looking now to fig1 the furnace 10 of a steam generator is shown in which burners 12 are provided for burning coal therein . the walls of the furnace are lined with water - cooled tubes 14 , and in the upper portion of the furnace is located pendant superheaters 16 . during regularly scheduled maintenance shutdowns , it sometimes is necessary for workmen to gain access to the upper portion of the furnace , for example to remove slag from the superheater panels . as shown in fig1 - 4 , there are a plurality of openings 18 along each side 19 of the furnace 10 , at about the height of the nose arch 20 , just beneath the superheaters 16 . these openings would be covered by removable doors during normal operation of the boiler . during a maintenance shutdown , the doors are removed so that the platform framework can be placed in the furnace and assembled . as shown in fig2 a plurality of beams 22 can be moved into and out of the furnace by means of upper and lower rollers 24 and 26 ( fig5 ), the lower rollers 26 being power driven . these beams 22 , when fully extended into the furnace , reach to a point close to the center of the furnace ( fig3 ), and form the major portion of the maintenance platform framework . as seen in fig5 the beams 22 closest to the furnace front wall 25 have attached thereto a handrail 28 and a grate 30 . these are the only beams containing this added equipment . this enables a workman to initially get out onto this beam to assemble the rest of the platform in relative safety . there are a pair of doorways 32 ( fig2 - 4 ) in the front wall of the furnace , which doorways are aligned with the end of beams 22 when they are fully extended into the furnace . these openings permit a locking beam 34 to be inserted into the furnace , which beam slides between the rolls 36 and 38 ( fig6 ), thus supporting and stabilizing the end of beam 22 . once the beam 34 has been properly positioned relative to rolls 36 and 38 , a pin 40 is placed in opening 42 , locking it to channel member 44 . the turnbuckle members 46 and 48 can also be pinned to the channel member 44 , and the turnbuckles can then be tightened to firmly hold beam 34 in place . at this point in time , a workman can enter the furnace along the beam 22 located next to the front wall . a plank or two can be placed between this beam 22 and the next adjacent beam 22 , so that the worker can move out onto this next beam . the workmen can attach cable 50 to the lug 52 which is welded to the end of beam 22 ( fig7 ). turnbuckle 54 can then be adjusted to level the beam 22 . the cables 50 , there being one for the end of each of beams 22 other than the beams adjacent the front wall , can be dropped into the furnace prior to the workmen entering therein . these cables are attached at their upper ends to support steel 55 ( fig1 ), and extend through sleeves 56 , which are anchored in the doghouse 58 of the furnace 10 above the furnace roof tubes 60 . once the cable is properly attached to the end of the first beam 22 , the workmen can place a couple of more planks over to the next beam and repeat the procedure . this can be repeated as often as necessary until the ends of all of the beams 22 on both halves of the furnace are supported by cables . the workmen can then place the structural tubing members 62 ( fig3 ) between the ends of each beam 22 , and bolt them to each beam . the purpose of these structural tubing members 62 is twofold . first , they tie the ends of all of the beams 22 together , giving the framework added rigidity and preventing relative lateral movement of these beam ends . secondly , they form a ledge , which coacts with a complementary ledge 64 on planks 66 ( fig7 ), preventing these planks from slipping off of the ends of the beams 22 . after the tubing members 62 have been secured in place , the only thing left to do is to place the planks 66 and 68 in position ( fig7 and 8 ). planks 68 have ledges 70 attached to them which coact with the edges of the beams 22 to lock them in place , preventing them from slipping out of the framework . after placement of the planks 66 and 68 , any number of workers can safely enter the upper furnace area to accomplish whatever maintenance work is necessary . when this is accomplished , the temporary platform can be quickly disassembled , the doors can again be secured to the openings 18 and 32 in the furnace , and the unit can be placed back into operation .