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Cryogenics

Because of its unique properties, perlite insulation has found wide acceptance in the insulating of cryogenic and low temperature storage tanks, in shipping containers, cold boxes, test chambers and in food processing. Storage temperatures of -150oF (-100oC) and below are considered cryogenic. Storage temperatures of 150oF (-100oC) and above to + 40oF (+ 4oC) are considered low temperature. Super cold or extremely cold cryogenic fluids such as hydrogen and helium are normally stored in spherical, double walled vessels with evacuated annular spaces using evacuated perlite

 

Properties of Perlite Insulation

Perlite insulation suitable for non-evacuated cryogenic or low temperature use exhibits low thermal conductivity throughout a range of densities. However, the normal recommended density range is 3 to 4.5 lb/ft3 (48 to 72 kg/m3). In addition to its excellent thermal properties, Perlite insulation is relatively low in cost, easy to handle and install, non-combustible and so meets fire regulations, lowers insurance rates and does not shrink, swell or slump. Because it is inorganic material it is rot and vermin-proof. As a result of its closed cell structure, the material does not retain moisture. 

Typical Non-Evacuated Installation

There are many different design concepts for low temperature and cryogenic storage vessels. However, most have a double wall construction with the annulus filled with expanded perlite. Packaged or bulk perlite may be used to insulate smaller vessels by pouring or blowing it into place. Portable perlite expansion plants are usually used to insulate storage tanks,cold boxes, ships and other double wall vessels and pipes. In these applications perlite ore is expanded on-site and the expanded perlite insulation is conveyed pneumatically into the annulus.

Specificiations

 

Density 
3 to 6 lb/ft3 (48 to 96 kg/m3)
 
 
Sieve Analysis (U.S. Standard mesh)
Percent weight retained
Max. 10% + 16 mesh
(1.18mm)
Min. 50% + 100 mesh
(0.15mm)
 
Thermal Conductivity*
Low temperature applications
Mean temp. -40oF (-40oC)
Non-evacuated cryogenic applications
Mean temp. -195oF (-126oC)
0.24-0.27 Btu.in/h/ft2 deg.F
(0.035-0.039 w/m.K)
0.17-0.20 Btu.in/h/ft2 deg.F
(0.025-0.029 w/m.K)

*Thermal conductivity varies with temperature, density, pressure and conductivity of gas which fills the annulus or insulation pipes.

   

 

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