Why Ammonia Cylinders get Freezed during Usage?

Question

When atmosphere temperature is lesser,Freezing of the Ammonia Cylinders is Observed

Answer 1

Ammonia gas becomes a liquid at atmospheric pressure when cooled to -33°C.
When stored under pressure and ambient temperature, it remains a liquid.
When in use, the pressure in the storage cylinder is decreased and the liquid begins to boil at the pressure to which it falls when in use. The temperature also falls due to refrigeration by expansion of the liquid to gas and a frost will form on the cylinder and piping due to water vapour from the air condensing and freezing on the cylinder and piping surfaces.

Answer 2

When you start with a pressurized cylinder of ammonia gas, and then remove some of the gas, you reduce the pressure in the cylinder.

When the pressure drops, the ammonia gas remaining in the cylinder becomes cooler.

At some point, the ammonia gas will cool sufficiently to reduce the temp. of the metal cylinder to below the freezing point of water = 32 Deg F
This should occur at a pressure of about 62.3 psia, or 47.6 psig.

At this point, if there is any humidity in the air, it will condense and freeze on the outside of the cylinder, and will continue to do so until the ammonia gas is all used up.

This freeze up will occur only if you are continuously drawing ammonia from the cylinder. If you stop, the metal will have a chance to warm up and the frost will melt untill you start up again.

Answer 3

When the pressure on any gas is reduced, as by using some of it, the gas self-refrigerates. This is true also of liquids that boil when pressure is relieved. Carbon dioxide, for instance, refrigerates down to around 110 below zero Fahrenheit when pressure is relieved.