TM 1-1500-204-23-9 (f) Maintenance. Consult the applicable    maintenance    manual    for    preventive    and scheduled maintenance requirements. (2) Folding   maintenance   stand,   type   B-4A. The B-4A maintenance stand, shown in figure 9-2, is an adjustable platform and ladder assembly mounted on a caster-equipped    base.        The    maintenance    stand    is hydraulically raised and lowered.  . (a) Purpose.      The   B-4A   maintenance stand has a working height of 3 to 7 feet.  It will support a maximum weight of 500 pounds on the platform. (b) Principles of operation. The maintenance   stand   consists   of   a   main   base   and   a platform surface.  The platform is above and connected to  the  base  by  a  scissors  assembly.    A  hand-operated hydraulic pump is used to transfer fluid from a reservoir to a piston assembly, causing the piston to extend.  The piston  assembly  is  connected  to  the  scissors  and  as  it extends,   causes   the   platform   to   raise.      When   the platform  is  raised  to  the  desired  height,  it  is  manually locked  with  lockpins.    The  platform  is  lowered  to  the down  position  by  manually  opening  a  release  valve  on the  pump,  allowing  the  fluid  to  return  to  the  reservoir and the piston to retract. (c) Safety    practices    and    procedures. The  following  special  precautions  should  be  observed when the using the folding maintenance stand: · Do not stand on the ladder while raising or lowering the platform. · Apply the caster brakes when the stand is in position. · Install the two platform safety pins when the platform is at the desired height. · Leave the platform rails in place unless they interfere with the work area. (d) Operating procedures. The following procedures pertain to the operation of the B-4 folding maintenance stand: 1 Position  the  maintenance  stand  in the desired location. 2 Lock  the  casters  on  all  four  wheels and apply the brakes on the two rear casters. 3 Open  the  vent  plug  and  close  the release valve. 4 Operate   the   hand   pump   until   the platform is at the required height. 5 Install the two safety lockpins. 6 Climb the ladder and do the task. 7 Upon task completion, dismount the stand. 8 Open  the  vent  plug  and  raise  the platform  slightly  to  make  removing  the  safety  lockpins easier. 9 Remove the safety lockpins. 10 Slowly  turn  the  release  valve  lever in a counterclockwise direction until the stand begins to lower. 11 When   the   platform  is   fully   down, close the vent plug and the release valve. (e) Inspection.    The  following  operator inspections   should   be   made   before   using   the   folding maintenance stand. 1 Pump   reservoir.      Check   the   fluid level and service if necessary. 2 Hydraulic hoses. Inspect for security and signs of damage. 3 Actuating cylinder. Look for evidence of leaking. 4 Swivel  casters  and  brakes.    Check for proper operation, adequate lubrication, and broken or chipped wheels. 5 Roller  channels,  ladder  guides,  and scissors pivot points.  Look for cleanliness and adequate lubrication. (f) Maintenance. Consult the applicable    maintenance    manual    for    preventive    and scheduled maintenance requirements. 9-26