Direct fired heater with improved set-up features

Abstract

Features of the direct fired heater can facilitate and improve setup and operation thereof. The direct fired heater can include a housing forming an airflow passage and the airflow passage having an inlet and an outlet; an air moving device to flow air from the inlet to the outlet; gas fired burner disposed in the housing; a pivotal airflow damper disposed in the housing relative to the gas fired burner to control the air flow rate through the burner; and an adjusting device for adjusting the damper from outside the airflow passage. Sensing probes disposed in the airflow passage upstream and downstream of the burner and a pressure differential measuring instrument, such as a manometer, disposed outside of airflow passage in communication with the upstream sensing probe and the downstream sensing probe can measure the differential pressure upstream and downstream of the burner. A shut-off switch also in communication with the sensing probes controls a valve that can interrupt gas flow to the burner when the pressure differential between the upstream and downstream sensing probe is out of a predetermined pressure differential range.

1 . A direct fired heater comprising a housing forming an airflow passage and said airflow passage having an inlet and an outlet, an air moving device to flow air from said inlet to said outlet, a gas fired burner operatively associated with the housing, a pivotal airflow damper disposed in said housing relative to said gas fired burner to control the air flow rate through said burner, and an adjusting device to adjust said damper from outside said airflow passage.  
   
   
       2 . The direct fired heater in  claim 1  wherein said pivotal damper is adjacent to said gas fired burner in said airflow passage.  
   
   
       3 . The direct fired heater in  claim 1  wherein said pivotal damper pivots about an axis transverse relative to the longitudinal axis of said airflow passage.  
   
   
       4 . The direct fired heater in  claim 1  wherein said housing has a mixing chamber downstream from said burner for mixing partially combusted air from said burner and uncombusted air that passes through said damper to provide tempered air.  
   
   
       5 . The direct fired heater in  claim 1  wherein said pivotal damper has a pivotal shaft having an end portion residing outside of said airflow passage.  
   
   
       6 . The direct fired heater in  claim 5  wherein said adjusting device comprises an adjustable arm on said end portion to rotate said shaft and by which the damper is pivoted, and a locking means to maintain the adjusted position of said adjustable arm.  
   
   
       7 . A direct fired heater comprising a housing forming an airflow passage and said airflow passage having an inlet and an outlet, an air moving device to flow air from said inlet to said outlet, a gas fired burner disposed in said housing, an airflow damper disposed in said housing relative to said gas fired burner to control the air flow rate through said burner, an upstream sensing probe disposed in said airflow passage upstream of said burner and said damper, a downstream sensing probe disposed in said airflow passage downstream of said burner and said damper, a pressure differential measuring instrument disposed outside of said airflow passage in communication with said upstream sensing probe and said downstream sensing probe, and an adjusting device to adjust said damper in response to said pressure differential measuring instrument.  
   
   
       8 . The direct fired heater in  claim 7  wherein said upstream sensing probe is a static tube or pitot tube.  
   
   
       9 . The direct fired heater in  claim 7  wherein said downstream sensing probe is a static tube or pitot tube.  
   
   
       10 . The direct fired heater in  claim 7  wherein said pressure differential measuring instrument is a fluid containing differential manometer comprising a U shaped conduit having a first tubular arm in communication with said downstream sensing probe, a second tubular arm in communication with said upstream sensing probe, a first fluid level in said first arm, and a second fluid level in said second arm.  
   
   
       11 . The direct fired heater in  claim 10  further comprising a visual indicia disposed outside of said airflow passage for viewing in conjunction with said first fluid level and said second fluid level of said differential manometer so that said first and second fluid levels can be adjusted during operational set up of said direct fired heater.  
   
   
       12 . The direct fired heater in  claim 7  wherein said damper pivots about an axis transverse relative to the longitudinal axis of said airflow passage.  
   
   
       13 . The direct fired heater in  claim 12  wherein said damper has a rotatable shaft having an end portion residing outside of said airflow passage.  
   
   
       14 . The direct fired heater in  claim 13  wherein said adjusting device said damper comprises an adjustable arm on said end portion to rotate said shaft and by which the damper is rotated; and a locking means to maintain the adjusted position of said adjustable arm.  
   
   
       15 . The direct fired heater in  claim 7  wherein said housing has a mixing chamber downstream from said burner and damper for mixing partially combusted air from said burner and uncombusted air that passes through said damper to provide tempered air.  
   
   
       16 . The direct fired heater in  claim 7  further comprising a supply line for supplying gas to said gas fired burner and having a valve to control the gas supply to said gas fired burner, and a shut-off switch in communication with said upstream sensing probe and said downstream sensing probe wherein said switch controls said valve to interrupt gas flow to said burner when a pressure differential between said upstream and downstream sensing probe is out of a predetermined pressure differential range.  
   
   
       17 . A direct fired heater comprising a housing forming an airflow passage and said airflow passage having an inlet and outlet, an airflow passage disposed in said housing and having an inlet and an outlet, an air moving device to flow air from said inlet to said outlet, a gas fired burner disposed in said housing, an airflow damper disposed in said housing relative to said gas fired burner to control the air flow rate through said burner, an upstream sensing tube disposed in said airflow passage upstream of said burner and damper, a downstream sensing tube disposed in said airflow passage downstream of said burner and damper, a fluid containing differential manometer comprising a U shaped conduit having a first tubular arm in communication with said downstream sensing tube, a second tubular arm in communication with said upstream sensing tube, a first fluid level in said first arm, and a second fluid level in said second arm, a visual indicia disposed outside said airflow passage for viewing in conjunction with said first fluid level and said second fluid level of said differential manometer, an adjusting device to adjust said damper in response to said differential manometer, a supply line for supplying gas to said gas fired burner and having a valve to control the gas supply to said gas fired burner, and a shut-off switch in communication with said upstream tube and said downstream tube wherein said switch controls said valve to interrupt gas flow to said burner when a pressure differential between said upstream and downstream sensing tubes is out of a predetermined pressure differential range.  
   
   
       18 . Method for controlling a direct fired heater where air is drawn through a passage in a housing and a portion of the air is combusted by a burner comprising sensing pressure upstream and downstream from an airflow damper, and adjusting said damper from outside of said passage until the measured pressure differential upstream and downstream of said damper falls into a predetermined range.  
   
   
       19 . The directed fired heater of  claim 5  wherein said end portion resides between an interior wall of said housing defining said airflow passage and an exterior wall of said housing, said exterior wall having an access to said end portion.