Quantcast Accessibility and Maintainability Features

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MIL-HDBK-1038
It is recommended that the test weights be of all-steel or ductile cast
iron construction.  The design criteria limit the maximum stresses to 100 percent
of the AISC allowable value or 35 percent of the cast iron yield strength.
5.1.4.3
Structural Assembly Standards.  Common acceptance criteria for structural
steel are established by ASTM A6, General Requirements for Rolled Structural Steel
Bars, Plates, Shapes, and Sheet Piling.  This standard addresses the permissible
variations in the dimensional, chemical, and mechanical attributes of commercially
produced structural steel.  This material is acceptable for all structural
components of cranes.
Field assembly and fit-up of large structural components invariably
reveals misalignments at their interfaces that require some form of compensation.
Quality Criteria and Inspection Standards, published by AISC, addresses typical
problems encountered in fabrication and erection of steel structures.  This
publication addresses all problems related to fabrication and assembly of steel
structures and provides commentary together with formal AISC recommendations.  The
scope includes:
a)
Preparation of materials (purchased steel)
b)
Fitting and fastening
c)
Dimensional tolerances
d)
Welding
e)
Surface preparation and painting
f)
Non-destructive examination
g)
Special fabrication problems
NCC policy is to accept/apply the AISC recommendations for new crane
procurements.  Additionally, although this item is not addressed by AISC, on new
cranes NCC policy is to accept filler plates at bolted butt joints, such as those
between boom sections, portal base cap and legs, A-frame members, and other major
structural joints.  The minimum thickness of the filler plates is 1/4 inch, and
only one filler plate is permitted per bolted butt joint.
5.1.4.4
Accessibility and Maintainability Features.  The design of older portal
and floating cranes restricts or complicates access to, or repair of, mechanical
and structural components.  For example, A-frames normally penetrate the machinery
house roof, and are riveted to the machinery deck.  This arrangement makes the
task of A-frame removal a major maintenance operation.  Furthermore, when an A-
frame or another structural member is in close proximity to a hoist gear reducer
cover, the internal components of the gear reducer cannot be readily inspected.
NCC policy for new portal, floating, and container cranes is to require specific
designed-in accessibility and maintainability features.  The layout of the
machinery house requires that the diesel engine-generator set be separated from
the control (electrical) compartment and operator's cab by the hoist machinery
compartment.
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