Model 1813 is a flange-mounted unit incorporating an insertion tube with sintered filter and a blowback housing assembly. Gas sample is extracted by the analyzer system through the sintered filter insertion tube and blowback valve to a heated sample line for transport to the analyzer system. The insertion tube is a concentric double skin arrangement with insulation between the two concentric tubes to prevent sample temperature loss as gas is extracted. The in-situ stainless steel sintered filter prevents large particles being extracted from the duct or flue, thereby eliminating particle blockage of the system.
The blowback oven incorporates a pneumatically actuated heated blowback valve operated by a pilot solenoid valve. An air supply pressure regulator provides regulated, preheated blowback air into the blowback valve. Periodically, the pilot solenoid valve is switched by a signal from the analyzer system to actuate the pneumatic blowback valve. This temporarily stops sampling, allowing a blast of air to back-purge the insertion tube and sintered filter, clearing any accumulated particulate matter. The blowback sequence normally consists of 5 pulses, at 6 second intervals between pulses. The frequency of such blowback will depend on the process conditions and is determined upon commissioning. The control signal for blowback is a 24V DC drive from the analyzer system controller. The oven includes a low temperature thermostat, to provide a system interlock on loss of temperature or power failure.
All wetted parts in the probe are stainless steel (316) except the blowback valve diaphragm assembly which is high temperature VitonŽ. The probe is run at a minimum temperature of 180°C to avoid corrosive condensation.
The insertion tube length can be varied to suit different duct sizes, and the sintered filter length is matched to insertion length. Heat tracing of the insertion tube is available optionally where low temperatures may give a risk of condensation.