Metrohm NIRS XDS Process Analyzer – DirectLight/NonContact - Manual (Page 23)

▪▪▪▪▪▪▪ 21
contains a pressure control valve, surrounded by a spark arrestor.
EPCU
Electronic Power Control Unit. This is the round green housing with Display/ Interface LED panel in
the face.
HEP
High Enclosure Pressure. When activated, the Rapid Exchange Solenoid Valve is disabled and the
alarm relay is energized.
IEC
International Electrotechnical Commission. The IEC issues international standards for all areas of
electrical, electronic and related technologies.
ISA
Instrument Society of America. ISA is an industry organization representing the interests of quality,
safety, and productivity of measurement and control systems and equipment. ISA standards cover
these important subjects: symbols and diagrams, specification sheets, electrical safety in hazardous
locations, fieldbus, control valve dimensions and tests, environmental conditions for M&C systems,
fossil fuel power plant controls, and much more.
NFPA
National Fire Protection Association. The mission of the international nonprofit NFPA is to reduce the
worldwide burden of fire and other hazards on the quality of life by providing and advocating
scientifically-based consensus codes and standards, research, training, and education.
PSB
Power Shutdown Bypass input. This feature, if supplied, permits access to instrument adjustments
without use of the pressure control sequence. This is for adjustment only, not for operational use.
Rapid Exchange Control Valve Stem
This is a manual adjustment on the front panel, to permit air entry into the system.
Rapid Exchange Solenoid Valve
This is an Intrinsically safe valve used to control incoming air.
RET
Rapid Exchange Timer. This provides a short delay after Rapid Exchange Pressure and flow are
detected, to accomplish multiple volume exchanges before the enclosure power relays are energized.
SDT
Shutdown Delay Timer. When initiated by loss of safe pressure, the power relays are latched and the
Power Shutdown Delay LED illuminates. Upon time out, the power relays de-energize unless a safe
pressure is restored or PSB input is activated (Passive Access™).
SEP
Safe Enclosure Pressure. When activated, normal operation is enabled. Upon deactivation, enclosure
power relays are de-energized or latched by SDT (Shutdown Delay Timer) function and alarm relay is
de-energized.