A process normally contains no HHCs, but under upset conditions, the process
could generate an HHC in an amount in excess of the TQ. Is the process covered?
Processes are covered by the Rule only if, at any time under normal processing
circumstances, they contain an HHC in excess of its TQ. The ability to generate an HHC
during an upset condition does not invoke coverage by the PSM Rule. However, when
DOE contractors recognize situations with significant potential for safety and health
impacts, they should consider applying appropriate PSM practices to protect worker
health and safety.
An Appendix A chemical is created within and then immediately consumed in a
process. Does the brief existence of this short-term intermediate chemical cause this
process to be covered by the Rule? If the inventory of this intermediate can only
exceed the TQ under upset conditions, is it a covered process?
A process is covered if, at any time in one location, it contains an HHC in excess of its
TQ. This process is covered as long as the intermediate existed under normal conditions
in the process. If the intermediate chemical could exist above the TQ only under upset
conditions, then the process is not covered. However, when DOE contractors recognize
situations with significant potential for safety and health impacts, they should consider
applying appropriate PSM practices to protect worker health and safety.
Please clarify the exemptions for the following types of operations covered under the
workplace fuel criteria: hazardous waste incinerators, refinery fuel gas systems,
liquefied petroleum gas (LPG) storage for vehicle fueling, natural gas systems for
utility boilers, and natural gas systems used to sweep flare systems.
If the incinerator is used to destroy either a flammable material or another HHC that is
listed in Appendix A, and the process contains a TQ of an HHC, the incinerator is
covered. Generally, fuel gas or natural gas systems are exempt if they are operated only
for fueling process furnaces or utility boilers that are also not covered. However, if fuel
gas or natural gas is used to fuel a covered process, then the fuel gas or natural gas
systems associated with the process are covered. LPG storage and handling systems used
exclusively to fuel vehicles are not covered. A natural gas supply used to "sweep" a flare
system is not covered unless the flare system is covered for other reasons.
Must the boundary of a covered process containing many interconnected vessels
always extend in all directions to the process unit's battery limits?
No. In many cases, DOE contractors may wish to define the physical limits of coverage
based on an evaluation of the threat of a catastrophic release of an HHC. Contractors are
encouraged to document the technical basis of their coverage decision for those cases
subject to interpretation.
A continuous process uses an HHC, but the HHC inventory exceeds the TQ in only
one vessel. Upstream of this vessel, except for the HHC supply system, there are no
HHCs. Because the HHC is consumed almost entirely in the vessel, normally only
trace amounts of the HHC exist downstream of this vessel. Is this process covered,
and if so, how far upstream and downstream do the covered process boundaries