STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Derricks and Portable Masts 515
to the ground motion prescribed for the design of the offshore platform. The
allowable stresses for the combination of earthquake, gravity and operational
loading should be limited to those basic allowables with the one-third increase
as specified in AISC Part I. The computed stresses should include the primary
and the secondary stress components.
Extreme Temperature
Because of the effect of low temperatures on structural steel, it will be no
use to change (decrease) the allowable unit stresses mentioned in the preceding
paragraphs titled “Allowable Stresses.” Low temperature phenomena in steel
are well established in principle. Structures to be used under extreme conditions
should use special materials that have been, and are being, developed for
this application.
Miscellaneous
Structural Steels. Structures shall conform to sections of the AISC “Specifications
for the Design, Fabrication and Erection of Structural Steel Buildings.”
Castings. All castings shall be thoroughly cleaned, and all cored holes shall be
drifted to ensure free passage of proper size bolt.
Protection. Forged parts, rolled structural steel shapes and plates, and castings
shall be cleaned, primed, and painted with a good commercial paint or other
specified coating before shipment. Machined surfaces shall be protected with a
suitable lubricant or compound.
Socketing. Socketing of raising, erecting, or telescoping mast wire ropes shall
be performed in accordance with practices outlined by API RP 9B.
Recommended Practice for Maintenance and
Use of Drilling and Well Servicing Structures
These general recommendations, if followed, should result in longer satisfactory
service from the equipment. These recommendations should in every
case be considered as supplemental to, and not as a substitute for, the manufacturer’s
instructions.
The safe operation of the drilling and well servicing structure and the success
of the drilling operation depend on whether the foundation is adequate for the
load imposed. The design load for foundation should be the sum of the weight
of the drilling or well servicing structure, the weight of the machinery and
equipment on it, the maximum hook load of the structure, and the maximum
setback load.
Consultation with the manufacturer for approval of materials and methods
is required before proceeding with repairs. Any bent or otherwise damaged
member should be repaired or replaced. Any damaged compression member
should be replaced rather than repaired by straightening. Drilling and well
servicing structures use high-strength steels that require specific welding electrodes
and welding techniques.
Fixtures and accessories are preferably attached to a structure by suitable
clamps. Do not drill or burn holes in any members or perform any welding
without obtaining approval of the manufacturer.