High Priority: The gap that is recommended to be closed urgently as it is considered
as the “last line of defense” to prevent/ minimize the risk of either releasing hazardous
liquid to ATM, vapor cloud or fire incident. Thus, no Level Switch Low (LSL) to monitor
the condition of outboard seal is considered to the high priority gap.
The high priority gap is also emphasized for pump serving light hydrocarbon which is
identified to process liquid that has vapor pressure at operating temperature higher
than 6 barA* as it will accompany with higher consequence of incident.
* The baseline used by this assessment to identify Light Hydrocarbon is set to the
vapor pressure of LPG at 50%:50% Propane to Butane ratio at 25oC.