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Some standard commercial mobile cranes manufactured before 28 February 1992,
however, are not equipped with A2Bs.  Those of later manufacture are equipped with
There are three commercial A2Bs available on mobile cranes those that
give a warning of impending two-blocking, those that prevent damage from two-
blocking, and those that preclude two-blocking.  The Recommended Practice of SAE
J1350, Two-Block Warning and Limit Systems in Lifting Crane Service, establishes
the minimum performance requirements for these devices.  NCC policy is to require
A2Bs that prevent two-blocking on all mobile cranes. Additional Requirements.  All load bars (tension links) of LIDs and LMIs
used on Navy cranes are required to comply with additional requirements, beyond
those of commercial practice.  Steel tension links must have a minimum design
factor of 5.0, based on its rated capacity and the material ultimate strength, and
a hardness not greater than 40 Rockwell C.  Aluminum tension links must have a
minimum design factor of 7.0, as defined above. Wind Speed Indicating Systems.  Wind speed indicating devices are
required on all cranes in longshoring service, with the speed of the wind
displayed in the operator's cab.  NCC also requires that the direction of the wind
be displayed.  A transmitter is mounted on a portion of the crane's upperworks in
a location free from obstructions to the flow of the wind.  It is directly
connected to a display unit in the operator's cab.  The display unit is also
programmed to give the operator a visible or audible warning of high wind
conditions.  The transmitter is to be fitted with a heater to eliminate freezing.
Painting and Corrosion Protection.  Electrical equipment is usually
painted by its manufacturer and field painting is not required.  Steel panel
enclosures received in unpainted condition are to be painted in accordance with
paragraph 4.1.29.  Enclosures fabricated from stainless steel are not to be
painted.  Other than aluminum which has not been anodized, nonferrous metals are
also not to be painted.  Motors used in outdoor applications are to be factory
painted to their manufacturer's standard for "wash-down" service.  Prior to
painting galvanized rigid steel conduit, it must be sprayed with a zinc-phosphate
primer.  Gaskets of enclosures and fixtures, and joints and contact surfaces of
explosion-proof and dust-ignition-proof enclosures must be kept free of any paint.


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