Pure Steam Distribution Systems:
The piping should be of inert nature.Pipe material should be SS 304, 316, or 316L grade stainless steel with a mill finish or 180-grit mechanically polished pipe. Passivation post Orbital welding and installation should be conducted. Piping should be designed to facilitate thermal expansion. The distribution header should be able to handle maximum velocity of 7,200 feet per minute.There are few issues which need to be considered when designing a steam distribution systems. This includes the following:
Water Vapor in Steam:
Water vapor are present in steam as a result of heat loss which leads to the change in the liquid to vapor ratio. This moisture can be dried if steam pressure is reduced to achieve temperature of saturation. Further reduction is achieved through installation of separators at Point of used previous and after the regulator
Condensate is formed in the steam systems due to heat losses and natural separation effects. So the piping network should be designed in a manner that eliminates the possibility of condensate formation. Now the question comes what is it that makes the condensate formation unacceptable. The condensate formation accumulation in the piping lowers down the temperature in the network, which is an excellent condition for the microbial proliferation. This condensate presence in the network leads to heavy hammering due to steam and liquid interactions. The condensate develops especially when the POU is not in use, so if this condensate if allowed to stand for a longer period, will lead to microbial growth followed by proliferation of contamination in the entire distribution system.
In order to combat the above identified issues following actions must be followed:
- The piping should be adequately supported so that accumulation of condensate does not happen as a result of sagging.
- Sanitary type steam traps installation at point of use as well as in between the point of use and before a control valve or regulator.
- The distribution header should be designed at lower level than the user points, therefore allowing complete drainage of condensate.
- As a proactive action to control condensate accumulation at POU, a temperature sensor interlocked with the an arrangement of pneumatic valve to drain the condensate must be applied at each point of use. The moment condensate accumulation takes place, it will lower down the temperature, which shall be sensed by the PT-100 and signal to open the drain shall be sent through the solenoid valves to the pneumatic valve.
Removal of NCGs Non-Condensable Gasses):
The term non-condensable gasses is applied to the presence of air and other gasses in pharmaceutical steam systems. It is very critical to remove these non-condensable as these act as hurdle to effective heat transfer leading to inefficient sterilization and excess water accumulation. The non-condensable gasses are removed by pre-heating the water above 80 degrees centigrade and venting the gasses before letting that water enter the pure steam generation system. Also installation thermostatic pharmaceutical steam traps may further remove the non-condensable gasses.