10 January 2002
3-4. SYSTEM LAYOUT PLAN/PROFILE. All distribution systems require a layout plan and profile be
provided by the designer.
a. Layout plans will include, but not be limited to:
(1) system routing (including expansion loops and bends, manhole locations and anchor
the distribution system).
(3) all utilities within 25 feet of the system.
(4) all roads and buildings clearly labeled.
(5) types of surface conditions (asphalt, concrete, seeding, gravel, etc.).
(6) grade contour lines (new and existing).
(7) all dimensions and clearances to ensure accurate routing.
b. A profile of the system will also be drawn and, as a minimum, show:
(2) system slope drawn to scale (1-inch to 20 feet minimum for all systems) to all low points.
(3) new and existing grade.
(4) all existing or new utilities shown at their actual burial depths.
3-5. EXPANSION COMPENSATION. All expansion systems, loops, and bends, will be sized in order to
prevent excessive pipe stresses (due mainly from thermal expansion) from exceeding those allowed by the
Power Piping Code, ASME B31.1. Mechanical expansion joints are not recommended for absorbing system
expansion. Mechanical expansion joints greatly increase the maintenance requirements of the distribution
systems. In the unlikely event that expansion joints must be used, they must be placed in an adequately
sized valve manhole. The designer is responsible for expansion calculations for Heat Distribution Systems in
Concrete Trenches, Prefabricated Underground Heating/Cooling Distribution Systems, and Aboveground
Heat Distribution Systems. The designer is also responsible for the expansion and stress determinations in
all the valve manholes, including the location of the equipment/pipe support locations. Even though the
manufacturer is responsible for the expansion calculations for Pre-Engineered Underground Heat Distribution
Systems, the calculations will be thoroughly reviewed by the designer at the shop drawing review. It is
recommended that a three dimensional finite element computer program be used for determining system
stresses. Many finite element software packages are available which operate on desktop computers. The
temperature differential used in the stress analysis will be the maximum temperature of the media less the
minimum temperature the system will encounter during a shutdown. All loops and bends will be sized based
on zero percent cold springing. Cold springing effects lessen over time and are difficult to maint ain in the
event the system is ever cut, and shall therefore not be included in the analysis. However, loops may be
installed with cold springing as an added conservative measure.
3-6. VALVE MANHOLES. For all distribution systems, valve manholes will be designed by the
project designer. A valve manhole is required for all buried system lateral connections, all below