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Asme BPVC Code Cases 1998 Edition CCASE11993 06-15-98 12:58:08

CASE

1993-5

CASES OF ASME BOILER AND PRESSURE VESSEL CODE

Approval Date: December 23, 1996

See Numeric Index for expiration

and any reaffirmation dates.

Case 1993-5

Precipitation-Hardening Nickel Alloy (UNSN07718) Used as Bolting Material

Section I and Section VIII, Division 1

Inquiry: May precipitation-hardened nickel alloy rod,

bar, forgings, and forging stock (UNS N07718) con-

forming to SB-637 be used as a bolting material for

Section I and Section VIII, Division 1 construction?

Reply: It is the opinion of the Committee that the

material described in the Inquiry may be used as a

bolting material in Section I and Section VIII, Division

1, construction at a design temperature of 1150F or

less, provided the following additional requirementsare met.

(a) The maximum allowable stress values shall be

those listed in Table 1.

(b) The rules of Part UNF shall apply for Section

VIII, Division 1 construction.

(c) Except for nonstructural tack welds used as a

locking device, no welding is permitted.

(d) This Case number shall be shown on the Manufac-

turers Data Report.

CAUTIONARY NOTE: Austenitic alloys are subject to stress corro-

sion cracking, intergranular attack, pitting, and crevice corrosionwhen used in boiler applications in aqueous environments. Factors

This is Electrontic File Page # 83

that affect the susceptibility of these materials are applied or residualstress, water chemistry and deposition of solids, and material condi-

tion. Susceptibility to attack is enhanced when the material is usedin the sensitized condition, or with residual cold work. Concentrationof corrosive agents (e.g., chlorides, caustic or reduced sulfur species)can occur under deposits formed on the surface of these materials,and can result in severe underdeposit wastage or cracking. Forsuccessful operation in water environments, careful attention mustbe paid to continuous control of water chemistry.

TABLE 1

MAXIMUM ALLOWABLE

STRESSES, ksi

For Metal Temperature Allowable Stress Values,

Not Exceeding, F max., ksi

100 37.0

200 36.0

300 35.2

400 34.6

500 34.2

600 33.8

700 33.6

750 33.5

800 33.3

850 33.1

900 32.9

950 32.6

1000 32.3

1050 32.0

1100 30.7

1150 29.5

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