Armstrong International B7131 Pneumatic Temperature Switch

Armstrong B7131 Pneumatic Temperature Switch is a compact, air-pressure–driven sensor used to control Armstrong Series 9000 conditioned-steam humidifiers (also listed for Series 1000 in some refurbisher materials). It is mounted on the condensate line ahead of the humidifier and, by responding to the sensed temperature, provides a pneumatic switch signal to regulate humidification and help prevent the humidifier from spitting water during warm-up. The switch accommodates two pneumatic-control ranges, with replacements available for 2–9 psi (D126007) or 10–60 psi (D126008) to suit the operating steam pressure in the system. It weighs about 0.25 lb and is designed to operate with standard plant steam or steam generated from deionized or RO water, offering compatibility across common steam-generation sources. A cross-reference exists to older Armstrong parts (A5503, B6056, B6057) for compatibility in legacy installations, and the B7131 requires no stainless steel thermal well. When specified as an option for Armstrong humidifiers, the B7131 serves as the pneumatic counterpart to maintain temperature-triggered control even if the main steam supply is interrupted, aligning with Armstrong’s guidance for Series 9000 installations.