We pump 33% ammonia solution along a single pipe line before we introduce it to the mix. We've had two occasions now where the ammonia pressure has rapidly risen in the pipe. It happens when the fluid is at rest, meaning all valve shut and no pumps running. The pressure just escalates. The pipe was rinsed with recycled water, but this is a weak solution of what the ammonia is mixed with anyway.
Is there any material/condition that the ammonia solution could react with to cause this sudden over pressure?
- The ammonia tanks are outside (+1–2 degrees Celsius).
- The internal temperature is (+15–19 degrees Celsius).
- There is no pressure release system.
- The system is 8yrs old.