Technical requirements for safety in metal scaffolding – Plane frame scaffolds

5.3.2  Plane frame scaffolds

(a)    This  type of scaffolds  is  commonly  used  for  access  to  ceiling, soffits, walls and columns for carrying out light work, for examples, plastering, painting, conduit installation, cleaning and similar operations. Each scaffold comprises an arrangement of vertical frames and bracings supporting closely boarded working platforms at required levels.

(b)   The design and loading of plane frame scaffolds should be in accordance  with  Section  5.1  of  this  Code.  The  height  of  a vertical frame is normally 1.7m to 2m (depending on the type of the frame used) to give adequate headroom for passage. The height limits of the free-standing plane frame scaffolds and tied plane frame scaffolds should follow professional engineer’s design.

(c)     A plane  frame  scaffold  system  mainly  consists  of  the  following components:

(i)     Ties

–        It  is  essential  for  all  plane  frame  scaffolds  to  be securely      tied   either   to   surrounding   walls,   columns or       such   similar   structures   throughout   the   length and height to prevent the scaffolds from movement, tipping into or away from the wall and structure.

–        The  ties  should  be  located  not  more  than  one  bay from    the   ends   of   the   scaffold   and   thereafter   at intermediate spacing of not more than 3 bays or 7.5m apart, whichever is the lesser. The ties should be as far as practicable be fixed at staggered positions at every two lifts.

–        The     ties     should     be     perpendicular     to     the longitudinal        plane   of   the   scaffold   and   where   it   is not practicable, the deviation from the perpendicular should not exceed 15o. Every tie should be capable of withstanding tensile or compression force applied along the length of the tie.

–       Besides, corner-ties are also necessary to maintain the

stability of plane frame scaffolds. (See Figure 5 for details) (ii)    Bracings

–       Each   plane   frame   scaffold   should   be   effectively

braced   to   restrain   from   lateral   movement.   Cross bracing should be of such length as to square and align vertical members while diagonal bracing should be braced at about 45o  to the horizontal. (See Figure 6 for details)

–        The  scaffolds  should  also  be  braced  horizontally  at intervals of not more than every five lifts. The joints for the bracings should be continuous or lapped. All the brace connections should be made secure.

(iii)   Joints

A joint tube is an internal fitting for joining two standards end to end. A joint tube should be self-centring so that equal length of the tube can be embedded into each of the standards. When uplift may occur, plane frames should be locked together vertically by pins/bolts & nuts. (See Figure 7 for details)

(iv)   Flip locks

Flip locks should be installed at upright position so as to prevent the cross bracing from detaching out of the standards. (See Figure 6)

(v)    Base plates

Legs of the plane frame scaffold should be set on adjustable base plates or plain bases on foundations adequate to support the maximum designed vertical and horizontal loads. The erected scaffold should be plumbed and levelled. (See Figure 6)

(vi)   Fork-heads

A  fork-head  is  a  U-shaped  assembly  at  the  top  of  a standard  for  bearers  of  formwork  to  rest  on.  Fork-heads should  not  be  used   as   base   plates   in   supporting   the scaffold.

(vii)  Castors

A  castor  is  a  swiveling  wheel  secured  to  the  base  of  a vertical member for the purpose of mobilizing the scaffold. All scaffold castors should be designed for strength and dimension to support the designed working load. Castors should be provided with a positive wheel and swivel lock, or equivalent means, to prevent movement and rotation while the scaffold is in place. Castor stems should be secured in the scaffold to prevent them from accidentally falling out at any time.

(d)    Safety  requirements  relating  to  the  boards  or  planks  forming  a working  platform,   guard-rails   and   toe-boards   of   a   working platform, access to and egress from a scaffold, etc. for prevention of falls are the same as described in Section 5.1.4. (See Figure 8 for details)