Water system loop passivation

Dear Sir,

Wht is the frequency,Temperature limit and time for passivation of water for injection distribution loop and purified water system distibution loop.

There is a nice baseline guide from ISPE on water systems. It has all your needs spelled out. As far as your questions go…it depends. Passivation is done to create an ionic barrier at the contact point of the stainless steel piping. Some systems have clamped in piping that can be removed to test the passive nature of the piping. Based on these tests the piping can be scheduled to be passivated again. Scientifically, I don’t know the duration that stainless steel loses is passive nature. If it is bioburden that you are worried about, I think it depends on the temperature of your loops. Hot loops, <80 C typically do not have a bioburden issue. Typically, loops that run at less than 80C are heat sanitized daily at <80C. I like to dump the cold loop, and then heat sanitize because it allows the loop to reach the target temperature quickly. You also need to make sure that your TOC meters are either disconnected or have an adequate cooling supply to cool the water to them, they typically don’t fare well with hot water. I try to heat sanitize loops for about hour, again not scientific, but you can look at one year worth of data to determine if more or less time is justified.

Dear All
Water and steam systems in the Pharmaceutical industry are normally fabricated of stainless steel, typically 316/316L grade. Operating temperatures vary from ambient to high temperature for many USP Purified water systems, for most WFI systems 80° C to 85° C and for pure steam generators and distribution piping, as high as 155° C, as a result the majority, of these systems develop surface deposits or staining corrosions known in the industry as Rouge. Low pH of single pass RO or deionised feed water, aggressive cleaning and passivation chemicals may etch the stainless steel surface. It may also be typically due to chlorides. Some drug manuufacturers are concerned about particulate matter contamination of their products, and routinely clean and re-passivate their systems, at a considerable cost and downtime. So the present concern relates to rouge (corrosion) free pharmaceutical Water for Injection (WFI) systems supply. Rouge is prevented by using a controlled atmosphere which does not contain carbon dioxide. Preferably, this controlled atmosphere is a mixture of about 80% nitrogen and about 20% oxygen. Rouge removal and passivating agents are recommended like Phosphoric acid, citric acid, oxalic acid and ammonium citrate etc etc.

Shahid Ali
QA Manager
APF SC, Ethiopia