ammonia / galvanize pipe

[JimEldridge]

We have @ 30 pressure relief valves connected to a header that leads to a diffuser water tank. The piping and header is galvanized steel pipe .The diffuser tank is stainless steel.We have had some relief valves release causing the galvanize to wash off.Will this weaken the pipe or cause the valves to deteriorate ? What would be the effect on the SS diffuser tank? It is turning white inside. Should we replace the pipe before changing relief valves?
Mechanical Engineers Area

 

[gr2vessels]

Jim,
Please clarify;- the water released from the relief valves has spilled over the pipe, causing the external zinc coating to wash off? Or the water was outside the relief valve and the release was from outside to inside the pipe, causing the internal zinc wash off, ending as white coating in the stainless steel diffuser tank?
It is unusual to replace the relief valves simply for doing their job. The offender in this case seems to be the water which is oxidizing the zinc coating on the pipe and header. It will most likely corrode the pipe and valves if left uncontrolled. I would give the water an appropriate treatment to prevent it from re-offending, thus preventing further deterioration of the pipe and valves.
The white zinc oxide is not likely to affect the stainless steel tank, provided that you stop the zinc corrosion, maintain ambient temperature in the tank and wash the tank periodically to remove those sediments.
gr2vessels

 

[JimEldridge]

Sorry .... I neglected to mention the most important factor. This is an ammonia refrigeration system. the ammonia "washed" off the galvanize. We are changing the pressure reliefs due to a code requirement that they be replaced every 5 years. The pressure reliefs are set at 250#
and I am concerned that the pipe has been weakened. I
have been told that some of the steel comes off when the galvanize washes off.