LADDERS AND PLATFORMS

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LADDERS AND PLATFORMS
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Ladders and platforms on vertical fractionating
towers are layed out by the piping designer as
the nozzles are oriented.
PLATFORMS Platforms are provided at each
manhole located 2-6 below the manhole
centerline. Other platforms are located as needed
for access to critical instruments or operating
valves. However, the ultimate rules as to
location and need of platforms are provided by
your employer. Platforms for towers should be
3-0 wide plus 6 clearance from the vessel OD.
The flooring of a platform is typically ¼
thick plate or ¼- 3/8 grating. On pages 184
185 of your text you will find a layout of the
platforms necessary for V-101.
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LADDERS Ladders are made of steel bar and plate
and are welded /or bolted to the exterior of a
vessel. Ladders should be caged if they are over
20-0 above grade. A cage is designed to
enclose a ladder and prevent a worker from
falling away from the ladder if he looses his
grip. The maximum continuous ladder run should
be 30-0 This means that the ladder should be
offset every 30-0 with an offset platform at
these points.
Ladder rungs are 3/4 in diameter and spaced
1-0 apart with the centerline of the rungs
spaced typically spaced 1-0 off the vessel. For
our drawings, we will use 9 between the outside
of the vessel to the centerline of the ladder
rung as shown in illustrations on pages 184-185
of your textbook. 5/8 diameter bolts are used in
fabrication of the ladder. The bolt hole
diameter is typically 1/16 larger than the bolt
diameter.
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The adjacent illustration shows V-101 (the
smaller white circle) and the initial layout for
Platform 1 (green circles). The red lines show
the centerline of the ladder and the edge of the
platform. For the precise angles that these lines
are drawn, see page 184 in your text. The inner
circle of the platform is 6 off the OD of the
vessel.
Ladder
3-0 Wide
To layout the platform circles The vessel is
4-0 diameter, there is a 6 space between the
platform and the vessel and the platform is 3-0
wide.
Edge
Radius of the inner circle 4-0/2 6 2-6
Radius of the outer circle 4-0/2 6 3-0
5-6
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Trim the platform circles to the ladder and edge
lines. Change the ladder line to a centerline
for work on the ladder in the next few steps.
Extend the centerline of the ladder to the vessel
OD.
Draw a line perpendicular to the ladder
centerline and tangent to V-101 (shown in RED).
Use this line and the dimensions provided on pg.
184 to offset the lines for ladder rung
centerline, the tangent point for the ladder cage
and the centerline for the ladder cage.
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Now you need to draw the circle that represents
the ladder cage using the 1-1 radius.
NOTE Centerline of ladder rung to center of
cage 1-1
Trim the cage circle and draw two lines parallel
to the ladder centerline that are tangent to the
cage.
Centerline of Rung
The line on the platform side of the ladder
represents the edge of the platform.
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The dimension 1-9 indicates where the ladder
cage will connect to the platform. Remember,
your job is to provide an accurate representation
of the ladder and platform. Drafters in your
companys Civil department will provide detail
drawings for the connections between the ladders,
platforms and vessels.
Rung Centerline
Platform Edge
Trim the cage and make the connection to the
platform.
Typical Platform Cage
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Rung Centerline
V-101
Platform
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The width of the ladder rung is 1-4. The
distance from the OD of V-101 to the center of
the ladder clip bolt-holes is 5.
Centerline bolt-holes
Use the lines that you have drawn from previous
steps to aid in the alignment and offset of lines
that you need to set up the ladder detail.
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9
Typically, the flat bar will extend at least 1
past the centerline of the bolt hole.
The ladder sidebars are 2 ½ wide x 3/8 thick
As a pipe designer, your job is to provide an
accurate depiction in your drawing. You will be
able to obtain exact details of the ladder
connections from your Civil department or
fabricator. For our coursework this amount of
detail will be acceptable.
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The ladder clips that are attached to the vessel
itself are welded in place by the vessel
fabricator. Their location is determined by the
piping designer on the initial vendor drawings
before the vessel is fabricated.
Depending on your company vendors or fabricators,
the radial ladder connection (R 2 5/16) may be
circumvented by the use of flat bar or channel
instead.
The ladder side bars (what the rungs are welded
between) are typically sized according to the
maximum unsupported length Use 2 ½x 3/8 flat
bar to 10-0 clip spacing Use 3 x 3/8 flat bar
to 20-0 clip spacing.
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Typical Cage Detail
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• When laying out the section view of a ladder
  platform
• The centerline of the topmost rung of the ladder
  should be approximately 1-0 above the handrail.
  This provides a safe exit from the ladder to the
  platform.

Top of Grating

• The top of the handrail is typically 4 ½ above
  the ladder clip.
• The toe-plate around the perimeter of the
  platform is typically 6 high on the outer edges
  and 4 high on the side of the platform nearest
  the vessel.
• The thickness of the grating or plate cover on
  the platform is ¼.

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Ladder Setup at Platform Elevation
The top-most hoop of the ladder cage is located
2 below the handrail. It is open to the
platform side as shown in an earlier slide.
Ladder hoops are spaced 4-0 to 5-0 apart.
With the lowest hoop being located between 7-0
to 8-0 above HP of grade.
The ladder support clips are approximately spaced
at 10-0 intervals with the first clip being
located at approximately 3-6 MAX above H.P. of
grade.
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Ladder Setup at Grade
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Thanks for viewing the tutorial and hope you have
found it beneficial.
QUESTIONS, COMMENTS or COMPLAINTS can be sent to
me via email or bring them up in the next class
meeting.