The Sun: Man's Friend & Foe

Engineers have to deal with the Sun and Sun related problems every day. Civil engineers must take into account solar heat gain when designing and building roads. Electrical engineers have to compensate for the Sun's interference in their calculations for communication systems, while welding engineers are effected by the potentially deteriorating effects of the Sun on materials they use. Almost every branch of the engineering field is effected in one way or another by the Sun.

To illustrate this fact here are some excerpts from a welding manual on plastic-lined piping products to show one way welding engineers are effected:

Solar effects
How can the Sun effect the piping system? Can the surface of the pipe withstand direct sunlight? Does the material degrade when exposed to ultraviolet radiation? Solar radiation not only degrades many solid plastic systems, but can raise the exterior shell temperature of the pipe to temperatures in excess of 140 degrees Farenheit.
- Engineering Manual
DOW Plastic-Lined Piping Products
[Welder]

Chevron's subsidiary Plexco, Inc. published a paper on Chemical and Environmental Considerations, in it they said the following:

Sunlight and Thermal Effects

For Pressure
Rating At Multiply 73 Degrees
Rating By

    40 Degrees 1.20

    60 Degrees 1.08

    73 Degrees 1.00

  100 Degrees 0.78

  120 Degrees 0.63

  140 Degrees 0.50

To protect the piping material from ultraviolet radiation, most polyethylene pipe formulations include carbon black or some other ultraviolet screening substance.
PLEXCO PE 3408 pipe can be used over a wide temperature range. With a brittleness temperature (ASTM D-746) of -180 degrees Farenheit it performs very well at subambient temperatures. In pressurized systems, it can be used up to 140 degrees Farenheit; and up to 180 degrees Farenheit for non-pressure applications. However, elevated temperatures reduce the effective operating pressure of polyethylene piping systems. To determine the pressure rating for pipe at a temperature above ambient, multiply the 73 degree rating by the following factors on the chart.
Temperature fluctuations experienced in surface installations need to be taken into consideration when designing a piping system. Polyethylene's high thermal expansion coefficient of 9 X 10 to the -5 in/in/degrees Farenheit may lead to lateral movement of the pipeline. The results of this movement can be compensated for by snaking the pipeline or installing expansion loops.

Weatherability
Two principal factors influence the weathering of plastic pipe in outside above ground applications... temperature changes caused by seasonal variations and solar heating and solar radiation of ultraviolet rays...