Cryogenic Perlite

Cryogenic Perlite

"Super" Insinuating Perlite For Evacuated Cryogenic Service

Expanded
cryogenic perlite is used for a wide variety of insulating applications
ranging from cryogenic vessels requiring 'super' insulation to low
temperature and high temperature applications, lightweight perlite
insulating concrete, insulating board, insulating plasters, masonry
wall insulation and underfloor insulation.
Cryogenic Perlite 'Super' Insulation

For
cryogenic applications of -150F (-101C) and below requiring "super"
insulation, evacuated perlite provides a superior insulation with
thermal conductivity up to 40 times less than 0.200 Btu-in/h-ft3oF
(0.029 W/m-K) depending on vacuum and temperature. Usual applications
for evacuated perlite insulation are in double walled helium and
hydrogen storage spheres. It may also be used for storage of oxygen,
nitrogen and LNG when especially low thermal conductivities are
desired. In addition to large field erected storage tanks, evacuated
perlite is used to insulate smaller shop fabricated vessels designed
for the storage of many of the cryogenic gases.

Properties of Cryogenic Perlite Insulation

Perlite
insulation suitable for evacuated cryogenic service exhibits low
thermal conductivity throughout a range of temperatures, pressures and
densities. The normal recommended density range is 8 to 9-1/2 lb/ft3
(128 to 152 kg/m3). The accompanying graph provides data on thermal
conductivity for expanded perlite with a density of 8.7 lb/ft3 (139
kg/m3) at mean temperatures from 0F (-18C) to -160F (-107C).
Cryogenic temperatures are generally considered to be below -150F
(-101C). Thermal conductivity of evacuated perlite is many times lower
than that of nonevacuated perlite insulation. For example, at a mean
temperature of -115F (-82C), normal unevacuated cryogenic perlite at
4 lb/ft3 (64 kg/m3) would have a thermal conductivity about 22 times as
peat as evacuated perlite at 8.7 lb/ft3 (139 kg/m ) and interstitial
pressure of 10 microns.

Density 8 to 9 lb/ft3 (128 to 152 kg/m3) Sieve Analysis (U.S. Standard) Maximum 5% +30 mesh (0.6 mm)* Thermal Conductivity 0.0047 Btu-in/h-ft2- F' (0.0007 W/m-K)+
Tests have shown that the finer the material the better its performance (Within the specified density range). Thermal conductivity depends on temperature, density and sieve analysis of expanded perlite and the interstitial pressure.+ At -160F (-107C), 8.7 lb/ft3 (139 kg/m3), 0.01. (1.33 mPa)