Hot Box for outdoor process sampling applications can deliver high temperatures up to 150°C/300°F in compact footprints. The hot boxes employ a combination of conduction and convection heating assisted by a novel air circulation system.
Protective enclosures are usually necessary for analyzer applications and are a major contributor to overall costs. The compact hot boxes make it possible to provide elevated temperature environments for sampling systems in small form factors, This greatly simplifies installations close to the process lines being tested - to minimize sample lag time and substantially reduce the hidden costs of analyzer installations such as heated sample lines.
Intertec's easy-access hot boxes provide an efficient heating solution thanks to the way they are constructed, using high-performance insulation sandwiched between sheets of GRP (glass-fiber reinforced polyester). All of the materials have low thermal conductivity, and the sandwich construction means that enclosures can be fabricated using bonding techniques, avoiding the 'thermal short cuts' between inner and outer shells that metal enclosures and metal fixings create. The overall thermal insulation of a sandwich-construction GRP enclosure is typically more than twice as good as a steel enclosure with the same insulation thickness and provides a highly stable environment for maintaining elevated temperatures. Among many applications, the hot boxes are helping plant operators to implement the monitoring and analysis required to meet new flare stack combustion rules.
The hot boxes use electric heaters that have a flat side for conductive heat transfer, and a finned side for efficient heat transfer to the internal atmosphere using convection. The conductive face of the heater is attached to an aluminum plate. The sampling equipment is assembled onto a second detachable plate, which bolts onto the heated plate with the assistance of thermal transfer paste for optimal heat conductivity. The heaters are designed for hazardous area (potentially explosive) applications and employ positive temperature coefficient or PTC cartridges. As their electric resistance increases with rising temperature, the heaters are self-limiting, ensuring that the surface temperature will never exceed the maximum temperature of the listed temperature class.
