Palladium Alloy Hydrogen Purifiers (PAHP's) are among the class of devices that require considerable operator sophistication for safe operation, both with respect to obvious hazards in handling hydrogen and to less obvious requirements for maintaining the integrity of the palladium alloy barrier and thus the purity of the process stream.
DSPS Protection Systems are designed to respond appropriately to emergency situations, such as power loss, and to assist the operator to start up and shut down a PAHP under normal operating conditions.
DSPS units are mounted externally to PAHP's and replace the external networks recommended in PAHP instruction manuals.
A primary rule for the reliable operation of a PAHP is to never have hydrogen present below 600°F.
By the proper choice of normally open and normally closed valves, the DSPS shuts off the feed hydrogen, flushes the crude side with nitrogen and evacuates the pure side whenever power is lost, preventing the PAHP from cooling in hydrogen.
Most power outages are of trivial duration and do not call for complete shut down. Timing circuitry is provided in the DSPS to allow the unit to come back on line whenever the power interruption is less than three minutes. When the power is off longer than three minutes, the feed hydrogen remains off when power returns.
A secondary function of the DSPS is to assist in normal PAHP start-up and shut-down. Whenever the Power Switch is turned On or Off, a 15 minute purge starts. When the unit is turned Off, the purge proceeds as in the case of an emergency shut-down, but is limited to 15 minutes and the evacuated PAHP cools safely to room temperature.