Polystyrene

Polystyrene thermal insulation is rigid, cellular foam
insulation. It is commonly classified as either Expanded Polystyrene Foam (EPS)
or Extruded Polystyrene Foam (XPS). XPS is a closed-cell material manufactured
as rectangular billets, typically 20 in wide x 9 ft long x 10 in tall. Prior to
actual installation, billets are fabricated into various shapes including
preformed pipe half-shells 3 ft long designed to fit NPS pipe and tubing.
Complex shapes can also be fabricated to fit valves, fittings, and other
equipment. ASTM material specification C 578 covers several types of
polystyrene insulation, but Type XIII is usually specified for mechanical
applications and covers service temperatures from -297°F to +165°F. The
standard contains requirements for compressive resistance, flexural strength,
thermal conductivity, water absorption, water vapor permeability, and
dimensional stability. For comparison purposes, the thermal conductivity of the
Type XIII XPS is a maximum of 0.259 Btu-in/hr-ft²-°F at 75°F.

Key
applications for XPS insulation are on pipe, equipment, tanks, and ducts
operating at temperatures below ambient. These include food and beverage lines,
and refrigeration lines.

Figure 1