Page 294 - Ship Construction.DJ Eyres 6Ed

Ch24-H8070.fm Page 283 Wednesday, October 18, 2006 7:00 AM
Lifting Arrangements 283
Swivel for derrick head
span block
Eye plate welded thro’
derrick
Span load
Span pull Resultant load on span block
Welded lugs for
--- ใช้เพื่อการศึกษาเท่านั้น---
slewing guys
Mast
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี

Pull in lead purchase
Cargo
Shrunk and welded
tubular sections Resultant on cargo head block

Derrick boom Boom thrust Safe working load S.W.L.

ึ S.W.L. + Cargo purchase + Half boom

Span load

Pull in lead heel block
Resultant load on

Pull to winch

Gooseneck seat
welded thro’ mast

FIGURE 24.4 Forces in single swinging derrick rig
at an angle of 45° to the horizontal. The loads on all the blocks except the
lower block of a cargo purchase will be the resultant of the two forces to
which the block is subjected. A single sheave block has a safe working load
which is half the resultant, and multi-sheave blocks have a safe working
load which is the same as the resultant.