Advanced Photon Source

An Office of Science National User Facility

Lesson Module A-18: Liquid Nitrogen Distribution System


This lesson module is intended to familiarize UES personnel with background information and operation of the Liquid Nitrogen Distribution System (LNDS).

The Building and Site Service Coordination (BSC)/Conventional Facilities Group (CFG) monitors the LNDS, but the UES group, with their wider shift coverage, can be asked to act on a problem with the system.

This module will briefly cover information presented in the Liquid Nitrogen Distribution System tutorial, but it is highly recommended that the tutorial be read in its entirety.

The LNDS has been installed at the APS to limit the need for periodic changing of liquid nitrogen dewars that supply liquid nitrogen to the cryo-pumps which function to cool the crystals of beamline monochromators. This system consists of four modules (A through D). Piping is marked to indicate that the line contains liquid nitrogen. The system is operated at approximately 40-psi pressure and is always kept full under normal operating conditions. The lines are kept full via mechanical float keep full valves (one on either side of each module) that vent boil off gas thus keeping liquid in the line. As a back up, electrical keep full valves are adjacent to the mechanical valves. The lines are vacuum jacketed for insulation purposes and do not show evidence of the cryogenic liquid inside. Each system starts in the open gas yards of the 400 area. Namely areas between 431/432, 433/434, 435/436, & 438. The transfer line starts at the 3000 gallon liquid nitrogen dewar.


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