWP for a vessel is the maximum permissible pressure at
ture, psi
SBA = allowable stress of base material at ambient tempera- the top of the vessel in its normal operating position at a
specific temperature, usually the design temperature.
ture, psi
SBD = allowable stress of base material at design tempera- When calculated, the MAWP should be stamped on the
nameplate. The MAWP is the maximum pressure allowable
ture, psi
C.a. = corrosion allowance, in. in the “hot and corroded’ condtion. It is the least of the
values calculated for the MAWP of any of the essential parts
t,, =thickness of shell, corroded, in.
t,, =thickness of shell, new, in. of the vessel, and adjusted for any difference in static head
thc =thickness of head, corroded, in. that may exist between the part considered and the top of
thn =thickness of head, new, in. the vessel. This pressure is based on calculations for every
tb =thickness of base portion of clad material, in. element of the vessel using nominal thicknesses exclusive of
t, =thickness of cladding, in, corrosion allowance. It is the basis for establishing the set
R, =inside radius, new, in. pressures of any pressure-relieving devices protecting the
R, = inside radius, corroded, in. vessel. The design pressure may be substituted if the
R, = outside radius, in. MAWP is not calculated.
D, =inside diameter, new, in. The MAWP for any vessel part is the maximum internal or
D, =inside diameter, corroded, in. external pressure, including any static head, together with
D, =outside diameter, in. the effect of any combination of loadings listed in UG-22
PM = MAP, psi which are likely to occur, exclusive of corrosion allowance
PW = MAWP, psi at the designated coincident operating temperature. The
P = design pressure, psi MAWP for the vessel will be governed by the MAWP of
Ps = shop hydro pressure (new and cold), psi the weakest part.
PF = field hydro pressure The MAWP may be determined for more than one de-
(hot and corroded), psi signated operating temperature. The applicable allowable