Starting version 5.01B, beams can be rendered by specifying
the depth and width of the beam section. So too can hinge joints with
axis specified.
In the figure below, notice the two beams, one with a beta angle of 90
deg. and how it is shown differently from the beam which has no angle
specified. The beta angle is used to define the orientation of the beam
local axes. Observe the local axes for the beam (that applies to the beam
with a beta angle of 90 deg.).
The local coordinate system for the beam can be shown on graphics in single
line mode (select List>Beams, List Window>View menu>Show LCS).
In laying out hot piping, one should consider the
following:
1. The expansion of turbines, towers, heat exchangers, etc., must be added
to the pipe expansion.
2. A heat exchanger is generally fixed at one end, and free to slide at
the other.
3. Long radius elbows are more flexible than five diameter bends. The
elbows produce lower forces but higher local stresses because of the flattening
of a curved member when it flexes. The five diameter bend flattens less
and therefore produces higher forces but lower local stresses. These local
stresses are in the bend or elbow itself.
4. Pumps, turbines and compressors must have low forces on them as required
by the manufacturer and in compliance with API/NEMA. If the stress in
the piping adjacent to the equipment is limited to 5000 psi, the forces
will generally be acceptable.
5. Dead weight of piping must in most cases be carried by independent
supports and not by the pump, turbine or compressor. In the case of heat
exchangers and vessels and other non-rotating equipment, some of the piping
dead weight loads may be transferred to the nozzles but the designer must
check with the equipment designer first.
6. Always run a line with the thought as to how it will be supported.
Lines should be grouped whenever possible. If a line needs to be rerouted
for better support, this should be done.
7. Cold spring is not the answer to lowering stresses in overstressed
piping. Piping codes do not permit this. They allow only a one-third reduction
in forces and bending moments if the line is cut short by 50% of its total
expansion.
The above tips are excerpted from SST 101: Piping
Design and Analysis Seminar Notes.
This tip will give you a guideline for locating the supports
in your piping system.
• Locate dead weight supports using recommended spacing from the
code (B31 etc.).
• Consider existing support points.
• Decrease span by half off equipment.
• Decrease span for concentrated loads.
• Support concentrated loads.
• Support offset loads.
• Decrease span for extra lagging or insulation.
• Locate supports at changes in direction (no overhung corners, top
or bottom of risers).
• Select type (rigid, spring, or constant support) based on thermal
expansion analysis.
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