Closed drain header systems

Closed Drain Header Systems for Flammable Liquids... 

Usually, the closed liquid drain header is run as a separate line to the drum and provided with a high level cut-off valve with local manual reset. In some cases the closed drain system is segregated into a number of subheaders, as described earlier. Hydrocarbon liquids may be bypassed around the drum through a connection from the closed drain header directly to the pumpout pump suction, provided that the liquid can be routed to a safe disposal location, considering its vapor pressure and temperature. Emergency liquid pulldown connections, if provided, are routed to the blowdown drum via the closed drain header. 

The shutter section of each beam port is drained to a common drain header. The header drains to the hold tank floor drain through a valve located in the pit beside the demineralizer. This valve is kept closed for Ar-41 control. The vent line from each beam port goes through a check valve and stop valve with bypass flow control and then to the BP TC vent system. Provision is made for leak checking of the beam ports to assure an air-tight seal. 

Isolation valves in the purification system inlet and outlet lines are provided for maintenance purposes. The valves also allow drainage of the HTS coolant to just above the elevation of the headers without the need to drain the purification system. These valves close automatically in the event of LOCA. 

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