Taylor-Wharton LP3 - Manual (Page 12)

Safety Devices
The Laser Pak III features relief devices to prevent over pressurization of the vessel, piping, and vaporizers. A
primary relief valve (SV-1) relieves pressure when it exceeds 500 psig. The valve reseats when pressure
drops below this point. In addition, the primary relief valve is supported by a secondary relief device
consisting of a rupture disc (R-1) that will burst at a pressure of approximately 750 psig. The rupture discs
require replacement in the event a safety valve malfunctions and allows vessel pressure to reach the burst
pressure rating.
A relief valve (SV-3), set to open at 22 psig, is also provided. Closing the isolation valve (V-6) prevents flow
through the relief valve. This feature is useful if it is necessary to transport the Laser Pak III at a reduced
pressure. It also allows liquid to be stored at a low pressure. Cryogenic liquid stored at low pressure is colder
and therefore more dense than liquid stored at higher pressure. Dense liquid maximizes the pressure builder
performance for high flow applications.
R-1
SV-1
SV-3
V-6
Figure 7: Safety circuit highlighted in blue.
(Frame and wiring omitted from view for clarity.)
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