Often there is a requirement to have the liquid nitrogen supply pressure reduced as well as removing the gas from the liquid stream.

A pressure dropping phase separator achieves this by reducing the pressure through a pressure-reducing valve. When a high-pressure liquid is flashed down to the lower (usable) pressure, quantities of gas are evolved (see graph below), which in turn will give a poor quality, low-pressure liquid supply. To overcome this, a large orifice float valve is installed in the phase separator to vent the larger than normal gas quantities.

Other features of the system are a small ¼" economiser pressure control valve that will keep the vessel and any downstream pipe work at the low working pressure (typically 0.5 bar above the working pressure). Along with this, there is a ⁷⁄₁₆" relief valve set at a higher pressure. This valve gives additional protection to the system (through higher discharge rate) if the pressure rises rapidly due to unforeseen events.

Typical applications:

• Decanting quantities of liquid from high-pressure storage tanks primarily used for gas supply applications.
• Reducing pressure from the main feed line to supply pressure sensitive equipment (for example semiconductor testing machines).