Salient Features of Thermo-setting Unit Steam Cascade System in PSF Draw Line
Process Description :
There are eighteen rollers in the Thermo-setting Unit (TSU). Rollers in four heating zones are distributed as follows - - -
• Zone 1 : 4 Rollers
• Zone 2 : 4 Rollers
• Zone 3 : 4 Rollers
• Zone 4 : 6 Rollers
Steam heating is done through rotary joints in each roller. Each zone has one flash tank for steam conversion.
Steam from the boiler, at 23 bar pressure, is first supplied to the rollers of the 4th zone of the TSU through a pressure control valve and a pressure of 16 ~ 18 bar is maintained.
Condensate from the rollers of the 4th zone of TSU goes into the 4th flash tank and steam from this flash tank is supplied to the rollers of the 3rd zone of the TSU through another pressure control valve where 1 bar differential pressure is maintained.
Condensate from the rollers of the 3rd zone of TSU goes into the 3rd flash tank. Condensate from the 3rd and 4th flash tanks goes into the 2nd flash tank.
Steam from the 3rd flash tank in turn is supplied to the rollers of the 2nd zone of the TSU through another pressure control valve where 1 bar differential pressure is maintained.
Condensate from the 2nd flash tank goes into the 1st flash tank. Steam from the 2nd flash tank is supplied to the rollers of the 1st zone of the TSU where a pressure of 4.5 bar is maintained through two sets of pressure control valves in cascade and a part of the steam goes into the 10 bar Steam header for dryer heating (comprising of 4 zones).
Condensate from the 1st flash tank goes to a separate flash tank (supplied by m/s. Forbes Marshall) where condensate from other heating equipment, for e.g., Dip Bath, Draw Bath, Heating Channels, Crimper, etc. also comes.
Flash steam from this flash tank is supplied to a Thermo-compressor (with 23 bar supplied motive steam) for steam conversion and utilization in the 3.0 bar steam supply...