Boiler Maintenance Flashcards
if a boiler tube cannot be removed immediately because of its location in the boiler, and a decision is made to plug the tube, what must be done to the tube after plugging?
puncture the tube to prevent an increase in pressure and the possibility of blowing the plug out of the tube
when laying firebrick with mortar in place, what is the proper procedure for dipping the bricks in mortar?
dip one end of the brick into the mortar, and then with a wiping motion, dip the bottom of the brick
once the mortared firebrick is laid into position, how is it tapped in place?
tap it firmly, both sidewise and backwards, so that it will be forced into position
what is the required size of mortared joints when installing firebrick?
1/16 inch
what type of burner front cracks are caused by stresses resulting from normal expansion and contraction?
radial cracks
what type of burner front cracks eventually results in extensive damage and run approximately parallel to the surface of the Bruner front?
parallel cracks
what is the probable cause of a cartable burner front breaking up after very little use?
too much water was used in mixing the material during installation
the loss of firebrick through cracking and subsequent breaking or crumbling is called what?
spalling
what are the two main causes of refractory deterioration ?
spalling and slagging
what forms slag?
ash and other unburnable materials such as seawater solids that react with brick work?
lowering boiler furnace temperature too rapidly will likely cause what damage to firebrick?
deep fractures
raising the boiler furnace temperature too rapidly will likely cause what damage to firebrick?
firebrick will break at the anchor bolts
what is installed to provide space for the refractories to expand without putting pressure on the linings?
expansion joints
castable should not be mixed until all preparations have been made fro installing the burner front, since the material begins to set at once and must be discarded if it is not used within what time frame?
30 minutes
when using plastic fireclay for burner cone insulation, the plastic is vented at what intervals?
every 2 inches centerline
what is sued to vent plastic fireclay burner fronts?
A 3/16 inch rod tapered to blunt point in the last half inch
when compared to insulating block, firebrick has an insulating value of what?
less than 1/10th that of insulation block
what is the FC-25 fiber fax tamping tax used for?
to repair cracks in deteriorated or failed refractory
anchors used for castable or plastic refractory shall be what type?
pennant type
when working in large areas the refractory anchors should be spaced at what intervals?
every 10 to 12 inches
what is the maximum gap between two sidewall tubes in a D type boiler?
1/4 inch
what is the corrective action for a gap exceeding 1/4 inch on two sidewall tubes?
fill the gap with ceramic fiber or ceramic fiber rope
castable refractory shall be air-cured for how long?
two days or more
lighting fires in boiler with newly installed castable refractory after an air-cure of oil one day is prohibited without approval from whom ?
NAVSEA