law: Factories Act, 1948 
  21. Fencing of machinery 
  (1) In every factory the following, namely:
  ( i ) every moving
  
  part of a prime mover and every flywheel connected to a prime mover, whether
  
  the prime mover or flywheel is in the engine house or not;
  (ii) the headrace and tailrace of every
  
  water-wheel and water turbine;
  (iii) any part of a stock-bar which projects
  
  beyond the head stock of a lathe; and
  (iv) unless they are in such position or of
  
  such construction as to be safe to every person employed in the factory as they
  
  would be if they were securely fenced, the following, namely,- 
  (a) every part of an
  
  electric generator, a motor or rotary convector;
  (b) every part of
  
  transmission machinery; and
  (c) every dangerous
  
  part of any other machinery;
  shall be securely fenced by safeguards of substantial
  
  construction which 40[shall be constantly maintained and kept in
  
  position] while the parts of machinery they are fencing are in motion or in
  
  use:
   41  [PROVIDED that for the purpose of determining
  
  whether any part of machinery is in such position or is of such construction as
  
  to be safe as aforesaid, account shall not be taken of any occasion when- 
  ( i ) it is necessary to make an
  
  examination of any part of the machinery aforesaid while it is in motion or, as
  
  a result of such examination, to carry out lubrication or other adjusting
  
  operation while the machinery is in motion, being an examination or operation
  
  which it is necessary to be carried out while that part of the machinery is in
  
  motion, or
  (ii) in the case of any part of a transmission machinery used in
  
  such process as may be prescribed (being a process of a continuous nature the
  
  carrying on of which shall be, or is likely to be, substantially interfered
  
  with by the stoppage of that part of the machinery), it is necessary to make an
  
  examination of such part of the machinery while it is in motion or, as a result
  
  of such examination, to carry out any mounting or shipping of belts or
  
  lubrication or other adjusting operation while the machinery is in motion, and
  
  such examination or operation is made or carried out in accordance with the provisions
  
  of sub-section (1) of section 22.]
  (2) The State Government may by rules prescribe such further
  
  precautions as it may consider necessary in respect of any particular machinery
  
  or part thereof, or exempt, subject to such condition as may be prescribed, for
  
  securing the safety of the workers, any particular machinery or part thereof
  
  from the provisions of this section.