Sealing Glands
In order to pass temperature, analytical or other types of instrument probes or conductors from ambient conditions through a pressure barrier and into a process environment it is necessary to effect and maintain a credible seal.
This operation can be performed on straight forward single probes by the use of a simple compression type of fitting. However the olive or ferrule which produces the seal frequently becomes a permanent part of the probe and on occasions can damage the probe wall.
In many applications this is an undesirable consequence when attempting to remove the probe for calibration or replacement and it is not possible to use this method when the need arises to pass multiple probes or conductors.
The solution to this is the sealed feedthrough manufactured by Conax Technologies, which utilises soft sealant technology. This technique offers many advantages over previous methods, including the ability to pass multiple probes or conductors.
Sealed against pressures of up to 700 bar.
Sealed against vacuums down to 6.67 x 10-6mbar.
Can be used within a temperature range of -240ºC to +870 ºC.
Sealants are reusable (except Lava).
Soft sealants allow adjustment of probe location.
Can offer electrical isolation between the probe and feedthrough body.
Can be supplied with the option of a range of process connection types.
All the bodies of the feedthroughs are in 316L stainless steel with the soft sealants being supplied in a selection of materials to suit the process parameters. These consist of Neoprene, Teflon®, Viton®, Lava (magnesium silicate) and Grafoil®.
Sealant Types
Neoprene (polychoroprene)
Having the resilience of natural rubber, but with an enhanced resistance to oil. petroleum, ozone, weather and heat. Excellent physical ‘memory´ for temperature cycling applications, moderate electrical resistivity and is reusable.
Temperature range -40 to +93 ºC
Teflon® (tetrafluoroethylene)
The natural lubricity of this material is well documented, it also resists the adhesion of foreign matter and is reusable.
Temperature range -185 to +240 ºC
Viton® (Fluoroelastomer)
This material will retain its mechanical properties at high temperatures, it is resistant to oils, solvents, fuels and corrosive industrial chemicals and is reusable.
Temperature range -20 to +240 ºC
Lava (magnesium silicate)
A low thermal co-efficient, good electrical resistivity and a wide operating temperature range. Tends to be porous to light and wet gases and is not recommended for use with steam or for vacuum applications. Since this material disintegrates into powder form to effect the seal when under compression it is not reusable.
Temperature range -185 to +870ºC.
Grafoil® (99.5% graphite within aluminium foil layers)
Has low vapour pressure and gas permeability and is excellent for vacuum applications. It has a natural lubricity, but is electrically conductive. Due to its construction it is generally not reusable.
Temperature range -240 to +495ºC, but up to +1,650ºC in a reducing/inert atmosphere.
Click on these links for:
MHC and MHM multiple hole glands.
Teflon® is a registered trade mark of EI Du Pont de Nemours.
Viton® is a registered trade mark of DuPont Dow Elastomers LLC.
Grafoil® is a registered trade mark of the UCAR Carbon Company.
