INSTRUMENTATION AND ELECTRICAL SERVICES 59A?23
2001 Edition
other. Thealarm shall be set so that the operator has sufficienttime to stop the flow without exceeding the maximum permittedfilling height and shall be located so that it isaudible to
personnel controlling the filling. The high-liquid-levelflow
cutoff device required in 7.1.1.3 shall not be consideredas a
substitute for the alarm.
7.1.1.3 The LNG containershall be equipped with a high-liquid-
level flow cutoffdevice, which shall be separate from all
gauges.
7.1.2 Tanksfor Refrigerants or Flammable Process Fluids.
7.1.2.1 Each storage tankshall be equipped with a liquid level
gauging device. Ifit is possible to overfill the tank, a high-liquidlevelalarm shall be provided in accordance with 7.1.1.2.
7.1.2.2 Therequirements of 7.1.1.3 shall also apply to installations
of flammablerefrigerants.
7.2 Pressure Gauge. Each container shall be equipped witha
pressure gauge connected to the container at a pointabove
the maximum intended liquid level.
7.3 Vacuum Gauge. Vacuum-jacketed equipment shall be
equipped with instruments or connections forchecking the
absolute pressure in the annular space.
7.4 TemperatureIndicators. Temperature-monitoring devices
shall be provided in field-erectedcontainers to assist in controlling
temperatures when placing the containerinto service or as
a method of checking and calibratingliquid level gauges.
7.4.1 Vaporizers. Vaporizers shall be provided withindicators
to monitor inlet and outlet temperatures of LNG, vaporizedgas, and heating-medium fluids to ensure effectiveness of
theheat transfer surface.
7.4.2 Heated Foundations of Cryogenic Containers andEquipment. Temperature-monitoring systems shall be provided
where foundations supportingcryogenic containers and
equipment could be affected adversely by freezingor frost
heaving of the ground.
7.5 Emergency Shutdown. Instrumentationfor liquefaction,
storage, and vaporization facilities shall be designed sothat, in
the event that power or instrument air failureoccurs, the system
will proceed to a failsafe condition thatis maintained
until the operators can take appropriate action eitherto reactivate
or to secure the system.
7.6 Electrical Equipment.7.6.1 Electrical equipment and wiring shall be of the typespecified
by and shall be installed in accordance with NFPA70,
National Electrical Code?, or CSA C 22.1,Canadian Electrical Code,
for hazardous locations.
7.6.2 Fixed electrical equipmentand wiring installed within
the classified areas specified in Table7.6.2 shall comply with
Table 7.6.2 and Figures 7.6.2(a)through 7.6.2(d) and shall be
installed in accordance withNFPA 70, National Electrical Code,
for hazardous locations.
FIGURE 7.6.2(a) Extent of classified area around containers.
FIGURE 7.6.2(b)Dike height less than distance from container
to dike (H less than x).
FIGURE 7.6.2(c) Dike height lessthan distance from container
to dike (H greater thanx).
FIGURE 7.6.2(d) Container with liquid level below gradeor
top of dike.
?
Sphere having radius
of 15ft (4.6 m)?ivision 2
Horizontal
equator of
sphereGrade level
Cylindrical volume?
Division 2 [includes
bottom halfof 15-ft
(4.6-m) radius sphere]
Sphere havingradius of 5 ft
(1.5 m)?ivision 1
Pointof connection
or source of
excessive release
of liquid orgas
H
x
Belowgrade pit or trench
Area within 5ft (1.5 m)
of relief valve
Container
15 ft(4.5 m)
x
H
Division 1
Division 2
Areawithin 5 ft (1.5 m)
of relief valve
Hx
15 ft (4.5 m)
Container
Division 1
Division2
Area within 5 ft (1.5 m)
of reliefvalve
Container
Dike
15 ft (4.5 m)
Grade
Division1
Division 2
