Coatings firm probes solvent vapour measuring device

Congleton, UK - Raleigh Coatings has trialled a new type of solvent vapour probe at its Staffordshire operation, which provides contract coating services to industry markets including medical devices, aerospace, security and electronics.

The Extronics' iLEL100 device is designed for the continuous in situ measurement of flammability (lower explosive limit, %LEL) of solvent vapours driven off in ovens and dryers. Such measurements have previously required the use of complex sample extraction systems demanding high levels of maintenance.

The clean room coating and laminating equipment at the Raleigh Coatings site can handle 100% solids, water-based and solvent-based chemistry applied with precision to films, foils and papers. R&D clean room pilot coating and laminating facilities are also available.

Raleigh Coatings plant manager Paul Hewitt agreed to allow Extronics to install the iLEL100 solvent probe and initiate the performance trials to put the probe through its paces. The first location in which the probe was located was in the main oven exhaust.

The internal temperature of the exhaust duct was about 60°C and the vapour velocity between 4-10m/sec. The duct provided a low temperature point of measurement, which was of interest as it presented the possibility of particulate deposition within the probe that could be detrimental to its long-term operation. However, no deposition was observed.

The probe was trialled in this location for six months before being moved to the more arduous location by being directly inserted into the oven. The internal conditions within the oven at this point of measurement were of a more turbulent nature in terms of the gas streams as the probe was no longer located in a straight run pipe, hence the velocity across the probe was varying and secondly the temperature was much higher at 120°C plus.

The design of the oven was such that it would open up to allow access to the internals for maintenance and service work, it was noticed during one such interval that the internals of the oven were coated with a brown sticky substance.
This particular point of the oven was the chosen location of installation as it also provided an opportunity for comparative measurements to be made as another semi-extractive monitor was located near the selected point of entry.

Across the two-year trial, the measured values of the %LEL of the probe and the reference device were downloaded to a data logger for analysis and comparison. A detailed analysis of the results revealed that the two devices paralleled each other in performance with respect to the measured values of the %LEL.

After the conclusion of the trials the iLEL100 probed was reinstalled on the feed to the oxidiser where it has been operating for the last three years, providing continuous maintenance-free operation.