TM 5-3895-374-24-2 exchanger.  The front plate must be protected from heat using high temperature refractory on firebox side (as applicable). To  install  the  burner,  a  circular  opening  must  be  cut  in  the  steel front  plate.    Four  (4)  mounting  bolts  must  be  installed  at  proper locations   to   match   the   mounting   holes   provided   on   the   burner mounting flange.  (See dimensional drawings, page 5.) The burner mounting flange must be securely attached to the front plate with suitable gasket or non-asbestos, high temperature rope packing to prevent   any   products   of   combustion   from   escaping   from   the combustion chamber.  The burner assembly  should  be  supported at  the  base  of  the  housing  to  prevent  undue  strain  on  the  front plate.  (A mounting pedestal is furnished for this purpose.) Type C burners are furnished with a lifting lug for ease of handling and mounting. Combustion Chamber - General Combustion   chambers   shall   be   provided   as   recommended   in “Chamber  Dimension  Charts,”  and  should  be  constructed  of  high temperature refractories, in the form of firebrick or rammed plastic refractory,  backed  by  suitable  heat  insulating  material.  Certain types of heat exchangers, such as warm air furnaces, some hot oil heaters, wet base steel and cast iron packaged firebox boilers and Scotch  marine  boilers,  use  the  combustion  chamber  to  transfer heat, and therefore do not require refractory or other insulation.  If in doubt, consult the heat exchanger equipment manufacturer. Where boilers are of the mud-leg type, refractory should extend 6” to 8” above the bottom of mud-leg. All possible points of air infiltration or ex-filtration must be sealed. If   the   unit   is   to   be   fired   under   positive   combustion   chamber conditions, extreme care must be taken to ensure that a 100% seal is maintained.  The Type C burner is designed to provide all the air required for complete and efficient combustion.  Entry or loss of air from  sources  other  than  the  firing  unit  will  decrease  its  overall combustion  and  operational  efficiency.    See  page  12,  Figs.    13 through 16 and Table 7 for additional information. Figure 13 Conventional Firebox Boiler Figure 14 Figure 15 Typical Firedoor Installation - Cast Iron Boiler Packaged Firebox Boiler Figure 16 Scotch Marine Boilers Scotch Marine Boiler Minimum Furnace Tube Inside Dimensions BHP  Min Inside Dimension BHP  Min Inside Dimension BHP  Min Inside Dimension 20 14” 80 20” 200 28” 30 16” 100 22” 250 34” 40 16 125 22” 300 34” 60 19 150 - 24”. 350 38” Note: The  above  minimum  dimensions  are  recommended.    If  boiler  dimensions  are  less,  consult  with factory.    All  burners  set  through  refractory  with  sleeve  to  allow  field  removal.    Unlined  space between sleeve and burner blast tube closed with non-asbestos high temp rope or KA-O-Wool. (page 3 - 964)