Open AccessIgnition risks associated with migratory antistatic liners at the point of use
Author(s) -
C. Newlands,
I. Pavey,
S. Shepherdson,
Wan Azizi
Publication year - 2019
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1322/1/012017
Subject(s) - ignition system , rubbing , antistatic agent , materials science , dissipative system , composite material , electrostatic discharge , forensic engineering , environmental science , nuclear engineering , sheet resistance , mechanics , electrical engineering , engineering , thermodynamics , aerospace engineering , physics , voltage , layer (electronics)
Dissipative plastics are often used to reduce risks of static ignition sources in explosive atmospheres. Migratory agents which diffuse to the surface can aid dissipation. The agent attracts ambient moisture to the surface thus decreasing the electrical resistance. In tests it has been found that surface resistance of migratory liners can take around 24 hours to become dissipative. This brings into question whether conditioning periods recommended for surface resistance tests could be masking the ignition risk of materials. Surface resistance, transferred charge and gas probe ignition tests have been carried out to investigate the ignition likelihood further. Rubbing tests indicated that a protective lubricating film formed at around 1 hour that could prevent charge transfer events but subsequent rubbing removed the film leading to charge transfer events. Liner filling tests were set up similar to IEC 61340-4-4. This testing recorded charge transfer events of over 60 nC for all liners even after 24 hours exposure. Liner filling tests with the gas ignition probe produced ignitions with standard insulating liners (no migratory agent) but produced no ignitions or measurable charge transfers for migratory liners. A question remains over the use of charge transfer values to evaluate ignition risks for migratory static dissipative materials and more guidance is sought to help industry manage these risks.