Modified air filter cum regulator combination unit model FRSM- 4 of SIEMAG make with metallic bowl sintered bronze filter element, metallic handle, manual drain and with following ( 1 ) Pressure drop of 0. 1 kg/ cm2 to 0. 2 kg/ cm2. ( 2 ) Thermo plastic piston ( diaphragm ). [ 3 ] Rounded brass plunger. [ 4 ] Pressure guage with red marking at 2. 5 kg/ cm2 & 3. 5 kg/ cm2 band of green colour between 2. 5 kg/ cm2 to 3. 5 kg/ cm2 without connector size 1/ 2